COMPOUNDS FOR USE IN SCREENING METHODS FOR SPINAL MUSCULAR ATROPHY

Info

Publication number: 20160052935
Type: Application
Filed: Nov 10, 2015
Publication Date: Feb 25, 2016
Inventors: Elliot Androphy (Indianapolis, IN), Gregory D. Cuny (Houston, TX), Jonathan Cherry (Carmel, IN), Marcie A. Glicksman (Winchester, MA)
Application Number: 14/936,949

Abstract

Disclosed herein are compositions and methods for treatment of spinal muscular atrophy (SMA). In certain embodiments, compounds are provided that increase full-length survival of motor neuron (SMN) protein production by an SMN2 gene.

Description

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Non-provisional application Ser. No. 13/941,099 filed Jul. 12, 2013, which claims priority to U.S. Provisional Patent Application No. 61/671,425 filed on Jul. 13, 2012, both of which are hereby incorporated by reference in their entireties.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grant numbers HD064850 and NS064349 awarded by the National Institutes of Health. The U.S. Government has certain rights in the invention.

INCORPORATION OF SEQUENCE LISTING

A paper copy of the Sequence Listing and a computer readable form of the sequence containing the file named “31377-18 (IURTC 12111)_ST25.txt”, which is 54,433 bytes in size (as measured in MS-DOS), are provided herein and are herein incorporated by reference. This Sequence Listing consists of SEQ ID NOS: 1-9.

FIELD OF DISCLOSURE

The present disclosure relates to pharmaceutically active compounds useful for treating, or lessening the severity of, spinal muscular atrophy.

BACKGROUND OF DISCLOSURE

Spinal muscular atrophy (SMA) is a neurological disorder that results from loss of function of the anterior horn cells in the spinal cord, manifesting as progressive motor weakness, muscle wasting, and paralysis. SMA is caused by insufficient levels of the survival motor neuron (SMN) protein. The SMN locus on chromosome 5q13 contains two inverted copies of SMN called SMN1 and SMN2. Most cases of SMA harbor homozygous deletions of the SMN1 gene and retain at least one copy of SMN2. With a carrier rate of about 1 in 40, SMA is estimated to be the most frequent genetic cause of infant mortality.

SMN2 is a gene duplication of SMN1 with the same predicted amino acid coding capacity. The nucleotide sequences of SMN1 and SMN2 are nearly identical. A critical difference is a C to T transition at the +6 position in exon 7, which dramatically influences the splicing pattern in these genes. Greater than 90% of SMN1 transcripts include exon 7, while there is less than 15% exon 7 inclusion in SMN2 transcripts. This alternatively spliced product produces a truncated and unstable form of the SMN protein. Any increase in the inclusion of exon 7 in SMN2 transcripts would result in higher levels of full length SMN protein. A treatment that increases the amount of full length SMN2 mRNA should result in increased levels of SMN protein. Based on this premise, an in vivo screen that can detect increases in full-length exon 7 included SMN2 transcripts was developed.

A splicing reporter that fused SMN exons 6, 7, and 8 and their introns in frame with firefly luciferase and was expressed from a CMV promoter in C33a cells has previously been constructed. It was found that this reporter could recapitulate changes in splicing observed with over-expression of the splicing factor Tra2β. This assay was used successfully to identify compounds that increase the amount of full-length transcript produced by the SMN2 gene and SMN protein in fibroblasts isolated from an SMA patient. Another study used a SMN2 promoter based reporter to screen a library of small molecules for ability to increase SMN expression levels in NSC34 cells. This reporter measured only SMN2 specific transcription and lacked any SMN gene sequence.

It has been reported that histone deacetylase (HDAC) inhibitors such as sodium butyrate, trichostatin A (TSA), valproic acid, suberoylanilide hydroxamic acid (SAHA) and LBH589 increase SMN transcription and inclusion of exon 7. For many of these HDACs, relatively high (micromolar or millimolar) concentrations of these compounds are necessary. These activators are non-specific and will alter transcription of many genes so long-term safety has been questioned. However, type I severe SMA is fatal and short-term administration of such compounds may provide limited benefits.

A first generation splicing assay had low signal intensity, high basal expression of SMN-luciferase, and became less responsive with serial cell passage. These cells were determined to be unsuitable for high-throughput screening (HTS). The reporter system was redesigned and a more stable and reproducible assay has now been built that may be used for HTS.

Particularly, described herein is a clonal second generation SMN-luciferase reporter cell line that combines the strengths of both the promoter-based assay and a previous splicing reporter. This assay is much more robust, has lower well-to-well variation, and displays more stable luciferase expression that does not change with serial passage. It also faithfully reproduces the reported activity of an array of drug-like compounds that have been shown to increase SMN expression levels. This reporter can detect changes in SMN2 levels in response to overexpression of splicing factors such as Tra2β. This assay is a vast improvement on the previous generation of reporters and represents a valuable tool for further identification and characterization of compounds that increase expression of full-length SMN protein from the SMN2 gene.

Additionally, there is a need for new drugs to treat spinal muscular atrophy. SMN reporters can be used as tools for identifying and characterizing protein factors and chemical compounds that increase expression of full-length SMN2 transcripts. Results from HTSs to identify novel compounds that increase SMN2 expression using this cell based SMN-luciferase reporter assay are also described herein.

As described herein, the present disclosure provides compounds useful for treating or lessening the severity of spinal muscular atrophy. The present disclosure also provides methods of treating or lessening the severity of spinal muscular atrophy comprising administering to a patient susceptible to or having spinal muscular atrophy a compound or composition of the present disclosure.

BRIEF DESCRIPTION

The present disclosure is generally related to compounds and methods for treatment of spinal muscular atrophy (SMA) utilizing the compounds. In certain embodiments, compounds are provided that increase full-length survival of motor neuron (SMN) protein production by an SMN2 gene.

Accordingly, in one aspect, the present disclosure is directed to a compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L¹is independently a covalent bond or an optionally substituted bivalent C1-6 hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—;
each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:
two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
- each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In another aspect, the present disclosure is directed to a composition comprising a compound and a pharmaceutically acceptable carrier, adjuvant or vehicle. The compound has the formula of formula I:

or a pharmaceutically acceptable salt thereof, wherein

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L¹is independently a covalent bond or an optionally substituted bivalent C1-6 hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—;
each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:
two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In yet another aspect, the present disclosure is directed to a method for increasing the production of full-length SMN protein in a cell having an SMN2 gene. The method comprises contacting the cell with a compound or composition. In some embodiments, the compound has the formula of formula I:

or a pharmaceutically acceptable salt thereof, wherein

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L¹is independently a covalent bond or an optionally substituted bivalent C1-6 hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—;
each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:
two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, a composition is administered, the composition includes the compound described above and a pharmaceutically acceptable carrier, adjuvant or vehicle.

In some embodiments, the full-length SMN protein is produced by upregulation of SMN2 activity. In one embodiment, the upregulation of SMN2 activity includes increased expression of full-length SMN2 transcripts.

In another aspect, the present disclosure is directed to a method of treating a patient susceptible to or having spinal muscular atrophy. The method comprises administering to the patient a therapeutically effective amount of the compound or composition described above.

In another aspect, the present disclosure is directed to a vector. The vector comprises a survival motor neuron (SMN) promoter selected from the group consisting of a survival motor neuron 1 (SMN1) promoter and a survival motor neuron 2 (SMN2) promoter; a transcription start site; a nucleic acid encoding exons 1-8 of the SMN gene and encoding introns 6-8 of the SMN gene; and a reporter gene. In yet another aspect, the present disclosure is directed to a host cell comprising the vector.

In another aspect, the present disclosure is directed to a vector. The vector comprises a survival motor neuron 1 (SMN1) promoter; a transcription start site; a nucleic acid encoding exons 1-8 of the SMN1 gene and encoding introns 6-8 of the SMN1 gene; and a reporter gene. In yet another aspect, the present disclosure is directed to a host cell comprising the vector.

In yet another aspect, the present disclosure is directed to a vector. The vector comprises a survival motor neuron 2 (SMN2) promoter; a transcription start site; a nucleic acid encoding exons 1-8 of the SMN2 gene and encoding introns 6-8 of the SMN2 gene; and a reporter gene. In yet another aspect, the present disclosure is directed to a host cell comprising the vector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D show SMN-reporter mini-genes. FIGS. 1A and 1B illustrate the changes made to the new reporter (see text). The asterisk denotes a restriction site included during cloning that is unique to the SMN reporter gene. These reporters produce a SMN-luciferase fusion protein when exon 7 is included (FIG. 1C) but not when exon 7 is skipped (FIG. 1D). ˜90% of mRNA from the SMN2-reporter mini-gene skips exon 7.

FIGS. 2A-2D show reporter assay validation. FIG. 2A illustrates a comparison of luciferase activity for equivalent numbers of mixed population SMN1-luc, mixed population SMN2-luc, clonal SMN1-luc and clonal SMN2-luc cells. Luciferase activity, scored as relative light units (RLU). FIG. 2B illustrates the detection of SMN-luciferase fusion protein in HEK parent, SMN1-luc, and SMN2-luc reporter cells. Lysates were blotted for the fusion protein with an anti-luciferase antibody and endogenous SMN and compared to actin and tubulin. FIG. 2C illustrates the end point RT-PCR used to compare mRNA species of SMN1-luc and SMN2-luc cells. Primer pairs were designed to amplify both full-length and exon 7 excluded SMN-luciferase mRNA. Percent inclusion was determined by comparing band intensities using QUANTITY ONE software. FIG. 2D illustrates that SMN-luciferase fusion stability was determined by treating cells with 10 μM cycloheximide and measuring luciferase activity at various time points. Data were plotted using PRISM4 (Graphpad Software Inc.) and non-linear regression was used to determine protein half-life.

FIGS. 3A-3E show activity of known compounds in the reporter cells. FIG. 3A depicts results of sodium butyrate, SAHA, TSA, aclarubicin, indoprofen, valproic acid, and tobramycin tested in 6-point dose response experiments. Each compound was tested at concentrations previously reported to increase SMN protein levels. Black square with solid line SMN2-luc cells; gray triangle—SMN1-luc cells; black circle with dotted line—SV40 control. Y-axis represents % activation relative to DMSO control. All points were tested in quadruplicate and plotted as mean±SEM. Curves were created by linear regression using PRISM4 (Graphpad Software Inc.). FIGS. 3B and 3C illustrate SMN1-luc cells treated for 24 hours at increasing concentrations of SAHA. The amount of SMN-luciferase fusion protein detected by anti-luciferase antibody (FIG. 3B) is similar to the % increase in luciferase activity in the same samples (FIG. 3C). FIGS. 3D and 3E illustrate SMN2-luc cells treated for 24 hours with increasing amounts of SAHA or sodium butyrate. The increase in SMN-luciferase fusion protein (FIG. 3D) correlates with luciferase activity (FIG. 3E). Experiments were performed 3 times with similar results. Blots shown are representative.

FIGS. 4A and 4B show analysis of SMN-luciferase fusion transcripts by qRT-PCR. FIG. 4A is a schematic of the primer design for qRT-PCR. Primer pairs were chosen to amplify only the SMN-luciferase fusion transcripts but not endogenous SMN. Primer 1 overlaps a unique Xho I site (*). Primers 1 and 2 can only amplify full-length SMN-luc transcripts that contain exon 7. Primers 1 and 3 amplify SMN-luc reporter transcripts (both exon 7 included and excluded). FIG. 4B illustrates the comparison of increases in amount of total reporter transcripts (lined bars) and amount of exon 7 included reporter transcripts (white bars). Cells were treated at increasing concentrations of compound for 24 hours. Percent increase was calculated in relation to treatment with DMSO and normalized to GAPDH.

FIGS. 5A-5C show over-expression of the splicing factors hTra2β and SF2/ASF. SMN2-luciferase reporter cells were transfected with increasing amounts of HA-tagged hTra2β or SF2/ASF. Cells were incubated for 48 hours and assayed for luciferase activity. FIG. 5A shows the percent increase calculated in relation to treatment with control DNA transfection and normalized to internal renilla control. FIG. 5B illustrates that transfected protein expression was confirmed using anti-HA antibody. The asterisk denotes a background HA band. Actin was used as a loading control. FIG. 5C illustrates the comparison of increases in amount of total reporter transcripts (gray bars), and amount of exon 7 included reporter transcripts (white bars). Percent increase was calculated in relation to treatment with DMSO and normalized to GAPDH.

FIGS. 6A-6C show hit confirmation in the reporter cells. FIG. 6A depicts structures of three hits from the high-throughput screen. FIG. 6B illustrates 12-point dose response experiments. Each compound was tested with the reporter cell lines at 12 concentrations (0.17, 0.5, 1.5, 4.5, 13.7, 41, 123, 370, 1111, 3333, 10,000, 30,000 nM) Black-SMN2-luc cells; grey—SMN1-luc cells; dotted line—SV40 control. Y-axis represents % activation over DMSO control. All points were tested in quadruplicate and plotted as mean±SEM. Curves were created by linear regression using Prism4 (GraphPad Software Inc.). FIG. 6C illustrates primary human fibroblast lysates from carrier (3814; SMN1^+/−; SMN2^+/+) and depicts SMA (3813; SMN1^−/−; SMN2^+/+) cells that were blotted with antibodies to SMN and a-tubulin. Cells were treated for 48 hours with increasing concentrations of compound. Fold increase was calculated in relation to DMSO treated 3813 and normalized to tubulin levels. Experiments were performed 3 times. Blots shown are representative.

FIG. 7 shows original and new reporter assay comparison. Comparison of luciferase activity for equivalent numbers of previous generation reporter cells, mixed population SMN1-luc, mixed population SMN2-luc, clonal SMN1-luc and clonal SMN2-luc cells. Luciferase activity was scored as relative light units (RLU).

FIG. 8 shows survival proportions of animals in a mouse model of spinal muscular atrophy treated with compound 76070, DMSO, or untreated.

FIG. 9 shows average weights of animals in a mouse model of spinal muscular atrophy treated with compound 76070, DMSO, or untreated.

FIG. 10 shows percent weight gained from birth to peak of animals in a mouse model of spinal muscular atrophy treated with compound 76070, DMSO, or untreated.

FIG. 11 shows actual time to right of the compound 76070-treated group. Animals are placed on their backs and assayed for the time it requires for them to right themselves. Thirty (30) seconds or greater is considered a failure to right and scored as 30 sec.

FIG. 12 shows actual time to right of the DMSO-treated group. Animals are placed on their backs and assayed for the time it requires for them to right themselves. Thirty (30) seconds or greater is considered a failure to right and scored as 30 sec.

FIG. 13 shows actual time to right of the untreated group. Animals are placed on their backs and assayed for the time it requires for them to right themselves. Thirty (30) seconds or greater is considered a failure to right and scored as 30 sec.

FIG. 14 shows the average time to right between postnatal day 7 and postnatal day 20 of the untreated, DMSO, and compound 76070-treated groups. Animals are placed on their backs and assayed for the time it requires for them to right themselves. Thirty (30) seconds or greater is considered a failure to right and scored as 30 sec.

FIG. 15 shows the percentage of animals able to right between postnatal day 7 and postnatal day 20 of the untreated, DMSO, and compound 76070-treated groups.

FIG. 16 shows the actual time to right on postnatal day 9 of untreated, DMSO, and compound 76070-treated groups.

FIG. 17 shows survival proportions of animals in a mouse model of spinal muscular atrophy treated with compound 212014, DMSO, or untreated.

FIG. 18 shows average weights of animals in a mouse model of spinal muscular atrophy treated with compound 212014, DMSO, or untreated.

FIG. 19 shows percent weight gained from birth to peak of animals in a mouse model of spinal muscular atrophy treated with compound 212014, DMSO, or untreated.

FIG. 20 shows actual time to right of the compound 212014-treated group.

FIG. 21 shows actual time to right of the untreated group.

FIG. 22 shows actual time to right of the DMSO-treated group.

FIG. 23 shows percentage of animals able to right between postnatal day 7 and postnatal day 19 of the untreated, DMSO, and compound 212014-treated groups.

FIG. 24 shows the average time to right between postnatal day 7 and postnatal day 21 of the untreated, DMSO, and compound 212014-treated groups.

FIG. 25A shows luciferase activities (-□-) in SMN2 reporter cells treated with LDDN-75654, LDN-212016, LDN-76070, and LDN-212391. The curve represented by -Δ is the internal control renilla luciferase and the curve represented by -∘- is the luciferase activity in SMN1 reporter cells.

FIG. 25B shows SMN protein levels in 3813 cells by immunoblot and gem counts. Cells were treated with LDN-75654 (left two panels) or LDN-76070 (right two panels) for 48 hours. Graphs plot the number of gems per 100 nuclei where 3813 cells are designated by lined bars and 3814 by solid bars. Data are presented as mean±SEM for three experiments and were analyzed using Prism4 (GraphPad Software Inc.). Each data point was compared to DMSO control using t-test. * (P<0.05) ** (P<0.01) *** (P<0.001).

FIG. 26A shows survival proportions of animals in a mouse model of spinal muscular atrophy treated with compounds. FIG. 26B shows average weights of animals in a mouse model of spinal muscular atrophy treated with compounds.

FIG. 27 shows survival proportions of animals in a mouse model of spinal muscular atrophy treated with compounds. Animals were treated once a day with 20 mg/kg by IP injection starting on post natal day (PND) 1.

FIG. 28 shows time to right of mice treated with compounds. Animals are placed on their backs and assayed for the time it requires for them to right themselves. Thirty (30) seconds or greater is considered a failure to right and scored as 30 sec.

FIG. 29 shows SMN protein levels in treated animals. Animals were harvested on postnatal day 7 and blotted for SMN and IP90.

FIG. 30 shows a vector map of the SMN1 luciferase vector (SEQ ID NO:8).

FIG. 31 shows a vector map of the SMN2 luniferase vector (SEQ ID NO:9).

DETAILED DESCRIPTION 1. General Description of Compounds of the Disclosure

According to one embodiment, the present disclosure provides a compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L¹is independently a covalent bond or an optionally substituted bivalent C_1-6hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)2-, —S(O)2N(R′)—, —N(R′)S(O)2-, —OC(O)—, or —C(O)O—;
each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

According to one embodiment, the present disclosure provides a compound of formula II:

or a pharmaceutically acceptable salt thereof, wherein:

each of Ring A′ and Ring B′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L²is —C(O)N(R′)—;
R′ is —R, —C(O)R, —CO₂R, or —SO₂R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

According to one embodiment, the present disclosure provides a compound of formula III:

or a pharmaceutically acceptable salt thereof, wherein:

Ring C″ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R¹, R²and R³is independently halogen, R′, —C(O)R′, —C(S)R′, —CO2R′, —C(O)N(R′)2, —C(S)N(R′)₂, —S(O)R′, —SO₂R′, —SO2N(R′)₂, —OR′, —O—(C_1-6aliphatic)-N(R′)₂, —O—(C_1-6aliphatic)-OR′, —OC(O)R′, —SR′, —NO₂, —N(R′)₂, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′;
a is 1-4;
b is 1-5;
X¹is —C(R^x)₂—, —NR^x—, —NR^xC(R^x)₂— or —OC(R^x)₂—; X²is —C(R^x)₂— or —NR^x—;
each R^xis R′, —(C1-6 aliphatic)-N(R′)₂, or —(C_1-6aliphatic)-OR′;
each R′ is —R, —C(O)R, —CO₂R, or —SO₂R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

2. Definitions

Compounds of this disclosure include those described generally above, and are further illustrated by the embodiments, sub-embodiments, and species disclosed herein. As used herein, the following definitions shall apply unless otherwise indicated. For purposes of this disclosure, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75^thEd. Additionally, general principles of organic chemistry are described in “Organic Chemistry,” Thomas Sorrell, University Science Books, Sausalito: 1999, and “March's Advanced Organic Chemistry,” 5^thEd., Ed.: Smith, M. B. and March, J., John Wiley & Sons, New York: 2001, the entire contents of which are hereby incorporated by reference to the extent they are consistent herewith.

As described herein, compounds of the disclosure may optionally be substituted with one or more substituents, such as are illustrated generally above, or as exemplified by particular classes, subclasses, and species of the disclosure. It will be appreciated that the phrase “optionally substituted” is used interchangeably with the phrase “substituted or unsubstituted.” In general, the term “substituted,” whether preceded by the term “optionally” or not, refers to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent. Unless otherwise indicated, an optionally substituted group may have a substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this disclosure are preferably those that result in the formation of stable or chemically feasible compounds.

The term “stable,” as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and preferably their recovery, purification, and use for one or more of the purposes disclosed herein. In some embodiments, a stable compound or chemically feasible compound is one that is not substantially altered when kept at a temperature of 40° C. or less, in the absence of moisture or other chemically reactive conditions, for at least a week.

The term “aliphatic” or “aliphatic group,” as used herein, means a straight-chain (i.e., unbranched) or branched, substituted or unsubstituted hydrocarbon chain that is completely saturated or that contains one or more units of unsaturation, or a monocyclic hydrocarbon or bicyclic hydrocarbon that is completely saturated or that contains one or more units of unsaturation, but which is not aromatic (also referred to herein as “carbocycle” “cycloaliphatic” or “cycloalkyl”), that has a single point of attachment to the rest of the molecule. Unless otherwise specified, aliphatic groups contain 1-20 aliphatic carbon atoms. In some embodiments, aliphatic groups contain 1-6 aliphatic carbon atoms. In yet other embodiments aliphatic groups contain 1-4 aliphatic carbon atoms. In some embodiments, “cycloaliphatic” (or “carbocycle” or “cycloalkyl”) refers to a monocyclic C3-C8 hydrocarbon or bicyclic C₈-C12 hydrocarbon that is completely saturated or that contains one or more units of unsaturation, but which is not aromatic, that has a single point of attachment to the rest of the molecule wherein any individual ring in said bicyclic ring system has 3-7 members. Suitable aliphatic groups include, but are not limited to, linear or branched, substituted or unsubstituted alkyl, alkenyl, alkynyl groups and hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl. In other embodiments, an aliphatic group may have two geminal hydrogen atoms replaced with oxo (a bivalent carbonyl oxygen atom ═O), or a ring-forming substituent, such as —O-(straight or branched alkylene or alkylene)-O— to form an acetal or ketal.

In certain embodiments, exemplary aliphatic groups include, but are not limited to, ethynyl, 2-propynyl, 1-propenyl, 2-butenyl, 1,3-butadienyl, 2-pentenyl, vinyl (ethenyl), allyl, isopropenyl, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl, neo-pentyl, tert-pentyl, cyclopentyl, hexyl, isohexyl, sec-hexyl, cyclohexyl, 2-methylpentyl, tert-hexyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1,3-dimethylbutyl, and 2,3-dimethyl but-2-yl.

The term “heterocycle,” “heterocyclyl,” “heterocycloaliphatic,” or “heterocyclic” as used herein means non-aromatic, monocyclic, bicyclic, or tricyclic ring systems in which one or more ring members is an independently selected heteroatom. In some embodiments, the “heterocycle,” “heterocyclyl,” “heterocycloaliphatic,” or “heterocyclic” group has three to fourteen ring members in which one or more ring members is a heteroatom independently selected from oxygen, sulfur, nitrogen, or phosphorus, and each ring in the system contains 3 to 7 ring members.

A heterocyclic ring can be attached to its pendant group at any heteroatom or carbon atom that results in a stable structure and, when specified, any of the ring atoms can be optionally substituted. Examples of such saturated or partially unsaturated heterocyclic radicals include, without limitation, tetrahydrofuranyl, tetrahydrothiophenyl pyrrolidinyl, piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl.

The term “heteroatom” means one or more of oxygen, sulfur, nitrogen, phosphorus, or silicon (including, any oxidized form of nitrogen, sulfur, phosphorus, or silicon; the quaternized form of any basic nitrogen or; a substitutable nitrogen of a heterocyclic ring, for example N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl) or NR⁺ (as in N-substituted pyrrolidinyl).

The term “unsaturated,” as used herein, means that a moiety has one or more units of unsaturation.

As used herein, the term “partially unsaturated” refers to a ring moiety that includes at least one double or triple bond. The term “partially unsaturated” is intended to encompass rings having multiple sites of unsaturation, but is not intended to include aryl or heteroaryl moieties, as herein defined.

The term “aryl” used alone or as part of a larger moiety as in “aralkyl,” “aralkoxy,” or “aryloxyalkyl,” refers to monocyclic, bicyclic, and tricyclic ring systems having a total of five to fourteen ring members, wherein one or more ring in the system is aromatic and wherein each ring in the system contains 3 to 7 ring members. The term “aryl” may be used interchangeably with the term “aryl ring”. The term “aryl” also refers to heteroaryl ring systems as defined herein below. In certain embodiments of the present disclosure, “aryl” refers to an aromatic ring system which includes, but not limited to, phenyl, biphenyl, naphthyl, anthracyl and the like, which may bear one or more substituents. Also included within the scope of the term “aryl,” as it is used herein, is a group in which an aromatic ring is fused to one or more non-aromatic rings, such as indanyl, phthalimidyl, naphthimidyl, phenanthridinyl, or tetrahydronaphthyl, and the like.

The term “heteroaryl,” used alone or as part of a larger moiety as in “heteroaralkyl” or “heteroarylalkoxy,” refers to monocyclic, bicyclic, and tricyclic ring systems having a total of five to fourteen ring members, wherein one or more ring in the system is aromatic, one or more ring in the system contains one or more heteroatoms, and wherein each ring in the system contains 3 to 7 ring members. The term “heteroaryl” may be used interchangeably with the term “heteroaryl ring” or the term “heteroaromatic”. Heteroaryl groups include thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, and pteridinyl.

The terms “heteroaryl” and “heteroar-,” as used herein, also include groups in which a heteroaromatic ring is fused to one or more aryl, cycloaliphatic, or heterocyclyl rings. Exemplary heteroaryl rings include indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one.

As described herein, compounds of the disclosure may contain “optionally substituted” moieties. In general, the term “substituted,” whether preceded by the term “optionally” or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an “optionally substituted” group may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this disclosure are preferably those that result in the formation of stable or chemically feasible compounds. The term “stable,” as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein.

Suitable monovalent substituents on a substitutable carbon atom of an “optionally substituted” group are independently halogen; —(CH₂)_0-4R^∘; —(CH₂)_0-4OR^∘; —O(CH2)_0-4R^∘, —O—(CH₂)_0-4C(O)OR^∘; —(CH₂)_0-4CH(OR^∘)₂; —(CH₂)_0-4SR^∘; —(CH₂)_0-4Ph, which may be substituted with R^∘; —(CH₂)_0-4O(CH₂)_0-4Ph which may be substituted with R^∘; —CH═CHPh, which may be substituted with R^∘; —(CH₂)_0-4O(CH₂)_0-1-pyridyl which may be substituted with R^∘; —NO₂; —CN; —N₃; —(CH₂)_0-4N(R^∘)₂; —(CH₂)_0-4N(R^∘)C(O)R^∘; —N(R^∘)C(S)R^∘; —(CH₂)_0-4N(R^∘)C(O)NR₂; —N(R^∘)C(S)NR^∘₂; —(CH₂)_0-4N(R^∘)C(O)OR^∘; —N(R^∘)N(R^∘)C(O)R^∘; —N(R^∘)N(R^∘)C(O)NR^∘₂; —N(R^∘)N(R^∘)C(O)OR^∘; —(CH₂)_0-4C(O)R^∘; —C(S)R^∘; —(CH₂)_0-4C(O)OR^∘; —(CH₂)_0-4C(O)SR^∘; —(CH₂)_0-4C(O)OSiR₃; —(CH₂)_0-4C(O)R^∘; —OC(O)(CH₂)_0-4SR^∘, SC(S)SR^∘; —(CH₂)_0-4SC(O)R^∘; —(CH₂)_0-4C(O)NR^∘₂; —C(S)NR^∘₂; —C(S)SR^∘; —SC(S)SRO, —(CH₂)_0-4OC(O)NR^∘₂; —C(O)N(OR^∘)R^∘; —C(O)C(O)R^∘; —C(O)CH₂C(O)R^∘; —C(NOR^∘)R^∘; —(CH₂)_0-4SSR^∘; —(CH₂)_0-4S(O)₂R^∘; —(CH₂)_{0- 4}S(O)₂OR^∘; —(CH₂)_0-4S(O)₂R^∘; —S(O)₂NR^∘₂; —(CH₂)_0-4S(O)R^∘; —N(R^∘)S(O)₂NR^∘₂; —N(R^∘)S(O)₂R^∘; —N(OR^∘)R^∘; —C(NH)NR^∘₂; —P(O)₂R^∘; —P(O)R^∘₂; —OP(O)R^∘₂; —OP(O)(OR^∘)₂; SiR^∘₃; —(C_1-4straight or branched alkylene)O—N(R^∘)₂; or —(C_1-4straight or branched alkylene)C(O)O—N(R^∘)₂, wherein each R^∘may be substituted as defined below and is independently hydrogen, C_1-6aliphatic, —CH₂Ph, —O(CH₂)_0-1Ph, —CH₂-(5-6 membered heteroaryl ring), or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R^∘, taken together with their intervening atom(s), form a 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, which may be substituted as defined below.

Suitable monovalent substituents on R^∘(or the ring formed by taking two independent occurrences of R^∘together with their intervening atoms), are independently halogen, —(CH2)0-2R^•, -(haloR^•), —(CH2)0-2OH, —(CH2)0-2OR^•, —(CH2)0-2CH(OR^•)2; —O(haloR^•), —CN, —N3, —(CH2)0-2C(O)R^•, —(CH2)0-2C(O)OH, —(CH2)0-2C(O)OR^•, —(CH2)0-2SR^•, —(CH2)0-2SH, —(CH2)0-2NH2, —(CH2)0-2NHR^•, —(CH2)0-2NR^•, —NO, —SiR^•, —OSiR^•, —C(O)SR^•—(C1-4 straight or branched alkylene)C(O)OR^•, or —SSR^• wherein each R^• is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently selected from C_1-4aliphatic, —CH₂Ph, —O(CH₂)_0-1Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents on a saturated carbon atom of R^∘include ═O and ═S.

Suitable divalent substituents on a saturated carbon atom of an “optionally substituted” group include the following: ═O, ═S, ═NNR*₂, ═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O)₂R*, ═NR*, ═NOR*, —O(C(R*₂))_2-3O—, or —S(C(R*₂))_2-3S—, and ═C(R*)₂, wherein each independent occurrence of R* is selected from hydrogen, C_1-6aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents that are bound to vicinal substitutable carbons of an “optionally substituted” group include: —O(CR*₂)_2-3O—, wherein each independent occurrence of R is selected from hydrogen, C_1-6aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R* include halogen, —R^•, -(haloR^•), —OH, —OR′, —O(haloR^•), —CN, —C(O)OH, —C(O)OR′, —NH2, —NHR^•, —NR^•, or —NO, wherein each R^• is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C_1-4aliphatic, —CH₂Ph, —O(CH₂)_0-1Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionally substituted” group include —R^†, —NR^†₂, —C(O)R^†, —C(O)OR^†, —C(O)C(O)R^†, —C(O)CH₂C(O)R^†, —S(O)₂R^†, —S(O)₂NR^†₂, —C(S)NR^†₂, —C(NH)NR^†₂, or —N(R^†)S(O)₂R^†; wherein each R^†is independently hydrogen, C_1-6aliphatic which may be substituted as defined below, unsubstituted —OPh, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R^†, taken together with their intervening atom(s) form an unsubstituted 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of Rt are independently halogen, —R^•, -(haloR^•), —OH, —OR^•, —O(haloR^•), —CN, —C(O)OH, —C(O)OR^•, —NH², —NHR^•, —NR^•, or —NO₂, wherein each R^• is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C_1-4aliphatic, —CH2Ph, —O(CH₂)_0-1Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Unless otherwise stated, structures depicted herein are also meant to include all isomeric (e.g., enantiomeric, diastereomeric, and geometric (or conformational)) forms of the structure; for example, the R and S configurations for each asymmetric center, (Z) and (E) double bond isomers, and (Z) and (E) conformational isomers. Therefore, single stereochemical isomers as well as enantiomeric, diastereomeric, and geometric (or conformational) mixtures of the present compounds are within the scope of the disclosure.

Unless otherwise stated, all tautomeric forms of the compounds of the disclosure are within the scope of the disclosure.

Additionally, unless otherwise stated, structures depicted herein are also meant to include compounds that differ only in the presence of one or more isotopically enriched atoms.

For example, compounds having the present structures except for the replacement of hydrogen by deuterium or tritium, or the replacement of a carbon by a ¹¹C- or ¹³C- or ¹⁴C-enriched carbon are within the scope of this disclosure. Such compounds are useful, for example, as analytical tools or probes in biological assays.

3. Description of Exemplary Compounds

According to one embodiment, the present disclosure provides a compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L¹is independently a covalent bond or an optionally substituted bivalent C_1-6hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—;
R′ is —R, —C(O)R, —CO₂R, or —SO₂R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
R is hydrogen, or an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

According to one embodiment, the present disclosure provides a compound of formula II:

or a pharmaceutically acceptable salt thereof, wherein:

each of Ring A′ and Ring B′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L²is —C(O)N(R′)—;
each R′ is independently —R, —C(O)R, —CO₂R, or —SO₂R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

According to one embodiment, the present disclosure provides a compound of formula III:

or a pharmaceutically acceptable salt thereof, wherein:

Ring C″ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R¹, R²and R³is independently halogen, R′, —C(O)R′, —C(S)R′, —CO2R′, —C(O)N(R′)2, —C(S)N(R′)₂, —S(O)R′, —SO₂R′, —SO₂N(R′)₂, —OR′, —O—(C_1-6aliphatic)-N(R′)₂, —O—(C_1-6aliphatic)-OR′, —OC(O)R′, —SR′, —NO₂, —N(R′)₂, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′;
a is 1-4;
b is 1-5;
X¹is —C(R^x)₂—, —NR^x—, —NR^xC(R^x)₂— or —OC(R^x)₂—;
X²is —C(R^x)₂— or —NR^x—;
each R^xis independently R′, —(C_1-6aliphatic)-N(R′)₂, or —(C_1-6aliphatic)-OR′;
each R′ is independently —R, —C(O)R, —CO₂R, or —SO2R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

As generally defined above, Ring A is an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

In some embodiments, Ring A is optionally substituted phenyl. In some embodiments, Ring A is substituted phenyl. In some embodiments, Ring A is phenyl. In some embodiments, Ring A is phenyl substituted with one or more halogen atoms. In some embodiments, Ring A is phenyl substituted with two halogen atoms. In some embodiments, Ring A is 2-fluoro-5-chlorophenyl. In some embodiments, Ring A is 2-fluoro-5-bromophenyl. In some embodiments, Ring A is 3-chloro-4-flluorophenyl.

In some embodiments, Ring A is an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, Ring A is an optionally substituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring A is a substituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring A is an unsubstituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring A is an optionally substituted 3-7 membered unsaturated carbocyclic ring. In some embodiments, Ring A is a substituted 3-7 membered unsaturated carbocyclic ring. In some embodiments, Ring A is an unsubstituted 3-7 membered unsaturated carbocyclic ring.

In some embodiments, Ring A is an optionally substituted cycloheptyl. In some embodiments, Ring A is an optionally substituted cyclohexyl. In some embodiments, Ring A is an optionally substituted cyclopentyl. In some embodiments, Ring A is an optionally substituted cyclobutyl. In some embodiments, Ring A is an optionally substituted cyclopropyl.

In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring. In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic saturated carbocyclic ring. In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic partially unsaturated carbocyclic ring. In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic aryl ring.

In some embodiments, Ring A is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is a substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A is an unsubstituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A is an optionally substituted 5 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring A is an optionally substituted 6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A is an optionally substituted 5-membered monocyclic heteroaryl ring having 1 heteroatom selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is selected from pyrrolyl, furanyl, or thienyl.

In some embodiments, Ring A is an optionally substituted 5-membered heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring A groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring A is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring A is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring A is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring A is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring A groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl.

In some embodiments, Ring A is an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is a substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an unsubstituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A is an optionally substituted 6 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 oxygen atom. In some embodiments, Ring A is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 oxygen atom having the structure

In certain embodiments, Ring A is a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A is oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, oxepaneyl, aziridineyl, azetidineyl, pyrrolidinyl, piperidinyl, azepanyl, thiiranyl, thietanyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, thiepanyl, dioxolanyl, oxathiolanyl, oxazolidinyl, imidazolidinyl, thiazolidinyl, dithiolanyl, dioxanyl, morpholinyl, oxathianyl, piperazinyl, thiomorpholinyl, dithianyl, dioxepanyl, oxazepanyl, oxathiepanyl, dithiepanyl, diazepanyl, dihydrofuranonyl, tetrahydropyranonyl, oxepanonyl, pyrolidinonyl, piperidinonyl, azepanonyl, dihydrothiophenonyl, tetrahydrothiopyranonyl, thiepanonyl, oxazolidinonyl, oxazinanonyl, oxazepanonyl, dioxolanonyl, dioxanonyl, dioxepanonyl, oxathiolinonyl, oxathianonyl, oxathiepanonyl, thiazolidinonyl, thiazinanonyl, thiazepanonyl, imidazolidinonyl, tetrahydropyrimidinonyl, diazepanonyl, imidazolidinedionyl, oxazolidinedionyl, thiazolidinedionyl, dioxolanedionyl, oxathiolanedionyl, piperazinedionyl, morpholinedionyl, thiomorpholinedionyl, tetrahydropyranyl, tetrahydrofuranyl, morpholinyl, thiomorpholinyl, piperidinyl, piperazinyl, pyrrolidinyl, tetrahydrothiophenyl, or tetrahydrothiopyranyl. In some embodiments, Ring A is an optionally substituted 5 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, two optional substituents are taken together with their intervening atom(s) to form a 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, which may be substituted. In some embodiments, Ring A is an optionally substituted group selected from

In certain embodiments, Ring A is an optionally substituted 5-6 membered partially unsaturated monocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A is an optionally substituted tetrahydropyridinyl, dihydrothiazolyl, dihydrooxazolyl, or oxazolinyl group.

In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted indolinyl. In some embodiments, Ring A is an optionally substituted isoindolinyl. In some embodiments, Ring A is an optionally substituted 1,2,3,4-tetrahydroquinoline. In some embodiments, Ring A is an optionally substituted 1,2,3,4-tetrahydroisoquinoline.

In some embodiments, Ring A is an optionally substituted group selected from or

In certain embodiments, Ring A is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted 5,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring A is an optionally substituted 5,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A is an optionally substituted 5,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted indolyl. In some embodiments, Ring A is an optionally substituted azabicyclo[3.2.1]octanyl. In certain embodiments, Ring A is an optionally substituted 5,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted azaindolyl. In some embodiments, Ring A is an optionally substituted benzimidazolyl. In some embodiments, Ring A is an optionally substituted benzothiazolyl. In some embodiments, Ring A is an optionally substituted benzoxazolyl. In some embodiments, Ring A is an optionally substituted indazolyl. In certain embodiments, Ring A is an optionally substituted 5,6-fused heteroaryl ring having 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring A is an optionally substituted 6,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted 6,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring A is an optionally substituted 6,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is an optionally substituted quinolinyl. In some embodiments, Ring A is an optionally substituted isoquinolinyl. According to one aspect, Ring A is an optionally substituted 6,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A is a quinazoline or a quinoxaline.

In some embodiments, two substituents on Ring A are optionally taken together with their intervening atoms to form an optionally substituted, 3-7 membered saturated, partially unsaturated or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring A are optionally taken together with their intervening atoms to form an optionally substituted phenyl. In some embodiments, two substituents on Ring A are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, two substituents on Ring A are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring A are optionally taken together with their intervening atoms to form an optionally substituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur.

As generally defined above, Ring B is an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

In some embodiments, Ring B is an optionally substituted phenyl. In some embodiments, Ring B is a substituted phenyl. In some embodiments, Ring B is phenyl. In some embodiments, Ring B is a phenyl substituted with one or more halogen atoms. In some embodiments, Ring B is a phenyl substituted with two halogen atoms. In some embodiments, Ring B is 2-fluoro-5-chlorophenyl. In some embodiments, Ring B is 2-fluoro-5-bromophenyl. In some embodiments, Ring B is 3-chloro-4-flluorophenyl.

In some embodiments, Ring B is an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, Ring B is an optionally substituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring B is a substituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring B is an unsubstituted 3-7 membered saturated carbocyclic ring. In some embodiments, Ring B is an optionally substituted 3-7 membered unsaturated carbocyclic ring. In some embodiments, Ring B is a substituted 3-7 membered unsaturated carbocyclic ring. In some embodiments, Ring B is an unsubstituted 3-7 membered unsaturated carbocyclic ring.

In some embodiments, Ring B is an optionally substituted cycloheptyl. In some embodiments, Ring B is an optionally substituted cyclohexyl. In some embodiments, Ring B is an optionally substituted cyclopentyl. In some embodiments, Ring B is an optionally substituted cyclobutyl. In some embodiments, Ring B is an optionally substituted cyclopropyl.

In some embodiments, Ring B is an optionally substituted 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring. In some embodiments, Ring B is an optionally substituted 8-10 membered bicyclic saturated carbocyclic ring. In some embodiments, Ring B is an optionally substituted 8-10 membered bicyclic partially unsaturated carbocyclic ring. In some embodiments, Ring B is an optionally substituted 8-10 membered bicyclic aryl ring.

In some embodiments, Ring B is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is a substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an unsubstituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B is an optionally substituted 5 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring B is an optionally substituted 6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B is an optionally substituted 5-membered monocyclic heteroaryl ring having 1 heteroatom selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is selected from pyrrolyl, furanyl, or thienyl.

In some embodiments, Ring B is an optionally substituted 5-membered heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring B groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring B is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring B is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring B is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring B is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring B groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl.

In some embodiments, Ring B is an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is a substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an unsubstituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B is an optionally substituted 6 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 oxygen atom. In some embodiments, Ring B is an optionally substituted 6 membered partially unsaturated heterocyclic ring having 2 oxygen atom having the structure

In certain embodiments, Ring B is a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B is oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, oxepaneyl, aziridineyl, azetidineyl, pyrrolidinyl, piperidinyl, azepanyl, thiiranyl, thietanyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, thiepanyl, dioxolanyl, oxathiolanyl, oxazolidinyl, imidazolidinyl, thiazolidinyl, dithiolanyl, dioxanyl, morpholinyl, oxathianyl, piperazinyl, thiomorpholinyl, dithianyl, dioxepanyl, oxazepanyl, oxathiepanyl, dithiepanyl, diazepanyl, dihydrofuranonyl, tetrahydropyranonyl, oxepanonyl, pyrolidinonyl, piperidinonyl, azepanonyl, dihydrothiophenonyl, tetrahydrothiopyranonyl, thiepanonyl, oxazolidinonyl, oxazinanonyl, oxazepanonyl, dioxolanonyl, dioxanonyl, dioxepanonyl, oxathiolinonyl, oxathianonyl, oxathiepanonyl, thiazolidinonyl, thiazinanonyl, thiazepanonyl, imidazolidinonyl, tetrahydropyrimidinonyl, diazepanonyl, imidazolidinedionyl, oxazolidinedionyl, thiazolidinedionyl, dioxolanedionyl, oxathiolanedionyl, piperazinedionyl, morpholinedionyl, thiomorpholinedionyl, tetrahydropyranyl, tetrahydrofuranyl, morpholinyl, thiomorpholinyl, piperidinyl, piperazinyl, pyrrolidinyl, tetrahydrothiophenyl, or tetrahydrothiopyranyl. In some embodiments, Ring B is an optionally substituted 5 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring B is an optionally substituted 5-6 membered partially unsaturated monocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B is an optionally substituted tetrahydropyridinyl, dihydrothiazolyl, dihydrooxazolyl, or oxazolinyl group.

In some embodiments, Ring B is an optionally substituted 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted indolinyl. In some embodiments, Ring B is an optionally substituted isoindolinyl. In some embodiments, Ring B is an optionally substituted 1,2,3,4-tetrahydroquinoline. In some embodiments, Ring B is an optionally substituted 1,2,3,4-tetrahydroisoquinoline. In some embodiments, Ring B is an optionally substituted group selected from

In certain embodiments, Ring B is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted 5,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring B is an optionally substituted 5,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B is an optionally substituted 5,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted indolyl. In some embodiments, Ring B is an optionally substituted azabicyclo[3.2.1]octanyl. In certain embodiments, Ring B is an optionally substituted 5,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted azaindolyl. In some embodiments, Ring B is an optionally substituted benzimidazolyl. In some embodiments, Ring B is an optionally substituted benzothiazolyl. In some embodiments, Ring B is an optionally substituted benzoxazolyl. In some embodiments, Ring B is an optionally substituted indazolyl. In certain embodiments, Ring B is an optionally substituted 5,6-fused heteroaryl ring having 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring B is an optionally substituted 6,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted 6,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring B is an optionally substituted 6,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is an optionally substituted quinolinyl. In some embodiments, Ring B is an optionally substituted isoquinolinyl. According to one aspect, Ring B is an optionally substituted 6,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B is a quinazoline or a quinoxaline.

In some embodiments, two substituents on Ring B are optionally taken together with their intervening atoms to form an optionally substituted, 3-7 membered saturated, partially unsaturated or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring B are optionally taken together with their intervening atoms to form an optionally substituted phenyl. In some embodiments, two substituents on Ring B are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, two substituents on Ring B are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring B are optionally taken together with their intervening atoms to form an optionally substituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur.

As generally defined above, L¹is independently a covalent bond or an optionally substituted bivalent C_1-6hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—, wherein each R′ is independently as defined above and described herein.

In some embodiments, L¹is a covalent bond.

In some embodiments, L¹is an optionally substituted bivalent C_1-6hydrocarbon chain, wherein one or more methylene units of L¹are optionally and independently replaced by —O—, —S—, —N(R′)—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R′)—, —S(O)—, —S(O)₂—, —S(O)₂N(R′)—, —N(R′)S(O)₂—, —OC(O)—, or —C(O)O—, wherein each R′ is independently as defined above and described herein.

In some embodiments, L¹is —C(O)NR′—, wherein R′ is as defined above and described herein. In some embodiments, L¹is —C(O)NR—, wherein R is as defined above and described herein. In some embodiments, L¹is —CONH—. In some embodiments, L¹is —NHCO—.

In some embodiments, Ring A is an optionally substituted group selected from

Ring B is optionally substituted phenyl; and L¹is a covalent bond.

As generally defined above, each R′ is independently —R, —C(O)R, —CO₂R, or —SO₂R, or:

- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur.

In some embodiments, each R′ is independently —R, —C(O)R, —CO₂R, or —SO₂R, wherein R is as defined above and described herein. In some embodiments, R′ is R, wherein R is as defined above and described herein. In some embodiments, R′ is hydrogen. In some embodiments, R′ is —(CH₂)_1-6N(R)₂, wherein each R is independently as defined above and described herein. In some embodiments, R′ is —(CH₂)₂N(CH₃)₂.

As generally defined above, each R is hydrogen, or an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, R is hydrogen.

In some embodiments, R is an optionally substituted group selected from C_1-6aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, R is an optionally substituted C_1-6aliphatic. In some embodiments, R is an optionally substituted phenyl. In some embodiments, R is an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, R is an optionally substituted 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring. In some embodiments, R is an optionally substituted a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, R is an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, R is an optionally substituted 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, R is optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A is an optionally substituted group selected from phenyl, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; Ring B is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; and L¹is —CONH— or —NHCO—.

In some embodiments, Ring A is an optionally substituted phenyl; Ring B is an optionally substituted 5 membered monocyclic heteroaryl ring having two heteroatoms independently selected from nitrogen, oxygen, or sulfur; and L¹is —CONH— or —NHCO—.

In some embodiments, Ring A is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; Ring B is an optionally substituted 5 membered monocyclic heteroaryl ring having two heteroatoms independently selected from nitrogen, oxygen, or sulfur; and L¹is —CONH— or —NHCO—.

According to one embodiment, the present disclosure provides a compound of formula I having the structure of formula II:

or a pharmaceutically acceptable salt thereof, wherein:

each of Ring A′ and Ring B′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L²is —C(O)N(R′)—; and
wherein each of R′ and R is independently as defined above and described herein.

As generally defined above, Ring A′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A′ is an optionally substituted phenyl. In some embodiments, Ring A′ is a substituted phenyl. In some embodiments, Ring A′ is phenyl. In some embodiments, Ring A′ is a phenyl substituted with one or more halogen atoms. In some embodiments, Ring A′ is a phenyl substituted with two halogen atoms. In some embodiments, Ring A′ is 2-fluoro-5-chlorophenyl. In some embodiments, Ring A′ is 2-fluoro-5-bromophenyl.

In some embodiments, Ring A′ is 3-chloro-4-flluorophenyl.

In some embodiments, Ring A′ is an optionally substituted 8-10 membered bicyclic aryl ring. In some embodiments, Ring A′ is an optionally substituted 10 membered bicyclic aryl ring.

In some embodiments, Ring A′ is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is a substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A′ is an unsubstituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A′ is an optionally substituted 5 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring A′ is an optionally substituted 6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring A′ is an optionally substituted 5-membered monocyclic heteroaryl ring having 1 heteroatom selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is selected from pyrrolyl, furanyl, or thienyl.

In some embodiments, Ring A′ is an optionally substituted 5-membered heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A′ is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring A′ groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring A′ is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring A′ is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring A′ is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring A′ is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring A′ groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl.

In certain embodiments, Ring A′ is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is an optionally substituted 5,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring A′ is an optionally substituted 5,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring A′ is an optionally substituted 5,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is an optionally substituted indolyl. In some embodiments, Ring A′ is an optionally substituted azabicyclo[3.2.1]octanyl. In certain embodiments, Ring A′ is an optionally substituted 5,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is an optionally substituted azaindolyl. In some embodiments, Ring A′ is an optionally substituted benzimidazolyl. In some embodiments, Ring A′ is an optionally substituted benzothiazolyl. In some embodiments, Ring A′ is an optionally substituted benzoxazolyl. In some embodiments, Ring A′ is an optionally substituted indazolyl. In certain embodiments, Ring A′ is an optionally substituted 5,6-fused heteroaryl ring having 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring A′ is an optionally substituted 6,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is an optionally substituted 6,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring A′ is an optionally substituted 6,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is an optionally substituted quinolinyl. In some embodiments, Ring A′ is an optionally substituted isoquinolinyl. According to one aspect, Ring A′ is an optionally substituted 6,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring A′ is a quinazoline or a quinoxaline.

In some embodiments, two substituents on Ring A′ are optionally taken together with their intervening atoms to form an optionally substituted, 3-7 membered saturated, partially unsaturated or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring A′ are optionally taken together with their intervening atoms to form an optionally substituted phenyl. In some embodiments, two substituents on Ring A′ are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, two substituents on Ring A′ are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring A′ are optionally taken together with their intervening atoms to form an optionally substituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur.

As generally defined above, Ring B′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B′ is an optionally substituted phenyl. In some embodiments, Ring B′ is a substituted phenyl. In some embodiments, Ring B′ is phenyl. In some embodiments, Ring B′ is a phenyl substituted with one or more halogen atoms. In some embodiments, Ring B′ is a phenyl substituted with two halogen atoms. In some embodiments, Ring B′ is 2-fluoro-5-chlorophenyl. In some embodiments, Ring B′ is 2-fluoro-5-bromophenyl. In some embodiments, Ring B′ is 3-chloro-4-flluorophenyl.

In some embodiments, Ring B′ is an optionally substituted 8-10 membered bicyclic aryl ring. In some embodiments, Ring B′ is an optionally substituted 10 membered bicyclic aryl ring.

In some embodiments, Ring B′ is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is a substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an unsubstituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B′ is an optionally substituted 5 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring B′ is an optionally substituted 6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B′ is an optionally substituted 5-membered monocyclic heteroaryl ring having 1 heteroatom selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is selected from pyrrolyl, furanyl, or thienyl.

In some embodiments, Ring B′ is an optionally substituted 5-membered heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B′ is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring B′ groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring B′ is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring B′ is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring B′ is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring B′ is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring B′ groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl.

In certain embodiments, Ring B′ is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an optionally substituted 5,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring B′ is an optionally substituted 5,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring B′ is an optionally substituted 5,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an optionally substituted indolyl. In some embodiments, Ring B′ is an optionally substituted azabicyclo[3.2.1]octanyl. In certain embodiments, Ring B′ is an optionally substituted 5,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an optionally substituted azaindolyl. In some embodiments, Ring B′ is an optionally substituted benzimidazolyl. In some embodiments, Ring B′ is an optionally substituted benzothiazolyl. In some embodiments, Ring B′ is an optionally substituted benzoxazolyl. In some embodiments, Ring B′ is an optionally substituted indazolyl. In certain embodiments, Ring B′ is an optionally substituted 5,6-fused heteroaryl ring having 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring B′ is an optionally substituted 6,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an optionally substituted 6,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring B′ is an optionally substituted 6,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is an optionally substituted quinolinyl. In some embodiments, Ring B′ is an optionally substituted isoquinolinyl. According to one aspect, Ring B′ is an optionally substituted 6,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring B′ is a quinazoline or a quinoxaline.

In some embodiments, two substituents on Ring B′ are optionally taken together with their intervening atoms to form an optionally substituted, 3-7 membered saturated, partially unsaturated or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring B′ are optionally taken together with their intervening atoms to form an optionally substituted phenyl. In some embodiments, two substituents on Ring B′ are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated carbocyclic ring. In some embodiments, two substituents on Ring B′ are optionally taken together with their intervening atoms to form an optionally substituted 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, two substituents on Ring B′ are optionally taken together with their intervening atoms to form an optionally substituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen or sulfur.

As generally defined above, L²is —C(O)N(R′)—, wherein R′ is as defined above and described herein. In some embodiments, L²is —C(O)NH—. In some embodiments, L²is —C(O)N(R)—, wherein R is as defined above and described herein. In some embodiments, Ring A′ is directly connected to the carbonyl group in L². In some embodiments, Ring B′ is directly connected to the carbonyl group in L².

In some embodiments, the present disclosure provides a compound of formula II having the structure of formula II-a:

or a pharmaceutically acceptable salt thereof, wherein:

Ring A″ is an optionally substituted phenyl or benzimidazolyl ring;
Ring B″ is an optionally substituted 5-6 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
L³is —C(O)NH—;
R⁴is halogen or R;
R⁵is an optionally substituted C_1-6aliphatic;
each of d and e is independently 0-5; and
wherein R is as defined above and described herein.

As generally defined above, Ring A″ is an optionally substituted phenyl or benzimidazolyl ring.

In some embodiments, Ring A″ is optionally substituted phenyl. In some embodiments, Ring A″ is unsubstituted phenyl. In some embodiments, Ring A″ is substituted phenyl. In some embodiments, Ring A″ is 3-chloro-4-fluorophenyl. In some embodiments, Ring A″ is optionally substituted benzimidazolyl. In some embodiments, Ring A″ is unsubstituted benzimidazolyl. In some embodiments, Ring A″ is substituted benzimidazolyl.

As generally defined above, Ring B″ is an optionally substituted 5-6 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring B″ is an optionally substituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring B″ is unsubstituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring B″ is substituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In certain embodiments, Ring B″ is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring B″ groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring B″ is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring B″ is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring B″ is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring B″ is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring B″ groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl.

As generally defined above, each R⁴is independently halogen or R, wherein R is as defined above and described herein. In some embodiments, R⁴is halogen. In some embodiments, R⁴is —F. In some embodiments, R⁴is —Cl. In some embodiments, R⁴is —Br. In some embodiments, R⁴is —I. In some embodiments, R⁴is R, wherein R is as defined above and described herein.

As generally defined above, each R⁵is independently an optionally substituted C_1-6aliphatic. In some embodiments, R⁵is optionally substituted straight or branched C_1-6alkyl. In some embodiments, R⁵is optionally substituted hexyl, pentyl, butyl, propyl, ethyl or methyl. In some embodiments, R⁵is hexyl. In some embodiments, R⁵is pentyl. In some embodiments, R⁵is butyl. In some embodiments, R⁵is propyl. In some embodiments, R⁵is ethyl. In some embodiments, R⁵is methyl. In some embodiments, R⁵is isopropyl.

In some embodiments, R⁵is optionally substituted C_1-6cycloalkyl. In some embodiments, R⁵is optionally substituted cyclohexyl. In some embodiments, R⁵is optionally substituted cyclopentyl. In some embodiments, R⁵is optionally substituted cyclobutyl. In some embodiments, R⁵is optionally substituted cyclopropyl. In some embodiments, R⁵is 1-hydroxycyclobutyl. In some embodiments, R⁵is cyclohexyl, cyclopentyl, cyclobutyl, or cyclopropyl.

As generally defined above, each of d and e is independently 0-5. In some embodiments, d is 0. In some embodiments, d is 1. In some embodiments, d is 2. In some embodiments, d is 3. In some embodiments, d is 4. In some embodiments, d is 5. In some embodiments, e is 0. In some embodiments, e is 1. In some embodiments, e is 2. In some embodiments, e is 3. In some embodiments, e is 4. In some embodiments, e is 5.

In some embodiments, a compound of formula II-a is selected from

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

According to one embodiment, the present disclosure provides a compound of formula I having the structure of formula III:

or a pharmaceutically acceptable salt thereof, wherein:

Ring C″ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R¹, R²and R³is independently halogen, R′, —C(O)R′, —C(S)R′, —CO₂R′, —C(O)N(R′)₂, —C(S)N(R′)₂, —S(O)R′, —SO₂R′, —SO₂N(R′)₂, —OR′, —O—(C_1-6aliphatic)-N(R′)₂, —O—(C_1-6aliphatic)-OR′, —OC(O)R′, —SR′, —NO₂, —N(R′)₂, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′;
a is 1-4;
b is 1-5;
X¹is —C(R^x)₂—, —NR^x—, —NR^xC(R^x)₂— or —OC(R^x)₂—;
X²is —C(R^x)₂— or —NR^x—;
each R^xis independently R′, —(C_1-6aliphatic)-N(R′)₂, or —(C_1-6aliphatic)-OR′;
each R′ is independently —R, —C(O)R, —CO₂R, or —SO₂R, or:
- two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and
each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ring C″ is optionally substituted phenyl. In some embodiments, Ring C″ is substituted phenyl. In some embodiments, Ring C″ is phenyl. In some embodiments, Ring C″ is phenyl substituted with one or more halogen atoms. In some embodiments, Ring C″ is phenyl substituted with two halogen atoms. In some embodiments, Ring C″ is 2-fluoro-5-chlorophenyl. In some embodiments, Ring C″ is 2-fluoro-5-bromophenyl. In some embodiments, Ring C″ is 3-chloro-4-flluorophenyl.

In some embodiments, Ring C″ is an optionally substituted 8-10 membered bicyclic aryl ring.

In some embodiments, Ring C″ is an optionally substituted 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring C″ is unsubstituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In some embodiments, Ring C″ is substituted 5 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen or sulfur. In certain embodiments, Ring C″ is an optionally substituted 5-membered heteroaryl ring having 1 nitrogen atom, and an additional heteroatom selected from sulfur or oxygen. Exemplary Ring C″ groups include optionally substituted pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl or isoxazolyl.

In some embodiments, Ring C″ is a 6-membered heteroaryl ring having 1-3 nitrogen atoms. In other embodiments, Ring C″ is an optionally substituted 6-membered heteroaryl ring having 1-2 nitrogen atoms. In some embodiments, Ring C″ is an optionally substituted 6-membered heteroaryl ring having 2 nitrogen atoms. In certain embodiments, Ring C″ is an optionally substituted 6-membered heteroaryl ring having 1 nitrogen. Exemplary Ring C″ groups include optionally substituted pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, or tetrazinyl. In some embodiments, Ring C″ is optionally substituted pyridinyl.

In certain embodiments, Ring C″ is an optionally substituted 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted 5,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring C″ is an optionally substituted 5,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In certain embodiments, Ring C″ is an optionally substituted 5,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted indolyl. In some embodiments, Ring C″ is an optionally substituted benzofuranyl. In some embodiments, Ring C″ is an optionally substituted azabicyclo[3.2.1]octanyl. In certain embodiments, Ring C″ is an optionally substituted 5,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted azaindolyl. In some embodiments, Ring C″ is an optionally substituted benzimidazolyl. In some embodiments, Ring C″ is an optionally substituted benzothiazolyl. In some embodiments, Ring C″ is an optionally substituted benzoxazolyl. In some embodiments, Ring C″ is an optionally substituted indazolyl. In certain embodiments, Ring C″ is an optionally substituted 5,6-fused heteroaryl ring having 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, Ring C″ is an optionally substituted 6,6-fused heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted 6,6-fused heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In other embodiments, Ring C″ is an optionally substituted 6,6-fused heteroaryl ring having 1 heteroatom independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is an optionally substituted quinolinyl. In some embodiments, Ring C″ is an optionally substituted isoquinolinyl. According to one aspect, Ring C″ is an optionally substituted 6,6-fused heteroaryl ring having 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, Ring C″ is a quinazoline or a quinoxaline.

As generally defined above, each R¹is independently halogen, R′, —C(O)R′, —C(S)R′, —CO2R′, —C(O)N(R′)2, —C(S)N(R′)2, —S(O)R′, —SO2R′, —SO2N(R′)2, —OR′, —O—(C1-6 aliphatic)-N(R′)₂, —O—(C_1-6aliphatic)-OR′, —OC(O)R′, —SR′, —NO₂, —N(R′)₂, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′, wherein each R′ is independently as defined above and described herein.

In some embodiments, R¹is —OR′, wherein R′ is as defined above and described herein. In some embodiments, R¹is OR, wherein R is as defined above and described herein. In some embodiments, R¹is —OMe.

In some embodiments, R¹is —O—(C_1-6aliphatic)-OR′, wherein R′ is as defined above and described herein. In some embodiments, R¹is —O—(C_1-6aliphatic)-OR, wherein R is as defined above and described herein. In some embodiments, R¹is —O—(C1-6 aliphatic)-OH. In some embodiments, R¹is —O(CH2)2OH. In some embodiments, R¹is —O—(C_1-6aliphatic)-OR, wherein R is C_1-6alkyl. In some embodiments, R¹is —O(CH₂)₂OMe.

In some embodiments, R¹is —O—(C_1-6aliphatic)-N(R′)₂, wherein each R′ is independently as defined above and described herein. In some embodiments, R¹is —O—(C_1-6aliphatic)-N(R′)₂, wherein two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur. In some embodiments, R¹is —O—(C_1-6aliphatic)-N(R)₂, wherein each R is independently C_1-6alkyl. In some embodiments, R¹is —O(CH₂)₂N(R′)₂, wherein each R′ is independently C_1-6alkyl. In some embodiments, R¹is —O(CH₂)₂N(R′)₂, wherein two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur. In some embodiments, R¹is

As generally defined above, each R²is independently halogen, R′, —C(O)R′, —C(S)R′, —CO₂R′, —C(O)N(R′)₂, —C(S)N(R′)₂, —S(O)R′, —SO₂R′, —SO₂N(R′)₂, —OR′, —O—(C_1-6aliphatic)-N(R′)2, —O—(C1-6 aliphatic)-OR′, —OC(O)R′, —SR′, —NO2, —N(R′)2, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′, wherein each R′ is independently as defined above and described herein.

In some embodiments, R²is halogen. In some embodiments, R²is —F. In some embodiments, R²is —Cl. In some embodiments, R²is —Br. In some embodiments, R²is —I.

As generally defined above, each R³is independently halogen, R′, —C(O)R′, —C(S)R′, —CO₂R′, —C(O)N(R′)₂, —C(S)N(R′)₂, —S(O)R′, —SO₂R′, —SO₂N(R′)₂, —OR′, —O—(C_1-6aliphatic)-N(R′)₂, —O—(C_1-6aliphatic)-OR′, —OC(O)R′, —SR′, —NO₂, —N(R′)₂, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)₂, —NR′SO₂R′, —NR′SO₂N(R′)₂, or —NR′OR′, wherein each R′ is independently as defined above and described herein.

In some embodiments, R³is hydrogen.

As generally defined above, a is 1-4. In some embodiments, a is 1. In some embodiments, a is 2. In some embodiments, a is 4. In some embodiments, a is 4.

In some embodiments, a=3 and each R¹is —OMe.

As generally defined above, b is 1-5. In some embodiments, b is 1. In some embodiments, b is 2. In some embodiments, b is 3. In some embodiments, b is 4. In some embodiments, b is 5.

As generally defined above, X¹is —C(R^x)₂—, —NR^x—, —NR^xC(R^x)₂— or —OC(R^x)₂—, wherein each R^Xis independently as defined above and described herein. In some embodiments, X¹is —C(R^x)₂—, wherein each R^xis independently as defined above and described herein. In some embodiments, X¹is —CH₂—. In some embodiments, X¹is —NR^x—, wherein R′ is as defined above and described herein. In some embodiments, X¹is —NH—. In some embodiments, X¹is —NR^xC(R^x)₂—, wherein R′ is independently as defined above and described herein. In some embodiments, X¹is —NHCH₂—. In some embodiments, R′ is —OC(R^x)₂—, wherein R′ is independently as defined above and described herein. In some embodiments, R′ is —OCH₂—.

In some embodiments, X¹is —NR′—, wherein R′ is as defined above and described herein. In some embodiments, X¹is —NR′—, wherein R′ is optionally substituted C_1-6alkyl. In some embodiments, X¹is —NR′—, wherein R′ is unsubstituted C_1-6alkyl. In some embodiments, X¹is —NR′— wherein R′ is methyl. In some embodiments, X¹is —NR′— wherein R′ is propyl. In some embodiments, X¹is —NR′— wherein R′ is n-propyl. In some embodiments, X¹is —NR′—, wherein R′ is methyl. In some embodiments, X¹is —NR′—, wherein R′ is substituted C_1-6alkyl.

In some embodiments, X¹is —NR^x—, wherein R^xis wherein R^xis —(C_1-6aliphatic)-N(R′)₂, wherein each R′ is independently as defined above and described herein. In some embodiments, —NR^x— is —(CH₂)_1-6N(R′)₂, wherein each R′ is independently as defined above and described herein. In some embodiments, —NR^x— is —(CH₂)_1-6N(R′)₂, wherein each R′ is optionally substituted C_1-6alkyl. In some embodiments, —NR^x— is —(CH₂)₂N(R′)₂, wherein each R′ is optionally substituted C_1-6alkyl. In some embodiments, X¹is —N[(CH₂)₂N(CH₃)₂]—.

As generally defined above, X²is —C(R^x)₂— or —NR^x—, wherein each R^xis independently as defined above and described herein. In some embodiments, X²is —C(R′)₂—, wherein each R′ is independently as defined above and described herein. In some embodiments, X²is —CH₂—. In some embodiments, X²is —NR′—, wherein R′ is as defined above and described herein. In some embodiments, X²is —NH—.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-a:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein. In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-b:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-c:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-d:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-e:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-f:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

In some embodiments, the present disclosure provides a compound of formula III having the structure of formula III-g:

or a pharmaceutically acceptable salt thereof, wherein each variable is independently as defined above and described herein.

Exemplary compounds are set forth in Table 1, below.

TABLE 1 Exemplary Compounds 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136

In some embodiments, the present disclosure provides a compound depicted in Table 1, above, or a pharmaceutically acceptable salt thereof.

4. General Methods of Providing the Present Compounds

The compounds of this disclosure may be prepared or isolated in general by synthetic and/or semi-synthetic methods known to those skilled in the art for analogous compounds.

Pharmaceutically Acceptable Compositions

It will be appreciated that certain of the compounds of present disclosure can exist in free form for treatment, or where appropriate, as a pharmaceutically acceptable salt thereof.

As used herein, the term “pharmaceutically acceptable salt” refers to those salts which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. A “pharmaceutically acceptable salt” means any non-toxic salt or salt of an ester of a compound of this disclosure that, upon administration to a recipient, is capable of providing, either directly or indirectly, a compound of this disclosure or a pharmaceutically active metabolite or residue thereof. As used herein, the term “pharmaceutically active metabolite or residue thereof” means that a metabolite or residue thereof is also a pharmaceutically active compound in accordance with the present disclosure.

Pharmaceutically acceptable salts are well known in the art. For example, S. M. Berge et al., describes pharmaceutically acceptable salts in detail in J. Pharmaceutical Sciences, 1977, 66, 1-19, incorporated herein by reference to the extent it is consistent herewith. Pharmaceutically acceptable salts of the compounds of this disclosure include those derived from suitable inorganic and organic acids and bases. Examples of pharmaceutically acceptable, nontoxic acid addition salts are salts of an amino group formed with inorganic acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid and perchloric acid or with organic acids such as acetic acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid or malonic acid or by using other methods used in the art such as ion exchange. Other pharmaceutically acceptable salts include adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Salts derived from appropriate bases include alkali metal, alkaline earth metal, ammonium and N⁺(C1-4 alkyl)4 salts. This disclosure also envisions the quaternization of any basic nitrogen-containing groups of the compounds disclosed herein. Water or oil-soluble or dispersable products may be obtained by such quaternization. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further pharmaceutically acceptable salts include, when appropriate, nontoxic ammonium, quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulfate, phosphate, nitrate, loweralkyl sulfonate and aryl sulfonate.

In some cases, compounds of the present disclosure may contain one or more acidic functional groups and, thus, may be capable of forming pharmaceutically-acceptable salts with pharmaceutically-acceptable bases. The term “pharmaceutically-acceptable salts” in these instances refers to the relatively non-toxic, inorganic and organic base addition salts of compounds of the present disclosure. These salts can likewise be prepared in situ in the administration vehicle or the dosage form manufacturing process, or by separately reacting the purified compound in its free acid form with a suitable base, such as the hydroxide, carbonate or bicarbonate of a pharmaceutically-acceptable metal cation, with ammonia, or with a pharmaceutically-acceptable organic primary, secondary or tertiary amine. Representative alkali or alkaline earth salts include the lithium, sodium, potassium, calcium, magnesium, and aluminum salts and the like. Representative organic amines useful for the formation of base addition salts include ethylamine, diethylamine, ethyldiamine, ethanolamine, diethanolamine, piperazine and the like.

According to another aspect of the present disclosure, pharmaceutically acceptable compositions are provided, wherein these compositions comprise any of the compounds as described herein, and optionally comprise a pharmaceutically acceptable carrier, adjuvant or vehicle, which, as used herein, includes any and all solvents, diluents, or other liquid vehicle, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like, as suited to the particular dosage form desired.

Remington's Pharmaceutical Sciences, Sixteenth Edition, E. W. Martin (Mack Publishing Co., Easton, Pa., 1980) discloses various carriers used in formulating pharmaceutically acceptable compositions and known techniques for the preparation thereof. Except insofar as any conventional carrier medium is incompatible with the compounds of the disclosure, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the pharmaceutically acceptable composition, its use is contemplated to be within the scope of this disclosure. Some examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, ion exchangers, alumina, aluminum stearate, lecithin, serum proteins, such as human serum albumin, buffer substances such as phosphates, glycine, sorbic acid, or potassium sorbate, partial glyceride mixtures of saturated vegetable fatty acids, water, salts or electrolytes, such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, zinc salts, colloidal silica, magnesium trisilicate, polyvinyl pyrrolidone, polyacrylates, waxes, polyethyl-polyoxypropyl-block polymers, wool fat, sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients such as cocoa butter and suppository waxes; oils such as peanut oil, cottonseed oil; safflower oil; sesame oil; olive oil; corn oil and soybean oil; glycols; such a propyl glycol or polyethyl glycol; esters such as ethyl oleate and ethyl laurate; agar; buffering agents such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol, and phosphate buffer solutions, as well as other non-toxic compatible lubricants such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, releasing agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the composition, according to the judgment of the formulator. In some embodiments, the compositions of the present disclosure additionally comprise one or more of DMSO, PEG400, Tween-80, and hydropropyl beta cyclodextrin. In some embodiments, the compositions of the present disclosure additionally comprise 2% DMSO, 2% PEG400, 0.2% Tween80, and 20% hydropropyl beta cyclodextrin.

The compositions provided by the present disclosure can be employed in combination therapies, meaning that the present compositions can be administered concurrently with, prior to, or subsequent to, one or more other desired therapeutic agents or medical procedures. The particular combination of therapies (therapeutic agents or procedures) to employ in a combination regimen will take into account compatibility of the desired therapeutic agents and/or procedures and the desired therapeutic effect to be achieved. It will also be appreciated that the therapies employed may achieve a desired effect for the same disorder (for example, a compound described herein may be administered concurrently with another therapeutic agent used to treat the same disorder), or they may achieve different effects (e.g., control of any adverse effects).

The amount of additional therapeutic agent present in the compositions of this disclosure will be no more than the amount that would normally be administered in a composition comprising that therapeutic agent as the only active agent. In certain embodiments, the amount of additional therapeutic agent in the present compositions will range from about 50% to 100% of the amount normally present in a composition comprising that agent as the only therapeutically active agent.

In an alternate embodiment, the methods of this disclosure that utilize compositions that do not contain an additional therapeutic agent, comprise the additional step of separately administering to said patient an additional therapeutic agent. When these additional therapeutic agents are administered separately they may be administered to the patient prior to, sequentially with or following administration of the compositions of this disclosure.

The pharmaceutically acceptable compositions of this disclosure can be administered to humans and other animals orally, rectally, parenterally, intravenously, intracisternally, intravaginally, intraperitoneally, topically (as by powders, ointments, or drops), bucally, as an oral or nasal spray, or the like, depending on the severity of the disorder being treated.

Liquid dosage forms for oral administration include, but are not limited to, pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. In addition to the active compounds, the liquid dosage forms may contain inert diluents commonly used in the art such as, for example, water or other solvents, solubilizing agents and emulsifiers such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propyl glycol, 1,3-butyl glycol, dimethylformamide, oils (in particular, cottonseed, groundnut, corn, germ, olive, castor, and sesame oils), glycerol, tetrahydrofurfuryl alcohol, polyethyl glycols and fatty acid esters of sorbitan, and mixtures thereof. Besides inert diluents, the oral compositions can also include adjuvants such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, and perfuming agents.

Injectable preparations, for example, sterile injectable aqueous or oleaginous suspensions may be formulated according to the known art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation may also be a sterile injectable solution, suspension or emulsion in a nontoxic parenterally acceptable diluent or solvent, for example, as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution, U.S.P. and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil can be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid are used in the preparation of injectables.

The injectable formulations can be sterilized, for example, by filtration through a bacterial-retaining filter, or by incorporating sterilizing agents in the form of sterile solid compositions which can be dissolved or dispersed in sterile water or other sterile injectable medium prior to use.

In order to prolong the effect of a compound of the present disclosure, it is often desirable to slow the absorption of the compound from subcutaneous or intramuscular injection. This may be accomplished by the use of a liquid suspension of crystalline or amorphous material with poor water solubility. The rate of absorption of the compound then depends upon its rate of dissolution that, in turn, may depend upon crystal size and crystalline form. Alternatively, delayed absorption of a parenterally administered compound form is accomplished by dissolving or suspending the compound in an oil vehicle. Injectable depot forms are made by forming microencapsule matrices of the compound in biodegradable polymers such as polylactide-polyglycolide. Depending upon the ratio of compound to polymer and the nature of the particular polymer employed, the rate of compound release can be controlled. Examples of other biodegradable polymers include poly(orthoesters) and poly(anhydrides). Depot injectable formulations are also prepared by entrapping the compound in liposomes or microemulsions that are compatible with body tissues.

Compositions for rectal or vaginal administration are preferably suppositories which can be prepared by mixing the compounds of this disclosure with suitable non-irritating excipients or carriers such as cocoa butter, polyethyl glycol or a suppository wax which are solid at ambient temperature but liquid at body temperature and therefore melt in the rectum or vaginal cavity and release the active compound.

Solid dosage forms for oral administration include capsules, tablets, pills, powders, and granules. In such solid dosage forms, the active compound is mixed with one or more inert, pharmaceutically acceptable excipient or carrier such as sodium citrate or dicalcium phosphate and/or a) fillers or extenders such as starches, lactose, sucrose, glucose, mannitol, and silicic acid, b) binders such as, for example, carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidinone, sucrose, and acacia, c) humectants such as glycerol, d) disintegrating agents such as agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and sodium carbonate, e) solution retarding agents such as paraffin, f) absorption accelerators such as quaternary ammonium compounds, g) wetting agents such as, for example, cetyl alcohol and glycerol monostearate, h) absorbents such as kaolin and bentonite clay, and i) lubricants such as talc, calcium stearate, magnesium stearate, solid polyethyl glycols, sodium lauryl sulfate, and mixtures thereof. In the case of capsules, tablets and pills, the dosage form may also comprise buffering agents.

Solid compositions of a similar type may also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polyethyl glycols and the like. The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings and other coatings well known in the pharmaceutical formulating art. They may optionally contain opacifying agents and can also be of a composition that they release the active ingredient(s) only, or preferentially, in a certain part of the intestinal tract, optionally, in a delayed manner. Examples of embedding compositions that can be used include polymeric substances and waxes. Solid compositions of a similar type may also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polyethyl glycols and the like.

The active compounds can also be in micro-encapsulated form with one or more excipients as noted above. The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings, release controlling coatings and other coatings well known in the pharmaceutical formulating art. In such solid dosage forms, the active compound may be admixed with one or more inert diluent such as sucrose, lactose or starch. Such dosage forms may also comprise, as is normal practice, additional substances other than inert diluents, e.g., tableting lubricants and other tableting aids such a magnesium stearate and microcrystalline cellulose. In the case of capsules, tablets and pills, the dosage forms may also comprise buffering agents. They may optionally contain opacifying agents and can also be of a composition that they release the active ingredient(s) only, or preferentially, in a certain part of the intestinal tract, optionally, in a delayed manner. Examples of embedding compositions that can be used include polymeric substances and waxes.

Dosage forms for topical or transdermal administration of a compound of this disclosure include ointments, pastes, creams, lotions, gels, powders, solutions, sprays, inhalants or patches. The active component is admixed under sterile conditions with a pharmaceutically acceptable carrier and any needed preservatives or buffers as may be required. Ophthalmic formulation, ear drops, and eye drops are also contemplated as being within the scope of this disclosure. Additionally, the present disclosure contemplates the use of transdermal patches, which have the added advantage of providing controlled delivery of a compound to the body. Such dosage forms can be made by dissolving or dispensing the compound in the proper medium. Absorption enhancers can also be used to increase the flux of the compound across the skin. The rate can be controlled by either providing a rate controlling membrane or by dispersing the compound in a polymer matrix or gel.

Uses of Compounds and Pharmaceutically Acceptable Compositions

The compounds of the disclosure are preferably formulated in dosage unit form for ease of administration and uniformity of dosage. The expression “dosage unit form” as used herein refers to a physically discrete unit of agent appropriate for the patient to be treated. It will be understood, however, that the total daily usage of the compounds and compositions of the present disclosure (also referred to herein as “therapeutically effective amount”) will be decided by the attending physician within the scope of sound medical judgment. More particularly, as used herein, the phrase “therapeutically effective amount” of the compound used in the methods of the present disclosure refers to a sufficient amount of a compound to treat SMA as defined herein, at a reasonable benefit/risk ratio applicable to any medical treatment. It can be understood, however, that the total daily usage of the compound and pharmaceutically acceptable compositions including the compound for use in the methods of the present disclosure can be decided by the attending physician within the scope of sound medical judgment. The specific therapeutically effective dose level for any particular patient can depend upon a variety of factors including the loss of motor neuron function episode being treated and the severity of the episode; activity of the specific compound employed; the specific pharmaceutically acceptable composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and rate of excretion of the compound employed; the duration of the treatment; drugs used in combination or coincidental with the specific compound employed; and like factors well-known in the medical arts. For example, it is well within the skill of the art to start doses of the compound at levels lower than required to achieve the desired therapeutic effect and to gradually increase the dosage until the desired effect is achieved.

In certain embodiments, the compounds of the disclosure may be administered orally or parenterally at dosage levels of about 0.01 mg/kg to about 50 mg/kg and preferably from about 1 mg/kg to about 25 mg/kg, of subject body weight per day, one or more times a day, to obtain the desired therapeutic effect.

The term “patient,” as used herein, means an animal, preferably a mammal, and most preferably a human. Particularly, the patient refers to a subject that is susceptible to or has SMA. As used herein, “susceptible to” refers to having little resistance to a certain disease, disorder or condition, and in particular, to SMA, including being genetically predisposed, having a family history of, and/or having symptoms of the disease, disorder or condition. Accordingly, in some embodiments, the compounds and/or pharmaceutically acceptable compositions can be administered to a subset of subjects in need of preventing/minimizing/controlling loss of motor neuron function, progressive motor weakness, muscle wasting, and paralysis. Some subjects that are in specific need of restored/maintained motor neuron function may include patients who are susceptible to, or at elevated risk of, experiencing loss of motor neuron function, including subjects susceptible to, or at elevated risk of, areflexia, muscle weakness, poor muscle tone, muscle wasting, paralysis, fasciculations of the tongue, difficulty sucking or swallowing, arthrogryposis, low weight, and the like. In one particular embodiment, the methods can be administered to a patient who has, or is susceptible to, or at elevated risk of, SMA. Subjects may be susceptible to, or at elevated risk of, experiencing SMA, and generally, loss of motor neuron function, areflexia, muscle weakness, poor muscle tone, muscle wasting, paralysis, fasciculations of the tongue, difficulty sucking or swallowing, arthrogryposis, low weight due to family history, age, environment, and/or lifestyle. Based on the foregoing, because some of the method embodiments of the present disclosure are directed to specific subsets or subclasses of identified subjects (that is, the subset or subclass of patients susceptible to one or more specific conditions noted herein), not all subjects will fall within the subset or subclass of subjects as described herein for certain diseases, disorders or conditions.

Various functions and advantages of these and other embodiments of the present disclosure will be more fully understood from the examples described below. The following examples are intended to illustrate the benefits of the present disclosure, but do not exemplify the full scope of the disclosure.

EXAMPLES Example 1

In this Example, the assay method of the present disclosure was utilized to identify compounds that increase SMN2 expression.

Materials and Methods Cloning

The luciferase minigene from previous reporter vectors SMN1-luc (T-luc) or SMN2-luc (C-luc) was shortened by digestion with Sma I and Swa I to remove 2 kB from intron 6. The SMN exon 1-5 fragment was generated by PCR from human cDNA (exon 1 forward: ccacaaatgtgggagggcgataacc (SEQ ID NO: 1) and exon 6 reverse: tatctcgagtggtccagaaggaaatggaggcagcc (SEQ ID NO: 2)). The SMN promoter elements were from p3.4^Tand p3.4^CSMN (Monani et al., Promoter analysis of the human centromeric and telomeric survival motor neuron genes (SMNC and SMNT), Biochim Biophys Acta 1999, 1445 (3), 330-336). These were combined into pIRES cloning vector (BD Clontech) at the multiple cloning site. The entire reporter fragment was excised from pIRES and ligated into a pCEP4 (Invitrogen) plasmid that also expressed renilla luciferase from nucleotides 299-1259 of phRL-null (Promega) from the CMV promoter.

Cell Culture

Cells were incubated at 37° C. with 5% CO2. HEK-293 cells were cultured in D-MEM (GIBCO 11995) with 10% fetal bovine serum (FBS, ATLAS) and 1× pen-strep (GIBCO 15140). Reporter cell lines containing SMN1, SMN2, or control luciferase reporter were selected and maintained in D-MEM with 10% FBS and 1× pen-strep with 200 μg/mL hygromycin B (Invitrogen 10687-010). 3813 and 3814 fibroblasts were cultured in D-MEM (GIBCO 11995) with 15% fetal bovine serum (FBS, ATLAS) and 1× pen-strep (GIBCO 15140).

Luciferase Reporter Assay

The reporter cell lines were plated at 50,000 cells per well in 96-well plates and incubated overnight. Compounds were added to each well and incubated at 37° C. overnight. The final DMSO concentration was 0.1%. Luciferase activity was assayed using either STEADYGLO (PROMEGA E2510) or DUALGLO (PROMEGA E2920) luciferase using the WALLAC ENVISION multilabel reader. For detailed assay conditions see Table 2A. All data points were transformed from CPS to percent increase over basal expression in the treated control wells (DMSO or H2O as appropriate).

Protein Detection

For analysis of SMN-luciferase fusion, cells were treated with compound or DMSO for 25 hours. Cells were lysed with protein lysis buffer (100 mM Tris pH 8.0, 100 mM NaCl, 0.1% NP-40, 8.0 M urea, and protease inhibitor). Each sample was separated on a 10% SDS-page gel, transferred to Immobilon-P membrane (MILLIPORE IVPH00010) and blotted for the SMN-luciferase fusion with anti-luciferase antibody (PROMEGA, #G7541), SMN with the 4f11 mouse monoclonal antibody (described in Mattis et al., “Detection of human survival motor neuron (SMN) protein in mice containing the SMN2 transgene: Applicability to preclinical therapy development for spinal muscular atrophy” J. Neurosci Methods, 2008), HA-tag with 12CA5 monoclonal, actin (Sigma A2066) or a-tubulin (DM1a; Sigma T6199).

For detection of SMN protein in patient fibroblasts, 8,000 cells per cm were plated 24 hours prior to drug addition. Fresh media and compound were added every 24 hours. After 72 hours, cells were harvested, washed with cold PBS, and lysed as above. It has been determined that 10 μg total protein per lane is within the linear range for immunoblot detection of SMN and a-tubulin. Western blots were probed for SMN with the 4f11 mouse monoclonal antibody and a-tubulin.

Quantification of protein was performed with FUJIFILM LAS-4000 Multifunctional Imaging System. The signal intensity was measured for each band on an immunoblot, normalized to the loading control, and the fold increase was determined in relation to the appropriate DMSO treated control.

Overexpression Assays

Cells were plated at a density of 2×10⁶per 60 cm dish and incubated overnight. Cells were transfected with up to 6 g of HA-tagged expression vector using FUGENE 6 at a 3:1 fugene:DNA ratio and incubated overnight. After 24 hours cells were re-plated at 1×10⁵cells per well in a 96-well plate or 1×10⁶cells per well in 6-well dishes. Cells were tested 24 to 48 hours later. Luciferase was assayed using DUALGLO luciferase as described above. Protein lysates and RNA samples were collected using protein lysis buffer or Trizol respectively. Protein was analyzed by western blot and RNA was analyzed by qRT-PCR.

PCR and RT-PCR

Compounds were tested at three concentrations that display maximal activity in the luciferase assay. Cells were treated as described above for the luciferase assay. Cells were harvested by trypsinization, neutralized with trypsin inhibitor, and washed. RNA was isolated from the cells using TRIZOL Reagent (Invitrogen 15596-026). cDNA was generated using the IMPROM-II Reverse Transcription System (Promega A3801).

The forward primer pair recognizes the exon 5-6 junction, which includes a restriction site that was engineered into the reporter and will exclude amplification of endogenous SMN mRNA. The reverse primers recognize either exon 7 or luciferase for detection of full-length or total SMN-luciferase transcripts respectively. For a reference control, cDNA from the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was amplified. The primers used include SMN exon5-forward (catttccttctggaccactcgag) (SEQ ID NO: 3), luciferase-reverse (atagcttctgccaaccgaacgg) (SEQ ID NO: 4), exon7-reverse (taaggaatgtgagcaccttccttc) (SEQ ID NO: 5), GAPDH-reverse (G3A) (tccaccaccctgttgctgta) (SEQ ID NO: 6) and GAPDH-forward (G3S) (accacagtccatgccatcac) (SEQ ID NO: 7). qPCR was performed as described in the protocol for iQ SYBRGREEN SUPERMIX (Biorad 170-8882) using an EPPENDORF Mastercycler ep realplex⁴Thermo Cycler. Reactions were incubated for a 10 minute, 94° C. hot start followed by 45 cycles of the following: 94° C. for 45 second, 60° C. for 15 seconds, 72° C. for 45 seconds. Melting curves for each reaction were obtained. Each sample was assayed in triplicate and every plate contained a 5-point cDNA dilution course to calculate amplification efficiency for each primer pair. The Pfaffl method was used to determine the change in transcript levels relative to the DMSO and normalized to GAPDH (Pfaffl, M. W., “A new mathematical model for relative quantification in real-time RT-PCR,” Nucleic Acids Res 2001, 29(9), 3e45).

Screening Protocol

Cells were plated in phenol red-free D-MEM (Gibco 21063) with sodium pyruvate (Gibco 11360) and 10% FBS in the absence of hygromycin B and pen-strep and allowed to adhere 1 hour prior to addition of compound. Each compound was added to a single well with a BECKMAN COULTER BIOMEK FX 384 to a final concentration of approximately 2 M from compound stocks, based on an average molecular weight of 500. The final DMSO concentration in test and control wells was 0.13%. Plates were sealed with porous paper tape and incubated for 24 hours. Luciferase expression was measured using the STEADYLITE luciferase (Perkin Elmer 6016981) substrate and the LJL Analyst HT, and read for counts per second (CPS) at an integration time of 100,000 μS. For comparison, data points were transformed from CPS to percent activation over basal expression in the DMSO treated control wells. This is summarized in Table 2B.

Library Composition

A compound library of approximately 115,000 small molecules, including compounds approved by the Food and Drug Administration (FDA), a purified natural products library, compounds purchased from PEAKDALE (High Peak, UK), MAYBRIDGE Plc. (Cornwall, UK), Cerep (Paris, France), BIONET RESEARCH Ltd. (Cornwall, UK), PRESTWICK (Ilkirch, France), SPECS and BIOSPECS (CP Rijswijk, the Netherlands), ENAMINE (Kiev, Ukraine), I.F. Lab LTD (Burlington, Canada), and Chemical Diversity Labs (San Diego, Calif.), and small molecules from academic institutions was tested. Compounds were selected from vendors by applying a series of filters including clogP and predicted solubility. All of the small molecules generally adhere to Lipinski's rules (Lipinski et al. “Experimental and computational approaches to estimate solubility and permeability in drug discover and development settings,” Adv Drug Deliv Rev 2001, 46(1-3), 3-26) and contain a low proportion of known toxicophores (i.e. Michael acceptors and alkylating agents) and unwanted functionalities (i.e. imines, thiols, and quarternary amines) and have been optimized for molecular diversity. Compound source plates for the assay were prepared by spotting 0.4 μl of 1.67 mM compound in DMSO in each well of a Greiner 384-well plate, with columns 23 and 24 spotted with neat DMSO for positive and negative controls. These were then sealed with aluminum plate seals and stored at −20° C.

Results Development of a New Reporter

Over time, the original C33a reporter cell lines displayed a decrease in the difference in luciferase signal from SMN1 and SMN2 (FIG. 7) and showed inconsistent responses to treatment with drugs known to increase SMN expression (data not shown). These original reporters were also driven by the CMV promoter and displayed much higher basal levels of SMN1- and SMN2-luciferase activity in the absence of treatment (FIG. 7), which could diminish the reporters' ability to detect compounds that are less potent and more selective. To address this, a new reporter assay was designed that would be more responsive to molecular cues that regulate the levels of SMN expression through multiple pathways. The SMN promoter and exon 7 splicing cassette were combined into a single construct to simultaneously identify compounds that increase SMN transcription or exon 7 inclusion (FIGS. 1A-1D). The presence of the native SMN promoter may also influence recruitment of splicing factors to the transcript and better reproduce the context in which the endogenous gene is processed and expressed. Since a subset of compounds might stabilize the SMN RNA or protein, for example, by interfering with its metabolism or ubiquitination, exons 1-5 were included in the new reporter. This reporter produces a full-length SMN-luciferase fusion protein that should be regulated and metabolized in a manner that is more consistent with the endogenous SMN protein. The entire reporter was cloned into an Epstein Barr Virus (EBV) vector that is maintained autonomously as stable episomes in some human cell lines.

To summarize, the new assay design: i) replaced the CMV promoter with 3.4 kb of the SMN1 or SMN2 promoters with an intact transcription start site; ii) included the cDNA for exons 1-5 following the authentic promoter and translational ATG; iii) deleted a portion of intron 6 since the size of the entire 6 kb intron complicated cloning; iv) included the exon 7 splicing cassette with the firefly luciferase reporter; v) cloned renilla luciferase expressed from the CMV promoter into the construct for monitoring copy number, cell viability and specificity of the transcriptional effects; and vi) transferred the 9 kb reporter SMN1 and SMN2 cassettes into EBV ori based pCEP4. The result is reporters with sequences from SMN1 and SMN2 in the context of their respective promoters. These constructs, each ˜19 kb, will produce increased SMN-luciferase fusion protein if there is an induction of 1) transcription from the SMN promoter; 2) inclusion of exon 7; or 3) stabilization of the SMN-luciferase mRNA or fusion protein. Not only will this reporter be able to identify potential positive modifiers of SMN expression, but the design of the screen and the renilla control also reduces the likelihood of selecting compounds that are toxic or cause non-specific increases in transcription. These reporters were transfected into HEK 293 cells. These human cells are easy to culture and expand, highly transfectable, and maintain EBV based plasmids extrachromosomally. Stable clonal cell lines were isolated that express the full-length SMN-luciferase protein as appropriate in both the SMN1-luc or SMN2-luc reporters.

Analysis of SMN1-Luc and SMN2-Luc Clonal Cell Lines Population

Luciferase expression was analyzed in the stable HEK293 cell lines containing the SMN1- and SMN2-luciferase reporters. In the initial stable mixed cell populations, mixed SMN1-luc cells displayed 30% more luciferase activity than the mixed SMN2-luc cells. A pair of clonal cell lines was isolated, clonal SMN1-luc and clonal-SMN2-luc, in which the clonal-SMN1-luc cell line has 50-fold higher luciferase activity when compared to clonal-SMN2-luc cell line (FIG. 2A). This range of expression provides a large window for potential activation of SMN2 expression with drug treatment. Since these reporters were designed for use in either high or low throughput screens, the dynamic range of activation is very important. The selection of SMN2-luc clones that maintain low levels of basal SMN-luciferase expression was instrumental in establishing this range of activation and was a dramatic improvement over not only the original C33a based reporter cell lines but also the mix population HEK293 SMN1-luc and SMN2-luc cell lines (FIG. 7).

Expression of the SMN-luciferase protein fusion was confirmed by western blot (FIG. 2B). All cells express endogenous SMN (38 kD) but only the SMN1-luc cell line expresses detectable levels of the SMN-luciferase fusion protein. The SMN-luciferase fusion protein could only be detected in the SMN2-luc cell line upon induction with compounds that increase SMN expression (SAHA and sodium butyrate in FIG. 3B).

These clonal cell lines display the expected patterns of exon 7 inclusion in the reporter transcripts for both the SMN1-luc and SMN2-luc cell lines. Published studies have determined that 90% of transcripts from SMN1 include exon 7, while only 10-20% of transcripts from SMN2 include exon 7. In FIG. 2C, end-point RT-PCR for each cell line is shown and inclusion of exon 7 was calculated as 64% for SMN1-luc and 13% for SMN2-luc. By quantitative reverse transcription-PCR (qRT-PCR) using the primers illustrated in FIG. 4A, the percent inclusion for transcripts in each reporter was calculated more precisely; 95.1%±6.7 for SMN1-luc and 10.2%±0.9 for SMN2-luc. Using these primers, the number of copies of each reporter in these clonal cell lines was estimated. SMN1-luc has 1 copy of the episomal reporter per cell and the SMN2-luc cell line has about 10 copies of the reporter per cell.

To determine the half-life of the SMN-fusion protein in these cell lines, cells were treated with cycloheximide and assayed for residual luciferase activity for 24 hours. The luciferase activity in the SMN2-luc cell line had a t_1/2of 3.2 hours (FIG. 2D). This matches well with published data for endogenous SMN protein. This data suggests that any changes in protein stability for the SMN-luciferase fusion protein would be easily detected within 24 to 48 hours.

When the cell-lines were tested for tolerance to DMSO, it was found the luciferase expression was virtually unchanged when the final DMSO concentration in the reaction ranged from 0-1%. Concentrations above 1% decreased luciferase activity and were very likely detrimental to cell viability. Compounds are routinely screened at a final DMSO concentration equal to or less than 0.1%. Basal activity and response to compounds did not vary with serial cell passage and was very reproducible after the clones were thawed from liquid nitrogen storage.

SMN-Luciferase Reporter Cell Response to Compound Treatment.

In this assay, cells were treated with compounds previously shown to increase SMN2 protein levels and luciferase expression read for counts per second (CPS) at an integration time of 100,000 μS (see Table 2A for detailed assay conditions). For comparison, all data points are expressed as percent increase over basal luciferase expression in the control cells.

Compounds that were previously shown to increase SMN expression including SAHA, sodium butyrate, aclarubicin, TSA, indoprofen, and tobramycin were tested in the cell lines (FIG. 3A). These compounds were screened in both the SMN1-luc and SMN2-luc cell lines and % increase of luciferase activity was plotted for SMN1-luciferase, SMN2-luciferase, and the CMV driven internal renilla luciferase control. The activity for each compound, except tobramycin, matched or exceeded the published activities for these compounds (FIG. 3A and Table 4). Tobramycin displayed no response in these cell lines. Tobramycin is an aminoglycoside that increases stable SMN protein levels from the SMN2 gene through transcriptional read-through of the termination codon in exon 8. By design, the reporter requires the inclusion of exon 7 and the frameshift mutation therein to restore the reading frame for luciferase. In the absence of exon 7, luciferase is out of frame. Read-through will not correct the frame shift, so tobramycin cannot and did not increase SMN-luciferase protein levels in the SMN-luciferase reporter cell lines.

Changes in the SMN-luciferase fusion protein levels were confirmed with SAHA in both the SMN1-luc and SMN2-luc cell lines and with sodium butyrate in the SMN2-luc cell line. There was a moderate increase in SMN-luciferase protein in the SMN1-luc cell line with increasing SAHA (FIG. 3B), which corresponds to the increase in luciferase activity (FIG. 3C). A greater than 9-fold increase in SMN-luciferase protein was observed when the SMN2-luc cell line was treated with either SAHA or sodium butyrate (FIG. 3B). This protein increase corresponds to an increase in luciferase activity (FIG. 3C). These data confirm the correlation between luciferase activity and levels of full-length SMN-luciferase protein.

Analysis of mRNA in SMN2-Luciferase Reporter by qRT-PCR

Based on the new reporter design, it was predicted that this screen could detect increased SMN-luciferase protein levels caused by compounds that stimulate SMN2 transcription, exon 7 inclusion, or by increasing the half-life of the SMN mRNA or protein. Quantitative reverse transcriptase PCR (qRT-PCR) was used to analyze SMN-luciferase mRNAs. All assays used RNA from control and compound-treated SMN2-luc cells and primers pairs were chosen to amplify only the SMN-luciferase derived transcripts (FIG. 4A). A pair of primers were used that specifically detects both full-length (exon 7 included) and Δ7 (exon 7 excluded) SMN-luciferase transcripts (primers 1 and 3). To measure changes in exon 7 splicing efficiency, a primer pair was used that detects only the full-length (exon 7 included) SMN-luciferase transcript (primers 1 and 2).

For each sample, the percent increase in the amount of total SMN-luciferase transcripts (gray bar) and exon 7 included full-length SMN-luciferase transcripts (white bar) was plotted (FIG. 4). Compounds that increase transcription should show increased total SMN-luciferase transcripts (gray bar) with a proportional increase for exon 7 included transcripts (white bar), assuming that proper splicing of exon 7 is not rate limiting. Compounds that stimulate exon 7 inclusion should increase the amount of exon 7 included full-length transcript (white bar) detected with little to no change in the expression of total SMN-luciferase transcripts (gray bar). In these experiments, cells were treated with compound, harvested, and each cell pellet was divided for isolation of RNA and to assay luciferase activity. Each qRT-PCR sample was normalized to the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The Pfaffl method was used to calculate the change in the amount of total SMN mRNA and determine whether compound treatments increased SMN transcripts.

With the pan HDAC inhibitor compounds SAHA, TSA, valproic acid, and sodium butyrate, increases in both the total and exon 7 included full-length SMN-luciferase transcripts were observed. The increase in total SMN-luciferase mRNA suggests that these compounds are increasing transcription, as would be expected for HDAC inhibitors. These compounds also display a dramatic increase in exon 7 included full-length transcripts that was greater in magnitude than the increase of total SMN-luciferase transcripts. This suggests that the HDAC inhibitors stimulate both SMN transcription and exon 7 recognition and inclusion. With aclarubicin at 300 nM, there was a potent increase in total SMN-luciferase transcript. This increase was accompanied by a lesser increase in exon 7 included transcript, indicating that aclarubicin increases transcription of SMN2. In a cell in which transcription is increased and splicing efficiency is unchanged, the percent increase in exon 7 included transcripts (gray bar) would be equal to the increase in total transcripts (white bar). In this case, the amount of exon 7 included transcripts has decreased even as the number of total transcripts increased. While aclarubicin does increase transcription, it appears to antagonize exon 7 recognition and inclusion. No consistent change in transcript levels was observed with indoprofen.

Genetic Modulation of SMN-Luciferase Protein Expression.

To confirm that the reporter could also respond to protein-induced changes in SMN expression, the splicing factors SF2/ASF and Tra2Pβ were overexpressed. SF2/ASF recognizes a splicing enhancer that includes C in the +6 position at the 5′ end of exon 7 in SMN1 to promote exon 7 inclusion. This interaction is antagonized by hnRNPA1, which binds at an overlapping splicing silencer that is created by the C to T transition at the +6 position in exon 7 in the SMN2 transcripts. Little to no increase in luciferase activity or change in RNA was observed in the SMN2-luciferase reporter cell-line (FIGS. 5A and C). This was expected, since hnRNPA1 has a high affinity for the silencing element in exon 7 of SMN2. Even at its highest levels of overexpression, SF2/ASF was unable to effectively stimulate the weakened enhancer element (FIG. 5B).

Tra2β is known to increase exon 7 inclusion in SMN2. Despite low levels of Tra2β expression (FIG. 5B), transfected Tra2 stimulated luciferase activity 2-3 fold greater than the negative control (FIG. 5A). With increasing amounts of Tra2β expressed there was up to a 6-fold increase in exon 7 included transcripts (white bar) with only a 1.4-fold increase in total transcripts (gray bar) (FIG. 5C). Analysis of the reporter mRNA confirmed that this SMN2-luciferase reporter detects increased inclusion of exon 7. From these data, the efficiency of exon 7 splicing of the reporter construct was calculated. Inclusion of exon 7 was 6.5% in the negative control sample, and no increase was observed with heterologous SF2/ASF expression. Exon 7 inclusion increased to 20% with the highest amount of transfected Tra2P. This validates the use of the SMN2-luciferase reporter cells to detect and quantify changes in exon 7 inclusion as well as changes in SMN expression in response to drug treatment and protein overexpression.

Assay Validation for High-Throughput

To evaluate the suitability of the SMN2-luc cells for HTS, test plates in both 96-well and 384-well format were prepared to determine signal strength, well-to-well percent coefficient of variation (% CV), amplitude of drug response, optimal cell density, and time of treatment. It was observed that these HEK derived cell lines displayed signal variability at low cell densities. As can be seen in Table 3, the correlation between luciferase signal and cell number was not linear. This is most clear in the 384-well format. At low cell densities, these cells grow slowly and are less responsive to treatment. A cell density of 50,000 or 10,000 per well was found to be optimal in the 96- and 384-well plates, respectively. To assess responsiveness, 500 g/mL sodium butyrate was selected as a stimulus. While sodium butyrate is an HDAC inhibitor that can cause non-specific transcriptional activation, it has been reported to stimulate SMN2 transcription and SMN2 exon 7 inclusion. Cells were treated for 24 or 48 hours and while increases in overall signal intensity were observed at the 48 hour time point, there was no difference in the % activation with sodium butyrate over control. However, there was an increase in the well-to-well % CV. Therefore 24 hours was chosen as the optimal time point for treatment. In the 96-well format, luciferase activity in the SMN2-luc cell increased by more than 3 fold with sodium butyrate and well-to-well % CV was 5% for both treated and control cells. In 384-well format, the % CV for control cells was 11% and 3% for treated. The “z” scores were calculated as 0.74 in 96-well and 0.78 in the 384-well formats, confirming that these assay conditions are suitable for HTS. These data are summarized in Table 3.

High-Throughput Screening and Hit Selection

An 115,000 compound library was screened using the screening protocol outlined in Table 2B. Each compound was added to a single well to a final concentration of ˜2.2 μM. The final DMSO concentration in test and control wells was 0.13%. Each plate included negative controls of 0.13% DMSO (n=16) and positive controls of 500 mg/mL sodium butyrate with 0.13% DMSO (n=16). For the entire screen, the average % CV was 9.1% for DMSO alone and 9.8% for sodium butyrate treated wells. The average increase with 500 mg/mL was 3.1 fold or 210%. A hit was defined by activation of greater than 6 times the % CV; 60%. 462 hits were identified for an overall 0.4% hit rate.

Hit Confirmation

The 462 hits were re-plated from the screening library into master plates and then re-screened at 0.1, 1, and 5 M in quadruplicate under conditions identical to the original HTS. Each compound was counter-screened against an unrelated luciferase control cell line that expresses luciferase from the minimal SV40 promoter and lacks an intron. This reporter should not respond to compounds that specifically affect the SMN promoter or compounds that change regulation of splicing. This allowed exclusion of compounds that may cause non-specific increases in luciferase expression. Of the 462 initial hits, 168 failed to reproduce at least 60% activation with the SMN2-luciferase reporter clone and were categorized as false positives (34% false positive rate). The remaining 294 compounds were limited to a high priority group of 19 scaffolds based on potency, strength of activation, dose dependency, specificity against luciferase control, and favorable chemical properties. All 19 compounds showed greater than 100% increase in reporter expression in the re-screen and stimulated the control reporter less than 40%. All 19 lacked overtly toxic functional groups and had chemical scaffolds that were tractable to chemical modification.

Compounds then re-screened in quadruplicate using a twelve-point dose response under the same conditions as the first two rounds of screening with both the SMN2-luc and SMN1-luc cell lines and using the SV40 luciferase control cell line. Since the SMN1 and SMN2 promoters are nearly identical, compounds that increased transcription of the SMN2-luc reporter would also increase transcription of the SMN1-luc reporter. The SMN-luc cells should therefore be responsive to compounds that increase transcription from the SMN promoter. However, since the SMN gene in the SMN1 cells includes exon 7 efficiently (>90%) only a small increase in % activation is possible with compounds that stimulate exon 7 inclusion.

Overall, this panel of reporter cell lines offers the ability to discriminate between compounds that increase SMN expression through promoter and splicing specific mechanisms and rule out non-specific activators. For example LDN-109657 (FIG. 6B) increased SMN2-luciferase levels up to 300% (4 fold), but also increased luciferase expression in the SMN-luc1 reporter and, to a lesser extent, the luciferase control cells. These data suggest that this compound acts by either increasing SMN transcription or protein stabilization. Several compounds decreased SMN1-luciferase expressed in the SMN1-luc reporter cell line, but still increased SMN2-luciferase expression in the SMN2-luc cell line (LDN-72939 and LDN-79199 FIG. 6B). Of 17 compounds tested in the twelve-point dose response, 13 increased luciferase expression by >60%, four did not. Initial confirmation and characterization of three of these compounds, LDN-72939, LDN-79199, and LDN-109657 is reported here. Overall, the amplitude of SMN-luciferase increase varied, but all three compounds displayed an EC50 in the low micromolar range; 1.1 μM, 750 nM, and 2.4 μM respectively.

To further evaluate the compounds, their effects on endogenous SMN protein levels were examined. Any cell containing even one copy of the SMN1 gene will produce enough SMN protein from SMN1 to mask the effects of the compounds on protein expression from the SMN2 gene. SMN null cells are not viable. The current standard is to test primary human fibroblast cells derived from a severe type 1 SMA patient. Most commonly used are the 3813 cells (SMN1^−/−; SMN2^+/+). These cells express very low basal levels of full-length SMN protein. For comparison, 3814 primary fibroblasts from the carrier parent (SMN1^+/−; SMN2^+/+) of this SMA infant are available. By quantitative immunoblot for full-length SMN protein, the heterozygous 3814 cells express 3-5 times more full-length SMN protein than in the 3813 cells²⁸(FIG. 6C).

The selected compounds were tested for their effect on total endogenous SMN protein levels. 3813 fibroblasts were treated with varying concentrations of each compound for 72 hours (FIG. 6C). It was observed that these primary fibroblasts were sensitive to lower concentrations of compound than those used in the immortal reporter cell lines. Not all compounds increase endogenous SMN levels in the fibroblasts as well as others, regardless of their activity in the reporter cell lines. LDN-72939 was more active in the reporter cell line but showed little activity in the fibroblasts. LDN-79199 was less active in the reporter cells, but increased endogenous SMN level 2-fold at 370 nM. LDN-109657 displayed high activity in both the reporter assay and in fibroblasts. It increased endogenous SMN levels 2-fold at 120 nM. The decrease in SMN at higher concentrations (1.1 M and 3.3 M) is likely due to either poor solubility or a decrease in cell proliferation in the fibroblasts.

Discussion

Spinal muscular atrophy is caused by an insufficient amount of functional, full-length SMN protein, usually resulting from deletion or disruption of both SMN1 alleles. All SMA patients retain at least one SMN2 gene and disease severity inversely correlates with SMN2 copy number. Since the SMN2 gene has the potential to express functional full-length SMN protein, it is an attractive therapeutic target for the treatment for SMA.

SMN2 expression can be increased through upregulation of transcription, promotion of exon 7 inclusion, stabilization of SMN2 mRNA and protein, or elevation of translation efficiency. HDAC inhibitors are known to influence transcription through histone deacetylation, which causes chromatin remodeling. HDAC inhibitors sodium butyrate, TSA, VPA, and SAHA all increased the amount of total and exon 7 included SMN2-luc reporter transcripts (FIG. 4B). Not only do these pan-HDAC inhibitors increase the quantity of SMN-luciferase transcripts, but a higher percentage of those transcripts are correctly spliced (FIG. 4B). This bimodal mechanism for pan-HDAC inhibitor regulation of SMN2 expression may explain the high potency and efficacy observed with these compounds, but may also predict other potential and possibly detrimental off-target effects.

Splicing of exon 7 is tightly regulated in both the SMN1 and SMN2 mRNAs. Conserved splicing enhancer and splicing silencing elements within exon 7 recruit splicing factors to the mRNA in order to regulate exon 7 recognition. Two of these splicing factors, hTra2β and SF2/ASF, were tested in the SMN2-luc reporter cell line. SF2/ASF had no impact on SMN2-luciferase expression (FIGS. 5A-5C). hTra2β binds to a splicing enhancer downstream of the hnRNP A1 site and can stabilize U1 snRNP binding at the 5′splice site of exon 7. This should increase exon 7 recognition and increase its splicing efficiency. An increase in SMN-luciferase activity was observed, and an increase in exon 7 included full-length SMN2-luciferase transcripts with hTra2β overexpression (FIGS. 5A-5C). The small increase in total reporter mRNA that accompanies this effect may be due to changes in the stability of the full-length, exon 7 included mRNA and not an actual increase in transcription of the reporter.

Disruption or regulation of the mRNA or protein turnover machinery could also increase steady-state SMN levels. This could be the mechanism for the activity of indoprofen, the aminoglycosides, and the quinazoline compounds. Indoprofen, a non-steroidal anti-inflammatory drug, was identified using a first generation reporter assay. Its mechanism of action has not been determined but recent evidence suggests that it has anti-terminator activity that may stabilize the SMN A7 protein. It is possible that the quinazoline compounds could increase the translation efficiency of SMN mRNA, as suggested by the recent report of interaction with the RNA decapping factor DcpS.

The SMN2 reporter cell line described herein combines the benefits of previous reporters and expands their potential to identify new regulatory circuitry for SMN2 expression. This assay has proven to be stable and reliable in 96, 384, and 1536-well formats and has been used in at three independent screening centers to identify novel modulators of SMN2 protein expression. Interestingly, the HTS at the NIH Chemical Genomics Center identified chemically distinct activators. In addition to novel compounds, these screens also identified compounds known to modify SMN2 protein expression, including indoprofen, resveratrol, hydroxyurea, and aclarubicin.

Characterization of LDN-72939, LDN-79199, and LDN-109657 are shown herein. Each of these compounds increases SMN-luciferase expression by at least 60%. LDN-79199 and LDN-109657 increased the levels of endogenous SMN protein in SMA-derived primary fibroblasts.

One of the drawbacks of the previous C33a reporter cell line was its high basal level of SMN-luciferase expression. This made detection of small increases in SMN-luciferase difficult. High basal level expression was initially encountered with the new HEK293 mixed-population reporter cells as well. By isolating and expanding clonal cell lines, cells could be selected for lower levels of basal SMN2-luciferase expression. Another issue with the previous C33a reporter was a progressive loss of luciferase signal intensity and decreased responsiveness to drug treatment. This variability in signal strength and drug response made the previous generation reporter unsuitable for high-throughput screening. The new HEK293 cell lines have maintained constant luciferase expression and reproducible induction with drug treatment over hundreds of population doublings. The improvement in this reporter assay is likely due to a combination of factors, including the new reporter design, the episomal nature of the vector, isolation of clonal cell lines, and use of HEK293 cells.

Spinal muscular atrophy is fatal for approximately 5,000 children each year in the United States, while tens of thousands of others live with limited mobility and progressive muscle weakness. There is presently no FDA approved drug for the treatment of spinal muscular atrophy. It has been established that the amount of SMN protein expressed has an inverse relationship to the severity to the disease. Compounds that safely increase SMN protein levels would dramatically improve the quality of life for individuals with SMA. The assay described herein is a valuable tool for identifying new compounds, characterizing existing compounds, and driving medicinal chemistry programs on active chemical scaffolds.

TABLE 2a SMN-luciferase standard conditions - 96 well format Sequence Parameter Value Description 1 Cells 100 μL 50,000 cells/well 96 TC treated white plate (See below for media ^a) 2 Time 24 hours 37° C. 5% CO₂ 3 Compound 100 μL With compound 2x concentration 4 Time 24 hours 37° C. 5% CO₂ 5 Remove media from wells 6 Reagent 30 μL SteadyGlo or DualGlo reagent (Promega) 7 Time 30 sec Room Temp 8 Detector See below ^b Wallac Envision ^aMedia: phenol red free DMEM + 10% FBS and 1x Pen/Strep ^bWallac settings; luminescent read, 1.0 sec integration

TABLE 2b SMN2-luciferase conditions for HTS - 384 well format Sequence Parameter Value Description 1 Cells 40 μL 10,000 cells/well 384 TC treated white plate (See below for media ^c) 2 Time 1 hour 37° C. 5% CO₂ 3 Compound 2.2 mM Final of 0.13% DMSO 4 Time 25 hours 37° C. 5% CO₂ 5 Reagent 25 μL Perkin Elmer SteadyLite 6 Time 30 minutes Room Temp 7 Detector See Below^d LJL Analyst HT ^cMedia: Phenol-free DMEM + 10% FBSand 1x Pen/Strep ^dLJL Analyst HT settings; luminescent read, 10 sec integration

TABLE 3 SMN2-luciferase Reporter validation with 0.5 mg/mL sodium butyrate 384- well LDDN Format 96-well validation 384-well validation screen Cells per well 25,000 50,000 25,000 50,000 5,000 7,500 10,000 10,000 Time point 24 hrs 24 hrs 48 hrs 48 hrs 24 hrs 24 hrs 24 hrs 24 hrs Na-But RLU* ave 2046 4798 3696 7505 1332 2832 39287 13894 Na-But stdev 138 234 536 756 131 329 1337 1272.55 CV Na-But 0.07 0.05 0.15 0.10 0.10 0.12 0.03 0.09 DMSO RLU* ave 684 1357 1425 2626 521 1008 8054 4677 DMSO stdev 44 64 61.7 248 98 123 910 387 CV DMSO 0.06 0.05 0.04 0.09 0.19 0.12 0.11 0.08 S/B 3.0 3.5 2.6 2.9 2.6 2.8 4.9 3.0 Z′ 0.60 0.74 0.21 0.38 0.15 0.26 0.78 0.46 *Relative Light Units (RLU) vary based on luciferase substrate, plate reader, and protocol

TABLE 4 Cell-based reporter response to known SMN2 modulating compounds Max. fold increase EC₅₀ Aclarubicin 10 298 nM Indoprofen 3 460 nM Sodium Butyrate 10 1 mg/mL Trichostatin A 15 230 nM SAHA 15 12 μM Valproic Acid 2.5 10 mM Tobramycin inactive ^a inactive ^a ^aTranscriptional read-through compounds do not score in this assay

TABLE 5 Activity of compounds tested in reporter assay % activ- Structure LND # ation 66854 210% 66278 114% 107992 121% 32531 108% 79199 102% 110116 97% 76070 122% 79213 90% 98541 124% 110181 120% 110425 93% 67615 105% 109981 98% 75654 106% 109657 152% 75847 85% 72939 102% 75676 136%

TABLE 6 Additional compounds tested in the reporter assay Ec50 Max % Compound Structure Active (μM) Activity LDN-75654 Yes 1.8 274 LDN-75676 Yes 2.6 337 LDN-75847 Yes 9.9 333 LDN-75879 Yes 1.5 180 CAL-1 No — — CAL-2 No — — CAL-3 No — — CAL-4 Yes 8 211 CAL-5 Yes 10 108 CAL-6 Yes 6.5 180 CAL-7 Yes 10 134 CAL-8 Weak 10 120 CAL-9 No — — CAL-10 Yes 2 250 CAL-25 Yes 0.35 237 CAL-26 Yes 94 160 CAL-27 Yes 1 125 CAL-28 Yes 0.9 59 CAL-29 No — — CAL-30 No — — CAL-31 Yes 16 154 CAL-33 Yes 1.7 217 CAL-36 No — — CAL-37 Yes 30 143 CAL-38 No — — CAL-42 No — — LDN-211826 Yes 1.1 150 LDN-211827 No/Weak — — LDN-211828 Yes 20 100 LDN-211829 No/Weak — — LDN-211830 No — — LDN-211831 Yes 3 150 LDN-211832 No — — LDN-211834 No — — LDN-211854 Yes 0.5 200 LDN-211855 Yes 1.5 125 LDN-211856 No — — LDN-211857 No — — LDN-211858 No — — LDN-211859 No — — LDN-211860 Yes 2.5 125 LDN-211861 Yes 3.7 100 LDN-211862 Nonspecific — — LDN-211906 Yes 0.8 250 LDN-211907 No/Weak — — LDN-211908 No/Weak — — LDN-211909 No/Weak — — LDN-211910 Yes 0.7 100 LDN-211911 Yes 0.4 175 LDN-211912 Yes 1.1 150 LDN-211981 Yes 5.9 100 LDN-211982 No — — LDN-211983 No — — LDN-211984 Yes 2.1 200 LDN-211985 Yes 0.8 150 LDN-211986 Yes 1.5 100 LDN-211992 Yes 0.15 100 LDN-212011 No — — LDN-212012 No — — LDN-212013 Yes 0.5 100 LDN-212014 Yes 0.5 180 LDN-212015 Yes 1.7 100 LDN-212016 Yes 0.3 250 LDN-212026 No — — LDN-212255 Yes 0.4 117 LDN-212256 Yes 0.4 114 LDN-213766 No — — LDN-214095 No — — LDN-214098 Yes 0.15 200 LDN-76070 Yes 6.6 198 LDN-76158 No — — LDN-76515 No — — LDN-76074 No/Weak — — CAL-21 Yes 251 14 CAL-22 No — — CAL-23 No — — CAL-50 No — — CAL-51 No — — CAL-52 No — — CAL-53 Yes 91 27 CAL-55 No — — CAL-56 No — — CAL-57 No — — LDN-212263 No — — LDN-212264 No — — LDN-212265 No — — LDN-212266 No/Weak — — LDN-212267 No — — LDN-212350 No/Weak — — LDN-212351 Yes 12 150 LDN-212352 No — — LDN-212353 No/Weak — — LDN-212354 No/Weak — — LDN-212355 No/Weak — — LDN-212356 Yes 43 150 LDN-212357 No — — LDN-212358 No — — LDN-212359 No — — LDN-212360 No — — LDN-212361 No — — LDN-212388 No — — LDN-212389 No/Weak — — LDN-212390 No — — LDN-212391 Yes 4.4 267 LDN-212392 No — — LDN-212393 No/Weak — — LDN-213767 Yes 8.4 125 LDN-213768 Yes 5.9 150 LDN-213769 No — — LDN-213770 No — — LDN-213771 No — — LDN-213772 No — — LDN-213773 No — — LDN-214085 Yes 6 180 LDN-214096 No — — LDN-214097 No — —

TABLE 7 Structure activity data Maximal Maximum % T_1/2in liver solubility in activation EC₅₀ microsomes PBS 75654 242.4 ± 35.1 2.0 μM ± 0.9 15 min >2 mM 212016 162.4 ± 62.4 0.3 μM ± 0.1 Not tested 500 μM 212014 156.6 ± 30.7 0.3 μM ± 0.3 39 min >2 mM 76070 185.7 ± 48.0 8.3 μM ± 4.5 Not tested 500 μM 212351 168.5 ± 10.6 9.8 μM ± 4.1 45 min 500 μM 212391 238.3 ± 28.5 5.0 μM ± 0.8 13 min 1 mM

Example 2

In this Example, compounds were tested using SMN2 reporter cells. Particularly, over >150,000 compounds were tested using SMN2 reporter cells. Secondary assays were performed to measure SMN protein levels using SMA type 1 patient-derived fibroblasts (3813 cells) by Western blot, gem counts, and quantitative RT-PCR of SMN transcripts.

Two of the compounds, LDN-75654 and LDN-76070, were further tested. Analogs of both were synthesized and characterized first in the SMN2-luc reporter assays and later by Western blot or gem count using 3813 SMA fibroblasts (FIGS. 25A and 25B). Those compounds that were validated and had tractable chemistry progressed to a synthetic phase in which scaffolds are modified and their properties evaluated. The compounds identified by this iterative process are included in this application.

Seventy-six (76) LDN 75654 analogs were tested to explore three different regions of the molecule, including introducing a hydroxyl group to various aliphatic substituents on the central heterocycle, replacing the isoxazole with other heterocycles (i.e. thiazole and pyridine) and creating variations to the anilide group. Exemplary compounds are shown below:

Exemplary analogs that emerged with activity are LDN-212016 (see FIG. 25A), LDN-212014, LDN-212255, and LDN-212256. Some of the compounds have different metabolic stability. For example, LDN-212014 had a t_1/2of 39 minutes in mouse liver microsomes compared to 14 min for LDN-75654.

Example 3

Forty eight (48) LDN-76070 analogs were evaluated. Exemplary compounds are shown below:

Modifications of the pendent phenyl were examined. In some embodiments, the 2,5-dihalo substituted compounds showed activity. The 2,5-dihalo substituted compounds had improved activity, such as LDN-212351. The change of bromine to chlorine increased stability, which may be advantageous. Not wishing to be limited by theory, the increased stability could be due to C—Cl bonds being stronger than C—Br bonds. LDN-212351 demonstrated a t_1/2of 45 min in mouse liver microsomes. Incorporation of an additional nitrogen atom into the central ring to generate urea LDN-212391 was tolerated (see FIG. 25A).

Exemplary results are listed in Table 8, below.

TABLE 8 Exemplary compound test results. 75654 212014 212016 214098 76070 212351 212391 214085 +++ ++++ ++++ ++++ ++ ++ +++ ++ Potency Luc Reporter ++++ +++ +++ +++ ++ ++ +++ ++ Activity Luc Reporter ++ ? ? ? ++++ +++ +++ ? Fibroblasts (n = 16) (n = 4) (n = 4) − ++++ +++ ? ++++ +++ +++ ? IP (n = 16) (n = 4) (n = 16) (n = 4) (n = 4) injections/Activity in Mice + + − + − − +/− ? Solubility in aqueous solution 15 min 39 min 3 min 59 min ? 45 min 13-20 min ? Stabilityin liver microsomes

Pilot experiments with the LDN compounds were initiated in SMA mice. Compounds LDN-75654 and LDN-76070 were tested in SMA mice to evaluate SMN-inducing activity in vivo. The compounds were injected intracerebroventricular (ICV) into SMA mice. Injections were performed daily for 3 days, and animals were harvested on day 3. LDN-76070 increased SMN protein in muscle and liver. Importantly, SMN was also significantly elevated in spinal cord and brain (Table 9). LDN-75654 did not increase SMN protein levels in these animals. Without the intention to be limited by theory, it is proposed that this may be due to the instability observed in the liver microsomal stability assay.

TABLE 9 Exemplary test results in SMA mice*. 75654 212014 212016 214058 76070 212351 212391 214085 +++ ++++ ++++ ++++ ++ ++ +++ ++ Potency Luc Reporter ++++ +++ +++ +++ ++ ++ +++ ++ Activity Luc Reporter ++ ? ? ? ++ ? ? ? Fibroblasts − ++++ +++ ? ++++ +++ +++ ? IP (n = 16) (n = 4) (n = 16) (n = 4) (n = 4) Injections + + − + − − +/− ? Solubility 15 min 39 min 3 min 59 min ? 45 min 13-20 min ? Stability *Neonatal SMN D7 mice (Smn−/− SMN2+/+ SMNΔ7+/+) were injected intraperitoneally twice daily for 3 days with compound or DMSO starting at post-natal day 2. Tissues were harvested and immunoblotted for SMN and actin. Representative data from brain.

The animal studies included new derivatives of LDN-76070 and LDN-75654. Mice were injected intraperitoneally once daily from post-natal day 1-10. Weight increase, time to right onto four legs, and extension of lifespan were chosen as parameters for efficacy. Compounds LDN-212014, LDN-212016, LDN-212351, and LDN-212391 were injected into a cohort of animals (3-4 each). Mice showed an extension of lifespan. In the Kaplan-Meier curve that DMSO control decreased survival by 50%—the compounds were in 20% DMSO (FIG. 26A). The weight of the treated animals also increased and some of the animals were able to right themselves starting at day 6 (FIG. 26B and Table 10).

TABLE 10 Time to right in seconds. Fail = >30 sec (raw data). Pup Inj. DOB PND6 PND7 PND8 PND9 PND10 PND11 PND12 4527.5 212014 Apr. 5, 2011 Fail Fail Fail Fail Fail 5 16 4389.4 212014 Apr. 5, 2011 dead dead dead dead dead dead dead 4378.4 212014 Apr. 5, 2011 Fail Fail Fail 26 Fail Fail dead 4514.3 212014 Apr. 5, 2011 Fail Fail Fail Fail Fail Fail dead 4527.7 212016 Apr. 5, 2011 Fail Fail Fail Fail Fail Fail Fail 4389.1 212016 Apr. 5, 2011 Fail Fail Fail Fail Fail Fail Fail 4378.5 212016 Apr. 5, 2011 Fail 25 Fail Fail Fail Fail Fail 4515.5 212016 Apr. 5, 2011 Fail Fail Fail Fail 12 9 Fail 4516.3 212351 Apr. 5, 2011 dead dead dead dead dead dead dead 4533.5 212351 Apr. 5, 2011 Fail Fail Fail 13 Fail dead dead 4358.4 212351 Apr. 5, 2011 Fail Fail Fail Fail Fail dead dead 4354.1 212351 Apr. 5, 2011 3 5 Fail Fail Fail Fail Fail 4516.4 212391 Apr. 5, 2011 Fail Fail Fail Fail Fail Fail dead 4514.2 212391 Apr. 5, 2011 Fail Fail Fail Fail Fail Fail Fail 4354.4 212391 Apr. 5, 2011 Fail Fail Fail 18 20 Fail Fail 4378.2 DMSO Apr. 5, 2011 Fail Fail Fail Fail dead dead dead 4258.6 DMSO Apr. 5, 2011 dead dead dead dead dead dead dead 4514.1 DMSO Apr. 5, 2011 dead dead dead dead dead dead dead 4515.6 DMSO Apr. 5, 2011 dead dead dead dead dead dead dead Pup PND13 PND14 PND15 PND16 PND17 PND18 PND19 PND20 4527.5 Fail 5 14 Fail Fail dead dead dead 4389.4 dead dead dead dead dead dead dead dead 4378.4 dead dead dead dead dead dead dead dead 4514.3 dead dead dead dead dead dead dead dead 4527.7 dead dead dead dead dead dead dead dead 4389.1 Fail dead dead dead dead dead dead dead 4378.5 Fail Fail dead dead dead dead dead dead 4515.5 11 Fail Fail Fail Fail dead dead dead 4516.3 dead dead dead dead dead dead dead dead 4533.5 dead dead dead dead dead dead dead dead 4358.4 dead dead dead dead dead dead dead dead 4354.1 Fail Fail dead dead dead dead dead dead 4516.4 dead dead dead dead dead dead dead dead 4514.2 Fail Fail Fail Fail Fail Fail Fail dead 4354.4 Fail Fail Fail dead dead dead dead dead 4378.2 dead dead dead dead dead dead dead dead 4258.6 dead dead dead dead dead dead dead dead 4514.1 dead dead dead dead dead dead dead dead 4515.6 dead dead dead dead dead dead dead dead

LDN-212014 and LDN-76070 were further tested in A7 SMA model mice. Mice were dosed using compounds dissolved in 100% DMSO injected at 20 mg/kg with each dose administered once daily by intraperitoneal injection. As shown in the black curves in the Kaplan-Meier plot, control animals lived 4-5 days longer than the DMSO vehicle treated animals, indicating toxicity. Nonetheless, both 76070 and 212014 compounds significantly increased lifespan despite this DMSO associated toxicity (p<0.0001). In fact, the compounds display a statistically significant increase in survival compared with the untreated animals. These compounds extend the lifespan of SMA mice despite the DMSO toxicity. Test results of LDN-212014 and LDN-76070 were shown in FIGS. 8-24, 27-28 and others.

These experiments also demonstrated there was a concomitant increase in motor function in the treated animals. In ‘time to right’ experiments, animals are placed on their backs and the duration for animals to right themselves is recorded. Animals that are unable to right in less than 30 seconds are scored as a failure. DMSO treated animals were unable to right themselves, while a small percentage of untreated animals display the ability to right themselves for up to postnatal day (PND) 11. A larger percentage of treated animals can right themselves past PND 17, and in the case of one animal as late as PND 21.

To assess SMN protein level, tissues were harvested from three treated animals from each experiment at PND 7 and compared to wild type, untreated, and DMSO treated animals. Tissues from brain, spinal cord, and muscle were assayed. As shown in the western blots (FIG. 29), both compounds increase SMN protein levels in brain and spinal cord to greater than 75% that of wild type animals. They also promoted an increase of about 25% that of wild type in muscle. High levels of increase in these tissues are very desirable, especially in tissues of the CNS, suggesting that these compounds can pass through the blood brain barrier.

Exemplary Synthesis of Compounds.

In some embodiments, certain compounds described in the application are prepared using the general procedure outlined in Scheme 1 (Synthesis 2006, (22), 3805; Jiegou Huaxue 2007, 26(5), 533; Tetrahedron Lett. 2005, 46, 7169):

In some embodiments, several of the urea analogs are prepared using the procedures outlined in Scheme 2 (Perkins Trans 2 2001, 2226 and J. Heterocycl Chem 1982, 19, 1453):

In other embodiments, several seven-member ring analogs are prepared using the procedures outlined in Scheme 3 (J. Am. Chem. Soc. 1954, 76, 4550; J. Med Chem. 1974, 17, 668; J. Med Chem. 2006, 49, 3520-3535; J. Org. Chem. 1986, 51, 5001-5002):

In some embodiments, certain compounds are prepared using the procedure outline in Scheme 4 with aryl or heteroaryl acyl chlorides and aryl or heteroaryl amines. In other embodiments, a two-step process is used starting with aryl or heteroaryl carboxylic acids.

In some embodiments, certain heteroaryl carboxylic acids are prepared using the procedure outlined in Scheme 5 (Eur. J. Org. Chem. 2007, 4352-4359) and in Scheme 6 (J. Am. Chem. Soc. 1992, 114, 9450 and J. Org. Chem. 1993, 58, 4495).

In some embodiments, the cyclohexyl analog is prepared using the procedure outlined in Scheme 7 (Synthesis 1992, 769).

In some embodiments, certain heteroaryl amines are prepared using the procedure outlined in Scheme 8.

Claims

1. A compound of formula I: or a pharmaceutically acceptable salt thereof, wherein

each of Ring A and Ring B is independently an optionally substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

L1 is independently a covalent bond or an optionally substituted bivalent C1-6 hydrocarbon chain, wherein one or more methylene units of L1 are optionally and independently replaced by —O—, —S—, —C(O)—, —C(S)—, —C(NR′)—, —C(O)N(R′)—, —N(R′)C(O)N(R′)—, —N(R′)C(O)—, —N(R′)C(O)O—, —OC(O)N(R)—, S—(O)—, —S(O)2—, —S(O)2N(R)—, —N(R)S(O)2—, —OC(O)—, or —(O)0-;

each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and

each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

2. The compound according to claim 1, wherein said compound has the structure of formula II: or a pharmaceutically acceptable salt thereof, wherein

each of Ring A′ and Ring B′ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

L2 is —C(O)N(R′)—;

each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and

each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

3. The compound according to claim 2, wherein said compound has the structure of formula 11-a: or a pharmaceutically acceptable salt thereof, wherein:

Ring A″ is an optionally substituted phenyl or benzimidazolyl ring;

Ring B″ is an optionally substituted 5-6 membered heteroaryl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

L3 is —C(O)NH—;

each R4 is independently halogen or R;

each R5 is independently an optionally substituted C1-6 aliphatic;

each of d and e is independently 0-5; and

each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

4. The compound according to claim 3, wherein said compound has the structure of:

5. The compound according to claim 3, wherein said compound has the structure of:

6. The compound according to claim 3, wherein said compound has the structure of:

7. The compound according to claim 3, wherein said compound has the structure of:

8. The compound according to claim 1, wherein said compound has the structure of formula III: or a pharmaceutically acceptable salt thereof, wherein

Ring C″ is independently an optionally substituted group selected from phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

each of R1, R2 and R3 is independently halogen, R′, —C(O)R′, —C(S)R′, —CO2R′, —C(O)N(R′)2, —C(S)N(R′)2, —S(O)R′, —SO2R′, —SO2N(R′)2, —OR′, —O—(C1-6 aliphatic)-N(R′)2, —O0-(C1-6 aliphatic)-OR′, —OC(O)R′, —SR′, —NO2, —N(R′)2, —NR′C(O)R′, —NR′C(O)OR′, —NR′C(O)N(R′)2, —NR′SO2R′, —NR′SO2N(R′)2, or —NR′OR′;

a is 1-4;

b is 1-5;

X1 is —C(Rx)2—, —NRx—, —NRxC(Rx)2— or —OC(Rx)2—;

X2 is —C(Rx)2— or —NRx—;

each Rx is independently R′, —(C1-6 aliphatic)-N(R)2, or —(C1-6 aliphatic)-OR′;

each R′ is independently —R, —C(O)R, —CO2R, or —SO2R, or:

two R′ on the same nitrogen are taken together with their intervening atoms to form a 3-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; and

each R is hydrogen, or an optionally substituted group selected from C1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring, a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

9. The compound according to claim 1, selected from those depicted in Table 1, or a pharmaceutically acceptable salt thereof.

10. A composition comprising a compound according to claim 1 and a pharmaceutically acceptable carrier, adjuvant or vehicle.

11. A method for increasing the production of full-length SMN protein in a cell having an SMN2 gene, the method comprising contacting the cell with a compound or composition according to claim 1.

12. The method of claim 11, wherein the full-length SMN protein is produced by upregulation of SMN2 activity.

13. The method of claim 12, wherein the upregulation of SMN2 activity includes increased expression of full-length SMN2 transcripts.

14. A method of increasing the production of full-length SMN protein in a cell having an SMN2 gene, the method comprising contacting the cell with a compound or composition according to claim 2.

15. The method of claim 14, wherein the full-length SMN protein is produced by upregulation of SMN2 activity.

16. A method of increasing the production of full-length SMN protein in a cell having an SMN2 gene, the method comprising contacting the cell with a compound or composition according to claim 3.

17. The method of claim 16, wherein the full-length SMN protein is produced by upregulation of SMN2 activity.

18. A method of treating a patient susceptible to or having spinal muscular atrophy, the method comprising administering to the patient a therapeutically effective amount of a compound or composition of claim 1.

19. A method of treating a patient susceptible to or having spinal muscular atrophy, the method comprising administering to the patient a therapeutically effective amount of a compound or composition of claim 2.

20. A method of treating a patient susceptible to or having spinal muscular atrophy, the method comprising administering to the patient a therapeutically effective amount of a compound or composition of claim 3.