Abstract: Described herein are high affinity antigen binding constructs, e.g., antibodies, directed to the ECD2 domain of HER2. The antigen-binding constructs comprise at least one antigen-binding polypeptide construct that binds to ECD2 of HER2 (HER2 ECD2) with increased affinity compared to a wild-type 2C4 antibody. Such antigen-binding polypeptide constructs comprise one or more amino acid modifications in the framework region and/or CDRs compared to the amino acid sequence of a wild-type 2C4 antibody that increase affinity of the antigen-binding polypeptide construct for ECD2 by 2-fold or greater. The antigen-binding constructs can inhibit the growth of HER2-expressing breast cancer cells and gastric cancer cells. Antigen-binding constructs in biparatopic format are internalized in HER2-expressing cells.

Abstract: Provided herein are biparatopic antigen-binding constructs that specifically bind HER2. The biparatopic antigen-binding constructs comprise one antigen-binding moiety that binds to ECD2 of HER2, a second antigen-binding moiety that binds to ECD4 of HER2, and an Fc. At least one of the antigen-binding moieties is an scFv. The biparatopic antigen-binding constructs can be used in the treatment of cancer.

Abstract: Described herein methods of using antigen-binding constructs to treat HER2+ tumors in a subject such as breast, lung, or head and neck tumors. In some aspects, the tumor volume in the subject after receiving at least seven doses of the antigen binding construct is less than the tumor volume of a control subject receiving an equivalent amount of trastuzumab. In some aspects, the survival of the subject receiving the antigen binding construct is increased as compared to a control subject receiving an equivalent amount of a non-specific control antibody or as compared to a control subject not receiving treatment.

Abstract: Described herein is a method of treating breast cancer comprising administering a bispecific antigen-binding construct targeting HER2 or a bispecific antigen-binding construct targeting HER2 linked to an auristatin analogue (ADC) in combination with a CDK4/6 inhibitor to a subject.

Abstract: Provided are heterodimer pairs comprising a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain. At least one of the heterodimers comprises amino acid modifications in the CH1 and/or CL domains, amino acid modifications in the VH and/or VL domains or a combination thereof. The modified amino acid residues are part of the interface between the light chain and heavy chain and are modified in order to create preferential pairing between each heavy chain and a desired light chain such that when the two heavy chains and two light chains of the heterodimer pair are co-expressed in a mammalian cell, the heavy chain of the first heterodimer preferentially pairs with one of the light chains rather than the other. Likewise, the heavy chain of the second heterodimer preferentially pairs with the second light chain rather than first.

Abstract: Provided herein are biparatopic antigen-binding constructs that specifically bind HER2. The biparatopic antigen-binding constructs comprise one antigen-binding moiety that binds to ECD2 of HER2, a second antigen-binding moiety that binds to ECD4 of HER2, and an Fc. At least one of the antigen-binding moieties is an scFv. The biparatopic antigen-binding constructs can be used in the treatment of cancer.

Abstract: Provided herein are stabilized chimeric Fabs derived from a parent chimeric Fab having a lambda light chain. The stabilized chimeric Fabs comprise an immunoglobulin heavy chain polypeptide construct from the parent chimeric Fab, having a CH1 sequence and a VH sequence, as well as a Vlambda-Ckappa chimeric light chain construct. The Vlambda sequence of the chimeric light chain construct corresponds to that of the parent chimeric Fab, and comprises one or more stabilizing amino acid modifications that increase the thermal stability of the stabilized chimeric Fab compared to the parent chimeric Fab. The stabilized Fabs are useful as therapeutic polypeptides, or can be used to prepare antibody constructs in other formats. The stabilized chimeric Fabs may also be useful generally to increase the stability of antibodies having lambda light chains.

Abstract: Compounds having cytotoxic and/or anti-mitotic activity are disclosed. Methods associated with preparation and use of such compounds, as well as pharmaceutical compositions comprising such compounds, are also disclosed. Also disclosed are compositions having the structure: (T)-(L)-(D), wherein (T) is a targeting moiety, (L) is an optional linker, and (D) is a compound having cytotoxic and/or anti-mitotic activity.