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: Described herein are antibody constructs comprising a 4- 1BB binding domain and an anti-Folate Receptor a (FRa) antigen- binding domain, wherein the 4-1BB-binding domain and the FR? antigen-binding domain are linked directly or indirectly to a scaffold. The scaffold may be an Fc construct with modifications that reduce its ability to mediate effector function. The antibody constructs are used in the treatment of a subject having cancer.

Abstract: Described herein are antibody constructs comprising a 41-1BB binding domain and an antigen-binding domain that binds to a tumor-associated antigen (TAA), wherein the 4-1BB-binding domain and the TAA antigen-binding domain are linked directly or indirectly to a scaffold. The scaffold may be an Fc construct with modifications that reduce its ability to mediate effector function.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: Provided herein are multispecific antigen-binding polypeptide constructs comprising at least two different heterodimers, each comprising a heavy chain and a light chain. At least one heterodimer comprises a Fab region comprising a lambda light chain and at least one heterodimer comprises a Fab region comprising a kappa light chain. One or more of the immunoglobulin heavy and light chains that form the antigen-binding polypeptide construct comprise amino acid modifications that promote correct pairing between the heavy and light chains to form the desired multispecific antigen-binding polypeptide construct. The amino acid modifications may be in the CH1 and/or CL domains, in the VH and/or VL domains, or a combination thereof.

Abstract: Provided herein are multispecific antigen-binding polypeptide constructs comprising at least two different heterodimers, each comprising a heavy chain and a light chain. At least one heterodimer comprises a Fab region comprising a lambda light chain and at least one heterodimer comprises a Fab region comprising a kappa light chain. One or more of the immunoglobulin heavy and light chains that form the antigen-binding polypeptide construct comprise amino acid modifications that promote correct pairing between the heavy and light chains to form the desired multispecific antigen-binding polypeptide construct. The amino acid modifications may be in the CH1 and/or CL domains, in the VH and/or VL domains, or a combination thereof.

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 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 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: Provided herein are multispecific antigen-binding polypeptide constructs comprising at least two different heterodimers, each comprising a heavy chain and a light chain. At least one heterodimer comprises a Fab region comprising a lambda light chain and at least one heterodimer comprises a Fab region comprising a kappa light chain. One or more of the immunoglobulin heavy and light chains that form the antigen-binding polypeptide construct comprise amino acid modifications that promote correct pairing between the heavy and light chains to form the desired multispecific antigen-binding polypeptide construct. The amino acid modifications may be in the CH1 and/or CL domains, in the VH and/or VL domains, or a combination thereof.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides 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: The present invention provides 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: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the CH1 and/or CL domains, one or more amino acid modifications in the VH and/or VL domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides heterodimer pairs that can comprise a first heterodimer and a second heterodimer wherein each heterodimer comprises an immunoglobulin heavy chain or fragment thereof and an immunoglobulin light chain or fragment thereof. At least one of the heterodimers can comprise one or more amino acid modifications in the C H and/or C L domains, one or more amino acid modifications in the V H and/or V L domains, or a combination thereof. The modified amino acid(s) can be part of the interface between the light chain and heavy chain and are typically modified 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 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 typically preferentially pairs with the second light chain rather than first.

Abstract: The present invention provides 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.