Il-12 compositions and methods of use thereof

An attenuated protein heterodimer, comprising a first polypeptide and a second polypeptide, wherein:

• (a) the first polypeptide comprises, in an N- to C-terminal orientation, a variable heavy chain (VH) region and a CH1 region, an optional linker, and an IL-12A (p35) protein, and the second polypeptide comprises, in an N- to C-terminal orientation, a variable light chain (VL) region and a CL region, an optional linker, and an IL-12B (p40) protein, wherein the p35 protein of the first polypeptide is bound to the p40 protein of the second polypeptide;
• or
• (b) the first polypeptide comprises, in an N- to C-terminal orientation, a variable heavy chain (VH) region and a CH1 region, an optional linker, and an IL-12B (p40) protein, and the second polypeptide comprises, in an N- to C-terminal orientation, a variable light chain (VL) region and a CL region, an optional linker, and an IL-12A (35) protein, wherein the p40 protein of the first polypeptide is bound to the p35 protein of the second polypeptide,
• wherein the CH1 region and the CL region of (a) or (b) are bound together via a disulfide bond to form an immunoglobulin antigen binding domain (ABD), wherein the ABD specifically binds to a cell surface protein expressed on a cell, a plasma protein, or an extracellular matrix (ECM) protein, and wherein at least one of the p35 and/or the p40 protein is a variant that has one or more amino acid alterations relative to a wild-type p35 or p40 sequence, and which has reduced binding affinity to a wild-type IL-12Rβ1/IL-12Rβ2 receptor complex on the surface of an immune cell in vitro or in vivo relative to that of the wild-type p35 and/or p40 sequence.