Abstract: Mice are provided that comprise a reduction or deletion of ADAM6 activity from an endogenous ADAM6 locus, or that lack an endogenous locus encoding a mouse ADAM6 protein, wherein the mice comprise a sequence encoding an ADAM6 or ortholog or homolog or fragment thereof that is functional in a male mouse. In one embodiment, the sequence is an ectopic ADAM6 sequence or a sequence that confers upon a male mouse the ability to generate offspring by mating. Mice and cells with genetically modified immunoglobulin heavy chain loci that comprise an ectopic nucleotide sequence encoding a mouse ADAM6 or functional fragment or homolog or ortholog thereof are also provided.

Abstract: Antitumor antagonists that bind specifically to immune checkpoint regulators, angiogenesis pathway regulators and/or TGF pathway regulators are disclosed. Also disclosed are methods for treating proliferative disorders, infections, and immunological disorders with the antitumor antagonists described herein.

Abstract: Mice, embryos, cells, and tissues having a restricted immunoglobulin heavy chain locus and an ectopic sequence encoding one or more ADAM6 proteins are provided. In various embodiments, mice are described that have humanized endogenous immunoglobulin heavy chain loci and are capable of expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof that is functional in a male mouse. Mice, embryos, cells, and tissues having an immunoglobulin heavy chain locus characterized by a single human VH gene segment, a plurality of human DH gene segments and a plurality of human JH gene segments and capable expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof are also provided.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Antitumor antagonists that bind specifically to immune checkpoint regulator are disclosed. Also disclosed is a method of treating proliferative disorders with the antitumor antagonists.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Mice, embryos, cells, and tissues having a restricted immunoglobulin heavy chain locus and an ectopic sequence encoding one or more ADAM6 proteins are provided. In various embodiments, mice are described that have humanized endogenous immunoglobulin heavy chain loci and are capable of expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof that is functional in a male mouse. Mice, embryos, cells, and tissues having an immunoglobulin heavy chain locus characterized by a single human VH gene segment, a plurality of human DH gene segments and a plurality of human JH gene segments and capable expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof are also provided.

Abstract: Antitumor antagonists that bind specifically to immune checkpoint regulator are disclosed. Also disclosed is a method of treating proliferative disorders with the antitumor antagonists.

Abstract: A human antibody or an antigen-binding fragment which binds human IL-6 receptor (hIL-6R) with a KD of about 500 pM or less and blocks IL-6 activity with an IC50 of 200 pM or less, is provided. In preferred embodiments, the antibody the antibody or antigen-binding fragment binds hIL-6R with an affinity at least 2-fold higher relative to its binding monkey IL-6R.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: Mice, embryos, cells, and tissues having a restricted immunoglobulin heavy chain locus and an ectopic sequence encoding one or more ADAM6 proteins are provided. In various embodiments, mice are described that have humanized endogenous immunoglobulin heavy chain loci and are capable of expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof that is functional in a male mouse. Mice, embryos, cells, and tissues having an immunoglobulin heavy chain locus characterized by a single human VH gene segment, a plurality of human DH gene segments and a plurality of human JH gene segments and capable expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof are also provided.

Abstract: Mice, tissues, cells, and genetic material are provided that comprise a humanized heavy chain immunoglobulin locus, a humanized light chain locus that expresses a universal light chain, and a gene encoding an ADAM6 or ortholog or homolog or functional fragment thereof. Mice are provided that express humanized heavy chains comprising human variable domains, and that express humanized light chains comprising human variable domains wherein the light chains are derived from no more than one, or no more than two, light chain V and J or rearranged V/J sequences. Fertile male mice that express antibodies with universal light chains and humanized heavy chains are provided. Methods and compositions for making bispecific binding proteins are provided.

Abstract: Provided herein are cytokines or functional fragments thereof that, in some embodiments, are engineered to be masked by a masking moiety at one or more receptor binding site(s) of the cytokine or functional fragment thereof. In some embodiments, the cytokines are engineered to be activatable by a protease at a target site, such as in a tumor microenvironment, by including a proteolytically cleavable linker. In some embodiments, the proteolytically cleavable linker links the cytokine to the masking moiety, links the cytokine to a half-life extension domain, and/or links the masking moiety to a half-life extension domain. The masking moiety blocks, occludes, inhibits (e.g., decreases) or otherwise prevents (e.g., masks) the activity or binding of the cytokine to its cognate receptor or protein. Upon proteolytic cleavage of the cleavable linker at the target site, the cytokine becomes activated, which renders it capable of binding to its cognate receptor or protein with increased affinity.

Abstract: A human antibody or an antigen-binding fragment which binds human IL-6 receptor (hIL-6R) with a KD of about 500 pM or less and blocks IL-6 activity with an IC50 of 200 pM or less, is provided. In preferred embodiments, the antibody the antibody or antigen-binding fragment binds hIL-6R with an affinity at least 2-fold higher relative to its binding monkey IL-6R.

Abstract: Mice, tissues, cells, and genetic material are provided that comprise a humanized heavy chain immunoglobulin locus, a humanized light chain locus that expresses a universal light chain, and a gene encoding an ADAM6 or ortholog or homolog or functional fragment thereof. Mice are provided that express humanized heavy chains comprising human variable domains, and that express humanized light chains comprising human variable domains wherein the light chains are derived from no more than one, or no more than two, light chain V and J or rearranged V/J sequences. Fertile male mice that express antibodies with universal light chains and humanized heavy chains are provided. Methods and compositions for making bispecific binding proteins are provided.

Abstract: The invention provides activatable masked anti-CTLA4 binding proteins (e.g., antibodies, bispecific antibodies, and chimeric receptors) and their use in treating and preventing cancer, as well as compositions and kits comprising the activatable masked anti-CTLA4 binding proteins.