Abstract: The present application provides activatable antibodies comprising an antibody comprising an antigen-binding domain (ABD), wherein the ABD comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the N-terminus of the VH is fused to a first polypeptide shield moiety (S1), and the N-terminus of the VL is fused to a second polypeptide shield moiety (S2), wherein S1 comprises a first disease-sensing releasable moiety (DS1) and/or S2 comprises a second disease-sensing releasable moiety (DS2), wherein association of S1 with S2 blocks binding of the ABD to its target, and wherein the ABD does not specifically bind to S1, S2, or association thereof. Composition, methods of treatment using the activatable antibodies, and methods of preparation thereof are further provided.

Abstract: Provided herein, inter alia, are isolated, humanized antibodies that bind an extracellular domain of a human SIRP-? polypeptide. Also provided are polynucleotides, vectors, host cells, and methods of production and use related thereto.

Abstract: The present disclosure features signal-regulatory protein ? (SIRP?) polypeptides and constructs that are useful, e.g., to target a cell (e.g., a cancer cell or a cell of the immune system), to increase phagocytosis of the target cell, to eliminate immune cells such as regulatory T-cells, to kill cancer cells, to treat a disease (e.g., cancer) in a subject, or any combinations thereof. The SIRP-? constructs include a high affinity SIRP-? D1 domain or variant thereof that binds CD47 with higher affinity than a wild-type SIRP-?. The SIRP-? polypeptides or constructs include a SIRP-? D1 variant fused to an Fc domain monomer, a human serum albumin (HSA), an albumin-binding peptide, or a polyethylene glycol (PEG) polymer. Compositions provided herein include (i) a polypeptide including a signal-regulatory protein ? (SIRP-?) D1 variant and (ii) an antibody.

Abstract: The present disclosure features signal-regulatory protein ? (SIRP-?) polypeptides and constructs that are useful, e.g., to target a cell (e.g., a cancer cell or a cell of the immune system), to increase phagocytosis of the target cell, to eliminate immune cells such as regulatory T-cells, to kill cancer cells, to treat a disease (e.g., cancer) in a subject, or any combinations thereof. The SIRP-? constructs include a high affinity SIRP-? D1 domain or variant thereof that binds CD47 with higher affinity than a wild-type SIRP-?. The SIRP-? polypeptides or constructs include a SIRP-? D1 variant fused to an Fc domain monomer, a human serum albumin (HSA), an albumin-binding peptide, or a polyethylene glycol (PEG) polymer. Compositions provided herein include (i) a polypeptide including a signal-regulatory protein ? (SIRP-?) D1 variant and (ii) an antibody.