The present disclosure provides antibody-drug conjugates comprising (i) antibodies that specifically bind to Mer Tyrosin Kinase (MERTK) (e.g., human MERTK, or both human and mouse MERTK), and (ii) cytotoxic agents conjugated directly to the antibodies or conjugated to the antibodies via linkers, and compositions comprising such antibody-drug conjugates, wherein the antibodies contained in the antibody-drug conjugates agonize MERTK signaling of endothelial cells. The present disclosure also provides methods for treating cancer, by administering an antibody-drug conjugate that comprises (i) an antibody that specifically binds to MERTK and agonizes MERTK signaling of endothelial cells, and (ii) a cytotoxic agent conjugated directly to the antibody or conjugated to the antibody via a linker.