A fully human, IgG2 monoclonal antibody directed against activin-like receptor kinase 1 (ALK-1) with potential antineoplastic activity. Anti-ALK-1 monoclonal antibody PF-03446962 binds to and neutralizes ALK-1. This may disrupt tumor endothelial cell function and inhibit tumor angiogenesis, eventually leading to an inhibition of tumor cell proliferation. ALK-1, a member of the transforming growth factor beta (TGF-b) type I receptor family, is overexpressed on endothelial cells in a variety of tumor cell types and increases endothelial cell proliferation and migration.