ImmunoGen is TAP, TAP, TAPping its way toward a cure for cancer. The firm's product candidates are TAPs, or tumor-activated prodrugs, that combine cancer-killing drugs with monoclonal antibodies (single-source proteins) and attach only to tumor cells. Its lead compounds are trastuzumab emtansine, which is being developed with Genentech to treat breast cancer; lorvotuzumab mertansine to treat solid tumors and multiple myelomas; and SAR3419 for non-Hodgkin's lymphoma. Along with good ol' R&D, a large part of ImmunoGen's business is derived from licensing its TAP technology to other pharmaceutical companies.