CytomX is developing CX-2009, a Probody drug conjugate (PDC) conjugated with DM4, a highly potent cytotoxic drug, targeting CD166, also known as ALCAM. CD166 is a molecule widely and highly expressed on solid tumor cells and previously considered “undruggable” given its expression on normal tissues. In preclinical studies, Probody drug conjugates targeting CD166, have led to complete regressions in models of breast and lung cancer at therapeutically relevant doses, and are well tolerated in non-human primates.
Updated Phase 1 results of CX-2009 in selected tumor types were announced at ASCO 2020 demonstrating durable clinical activity in HER2 negative (HER2-) breast cancer. In December 2019, CytomX initiated a Phase 2 expansion study in patients with hormone receptor (ER, PR) positive, HER2- breast cancer.