Merrimack Pharmaceuticals, Inc. announced that preclinical data regarding the bispecific antibody MM-111 will be presented at the American Society of Clinical Oncology 2013 Gastrointestinal Cancers Symposium (ASCO GI), January 24-26, 2013 in San Francisco. MM-111 is designed to inhibit ErbB3 (HER3) receptor signaling in ErbB2 positive (HER2 or ErbB2+) cancer. Overexpression of the ErbB2 cell surface receptor has been reported in 7-34% of gastric cancers, and research has shown that ErbB3 levels are associated with poor prognosis in gastric cancer, which may contribute to resistance to therapy over time.

MM-111's bispecific design allows it to attach to ErbB2 receptors on the surface of tumor cells and then inhibit its target ErbB3. Signaling through ErbB3 appears crucial to a tumor's growth and survival during chemotherapy.