CAMBRIDGE, Mass., July 22, 2013 (GLOBE NEWSWIRE) -- Merrimack Pharmaceuticals, Inc. (Nasdaq:MACK) today announced the enrollment of its first patient in a Phase 2 clinical trial of its bispecific antibody, MM-111, for the treatment of advanced gastric, esophageal and gastroesophageal junction (GEJ) cancers. Overexpression of the HER2 (ErbB2) cell surface receptor has been reported in 7-34 percent of stomach and esophageal cancers. The HER2 receptor triggers tumor growth and survival when it binds together with an additional receptor known as HER3 (ErbB3) and another protein called heregulin. HER3 expression has been associated with poor prognosis in gastric cancer. MM-111 is designed to anchor to both receptors, HER2 and HER3, on the cell surface and block heregulin's ability to transmit tumor growth signals, thus inhibiting the tumor cell's ability to thrive. This Phase 2 study is unique in that it is testing MM-111 in two different subsets of patients overexpressing the HER2 receptor:
- The first set of patients traditionally receive trastuzumab-based therapy due to their HER2 score of 2+ or 3+ on the HercepTest® and/or have a positive fluorescence in situ hybridization status (FISH+). These patients will be randomized to receive either MM-111 combined with paclitaxel and trastuzumab or paclitaxel and trastuzumab.
- The second set of patients in the study are usually not treated with HER2-targeted therapy because they have a HER2 2+ HercepTest® score and have a negative FISH status (FISH-) for the HER2 gene. Some of these patients may still have relatively high HER2 levels but there are currently no HER2-targeted therapy options available for them. These patients will be randomized to receive either MM-111 combined with paclitaxel or paclitaxel alone.