Merrimack Pharmaceuticals 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, or GEJ, cancers. 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. 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 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.