CAMBRIDGE, Mass., Oct. 2, 2012 /PRNewswire/ -- Merrimack Pharmaceuticals, Inc. (NASDAQ: MACK) today announced the presentation of Phase 1 safety and clinical results evaluating two potential new therapies with a novel target – ErbB3, a signaling receptor believed to be responsible for triggering tumor growth and resistance in a number of malignancies including breast, ovarian, gastric, esophageal and bladder cancers. The two studies were presented in poster sessions at the European Society for Medical Oncology (ESMO) in Vienna, Austria. To view the multimedia assets associated with this release, please click: http://www.multivu.com/mnr/58387-merrimack-pharmaceuticals-erbb3-cancer-therapy-esmo-2012-congress The separate studies were testing the safety profiles of (1) MM-121, developed in collaboration with Sanofi, in a combination regimen with weekly paclitaxel in advanced metastatic breast and ovarian cancers and (2) MM-111 in multiple HER2-Targeting regimens in advanced HER2 positive (ErbB2+ or HER2+) solid tumors. Each study demonstrated a promising clinical benefit rate for the MM-121 and MM-111 combination regimens, a secondary endpoint for each of the studies. MM-121 and MM-111 each employ their own unique mechanisms to stop ligand-driven activation of ErbB3 from signaling the cancer cell to grow. "We are pleased to see signs of clinical benefit in our studies with MM-121 and MM-111 across a broad range of solid tumors in patients who have progressed on standard of care therapies," said Robert J. Mulroy, President and Chief Executive Officer, Merrimack Pharmaceuticals. "Both candidates emerged from our Network Biology research engine, in which we identified ErbB3 as a central growth signaling node. Given their unique approaches to targeting ErbB3 biology, we believe that MM-121 and MM-111 are important therapies to advance the treatment of cancer and we are excited to watch them progress through clinical development." A Phase 1 Study of the Anti-ErbB3 Antibody MM-121 in Combination with Weekly Paclitaxel in Patients with Advanced Gynecologic and Breast Cancers (Abstract #: 974PD) The study evaluated MM-121, a fully human monoclonal antibody, in combination with weekly paclitaxel, a standard regimen for patients with advanced gynecological and metastatic breast cancers.