CAMBRIDGE, Mass., April 8, 2013 /PRNewswire/ -- Merrimack Pharmaceuticals, Inc. (NASDAQ: MACK) today announced preclinical study results showing that the novel therapy MM-121 restores tumor sensitivity and delays the onset of resistance to the aromatase inhibitor, letrozole, in an ER+ breast cancer model. The study was presented as part of the American Association for Cancer Research's 2013 Annual Meeting in Washington, DC, April 6-10, 2013.
MM-121 is a fully human monoclonal antibody that targets ErbB3, a cell surface receptor implicated in tumor growth and survival. By inhibiting ErbB3 signaling, MM-121 was found to restore sensitivity, delay resistance and enhance the anti-tumor effect of letrozole as a combination therapy partner.
"In nearly all cases of advanced ER+ breast cancer, endocrine therapies are initially effective, but patients eventually develop resistance to these treatments," said Gavin MacBeath, Co-Founder and Head of Translational Research, Merrimack Pharmaceuticals. "We are excited to see that in preclinical models, MM-121 blocked activation of its target, ErbB3, and down-regulated several signaling pathways within these tumors. We saw delayed resistance to letrozole when co-administered with the drug, and restored sensitivity when added after the tumors developed resistance to letrozole. These data help guide our thinking regarding how best to combine MM-121 with anti-hormonal therapies in the treatment of advanced ER+ breast cancer."
The activity of MM-121 alone and in combination with letrozole was measured in an MCF7 in vivo model of post-menopausal ER+ breast cancer engineered to express aromatase. Models of ER+ breast cancer were randomized to receive letrozole, MM-121 or both MM-121 and letrozole following development of resistance to letrozole. Tumors were harvested 24 hours after initiating treatment post-randomization and at the end of the study when all treatment arms developed resistance.
Sanofi and Merrimack entered into an exclusive, global license and collaboration agreement for MM-121 in 2009.
About Merrimack Pharmaceuticals, Inc.
Merrimack Pharmaceuticals is a biopharmaceutical company discovering, developing and preparing to commercialize innovative medicines paired with companion diagnostics for the treatment of cancer. Merrimack applies Network Biology, its proprietary systems biology-based approach to biomedical research, throughout the research and development process. Merrimack currently has six targeted therapeutic oncology candidates in clinical development.
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SOURCE Merrimack Pharmaceuticals, Inc.