Merrimack presents encouraging preclinical research with MM-121 in ER-positive breast cancer model

USA-based Merrimack Pharmaceuticals (Nasdaq: MACK) has 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.

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.

Earlier this month, Merrimack reported that one cohort of a Phase II non-small cell lung cancer study with MM-121 did not meet its primary endpoint. The cohort evaluated MM-121 in combination with erlotinib to treat patients with non-small cell lung cancer whose disease progressed on an anti-EGFR tyrosine kinase inhibitor.