Merrimack Pharmaceuticals, Inc. (NASDAQ: MACK) today announced Phase I clinical trial results for MM-302, the company's novel agent for the treatment of advanced HER2 positive (HER2+ or ErbB2+) breast cancer. The findings demonstrated preliminary safety and tolerability. A study of its potential companion imaging diagnostic was shown to predict treatment response in preclinical models. Data were presented at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium, Dec. 4-8, 2012 in San Antonio, Texas.
MM-302 is a nanotherapeutic encapsulation of the anthracycline chemotherapy agent doxorubicin with anti-HER2 antibody fragments attached to its surface. Anthracyclines have known cardiotoxicities which historically have restricted their use in combination with HER2-targeted therapies.
"We are highly encouraged by these results. MM-302 was engineered to be a more effective treatment than free doxorubicin and to address the safety concerns associated with the traditional chemotherapy," said Ulrik B. Nielsen, Co-Founder and Chief Scientific Officer, Merrimack Pharmaceuticals. "We've encapsulated doxorubicin in a liposomal membrane that is designed to travel through the blood to the tumor cell with limited uptake into normal tissue such as heart tissue. When it arrives at the tumor cell, the antibodies on the outside of the encapsulated medicine bind to the HER2 receptor and pull the medicine inside the cell, allowing the chemotherapy to be delivered locally within the tumor."
Merrimack is developing an image-based companion diagnostic, MM-DX-929, to predict response to liposomal chemotherapeutics, such as MM-302. A preclinical study presented at SABCS showed that tumor uptake of MM-DX-929 correlated well with treatment response to MM-302.
METHODOLOGY AND RESULTS
A Phase I Study of MM-302, a HER2-targeted Liposomal Doxorubicin, in Patients with Advanced, HER2-positive (HER2+) Breast Cancer (Abstract #: P5-18-09)