Merrimack Pharmaceuticals Announces Results From A Phase 2 Study Of MM-121 (SAR256212) In Combination With Paclitaxel In Patients With Platinum-Resistant Or Refractory Advanced Ovarian Cancers

CAMBRIDGE, Mass., Oct. 30, 2013 /PRNewswire/ -- Merrimack Pharmaceuticals, Inc. (NASDAQ:MACK) today announced results of a global, Phase 2, open-label, randomized study of MM-121 in combination with paclitaxel versus paclitaxel alone in patients with platinum-resistant or platinum-refractory advanced ovarian cancers.

This study did not meet the primary endpoint of progression free survival in the overall population.  The hazard ratio (HR) for progression free survival (PFS) was 1.0 [95% CI 0.74 - 1.4].

Ongoing analysis of a pre-specified set of biomarkers mechanistically linked to ErbB3 signaling identified a potential subpopulation of patients benefiting from MM-121 treatment in combination with paclitaxel. When using a combination of two biomarkers, the hazard ratio for PFS was 0.37 [95% CI 0.2 - 0.8] in the 34% of patients who were biomarker positive. The hazard ratio for PFS in the biomarker negative population was 1.54 [95% CI 1.0 - 2.4].

An overall increase in all grades of gastrointestinal toxicities, including diarrhea (73.6% vs. 42.5%), vomiting (31.4% vs. 18.8%) and other mucosal toxicities such as rhinitis (7.1% vs. 1.3%), epistaxis (23.6% vs. 17.5%), stomatitis (22.1% vs. 10.0%) and mucosal inflammation (22.1% vs. 1.3%), were observed in the combination as compared to paclitaxel alone, the majority of which were mild to moderate in severity. An increase in the pulmonary embolism rate was observed with the combination of MM-121 and paclitaxel (5.0% vs. 1.2%). No enhancement of paclitaxel-related peripheral neuropathy was reported with the combination.

"This unique study design lays the groundwork for future translational studies in ovarian cancer. The rapid enrollment into this study was a testament to the commitment of patients and physicians to advance our knowledge and improve upon available therapies in advanced ovarian cancers," said Dr. Akos Czibere, Clinical Director of the MM-121 program at Merrimack. "These data are a step forward for women with ovarian cancer." 

"Research at Merrimack and elsewhere has shown that ligand-driven signaling through ErbB3 is one way in which cancer cells become resistant to therapy," said Gavin MacBeath, Ph.D., Co-Founder and Vice President of Translational Research at Merrimack. "MM-121 was designed to block this pathway. We are particularly encouraged by the biomarker findings in this trial, which are consistent with our preclinical hypotheses. This gives us increased confidence in our network biology platform and in our translational program at Merrimack."

This study was designed to evaluate whether MM-121 in combination with paclitaxel is more effective than paclitaxel alone, based on progression free survival. Patients were randomized at a 2:1 ratio for MM-121 in combination with paclitaxel versus paclitaxel alone. The study was conducted in the United Stated and Europe, and 223 patients were randomized. Patients enrolled in this study had locally advanced/metastatic or recurrent epithelial ovarian cancer, fallopian tube cancer or primary peritoneal cancer, had received at least one prior platinum-based chemotherapy regimen, and were platinum-resistant or refractory. The full data from the study will be presented at a future conference.

MM-121, in partnership with Sanofi, is also being evaluated in second line ER/PR+ metastatic breast cancer, ER/PR+ neoadjuvant breast cancer, triple-negative neoadjuvant breast cancer and non-small cell lung cancer.

About MM-121

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 is designed to restore sensitivity, delay resistance and enhance the anti-tumor effect of a combination therapy partner. Sanofi and Merrimack entered into an exclusive, global license and collaboration agreement for MM-121 in 2009.

About Merrimack Pharmaceuticals, Inc.

Merrimack is a biopharmaceutical company discovering, developing and preparing to commercialize innovative medicines paired with companion diagnostics for the treatment of cancer. Merrimack applies its systems biology-based approach to biomedical research throughout the research and development process. Merrimack currently has six oncology therapeutics in clinical development.

Forward-Looking Statement

To the extent that statements contained in this press release are not descriptions of historical facts, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements include any statements about Merrimack's strategy, future operations, future financial position and future expectations and plans and prospects for Merrimack, and any other statements containing the words "anticipate," "believe," "estimate," "expect," "intend," "may," "plan," "predict," "project," "target," "potential," "will," "would," "could," "should," "continue," and similar expressions. In this press release, Merrimack's forward-looking statements include statements about the potential effectiveness of MM-121 in combination with paclitaxel in certain patient populations or subpopulations, its ability to develop a predictive diagnostic and its ability to translate clinical data into future clinical success. Such forward-looking statements involve substantial risks and uncertainties that could cause Merrimack's clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the initiation of future clinical trials, availability of data from ongoing clinical trials, expectations for regulatory approvals and other matters that could affect the availability or commercial potential of Merrimack's drug candidates or companion diagnostics. Merrimack undertakes no obligation to update or revise any forward-looking statements. Forward-looking statements should not be relied upon as representing Merrimack's views as of any date subsequent to the date hereof. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Merrimack's business in general, see the "Risk Factors" section of Merrimack's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on August 8, 2013 and other reports Merrimack files with the SEC.

SOURCE Merrimack Pharmaceuticals, Inc.