Sanofi, Merrimack rack up third straight failure for lead cancer drug

Merrimack Pharmaceuticals and its partners at Sanofi ($SNY) are back with another trial failure to report on the biotech's lead drug, MM-121. Combined with exemestane, the drug failed to improve progression-free survival among a group of ER/PR+, HER2 negative breast cancer patients. This is the third such setback for the program, though investigators quickly attempted to shift attention to indications that certain subpopulations benefit while another study provided indications of a positive effect on pathologic complete responses when compared with the control arm.

A few weeks ago Merrimack ($MACK) reported that MM-121 had failed to hit the PFS mark for ovarian cancer. And back in April, there was a flop for lung cancer. But in every case, the biotech pounced on an improved understanding of the biomarkers involved and signs of promise in breaking down the cancer groups into particular subpopulations.

That may not be much comfort for Sanofi, though, which has had to wrestle this year with a series of setbacks for its oncology R&D division. A few days ago, the pharma giant had to shutter a program for fedratinib after the FDA ordered a clinical halt when myelofibrosis patients developed Wernicke's encephalopathy--a neurological condition spurred by biochemical brain lesions. And earlier in the year iniparib was a total writeoff after back-to-back Phase III failures for lung cancer.

Sanofi CEO Chris Viehbacher made oncology a top priority when he stepped in as CEO 5 years ago.

Merrimack, though, shows no signs of throwing in the towel. The company reported that its combo for metastatic breast cancer patients may have failed the primary endpoint but it was happy to see confirmatory suggestions of success for patients with a specific biomarker profile.

"The biomarker results of this study support the hypothesis that ErbB3 signaling is an important pathway of resistance for some breast and ovarian cancers," said Dr. Michaela Higgins, assistant professor of medicine at Harvard Medical School and Massachusetts General Hospital Cancer Center and principal investigator on this study. "The data from this study suggest that MM-121 may enhance response to standard-of-care therapy among patients whose tumors are dependent on this pathway."

The second study found that patients taking a combination of MM-121 and paclitaxel achieved a pathologic complete response rate of 10.8% compared to 3.3% in the control arm. There was no primary endpoint set for this study, though.

Sanofi paid Merrimack $60 million upfront to partner on MM-121 back in 2009, adding in $470 million in promised milestones. Merrimack, a 2011 Fierce 15 company, went public last year but was forced to take a heavily discounted price for its shares.

In a separate release Tuesday morning, Merrimack also unveiled a collaboration with Actavis, which is paying $2 million upfront and promising up to $13.5 million more to get Merrimack to put its nanoliposomal tech platform to work for the specialty pharma company. The deal might explain why Merrimack's battered shares are up more than 10% this morning.

- here's the release on MM-121
- here's the release on the nanotech deal

Special Report: 2011 Fierce 15 - Merrimack Pharmaceuticals

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