Merrimack's lead cancer drug flunks first of three PhII tests

Merrimack Pharmaceuticals ($MACK) has nailed down the top-line results for one group of cancer patients in a mid-stage trial of Tarceva combined with its lead drug MM-121, partnered with Sanofi ($SNY). And it's not good.

Investigators say that the cohort of 50 patients suffering from non-small cell lung cancer patients in the single arm study failed to hit the primary endpoint of a 40% progression-free survival rate at four months. This particular cohort was made up of a group whose disease had "progressed on an anti-EGFR tyrosine kinase inhibitor." Two other cohorts--"patients with EGFR wild-type tumors who have recurring or progressive disease following at least one chemotherapy-containing regimen in the metastatic setting and who have had no prior EGFR-TKI therapy (Group A) and patients with a known EGFR-activating mutation who have had no prior EGFR-TKI therapy in the metastatic setting (Group B)"--are still being evaluated.

The researchers, though, cautioned that the study nevertheless helped advance its understanding of the ideal biomarker profile needed to identify patients most likely to respond.

"A strong component of these studies is a focused translational program directed toward the identification of a biomarker profile for the combination in this difficult to treat cancer," said Dr. Akos Czibere, senior medical director of the MM-121 program at Merrimack. "We are disappointed by the overall clinical results in this population, but are encouraged by our preliminary biomarker analysis which we believe will be important for the identification of a predictive diagnostic when analyzed in the context of the overall clinical development program."

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.

MM-121--an antibody that targets ErbB3, a cell surface receptor implicated in tumor growth and survival--is also engaged in other Phase II studies for other types of cancer.

- here's the press release

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