Sanofi, Merrimack cancer drug flops (again) in second round of PhII program

Seven months after a mid-stage cancer drug from Sanofi and Merrimack Pharmaceuticals flunked its first mid-stage test, researchers are back with another failure to report. The Cambridge, MA-based biotech said that MM-121 (SAR256212), partnered with Sanofi ($SNY) in a $530 million deal, failed to hit the primary endpoint on progression-free survival for ovarian cancer when combined with Taxol. Once again, though, the investigators are pointing to a subpopulation that benefited from the drug.

Shares of Merrimack ($MACK) plunged 20% on the news, with the market cap shrinking to about $277 million. For the year the stock is down 45%.

Back in April the biotech reported that a cohort of 50 patients suffering from non-small cell lung cancer patients in a 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."

This time around investigators reported that a "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]."

"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, co-founder and VP 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." 

Merrimack, a 2011 Fierce 15 company, went public last year, but only after offering a big discount on the share price.

- here's the release

Special Report: 2011 Fierce 15 - Merrimack Pharmaceuticals