Merrimack Pharma’s stock plunges (again) on its latest cancer drug trial flop

Richard Peters

Merrimack Pharmaceuticals $MACK has another loser on its hands.

The drug MM-121 (seribantumab) added to docetaxel did not do any better than docetaxel alone in improving the progression-free survival of patients suffering from non-small cell lung cancer.

Merrimack’s stock, already blighted by trial failure, quickly plunged anew, dropping more than 30% on the latest setback. The stock was trading at around $3.50 mid-morning. 

In the summer of 2015 it was over $120.

The company is once again putting a drug on death watch as it reviews their therapy’s prospects in another mid-stage study for heregulin positive, hormone receptor positive, ErbB2 (HER2) negative, metastatic breast cancer. The implication is that Merrimack may soon by a 1-drug company, which won’t improve investors’ satisfaction.

Last summer the company buried MM-141 (istiratumab) after it failed a Phase II pancreatic cancer study in which investigators paired it with nab-paclitaxel and gemcitabine against the standard combo alone. The company said the drug flat failed on the primary and secondary endpoints, with nothing encouraging to report in the subgroup analysis.

The company still has hopes for MM-310, though, two years after it restructured and sold off its one commercial product.

“Our ability to make a swift decision regarding these results is based on our development approach of testing our targeted therapies in biomarker-defined patient populations, which allows us to accelerate the timeframe needed to obtain clear data read-outs,” said CEO Richard Peters. “The data provide a definitive signal that MM-121 does not improve clinical outcomes for patients with non-small cell lung cancer and, in line with this efficient development strategy, we plan to look closely at the data as we assess the continued development of MM-121 and evaluate our pipeline more broadly.”

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Sr. Manager, Regulatory Affairs, CMC
CytomX Therapeutics San Francisco, CA
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