Merrimack's String of Failures Continues With Lung Cancer Study Shelved After Midstage Trials

Merrimack Pharmaceuticals Inc MACK shares were trading at record lows Friday and were down 32.85 percent at $3.46 at the time of publication. 

What Happened

Merrimack, which focuses on therapies for biomarker-defined cancer, said it has terminated a study dubbed SHERLOC, which evaluated its MM-121 in combination with docetaxel in patients with heregulin-positive non-small cell lung cancer, or NSCLC.

Docetaxel is a chemotherapy medication used to treat several cancers, including breast cancer, head and neck cancer, prostate cancer and NSCLC.

The decision was made after the Independent Data Safety Monitoring Board that evaluated the data from the Phase 2 trial found that the addition of MM-121 to docetaxel did not improve progression-free survival over docetaxel alone in the patient population.

The safety profile was consistent with MM-121's previously reported safety profile, the company said.

Why It's Important

Merrimack's pipeline now consists of two candidates in clinical trials: MM-121, which is being tested in two separate Phase 2 trials for HRG-positive NSCLC as well as HRG-positive, HR-positive and HER2-metastatic breast cancer, and MM-310, a novel antibody-directed nanotherapeutic targeting EphA2 receptor currently in a Phase 1 trial.

The setback is likely to hurt the stock, as MM-121 for HER-positive NSCLC is the most advanced asset in Merrimack's pipeline.

It is all the more important because the company was forced to shelve two Phase 2 studies — one in December 2016 and another in June 2018 — following failed trials.

What's Next

Based on the results of the SHERLOC study, the company said it will comprehensively review its drug pipeline, with a specific focus on the SHERBOC study, which is evaluating MM-121 in combination with fulvestrant for HRG-positive, HR-positive and HER2-metastatic breast cancer.

Merrimack also said it will provide an update on its pipeline and the results of its portfolio review on its third-quarter earnings call Nov. 7.

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