Merrimack halts Phase II breast cancer trial

Merrimack Pharmaceuticals Inc. (NASDAQ:MACK) sank $0.99 (18%) to $4.38 on Wednesday after stopping the Phase II HERMIONE trial of MM-302 to treat HER2-positive metastatic breast cancer. The company said it conducted a futility analysis after an independent DSMB concluded that continuing the study was not likely to show a benefit over comparators.

Merrimack said the futility assessment showed that both the MM-302 and control arms had shorter than expected median progression-free survival (PFS). There were no new or unexpected safety issues...