Merrimack Pharmaceuticals Inc said one of three patient groups in a mid-stage trial of its experimental lung cancer drug failed to meet the main goal of improving survival rates after four months of treatment without the disease worsening.
The company's shares fell 7 percent in premarket trade.
The group was administered the drug, MM-121, in combination with erlotinib, an approved cancer treatment, for non-small cell lung cancer.
Erlotinib is marketed as Tarceva by Swiss drugmaker Roche Holding AG.
The main goal of the study was to show that 40 percent of the 50-patient group experienced a progression-free survival after four months.
The drug is also being evaluated in two other lung-cancer patient groups, and in separate studies for ovarian and breast cancer.
Another cancer drug from the company, MM-398, is being tested in a late-stage trial for pancreatic cancer.
It is also being tested as a treatment for glioma and colorectal cancer.
Shares of the company, which went public in March 2012, were down 7 percent at $5.75 in trading before the bell. They closed at $6.21 on the Nasdaq on Wednesday.
(Reporting by Esha Dey in Bangalore; Editing by Sriraj Kalluvila)