Merrimack Pharmaceuticals has been saying for some time that the Phase 2 studies of its cancer drug, MM-121, while missing their goals, have been helping it find the right groups of patients for a late-stage trial. Apparently, however, Sanofi isn’t buying that thesis.
Merrimack (NASDAQ: MACK) said today that Sanofi has returned worldwide rights to MM-121 back to the Cambridge, MA-based company. Sanofi will continue to fund the Phase 2 trials Merrimack is running for MM-121—which include a breast cancer study that produced top-line results today—over the next six months. Afterwards, Merrimack will either have to find a new partner to help develop MM-121, or pick up the tab for a Phase 3 clinical study.
Sanofi first picked up the rights to MM-121, a cancer antibody targeting ErbB-3, a receptor on the surface of cancer cells, from Merrimack in 2009. Merrimack then set up an ambitious program to test it. The company put together a series of trials including about 1,000 patients total to test MM-121 as a first- and second-line treatment in ovarian, breast, and lung cancer.
Merrimack, for its part, has said that it didn’t expect all of these studies to succeed. Instead, it’s said that it’s been hoping to use these trials to find out not just if MM-121 works, but if diagnostics can accurately predict who should take it—and who shouldn’t—with the idea of designing a cheap, efficient late-stage trial to test the drug.
Over that time, MM-121 has failed trials in ovarian and lung cancer, and after data came out today from the last trial in the program, a breast cancer study, Sanofi decided to walk. Still, Merrimack said today that the trials helped it identify a biomarker associated with poor responses to standard of care therapies, and that MM-121 might help these patients. Indeed, CEO Bob Mulroy said in a statement that Merrimack will continue developing MM-121, that the drug has a chance to be a “foundational therapy across multiple solid tumor types,” and that the company will look to continue developing it with the help of “subsequent strategic partnerships.”
“We are grateful for Sanofi’s support over the last five years and believe that the data generated through this partnership validate the potential for MM-121 to help patients most at risk for progression on current therapies. Regaining MM-121 is an opportunity to capitalize on our leadership position among the other oncology companies that are pursuing ErbB3,” Mulroy said in a statement.
Merrimack slumped about 13 percent in after-hours trading. The company, however, is just a few months removed from reporting positive results in pancreatic cancer for another drug candidate, MM-398. Merrimack has said it plans to file a new drug application with the FDA based on the data.
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