After a series of late-stage failures, Sanofi has returned the rights to the cancer compound MM-121 to Merrimack Pharmaceuticals.

MM-121, a monoclonal antibody designed to block ErbB3 activation in patients with heregulin-positive tumours, has been tested in Phase II trials in partnership with the French giant in ovarian, breast and lung cancer. However, none of them have met their primary endpoints and Sanofi has decided  to pull the plug, although it will continue to fund the existing MM-121 Phase II programme for the next six months.

Merrimack is still optimistic and chief executive Robert Mulroy believes the data generated from these trials “validate the potential for MM-121 to help patients most at risk for progression on current therapies”. He added that getting back the rights “is an opportunity to capitalise on our leadership position among the other oncology companies that are pursuing ErbB3”.

Mr Mulroy said that with these data “and the feedback we've received from our committed investigators, we believe MM-121 has the potential to be a foundational therapy for use across multiple solid tumour types, and we plan to continue its development through subsequent strategic partnerships”. He concluded by saying that the next step is to “discuss our Phase II data and potential registration paths with the FDA”.