An experimental treatment for Duchenne muscular dystrophy has failed a mid-stage study, and Summit Therapeutics said Wednesday it is now stopping work on the drug. Summit shares plunged nearly 80 percent on the news.
Duchenne is an inherited disorder found mainly in boys that causes progressive muscle weakness. The Summit (NASDAQ: SMMT) drug, ezutromid, was developed to increase production of a protein called utrophin. By increasing utrophin, Summit hoped its small molecule drug could help Duchenne patients compensate for the lack of dystrophin, another protein that is key to healthy muscle function.
Summit enrolled 40 boys in the open-label Phase 2 study. The company, which is based in Oxford, U.K. and has additional operations in Cambridge, MA, said that the measures of muscle improvement observed after 24 weeks of treatment were not sustained through the end of the 48-week study.
Ezutromid’s clinical trial failure is also a blow to Cambridge-based Sarepta Therapeutics (NASDAQ: SRPT). In 2016, Sarepta entered into a collaboration with Summit, paying its partner $40 million up front, and committing up to $522 million more, for partial rights to ezutromid and other Summit drugs that modulate utrophin. Under the deal, Sarepta also shouldered 55 percent of Summit’s utrophin drug research starting this year. The Summit drugs could have complemented Sarepta’s FDA-approved Duchenne drug eteplirsen (Exondys 51), which helps patients produce dystrophin.
Following the failure of its Duchenne drug, Summit says it will now turn its focus to antibiotics in its pipeline. Summit expects to bring its lead antibiotic candidate, ridinilazole, into Phase 3 studies in the first quarter of next year, testing it as a treatment for C. difficile infection.