US FDA asks Stealth BioTherapeutics to resubmit application for rare genetic condition therapy

May 29 (Reuters) - The U.S. Food and Drug Administration has asked for a resubmission of Stealth BioTherapeutics' marketing application for its experimental therapy targeting a rare genetic condition, Barth syndrome, the company said on Thursday.

The drug developer added that it has implemented a 30% workforce reduction to conserve resources for a potential resubmission.

The federal health regulator's decision marks another setback in Stealth's prolonged effort to bring the therapy, elamipretide, to market after several delays.

Stealth received the FDA's so-called 'complete response letter' after a 16.5-month review, during which the FDA extended its review from January to April to assess additional data. Last month, the regulator missed the extended deadline.

The Needham, Massachusetts-based company is seeking approval for elamipretide, a potential treatment for Barth syndrome - a condition that typically affects boys and causes heart, muscle weakness and delays growth.

Stealth had submitted data from a mid-stage trial, which showed improvement in knee muscle strength, which was correlated with improvements on the six-minute walk test.

The FDA has agreed to consider knee extensor muscle strength, for which the company previously submitted data, as a goal to support accelerated approval, the company said.

However, the regulator is hesitant to extend the accelerated pathway to critically ill newborns, who make up nearly two-thirds of the therapy's expanded access program participants.

Barth syndrome affects fewer than 150 individuals in the United States and fewer than 300 worldwide, and currently, no approved therapies exist.