Nov 14 (Reuters) - The U.S. Food and Drug Administration

said on Friday it approved new labeling for Sarepta

Therapeutics' ( SRPT ) gene therapy Elevidys that includes its

most serious safety warning and restricts use of the treatment

to walking patients with Duchenne muscular dystrophy.

The agency added a boxed warning to the therapy after two

non-ambulatory pediatric patients died from acute liver failure

following treatment. The new label removes approval for use in

non-ambulatory patients entirely, limiting the drug to

ambulatory patients aged four and older.

In July, Sarepta voluntarily paused distribution of the $3.2

million gene therapy for non-ambulatory patients after the FDA

issued a safety communication following the deaths.

The label changes significantly narrow the patient

population eligible for Elevidys.

Elevidys is a one-time therapy that uses adeno-associated

virus vectors to deliver a shortened version of the dystrophin

gene - called micro-dystrophin - into muscle cells to help

protect and strengthen muscles in patients with Duchenne

muscular dystrophy, a rare and fatal muscle-wasting disease.

The FDA's label revision comes after what has been a year

filled with challenges for Sarepta. The company has grappled

with disappointing clinical trial outcomes, safety concerns tied

to Elevidys and falling sales, all of which have pressured its

financial performance.

The new labeling includes recommendations for weekly liver

function tests for at least three months after treatment and

advises patients to remain near an appropriate medical facility

for at least two months after taking Elevidys.

The FDA is also requiring Sarepta to conduct an

observational study with periodic liver function assessments,

enrolling approximately 200 DMD patients who will be followed

for at least 12 months after receiving Elevidys.

DMD affects roughly one in 3,500 to 5,000 male births

worldwide, according to Johns Hopkins data. Most patients lose

the ability to walk during their teenage years.