Sarepta has tested eteplirsen in 12 boys so far and is ramping up studies as it moves toward approval from the Food and Drug Administration, expected next year.
“Eteplirsen may hold the promise to change the face of this terrible disease and allow these boys the possibility of a different outcome than they would expect without treatment,” said Chris Garabedian, the company’s chief executive.
The event marked a milestone for the biotech company because it came less than a year after the FDA said it would be premature for Sarepta to submit a new-drug application for eteplirsen. The decision was a serious blow that disappointed patients and their families, as well as investors.
The FDA became wary of Sarepta’s drug after seeing poor results from a competing experimental treatment — called drisapersen — even though that drug has a different chemistry, Garabedian said.
“The most difficult part,” he said of the setback, “was keeping the employees motivated, keeping morale up in a time of uncertainty. When you don’t know what the pathway’s going to be, that can be difficult for employees.”
In April, the FDA changed its position and indicated it would consider allowing eteplirsen to be sold after more tests were done.
Sarepta is planning to expand from one clinical trial to six, enrolling more than 100 new patients. Two of the studies will test drugs that are similar to eteplirsen but work for different subsets of boys with Duchenne. Eteplirsen is designed to help the 13 percent of Duchenne patients who have a particular genetic mutation.
Duchenne muscular dystrophy afflicts about 1 in every 3,500 boys worldwide, destroying their muscle function over time. Boys with Duchenne are missing a crucial protein called dystrophin. They typically lose their ability to walk in their teen years, and most do not live past their twenties.
McSherry called Sarepta’s progress on drug development “a new beginning” for families struggling with the disease. She hopes eteplirsen will help stabilize her son’s condition.
Jett, who gets around in a wheelchair, is graduating from Pembroke High School this month and wants to study history at Bridgewater State University, as long as he can receive treatment locally.
“It might slow down the progression of the disease, just make me feel better overall,” Jett said of eteplirsen.
Results from Sarepta’s first and ongoing trial showed stability in patients’ lung function and their ability to walk. New trials will include patients like Jett, who can no longer walk.
Sarepta, formerly based in Seattle, began moving to locations scattered around Cambridge in 2013. It has consolidated those operations in 45,000 square feet of office and laboratory space at 215 First St.
Last month, the company said it would pay $25 million for an Andover manufacturing facility where it plans to produce drugs.
Sarepta has 160 employees, including 90 in Cambridge. Its Massachusetts workforce may double over the next year, Garabedian said.