(Reuters) – Sarepta Therapeutics Inc’s shares surged on Wednesday after the results of a trial on its drug to treat a fatal muscle-wasting disease showed it had the potential to be more effective than the company’s approved drug for the same disease.

Duchenne Muscular Dystrophy is a rare and progressive genetic disorder that hampers muscle movement and Sarepta said its drug was successful in boosting the production of dystrophin, a protein that helps keep muscles intact.

At least two analysts said the amount of dystrophin produced by the investigational drug, golodirsen, was more than the amount produced by Exondys 51, Sarepta’s other DMD drug that was controversially approved a year back.

Golodirsen led to an eleven-fold improvement in the mean dystrophin increase in patients, almost three times the improvement seen with Exondys, William Blair analyst Timothy Lugo told Reuters.

“We anticipate the FDA will be eager to bring golodirsen to the market given the lack of alternative treatment options,” Lugo said.

Sarepta’s shares surged as much as 14 percent on Wednesday, before easing to trade up 9 percent to $44.83 in late morning trading.

DMD, which affects about one in every 3,500 to 5,000 males, happens when an exon, or exons – one of the vital parts that make a gene – are deleted or absent, interfering with the rest of the gene being pieced together.

Golodirsen is for patients who are amenable to what is known as exon 53 skipping, a subset of overall DMD patients. It works by skipping the deleted exon, allowing the remainder to join and form a complete gene.

Sarepta said all 25 patients in the early-stage trial displayed an increase in skipping exon 53. Golodirsen uses the same exon-skipping platform used for Exondys 51, which helps complete a gene by skipping exon 51.

“Golodirsen does appear to be a more proficient exon skipper than Exondys 51,” Leerink analyst Joseph Schwartz wrote in a client note.

About 8 percent of all DMD patients are amenable to exon 53 skipping, compared with 13 percent for exon 51, Lugo said. He estimated if Sarepta prices the drug at parity with Exondys 51, sales could top $800 million by 2022.

Exondys 51 was approved in September last year after the U.S. Food and Drug Administration bowed to patient pressure and went against the recommendation of its top scientists and a panel of outside advisers.

(Reporting by Divya Grover in Bengaluru; Editing by Savio D’Souza)