Sarepta shares up 140 percent on positive data from Phase IIb trial of Duchenne muscular dystrophy drug

Shares in Sarepta Therapeutics soared more than 140 percent Tuesday after the company announced that its experimental exon-skipping compound, eteplirsen, achieved the primary endpoint in a Phase IIb trial in patients with Duchenne muscular dystrophy (DMD). "This result represents a major advance in the pursuit of a disease modifying treatment for this severe, progressive and life-threatening disease," remarked principal investigator Jerry Mendell.

Study 4658-US-201 assigned 12 boys aged 7 to 13 years with the appropriate deletions of the dystrophin gene to receive intravenous infusions of one of two doses of eteplirsen or placebo once weekly for 24 weeks. In an extension study, dubbed Study 4658-US-202, the four patients given placebo were rolled over at 24 weeks to receive one of two doses of the eteplirsen for 12 weeks. Patients assigned to receive eteplirsen in the first study continued to receive doses at their pre-assigned level.

In the primary clinical outcome of a 6-minute walk test, patients given the higher dose of eteplirsen demonstrated a decline of 8.7 meters in distance walked from baseline, versus a decline of 78 meters for patients who received placebo followed by delayed-eteplirsen treatment. The company noted that this amounts to a statistically significant treatment benefit of 69.4 meters over 36 weeks. The benefit observed in the highest-dose treatment cohort compared to placebo was also significant at week 32, with a benefit of 59.9 meters, Sarepta said.

Mendell commented that "the magnitude of this clinical benefit is an unprecedented treatment effect in DMD." There was no statistically significant difference between the cohort of patients on the lower weekly dose of eteplirsen and the placebo/delayed-treatment cohort. Further, the company noted that no treatment-related changes were detected on any safety parameters, including several biomarkers for renal function.

Sarepta, which was formerly known as AVI Biopharma, said it will continue to follow the patients in the study and expects to have updated results after 48 weeks of treatment ready for presentation at a medical conference in October. The company indicated that if the benefit is confirmed at 48 weeks, it will meet with the FDA to discuss regulatory options.

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