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May 10 (Reuters) - Data presented for Sarepta Therapeutics Inc's experimental gene therapy for a muscle-wasting disorder did not provide unambiguous evidence that the treatment worked, the U.S. Food and Drug Administration's staff reviewers on Wednesday.

The company is seeking accelerated approval for the first gene therapy for Duchenne muscular dystrophy, based on data that showed it helped patients make a mini version of the dystrophin protein needed to keep muscle cells intact.

"Additionally, FDA has safety concerns related to the possibility of administering an ineffective gene therapy," the reviewers said in the briefing documents, ahead of a meeting of outside advisers to the drug agency on Friday.

(Reporting by Leroy Leo in Bengaluru; Editing by Sriraj Kalluvila)