The U.S. Food and Drug Administration has placed Astellas Pharma’s Phase I/II FORTIS trial on clinical hold after one of its study participants suffered a serious adverse event (SAE).

The study, which is assessing the investigational adeno-associated virus gene replacement therapy AT845 in adults with late-onset Pompe disease, reported peripheral sensory neuropathy in one of the patients. The SAE was classified as Grade 1, or mild in severity, but it was considered serious because it is medically significant.

AT845 is a gene replacement therapy that uses an AAV8 vector to deliver a functional copy of the acid alpha-glucosidase (GAA) gene to treat late-onset Pompe disease. The FDA said Astellas did not submit adequate details to assess the risk of the drug to its participants, specifically regarding the SAE that surfaced. The regulator will send a comprehensive written explanation for its decision within the next 30 days.

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