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# FDA Grants, Denies Catalyst Amifampridine Petition
- URL: https://www.fdaweb.com/fda-grants-denies-catalyst-amifampridine-petition/
- Published: 2022-09-15T12:00:00.000Z
- Updated: 2026-09-14T17:59:30.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5152752

FDA has granted in part and denied in part a Catalyst Pharmaceuticals 7/8/21 petition asking the agency not to consider any NDA to use amifampridine to treat congenital myasthenic syndromes (CMS) approvable based on a mechanistic argument of efficacy and to require the NDA to include well-controlled, randomized clinical trials as evidence of efficacy and safety. The petition also asked FDA to issue guidance with several of the company’s recommendations.

The FDA [letter](https://downloads.regulations.gov/FDA-2021-P-0705-0004/attachment%5F1.pdf?ref=fdaweb.com) says cases of CMS vary in their clinical features and their response to treatment. “Because of the heterogeneity in the phenotypes and genotypes of congenital myasthenia,” it says, “FDA does not currently have evidence that a mechanistic rationale alone would be sufficient for the approval of a drug to treat CMS. We decline, however, to state that a mechanistic argument of efficacy could never provide evidentiary support for the treatment of CMS of genetic origin with amifampridine. The agency will consider any NDA for amifampridine for treatment of CMS on a case-by-case basis.”

FDA also declined to issue guidance at this time with recommendations on how to structure clinical trials studying genetic subtypes of CMS. It says it will continue to provide advice to sponsors on a case-by-case basis.