Catalyst hits an FDA roadblock with its 'breakthrough' rare disease drug

The FDA has declined to consider Catalyst Pharmaceuticals' ($CPRX) drug application, issuing a rare "refusal to file" letter and demanding the company submit more information on its treatment before coming back.

The agency's letter said Catalyst's application for the rare disease drug Firdapse "was not sufficiently complete," according to the company, and requested more supporting information. That doesn't amount to a ruling on Firdapse's supporting efficacy and safety data, Catalyst said, but it does throw the drug's timeline for approval into doubt. The company has promised to "request a meeting with the FDA as soon as possible" to figure out how to move forward.

The news sent the Coral Gables, FL-headquartered Catalyst's share price down more than 40% on Wednesday morning, seeming to dash investors' hopes that the company's lead drug might win approval.

Firdapse is meant to treat Lambert-Eaton myasthenic syndrome (LEMS), a rare neuromuscular disease that gradually robs patients of their mobility. In 2013, the drug picked up the FDA's coveted breakthrough therapy designation, guaranteeing Catalyst preferred access to top agency officials throughout the development process. A year later, Firdapse met its primary goals in a Phase III trial on 38 LEMS sufferers, setting the stage for Catalyst's FDA submission.

The FDA has the authority to refuse to file a company's drug application when it spots deficiencies that might delay the review process and thus stop the agency from meeting its efficiency goals. Such refusals are not based on qualitative conclusions about drug data, but they tend to be bad omens for applicants.

In 2011, the FDA refused to consider Pfizer's ($PFE) application for the rare disease treatment tafamidis. Pfizer marshaled the necessary information and returned to regulators only to be handed an outright rejection a year later. PTC Therapeutics ($PTCT) ran into the same roadblock with its Duchenne muscular dystrophy treatment in 2012, eventually giving up its effort to win early approval and embarking on a Phase III program, which failed last year.

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