Facing skepticism from U.S. and European regulators, Merck KGaA has given up efforts to gain approval for the oral immunosuppressant drug cladribine for multiple sclerosis, the company announced.
"We have decided to not pursue further the worldwide approval process of cladribine tablets and to focus resources on other projects bringing benefit to patients with multiple sclerosis," a Merck KGaA official said in a statement.
Cladribine is an established therapy for certain hematologic cancers and has shown significant efficacy as a treatment for MS. But it also had broader, long-lasting immunosuppressant effects that were worrisome in MS patients.
Last fall, the European Medicines Agency told the German company (which is not currently related to the U.S.-based firm Merck & Co.) that the submitted clinical data did not justify the drug's approval for MS.
In February, the FDA followed suit, sending a complete response letter indicating that Merck KGaA would have to submit new analyses or conduct new studies to satisfy its concerns about cladribine's safety and its risk-benefit balance.
"Merck believes that data from ongoing clinical trials are very unlikely to address the FDA requirements and will not provide a basis for approval," the company's statement said, adding that therefore it would have to conduct a new multiyear trial.
Because of "the time it would take to complete a new clinical trial program and the significant risk that even a new program would not result in data sufficient for cladribine tablets' approval," the firm decided instead to stop the program entirely.
In fact, the company added that it would withdraw cladribine as an MS treatment from two countries where it was already approved, Australia and Russia.
But it plans to continue three current MS trials with cladribine -- a 96-week CLARITY extension, ORACLE MS, and ONWARD -- and to follow patients who have participated in these and earlier studies.