U.S. FDA spurns Sanofi, Regeneron arthritis drug over manufacturing lapse

(Adds details on FDA letter, background on sarilumab)

Oct 28 (Reuters) - Sanofi SA and Regeneron Pharmaceuticals Inc on Friday said U.S. regulators had declined to approve their experimental treatment for rheumatoid arthritis because of manufacturing deficiencies.

The companies, in a release, said the U.S. Food and Drug Administration identified the deficiencies during a routine inspection of a Sanofi plant in France where the drug, sarilumab, is filled and finished, one of the last steps in the manufacturing process.

Sanofi said it had submitted a comprehensive correction plan to the FDA and is taking corrective actions. The FDA did not cite any safety concerns in its notice to the drugmakers, called a complete response letter, the companies said.

Sarilumab, meant for adult patients with moderate to severe rheumatoid arthritis, works by blocking a protein called IL-6 that is associated with inflammation. The companies had been expecting the FDA to make a decision on the injectable treatment by Oct. 30.

In a large clinical trial of rheumatoid arthritis patients who had failed to benefit from the standard treatment methotrexate, sarilumab was shown to be superior to AbbVie Inc's top-selling Humira in improving signs and symptoms of disease.

Other IL-6 inhibitors for rheumatoid arthritis include Roche Holding AG's approved Actemra and Johnson & Johnson's experimental sirukumab, now awaiting FDA approval.

Regeneron shares, which had been halted ahead of the drugmakers' announcement, were down 2.8 percent after trading resumed late Friday.

(Reporting by Ransdell Pierson; Editing by Chris Reese)