ZURICH (Reuters) - The U.S. Food and Drug Administration (FDA) has extended its review of Roche’s multiple sclerosis (MS) drug Ocrevus by three months to March 28, the Swiss drugmaker said on Tuesday.

The logo of Swiss pharmaceutical company Roche is seen outside their headquarters in Basel, January 30, 2014. REUTERS/Ruben Sprich/File Photo

Roche is counting on Ocrevus becoming a mainstay treatment for patients suffering from the neurological disease to help bolster its revenue as other top selling drugs in its portfolio start to face competition from cheaper copies.

“The extension is the result of the submission of additional data by Roche regarding the commercial manufacturing process of Ocrevus, which required additional time for FDA review. The extension is not related to the efficacy or safety of Ocrevus,” Roche said in a statement.

“We are working closely with the FDA during their review and are committed to bringing this innovative medicine to the over 400,000 people with MS in the U.S. living with this disabling disease as quickly as possible,” said Sandra Horning, Roche’s chief medical officer and head of global product development.

Roche shares closed down 0.1 percent in Switzerland before the extension of the review was announced.

Roche has said that in its trials among relapsing-remitting multiple sclerosis (RRMS) patients, 75 percent more reached “no evidence of disease activity” status taking Ocrevus than those on Merck’s Rebif, a standard therapy.

Doctors also found no evidence of disease progression in a 47 percent higher proportion of primary progressive multiple sclerosis (PPMS) patients who got Ocrevus compared with those on a placebo. There are no approved treatments for PPMS patients.

Over the past year, Roche has accelerated its timeline for U.S. approval of Ocrevus after winning FDA fast-track review status for the drug, and the FDA had been due to give its ruling by Dec. 28.

Roche has said that European approval will take longer, probably not coming until the third quarter of 2017, as the drug did not benefit from the European Medicines Agency’s accelerated review program.

Also known as ocrelizumab, Roche’s medicine has not always enjoyed such favorable prospects.

In 2010, Roche and Biogen suspended trials of the humanized monoclonal antibody against rheumatoid arthritis after patents died from fatal opportunistic infections. Trials were also suspended for lupus nephritis patients. (reut.rs/2gJfDIp)

Against multiple sclerosis, however, Roche has said the infection deaths were not repeated, with the negative effects of Ocrevus mostly infusion-related and appearing at similar rates as those of placebo treatments.