The FDA said it instructed Novartis to place a new warning on labeling for its multiple sclerosis treatment Gilenya (fingolimod) and the agency issued a warning that abruptly ending treatment can severely exacerbate the disease.

The drug was approved in the U.S. in 2010 for relapsing MS, or periods when symptoms of the condition become worse.

Since then, the agency has identified 35 cases of severely increased disability accompanied by multiple new lesions occurring two to 24 weeks after stopping treatment with Gilenya. In most cases, the adverse events occurred within the first 12 weeks after stopping the drug.