Novartis AG (NVS) Friday said a patient treated with its multiple-sclerosis pill Gilenya has been diagnosed with a rare and often fatal brain disease.
The Swiss drug maker said the patient had been previously treated with another MS drug, Tysabri, co-marketed by Biogen Idec Inc. (BIIB) and Elan Corp. PLC (ELN), which has been already associated with progressive multifocal leukoencephalopathy.
"The current assessment is that Tysabri is the drug most likely associated with this case of PML," Novartis said in a statement. "However, a contribution of Gilenya to the evolution of this case cannot be excluded."
The development comes at a critical time for Novartis's Gilenya, a potential blockbuster product whose safety profile has recently come into question after the death of one person in the U.S. last autumn within 24 hours of starting treatment.
The European Medicines Agency, the body responsible for licensing Gilenya in Europe a year ago, is expected to issue a decision on the safety of the medicine following an in-depth review next week.
Novartis said it doesn't know of any confirmed PML cases in patients treated with Gilenya, also known as fingolimod, who hadn't previously been treated with Tysabri.
At 0900 GMT, Novartis shares were trading 0.4% lower at CHF49.79.
-By Marta Falconi, Dow Jones Newswires; +41 43 443 8043; email@example.com