Patient taking Novartis' Gilenya develops PML

Novartis reported Tuesday that a patient who had been taking its multiple sclerosis drug Gilenya (fingolimod) for seven months developed progressive multifocal leukoencephalopathy (PML). The company stated that it was working with the reporting physician to understand all potential contributing factors, noting that "the course of the underlying neurological disease was rapid with some atypical findings for MS on the MRI scans of the brain and spinal cord, as well as some unusual clinical features."

The drugmaker pointed out that all previously cases of PML reported to date among the roughly 71 000 patients treated with Gilenya had been attributed to prior treatment with Biogen Idec's Tysabri (natalizumab), which has a known risk for the potentially fatal viral infection.

Deutsche Bank analyst Richard Parkes remarked that the PML case potentially associated with Gilenya "may cause some further jitters about the growth potential of this drug, which is a key driver for the company." However, Tim Race, also of Deutsche Bank, noted that the incidence of reported PML cases for Gilenya has so far been quite low. "By the time there was a similar level of patient experience with Tysabri there had been 298 cases reported. Thus, even if the risk proves to be real, it is likely to be of a very different order of magnitude," he added.

Gilenya, which is licensed from Mitsubishi Tanabe Pharma and garnered second-quarter sales of $468 million, is the first once-daily oral therapy that was approved by the FDA and EU to treat relapsing forms of MS. However, Novartis' drug faces increased competition since Biogen Idec's multiple sclerosis drug Tecfidera (dimethyl fumarate) was cleared in the US in March. Last month, Biogen Idec said it was investigating the death of a patient who took Tecfidera, but the company suggested its therapy was not likely the cause.

For related analysis, see ViewPoints: Will new doubts over JC virus test undermine growth outlook for Biogen Idec's Tysabri? and ViewPoints: Data remain early, but Tecfidera "crushing" launches of other oral MS treatments.

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