A fatal case of progressive multifocal leukoencephalopathy (PML) has been reported for the first time in a patient receiving dimethyl fumarate (Tecfidera), a medicine that was recently launched for relapsing-remitting multiple sclerosis (MS).
PML is a viral infection of the brain. The virus is carried by most healthy people but when the immune system is compromised it can cause brain damage and is fatal in 30–50% of cases. The patient who died had been receiving long-term treatment with dimethyl fumarate and had developed a severely low level of lymphocytes, a known side effect of the drug.
Tecfidera was launched in February 2014 by Biogen and was recommended by the National Institute for Health and Care Excellence six months later. In phase III trials, dimethyl fumarate halved the annual relapse rate of relapsing-remitting MS compared with placebo and was more effective than glatiramer.
The case of PML was highlighted by the Pharmacovigilance Risk Assessment Committee (PRAC), part of the European Medicines Agency, at its latest meeting on 3-6 November 2014. PRAC recommended that the case is investigated further.