Biogen has reported a second non-fatal case of the serious brain injection progress multifocal leukoencephalopathy in a patient taking its multiple sclerosis drug Tecfidera.

According to media reports, the US biotech has informed regulators that PML developed in an MS patient who also had prolonged severe lymphopaenia, which is characterised by an abnormally low level of white blood cells and is listed as a risk factor for the condition in the drug’s label.

Risk of PML in certain patients was added to Tecfidera’s (dimethyl fumarate) label last year after an MS patient who developed the condition died. Before her death, the patient also had a very low number of lymphocytes, which can weaken the immune system and increase risk of PML. 

Tecfidera has been available in the US for MS since 2013. A spokesperson for Biogen told Medpage that the company doesn’t anticipate any further label changes at this time.