Jitters caused by the death of a patient taking Biogen Idec's blockbuster-in-waiting multiple sclerosis (MS) drug Tecfidera seem to have been unfounded.
Shares in the company took a dive yesterday on the news that a women in her 50s died after developing severe gastrointestinal symptoms (GI) which caused her to discontinue therapy with Tecfidera (dimethyl fumarate). GI symptoms are a recognised side effect with Biogen Idec's drug.
The stock recovered later in the day and in after-hours trading after it emerged that the cause of death - more than two weeks after stopping treatment - was in fact pneumonia and not GI-related.
Patients with MS are vulnerable to pneumonia, and the patient in question was also suffering from other problems including irritable bowel syndrome and had a history of recurrent chest infections.
Biogen Idec said in a statement that at this stage it is unlikely that the death is Tecfidera-related, but would continue to investigate the case.
The scale of the reaction to the news is a measure of how important Tecfidera is seen to Biogen Idec, with analysts predicting that the orally-active drug will eventually come to dominate the MS sector with peak sales of $3bn or more a year.
Tecfidera is competing in the marketplace with two other oral MS therapies, Novartis' Gilenya (fingolimod) and Sanofi's Aubagio (teriflunomide) but is predicted to outperform its rivals. Rapid take-up in the US since its launch in March 2013 has put the drug on track for sales of $1bn or more in its first year on the market, despite a delay to launch in Europe.
Part of the nervousness among investors also stems from Biogen Idec's previous experience with Tysabri (natalizumab), another MS drug which was launched to great fanfare in 2004 but taken off the market a year later after a rare but severe brain infection called progressive multifocal leukoencephalopathy (PML) caused by the drug claimed the lives of two patients.
Tysabri was reintroduced in 2006 after a way of screening patients for PML was found, and last year Biogen Idec booked $1.1bn in sales from the product.