Biogen Idec Inc. said Wednesday that a patient who had taken its multiple sclerosis pill Tecfidera for more than four years died after getting a rare brain infection, sending shares of the Cambridge biotechnology company down sharply.
While the cause of death was pneumonia and there is no evidence conclusively linking it to the best-selling MS treatment, Biogen Idec spokeswoman Kate Niazi-Sai said in an interview that the company “can’t rule out Tecfidera as playing a role” in the brain infection known as progressive multifocal leukoencephalopathy, or PML.
Executives at Biogen Idec, the leading seller of MS drugs, reported the death during a conference call with analysts Wednesday after releasing stronger than anticipated third-quarter financial results. The company’s shares plunged $17.70 to $309.07, a loss of 5.4 percent on the Nasdaq stock exchange.
If it is confirmed that Tecfidera caused the brain infection, it would be the first time a PML case was tied to Biogen Idec’s multiple sclerosis pill. Tecfidera was approved by the Food and Drug Administration for US sale in March 2013. It has been used by more than 100,000 patients since the company began testing it in clinical trials more than 10 years ago.
As of last month, 495 cases of PML worldwide in patients taking an injected Biogen Idec drug, Tysabri, have been reported. Of those, 111 patients have died, while the rest are living with varying degrees of disability.
Tysabri was approved by the FDA in 2004, then pulled from the market in 2005 because of safety concerns. It was reintroduced in 2006 with a stringent monitoring program, and the company has since developed a test to determine which patients might be vulnerable to the brain infection.
Niazi-Sai said the company won’t disclose the identity, age, or gender of the Tecfidera patient who died. She said the patient had been taking the drug for four and a half years, and for three and a half years had experienced severe prolonged lymphopenia, a lowering of the white blood cell count. That condition is a known risk factor for PML.
Biogen Idec has modified its label for Tysabri to note several risk factors for PML. But there are no current plans to change the Tecfidera label.
“At this point, we don’t feel the risk-benefit ratio has changed in Tecfidera,” said Niazi-Sai. “We did notify the regulatory authorities, and if they want us to revisit our label we will work with them.”
Up to 5 percent of Tecfidera patients have to worry about low white blood cell counts, Eric Schmidt, biotechnology analyst for financial firm Cowen & Co., wrote in a note to investors Wednesday. He cited data from industry consultants. A change in the drug’s label could persuade many of those patients -- especially those with a virus known as a PML risk factor -- to stop taking the pill, he said.
Nonetheless,” wrote Schmidt, “the first report of PML in over 100,000 patients treated [with Tecfidera] should not be concerning for the other 95 percent of the MS population.”
Tecfidera sales have been brisk of late, making it Biogen Idec’s fastest-growing product. Revenue from the drug more than doubled to $787.1 million in the three months ending Sept. 3o compared with the same quarter last year.Robert Weisman can be reached at email@example.com. Follow him on Twitter @GlobeRobW.