Biogen Plunges After Cowen Says Alzheimer’s Drug Data Pose Risk

Biogen Inc. dropped the most since April after Cowen & Co. said the biotechnology company’s stock price faces risk from data coming later this month on a drug to treat Alzheimer’s disease.

Investors are awaiting further insight into BIIB037, an experimental medication that has shown promise. In March, Biogen said that in an early-stage trial of 166 patients, BIIB037 reversed build-up of beta amyloid, a plaque linked to the brain disease, and also reduced cognitive decline. On July 22, Biogen will present data to show how one group of those patients, on a 6-milligram dosage, fared after 12 months on the drug.

Enthusiasm for BIIB037 has helped propel Biogen’s stock up about 14 percent this year. The shares could swing $50 in either direction depending on how much the drug held off cognitive decline compared with a placebo, Cowen analyst Eric Schmidt said in a note to clients.

“Even small changes to the drug’s probability of success are likely to have a substantial impact on Biogen’s share price,” Schmidt said. “While we are biased somewhat to the positive side, we lack conviction in this binary event.”

Biogen declined 2.8 percent to $388 at 11:09 a.m. in New York. It fell as much as 4.4 percent earlier, the biggest intraday decline since April 24. It was among the 10 biggest decliners on the Standard & Poor’s 500 Index.

Also Friday, Biogen’s head of research and development, Douglas Williams, said he would leave the company at the end of the month to become chief executive officer of an undisclosed biotech company. Chief Medical Officer Alfred Sandrock and Chief Scientific Officer Spyros Artavanis-Tsakonas will take over Williams’s responsibilities, the company said in a statement.