Biogen stock plunges 28%

Biogen announced Thursday it would cancel a promising drug trial it hoped could treat Alzheimer’s disease. The company’s stock fell more than 28%.

Shares of Biogen are on track for their worst day since February 2005.

Biogen said in a statement that it had decided to end the Phase 3 trials of the drug, called aducanumab, after an independent audit revealed the drug was unlikely to work.

Aducanumab was widely believed to be the company’s next blockbuster drug because of its success in earlier trials. But treating Alzheimer’s is proving elusive. Biogen is the latest in a series of pharmaceutical companies to halt research on Alzheimer’s treatments in recent years. Eli Lilly, Pfizer, AstraZeneca and Merck have all canceled Alzheimer’s drug trials.

“This disappointing news confirms the complexity of treating Alzheimer’s disease and the need to further advance knowledge in neuroscience,” Biogen CEO Michel Vounatsos said. “We are incredibly grateful to all the Alzheimer’s disease patients, their families and the investigators who participated in the trials and contributed greatly to this research.”

The company said it will continue to work on developing treatments for Alzheimer’s, which kills more Americans than breast cancer and prostate cancer combined, according to the Alzheimer’s Association.

The safety of the drug, which Biogen developed with Japanese pharmaceutical company Eisai, did not play a role in the decision to end the trials according to a statement.