(Bloomberg) -- Biogen Inc. plunged after the company said it was making changes to a trial of an Alzheimer’s disease drug, after a long list of rival drugs failed.
In a presentation to investors Wednesday, Biogen said it would add about 500 more patients to its studies of aducanumab, which is in the final stages of testing and was expected to produce full results later this year. Aducanumab is one the last remaining late-stage Alzheimer’s drugs still in testing.
The problem seems to have been that the tests were creating too much statistical noise, and not giving researchers a clear indication of whether or not the drug was helping patients.
“We did see more variability on the primary endpoint than assumed when we did the original sample size estimations,” Biogen Chief Medical Officer Al Sandrock said during an investor event hosted by Leerink Partners.
The shares fell as much as 9.1 percent, the biggest intraday drop since June 2016. They were down 8.2 percent to $291.08 at 3:18 p.m. in New York.
The company said that the option to expand the trial was planned. It raises concerns that the results may not be what the Cambridge, Massachusetts-based company hoped, said Brian Skorney, an analyst at Robert W. Baird & Co.
‘Not a Good Sign’
“Generally, it’s not a good sign when the way you designed your study isn’t working out appropriately,” Skorney said in a telephone interview. “Aducanumab is considered a very risky pipeline candidate to begin with, just given the history of Alzheimer’s trials.”
Biogen spokesman Matt Fearer said the company hasn’t seen whether or not the drug was working, an experimental practice called blinding. It plans to finish adding patients to the trial by midyear, he said.
No company has successfully brought to market a drug to treat the neurodegenerative disease, which affects millions of Americans and causes memory failure, dementia and eventually the loss of ability to perform basic functions.
On Tuesday, Merck & Co. said it was halting a trial of its most advanced Alzheimer’s drug, verubecestat, that it was testing in patients with the earliest stages of the disease.
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