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Biogen said it plans to resume previous studies of its once-abandoned drug for Alzheimer’s disease, rolling out detailed trial data to a standing-room-only gathering of scientists in California.

The company’s in-depth presentation at the Clinical Trials on Alzheimer’s Disease conference in San Diego on Thursday marked a climax in a monthslong saga that has seen patients’ hopes dashed and revived, and Biogen’s stock price plummet and then rebound.

It was the first in-depth look Biogen has provided at the experimental treatment, known as aducanumab, since reviving it in October. In March, Biogen declared two studies of the medicine failures and abandoned the drug. But executives said on Thursday that additional data showed the infusion, if given long enough and at high doses, could offer some benefit.

“This could represent the first treatment that targets a core pathology and open an era of precision medicine for Alzheimer’s disease,” said Stephen Salloway, a Brown University professor who was part of a panel that discussed the results at the conference. “This is a milestone achievement for our field.”

Shares of the Cambridge, Mass.-based company were volatile as investors processed the vast new trove of information. After initially dipping nearly 4%, the stock was up 3.4% at $299.32 at 1:25 p.m. on Thursday in New York.

Aducanumab’s path is a reflection of the rollercoaster ride that researchers and drugmakers have been on for decades in trying to develop a way to combat Alzheimer’s disease.

“This is a pivotal time in the field, certainly with regard to the development of Alzheimer’s therapeutics,” said Ronald Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center in Rochester, who led the discussion of the study on behalf of the scientific organizers.

“Certainly there have been a lot of ups and downs in recent months and years, unfortunately more downs than ups,” said Petersen. “In many senses the aducanumab data that we are discussing today sort of characterizes — is almost a caricature — of the course we have had in the field.”

The move comes as researchers debate whether another study will be needed to confirm the drug’s benefits before it becomes widely available, a decision that will ultimately be the domain of the U.S. Food and Drug Administration and other regulators.

Biogen shocked researchers in March when it opted to shelve aducanumab, saying that trial results had suggested the drug was unlikely to work. The move caused investors to flee and disappointed scientists and patients.

Then, in October, the company reversed itself, saying new data had come to light suggesting that aducanumab could be effective. The presentation on Thursday was the first detailed look Biogen has provided at the data behind its dramatic decision to try to salvage the therapy.

As details of the trial unfurled, the most important audience was regulators who eventually will have to decide whether to allow aducanumab on the market.

“People are hoping of course, always hoping, that we will find something, but we aren’t going to approve drugs that aren’t effective,” said Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, speaking generally in an interview on Wednesday, ahead of the data release. “People won’t send us applications if their trials fail; they will just terminate their programs.”

Biogen said it plans to file for FDA approval in early 2020. Woodcock, in an interview about the agency’s recent blistering pace for drug approvals, declined to comment specifically on Biogen’s program.