USFDA rejects accelerated approval for Eli Lilly Alzheimer's drug Donanemab

Lilly said the FDA had sent it a complete response letter for donanemab, an antibody designed to remove amyloid protein plaques from the brains of people with early Alzheimer's. Such letters typically outline concerns and conditions that must be addressed to gain U.S. approval.

The FDA had issued the letter "due to the limited number of patients with at least 12 months of drug exposure data provided in the submission," Eli Lilly said. In the mid-stage trial, patients stopped treatment once their amyloid was cleared - which Lilly said had happened after six months for 40% of patients.

"I don't think it says anything negative about the drug. It was just a manifestation of the study design," said Dr. Ronald Petersen, an Alzheimer's expert at the Mayo Clinic in Rochester, Minnesota.

The company said it remained on track to report in the second quarter of this year results from a confirmatory Phase 3 trial of donanemab. That study, Lilly said, would form the basis of donanemab's application for traditional FDA approval shortly thereafter.

"I don't see this is an impediment to the process or timeline in any way," said Dr. Eric Reiman, executive director of Banner Alzheimer's Institute. "When the Phase 3 trial reads out, I understand it will have that safety data in at least 100 people."

UsAgainstAlzheimer's chief operating officer Russ Paulsen said the advocacy group was "disappointed this treatment won’t be made available to patients sooner," but was encouraged by the reason.

"Donanemab worked too well .... The FDA requires a minimum of 100 patients to be on the drug for at least 12 months but, due to donanemab's quick action in some patients, many were able to stop treatment in as little as six months," he said in an email.

The FDA can grant "accelerated" approval to drugs based on their impact on a measurement, in this case amyloid brain plaques, likely to correlate with patient response. Full approval requires clinical evidence a drug will help patient outcomes.

Shares of Lilly were down 1.4% at $346.02 in after hours trading.

Donanemab is in the same class as aducanumab and lecanemab, the latter being a treatment for early Alzheimer's that was given accelerated approval by the FDA earlier this month. It is being marketed under the brand name Leqembi by partners Eisai Co Ltd and Biogen Inc, which have said they are in the process of seeking full FDA approval.

Shares of Biogen were up 2.8% at $288 after hours.

Sales of amyloid-lowering Alzheimer's drugs, which need to be given by infusion, are expected to be minimal until they receive standard FDA approval. That is because the U.S. government's Medicare health plan for people over age 65 currently reimburses amyloid-targeting drugs with accelerated approval only if patients are enrolled in a validated clinical study.