Eli Lilly's Alzheimer's drug falls short for accelerated approval from the FDA

Eli Lilly's Alzheimer's drug donanemab is rejected for accelerated approval by the US FDA, but the clinical trial data still shows promise for coming up for standard approval later in the year. 

The FDA explained its rejection of the experimental drug from Eli Lilly was due to a lack of trial data from patients who had been treated with the drug for a minimum of one year. 

The drug, donanemab, is a humanised monoclonal antibody that actively removes amyloid plaques from the brains of those with early-stage Alzheimer’s disease. There has been some concern over using these antibodies in patients as they can cause microhaemorrhages in the brain, but this hasn’t been shown when donanemab has been tested. However, the FDA have noted that not enough trial data exists for them to fully rule out any concerns. 

Eli Lilly received a complete response letter from the FDA regarding donanemab, which is likely to stipulate the standards that need to be met for the drug to be approved. 

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 stated. 

Lilly points out that patients in the mid-stage trial who achieved clearance of the amyloid plaques in their brains then stopped the treatment. This typically took around six months in 40% of patients. 

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

The drug is still undergoing a Phase III trial to further confirm results, with this data hopefully supporting the current information, which altogether will be used in the next application for FDA approval later in the year. 

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

Chief Operating Officer Russ Paulsen from UsAgainstAlzheimer's stated that 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 put in an email.

The nuance of accelerated approval from the US FDA means that approval can only be granted if the measurement of an indicator correlates directly to an improvement in patient response and outcomes. Therefore longer-term clinical data is necessary to fully evaluate the patient outcomes.