03 Jul 2024

Donanemab has become the second anti-amyloid immunotherapy to win traditional approval from the U.S. Food and Drug Administration. The antibody, which will be marketed as Kisunla, got the official go-ahead July 2. The decision had been widely expected after the agency’s advisory committee voted unanimously in favor of the drug June 10 (Jun 2024 news). The announcement was covered in the media and welcomed by advocacy groups (The New York Times).

The FDA label for donanemab is similar to that of lecanemab, which was approved almost a year ago to the day (Jul 2023 news). It includes a boxed warning of the risk of ARIA, particularly for people who have two copies of the APOE4 allele, and it recommends APOE genotyping before prescribing the drug. To monitor for ARIA, the FDA suggests MRI at baseline and before the second, third, fourth, and seventh infusions. This is more frequent than before the fifth, seventh, and 14th infusions as recommended for lecanemab. Donanemab has about twice the risk of ARIA, with most serious reactions occurring early (Jun 2024 news). 

The label also discusses the increased risk of ARIA for people with cerebral amyloid angiopathy or other signs of cerebrovascular disease. It urges caution prescribing the drug to patients on antithrombotic medications. As with lecanemab, however, the FDA leaves these decisions up to clinical judgment. The only listed contraindication is for people with a known hypersensitivity reaction to donanemab.

In clinical trials, donanemab dosing was halted once amyloid plaques were gone. The label advises physicians to consider stopping treatment after plaques reach “minimal levels” on amyloid PET scans, but does not provide further guidelines. The label does not discuss tau PET imaging, which was used in the Phase 2 and 3 trials to select the patients most likely to benefit.

Donanemab will cost about $32,000 per year, compared with $26,500 a year for lecanemab. In the Phase 3 trial, about two-thirds of patients on donanemab were amyloid-negative by one year. This could allay the lifetime cost of treatment. Lecanemab is expected to be given indefinitely, with its yearly cost cut in half once plaques are gone and patients are shifted to maintenance dosing (May 2024 news). Both antibodies will be covered by Medicare, as long as physicians enter data into an approved patient registry (Jun 2023 news). So far, this process has been trouble-free for lecanemab in the clinic (Jan 2024 news).—Madolyn Bowman Rogers