Donanemab Receives FDA Breakthrough Therapy Designation

Pharma company Eli Lilly announced that their antibody drug for Alzheimer's disease, donanemab, has been granted a Breakthrough Therapy designation from the US Food and Drug Administration (FDA).

What is the Breakthrough Therapy designation?

Breakthrough Therapy is a designation that makes a drug eligible for a faster approval process from the FDA. To receive the designation, a drug must show substantial improvement over those currently on the market.^1,2

This Breakthrough Therapy designation was based on results from a Phase 2 trial called TRAILBLAZER-ALZ. The trial included 272 people with early-stage Alzheimer's who took donanemab for over 76 weeks. Results were published in the New England Journal of Medicine.³

How does donanemab work?

In Alzheimer's, beta-amyloid proteins form plaques in the brain that can damage memory and thinking. Donanemab calls on the body's immune cells to help fight the deposits.⁴

In the TRAILBLAZER-ALZ trial, plaque deposits shrunk or disappeared. Scores for cognition and the ability to perform daily activities also increased. Other measures had mixed results.

Similar to Aduhelm®

Aduhelm® (aducanumab) is a drug made by Biogen to treat Alzheimer’s. It received accelerated approval from the FDA in June 2021. It also seeks out plaque deposits caused by beta-amyloid proteins.

In the prescribing information for Aduhelm, there are warnings of side effects including temporary swelling of the brain (known as ARIA), headache, fall, diarrhea, swelling, hives, and confusion/delirium/altered mental status/disorientation.⁵

Aduhelm was the first drug of its kind to be approved for the treatment of Alzheimer's disease. According to the FDA, it was the first drug to target the underlying cause of the disease rather than treating symptoms.

How does donanemab differ from Aduhelm?

On a basic level, these drugs work very much the same way. In clinical trials, people on both drugs had reductions in plaque deposits in the brain.^1,5

Because donanemab has not completed the full approval process yet, it is not available as a prescription, and the side effects are not published. Aduhelm is available for doctors to prescribe to Alzheimer's patients now.

In early clinical trials, it appears that there may be a smaller chance of ARIA with donanemab than with Aduhelm.⁴

How is donanemab administered?

Like Aduhelm, donanemab is given intravenously. For the TRAILBLAZER-ALZ trial, it was given in a 700-mg dose for the first 3 doses. Then it was given in 1,400-mg doses. Doses were administered every 4 weeks for 72 weeks.³

Progress was measured by changes in score on the following scales:³

• Integrated Alzheimer’s Disease Rating Scale (iADRS)
• Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB)
• Alzheimer’s Disease Assessment Scale’s 13-item cognitive subscale (ADAS-Cog13)
• Alzheimer’s Disease Cooperative Study-Instrumental Activities of Daily Living Inventory (ADCS-iADL)
• Mini-Mental State Examination (MMSE)

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