Brain swelling. Brain hemorrhage. Strokes. Seizures. Falls. Trouble thinking.
Those are the known risks of donanemab, the new Alzheimer’s drug the FDA approved on July 15, 2024. Eli Lilly developed it, sells it as Kisunla. The target population is specific: people with mild cognitive impairment or mild dementia from Alzheimer’s. Not advanced cases. Not prevention. Just the early stages.
The numbers are stark. Clinical trial data shows brain hemorrhage and swelling hit 36.8% of patients taking the drug. That is more than one in three. In the placebo group, 14.9% had the same problems. So the drug roughly doubles the risk of these serious complications.
These are not minor side effects. Amyloid-related imaging abnormalities — that is the clinical term — can escalate fast. Strokes. Seizures. Falls. Cognitive trouble. The very thing the drug is supposed to slow down.
Headache and allergic reactions also turned up as common side effects. Less dramatic, but still a burden for patients already managing a devastating disease.
The FDA advisory panel was split. Most members voted against approval. Public interest groups testified against the drug during hearings. They cited safety concerns. They questioned effectiveness.
Yet the FDA approved it anyway.
Why? Because Alzheimer’s patients and their families have few options. The disease affects millions. The pipeline of treatments has been thin for decades. Donanemab is a monoclonal antibody — a type of biologic drug that targets amyloid plaques in the brain. It is not a cure. It does not reverse damage. But for people with mild symptoms, it may slow progression.
The clinical trials tested it exactly in that population. Mild cognitive impairment. Mild dementia. That is the only group where any benefit was demonstrated. And even there, the benefit comes with the 36.8% risk of brain bleeding or swelling.
Eli Lilly faces a challenge now. How to market a drug that requires careful patient selection and close monitoring. How to communicate risk to families desperate for hope. How to ensure doctors do not prescribe it off-label to patients with more advanced disease, where no trial data exists and risks may be higher.
The approval itself was not a surprise. The FDA has been under pressure to deliver treatments for Alzheimer’s. Earlier drugs in the same class, like Biogen’s Aduhelm, faced their own controversies. Aduhelm was approved despite an advisory panel voting against it. That pattern repeated here.
Critics say the agency is lowering its standards. Supporters say patients cannot wait for perfect drugs. Both sides have evidence. The brain hemorrhage data is real. The lack of alternatives is real.
For a patient with mild Alzheimer’s, the decision is brutal. Take a drug that might slow the disease but carries a one-in-three chance of a serious brain event. Or do nothing and watch the disease progress.
Doctors will have to weigh each case individually. Age matters. Overall health matters. Other medications matter. The risk of falls from a brain bleed might outweigh any cognitive benefit for an older patient who already struggles with balance.
The FDA’s approval opens the door. But the door leads into a room with hard choices.
