New Alzheimer's Drugs Show Promise, But Long-Term Effects Remain Unclear

The recent FDA approval of new Alzheimer’s medications has given patients and families a renewed sense of hope. These treatments are the first to target the physical root causes of the disease rather than just managing the symptoms. However, while early clinical results look positive, serious side effects like brain swelling mean these treatments require careful consideration.

The New Era of Alzheimer's Treatment

For decades, doctors could only offer medications that temporarily masked the symptoms of memory loss. That changed recently with the introduction of a new class of drugs called monoclonal antibodies. These medications work by identifying and removing amyloid-beta, a sticky protein that clumps together to form plaques in the brains of Alzheimer’s patients.

Currently, there are two major drugs in this category approved by the FDA:

  • Leqembi (lecanemab): Developed by Eisai and Biogen, this drug received full FDA approval in July 2023. Patients receive it through an intravenous infusion every two weeks.
  • Kisunla (donanemab): Developed by Eli Lilly, this drug received FDA approval in July 2024. Patients receive this treatment via a once-a-month IV infusion.

Both of these medications are designed specifically for people in the early stages of Alzheimer’s disease or those experiencing mild cognitive impairment. They are not approved for patients in the advanced stages of the disease.

Evaluating the Efficacy: How Well Do They Work?

When medical professionals talk about these new drugs showing promise, they are referring to a measurable slowdown in cognitive decline. It is important to understand that these medications are not cures. They do not reverse memory loss, nor do they completely stop the disease from progressing.

Instead, they buy patients more time.

Clinical trials for Leqembi showed that the drug slowed cognitive decline by 27% over an 18-month period compared to a placebo. Kisunla showed even stronger results in its trials, slowing cognitive decline by roughly 35% over the same 18-month timeframe.

For a patient, this percentage translates to real-world time. A 27% to 35% slowdown might mean an extra five to seven months of preserving independent function. This could allow a patient to continue driving, managing their own finances, or recognizing their grandchildren for a longer period before the disease inevitably advances.

The Major Risk: Brain Swelling and Bleeding

The most significant concern surrounding these new medications is a medical condition known as ARIA. ARIA stands for Amyloid-Related Imaging Abnormalities. It is a side effect that doctors monitor very closely using MRI scans.

There are two primary types of ARIA:

  • ARIA-E: This involves edema, or swelling, in the brain.
  • ARIA-H: This involves microhemorrhages, or small bleeds, in the brain.

Why does this happen? Amyloid plaques do not just float freely in the brain. They often build up along the walls of the brain’s blood vessels. When the monoclonal antibodies attack and dissolve these plaques, the walls of the blood vessels can become temporarily weakened or damaged. This allows fluid or tiny amounts of blood to leak into the surrounding brain tissue.

The risk levels are notable. In clinical trials, roughly 21% of patients taking Leqembi experienced some form of ARIA. For Kisunla, the rate was higher, with about 36% of patients showing signs of ARIA on their brain scans.

While many patients who develop ARIA never experience any physical symptoms, others suffer from severe headaches, confusion, dizziness, nausea, and in rare cases, life-threatening seizures. Because of this, patients must undergo frequent MRI scans during their first year of treatment to catch any swelling before it becomes dangerous.

The Unknown Long-Term Effects

While the 18-month clinical trial data gives doctors a clear picture of short-term safety and efficacy, the long-term effects of these drugs remain entirely unclear.

Medical researchers still have several unanswered questions:

  • Duration of benefit: Does the 27% to 35% slowdown in cognitive decline hold steady after three, five, or ten years? Or does the disease eventually accelerate and catch up to where it would have been without the drug?
  • The role of Tau protein: Alzheimer’s involves two proteins (amyloid and tau). These new drugs only clear amyloid. Many scientists worry that once tau tangles begin spreading through the brain, removing amyloid will no longer help the patient.
  • Stopping treatment: Kisunla allows patients to stop taking the drug once brain scans show the amyloid plaques are gone. Doctors do not yet know how long it takes for the plaques to return or if the cognitive benefits persist after the infusions stop.

The Logistical and Financial Burden

Beyond the medical risks, these drugs place a heavy burden on families and the healthcare system. Leqembi costs about $26,500 per year, while Kisunla is priced at roughly $32,000 per year.

Medicare does cover these treatments, but the hidden costs add up quickly. Patients must pay out of pocket for the facility fees associated with bi-weekly or monthly infusions. They also have to cover the copays for the required PET scans to confirm the presence of amyloid plaques, as well as the multiple MRI scans needed to monitor for brain swelling. For many families in rural areas, traveling to specialized infusion centers and imaging facilities twice a month is simply impossible.

Frequently Asked Questions

Are Leqembi and Kisunla a cure for Alzheimer’s? No. These medications do not cure Alzheimer’s disease. They are designed to clear amyloid plaques from the brain, which slows down the progression of memory loss and cognitive decline by 27% to 35% over 18 months.

Can anyone with Alzheimer’s take these new drugs? No. The FDA has only approved these medications for people in the mild or early stages of Alzheimer’s disease. Patients must also undergo a PET scan or a spinal tap to prove they have amyloid plaques in their brain before they can start treatment.

What are the symptoms of brain swelling (ARIA)? Many patients with ARIA have no symptoms at all, and the swelling is only found during a routine MRI. When symptoms do occur, they usually include headaches, confusion, visual changes, dizziness, or nausea.

Does Medicare cover the cost of these new Alzheimer’s treatments? Yes, Medicare covers both Leqembi and Kisunla. However, doctors must participate in a registry to track patient progress and side effects. Patients will still be responsible for their standard Medicare Part B coinsurance, which applies to the drugs, the infusion center visits, and the required MRI scans.