While there are many types of dementia, Alzheimer’s disease is by far the most common. According to the Alzheimer’s Association, over 7 million Americans have Alzheimer’s disease, as of 2025. In Alzheimer’s disease, plaques form in the brain and tend to affect people at any age. Symptoms usually get worse over time.
The U.S. Food and Drug Administration has approved new medications to treat mild or early dementia due to Alzheimer’s disease. Leqembi® (lecanemab), and Kisunla™ (donanemab), are both monoclonal antibody treatments that are designed to reduce amyloid beta plaques in the brain. These drugs are administered by intravenous infusion, though injectable forms are being developed.
At present, Mount Sinai is offering the monoclonal antibodies Lecanemab and Donanemab to eligible patients.
How It Works
Monoclonal antibodies work by clearing the plaques from your brain. These plaques are usually made up of a protein called amyloid. We’re not sure whether the plaques cause dementia, but we know they play a significant role.
Recent studies showed that monoclonal antibodies can slow the decline of symptoms such as forgetfulness and problems with day-to-day function. Patients who received the monoclonal antibodies experienced an average of 6-7 month slower decline in their symptoms than those who didn’t. The studies followed patients for 18 months, and we do not know yet what happens after that point.
Side Effects
Monoclonal antibodies can cause side effects in some patients. The most serious is swelling or bleeding in the brain, which affects up to 20 percent of patients. Most patients with these symptoms don’t feel anything and we can find it only with a magnetic resonance imaging (MRI) scan. At some point in treatment, some patients may experience:
- Confusion
- Difficulty walking
- Dizziness
- Headaches
- Nausea
- Vision changes
- Seizures
- Inability to speak
- Loss of movement in an arm or leg
Up to 25 percent of patients receiving monoclonal antibodies develop infusion-related reactions. Most of these reactions presented as mild flu-like symptoms, such as chills, body aches, joint pain and/or feeling shaky, nausea, vomiting, or dizziness or lightheadedness. In a smaller number of patients, infusion-related reactions are more severe, such as changes in heart rate, blood pressure or difficulty breathing. Rarely, patients with an infusion-related reaction had to be hospitalized because of severe allergic reactions.
Who It Can Help
To receive monoclonal antibody treatment, you must be:
- 50 to 90 years of age
- Diagnosed with mild cognitive impairment or mild dementia due to Alzheimer’s
- Have minimal or no functional impairment
- Have a body mass index between 17 and 35
- Able to receive magnetic resonance imaging scans
There are also other requirements that your clinician can discuss with you. To be sure you meet these requirements, we will do the following tests:
- An Alzheimer’s disease biomarker test by amyloid positron emission testing (PET) or by spinal tap study. The biomarker must be positive for Alzheimer’s disease.
- A brain magnetic resonance imaging (MRI) scan no more than 12 months before starting treatment
- Possible genetic testing for genes that may increase the risk of side effects from monoclonal antibodies (such as the APOE4 gene)
Per Mount Sinai’s best practice guidelines, you cannot receive monoclonal antibody treatment if you:
- Are taking medications to thin your blood (except for standard doses of aspirin and other antiplatelets)
- Have a bleeding disorder
- Have had a stroke or transient ischemic attack in the previous year
- Have a history of seizures
Treatment Process
Leqembi® (lecanemab):
You will receive an intravenous infusion every 2 weeks, in a certified facility, for at least 18 months. We will also perform MRI scans regularly to monitor for complications. The infusion itself takes one hour, plus the time for check-in and post-infusion monitoring. After your first infusion, we will monitor you for at least three hours after the infusion. In addition, we will perform MRI scans before your 5th, 7th, and 14th infusion, to check for swelling or bleeding in the brain. After 18 months of receiving the intravenous infusion every 2 weeks, the patient may switch to a maintenance dose which is given once every 4 weeks.
Kisunla™ (donanemab):
You will receive an intravenous infusion every 4 weeks, in a certified facility, for at least 12 months. We will also perform MRI scans regularly to monitor for complications. The infusion itself takes 30 minutes, plus the time for check-in and post-infusion monitoring. After your first infusion, we will monitor you for at least three hours after the infusion. In addition, we will perform MRI scans before your 2nd, 3rd, 4th, and 7th infusion to check for swelling or bleeding in the brain. After a year to 18 months of the treatment, the treatment may be stopped after demonstrating resolution of findings on the amyloid PET scan.
Medicare Coverage
If you meet certain criteria, Medicare will pay for the treatment. Depending on your insurance plan, you may have a copay.