Significant risks
Antiamyloid drugs are well-known to cause serious side effects. In the lecanemab trial, 13% of participants receiving Leqembi experienced brain swelling (vs. 2% of participants receiving placebo) and 17% of participants had brain bleeding (vs. 9% of participants on placebo). In the donanemab trial, brain bleeding occurred in 31.4% of participants on the drug (vs. 13.6% on placebo) and swelling occurred in 24% (vs. 2.1% receiving placebo). Thankfully, in both trials, most of these adverse events did not produce significant symptoms, but in rare cases these events caused severe or catastrophic neurologic injury, including death.
How can we best guide patients and their families to weigh the uncertain benefits against potentially serious risks? We can start by considering the patient characteristics most likely to portend increased risk for serious side effects: apo E4 mutations, blood thinner use, and the presence of microhemorrhages on brain imaging. But after that, we’re left with a lot of uncertainty in terms of which patients are most likely to see meaningful clinical improvements from the drug and unknown factors that may increase the risks of treatment.
A costly therapy
Medicare plans to cover 80% of lecanemab’s steep cost of $26,500 per year. Still, that will leave many patients with a hefty copay, potentially over $6,000 per year. But that only scratches the surface. Consider the frequent medical visits, repeated brain scans, laboratory tests, and infusion center appointments. It’s been estimated that all-in, the treatment will actually cost about $90,000 per year.
Yes, Medicare will reimburse a large portion of that cost, but it adds up to an estimated $2 billion per year for about 85,000 patients. This will probably spur increases to Medicare premiums, among other economic consequences for the health care system.
We’ll probably have to wait for an FDA approval decision before we know where donanemab will be priced.
Logistical challenges could be a rate-limiting step
Ask anyone who’s tried to see a neurologist recently, and they’ll tell you that the wait for a new patient appointment is months long. The shortage of neurologists in the United States is already a crisis, and there are even fewer cognitive neurologists. How long will patients be forced to wait for their diagnosis?
Many geriatricians will get comfortable prescribing these drugs, but will our already overburdened primary care providers have the bandwidth to do the same? It’s a tall order.
A new world of Alzheimer’s treatments also means that the infrastructure of our health care systems will need to be ramped up. Lecanemab infusions are administered every 2 weeks and donanemab every 4 weeks. Infusion centers will need to accommodate a lot more patients. And those patients will need frequent brain scans, so neuroimaging centers will need to increase their capacity to perform many more brain MRI and PET scans.
Antiamyloid drugs: An exciting first step
The bottom line is that these drugs aren’t the Alzheimer’s holy grail: An accessible treatment that could stop the disease in its tracks or reverse cognitive impairment. They are, however, a very promising breakthrough.
Yes, there are a ton of kinks to work out here, but this is an exciting start. Alzheimer’s research is entering a renaissance era that will hopefully bring more groundbreaking developments. Better biomarkers to facilitate faster, easier diagnosis. More drugs that go beyond amyloid proteins for their therapeutic targets. Treatments for later-stage disease. Drugs that prevent dementia altogether.
Ultimately, these new antiamyloid beta drugs are an exciting indication that we will eventually have a toolkit of Alzheimer’s drugs to choose from. For now, we’ve taken a solid step forward and there is ample reason to be hopeful for the future.
Dr. Croll is assistant professor of neurology at Temple University, Philadelphia. She reported no relevant conflicts of interest.
A version of this article first appeared on Medscape.com.