The FDA’s decision to grant accelerated approval for the anti-Alzheimer’s drug lecanemab, which will be sold as Leqembi, has significant potential for research into treatment of the disease. But people living with Alzheimer’s and their families will face difficult choices once the drug is made available later this month by Biogen and the Japanese firm Eisai.

A trial found the drug slowed the progression of early-stage Alzheimer’s Disease. There is no evidence that it helps people with moderate- or late-stage Alzheimer’s or that it benefits people living with any other form of dementia or even some forms of Alzheimer’s. It cannot reverse brain damage, memory loss, or other symptoms. It is not a cure and it is unclear how long any benefit will last.

However, the drug does suggest a promising path towards treating the disease. About 6 million Americans live with Alzheimer’s. Perhaps 1 million have early-stage disease, though many go undiagnosed.

What Is Leqembi? The drug is a monoclonal antibody that binds itself to a protein in the brain called Amyloid beta. By doing so, it helps the body destroy these proteins. People with Alzheimer’s have high levels of Amyloid beta in their brains and, in the trial, Leqembi significantly lowered those amounts. However, it remains unclear whether the protein causes Alzheimer’s, or how reducing it affects the disease’s progression.

Does It Work? In the 18-month trial, the drug slowed progression of the disease by 3-5 months.  However, benefits seemed to wane towards the end of the trial period. And because the trial ran for 18 months, it is not yet possible to know whether Leqembi has any long-term benefits. Because the study included only people with mild cognitive impairment caused by early-stage Alzheimer’s, the drugmakers have no evidence about the benefits or risks on those with later-stage disease. The trial also suggested that some people with a certain genetic risk factor for Alzheimer’s (those with the gene APOE4) may not benefit from the drug and may be more likely to suffer bleeding in their brains.

Are There Side Effects? There are. About 17 percent of those in the trial suffered brain bleeds and 13 percent brain swelling (ARIA). Most of these adverse events were minor, at least for those being carefully observed in the drug trial. But three trial subjects died. Some physicians worry about the effects of these bleeding episodes on people who are not under the regular care of a doctor or who may be taking blood thinners for conditions such as heart disease. There people should be very careful about taking Leqembi. The drug will carry a warning for these  patients.

How Will Patients Take It? It is given by infusion every two weeks and must be taken over a patient’s lifetime, or at least as long as it appears to slow the progression of Alzheimer’s.

What Will It Cost? Eisai says it will sell Leqembi for an average of $26,500-a-year. The independent non-profit Institute for Clinical and Economic Review calculates a cost-effective annual price for a typical patient should be between $8,500 to $20,600. For a sense of what $26,500 annually means to a family with limited resources, this sum could pay for 1,000 hours of a home health aide, more than 300 days of adult day, or six months in an assisted living facility.

Will Medicare Pay? Medicare will not pay, at least not now. Last year, after FDA approved a similar, but highly controversial, drug called Aduhelm, Medicare said it would not pay for it and similar drugs except for those in approved drug trials. For now, Medicare is treating Leqembi the same way. The Alzheimer’s Association and other drug-related advocacy groups, which heavily pressured FDA to approve both Adulhelm and Leqembi, now is pushing Medicare to pay for Leqembi. It would take Medicare several months to reverse its decision, should it choose to do so.

Will Private Insurers Pay? Like Medicare, most were reluctant to pay for Aduhelm, which despite FDA approval showed little evidence of clinical benefit to Alzheimer’s patients. Private insurers often take their cues from Medicare, but it is unclear now whether they’ll choose to pay for Leqembi, which shows more clinical promise than Aduhelm but whose benefits remain uncertain.

If I Have Alzheimer’s Should I Take It? That is the tough question. For researchers, Leqembi is highly promising. And it shows some clinical benefit for some people living with Alzheimer’s. But those benefits remain minimal. And the drug causes potentially serious adverse events in a significant number of patients.

Keep in mind too that the FDA is likely to approve other, related drugs in the coming months and years. Taking Leqembi likely would disqualify a patient from participating in trials of newer, potentially more effective drugs.

And there is the cost. For now, people with limited financial resources may have to make a tough choice. Buy a drug with promising but uncertain benefits or pay for day-to-day support that can certainly improve the quality of life of those living with the disease and their families.

It is not an easy choice. But for with Alzheimer’s Disease, there are few easy choices.