What we know about the Alzheimer's drug Health Canada approved

Health Canada has conditionally approved the drug lecanemab to slow early-stage Alzheimer's disease, raising questions about its effectiveness and availability in Canada.

Lecanemab is a lab-made antibody given by intravenous infusion. It targets the buildup of amyloid plaque in the brain, a hallmark of Alzheimer's disease.

Lecanemab is not a cure and cannot reverse the disease or restore lost memories.

The Alzheimer Society of Canada calls it the first disease-modifying Alzheimer's treatment approved for use in the country. Current medications mitigate symptoms rather than change the course of the disease. 

How well the drug works and its potential impact on Canada's health-care systems are now considerations for people with the disease, their families, physicians and governments. 

Lecanemab, also known by the brand name Leqembi, is approved to treat mild cognitive impairment and early stages of Alzheimer's disease.

Patients must have a documented presence of amyloid plaque in the brain, Canada's Drug Agency said. 

Patients must also seek testing for gene variants associated with negative side-effects. The new treatment is only available for patients with a single or no copy of a gene variant called APOE4. Patients with two APOE4 copies are more likely to experience swelling or bleeding in the brain.

Access to the required genetic testing varies across provinces and territories.

When someone is diagnosed with dementia, a common fear is losing the ability to stay independent, said Dr. Samir Sinha, a geriatrician and clinician scientist at Sinai Health and the University Health Network in Toronto.

"Right now, it takes about 18 months before you might notice some sort of significant difference," Sinha said.

It's estimated 750,000 Canadians live with dementia and about 500,000 of them have a diagnosis, said Sinha. By the time a lot of people receive a formal diagnosis, they may no longer be good candidates for this medication, he said.

Sinha said he thinks more research is needed to answer whether lecanemab's benefits are worth the $26,000 US it costs in other countries. He questioned whether the results would be noticeable enough to allow patients to stay independent.

"It's a positive development that there's another medication that's been approved and it's available, but it's not necessarily a medication that would be the most practical one for me to prescribe or recommend for the majority of my patients."