The United States Food and Drug Administration (FDA) has granted full approval to the closely watched Alzheimer's drug, Leqembi, paving the way for Medicare and other insurance plans to cover the treatment for people with the progressive brain-robbing disease. Leqembi is the first medication ever to be convincingly proven to modestly slow the cognitive decline caused by Alzheimer's.

The FDA confirmed the drug's efficacy by reviewing data from a 1,800-patient study in which the drug slowed memory and thinking decline by about five months in those who received treatment, compared to those who received placebo.

While the drug's prescribing information will carry the most serious type of warning, indicating the risk of brain swelling and bleeding, these side effects are also seen with other plaque-targeting Alzheimer’s drugs.

The Alzheimer's patient and advocacy community have been lobbying the US federal government for months after Medicare officials announced last year they wouldn’t pay for routine use of drugs like Leqembi until they receive the FDA’s full approval.

This is due to the high cost of the drug, priced at about $26,500 for a year’s supply, and the potential for it to overwhelm the programme’s finances, which provide care for 60 million seniors. However, with the FDA's full approval now granted, Medicare will begin paying for the drug.

The programme is also setting extra requirements for administering the drug, including enrollment in a federal registry to track its real-world safety and effectiveness, as well as 20 percent of the cost being paid by the patient depending on their plans and coverage details.

Eisai, the Japanese drugmaker responsible for Leqembi, has estimated that around 100,000 Americans could be diagnosed and eligible to receive Leqembi by 2026.

The drug is co-marketed with Biogen, a company based in Cambridge, Massachusetts. Alexander Scott, Eisai's vice president, said “We want to ensure that appropriate patients only are the ones that get this product.” Leqembi has been studied in people with early or mild stage of Alzheimer's who were evaluated using a scale measuring memory, thinking and other basic skills.

After 18 months, those who were administered with Leqembi declined more slowly – a difference of less than half a point on the scale – than participants who received a dummy infusion.

The FDA's approval of Leqembi is a welcome breakthrough for Alzheimer’s patients and advocates, as the drug can now be administered to those in need with Medicare’s coverage.