A health ministry panel reviewing the new Alzheimer’s drug lecanemab greenlighted its approval in Japan on Monday, amid high expectations for what it can do against the neurodegenerative disease and concerns from others about its side effects, cost and availability.

The experts determined that lecanemab — the first drug seen to slow the progression of the disease — was effective enough to grant it regulatory approval, a health ministry official said Monday night after the closed panel meeting.

The panel’s endorsement will be followed by official approval by the health minister in coming days.

The rollout of the medication, developed by Japanese drugmaker Eisai and U.S. firm Biogen, could start in the fall, after its price is decided by the government. But it will cover only a fraction of the millions of people in Japan with Alzheimer’s, as it can only be used for those who are in the early stages of the progressive disease and have undergone necessary testing.

Lecanemab, marketed under the brand name Leqembi, is different from four Alzheimer’s drugs currently in use in Japan. The existing drugs boost or regulate the activities of chemical messengers involved in brain functions, such as those for learning and memory, but can only help to ease or manage symptoms.

Lecanemab — like its predecessor aducanumab, which has been granted conditional approval in the United States but not in Japan — contains antibodies designed to remove a protein called amyloid-beta from the brain and prevent the formation of plaques of that protein, which is thought to contribute to the death of brain cells.

In July, the U.S. Food and Drug Administration (FDA) granted the drug full approval, based on the results of an international clinical trial that involved 1,795 participants with early-stage Alzheimer’s. Lecanemab slowed cognitive decline by 27% after 18 months of treatment compared with those given a placebo, translating to a delay in the progression of the disease by five to 7½ months within 18 to 24 months of the start of treatment, according to the researchers.

However, the infusion drug is linked to side effects, including some serious ones, prompting some scientists to raise concerns over its safety.

The results of the trial, published in the New England Journal of Medicine in November, showed the drug resulted in an “infusion reaction” including fever, chills, headaches and vomiting in 26.4% of those given lecanemab, against 7.4% in those given a placebo. Brain bleeding was seen in 14% of patients in the lecanemab group, against 7.7% in the placebo group, and brain swelling was observed in 12.6% of those who took lecanemab, compared with the placebo group’s 1.7%.

In the U.S. the drug is priced at $26,500 per year per person, but it is covered by Medicare, a federal health insurance program for those age 65 or older. The out-of-pocket expenses for those eligible are reported to be around $5,000 per year.

Since Japan’s national health insurance reimburses patients receiving expensive medical treatments that have been approved by the government, the cost for individual patients will likely be within several tens of thousands of yen per month. But a heated debate is expected over how much of the high cost the government should shoulder.

Takeshi Iwatsubo, a neuropathologist at the University of Tokyo who specializes in Alzheimer’s and serves as an adviser to Eisai, has said that the number of patients who will receive lecanemab in Japan will initially be “tens of thousands” per year, although this could grow to hundreds of thousands down the road.

Competition by drugmakers to develop treatments designed to slow cognitive decline through the removal of amyloid proteins in the brain is intensifying.

Donanemab, an Alzheimer's drug developed by U.S. firm Eli Lilly, slowed the progression of the disease by 35% compared with a placebo in a late-stage trial covering 1,182 people with early-stage Alzheimer's, according to the firm. The participants' brains had deposits of two proteins — amyloid beta as well as intermediate levels of tau, another protein linked with disease progression and brain cell death.

Eli Lilly has filed for approval in the U.S. and expects a decision by the FDA by the end of the year. It has yet to file for approval of the drug in Japan.