A single course of treatment with an Alzheimer's drug developed by Japanese company Eisai and U.S. firm Biogen will cost around ¥2.98 million ($20,500) per year in Japan, and will be largely covered by public health insurance, a health ministry body said Wednesday.

The highly anticipated drug, lecanemab, will be launched in Japan on Dec. 20, the companies said. The drug won approval in September as the country's first medication that can slow the progression in symptoms of the debilitating neurodegenerative disease, by removing a protein believed to be the cause.

As the drug, branded Leqembi, will be covered by public health insurance, those undergoing treatment will pay between 10% and 30% of the cost out of their own pocket, depending on their age and income.