The company expects to reach 90% of its target for integrated delivery networks (IDNs) used to administer the drug in the U.S. in the fiscal year ending this month, Chief Executive Haruo Naito said.

"In the United States, in comparison to what we have expected, it may be taking slightly more time," Naito said at a briefing in Tokyo. "We are confident that we are on a good trajectory."

Leqembi is an antibody designed to remove sticky deposits of a protein called amyloid beta from the brains of Alzheimer's patients. It is the first treatment shown to slow progression of Alzheimer's when administered in the earlier stages of the disease.

The drug was approved in the U.S. and Japan last year, and it is under review in Europe. Eisai is aiming to introduce Leqembi in China this year following approval by regulators there in January.

The drug's debut in Japan has progressed smoothly, Naito said, and the company is ramping up production ahead of a planned July launch in China.

The Chinese system for diagnosis and treatment of Alzheimer's is unique and could serve as a model for expansion in India along with other markets in Asia and Africa, Naito said.

(Reporting by Rocky Swift; Editing by Christopher Cushing)