Drug giant Eisai has said that its global Alzheimer drug program officer Ivan Cheung will retire at the end of the month and be replaced by the son of the firm’s CEO, after a tenure that saw him lead the push for U.S. approval of breakthrough medicine Leqembi.

Keisuke Naito, 34, a senior vice president and chief strategy and planning officer, will become the acting global Alzheimer’s officer, the company said in a statement Tuesday. Naito is a member of Eisai’s founding family and a son of CEO Haruo Naito.

Chief Financial Officer Tatsuyuki Yasuno will become acting president of its U.S. unit, Eisai said, another role that had been held by the outgoing Cheung.

Keisuke Naito has been in charge of strategy planning and creating a dementia platform with other industries to collect data and create solutions to detect the disease early. His family owns less than 2% of Eisai, according to data compiled by Bloomberg.

The 46-year-old Cheung is departing in order to seek new career challenges after 17 years with the company, an Eisai spokesperson said by phone Tuesday.

His resignation comes less than a week after Eisai and partner Biogen were granted full approval for Alzheimer drug Leqembi in the U.S. Leqembi is the first medicine shown to slow progression of the disease, which afflicts some 6 million Americans. Eisai is also seeking approvals in other markets.

Leqembi was granted expedited authorization in the U.S. in January, with the approval expected to spur greater insurance coverage for the drug, which costs $26,500 for a year's supply.