(Reuters) -The director of the U.S. Food and Drug Administration's Center for Drug Evaluation and Research, George Tidmarsh, resigned on Sunday amid serious concerns about his personal conduct, a Department of Health and Human Services spokesperson told Reuters on Monday.

He was placed on administrative leave on Friday after the Office of the General Counsel and the Office of the Inspector General were notified of the concerns, the spokesperson said.

Tidmarsh was appointed in July to oversee one of the FDA's largest and most important divisions, which regulates over-the-counter and prescription drugs.

"Secretary Kennedy expects the highest ethical standards from all individuals serving under his leadership and remains committed to full transparency," the HHS said.

In an interview with the New York Times on Sunday, Tidmarsh said he was placed on administrative leave after raising concerns about the legal basis of a new program for the rapid approval of some drugs.

He is also facing a lawsuit from Canadian drugmaker Aurinia Pharmaceuticals ( AUPH ) that accuses him of soliciting a bribe and damaging the company's stock with false statements as part of a revenge campaign against a former colleague, the Wall Street Journal reported on Sunday.

In September Tidmarsh questioned the safety and clinical benefit of Aurinia's lupus drug, Lupkynis, in a LinkedIn post that was later deleted. Aurinia said the drug is safe and effective, citing data from two major trials and the FDA's full approval in 2021.

The departure comes as U.S. health agencies undergo significant leadership changes under Health Secretary Robert F. Kennedy Jr.

Longtime vaccine official Peter Marks was ousted earlier this year, followed by gene-therapy head Nicole Verdun.