WASHINGTON (AP) — The director of the FDA’s drug division unexpectedly stepped down on Sunday, following the initiation of a federal review into “serious concerns about his personal conduct,” as reported by a government representative.

Dr. George Tidmarsh, who assumed the FDA role in July, was placed on administrative leave on Friday. This action occurred after officials from the Department of Health and Human Services’ Office of General Counsel were informed about the issues, according to HHS press secretary Emily Hilliard via email. Tidmarsh subsequently submitted his resignation on Sunday morning.

“Secretary Kennedy demands the utmost ethical behavior from all personnel under his leadership and is dedicated to ensuring complete transparency,” Hilliard stated.

The resignation coincided with a lawsuit filed by a pharmaceutical company linked to a former business partner of Tidmarsh. This suit accuses him of making “false and defamatory statements” during his tenure at the FDA.

Aurinia Pharmaceuticals, the company behind the legal action, claims that Tidmarsh exploited his FDA position to carry out a “longstanding personal vendetta” against Kevin Tang, the chair of the company’s board of directors.

Tang previously served as a board member of several drugmakers where Tidmarsh was an executive, including La Jolla Pharmaceutical, and was involved in his ouster from those leadership positions, according to the lawsuit.

Messages placed to Tidmarsh and his lawyer were not immediately returned late Sunday.

Tidmarsh founded and led a series of pharmaceutical companies over several decades working in California’s pharmaceutical and biotech industries. Before joining the FDA, he also served as an adjunct professor at Stanford University. He was recruited to join the agency over the summer after meeting with FDA Commissioner Marty Makary.

Tidmarsh’s ouster is the latest in a string of haphazard leadership changes at the agency, which has been rocked for months by firings, departures and controversial decisions on vaccines, fluoride and other products.

Dr. Vinay Prasad, who oversees FDA’s vaccine and biologics center, resigned in July after coming under fire from conservative activists close to President Donald Trump, only to rejoin the agency two weeks later at the behest of Health Secretary Robert F. Kennedy Jr.

The FDA’s drug center, which Tidmarsh oversaw, has lost more than 1,000 staffers over the past year to layoffs or resignations, according to agency figures. The center is the largest division of the FDA and is responsible for the review, safety and quality control of prescription and over-the-counter medicines.

In September, Tidmarsh drew public attention for a highly unusual post on LinkedIn stating that one of Aurinia Pharmaceutical’s products, a kidney drug, had “not been shown to provide a direct clinical benefit for patients.” It’s very unusual for an FDA regulator to single out individual companies and products in public comments online.

According to the company’s lawsuit, Aurinia’s stock dropped 20% shortly after the post, wiping out more than $350 million in shareholder value.

Tidmarsh later deleted the LinkedIn post and said he had posted it in his personal capacity, not as an FDA official.

Aurinia’s lawsuit also alleges, among other things, that Tidmarsh used his post at FDA to target a type of thyroid drug made by another company, American Laboratories, where Tang also serves as board chair.

The lawsuit, filed in U.S. District Court of Maryland, seeks compensatory and punitive damages and “to set the record straight,” according to the company.

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