A prominent doctor is suing Mayo Clinic, accusing it of trying to stifle his public criticism of the federal COVID-19 response because the Rochester health system was worried about losing vital government funding.

In response, Mayo accused the doctor of making "unfounded allegations" and demanding a seven-figure payment from the health system at the height of the pandemic in 2020.

Dr. Michael Joyner's lawsuit is the latest step in a feud that has been simmering for nearly a year after Mayo suspended him without pay for one week, purportedly over his public comments. Colleagues from academic medical centers across the U.S. protested the disciplinary action this summer.

The suit was filed Tuesday in Olmsted County and asserted that Mayo "ignored its promise of free expression and academic freedom for faculty" when it sought to confine the doctor in public interviews to "prescribed messaging."

"Free speech and academic freedom do not become less important because of public disagreement or debate," Joyner argued in his complaint. "To the contrary, it is precisely during times of intense disagreement that unbiased research and expert opinions of faculty are most in service to the public."

The dispute pits the internationally renowned Mayo against one of its most visible doctors, who has given numerous interviews with media outlets across the world and has coauthored as many as 500 medical studies.

Mayo broke with its tradition of offering little or no comment in personnel disputes or lawsuits. Its four-paragraph statement accused the doctor of "invoking academic freedom as a shield to escape accountability for actions that violate Mayo policies and values."

"Mayo intends to show that in 2020, in the heart of the COVID-19 pandemic, Dr. Joyner gave Mayo an ultimatum, demanding that Mayo agree to give him a seven-figure payment within 48 hours," the statement said. "At the same time, he was found to have consistently engaged in rude and disrespectful communications toward coworkers and outside partners. Dr. Joyner received the highest level of disciplinary action short of termination."

A physician committee upheld the action after Joyner appealed it, the statement added, and an outside attorney concluded that it wasn't retaliation for Joyner's comments.

Joyner's attorney, Kellie Miller, called the statement "a vitriolic, defamatory, and baseless press release from Mayo's PR department."

The lawsuit seeks an unspecified amount of money and a court order requiring Mayo to comply with its policies favoring academic freedom and opposing retaliation.

Joyner pivoted his human performance lab at the outset of the pandemic to study whether the plasma from blood donors who previously had COVID-19 could treat others who contracted the infectious disease. His early research prompted a federal order to authorize plasma's use on an emergency basis, but the approach was largely supplanted by 2022 with alternatives such as new antiviral pills.

Joyner in a January 2023 CNN story accused the National Institutes of Health of "bureaucratic rope-a-dope" because of its halfhearted approval of plasma use in COVID cases. The NIH's "wet blanket" guidance for plasma undercut its use and potential during the pandemic, he said.

The comments had come on the heels of a May 2022 New York Times article in which Joyner had leapt into the politically explosive topic of transgender sports participation. Joyner opined that girls had competitive advantages in sports such as swimming initially because of their early development, but that boys outpaced them after puberty because of testosterone growth.

According to the lawsuit, Mayo in a disciplinary letter said that Joyner's comments "reflect poorly on Mayo Clinic's brand and reputation" and that in the future he must "discuss approved topics only."

Mayo, like most major U.S. academic medical centers, is reliant on competitive sources of federal funding to support research, clinical trials and training. It received $271 million in NIH research awards in 2023, ranking it second in Minnesota and 35th among U.S medical institutions.