A former senior executive at Madrigal Pharmaceuticals has filed a whistleblower lawsuit alleging that the company covered up liver safety concerns about Rezdiffra, its approved treatment for the liver disease MASH, and retaliated against him for raising them. The lawsuit was filed by Michael Charlton, the company’s former senior vice president and head of clinical development, in the US District Court for the Northern District of Illinois on October 9, and was disclosed in Madrigal’s third quarter securities filing, Fierce Biotech and STAT reported on November 4. The allegations are unproven and no court has made any finding.
Charlton joined Madrigal in October 2024 from a professorship at the University of Chicago. According to the complaint, he identified safety signals that included failures to recognise cases of hepatic decompensation in clinical studies and relatively high rates of liver toxicity reports in the FDA’s adverse event reporting system compared with other drugs. He also alleged discrepancies in two year data from an open label arm of the Phase 3 Maestro-NAFLD-1 trial in compensated MASH cirrhosis, presented at the European Association for the Study of the Liver congress.
The complaint alleges that chief executive Bill Sibold told Charlton to stop looking when he raised the congress data concerns. Five weeks later, in June 2025, Charlton was moved to a new position that the complaint describes as carrying a senior vice president title with no significant leadership, and he lost his seat on the clinical trial protocol review committee. He resigned on January 5, 2026. The suit accuses Madrigal of retaliation under federal whistleblower protection statutes and seeks reinstatement or monetary damages.
Rezdiffra was the first treatment approved for MASH, and it is Madrigal’s flagship product amid surging sales, as Fierce Biotech put it. That is why an allegation of censored safety data from the person hired to safeguard trial integrity carries weight beyond ordinary employment litigation. It is also, at this stage, one side’s account in a complaint. No company response was available in the sources read for this story, and none is invented here.