Amid surging sales of Rezdiffra, Madrigal Pharmaceuticals is facing a whistleblower lawsuit alleging that senior leadership censored serious liver-injury data related to the world’s first approved treatment for MASH and retaliated against the firm’s top clinical development head who tried to sound the alarm.
The damning lawsuit, filed by Michael Charlton, M.D., Madrigal’s former senior vice president and head of clinical development, accuses the company of disregarding patient safety by allegedly covering up liver safety concerns, breaching clinical-trial integrity and manipulating data presented at a medical conference.
The lawsuit was filed in the U.S. District Court for the Northern District of Illinois and disclosed in Madrigal’s third-quarter securities filing (PDF). It coincides with Rezdiffra’s milestone of crossing $1 billion in year-to-date sales for the first time since its landmark FDA approval in March 2024.
In a statement to Fierce, a Madrigal spokesperson said the company intends to defend itself vigorously.
“Rezdiffra has improved the lives of thousands of patients living with MASH, and Madrigal stands firmly behind the safety and effectiveness of our product,” the spokesperson said.
Charlton joined Madrigal from a professorship at the University of Chicago in October 2024. Upon his arrival, Charlton uncovered safety signals that allegedly contradicted the drug’s pristine narrative. According to the complaint, these included failure to recognize cases of hepatic decompensation in clinical studies as well as findings of high relative rates of liver toxicity from the FDA Adverse Event Reporting System (FAERS) compared to other drugs.
However, after querying FAERS based on the complaint, Citi analysts said they found “no outsized liver impact with Rezdiffra compared to marketed therapies for other liver-related conditions.”
The Citi team specifically looked at two primary biliary cholangitis drugs, neither of which has drawn liver toxicity concerns post-approval. After benchmarking the reported liver safety events against the estimated number of patients on each drug while excluding events such as hepatic cirrhosis related to MASH progression, the analysts “found that reported liver event rates were similar across the board.”
A large part of Charlton’s complaint also focuses on data integrity, as he reported being alarmed by the role that Madrigal’s co-founder and board director Rebecca Taub, M.D., played in assessing Rezdiffra’s clinical data.
According to the complaint, Taub held conflicts of interest while exerting influence over the evaluation of data for the phase 3 Maestro-NASH trial, which got Rezdiffra its accelerated approval. Charlton alleges that she was able to prescreen any Rezdiffra-associated liver adverse events and edit the narratives authored by investigators after she had been unblinded to treatment assignment. The edits happened before the reports were shared with the trials’ independent expert panels for assessment of the nature and cause of the events.
These include one case where Taub requested to remove a patient who had developed a life-threatening complication of their liver disease from an ongoing phase 3 trial after effective unblinding, according to the complaint.
“Maintaining the blind is a foundational principle of clinical-trial integrity,” the complaint reads. “Individuals responsible for trial conduct, monitoring, data management, and endpoint adjudication must remain blinded to treatment assignments.”
Charlton’s concerns aggravated when Madrigal presented two-year data from the open-label compensated MASH cirrhosis (stage F4c) arm of the phase 3 Maestro-NAFLD-1 trial at the European Association for the Study of the Liver (EASL) Congress last year.
Specifically, a quality-control review “revealed pervasive problems” and that “[a]lmost not data point or result in the presentation could be replicated from the underlying source data,” Charlton alleges in the complaint. These include the primary findings around improvements in liver stiffness.
Charlton brought the discrepancies to CEO Bill Sibold, who allegedly told Charlton to “stop looking.”
Findings from the Maestro-NAFLD-1 trial have partly inspired Madrigal’s plan to start another large phase 3 trial for Rezdiffra focused on patients with clinically significant portal hypertension.
In June 2025, five weeks after he flagged the EASL concerns to Sibold, Charlton was told he would be moving to a new position. According to the complaint, the position had “no significant leadership” despite bearing a senior vice president title. Simultaneously, he lost his position on Madrigal’s clinical trial protocol review committee.
Faced with a “hollowed-out” role, Charlton resigned on Jan. 5, 2026.
Despite a stellar third quarter, Madrigal’s stock price dropped 8% Tuesday, which Citi analysts attributed to the whistleblower lawsuit. The company’s shares again declined about 8% as of publication time Wednesday morning.