After more than two decades of clinical failures, dead-end trials, and billions of dollars spent chasing a treatment that never materialized, NASH liver disease finally has an approved drug. In March 2024, the FDA granted accelerated approval to Rezdiffra (resmetirom), made by Madrigal Pharmaceuticals, for adults with noncirrhotic NASH who have moderate-to-advanced liver fibrosis (stages F2–F3). It is the first and only medication ever approved for this condition — a milestone that liver specialists had nearly stopped believing would come. The drug has since received conditional marketing authorization from the European Commission as well, making it the first approved MASH therapy on both sides of the Atlantic.
For readers of this site, the relevance is not abstract. Liver disease and brain health are more connected than most people realize. NASH — now officially renamed MASH, as part of a 2023 effort to drop the stigmatizing “nonalcoholic” label — drives systemic inflammation, insulin resistance, and vascular damage that researchers have increasingly linked to cognitive decline and dementia risk. A drug that can reverse liver fibrosis may, over time, reduce one of the quieter upstream threats to brain health. This article covers the science behind Rezdiffra, why so many drugs failed before it, what the clinical data actually shows, the cost and access realities, and what the next few years of development look like.
Table of Contents
- Why Did It Take Decades to Get a Drug for NASH Liver Disease?
- What Does the Clinical Evidence for Rezdiffra Actually Show?
- The NASH-to-Brain Connection — Why This Matters for Cognitive Health
- What Does Rezdiffra Cost, and Can Patients Actually Access It?
- The Naming Change from NASH to MASH — and Why It Matters More Than You Think
- What Is in the Pipeline Beyond Rezdiffra?
- Where This Goes from Here
- Conclusion
- Frequently Asked Questions
Why Did It Take Decades to Get a Drug for NASH Liver Disease?
The history of NASH drug development is a graveyard of promising candidates. For over twenty years, pharmaceutical companies poured resources into clinical trials that repeatedly came up empty. Elafibranor, a PPARα/δ agonist, failed to hit its primary endpoint. Obeticholic acid, an FXR agonist that once looked like the frontrunner, stumbled on safety and efficacy concerns. Selonsertib went through two negative Phase III trials before being abandoned. The pattern was so consistent that some researchers began questioning whether the disease could be treated pharmacologically at all. The reasons for these failures were not simple bad luck.
NASH is a disease defined by patient heterogeneity — the people who have it vary enormously in their underlying metabolic profiles, genetic predispositions, and rates of disease progression. The condition moves slowly, sometimes over decades, which makes it brutally difficult to show meaningful change within a typical trial window. Diagnosis has historically required invasive liver biopsies, creating enrollment barriers and dropout problems. And placebo response rates have been stubbornly high, sometimes above 10%, muddying the statistical waters. Compare this to a condition like hepatitis C, where viral clearance offers a clean binary endpoint, and you begin to see why NASH was such a uniquely difficult target. The Lancet Gastroenterology & Hepatology has documented this long arc of failure in detail, and the consensus view by the early 2020s was cautious at best. Rezdiffra did not emerge from a sudden breakthrough — it came from a mechanism (thyroid hormone receptor-beta agonism) that had been explored for years but that Madrigal refined with enough precision to finally clear the regulatory bar.
What Does the Clinical Evidence for Rezdiffra Actually Show?
The pivotal data comes from the Phase 3 MAESTRO-NASH trial, and the numbers deserve a careful look rather than a glancing headline. Among patients taking the 100 mg dose, 29.9% achieved NASH resolution without worsening fibrosis, compared to 9.7% on placebo — a statistically significant difference (P<0.001). The 80 mg dose showed a 25.9% resolution rate. For fibrosis improvement of at least one stage without worsening of the overall NASH activity score, the results were 25.9% for the 100 mg group and 24.2% for the 80 mg group, versus 14.2% on placebo (P<0.001 for both). These numbers are meaningful, but they come with an important caveat: roughly 70% of patients on the drug did not achieve NASH resolution, and about 74% did not see a full stage of fibrosis improvement. This is not a cure.
It is a treatment that works for a meaningful subset of patients, which is exactly the profile that led to an accelerated — not full — approval. The FDA’s continued approval is contingent on the ongoing MAESTRO-NASH-OUTCOMES trial, with data expected in 2027, which will need to demonstrate actual clinical outcomes like reduced progression to cirrhosis, liver transplant, or death. However, there is additional encouraging data beyond the fibrosis and resolution endpoints. Rezdiffra produced significant reductions in LDL cholesterol — down 13.6% at 80 mg and 16.3% at 100 mg by week 24, versus essentially no change on placebo. For a patient population that overwhelmingly carries cardiovascular risk, this is a notable secondary benefit. And in November 2025, Madrigal presented two-year data from the MAESTRO-NAFLD-1 cirrhosis arm at the AASLD Liver Meeting, showing significant improvements in liver stiffness, fat content, fibrosis biomarkers, and portal hypertension risk scores among 122 patients — suggesting the drug’s effects may extend, with further study, to more advanced disease.
