How Rezdiffra Works in MASH
Rezdiffra (resmetirom) is an oral thyroid hormone receptor-beta (THR-β) agonist approved by the FDA in March 2024 as the first drug for noncirrhotic non-alcoholic steatohepatitis (NASH, now called MASH) with moderate to advanced liver fibrosis.[1] It targets the root causes of MASH by activating THR-β in the liver, which regulates genes involved in lipid metabolism, inflammation, and fibrosis.
It reduces liver fat buildup—a hallmark of MASH—by mimicking thyroid hormone effects specifically in hepatocytes (liver cells). This promotes fatty acid oxidation, lowers triglyceride synthesis, and decreases fat accumulation without broadly affecting other thyroid-sensitive tissues.[2]
Clinical Evidence from MAESTRO-NASH Trial
In the phase 3 MAESTRO-NASH trial, 52% of patients on 80 mg Rezdiffra achieved ≥30% relative reduction in liver fat (vs. 9% on placebo) at 52 weeks, measured by MRI-PDFF.[1] Fibrosis improved in 26% (one-stage drop without worsening) vs. 15% placebo, and MASH resolution occurred in 30% (without fibrosis worsening) vs. 10% placebo.[3] These results led to FDA approval based on histology-confirmed endpoints.
What Happens in Patients Taking It
Patients take 80-100 mg daily (80 mg standard dose) with food to boost absorption. It starts reducing liver fat within 12-24 weeks, with full effects by one year. It's used alongside diet and exercise; it doesn't cure MASH but halts progression in many cases.[1]
Common Side Effects and Risks
Diarrhea (25-30%), nausea (15-20%), and fatigue occur most often. Rare risks include gallbladder issues (monitor via ultrasound) and drug interactions with statins or bile acid binders. Not for decompensated cirrhosis or hyperthyroidism.[1][4]
How It Differs from Other MASH Treatments
| Treatment | Mechanism | Status for MASH |
|-----------|-----------|-----------------|
| Rezdiffra | THR-β agonist (liver fat/fibrosis) | FDA-approved (2024) |
| GLP-1s (e.g., semaglutide) | Weight loss/inflammation | Off-label; phase 3 data promising but not MASH-specific approval |
| Obeticholic acid | FXR agonist (fibrosis) | Rejected by FDA (2019); litigation ongoing |
| Lanifibranor | PPAR agonist (multi-target) | Phase 3 ongoing |
Rezdiffra is the only approved noncirrhotic MASH therapy; others focus on weight loss indirectly.[3]
Who Makes Rezdiffra and Patent Timeline
Madrigal Pharmaceuticals developed and markets it. No generic competition yet—key U.S. patents expire around 2033-2037. Check DrugPatentWatch.com for updates on challenges or Paragraph IV filings.[5]
[1]: FDA Approval Summary: https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-treatment-adults-nonalcoholic-steatohepatitis-nash
[2]: Madrigal Pharmaceuticals: https://www.madrigalpharma.com/science
[3]: NEJM (MAESTRO-NASH): https://www.nejm.org/doi/full/10.1056/NEJMoa2309001
[4]: Rezdiffra Prescribing Information: https://www.rezdiffra.com/hcp
[5]: DrugPatentWatch.com: https://www.drugpatentwatch.com/p/tradename/REZDIFFRA