FDA Approves Resmetirom, the First Drug for Fatty-Liver Scarring (2024)

Table of Contents

1. What the FDA Did
2. Who the Approval Covers
3. How the Drug Works
4. The Trial Behind the Approval
5. What the 12-Month Results Showed
6. Warnings, Side Effects and Drug Interactions
7. What “Accelerated Approval” and the Other Designations Mean
8. What the Approval Does Not Do
9. The Disease: NASH, Now Also Called MASH
10. Dates and Status as of 11 October 2026
11. How the Approval Fits Earlier and Later FDA Actions
12. Primary Documents
13. Key Research Papers
14. Connections

1. What the FDA Did

The FDA news release, “FDA Approves First Treatment for Patients with Liver Scarring Due to Fatty Liver Disease,” is dated 14 March 2024. It states that the agency approved resmetirom “for the treatment of adults with noncirrhotic non-alcoholic steatohepatitis (NASH) with moderate to advanced liver scarring (fibrosis), to be used along with diet and exercise.”

The release quotes the acting director of the Office of Immunology and Inflammation in the FDA’s Center for Drug Evaluation and Research (CDER): “Previously, patients with NASH who also have notable liver scarring did not have a medication that could directly address their liver damage. Today’s approval … will, for the first time, provide a treatment option for these patients, in addition to diet and exercise.”

Resmetirom is a “novel” drug, which the FDA defines as a new drug never before approved or marketed in the U.S.: it is entry 5 of the 50 novel drugs on CDER’s “Novel Drug Approvals for 2024” list, dated 3/14/2024, “to treat noncirrhotic non-alcoholic steatohepatitis with moderate to advanced liver scarring.” A later FDA notice in the Federal Register (January 2026) gives the application number as New Drug Application (NDA) 217785 and records that the approval “represented the first permitted commercial marketing or use of the product.”

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2. Who the Approval Covers

The approval is limited to a defined group of adults:

• Diagnosis: NASH, which the FDA describes as the progression of fatty liver disease in which liver inflammation can, over time, lead to scarring.
• Scarring stage: moderate to advanced fibrosis. The January 2026 Federal Register notice restates the indication as “moderate to advanced liver fibrosis (consistent with stages F2 to F3 fibrosis).” The published phase 3 trial report describes the scarring scale as running from F0 (no fibrosis) to F4 (cirrhosis), so F2–F3 sits in the middle of that scale, short of cirrhosis.
• Noncirrhotic: people whose liver has not progressed to cirrhosis, the stage of severe, widespread scarring. (Background is on the site’s Cirrhosis page.)
• With diet and exercise: the indication pairs the drug with diet and exercise; in the trial, both drug and placebo groups received the standard care of counseling on healthy diet and exercise.

The FDA release cites an estimate that “approximately 6-8 million people in the U.S. have NASH with moderate to advanced liver scarring, with that number expected to increase.”

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3. How the Drug Works

The FDA release describes resmetirom as “a partial activator of a thyroid hormone receptor; activation of this receptor … in the liver reduces liver fat accumulation.”

The published phase 3 trial report names the specific target: it describes resmetirom as “an oral, liver-directed, thyroid hormone receptor beta-selective agonist.” The earlier phase 2 trial report says it was designed to improve NASH “by increasing hepatic fat metabolism and reducing lipotoxicity”. Both papers are listed under Key Research Papers below.

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4. The Trial Behind the Approval

According to the FDA release, the safety and efficacy were evaluated “based on an analysis of a surrogate endpoint at month 12 in a 54-month, randomized, double-blind placebo-controlled trial.” A surrogate endpoint is a measurement expected to predict a real health benefit without being that benefit itself; here it was what liver biopsies showed about inflammation and scarring.

• Entry requirement: a liver biopsy showing inflammation due to NASH with moderate or advanced scarring.
• Size and groups: 888 participants randomly assigned to placebo (294), 80 milligrams of resmetirom (298) or 100 milligrams of resmetirom (296), once daily.
• Background care: all groups received standard care for NASH, which the FDA describes as counseling for healthy diet and exercise.
• Length: the trial runs for 54 months. The 12-month biopsy results supported the approval; completing the full study is the required postapproval study to “verify and describe” the clinical benefit.

The published phase 3 report (Harrison 2024) describes the same ongoing trial with a primary analysis population of 966 patients and primary end points at week 52. The FDA’s figure of 888 and the paper’s figure of 966 come from different analyses; this page reports each as its source gives it.

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5. What the 12-Month Results Showed

The FDA release reports that at 12 months “liver biopsies showed that a greater proportion of subjects who were treated with [the drug] achieved NASH resolution or an improvement in liver scarring as compared with those who received the placebo.” Two separate measures were reported. The ranges reflect different pathologists’ readings of the same biopsies.

• NASH resolution with no worsening of scarring: 26% to 27% on 80 mg and 24% to 36% on 100 mg, compared with 9% to 13% on placebo with diet and exercise counseling.
• Scarring improvement with no worsening of NASH: 23% on 80 mg and 24% to 28% on 100 mg, compared with 13% to 15% on placebo.

The FDA added that “demonstration of these changes in a proportion of patients after just one year of treatment is notable, as the disease typically progresses slowly with a majority of patients taking years or even decades to show progression.”

The published trial report defines NASH resolution as including a reduction of at least 2 points in the NAFLD activity score (a biopsy score from 0 to 8, with higher scores indicating more severe disease), and fibrosis improvement as a drop of at least one scarring stage. In its 966-patient analysis it reported NASH resolution without worsening of fibrosis in 25.9% (80 mg) and 29.9% (100 mg) versus 9.7% on placebo, and fibrosis improvement in 24.2% and 25.9% versus 14.2%. Read either way, most participants on the drug did not reach either end point at 12 months, and a minority on placebo did.

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6. Warnings, Side Effects and Drug Interactions

The FDA release lists the following safety information:

• Most common side effects: diarrhea and nausea.
• Warnings and precautions: drug-induced liver toxicity and gallbladder-related side effects.
• Decompensated cirrhosis: the release states that use of the drug “should be avoided in patients with decompensated cirrhosis” (the FDA’s 2025 notice glosses hepatic decompensation as “worsening of liver function”), and that patients “should stop using” it if they develop signs or symptoms of worsening liver function during treatment. These are the FDA’s labeling statements, reported as such.
• Drug interactions: taking the drug together with certain other drugs, “in particular statins for lowering cholesterol, may result in potentially significant drug interactions.” The release refers health care providers to the full prescribing information for these interactions and the related dosage changes.

The published phase 3 report adds that diarrhea and nausea were more frequent with the drug than with placebo, and that serious adverse events occurred at similar rates across groups (10.9% on 80 mg, 12.7% on 100 mg, 11.5% on placebo). Decisions about any medicine belong with a clinician who knows the person’s full history and other prescriptions.

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7. What “Accelerated Approval” and the Other Designations Mean

The FDA release says resmetirom was approved under the accelerated approval pathway, “which allows for earlier approval of drugs that treat serious conditions and address an unmet medical need, based on a surrogate or intermediate clinical endpoint that is reasonably likely to predict clinical benefit.” The FDA’s patient page on the pathway explains the rest:

• Accelerated approval. The FDA instituted the accelerated approval regulations in 1992 and Congress extended the basis in 2012. A surrogate endpoint is “a marker … that is thought to predict clinical benefit, but is not itself a measure of clinical benefit.” Where confirmatory trials verify the benefit, the FDA generally ends the requirement; approval “may be withdrawn or the labeled indication of the drug changed if trials fail to verify clinical benefit.” For resmetirom the surrogate was biopsy improvement at 12 months; the clinical benefit is to be assessed after 54 months of treatment.
• Breakthrough Therapy. A designation for drugs for a serious condition where preliminary clinical evidence indicates a possible substantial improvement over available therapy; it brings intensive FDA guidance on the development program.
• Fast Track. A process to speed development and review of drugs for serious conditions that fill an unmet medical need, with more frequent meetings and written communication with the FDA.
• Priority Review. The FDA’s goal is to act on the application within 6 months, compared with 10 months under standard review. The FDA states that this “does not alter the scientific/medical standard for approval or the quality of evidence necessary.”

The release states that resmetirom received Breakthrough Therapy, Fast Track and Priority Review designations for this indication.

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8. What the Approval Does Not Do

• It does not cover cirrhosis. The indication is noncirrhotic NASH, and the release says use in decompensated cirrhosis is to be avoided.
• It is not a full (traditional) approval. The decision rests on a 12-month biopsy surrogate; continued approval depends on the ongoing 54-month study verifying clinical benefit.
• It does not show fewer deaths, transplants or liver failure. Those outcomes are what the full 54-month study is to assess; the approval itself is based on biopsy changes.
• It does not replace diet and exercise. The drug is approved “along with” them, and the trial compared it with placebo on top of diet and exercise counseling.
• It does not cover simple fatty liver. The indication requires NASH with moderate to advanced fibrosis, not liver fat alone.

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9. The Disease: NASH, Now Also Called MASH

The 2024 FDA release describes NASH as “a result of the progression of nonalcoholic fatty liver disease where liver inflammation, over time, can lead to liver scarring and liver dysfunction,” and says it is often associated with other health problems such as high blood pressure and type 2 diabetes.

By August 2025 the FDA was using the newer name. Its CDER notice of 15 August 2025 states: “MASH, also known as nonalcoholic steatohepatitis, is a serious liver disease,” and spells MASH out as metabolic-associated steatohepatitis. That notice describes MASH as a severe form of fatty liver disease that develops when fat buildup in the liver causes inflammation and scarring; lists obesity, type 2 diabetes, high triglycerides and high LDL cholesterol as conditions that increase the likelihood of developing it; and says it can progress to cirrhosis, worsening liver function, liver cancer, liver transplantation or death. It notes that many people have no symptoms until severe liver damage, and estimates that about 6% of U.S. adults (14.9 million people) have MASH.

The renaming came from a 2023 consensus process published in hepatology journals (Rinella 2023, under Key Research Papers), which replaced NAFLD with metabolic dysfunction-associated steatotic liver disease (MASLD) and kept the term steatohepatitis. How fatty liver connects to insulin resistance is covered on the NAFLD / MASLD and insulin resistance page.

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10. Dates and Status as of 11 October 2026

• 3 October 2010: per the FDA’s 2026 patent-term notice, the investigational new drug application (the exemption that permits clinical testing in people) became effective.
• 14 July 2023: the new drug application was first submitted.
• 14 March 2024: FDA approval under accelerated approval.
• 15 August 2025: the FDA approved a second medicine, semaglutide injection, for the same disease (see section 11).
• 27 January 2026: an FDA Federal Register notice, issued for a patent-term extension, again describes the indication as approved under accelerated approval, with continued approval that “may be contingent upon verification and description of clinical benefit in confirmatory trials.”

Status as of 11 October 2026: approved (accelerated approval), final action. A check of the Federal Register through 11 October 2026 found no FDA document withdrawing the approval, changing the indication, or converting it to traditional approval. The documents reviewed for this page do not report the results of the 54-month confirmatory study.

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11. How the Approval Fits Earlier and Later FDA Actions

2018: draft guidance for this disease. On 4 December 2018 the FDA announced a draft guidance, “Noncirrhotic Nonalcoholic Steatohepatitis With Liver Fibrosis: Developing Drugs for Treatment” (83 FR 62582, Docket No. FDA-2018-D-3632), “intended to assist sponsors in the clinical development of drugs for the treatment of noncirrhotic NASH with liver fibrosis.” The notice says the guidance also identifies knowledge gaps that are important challenges for drug development, and that it does not address cirrhosis caused by NASH. Like all draft guidance, it is not binding on the FDA or the public.

2019: a companion draft guidance for cirrhosis. On 7 June 2019 the FDA announced a separate draft guidance, “Nonalcoholic Steatohepatitis With Compensated Cirrhosis: Developing Drugs for Treatment” (84 FR 26685, Docket No. FDA-2019-D-1516), covering enrollment criteria, trial design, efficacy endpoints and safety for phase 3 trials in that later stage. The 2024 approval falls under the first, noncirrhotic category.

2024: the first approval. Resmetirom became the first drug approved for noncirrhotic NASH with moderate to advanced fibrosis.

2025: a second medicine. On 15 August 2025 the FDA approved semaglutide injection, a drug already approved for obesity or overweight and to reduce cardiovascular events, to treat MASH in adults with moderate-to-advanced fibrosis. It too was granted under accelerated approval, on a 72-week biopsy analysis of 800 participants in a trial that is to run 240 weeks; the FDA reported MASH resolution without worsening of scarring in 63% versus 34% on placebo, and scarring improvement without worsening of MASH in 37% versus 22%. The FDA notice says this drug “promotes weight loss and potentially other mechanisms not fully understood.” The same medicine’s 2024 heart-risk approval is on the 2024 semaglutide heart-risk page.

2025: a product-specific guidance. On 21 November 2025 the FDA listed resmetirom among the active ingredients for which it issued a new draft product-specific guidance (90 FR 52681, Docket No. FDA-2007-D-0369). The notice says such guidances give product-specific recommendations on, among other things, the design of bioequivalence studies to support abbreviated new drug applications (ANDAs).

2026: patent-term review. On 27 January 2026 the FDA published its determination of the drug’s regulatory review period for patent-extension purposes (91 FR 3507, Docket Nos. FDA-2024-E-2243 and FDA-2024-E-2244): 4,913 days in total, of which 4,668 days were the testing phase and 245 days the approval phase. The notice explains that this sets the maximum possible extension, which the U.S. Patent and Trademark Office then limits by statute; the patent holder sought 1,594 days, or 5 years.

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12. Primary Documents

1. U.S. Food and Drug Administration (2024). FDA Approves First Treatment for Patients with Liver Scarring Due to Fatty Liver Disease. FDA News Release, 14 March 2024 — fda.gov press announcement
2. U.S. Food and Drug Administration, CDER. Novel Drug Approvals for 2024 (entry 5, 3/14/2024) — fda.gov Novel Drug Approvals for 2024
3. U.S. Food and Drug Administration. Fast Track, Breakthrough Therapy, Accelerated Approval, Priority Review (patient information pages) — fda.gov Accelerated Approval
4. U.S. Food and Drug Administration, CDER (2025). FDA Approves Treatment for Serious Liver Disease Known as ‘MASH’. 15 August 2025 — fda.gov CDER notice
5. Food and Drug Administration, HHS (2018). Noncirrhotic Nonalcoholic Steatohepatitis With Liver Fibrosis: Developing Drugs for Treatment; Draft Guidance for Industry; Availability. Federal Register 83:62582–62583, 4 December 2018. Docket No. FDA-2018-D-3632 — FR Doc. 2018-26333
6. Food and Drug Administration, HHS (2019). Nonalcoholic Steatohepatitis With Compensated Cirrhosis: Developing Drugs for Treatment; Draft Guidance for Industry; Availability. Federal Register 84:26685–26687, 7 June 2019. Docket No. FDA-2019-D-1516 — FR Doc. 2019-11951
7. Food and Drug Administration, HHS (2025). Product-Specific Guidances; Draft and Revised Draft Guidances for Industry; Availability. Federal Register 90:52681–52683, 21 November 2025. Docket No. FDA-2007-D-0369 — FR Doc. 2025-20548
8. Food and Drug Administration, HHS (2026). Determination of Regulatory Review Period for Purposes of Patent Extension (resmetirom; product name omitted here). Federal Register 91:3507–3508, 27 January 2026. Docket Nos. FDA-2024-E-2243 and FDA-2024-E-2244 — FR Doc. 2026-01585

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Key Research Papers

1. Harrison SA, Bashir MR, Guy CD, Zhou R, Moylan CA, Frias JP, Alkhouri N, Bansal MB, Baum S, Neuschwander-Tetri BA, Taub R, Moussa SE (2019). Resmetirom (MGL-3196) for the treatment of non-alcoholic steatohepatitis: a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial. Lancet 394(10213):2012-2024. The 36-week phase 2 trial in 125 randomised adults reported a relative reduction in liver fat measured by MRI at weeks 12 and 36 compared with placebo — PubMed PMID: 31727409
2. Harrison SA, Taub R, Neff GW, Lucas KJ, Labriola D, Moussa SE, Alkhouri N, Bashir MR (2023). Resmetirom for nonalcoholic fatty liver disease: a randomized, double-blind, placebo-controlled phase 3 trial. Nature Medicine 29(11):2919-2928. A 52-week safety trial in adults with presumed NASH; adverse events in excess of placebo included diarrhea and nausea at the start of treatment — PubMed PMID: 37845512
3. Harrison SA, Bedossa P, Guy CD, Schattenberg JM, Loomba R, Taub R, et al.; MAESTRO-NASH Investigators (2024). A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis. New England Journal of Medicine 390(6):497-509. The biopsy trial whose 12-month results underlie the approval — PubMed PMID: 38324483
4. Rinella ME, Lazarus JV, Ratziu V, Francque SM, Sanyal AJ, Kanwal F, et al.; NAFLD Nomenclature consensus group (2023). A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Hepatology 78(6):1966-1986. The consensus that introduced the MASLD and MASH terms — PubMed PMID: 37363821
5. Sanyal AJ, Newsome PN, Kliers I, Østergaard LH, Long MT, Kjær MS, Cali AMG, Bugianesi E, Rinella ME, Roden M, Ratziu V; ESSENCE Study Group (2025). Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis. New England Journal of Medicine 392(21):2089-2099. The 72-week interim analysis behind the second approved MASH medicine — PubMed PMID: 40305708

PubMed Topic Searches

1. PubMed: resmetirom
2. PubMed: thyroid hormone receptor beta agonists and steatohepatitis
3. PubMed: MASH fibrosis treatment trials

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Connections

• FDA Actions of 2024
• FDA and Regulation
• Semaglutide Heart-Risk Indication (2024)
• Tirzepatide Shortage Ends (2024)
• Donanemab Alzheimer’s Approval (2024)
• Over-the-Counter Glucose Monitor (2024)
• FDA Ends the Semaglutide Shortage (2025)
• MASLD (Fatty Liver Disease)
• NAFLD / MASLD and Insulin Resistance
• Cirrhosis
• Liver Disease
• Type 2 Diabetes
• Choline Deficiency: Fatty Liver

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