MASH Combination Therapy: Breaking the Monotherapy Ceiling

Monotherapy Doesn't Cure Most Patients—That's the Reality

Resmetirom and Semaglutide have arrived, but let's be blunt: only 25-37% of patients achieve the histologic ≥1-stage fibrosis improvement endpoint in pivotal trials¹². MASH resolution and lipid/transaminase improvements are evaluated on separate axes, but on this primary histologic benchmark the majority of patients fall short.

The key to breaking this ceiling is Combination Therapy. This article maps out the ideal drug pairings—FGF21 analogs with Resmetirom or GLP-1—and charts the roadmap to MASH complete remission.

The Ideal Partnership: Concrete Combination Strategies

We aim for synergistic effects by combining drugs with different mechanisms of action.

1. GLP-1 (Metabolic Backbone) + Anti-fibrotic Agent

Currently this strategy is being explored primarily at theoretical and early-trial levels; combination protocols are being designed with reference to ClinicalTrials.gov entries that change over time (specific NCT IDs vary by registration timing).

• Theoretical Background: Manage systemic weight and metabolism with GLP-1 receptor agonists (Semaglutide², Tirzepatide³) to cut off the "fuel (fatty acid) supply" to the liver. On top of that, directly strike the remaining intrahepatic inflammation and fibrosis signals with liver-specific agents like Resmetirom¹. This is a fusion of "defense and offense."
• Expected Effects (Hypothesis): Incremental fibrosis improvement, long-term maintenance of MASH resolution (not validated in short-term Phase 2/3 trials). Suppression of liver cancer development is a long-term outcome research topic that requires separate verification, and is not directly evaluated in current MASH combination Phase 2/3 trials.

2. Incretin Combinations (GLP-1 based combinations)

• GLP-1/GIP (Tirzepatide): SYNERGY-NASH (Phase 2b) showed dose-dependent MASH resolution and fibrosis improvement³. However, SYNERGY-NASH (n=190) and ESSENCE (n=800 interim analysis) are not head-to-head trials, so simple superiority comparisons warrant caution.
• GLP-1/Glucagon (Survodutide, etc.): Adds the energy expenditure enhancing effect of glucagon. Phase 2 (NEJM 2024) showed the 4.8 mg arm achieved ≥30% liver fat reduction in 67%, and MASH histologic improvement in 62% vs 14% placebo⁴. However, fibrosis ≥1-stage improvement was 34-36%, similar to Semaglutide monotherapy (36.8%)—Survodutide does not clearly surpass GLP-1 monotherapy on fibrosis at present and is positioned as a fat reduction driver.

Leading Actors in the Pipeline: The Rise of FGF21 Analogs

Following THR-β and GLP-1, FGF21 (Fibroblast Growth Factor 21) analogs are rapidly increasing their presence as the third pillar.

Pegozafermin (89bio) / Efruxifermin (Akero)

• Mechanism of Action (Hypothesis): FGF21 is a metabolic regulatory hormone produced in the liver. Beyond improving lipid metabolism and insulin sensitivity, direct anti-fibrotic effects via hepatic stellate cells have been proposed in preclinical and translational studies. The relative contribution of direct anti-fibrotic action vs metabolism-improvement-derived benefit in humans has not been established; clinical histology outcomes (fibrosis improvement rate) are reported separately as observational data.
• ENLIVEN Trial (Pegozafermin): Phase 2b reported fibrosis ≥1-stage improvement in F2-F3 patients of 27% in 44mg vs 7% placebo (p=0.008)⁵; 30mg arm 26% vs 7% (p=0.009). Safety and additive effects in combination trials with GLP-1 receptor agonists are drawing attention.
• HARMONY Trial (Efruxifermin): Phase 2b reported fibrosis ≥1-stage improvement of 39% in 28mg, 41% in 50mg vs placebo 20% (p=0.025/0.036)⁶.
• Characteristics: Within the Pegozafermin/Efruxifermin Phase 2b trial ranges, weight loss is smaller than GLP-1 agents while still intervening on liver fat and fibrosis (potential option for patients not seeking appetite suppression or non-obese MASH patients; Phase 3 readouts pending).

Diagnosis Revolution: Evolution of Biomarkers (NITs)

The evolution of therapeutics requires the evolution of diagnostic technologies. The shift from painful "liver biopsies" to blood tests and imaging diagnostics (NITs) is becoming decisive.

• FIB-4 Index: Basic screening. Essential for "pick-up" in primary care.
• ELF Score / PRO-C3: Markers to see the "activity" or "dynamic change" of fibrosis. Validation is currently underway in programs like the FDA's Biomarker Qualification Program, and future use for enrichment in trial designs and evaluation of treatment response is expected.
• VCTE (FibroScan): For Liver Stiffness Measurement (LSM), FDA advanced to the initial qualification step of accepting a Letter of Intent for VCTE-LSM as a surrogate endpoint in MASH trials on 2025-08-27. Full qualification and complete replacement of biopsy have not been achieved—currently positioned as a complementary measure.
• MRE (MR Elastography): One of the major non-invasive imaging modalities for liver stiffness, with strong sensitivity and reproducibility; increasingly adopted as a secondary/exploratory endpoint in many clinical trials (not yet a regulator-qualified "gold standard").

Conclusion: Towards Precision Medicine

Towards 2030, MASH treatment is expected to evolve from a one-size-fits-all approach to precision medicine. The following is not current guideline recommendation but an editorial framework organized as the author's outlook:

• Patients with Obesity Preponderance → GLP-1/GIP agents as the backbone
• Non-obese Patients with Liver Pathology Preponderance → Resmetirom or other liver-selective agents
• Patients with Advanced Fibrosis → Combination Therapy (GLP-1 + Resmetirom / FGF21 analog)

The arrival of two approved drugs is not the goal, but merely the first piece to solving this complex puzzle. Phase 3 combination trials, long-term outcome research, and NITs regulatory qualification each form independent milestones in this important era for overcoming MASH.

References & Clinical Trials

1. Harrison SA, et al. A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis (MAESTRO-NASH). N Engl J Med. 2024;390(6):497-509. PubMed / NCT03900429

2. Sanyal AJ, Newsome PN, et al. Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis (ESSENCE). N Engl J Med. 2025;392(21):2089-2099. PubMed / NCT04822181

3. Loomba R, et al. Tirzepatide for MASH with Liver Fibrosis (SYNERGY-NASH). N Engl J Med. 2024;391(4):299-310. PubMed / NCT04166773

4. Sanyal AJ, Newsome PN, et al. A Phase 2 Randomized Trial of Survodutide in MASH and Fibrosis. N Engl J Med. 2024. PubMed / NCT04771273

5. Loomba R, et al. Randomized, Controlled Trial of Pegozafermin in NASH (ENLIVEN). N Engl J Med. 2023;389(11):998-1008. PubMed / NCT04929483

6. Harrison SA, et al. Efruxifermin in NASH (HARMONY): a randomised, double-blind, placebo-controlled, Phase 2b trial. Lancet Gastroenterol Hepatol. 2023;8(12):1080-1093. PubMed / NCT04767529

7. Sanyal AJ, et al. Retatrutide in MASLD: a randomized Phase 2a liver fat substudy. Nat Med. 2024;30(7):2037-2048. PubMed

8. FDA. Rezdiffra (resmetirom) Prescribing Information. Madrigal Pharmaceuticals; revised December 2025. DailyMed current label

9. FDA. Wegovy (semaglutide) Prescribing Information. Novo Nordisk; revised March 2026. DailyMed current label