Pegbelfermin

Mechanism

A long-acting version of FGF21, a natural hormone that helps the liver burn fat and manage metabolism. It is being developed to treat fatty liver disease (NASH/MASH), a condition where fat builds up in the liver and causes inflammation and scarring. In clinical trials, it significantly reduced liver fat and improved markers of liver damage.

Effects

HEPATIC/METABOLIC SYSTEM: Pegbelfermin (BMS-986036) is a PEGylated recombinant analog of human fibroblast growth factor 21 (FGF21), developed primarily for nonalcoholic steatohepatitis (NASH). FGF21 is an endocrine hormone that acts through FGFR1c/β-klotho receptor complexes in liver, adipose tissue, and pancreas to regulate lipid and glucose metabolism [pharmacological]. PEGylation extends half-life from ~2 hours (native FGF21) to ~80 hours, enabling weekly subcutaneous dosing [pharmacokinetic]. HEPATIC: Reduces hepatic de novo lipogenesis by suppressing SREBP-1c and lipogenic gene expression. Increases hepatic fatty acid oxidation via PPARα activation. Stimulates adiponectin secretion from adipose tissue, which independently reduces hepatic fat content and inflammation [animal, Phase 2]. Phase 2 trials demonstrated 6.8% absolute reduction in hepatic fat fraction (MRI-PDFF) at 10mg weekly vs. 1.3% placebo reduction over 16 weeks — clinically meaningful [RCT — Sanyal et al., 2019]. Reduces hepatic inflammation markers (ALT, AST) and fibrosis biomarkers (Pro-C3, ELF score) [Phase 2]. METABOLIC: Improves lipid profile — reduces triglycerides (20-30%), LDL-C, and increases HDL-C [RCT]. Reduces body weight modestly (1-2 kg over 16 weeks) [Phase 2]. Improves insulin sensitivity and reduces fasting glucose [Phase 2]. Increases adiponectin levels 2-3x — the primary mediator of many downstream metabolic benefits [RCT]. CARDIOVASCULAR: Favorable CV biomarker profile — triglyceride reduction and HDL elevation suggest cardiovascular benefit, though no outcome trial data [Phase 2 biomarker data]. FIBROSIS: The key clinical question — NASH fibrosis improvement. Phase 2b (FALCON) trials showed trends toward fibrosis improvement but did not meet primary endpoints for fibrosis stage reduction, which contributed to Bristol-Myers Squibb's decision to deprioritize the program [Phase 2b]. This was a setback for the FGF21 class, though hepatic fat reduction was robust and consistent.

Practitioner Guide

AVAILABILITY: Pegbelfermin is NOT commercially available. It is an investigational drug that completed Phase 2 trials but was deprioritized by BMS after Phase 2b (FALCON) results did not meet fibrosis endpoints. As of 2025, development status is uncertain. Patients cannot access pegbelfermin outside of clinical trials. CLINICAL CONTEXT FOR PRACTITIONERS: Understanding pegbelfermin matters because: (1) FGF21 biology is central to metabolic health, (2) the NASH pipeline is rapidly evolving and practitioners need to understand where FGF21 agonists fit, (3) patients with NASH may ask about emerging therapies. NASH PIPELINE COMPARISON: Resmetirom (Rezdiffra, THR-β agonist) — FDA-approved March 2024, first approved NASH therapy. Reduces hepatic fat and improves fibrosis. Oral, daily dosing. This is the current standard. Semaglutide (GLP-1 RA) — Phase 3 for NASH (ESSENCE trial), robust hepatic fat reduction and fibrosis improvement, plus weight loss and cardiovascular benefits. Likely second approval. Pegbelfermin — robust hepatic fat reduction but failed to convincingly demonstrate fibrosis improvement in Phase 2b, limiting its competitive position. Other FGF21 analogs (efruxifermin/AKR-001) continue development with potentially better fibrosis data. SUPPORTING ENDOGENOUS FGF21: Since pegbelfermin is unavailable, practitioners can support the FGF21 axis through lifestyle measures: prolonged fasting and ketogenic diets are the most potent natural FGF21 stimulators (FGF21 is the 'starvation hormone'). Exercise increases FGF21 acutely. Cold exposure stimulates FGF21 via brown adipose tissue activation. Berberine (500mg 2-3x/day) may upregulate FGF21 expression. Metformin modestly increases FGF21 levels. PRACTICAL NASH MANAGEMENT (CURRENT): Weight loss (7-10% body weight) remains the most effective intervention. Exercise (150 min/week moderate-intensity). Mediterranean diet. Consider resmetirom for biopsy-proven NASH with F2-F3 fibrosis. GLP-1 RAs (semaglutide, liraglutide) for patients with NASH + obesity/T2DM. Vitamin E 800 IU/day for non-diabetic NASH (PIVENS trial). Pioglitazone 30-45mg/day for NASH with T2DM.

Evidence

• Efficacy and safety of fibroblast growth factor 21 analogs in metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis: A systematic review and network meta-analysis.

  Abdeljawad et al. (2026) — J Pharmacol Exp Ther — PMID: 41529428

  Across nine trials of FGF21 analogs in MASLD/MASH, pegbelfermin was included in the comparative evidence base; while other analogs ranked more strongly for fibrosis improvement, pegbelfermin remained part of the human clinical dataset and helps anchor its place in the broader FGF21 therapeutic landscape rather than showing standout superiority.

  moderate

Research Summary

TIER 1: Phase 2 RCT (Sanyal et al., 2019 — Lancet): pegbelfermin 10mg weekly SC reduced hepatic fat fraction by 6.8% (absolute) vs. 1.3% placebo over 16 weeks in NASH patients. Significant reductions in ALT, Pro-C3, and triglycerides. Phase 2b FALCON trials (FALCON-1 for F4 cirrhotic NASH, FALCON-2 for F3 bridging fibrosis): hepatic fat reduction confirmed but primary fibrosis endpoints not met (≥1 stage fibrosis improvement without worsening NASH). BMS deprioritized development. FDA: not approved; no active path to approval as of 2025. TIER 2: Reviews of FGF21 biology and therapeutic analogs (Geng et al., 2020). Systematic comparisons of NASH pipeline agents including FGF21 agonists (Vuppalanchi et al., 2021). Preclinical studies demonstrating FGF21's pleiotropic metabolic effects. Comparative reviews of pegbelfermin vs. efruxifermin (potentially superior FGF21 analog). Analysis of why hepatic fat reduction does not always translate to fibrosis improvement. TIER 3: Clinical trial participant experiences. Hepatology conference presentations (AASLD, EASL) on FALCON data. Expert opinion on the future of FGF21-based therapies in NASH. KEY FINDINGS: Pegbelfermin validates FGF21 as a potent regulator of hepatic lipid metabolism — the fat reduction was real, robust, and consistent. However, the failure to demonstrate fibrosis improvement was a critical commercial and clinical setback. The NASH field learned that reducing hepatic fat alone may not be sufficient to reverse fibrosis — inflammation, stellate cell activation, and other pathways may need to be targeted simultaneously. Efruxifermin (Fc-FGF21 fusion) may succeed where pegbelfermin struggled due to higher potency and different pharmacology. GAPS: No Phase 3 data. Unclear whether higher doses or longer treatment would improve fibrosis outcomes. No cardiovascular outcome data. Role in combination therapy (e.g., with resmetirom or GLP-1 RA) unexplored. ACTIVE TRIALS: Pegbelfermin development largely paused. Efruxifermin (Akero Therapeutics) in Phase 2b/3 as the leading FGF21 program. FGF21 biology continues to be actively studied across metabolic disease.