Skip to main content
    Educational information only. This site does not provide medical advice. Read full disclaimer
    PepTracker Pro
    Open the App
    Research-only content. This page is for educational purposes and does not constitute medical advice. Read full disclaimer →

    Pegozafermin

    Low Evidence

    Pegozafermin (development code BIO89-100) is an investigational, long-acting analog of fibroblast growth factor 21 (FGF21) being developed for metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH) and for severe hypertriglyceridemia (SHTG). Originally developed by 89bio and acquired by Roche in a deal announced in September 2025 (about $2.4 billion upfront and up to roughly $3.5 billion including a contingent value right), it uses site-specific glycoPEGylation to extend the very short half-life of native FGF21 to roughly 55-100 hours, enabling once-weekly or once-every-two-weeks subcutaneous dosing. FGF21 is a metabolic hormone that acts on liver, fat, and other tissues to improve insulin sensitivity, lower triglycerides, and exert direct anti-fibrotic and anti-inflammatory effects. In the Phase 2b ENLIVEN trial in biopsy-confirmed F2-F3 MASH, the 44 mg every-two-weeks dose produced at least a one-stage fibrosis improvement without worsening of MASH in about 27% of patients versus 7% on placebo, and MASH resolution without worsening of fibrosis in about 26% versus 2% on placebo, with benefits sustained through week 48. Pegozafermin holds FDA Breakthrough Therapy designation and EMA PRIME status for MASH and has advanced into the Phase 3 ENLIGHTEN program (ENLIGHTEN-Fibrosis in non-cirrhotic F2-F3 MASH and ENLIGHTEN-Cirrhosis in compensated F4 cirrhosis), plus the Phase 3 ENTRUST trial in SHTG.

    AliasesPegozafermin+5 more
    EvidenceLow Evidence
    Last Updated 2026-07-13
    Reading Time 6 min

    What It Is

    Pegozafermin (BIO89-100) is an investigational, once-weekly or once-every-two-weeks, subcutaneously injected analog of fibroblast growth factor 21 (FGF21). FGF21 is an endogenous hormone, secreted mainly by the liver, that coordinates the body's response to metabolic stress: it acts through FGF receptors and the co-receptor beta-Klotho in liver, adipose tissue, and the central nervous system to enhance insulin sensitivity, increase fat oxidation and energy expenditure, lower circulating triglycerides, and reduce hepatic fat, inflammation, and fibrosis. Native FGF21 is a poor drug because it is cleared within hours, so pegozafermin is engineered to overcome this: it is a recombinant FGF21 backbone modified by site-specific glycoPEGylation - the attachment of a polyethylene-glycol chain at a defined site via a glycan linker - which shields the molecule from rapid degradation and clearance and extends its half-life to roughly 55-100 hours while preserving receptor activity. The drug was developed by 89bio and, in a transaction announced in September 2025, is being acquired by Roche (through Genentech) for approximately $2.4 billion in cash upfront plus a contingent value right of up to about $6.00 per share, for a potential total of around $3.5 billion; the deal gives Roche a late-stage FGF21 asset to pair with its broader cardiometabolic and MASH ambitions. Pegozafermin's lead indication is MASH, the progressive, inflammatory, fibrosing form of metabolic (nonalcoholic) fatty liver disease, where it is positioned as a liver-directed therapy that works through a mechanism distinct from the incretin (GLP-1-based) drugs - and potentially complementary to them. Its second indication is severe hypertriglyceridemia (SHTG), a condition of dangerously high blood triglycerides that raises the risk of acute pancreatitis, where FGF21 pathway activation drives large triglyceride reductions.

    Also known as: Pegozafermin, BIO89-100, glycoPEGylated FGF21 analog, FGF21 analogue (89bio / Roche), Roche / Genentech FGF21 analog, pegozafermin (MASH)

    Regulatory Status

    Why Researchers Study It

    Pegozafermin is one of the most advanced FGF21 analogs and a key test of whether directly engaging the FGF21 metabolic pathway can reverse liver fibrosis in MASH - the endpoint that regulators care most about - rather than only reducing liver fat. Because it works through a mechanism entirely different from the GLP-1/GIP/glucagon incretin drugs, it is studied both as a standalone MASH and severe-hypertriglyceridemia therapy and as a potential future combination partner for incretin-based weight-loss agents. Roche's acquisition and the parallel FGF21 competition with efruxifermin have made pegozafermin a closely watched marker of where the MASH drug field is heading.

    Proposed Mechanisms

    • FGF21 receptor agonism: pegozafermin activates FGF receptor complexes (notably FGFR1c) together with the co-receptor beta-Klotho in liver, adipose tissue, and other metabolic tissues, reproducing the actions of native FGF21.
    • Direct hepatic effects: reduces hepatic de novo lipogenesis and liver fat, and exerts anti-inflammatory and anti-fibrotic actions on liver cells, aiming to reverse steatohepatitis and fibrosis.
    • Improved insulin sensitivity and lipid handling: enhances glucose uptake and fat oxidation in peripheral tissues and markedly lowers circulating triglycerides, addressing the metabolic drivers of MASH and severe hypertriglyceridemia.
    • Adipose-tissue signaling: acts on fat to promote adiponectin secretion and healthier lipid storage, part of the broader FGF21 metabolic program.
    • glycoPEGylation half-life extension: site-specific attachment of a PEG chain via a glycan linker protects the FGF21 backbone from rapid clearance, extending the half-life to roughly 55-100 hours and enabling weekly or every-two-weeks subcutaneous dosing.

    Evidence Snapshot

    Low Evidence
    Low
    Medium
    High
    Study Type Model Outcome Link
    RCT (human, Phase 2b - ENLIVEN) Biopsy-confirmed F2-F3 (non-cirrhotic) MASH; subcutaneous pegozafermin (including 44 mg every 2 weeks and 30 mg weekly) vs placebo over 24 weeks with data sustained to week 48 At least one-stage fibrosis improvement without worsening of MASH in ~27% (44 mg Q2W) vs ~7% placebo (p=0.008); MASH resolution without worsening of fibrosis in ~26% vs ~2% placebo (p=0.0005); reductions in liver fat, liver enzymes, and triglycerides Source
    RCT (human, Phase 3 - ENLIGHTEN-Fibrosis, ongoing) Non-cirrhotic F2-F3 MASH; ~1,000 patients randomized 1:1:1 to 30 mg weekly, 44 mg every 2 weeks, or placebo; co-primary histology endpoints at week 52 Pivotal trial designed to confirm fibrosis improvement and MASH resolution; enrolling/ongoing, no readout yet Source
    RCT (human, Phase 3 - ENLIGHTEN-Cirrhosis, ongoing) Compensated (F4) cirrhosis due to MASH; ~760 patients randomized 1:1 to 30 mg weekly vs placebo; interim primary endpoint of fibrosis regression from F4; NCT06419374 Pivotal trial in compensated cirrhosis; recruiting as of 2026, primary completion estimated 2028 Source

    Commonly Discussed Benefits

    Researching Pegozafermin? Track it, set reminders, and keep notes in the free app.

    Track in App

    Safety & Cautions

    • Investigational and not approved: pegozafermin is in Phase 3 development for MASH and severe hypertriglyceridemia and is not available by prescription; its ability to improve fibrosis in the pivotal Phase 3 trials remains to be confirmed.
    • No self-sourcing: pegozafermin is a proprietary, engineered glycoPEGylated FGF21 biologic studied only in controlled trials. Material sold online as 'pegozafermin', 'FGF21', or 'BIO89-100' is not the clinical drug and cannot be assumed authentic, pure, or safe.
    • Gastrointestinal and injection-site effects: the most commonly reported adverse effects in trials are nausea, diarrhea, and injection-site reactions, generally mild-to-moderate.
    • FGF21-class considerations: agents in this class have been examined for possible effects on appetite, bone-turnover markers, and blood pressure; the long-term significance of these signals is still being studied.
    • Surrogate vs clinical endpoints: much of the supportive data is from a 24- to 48-week Phase 2b trial using liver histology and non-invasive markers; long-term outcomes (progression to cirrhosis, liver-related events) require the ongoing Phase 3 program.
    • Not a weight-loss drug: unlike incretin agonists, pegozafermin is a liver- and lipid-directed therapy; it should not be conflated with GLP-1-based obesity medications, though the two mechanisms may eventually be combined.

    Comparisons

    See how Pegozafermin compares to related peptides:

    Calculator Tools

    Use our research tools to explore dosing and reconstitution data:

    Citations

    1. [1] Randomized, Controlled Trial of the FGF21 Analogue Pegozafermin in NASH (ENLIVEN) - New England Journal of Medicine PubMed
    2. [2] Roche enters into a definitive merger agreement to acquire 89bio and its Phase 3 FGF21 analog for MASH - Roche media release (Sept 18, 2025) PubMed
    3. [3] 89bio Initiates Phase 3 ENLIGHTEN-Fibrosis Trial of Pegozafermin in Non-Cirrhotic MASH with Fibrosis - 89bio PubMed
    4. [4] 89bio Initiates Phase 3 ENLIGHTEN-Cirrhosis Trial of Pegozafermin in MASH with Compensated Cirrhosis - 89bio PubMed
    5. [5] A Study to Evaluate the Efficacy and Safety of Pegozafermin in Participants With Compensated Cirrhosis Due to MASH (ClinicalTrials.gov NCT06419374) PubMed
    6. [6] 89bio Receives EMA PRIME Status for Pegozafermin in the Treatment of MASH with Fibrosis and Compensated Cirrhosis - 89bio PubMed

    Keep researching in the app

    • Log Pegozafermin to your private tracker
    • Set a dosing reminder
    • Compare it side-by-side with your stack

    Related Peptides

    Tirzepatide

    High Evidence

    A dual GIP/GLP-1 receptor agonist FDA-approved for type 2 diabetes, weight management, and MASH with liver fibrosis.

    Survodutide

    Medium Evidence

    A dual GLP-1/glucagon receptor agonist with FDA Breakthrough Therapy designation for MASH and Priority Review NDA filed February 2026. Phase 3 SYNCHRONIZE-1 reported 16.6% weight loss at 76 weeks; approval possible Q3 2026.

    Mazdutide

    High Evidence

    The first dual GCG/GLP-1 receptor agonist approved in China for obesity and T2D, with Phase 3 showing up to 20.1% weight loss at the 9 mg dose and superiority over semaglutide.

    Pemvidutide

    Medium Evidence

    A GLP-1/glucagon dual receptor agonist with FDA Breakthrough Therapy Designation for MASH, showing strong weight loss and liver benefits in Phase 2 trials.

    Efocipegtrutide

    Medium Evidence

    Efocipegtrutide (Hanmi code HM15211) is an investigational, long-acting, once-weekly GLP-1/GIP/glucagon 'triple' receptor agonist being developed primarily for metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH) rather than obesity alone. It is built on Hanmi's LAPSCovery platform as a chemical conjugate of a chimeric tri-agonist peptide (TA15211) fused to a human IgG4 Fc fragment, which extends its half-life via FcRn-mediated recycling and enables weekly subcutaneous dosing. By adding glucagon-receptor activation to the GLP-1/GIP dual mechanism, efocipegtrutide is designed to combine appetite suppression and glycemic control with increased energy expenditure and direct hepatic anti-steatotic, anti-inflammatory, and anti-fibrotic effects. In a Phase 1b/2a study in obese subjects with non-alcoholic fatty liver disease, 12 weeks of treatment reduced liver fat by roughly 20% to 59% (dose-dependent, MRI-PDFF) versus about 6% on placebo. It has FDA Fast Track designation for MASH and orphan-drug designations from the FDA and EMA for primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and idiopathic pulmonary fibrosis (IPF). The 52-week adaptive Phase 2 HM-TRIA-201 study (NCT04505436) in biopsy-confirmed MASH with fibrosis is the pivotal read the field is watching.

    Efruxifermin

    Low Evidence

    Efruxifermin (development codes EFX, AKR-001; originally AMG 876) is an investigational, once-weekly, subcutaneously injected analog of the metabolic hormone fibroblast growth factor 21 (FGF21) being developed by Akero Therapeutics for metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH), including both pre-cirrhotic fibrosis and compensated (F4) cirrhosis. It is a bivalent Fc-FGF21 fusion protein - two engineered FGF21 sequences fused to a human immunoglobulin (IgG1) Fc domain - a design distinct from the glycoPEGylation used by its main FGF21-class rival, pegozafermin. The Fc fusion extends the very short half-life of native FGF21 to support once-weekly dosing while preserving agonism at FGF receptors (FGFR1c/2c/3c) together with the co-receptor beta-Klotho. In the 96-week Phase 2b HARMONY trial in biopsy-confirmed F2-F3 MASH, at least a one-stage improvement in fibrosis without worsening of MASH was reached by about 75% of patients on 50 mg and 46% on 28 mg versus 24% on placebo (published in The Lancet, August 2025). In the Phase 2b SYMMETRY trial in compensated MASH cirrhosis, about 39% of 50 mg patients with paired week-96 biopsies achieved reversal of cirrhosis without worsening of MASH versus 15% on placebo (published in the New England Journal of Medicine). Efruxifermin holds FDA Breakthrough Therapy designation and has advanced into the Phase 3 SYNCHRONY program (SYNCHRONY Histology in F2-F3 MASH, SYNCHRONY Outcomes in F4 compensated cirrhosis, and SYNCHRONY Real-World in non-invasively diagnosed MASH/MASLD, whose double-blind portion completed enrollment with safety results expected in 2026).

    Efimosfermin Alfa

    Low Evidence

    Efimosfermin alfa (development code BOS-580) is an investigational, long-acting, engineered analog of the metabolic hormone fibroblast growth factor 21 (FGF21) being developed by GSK - which acquired the molecule from Boston Pharmaceuticals in May 2025 for $1.2 billion upfront and up to $800 million in milestones (potential ~$2 billion total) - for steatotic liver disease, principally metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH). Its defining feature is a very long half-life engineered to allow once-monthly subcutaneous dosing - the least frequent schedule among the leading FGF21 analogs, contrasting with the once-weekly or every-two-weeks dosing of efruxifermin (an Fc-FGF21 fusion) and pegozafermin (a glycoPEGylated FGF21). Like the rest of the class, it activates FGF receptors (FGFR1c/2c/3c) together with the co-receptor beta-Klotho to cut liver fat, improve insulin sensitivity, lower triglycerides, and drive direct anti-inflammatory and anti-fibrotic effects in the liver. In a 24-week Phase 2 trial in biopsy-confirmed F2-F3 MASH, once-monthly efimosfermin achieved at least one-stage fibrosis improvement without worsening of MASH in about 45% of patients and MASH resolution without worsening of fibrosis in about 68%, both significantly better than placebo (published in The Lancet, 2025). It holds FDA Breakthrough Therapy designation and EMA PRIME (Priority Medicines) status for MASH, and has advanced into the Phase 3 ZENITH program (ZENITH-1 and ZENITH-2 in F2-F3 MASH), with a Phase 3 program in compensated (F4) MASH cirrhosis also underway; GSK has guided to a first potential launch around 2029.