Retatrutide (LY3437943) is an investigational triple hormone receptor agonist targeting GIP, GLP-1, and glucagon receptors. It is currently in Phase 3 clinical trials (TRIUMPH program) for the treatment of obesity, obstructive sleep apnea, and metabolic dysfunction.

Is retatrutide FDA approved?

No, as of 2026, retatrutide has not yet been approved by the FDA or EMA. It is currently undergoing Phase 3 clinical trials focusing on safety and efficacy markers including weight-loss, liver fat reduction, and dysesthesia tracking.

What makes retatrutide different from tirzepatide or semaglutide?

Unlike semaglutide (a single GLP-1 agonist) and tirzepatide (a dual GIP/GLP-1 agonist), retatrutide adds a third mechanism: glucagon receptor agonism. This triple-action approach aims to significantly increase energy expenditure while reducing appetite.

Retatrutide Liver Fat Reduction Nash Phase 2 Results

Retatrutide liver fat reduction NASH phase 2 results reveal impressive outcomes from a 48-week trial in obese patients with metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as NAFLD).[1] Higher doses of retatrutide led to up to 86% relative reductions in liver fat content, with 93% of participants on the top dose achieving normalization below 5% liver fat by week 48.[2][3][4] These findings, from a subset analysis of the Retatrutide TRIUMPH-1 and TRIUMPH-2 obesity trial results, highlight retatrutide's potential to resolve hepatic steatosis and support its role in early NASH intervention.[1][2]

Introduction to Retatrutide Liver Fat Reduction NASH Phase 2 Results

Retatrutide liver fat reduction NASH phase 2 results come from a dedicated subset of obese adults dealing with liver fat buildup.[1] This trial focused on how well the drug could shrink liver fat, a key step in stopping MASLD from worsening into NASH, which involves inflammation and scarring.[5] The data provide strong evidence of retatrutide's efficacy in this challenging condition, with dose-dependent improvements that surpassed placebo across all metrics.[2][3]

Overview of the Phase 2 Trial Design and Patient Population

The phase 2 trial was a randomized, placebo-controlled study lasting 48 weeks.[1] It included 98 obese adults aged 18-75 with MASLD/NAFLD, defined by at least 5% liver fat plus cardiometabolic risks like high blood sugar or cholesterol.[1][2]

Participants received weekly subcutaneous injections of retatrutide at doses of 1 mg, 4 mg, 8 mg, or 12 mg, or placebo.[1][2] Baseline liver fat ranged from 15.6% to 21.0% across groups, measured precisely with MRI-proton density fat fraction (MRI-PDFF).[2]

This design allowed researchers to track dose-dependent changes in liver fat over time. Results were presented at medical conferences like the American Diabetes Association (ADA) and American Association for the Study of Liver Diseases (AASLD).[2][3]

Why Retatrutide Targets Liver Fat in MASLD/NAFLD

MASLD affects up to 30% of adults worldwide, often linked to obesity and type 2 diabetes.[5] Excess liver fat, or steatosis, is the first stage and can progress to NASH if untreated.[6]

Retatrutide stands out because it not only cuts weight but directly boosts liver fat breakdown.[4] Its unique action on multiple hormones helps burn fat in the liver, addressing the root cause early.[4] By resolving steatosis, retatrutide could prevent fibrosis and cirrhosis in many patients, as evidenced by the retatrutide liver fat reduction NASH phase 2 results.[1][3]

Primary Endpoint: Liver Fat Reduction at 24 Weeks

The main goal was percent change in liver fat at 24 weeks using MRI-PDFF.[1][2] All retatrutide doses beat placebo, which showed a slight +0.3% increase.[2]

Doses showed clear dose-response: 1 mg cut 43%, 4 mg 57%, 8 mg 81%, and 12 mg 82%.[2] Normalization rates (liver fat <5%) reached 79% for 8 mg and 86% for 12 mg.[2][3] These rapid changes suggest retatrutide works quickly on liver fat, independent of full weight loss effects.[4]

What is Retatrutide? Mechanism of Action

Retatrutide, developed by Eli Lilly as LY3437943, is an investigational drug for obesity, diabetes, and liver diseases.[1] Unlike single-target drugs, it activates three key hormone receptors at once.[4] This triple action leads to greater fat loss, especially in the liver.[4]

Early data show it outperforms dual agonists like tirzepatide in weight and liver fat reduction.[3] The retatrutide liver fat reduction NASH phase 2 results underscore this advantage clearly.[1][2]

For more on related therapies, see our guide to tirzepatide for NASH and liver fat reduction.

Triple Hormone Agonist: GIP, GLP-1, and Glucagon Receptors

Retatrutide mimics three gut hormones:

GLP-1 (glucagon-like peptide-1): Slows digestion, reduces appetite, boosts insulin.[4]
GIP (glucose-dependent insulinotropic polypeptide): Improves insulin sensitivity and fat metabolism.[4]
Glucagon: Raises energy use, promotes fat burning in liver and body.[4]

Together, they create synergy for metabolic health. This combo explains the strong liver fat effects seen in trials.[1][4]

How Glucagon Agonism Enhances Liver Fat Reduction

Glucagon is key for liver-specific benefits. It stimulates fatty acid oxidation and ketone production, directly clearing liver triglycerides.[4]

In the trial, beta-hydroxybutyrate (a fat-burning marker) rose 78-181% by week 24.[1] This glucagon boost sets retatrutide apart from GLP-1/GIP drugs alone. Experts note glucagon addition "may result in greater efficacy in NAFLD/NASH".[4]

Developer: Eli Lilly (LY3437943) and Dosing Regimen

Eli Lilly is advancing retatrutide through late-stage trials.[1] Dosing starts low and ramps up weekly to minimize side effects: e.g., 2 mg → 4 mg → 8 mg → 12 mg over months.[1][2]

All doses were safe in this liver subset, mirroring obesity studies.[1] Maintenance at 8-12 mg sustained benefits to week 48.[3]

Retatrutide Liver Fat Reduction NASH Phase 2 Results: Efficacy at Week 24

At the primary endpoint of 24 weeks, retatrutide liver fat reduction NASH phase 2 results were striking. Higher doses nearly eliminated excess liver fat, far surpassing placebo.[2] MRI-PDFF confirmed these changes were real and consistent.[2]

This early efficacy points to retatrutide as a fast-acting option for steatosis. Here's a summary table of the key results:[2]

Dose	Week 24 Relative Reduction	Normalization Rate (<5% Liver Fat)
1 mg	-43%[2]	Not primary focus
4 mg	-57%[2]	Emerging
8 mg	-81%[2]	79%[2][3]
12 mg	-82%[2]	86%[2][3]
Placebo	+0.3%[2]	Minimal

Dose-Dependent Reductions: 1mg (43%), 4mg (57%), 8mg (81%), 12mg (82%)

Liver fat dropped in a clear dose pattern:

1 mg: 43% relative reduction[2]
4 mg: 57%[2]
8 mg: 81%[2]
12 mg: 82%[2]

Placebo increased by 0.3%.[2] All differences were statistically significant (p<0.001).[1][2] Lower doses still helped, but 8-12 mg hit near-maximal effects around 20% body weight loss.[1]

Placebo Comparison: +0.3% Increase

Placebo patients saw liver fat rise slightly, reflecting disease progression without intervention.[2] Retatrutide reversed this trend dramatically. This contrast underscores the drug's disease-modifying potential.[1]

Normalization Rates (<5% Liver Fat): 79-86% at Higher Doses

By week 24, 79% on 8 mg and 86% on 12 mg normalized liver fat (<5%).[2][3] This means most participants' livers looked healthy again. Such high rates are rare in early trials.[3]

Sustained Retatrutide Liver Fat Reduction at Week 48

Retatrutide liver fat reduction NASH phase 2 results held strong through 48 weeks.[1][3] High doses maintained over 80% reductions, with even higher normalization.[3][4] Long-term data confirm durability without rebound.

Liver volume and enzymes also improved alongside.[1] The table below extends the week 24 data:[3]

Dose	Week 48 Relative Reduction	Normalization Rate (<5% Liver Fat)	Steatosis Resolution
8 mg	-81.7-82%[3]	89%[3]	>85%[1][3]
12 mg	-86%[3]	93%[3]	>85%[1][3]
Placebo	+4.6%[3]	Minimal	Low

Long-Term Results: 8mg (81.7-82%), 12mg (86%)

At 48 weeks:

8 mg: 81.7-82% reduction[3]
12 mg: 86%[3]

Over 80% of high-dose patients achieved ≥70% fat drop.[1] These sustained effects link to ongoing weight loss and metabolic shifts.[4]

Steatosis Resolution: >85% in 8mg/12mg Groups, 93% Normalization at 12mg

Steatosis resolved in >85% on 8-12 mg.[1][3] Normalization hit 89% (8 mg) and 93% (12 mg).[3] Nearly all high-dose participants reached normal levels.

This resolution rate exceeds many prior therapies.[3] It positions retatrutide strongly for NASH prevention. Learn more in our MASLD/NAFLD overview guide.

Correlations with Weight Loss (~20% BW for Maximal Effect)

Liver fat changes tracked linearly with weight loss.[1] About 20% body weight drop maximized benefits.[1] Other links included lower triglycerides, insulin resistance (HOMA2-IR), and hormones like leptin/FGF-21.[1]

Weight loss drives results, but glucagon adds extra liver punch.[4] Strategies for preventing muscle loss during Retatrutide weight loss are crucial for long-term metabolic health.

Secondary Outcomes: Weight Loss and Metabolic Improvements

Beyond liver fat, retatrutide improved overall health in the retatrutide liver fat reduction NASH phase 2 results.[1] Weight loss reached 25%+, with big drops in harmful fats and biomarkers.[1][2] These changes reduce heart disease risk, common in MASLD patients.[5]

Body Weight Reduction: 23.8-25.9% at Higher Doses

High doses shone:

8 mg: -22.8% to -23.8%[1][2]
12 mg: -24.2% to -25.9%[1][2]

100% on 8-12 mg lost ≥5% weight.[1] This surpasses semaglutide or tirzepatide in head-to-head data.[3] These weight reductions were sustained through week 48, with dose escalation ensuring tolerability.[1]

Visceral and Subcutaneous Fat Losses: Up to 48% and 44%

Visceral (organ) fat fell up to 48%, subcutaneous up to 44% at 48 weeks.[1][2] These deep fat losses improve insulin sensitivity.[1] Liver fat correlated strongly with visceral reductions.[1]

Overall body composition shifted healthier. This supports long-term metabolic health in obese NAFLD patients. Check Eli Lilly's full pipeline for updates: /eli-lilly-pipeline-2026-obesity-diabetes-nash.

Biomarker Changes: Triglycerides (-35-40%), Insulin Sensitivity, Lipids

Key improvements included:

Triglycerides: -35-40%[1]
Fasting insulin: -37-71%[1]
HOMA-IR: -36-69%[1]
Non-HDL cholesterol: -25-27%[1]
Adiponectin up 30-99%[1]

Blood pressure dropped ~14 mmHg.[1] Leptin fell 29-56%, signaling less fat storage.[1] These shifts enhance liver health indirectly and align with guidelines for MASLD management.[6]

Safety Profile and Side Effects in Retatrutide Liver Fat Phase 2 Trial

Safety in retatrutide liver fat reduction NASH phase 2 results matched broader obesity trials.[1] No liver toxicity emerged over 48 weeks.[1] Side effects were mild to moderate, mostly gut-related, with low discontinuation rates.[1]

The profile supports safe use in liver patients. For specific management, see guidance on managing Retatrutide side effects like dysesthesia.

No Hepatotoxicity Signals Through 48 Weeks

Liver enzymes (ALT/AST) did not worsen; some improved with treatment.[1] No drug-induced liver injury or hepatotoxicity signals reported across all doses.[1]

This is crucial for NASH trials, where liver safety is paramount. Retatrutide proved exceptionally clean, even in patients with elevated baseline enzymes.[1]

Tolerability Similar to Obesity Trials

GI tolerability was good, with nausea affecting 40-60% (mostly mild, dose-dependent), vomiting 20-30%, and diarrhea 15-25%.[1] Symptoms peaked during escalation and resolved over time.

Heart rate increased mildly (5-10 bpm) but remained within safe limits.[1] Discontinuation due to adverse events was low: 5-8% overall, 6-12% at highest doses, comparable to placebo (4%).[1]

Serious adverse events occurred in 2-5% of participants, none liver-related or unexpected.[1]

Common Side Effects: Manageable Like Other GLP-1 Agonists

Dose escalation minimized issues. Common effects mirror semaglutide/tirzepatide: transient GI upset, injection-site reactions (<10%).[1]

No new safety signals in the liver subset. Long-term monitoring in phase 3 confirms the favorable profile.[1]

Clinical Trial Status and NASH Implications

The trial (NCT04881760) completed with full 48-week data.[1] It was a NAFLD/MASLD subset from a larger obesity study.[1] Implications for NASH are promising: resolving steatosis early may halt progression.[3][6]

See Retatrutide TRIUMPH-4 trial metabolic benefits for broader context on cardiometabolic outcomes.

Trial Completion: NCT04881760, Subset of Obesity Study (n=98)

Primary analysis at 24 weeks, extension to 48.[1] Small but robust with precise imaging.[2] Obesity-focused, so not biopsy-proven NASH.

Still, steatosis resolution is a strong surrogate endpoint for early disease.[3]

Potential for NASH: Resolving Steatosis to Prevent Progression

No approved NASH drugs exist yet.[6] Retatrutide's 80-90% resolution rates could fill this gap.[1][3] Glucagon's role enhances liver targeting.[4]

Pilot data support "bottom-up" therapy to prevent fibrosis.[3] This aligns with guidelines emphasizing fat clearance first.[6]

Limitations: Small Sample, Obesity-Focused Not Pure NASH Histology

n=98 limits power for rare events.[1] No histology for fibrosis/inflammation.[1] Longer trials needed for NASH endpoints like biopsy regression.

Phase 3 obesity data will inform liver applications.[1] Evidence is promising but preliminary.

FDA Approval Status and Future Phase 3 Trials

Retatrutide is not FDA-approved yet.[1] Phase 3 obesity trials (TRIUMPH program) are ongoing, with liver substudies possible.[1] NDA submission eyed for late 2026—track the Retatrutide NDA submission and FDA PDUFA timeline.

Current Legal Status: Not FDA Approved, Phase 3 Ongoing

Investigational only; no legal off-label use.[1] For pre-approval options, see accessing Retatrutide via compounding pharmacies before approval.

It follows semaglutide/tirzepatide successes but promises more.[3]

Ongoing Trials: Obesity Phase 3, Potential Liver-Specific Studies

TRIUMPH-1/2 showed superior weight loss (>25%).[1] Liver phase 3 (e.g., NCT05929066) may follow.[1] Combinations like tirzepatide + retatrutide test fatty liver further.

Comparisons to Semaglutide/Tirzepatide in NASH

Retatrutide outperforms:

Semaglutide: ~50-65% liver fat reduction in NAFLD trials vs. retatrutide's 82-86%.[3]
Tirzepatide: ~60-75% reductions, but less normalization (60-70% vs. 93%).[3]

Glucagon provides the edge in steatosis resolution.[3][4] Retatrutide liver fat reduction NASH phase 2 results set a new benchmark.[1][3]

Phase 3 Outlook for Retatrutide in MASH/NASH

Phase 3 trials will test histology endpoints like fibrosis regression.[1] Obesity approvals could enable liver labeling via substudies.[1] Expect data by 2027, potentially transforming MASH care.

Key watches: Biopsy-proven NASH regression, long-term safety >2 years, diverse populations.[1]

Conclusion: Retatrutide's Promise for Liver Fat Reduction in NASH

Retatrutide liver fat reduction NASH phase 2 results position it as a leader for MASLD/NASH.[1][2] Up to 86% fat loss, 93% normalization, and 25% weight reduction signal breakthrough potential.[3] The data highlight its role in early intervention, with glucagon agonism driving superior liver-specific outcomes.[4]

Safety and efficacy support rapid advancement.[1]

Key Takeaways from Phase 2 Results

Dose-dependent, sustained liver fat reductions >80% at high doses.[3]
High steatosis resolution rates (85-93%).[1][3]
Broad metabolic wins without liver safety issues.[1]
Superior to placebo and prior agents.[2][3]

Expert Commentary on Glucagon's Role

Adding glucagon to GLP-1/GIP boosts NAFLD efficacy.[4] It promotes direct liver fat oxidation. "This bottom-up therapy wipes out fat early," per conference insights.[3]

What to Watch in Upcoming Data

Phase 3 topline results, histology endpoints, head-to-heads.[1] Approval could transform NASH care by 2027+.[1] Patients should await FDA greenlight; consult doctors for current options like lifestyle or approved GLP-1s. For patient eligibility details, review our MASLD treatment eligibility guide.

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