Retatrutide Latest Research: New Indications, Trials & What’s Coming

Introduction

Retatrutide is the most-watched investigational obesity drug of 2026. Eli Lilly’s TRIUMPH Phase 3 program reads out across 2026 and 2027 with expected FDA submission for the obesity indication in late 2025 or early 2026. The drug already holds the record for largest mean weight loss in any GLP-1-class Phase 2 study, with 24.2 percent at 48 weeks reported by Jastreboff and colleagues in 2023 in the New England Journal of Medicine.

The research expansion beyond obesity is where the story gets interesting. Retatrutide is in active trials for type 2 diabetes, non-alcoholic steatohepatitis (now called metabolic dysfunction-associated steatohepatitis or MASH), obstructive sleep apnea, heart failure with preserved ejection fraction, and cardiovascular outcomes. The triple agonist mechanism, GLP-1 plus GIP plus glucagon, gives retatrutide a metabolic reach that single and dual agonists don’t have.

This article covers the active TRIUMPH program, completed and ongoing exploratory studies, and the expected indication expansions over the next 5 years. TrimRx provides personalized treatment plans for currently approved GLP-1 medications while retatrutide moves through regulatory review.

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What Is the TRIUMPH Phase 3 Program?

TRIUMPH is Eli Lilly’s umbrella name for the retatrutide Phase 3 development program. Five main trials are running or have completed enrollment, targeting different patient populations and indications.

Quick Answer: TRIUMPH-1 (obesity), TRIUMPH-2 (T2D), TRIUMPH-3 (cardiovascular outcomes), TRIUMPH-4 (MASH), and TRIUMPH-OSA are the five major Phase 3 programs

TRIUMPH-1 enrolled approximately 2,400 adults with obesity (BMI 30 or higher, or BMI 27 with comorbidity) without diabetes. Primary endpoint is percent change in body weight at 72 weeks. This is the registration trial for the obesity indication.

TRIUMPH-2 enrolled adults with type 2 diabetes and obesity, testing weight loss and glycemic outcomes at 72 weeks. TRIUMPH-3 is the cardiovascular outcomes trial with approximately 15,000 participants and a target follow-up of 5 years. TRIUMPH-4 is the MASH liver disease trial. TRIUMPH-OSA tests retatrutide for obstructive sleep apnea following the SURMOUNT-OSA tirzepatide template.

Topline data from TRIUMPH-1 and TRIUMPH-2 is expected in 2026. TRIUMPH-3 is a longer-duration trial reading out in 2027 or 2028.

What Did Phase 2 Obesity Data Show?

The Phase 2 trial (Jastreboff et al. 2023 NEJM) enrolled 338 adults with obesity (mean BMI 37) without diabetes. Participants were randomized to placebo or retatrutide at 1, 4, 8, or 12 mg weekly for 48 weeks.

The 12 mg group lost a mean of 24.2 percent of baseline body weight. The 8 mg group lost 22.8 percent. Both numbers exceed the 14.9 percent from STEP 1 semaglutide (Wilding et al. 2021 NEJM) and the 20.9 percent from SURMOUNT-1 tirzepatide (Jastreboff et al. 2022 NEJM).

The shape of the weight loss curve mattered. Unlike semaglutide and tirzepatide which plateau between week 60 and 72, retatrutide’s curve was still trending down at week 48 in the high-dose groups. Phase 3 is testing whether longer treatment continues to drive loss or whether plateau eventually arrives.

Body composition analysis showed fat mass accounted for the majority of weight lost, with lean mass loss representing about 22 to 25 percent of total weight loss, similar to dietary weight loss and to other GLP-1s.

What Does Phase 2 Diabetes Data Show?

Rosenstock and colleagues published Phase 2 retatrutide results in adults with type 2 diabetes in 2023 in The Lancet. The trial randomized 281 adults with inadequately controlled T2D to placebo, dulaglutide 1.5 mg, or retatrutide at 0.5, 4, 8, or 12 mg.

The 12 mg retatrutide group reduced A1C by 2.16 percent absolute, compared to 1.41 percent for dulaglutide and 0.01 percent for placebo. Body weight reduced by 16.9 percent on retatrutide 12 mg, compared to 2.0 percent on dulaglutide.

The glycemic efficacy plus weight loss combination positions retatrutide as a potential first-line therapy for T2D with obesity. Phase 3 TRIUMPH-2 is testing this at scale.

What Are the MASH and Liver Disease Results?

MASH (metabolic dysfunction-associated steatohepatitis), formerly NASH, is one of the most exciting expansion targets for retatrutide. Sanyal and colleagues published an exploratory analysis in 2024 in Nature Medicine using MRI-proton density fat fraction from the Phase 2 obesity trial.

At baseline, participants had mean liver fat content of 15.9 percent. At week 48, the 8 mg and 12 mg retatrutide groups showed reductions of 81.4 and 82.4 percent respectively. About 90 percent of participants in high-dose groups achieved liver fat content below 5 percent at week 48, which is the threshold for non-steatotic liver.

These results compare favorably to phase 2 semaglutide NASH data (Newsome 2021 NEJM) and to tirzepatide phase 2 (SYNERGY-NASH). TRIUMPH-4 is the dedicated Phase 3 MASH trial testing biopsy-confirmed fibrosis regression and NASH resolution.

The MASH market is growing rapidly. Resmetirom (Rezdiffra®) became the first FDA-approved MASH drug in 2024 based on MAESTRO-NASH (NEJM 2024). Retatrutide could become the first weight-loss-active MASH treatment if TRIUMPH-4 reads out positive.

What About Cardiovascular Outcomes?

TRIUMPH-3 is the major cardiovascular outcomes trial. The design closely mirrors SELECT (Lincoff et al. 2023 NEJM) which showed 20 percent MACE reduction on semaglutide in adults with established cardiovascular disease and obesity.

TRIUMPH-3 enrolled approximately 15,000 adults with established atherosclerotic cardiovascular disease and BMI 27 or higher. Primary endpoint is time to first MACE (cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke). Target follow-up is 5 years.

Topline data is expected in 2027. Given retatrutide’s larger weight loss magnitude and metabolic effects, expectations are for MACE reduction of 25 to 30 percent, exceeding semaglutide’s 20 percent benefit. That would be a substantial clinical and commercial inflection point.

How Does Retatrutide Affect Obstructive Sleep Apnea?

OSA is heavily driven by obesity. Tirzepatide became FDA-approved for OSA in December 2024 based on SURMOUNT-OSA, which showed 27 to 30 events per hour reduction in apnea-hypopnea index with weight loss.

TRIUMPH-OSA is testing retatrutide for OSA following the same template. Given retatrutide’s larger weight loss, expectations are for larger AHI reductions. Phase 2 retatrutide trials reported subset analyses suggesting significant OSA-symptom improvement, though formal AHI measurements come from TRIUMPH-OSA.

OSA approval would expand retatrutide’s reach into a market where coverage is often better than weight management alone, since OSA is a treatment indication that insurance can recognize.

Key Takeaway: Phase 2 diabetes results (Rosenstock et al. 2023 Lancet) showed A1C reduction of 2.16 percent on 12 mg with weight loss of 16.9 percent at 36 weeks

What About Heart Failure?

The STEP-HFpEF program established semaglutide for heart failure with preserved ejection fraction in adults with obesity. Retatrutide’s larger weight loss and unique glucagon effects on cardiac energetics raise interest in a similar indication.

A Phase 2 trial of retatrutide in HFpEF is in planning stages. Phase 3 development could follow if Phase 2 data supports it.

The glucagon receptor agonism is the wildcard. Glucagon increases resting energy expenditure, which is helpful for weight loss but theoretically could increase cardiac workload in fragile heart failure patients. The Phase 2 data will inform whether HFpEF is a fit or a contraindication.

Are There Any Retatrutide Trials in Addiction or Metabolic Syndrome?

Exploratory work in alcohol use disorder is underway following anecdotal reports of reduced alcohol consumption on GLP-1 drugs. Retatrutide’s mechanism makes it a strong candidate for this research direction.

Metabolic syndrome trials testing retatrutide for the cluster of insulin resistance, hypertension, dyslipidemia, and central obesity are in early planning. Polycystic ovary syndrome research is also being considered.

These are early-stage explorations. Approval for these uses is unlikely before 2030.

What’s the Timeline for FDA Approval?

Eli Lilly has stated late 2025 FDA submission for the obesity indication. Standard FDA review timeline is 10 to 12 months, putting potential obesity approval in late 2026 or early 2027.

T2D approval would follow 6 to 12 months after obesity. MASH and OSA indications would be Phase 3 reads in 2027 and submissions in 2028. Cardiovascular outcomes data and indication expansion to follow.

Real-world availability for the obesity indication could come within 12 months of approval, mirroring the Zepbound® launch trajectory.

What Does the Competitive Landscape Look Like?

Retatrutide is the lead triple agonist but not alone. Boehringer Ingelheim and Zealand Pharma’s survodutide is a GLP-1 plus glucagon dual agonist in Phase 3 for obesity and MASH. Pfizer’s danuglipron, an oral GLP-1, was discontinued in 2025. Novo Nordisk’s amycretin (combined GLP-1 plus amylin) and CagriSema (semaglutide plus cagrilintide) are direct competitors.

The next 3 years will see a wave of new mechanism approvals. Retatrutide’s edge is the largest weight loss in any Phase 2 program to date.

Bottom line: Cardiovascular outcomes data is expected from TRIUMPH-3 in 2027, following the SELECT semaglutide template for GLP-1 cardiovascular benefit

FAQ

When Will Retatrutide Be Available to Patients?

Expected late 2026 or 2027 for the obesity indication. Diabetes approval could follow 6 to 12 months later.

What’s the Difference Between Retatrutide and Tirzepatide?

Retatrutide adds glucagon receptor agonism on top of tirzepatide’s GLP-1 plus GIP profile. The third receptor drives extra weight loss and metabolic effects.

Will Retatrutide Be More Expensive Than Tirzepatide?

Likely launch pricing similar to Zepbound, around $1,000 to $1,400 monthly. Insurance coverage will determine out-of-pocket costs.

Is Retatrutide Better for Diabetes or Obesity?

Both. Phase 2 showed exceptional results in obesity (24.2 percent loss) and in T2D (2.16 percent A1C reduction with 16.9 percent weight loss).

What About Retatrutide and Kidney Disease?

The FLOW trial template for semaglutide suggests strong kidney benefit. Retatrutide kidney outcomes trials are in planning.

Can Retatrutide Treat Fatty Liver Disease?

Phase 2 data showed 80 percent plus reduction in liver fat content. TRIUMPH-4 is the dedicated Phase 3 MASH trial reading out in 2027.

How Long Will Treatment Need to Continue?

GLP-1-class drugs are likely chronic medications. Stopping leads to weight regain in most patients. Retatrutide is expected to follow this pattern.

Disclaimer: This content is for informational purposes only and does not constitute medical advice. It is not intended to diagnose, treat, cure, or prevent any disease or condition. Individual results may vary. Always consult a qualified healthcare professional before starting any weight loss program or medication.