Retatrutide: A Triple GLP-1/GIP/Glucagon Agonist for Obesity and Metabolic Disease

This content is provided by Superpower Health for educational and informational purposes only. Retatrutide is currently unavailable through Superpower. Retatrutide is not FDA-approved for any indication; it is an investigational compound currently in Phase 3 clinical trials. Access is limited to clinical trial enrollment. This page is not a substitute for medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

Semaglutide targets one receptor. Tirzepatide targets two. Neither addresses energy expenditure directly. The next generation of obesity pharmacology is testing whether activating a third receptor closes that gap. Retatrutide is the furthest along in that hypothesis, and it is not yet available outside clinical trials.

Here is how retatrutide works, what Phase 2 and emerging Phase 3 data have found, and what the regulatory timeline looks like.

Key Takeaways

• Regulatory Status: Not FDA-approved. As of April 2026, retatrutide is an investigational compound in Phase 3 clinical development under the TRIUMPH program. It is not approved for any indication.
• Research Stage: Phase 3 registrational trials ongoing (TRIUMPH program); Phase 2 obesity and T2D data published in NEJM and Lancet (2023); Phase 2a liver data published in Nature Medicine (2024).
• Availability: Not available through Superpower or by prescription outside clinical trials. Enrollment information is available at ClinicalTrials.gov.
• Compound reference: PubChem CID 163322498. No FDA-approved prescribing information exists; retatrutide is investigational.
• How it works: Simultaneously activates GLP-1, GIP, and glucagon receptors to reduce appetite, improve incretin signaling, and increase energy expenditure.
• What the research shows: In a 2023 Phase 2 RCT published in the New England Journal of Medicine by Jastreboff and colleagues (n=338, 48 weeks), retatrutide at the 12 mg dose produced mean weight loss of 24.2% versus 2.1% for placebo. Individual results varied. Phase 3 registrational trials are ongoing; weight regain after discontinuation, as observed with other agents in this class, has not yet been fully characterized for retatrutide but is anticipated based on the mechanism of action.

What Is Retatrutide?

Retatrutide (development code LY3437943) is a synthetic peptide developed by Eli Lilly that acts as a simultaneous agonist at three receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR). These three receptors regulate distinct but overlapping aspects of metabolic physiology: satiety signaling, incretin-mediated insulin secretion, and hepatic glucose and fat metabolism. The scientific rationale for combining all three is that each receptor contributes a different part of the metabolic response, and activating them together produces effects that no single-receptor or dual-receptor agonist fully replicates.

Retatrutide is the furthest advanced triple agonist in the obesity drug pipeline. A 2022 preclinical pharmacology paper in Cell Metabolism by Coskun and colleagues from Eli Lilly described LY3437943's receptor binding profile, noting balanced GCGR and GLP-1R activity with more prominent GIPR activity, and documented that in obese animal models, weight reduction was augmented by glucagon receptor-mediated increases in energy expenditure layered on top of GIPR- and GLP-1R-driven calorie intake reduction. The same paper reported persistent weight loss lasting 43 days post-dose in animal models, suggesting a pharmacodynamically durable profile. These findings supported the program's advancement to human trials.

How Retatrutide Works: The Triple-Receptor Mechanism

GLP-1 receptor agonism: appetite and satiety

The GLP-1 receptor is the mechanism underpinning semaglutide's efficacy and the most extensively characterized component of the incretin system. Daniel Drucker's foundational review on GLP-1 physiology and the pharmacotherapy of obesity, published in Molecular Metabolism, established that GLP-1 receptor agonism reduces food intake and body weight through highly conserved mechanisms in both animals and humans, across adolescents and adults, with a well-defined safety database built across years of clinical use in type 2 diabetes. In retatrutide, GLP-1R agonism provides the core appetite-suppression and slowed gastric-emptying effects familiar from semaglutide. This component slows meal absorption, reduces hunger signaling in the hypothalamus, and contributes to the caloric deficit that drives weight loss. A 2024 narrative review of the triple-agonist story by Abdul-Rahman and colleagues in the European Journal of Pharmacology described GLP-1R engagement as the foundational anchor of retatrutide's mechanism, on which the GIP and glucagon components build additive and complementary effects.

GIP receptor agonism: incretin synergy and tolerability

The glucose-dependent insulinotropic polypeptide receptor (GIPR) is the second receptor targeted by retatrutide, and it is the same receptor that tirzepatide adds to GLP-1 agonism. GIP enhances glucose-stimulated insulin secretion in a glucose-dependent manner, meaning it amplifies insulin release when blood sugar is elevated but has minimal effect at normal glucose levels. This mechanism improves glycemic control without proportionally increasing hypoglycemia risk. In the incretin pharmacology context, there is accumulating evidence that GIPR co-agonism also improves the gastrointestinal tolerability of GLP-1 receptor activation: the nausea and vomiting associated with pure GLP-1 agonists are attenuated when GIPR engagement is added simultaneously, an observation that may explain why tirzepatide's tolerability profile compares favorably to semaglutide despite producing greater weight loss. A 2025 mechanistic review by Jiang and colleagues in Diabetes, Obesity and Metabolism examined why GLP-1 combined with GIP and glucagon agonism exceeds the weight-loss efficacy of GLP-1 alone, concluding that each receptor contributes a mechanistically distinct pathway. GIP agonism contributes incretin synergy and an adipose-tissue effect that facilitates fat utilization during caloric restriction.

Glucagon receptor agonism: the differentiating mechanism

The glucagon receptor component is retatrutide's defining pharmacological feature versus tirzepatide. Glucagon is classically understood as a counter-regulatory hormone that raises blood glucose by stimulating hepatic glucose production, which is why its inclusion in a diabetes and obesity drug might seem counterintuitive at first. The critical insight is that glucagon receptor agonism, when administered at doses balanced against the GLP-1 and GIP components, does not produce net hyperglycemia because the glucose-lowering effects of GLP-1R and GIPR engagement offset any glucagon-driven glucose elevation. What remains is the thermogenic and lipolytic effect of glucagon receptor activation: increased hepatic fat oxidation, elevated energy expenditure, and direct promotion of fatty acid breakdown in the liver. Philip Newsome and Phil Ambery, in their 2023 review of incretins and the liver published in the Journal of Hepatology, contextualized this mechanism, noting that dual and triple gut hormone agonists have shown improvements in weight, insulin resistance, and liver parameters, and that the glucagon component in particular acts upstream on hepatic fat metabolism in ways that pure GLP-1 agents do not replicate. This hepatic-fat effect is the mechanism behind retatrutide's striking liver data, discussed in the evidence section below.

Phase 2 Clinical Evidence

Obesity: the NEJM Phase 2 trial

The landmark efficacy reference for retatrutide in obesity is the 2023 Phase 2 RCT by Jastreboff and colleagues published in the New England Journal of Medicine (n=338 adults with obesity or overweight and at least one weight-related comorbidity, 48 weeks, multiple dose levels versus placebo). At the 12 mg dose (the highest evaluated), participants achieved least-squares mean weight loss of 24.2% versus 2.1% in the placebo group. At lower doses, weight loss was clearly dose-dependent: approximately 8.7% at 1 mg, 17.1% at 4 mg, and 22.8% at 8 mg. The study noted that 100%, 93%, and 83% of the 12 mg group achieved weight reductions of at least 5%, 10%, and 15%, respectively. Adverse events were predominantly gastrointestinal: nausea, vomiting, and diarrhea, dose-related, and mostly mild to moderate in severity. The investigators noted that gastrointestinal events were partially mitigated by using a lower starting dose (2 mg versus 4 mg). Weight regain after discontinuation was not fully characterized in this Phase 2 trial; based on the mechanism of action and the class-wide pattern observed with GLP-1 receptor agonists, weight regain after stopping retatrutide is anticipated and is being evaluated in Phase 3 extension studies. Individual results varied across dose groups and participants. A contemporaneous editorial by Doggrell in Expert Opinion on Investigational Drugs in 2023 framed these Phase 2 results as a potential step forward in diabetes and obesity treatment while cautioning that longer-term Phase 3 data would be needed to establish durability and safety.

Type 2 diabetes: the Lancet Phase 2 trial

A separate Phase 2 trial specifically in people with type 2 diabetes was reported by Rosenstock, Frias, Jastreboff and colleagues in the Lancet in 2023 (n=281, placebo- and dulaglutide 1.5 mg-controlled, 36 weeks). At the 12 mg dose, retatrutide produced mean HbA1c reductions of 2.02 percentage points compared to 1.41 percentage points for dulaglutide (p=0.0002), with mean bodyweight reductions of 16.94% versus 2.02% for dulaglutide (p less than 0.0001). Across the 8 mg dose groups (slow and fast escalation), bodyweight reductions ranged from 16.34% to 16.81%. These results substantially exceeded those produced by dulaglutide, an established GLP-1 receptor agonist. The study pre-dated the TRIUMPH registrational program and was not designed or powered to draw conclusions about cardiovascular outcomes; the cardiovascular evidence base for retatrutide remains preliminary. A 2024 systematic review by Salmen and colleagues in Pharmaceuticals noted that further, longer-term follow-up studies are necessary to verify long-term cardiovascular protection for triple agonists, and that the current evidence base is insufficient to draw firm conclusions independent of metabolic improvements.

Early-phase proof of concept

The Phase 1b proof-of-concept trial for LY3437943 (retatrutide) in T2D was reported by Urva and colleagues in the Lancet in 2022 (n=72, 12 weeks, multiple-ascending-dose). The trial established that the compound had an acceptable pharmacokinetic and safety profile, with dose-dependent reductions in mean daily plasma glucose reaching approximately 2.8 to 3.1 mmol/L at the highest doses, HbA1c reductions of approximately 1.2 to 1.6 percentage points, and weight loss reaching up to 8.96 kg in the highest dose cohort. Gastrointestinal adverse events were the most common finding, consistent with the GLP-1 class profile. This trial provided the clinical proof of concept that supported the Phase 2 program.

Hepatic Fat and MASLD Evidence

One of the most clinically significant data sets for retatrutide comes from a Phase 2a trial in metabolic dysfunction-associated steatotic liver disease (MASLD, previously termed NAFLD/NASH). Published by Sanyal and colleagues in Nature Medicine in 2024 (n=98, 24 weeks, randomized placebo-controlled), retatrutide at the 8 mg and 12 mg doses produced relative reductions in hepatic lipid content of 81.4% and 82.4%, respectively, compared to a 0.3% change in the placebo group (p less than 0.001 for all active doses versus placebo). The 1 mg dose produced a 42.9% reduction and the 4 mg dose 57.0%, demonstrating a clear dose-response pattern. By week 24, achievement of normal liver fat levels (defined as less than 5% hepatic lipid content) ranged from 27% to 86% across dose groups, compared to 0% in placebo. These reductions correlated strongly with bodyweight loss and improvements in metabolic parameters including insulin resistance and liver enzymes. A 2025 review of triple-agonism therapies by Goldney and colleagues in Current Cardiovascular Risk Reports highlighted retatrutide's 82% hepatic steatosis reduction as one of the most striking findings in the emerging triple-agonist literature. The hepatic effect is mechanistically explained by the glucagon receptor component's promotion of hepatic fat oxidation, as described in the mechanism section above.

How Retatrutide Compares to Tirzepatide and Semaglutide

Retatrutide, tirzepatide, and semaglutide belong to the same pharmacological family but differ in their receptor targets. These comparisons are for scientific context only. Retatrutide is an investigational compound that has not completed the FDA approval process. Tirzepatide and semaglutide are FDA-approved medications with fundamentally different regulatory statuses and established evidence bases. Cross-trial comparisons are unreliable due to differences in study design, patient populations, follow-up duration, and endpoints.

Versus semaglutide (single GLP-1 agonist)

Semaglutide 2.4 mg once weekly was evaluated in the STEP 1 trial, reported by Wilding and colleagues in the New England Journal of Medicine in 2021 (n=1,961, 68 weeks), where participants with obesity achieved mean weight loss of 14.9% versus 2.4% for placebo. Semaglutide targets only the GLP-1 receptor and does not engage GIPR or GCGR. A narrative review by Alfaris and colleagues published in EClinicalMedicine in 2024 mapped the progression from semaglutide (single agonist) through tirzepatide (dual agonist) to retatrutide (triple agonist), finding a consistent pattern of increasing weight loss efficacy with each additional receptor target. The absence of direct glucagon receptor engagement is the primary mechanistic reason semaglutide does not produce the hepatic fat reductions observed with retatrutide; semaglutide's liver effects, while meaningful, are largely mediated indirectly through weight loss and improved insulin sensitivity rather than direct GCGR-driven fat oxidation.

Versus tirzepatide (dual GIP/GLP-1 agonist)

Tirzepatide 15 mg once weekly was evaluated in the SURMOUNT-1 trial, reported by Jastreboff and colleagues in the New England Journal of Medicine in 2022 (n approximately 2,539, 72 weeks), where participants achieved mean weight loss of 20.9% versus 3.1% for placebo at the highest dose. A 2024 network meta-analysis of seven GLP-1 receptor agonists and polyagonists by Xie and colleagues published in Metabolism (27 RCTs, 15,584 patients) found retatrutide 12 mg produced approximately 22.10% mean weight loss compared to approximately 16.53% for tirzepatide 15 mg, ranking retatrutide highest in the weight-loss hierarchy. A 2025 systematic review and network meta-analysis by Yan and colleagues in Acta Diabetologica reached a complementary conclusion: retatrutide achieved the greatest weight reduction among the agents evaluated, while tirzepatide was most effective at lowering fasting blood glucose and HbA1c, suggesting the two compounds may have different optimal profiles depending on whether weight reduction or glycemic control is the primary goal. Cross-trial comparisons must be interpreted with attention to specific doses, trial durations, populations, and endpoints.

The TRIUMPH Phase 3 Program

The TRIUMPH registrational trial program is the Phase 3 evidence-generation effort designed to support an eventual FDA approval application for retatrutide. The program's rationale and design were published by Giblin and colleagues in Diabetes, Obesity and Metabolism in 2026. TRIUMPH consists of four multicenter, randomized, double-blind trials enrolling more than 5,800 participants across four populations:

• TRIUMPH-1 and TRIUMPH-2: Weight management basket trials with nested sub-studies evaluating obstructive sleep apnea (OSA) outcomes (apnea-hypopnea index) and knee osteoarthritis pain (WOMAC pain subscale) in participants who also have these comorbidities alongside obesity.
• TRIUMPH-3: Weight management trial in participants with established cardiovascular disease, designed to evaluate retatrutide's effects on cardiovascular outcomes in a higher-risk population.
• TRIUMPH-4: A standalone knee osteoarthritis trial examining whether retatrutide's weight-reducing and potentially direct anti-inflammatory effects improve OA pain independent of the general obesity trials.

The primary weight-management endpoint across TRIUMPH-1, 2, and 3 is percent change in body weight from baseline. All trials use once-weekly subcutaneous injection. The basket design permits independent statistical analysis of each nested endpoint while controlling the Type I error rate. As of April 2026, TRIUMPH trial results are not yet published. Regulatory approval of retatrutide for obesity or any other indication is contingent on these readouts and FDA review, which will take additional time after the trials conclude. The regulatory timeline suggests potential FDA review in 2026 to 2027, depending on TRIUMPH readout timing and NDA submission.

Side Effects and Safety Profile

The safety profile of retatrutide observed in Phase 2 studies is consistent with the GLP-1 receptor agonist class and is predominantly characterized by gastrointestinal adverse events.

Common (reported in Phase 2 clinical trials):

• Nausea (the most frequently reported adverse event across dose groups; dose-related and typically more prominent during dose escalation)
• Vomiting (dose-related; partially mitigated by starting at the 2 mg dose rather than the 4 mg dose, as noted by Jastreboff and colleagues in the NEJM Phase 2 report)
• Diarrhea (reported across active dose groups; typically mild to moderate)
• Decreased appetite (a pharmacodynamic effect of GLP-1R agonism that contributes to the caloric deficit driving weight loss)

Less common but reported or theoretically relevant based on mechanism:

• Constipation (reported with other GLP-1 receptor agonists; observed across the class)
• Injection site reactions (expected with subcutaneous injection; generally mild)
• Hypoglycemia (theoretically lower risk than sulfonylureas because GLP-1R and GIPR effects on insulin secretion are glucose-dependent; however, risk may increase when retatrutide is used alongside other glucose-lowering agents, a consideration that applies primarily in the context of concurrent diabetes medications)

A 2025 systematic review and meta-analysis of retatrutide RCTs by Abouelmagd and colleagues in the Proceedings of Baylor University Medical Center (three RCTs, 878 patients) found no significant difference in the overall incidence of adverse events between retatrutide and placebo groups (relative risk 1.11; p=0.24), although this aggregate finding does not capture the dose-related increase in gastrointestinal symptoms that is consistently observed at higher doses within the active treatment arms. A 2025 review by Katsi and colleagues in Biomolecules characterized the overall safety profile as favorable relative to the magnitude of metabolic benefit, while noting that the full long-term safety profile will be established through the TRIUMPH Phase 3 program. Because retatrutide is an investigational compound, its complete safety profile, including rare adverse events, long-term cardiovascular safety, and effects in special populations, has not yet been established through adequate, well-controlled clinical trials.

Who Would Be a Potential Candidate Based on Clinical Trial Criteria

Because retatrutide is not FDA-approved and is not available by prescription, there is no current clinical candidacy framework outside clinical trial participation. The Phase 2 and Phase 3 trials have enrolled populations with:

• Obesity (body mass index of 30 kg/m² or higher) or overweight with at least one weight-related comorbidity
• Type 2 diabetes with inadequate glycemic control on existing therapy
• MASLD (metabolic dysfunction-associated steatotic liver disease, confirmed by imaging)
• Obstructive sleep apnea as a nested comorbidity in the TRIUMPH basket design
• Established cardiovascular disease as a specific sub-population in TRIUMPH-3

Enrollment criteria and eligibility requirements vary by individual trial. Anyone interested in participating in a retatrutide clinical trial should consult the ClinicalTrials.gov trial registry for current enrollment status and eligibility criteria.

Who Should Not Use Retatrutide

As an investigational compound, formal contraindications for retatrutide have not been established. The following populations were excluded from Phase 2 trials or face elevated theoretical risk based on the GLP-1 receptor agonist class profile and the glucagon receptor component's effects:

• Personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2): this exclusion applies to all GLP-1 receptor agonists based on preclinical rodent carcinogenicity data; human MTC risk has not been established for the class, but the exclusion is maintained in trial protocols based on the labeling for approved GLP-1 agents.
• Pancreatitis history: acute and chronic pancreatitis have been reported with GLP-1 receptor agonists; participants with a history of clinically significant pancreatitis were excluded from Phase 2 trials.
• Severe renal impairment: the Phase 2 trials excluded participants with severely impaired renal function; pharmacokinetic and safety data in this population are limited.
• Pregnancy and breastfeeding: retatrutide has not been studied in pregnant or breastfeeding individuals; weight loss during pregnancy is generally not recommended, and the safety of this compound in these populations is unknown.
• Hypersensitivity to any component of the formulation.

This is not an exhaustive list. A licensed provider will evaluate individual risk factors before any clinical decision involving this compound.

Is Retatrutide Legal?

As of April 2026, retatrutide is not FDA-approved for any indication. It is an investigational new drug in Phase 3 clinical development under the TRIUMPH program. Retatrutide is not available by prescription, through compounding pharmacies, or through any commercial channel. Access is restricted to participants enrolled in authorized clinical trials. It is not available over the counter in any form.

Retatrutide is not classified under the FDA's compounding bulk drug substance category system because it is an investigational compound under active IND (Investigational New Drug) status with Eli Lilly and is not available for compounding. Any online vendor claiming to sell retatrutide is selling an unregulated product of unknown identity, purity, and safety. The FDA has not authorized compounding or sale of retatrutide outside the controlled clinical trial setting. Compound reference data: PubChem CID 163322498.

Biomarkers Relevant to Metabolic Health Monitoring

Retatrutide is not currently available outside clinical trials, and there is no prescribing context in which to frame a monitoring panel. However, understanding the biomarkers that track the metabolic outcomes retatrutide is designed to address is clinically relevant regardless of which therapy is ultimately used. The markers below directly reflect the mechanisms and endpoints that define retatrutide's therapeutic rationale.

• Hemoglobin A1c (HbA1c): The primary marker of glycemic control over the preceding two to three months. HbA1c is the endpoint in all retatrutide T2D trials and directly tracks the GLP-1R and GIPR components' effect on insulin secretion and glucose regulation. Baseline HbA1c establishes glycemic status and makes any future response to therapy interpretable.
• Fasting glucose: Reflects hepatic glucose output and fasting insulin sensitivity. Retatrutide's glucagon receptor component directly modulates hepatic glucose production; fasting glucose tracks this mechanism. In the Phase 1b trial, placebo-adjusted mean daily glucose decreased by approximately 2.8 to 3.1 mmol/L at the highest doses.
• Fasting insulin: Elevated fasting insulin is the most sensitive early marker of insulin resistance and is often elevated years before HbA1c begins to rise. Tracking insulin alongside glucose provides a more complete picture of metabolic function than either marker alone.
• Body weight and waist circumference: The primary efficacy endpoints in the TRIUMPH program. Waist circumference specifically reflects visceral adiposity, the metabolically active fat depot that drives insulin resistance, hepatic steatosis, and cardiovascular risk. The Phase 2 network meta-analysis by Xie and colleagues reported retatrutide 12 mg produced approximately 17.00 cm reduction in waist circumference versus approximately 13.23 cm for tirzepatide 15 mg.
• Liver enzymes (ALT and AST): Alanine aminotransferase and aspartate aminotransferase are the primary serum markers of hepatocellular injury and are elevated in MASLD. In the Sanyal Phase 2a trial, liver enzyme improvements correlated with hepatic fat reduction. ALT and AST are practical proxy markers for hepatic fat changes when imaging is not available.
• Lipid panel (triglycerides, LDL, HDL): The Phase 2 obesity trial showed improvements in lipid parameters alongside weight loss. Triglycerides are particularly sensitive to both hepatic fat accumulation and the direct lipolytic effect of glucagon receptor activation. The Goldney et al. review noted retatrutide's improvements across blood pressure and lipid parameters as part of its broader cardiometabolic profile.
• Blood pressure: The Abouelmagd meta-analysis reported mean systolic blood pressure reductions of 9.88 mmHg and diastolic reductions of 3.88 mmHg across retatrutide-treated participants. Blood pressure monitoring tracks one of the most clinically meaningful cardiometabolic benefits associated with substantial weight loss.

The rationale for understanding these markers now, before any therapy begins, is consistent with Superpower's approach to preventive health: objective biomarker data should precede any clinical decision. Whether or not retatrutide eventually becomes available, knowing where your metabolic markers stand provides a meaningful baseline against which any intervention can be evaluated.

IMPORTANT SAFETY INFORMATION

Retatrutide (LY3437943) is NOT FDA-approved for any indication. It is an investigational new drug under active IND status with Eli Lilly and Company, currently in the Phase 3 TRIUMPH clinical program. Retatrutide is not classified as a Category 2 bulk drug substance under FDA Section 503A because it is an investigational compound under active IND review and was never available through compounding pharmacies; it is not eligible for compounding under 503A or 503B pathways. It is not commercially available, not available by prescription, and not available through any licensed pharmacy. Access is restricted to participants enrolled in authorized, IRB-approved clinical trials. Superpower is a technology platform; Superpower does not prescribe, sell, compound, or facilitate access to retatrutide.

Do not use retatrutide if you: have a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2); have clinically significant pancreatitis history; have severe renal or hepatic impairment (not studied in Phase 2); are pregnant, may become pregnant, or are breastfeeding (safety not established, weight loss not recommended in pregnancy); are a minor (pediatric safety not established); have a history of diabetic retinopathy that could worsen with rapid glucose change; or have known hypersensitivity to retatrutide or any formulation component.

Warnings: The GLP-1 receptor agonist class carries a class-associated preclinical finding of thyroid C-cell tumors in rodents at clinically relevant exposures; whether this finding translates to humans has not been established, but the signal is reflected in approved GLP-1 agonist labeling. Additional class considerations relevant to retatrutide's GLP-1 receptor agonism include acute pancreatitis, acute gallbladder disease, hypoglycemia risk (particularly with concomitant insulin or sulfonylureas), gastroparesis exacerbation, and acute kidney injury secondary to severe GI symptoms. The glucagon receptor agonism component may theoretically affect hepatic glucose handling; this has not been observed as net hyperglycemia in Phase 2 trials but requires Phase 3 confirmation. The triple-agonist combination has not been available long enough to characterize long-term cardiovascular safety.

Common adverse events observed in Phase 2 trials: nausea, vomiting, diarrhea, decreased appetite, constipation, injection site reactions. Most gastrointestinal events were dose-related, mild to moderate in severity, and predominantly occurred during dose escalation; a lower starting dose (2 mg) partially mitigated these events.

Long-term data limitations: The complete safety profile of retatrutide — including rare serious adverse events, long-term cardiovascular safety, effects in special populations, drug interactions, and weight regain dynamics after discontinuation — has not been established through adequate and well-controlled clinical trials. Phase 3 TRIUMPH trial data will provide the primary long-term evidence base. This is not a complete list of risks.

Compound reference: PubChem CID 163322498. For current trial eligibility and safety information, consult the authorized trial protocol at ClinicalTrials.gov. Upon FDA approval (if granted), DailyMed will carry the authoritative prescribing information.

Additional Questions

What side effects has retatrutide shown in trials?

The most common adverse events in Phase 2 trials were gastrointestinal: nausea, vomiting, and diarrhea, consistent with the GLP-1 receptor agonist class. These events were dose-related and mostly mild to moderate in severity. They were partially mitigated by starting at a lower dose (2 mg) and escalating gradually. The complete long-term safety profile of retatrutide has not been established; Phase 3 trials are the primary data source for this information.

How does retatrutide affect the liver?

In a Phase 2a RCT in MASLD published in Nature Medicine in 2024 by Sanyal and colleagues (n=98, 24 weeks), retatrutide at 8 mg and 12 mg produced 81.4% and 82.4% relative reductions in hepatic lipid content versus 0.3% for placebo. These results were attributed in part to the glucagon receptor component's direct effect on hepatic fat oxidation, layered on top of the metabolic improvements driven by weight loss. Liver enzyme changes correlated with hepatic fat reduction in these data.

When will retatrutide be available?

A regulatory timeline cannot be confirmed. The TRIUMPH Phase 3 program is ongoing as of April 2026. If TRIUMPH data support an NDA submission and the FDA reviews and approves the application, availability could follow in 2026 to 2027, though this estimate is contingent on trial readout timing, data quality, and the FDA's review process. Regulatory outcomes are not predictable from outside the process.