Retatrutide — Triple Agonist GLP-1/GIP/Glucagon Profile
Eli Lilly’s unimolecular triple agonist and the deepest-weight-loss obesity candidate in late-stage development. Pivotal TRIUMPH-1 Phase 3 readout (May 21, 2026): 28.3% mean weight loss at 80 weeks on 12 mg, 30.3% at 104 weeks in the BMI ≥35 extension. TRIUMPH-2 (T2D) and TRIUMPH-3 (established CVD) readouts expected later in 2026.
Update History ▾
May 25, 2026: Re-checked Lilly's TRIUMPH-1 topline and trial-registry status; aligned visible freshness, meta dateModified, schema, and internal routing to the retatrutide hub. Regulatory status unchanged: no approval and no NDA filed.
May 23, 2026: Integrated TRIUMPH-1 pivotal obesity Phase 3 topline (May 21, 2026) — 28.3% at 80 weeks on 12 mg, 30.3% at 104 weeks in the BMI ≥35 extension; 45.3% ≥30% responder rate, 65.3% <BMI 30; dose-by-dose AE-driven discontinuation 4.1/6.9/11.3% vs 4.9% placebo; dysesthesia up to 12.5% on 12 mg, UTI signal noted; full data at the 86th ADA Scientific Sessions, June 2026; broader pipeline status (Phase 3 in obesity, T2D, knee OA, OSA, low back pain, CV/renal outcomes, MASLD/MASH; cumulative TRIUMPH enrolment >5,800). Status now reads as Phase 3 (TRIUMPH program); TRIUMPH-1 reported May 21, 2026; TRIUMPH-4 reported Dec 2025; TRIUMPH-2/-3 readouts expected later in 2026.
May 18, 2026: Added May 2026 research update on retatrutide metabolomics/lipidomics signature (Pearson et al, JCEM, PMID 42135195).
May 7, 2026: Merged Phase 3 safety dataset into the profile — dose-by-dose GI rates, titration-effect analysis, severity stratification, AE timeline, TRIUMPH-4 (Dec 2025) and TRANSCEND-T2D-1 (Mar 2026) topline data, dysesthesia signal, cardiovascular signals, class-wide safety considerations, and four new safety FAQs.
April 22, 2026: Initial publication of dedicated compound profile
Retatrutide (LY-3437943) is Eli Lilly’s investigational once-weekly subcutaneous peptide that activates three receptors in a single molecule: GLP-1, GIP, and glucagon. In the pivotal Phase 3 TRIUMPH-1 trial (topline May 21, 2026, n=2,339, no T2D), retatrutide produced 28.3% mean weight loss at 80 weeks on 12 mg, rising to 30.3% (~85.0 lb) at 104 weeks in a BMI ≥35 extension — the deepest weight loss reported for any obesity candidate to date. The Phase 2 NEJM dataset (~24.2% at 48 weeks) remains the historical anchor. Retatrutide is not yet approved in any territory; TRIUMPH-2 (T2D) and TRIUMPH-3 (established CVD) readouts are expected later in 2026. For the compound-level route through trials, approval status, dosing, Dubai availability, and comparisons, use the retatrutide research hub.
- Architecture: Unimolecular triple agonist — a single engineered peptide activating GLP-1, GIP, and glucagon receptors.
- Sponsor: Eli Lilly — the company’s next-generation flagship beyond tirzepatide (Mounjaro / Zepbound).
- Phase 3 efficacy (TRIUMPH-1, May 21, 2026): 28.3% mean weight loss at 80 weeks on 12 mg; 30.3% at 104 weeks in the BMI ≥35 extension; 45.3% of 12 mg participants reached ≥30% weight loss; 65.3% fell below BMI 30. Phase 2 (NEJM 2023) reported ~24.2% at 48 weeks as historical context.
- Glucagon arm: Increases basal energy expenditure and reduces hepatic fat — mechanisms neither semaglutide nor tirzepatide addresses.
- Phase 3 tolerability (TRIUMPH-1): AE-driven discontinuation 4.1% / 6.9% / 11.3% across 4 / 9 / 12 mg vs 4.9% placebo. Dysesthesia up to 12.5% on 12 mg; UTIs noted. GI events remain the most common AEs.
- Pipeline: Phase 3 in obesity, T2D, knee OA, moderate-severe OSA, chronic low back pain, CV/renal outcomes, and MASLD/MASH. Cumulative TRIUMPH enrolment exceeds 5,800.
- Regulatory status: Not approved in any major territory as of May 28, 2026. TRIUMPH-2 and TRIUMPH-3 readouts expected later in 2026; full TRIUMPH-1 data at the 86th ADA Scientific Sessions, June 2026.
What Is Retatrutide?
Retatrutide (development code LY-3437943) is Eli Lilly’s investigational obesity and type 2 diabetes peptide. Unlike CagriSema, which co-formulates two separate molecules in one injection, retatrutide is a single engineered peptide that binds and activates three different receptors at once:
- GLP-1 receptor — the same target as semaglutide (Ozempic/Wegovy) and the GLP-1 arm of tirzepatide.
- GIP receptor — the same target as tirzepatide’s second arm.
- Glucagon receptor — a third arm not present in any currently approved obesity agent.
Dosing is once-weekly subcutaneous, matching the administration pattern of semaglutide and tirzepatide. Phase 2 tested 1, 4, 8, and 12 mg weekly maintenance doses. If approved, retatrutide would become the first triple agonist on market and Eli Lilly’s next-generation successor to tirzepatide. For regulatory tracking, see Is retatrutide approved?
Mechanism of Action
The retatrutide hypothesis is that the three receptor arms are mechanistically complementary, not redundant. Each arm addresses a different component of body-weight regulation:
- GLP-1 receptor: Central appetite suppression and slowed gastric emptying. This is the same mechanism driving semaglutide’s ~15% weight loss in STEP 1. Well-characterised; gastrointestinal tolerability is the dominant side-effect driver.
- GIP receptor: Adds insulinotropic and satiety effects that appear to blunt GLP-1-driven nausea while reinforcing satiety. This is the same arm that lifted tirzepatide above semaglutide in SURMOUNT-1 (~22.5% vs ~15%).
- Glucagon receptor: Increases basal energy expenditure and reduces hepatic fat. Glucagon also raises blood glucose; retatrutide’s balanced triple agonism is designed so the GLP-1 and GIP arms offset the glycemic impact of the glucagon arm, yielding a net glucose-neutral or glucose-lowering profile.
Compared to the obesity-pipeline alternatives, retatrutide is the only late-stage candidate that targets energy expenditure in addition to appetite. Tirzepatide and semaglutide work almost exclusively through appetite and satiety. Survodutide targets GLP-1 and glucagon (skipping GIP). CagriSema targets GLP-1 and amylin (skipping GIP and glucagon). Retatrutide is the mechanistic superset. For a receptor-by-receptor breakdown of what each arm controls and what trials measure, see the GLP-1, GIP and glucagon mechanism of action page.
Development Stage & TRIUMPH Programme
Retatrutide is in Phase 3 across the TRIUMPH programme, now broadened well beyond the original four lead indications — current Phase 3 work spans obesity, type 2 diabetes, knee osteoarthritis, moderate-severe obstructive sleep apnoea, chronic low back pain, cardiovascular and renal outcomes, and MASLD/MASH. Cumulative TRIUMPH enrolment exceeds 5,800. The pivotal TRIUMPH-1 obesity trial reported topline results on May 21, 2026 — 28.3% mean weight loss at 80 weeks on 12 mg (n=2,339), rising to 30.3% (~85.0 lb) at 104 weeks in a BMI ≥35 extension — joining the earlier TRIUMPH-4 readout (Dec 2025) and the TRANSCEND-T2D-1 readout (Mar 2026). Full TRIUMPH-1 data is scheduled for the 86th ADA Scientific Sessions in June 2026. TRIUMPH-2 (T2D) and TRIUMPH-3 (established CVD) readouts are expected later in 2026, with remaining program work extending into 2027. Eli Lilly has not announced an NDA filing date; regulatory filing will follow the broader Phase 3 sequence.
| Trial | Population | Design | Primary readout |
|---|---|---|---|
| TRIUMPH-1 | Adults with obesity | Placebo-controlled, 80+ weeks | Reported May 2026 — 28.3% at 80 weeks (12 mg) |
| TRIUMPH-2 | Obesity + type 2 diabetes | Placebo-controlled | Expected later 2026 |
| TRIUMPH-3 | Obesity + cardiovascular disease | CVOT design | Expected later 2026 |
| TRIUMPH-4 | Obesity + knee osteoarthritis | Function + weight loss | Reported Dec 2025 — 28.7% weight loss |
Regulatory outlook: TRIUMPH-1 has now reported, so the next gating milestones are the TRIUMPH-2 (T2D) and TRIUMPH-3 (established CVD) readouts expected later in 2026. A cardiovascular outcomes readout from TRIUMPH-3 would strengthen label positioning versus approved competitors. No NDA filed as of May 28, 2026. For a running timeline, see the TRIUMPH trial tracker and the broader obesity drug pipeline timeline.
Manufacturing & commercial outlook: Following the TRIUMPH-1 readout, a Lilly executive said (May 21, 2026) the company hopes to launch the drug around 2027, with an FDA submission expected in 2026. Separately, Lilly’s $4.5 billion additional Indiana manufacturing investment (announced May 6, 2026) expands capacity that supports its obesity and incretin pipeline — the same pipeline that includes retatrutide — rather than naming any single molecule. Sources: CNBC, PR Newswire.
Efficacy Data — TRIUMPH-1 Pivotal Phase 3 (May 2026)
The pivotal Phase 3 dataset is TRIUMPH-1 — a randomised, double-blind, placebo-controlled trial in 2,339 adults with obesity (BMI ≥30) or overweight (BMI ≥27 with comorbidity), excluding T2D. Baseline mean BMI 40.0; baseline weight 112.7 kg. Eli Lilly reported positive topline results on May 21, 2026. All three doses met the primary and key secondary endpoints.
| Dose | Mean weight loss at 80 wks | Absolute weight loss |
|---|---|---|
| Placebo | −2.2% | — |
| 4 mg | −19.0% | 47.2 lb |
| 9 mg | −25.9% | 64.4 lb |
| 12 mg | −28.3% | 70.3 lb |
| 12 mg — BMI ≥35 extension (104 wks) | −30.3% | ~85.0 lb |
On the 12 mg dose, 45.3% of participants achieved ≥30% weight loss and 65.3% reached a BMI under 30 — a magnitude often associated with bariatric surgery. A prespecified blinded extension in BMI ≥35 completers, maintained on 12 mg to the maximum tolerated dose, showed continued reduction to 30.3% mean weight loss at 104 weeks without an apparent plateau. Cardiometabolic improvements accompanied the weight loss, including a 24.1 cm waist-circumference reduction and favourable changes in non-HDL cholesterol, triglycerides, systolic blood pressure, and hs-CRP. Full data is scheduled for the 86th ADA Scientific Sessions in June 2026. Sources: Lilly investor release, TCTMD, AJMC.
Efficacy Data — Phase 2 NEJM Trial (Historical Context)
The Phase 2 dataset anchoring retatrutide’s pre-Phase-3 positioning is the 48-week randomised, double-blind, placebo-controlled trial published by Jastreboff and colleagues in the New England Journal of Medicine (June 2023). The trial enrolled 338 adults with obesity without type 2 diabetes and tested four retatrutide doses (1, 4, 8, 12 mg) against placebo.
| Dose | Mean weight change | ≥15% weight loss |
|---|---|---|
| Placebo | −2.1% | Minimal |
| 1 mg | −8.7% | — |
| 4 mg | −17.1% | — |
| 8 mg | −22.8% | — |
| 12 mg | −24.2% | 83% of participants |
Two features of the Phase 2 readout shaped retatrutide’s Phase 3 positioning. First, the dose-response was steep and orderly — every dose step produced meaningfully greater weight loss, which is a strong signal that the mechanism is active at the receptor level. Second, the 12 mg weight-loss curve had not plateaued at 48 weeks, implying longer dosing windows (as in TRIUMPH) could push efficacy higher still.
For cross-class context, semaglutide 2.4 mg produced ~15% weight loss at 68 weeks in STEP 1, and tirzepatide 15 mg produced ~22.5% at 72 weeks in SURMOUNT-1. Retatrutide’s 48-week number exceeds both, and the triple-agonist architecture provides a plausible mechanism. For a three-way breakdown, see Retatrutide vs Tirzepatide vs CagriSema.
A Phase 2 sub-study in JCEM (Pearson et al, May 14, 2026) profiled plasma metabolomics and lipidomics in 282 participants with obesity and 213 with type 2 diabetes. Higher retatrutide doses drove a coordinated rise in fatty-acid oxidation markers — 3-hydroxybutyrate, acetylcarnitine, and long-chain acylcarnitines — that mediated 23.2% of the weight-reduction response in the obesity arm versus only 12.7% in the T2D arm. Branched-chain amino acids, 2-aminoadipic acid, and urate — all insulin-resistance markers — fell across both populations, alongside a reduction in triglycerides enriched for short-chain and saturated acyl chains. The signal suggests retatrutide changes how weight is lost, not just how much, with measurably different metabolic mediation in obesity-only versus obesity-plus-diabetes.
Safety & Tolerability
Retatrutide’s Phase 2 safety profile was consistent with the GLP-1 class, layered with glucagon-related signals requiring further characterisation in Phase 3:
- Most common AEs: nausea, diarrhea, vomiting, constipation, decreased appetite — the standard GLP-1/GIP agonist profile, concentrated in dose-escalation phases.
- Heart rate: A modest dose-dependent increase in resting heart rate was observed, consistent with glucagon-receptor activation. The clinical significance is being monitored in TRIUMPH.
- Glycemic control: The balanced triple agonism produced neutral to favourable glycemic effects in Phase 2; HbA1c was not adversely affected.
- Hepatic fat: Retatrutide reduced hepatic fat content in Phase 2 substudy participants, consistent with the glucagon-arm mechanism.
No unexpected safety signals were reported in Phase 2. Long-term tolerability, cardiovascular outcomes, and discontinuation rates at commercial-intent doses are being characterised in TRIUMPH. For a dose-by-dose breakdown, see Phase 3 safety & adverse-event rates below. For a broader checklist of HbA1c, CMP, lipid, thyroid, and pancreatic-risk labs used before GLP-1-class protocols, see blood tests before starting GLP-1s and peptides.
Phase 3 Safety & Adverse-Event Rates
The Phase 2 dataset (Jastreboff et al., NEJM 2023) and the Phase 3 TRIUMPH-1 (May 2026), TRIUMPH-4 (December 2025), and TRANSCEND-T2D-1 (March 2026) topline readouts together form the most comprehensive safety dataset for retatrutide to date. The composite picture is consistent: gastrointestinal events dominate, severity is mostly mild-to-moderate, discontinuation runs in the single digits to low double digits at the highest dose, and titration design is the strongest tolerability lever.
TRIUMPH-1 dose-by-dose tolerability (May 21, 2026)
| Endpoint | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| AE-driven discontinuation | 4.1% | 6.9% | 11.3% | 4.9% |
| Dysesthesia | — | up to 12.5% | — | |
| Urinary tract infections | Noted in topline release; rates not yet quantified publicly | |||
| Adverse events — most common | Gastrointestinal (nausea, diarrhea, vomiting, decreased appetite); concentrated in dose-escalation window | |||
The TRIUMPH-1 dose-dependent discontinuation curve (4.1% / 6.9% / 11.3% vs 4.9% on placebo) is well below the 18.2% AE-driven discontinuation seen in the older TRIUMPH-4 obesity readout, validating the optimised 2 mg start with 4-week escalation steps adopted across the Phase 3 program. Dysesthesia at 12.5% sits between the TRIUMPH-4 high-dose signal and the lower TRANSCEND-T2D-1 incidence (2.3–4.5%). The new UTI signal is the most notable late-emerging observation and will be characterised in the full ADA presentation. Full data: 86th ADA Scientific Sessions, June 2026.
TRIUMPH-1 vs TRIUMPH-4 — tolerability at the 12 mg dose
The clearest read on retatrutide’s evolving tolerability is the side-by-side comparison of the two high-dose obesity readouts. The pivotal TRIUMPH-1 obesity cohort showed improved tolerability versus the older TRIUMPH-4 (obesity plus knee osteoarthritis) figures on both the dysesthesia signal and AE-driven discontinuation.
| Endpoint (12 mg) | TRIUMPH-1 (obesity, no T2D) | TRIUMPH-4 (obesity + knee OA) |
|---|---|---|
| Dysesthesia | 12.5% | 20.9% |
| AE-driven discontinuation | 11.3% | 18.2% |
Both the dysesthesia rate (12.5% vs 20.9%) and AE-driven discontinuation (11.3% vs 18.2%) ran lower in TRIUMPH-1 than in TRIUMPH-4, consistent with the cleaner obesity-only population and the optimised titration schedule. Sources: Reuters, STAT, Fierce Biotech.
Phase 2 GI rates by dose & titration design
| Dose Cohort | Titration Design | Nausea | Diarrhea | Vomiting |
|---|---|---|---|---|
| Placebo | — | 12.5% | 8.3% | 4.2% |
| 0.5 mg | No escalation | 8.9% | 6.7% | 2.2% |
| 4 mg | Slow (2→4 mg) | ~22% | ~13% | ~7% |
| 4 mg | Rapid (start at 4 mg) | ~36% | ~20% | ~13% |
| 8 mg | Slow (2→4→8 mg) | ~33% | ~22% | ~11% |
| 8 mg | Rapid (start at 4 mg) | ~60% | ~31% | ~18% |
| 12 mg | Slow (2→4→8→12 mg) | 45.8% | 33.3% | 16.7% |
Key finding: The 8 mg rapid-start cohort produced higher nausea (~60%) than the 12 mg slow-titration cohort (45.8%), even though the final dose was lower. Nausea incidence is dose dependent, but titration schedule is the primary tolerability lever — starting at 2 mg rather than 4 mg before escalation reduced nausea incidence by 30–50%. Phase 2 used four-week dose-escalation steps to allow adaptation during the treatment period (Jastreboff et al., NEJM 2023, Table 3).
Cross-class comparison — retatrutide vs tirzepatide vs semaglutide
| Side Effect | Retatrutide (12 mg) | Tirzepatide (15 mg) | Semaglutide (2.4 mg) | Placebo |
|---|---|---|---|---|
| Nausea | 45.8% | 29.0% | 44.2% | 12.5% |
| Diarrhea | 33.3% | 23.0% | 30.0% | 8.3% |
| Vomiting | 16.7% | 12.0% | 24.8% | 4.2% |
| Constipation | 16.7% | 11.0% | 24.2% | 4.2% |
| Dyspepsia | 8.3% | 9.0% | 8.0% | 2.1% |
| Abdominal pain | 8.3% | 6.0% | 6.5% | 4.2% |
| Discontinuation (AE) | ~6–8% | ~4–7% | ~5–7% | ~3% |
Retatrutide’s GI side-effect rates sit in the same general range as tirzepatide and semaglutide, but peak nausea can run modestly higher at the most aggressive dose levels. Per unit of weight reduction (~24% at 12 mg vs ~22.5% tirzepatide, ~15% semaglutide), the tolerability profiles are broadly comparable. Discontinuation rates fall in a comparable band across the class.
Severity stratification
Phase 2 trial reports describe retatrutide adverse events as predominantly mild-to-moderate, with severe events under 5% per individual AE category. Overall AE-driven discontinuation across active dose groups was approximately 6–8% in Phase 2 and 2.2–5.1% across TRANSCEND-T2D-1 dose arms.
| Adverse Event | % Mild | % Moderate | % Severe | % Leading to Discontinuation |
|---|---|---|---|---|
| Nausea | Majority mild | Minority moderate | <5% reported | ≤8% (overall AE-driven discontinuation, all causes) |
| Diarrhea | Majority mild | Minority moderate | <5% reported | ≤8% (overall AE-driven discontinuation, all causes) |
| Vomiting | Majority mild-to-moderate | Minority moderate | <5% reported | ≤8% (overall AE-driven discontinuation, all causes) |
| Constipation | Majority mild | Minority moderate | Rare | Trial-reported as low |
| Dysesthesia | Majority mild-to-moderate | Minority moderate | Rare per TRIUMPH-4 | Trial-reported as low |
| Injection-site reactions | Majority mild | Minority moderate | Rare | Trial-reported as low |
GI symptom timeline — onset, peak, resolution
Trial narrative reports describe a consistent onset/peak/resolution pattern for the GI category, with most events concentrated in the dose-escalation window.
| Adverse Event | Onset (Week 1–2) | Peak (Week 2–4) | Resolution (Week 4–8) |
|---|---|---|---|
| Nausea | Within first 1–2 weeks of new dose level | Peaks during weeks 2–4 of titration | Tolerance develops with continued dosing; generally resolves by week 4–8 |
| Diarrhea | Within first 1–2 weeks of new dose level | Peaks during weeks 2–4 of titration | Predominantly transient and self-limiting |
| Vomiting | Most events during initial titration period | Peaks during weeks 2–4 of titration | Diminishes as participants reach maintenance dose |
| Dysesthesia | Trial-reported timing not stratified by week | Trial-reported timing not stratified by week | TRANSCEND-T2D-1 narrative: generally mild, resolving during treatment |
| Injection-site reactions | May appear within 24–72h post-dose | Transient | Self-limiting in most cases (24–48h without intervention) |
Severe abdominal pain was reported in a small subset of Phase 2 participants at higher doses. Trial reports describe pain that persists beyond 48 hours or is accompanied by persistent vomiting as a flag for further investigation, with acute pancreatitis included in the differential and pancreatic enzymes (serum amylase, lipase) measured to rule out acute pancreatic disorders. No confirmed pancreatitis signal has been reported in Phase 2 or Phase 3 readouts to date, but the GLP-1 class warning applies by mechanism.
TRIUMPH-4 Phase 3 update (December 2025)
Eli Lilly reported topline results from the TRIUMPH-4 Phase 3 trial on December 11, 2025. TRIUMPH-4 evaluated retatrutide in adults with obesity and knee osteoarthritis across a larger and more diverse population than Phase 2, using the optimised slow-titration protocol informed by Phase 2 dose-finding. Topline results confirmed that retatrutide met its primary efficacy endpoint. Lilly’s announcement indicated the safety profile was broadly consistent with Phase 2 — gastrointestinal events remained the most common adverse events, no new safety signals were identified, and discontinuation rates were comparable to Phase 2. Dysesthesia — tingling/numbness — was reported at the high dose at frequencies higher than placebo (TRIUMPH-4 high-dose stat-chip approximation: ~20.9%). Full TRIUMPH-4 safety tables are expected in a peer-reviewed publication in 2026.
TRANSCEND-T2D-1 Phase 3 readout (March 2026)
On March 19, 2026, Eli Lilly announced topline results from TRANSCEND-T2D-1 — the first Phase 3 trial evaluating retatrutide in type 2 diabetes. The 40-week, placebo-controlled study randomised 537 participants to retatrutide 4 mg, 9 mg, or 12 mg (starting at 2 mg with four-week dose escalation) or placebo.
| Adverse Event | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 16.4% | — | 26.5% | 3.7% |
| Diarrhea | 18.7% | — | 26.3% | 4.5% |
| Vomiting | 15.0% | — | 17.6% | 2.2% |
| Dysesthesia | 2.3% | — | 4.5% | 0% |
| Discontinuation (AE) | 2.2% | 4.5% | 5.1% | 0% |
Notably, nausea rates in TRANSCEND-T2D-1 (16.4–26.5%) ran substantially lower than in the Phase 2 trial (up to 45.8% at 12 mg), likely reflecting the optimised 2 mg initiation and slower titration protocol adopted for Phase 3. Dysesthesia — the tingling/numbness signal first flagged in TRIUMPH-4 — occurred in 2.3–4.5% of retatrutide-treated participants and was described as generally mild, resolving during treatment. Discontinuation rates due to adverse events were low across all doses (2.2–5.1%). Detailed TRANSCEND-T2D-1 safety results will be presented at the American Diabetes Association Scientific Sessions in June 2026.
Heart rate & cardiovascular signals
The Phase 2 trial identified small, dose-dependent increases in resting heart rate among retatrutide-treated participants. Mean heart rate increases of approximately 2–4 beats per minute (bpm) were observed at the higher dose levels, consistent with the well-documented class effect of GLP-1 receptor agonists. Semaglutide and tirzepatide both produce similar modest heart rate elevations of 1–4 bpm in their respective Phase 3 programmes. The mechanism is believed to involve GLP-1 receptor-mediated effects on the sinoatrial node and sympathetic nervous system modulation.
No major adverse cardiovascular events (MACE) were identified as attributable to retatrutide in the Phase 2 trial. No clinically significant arrhythmias, QT prolongation, or blood pressure abnormalities were reported at rates above placebo. Phase 2 was not powered to detect rare cardiovascular events — TRIUMPH-3 is the dedicated cardiovascular outcomes trial that will provide definitive long-term CV safety data.
Class-wide safety considerations
| Safety consideration | Retatrutide | Tirzepatide | Semaglutide |
|---|---|---|---|
| Pancreatitis | Class warning; no confirmed signal in Phase 2/3 | Class warning per FDA label | Class warning per FDA label |
| Gallbladder events | Class warning; trial-reported as low | Class warning per FDA label | Class warning per FDA label |
| MTC / thyroid C-cell tumors | Class warning (rodent data) | Boxed warning per FDA label | Boxed warning per FDA label |
| MACE / cardiovascular | Pending dedicated CV outcome data (TRIUMPH-3) | CV outcomes data developing | LEADER, SUSTAIN-6: positive CV outcomes (semaglutide) |
| Suicidal ideation FDA review | Investigational; class included in 2024 FDA review | Included in 2024 FDA review (no causal link found) | Included in 2024 FDA review (no causal link found) |
Class-wide considerations reference FDA labels for tirzepatide (Mounjaro/Zepbound) and semaglutide (Wegovy/Ozempic). Retatrutide entries reflect investigational status; class warnings apply by mechanism. Combining GLP-1 receptor agonists with insulin or sulfonylureas increases the risk of hypoglycemia — a documented class effect that applies to retatrutide by mechanism. Trial protocols typically reduce concomitant insulin or sulfonylurea doses when GLP-1 agonists are added.
How It Compares — Retatrutide vs Tirzepatide vs CagriSema
Retatrutide sits at the mechanistic top of the obesity pipeline. Tirzepatide (Eli Lilly, approved as Mounjaro and Zepbound) is a dual GLP-1/GIP agonist. CagriSema (Novo Nordisk, NDA filed December 2025) is a GLP-1/amylin co-formulation. Retatrutide adds a glucagon arm that neither of those candidates has, which is the source of its weight-loss ceiling advantage in cross-trial comparison.
On efficacy, retatrutide’s Phase 3 TRIUMPH-1 12 mg result (28.3% at 80 weeks; 30.3% at 104 weeks in the BMI ≥35 extension) exceeds tirzepatide 15 mg in SURMOUNT-1 (~22.5% at 72 weeks) and CagriSema in REDEFINE 1 (~22.7% at 68 weeks). Timeline position is inverted: CagriSema is closest to market (FDA decision expected ~October 2026), tirzepatide is already approved, and retatrutide is still working through TRIUMPH. For a full comparative breakdown, see retatrutide vs tirzepatide vs CagriSema, and for orforglipron-specific context, see retatrutide vs orforglipron.
Research Use Notes
Remy Peptides supplies HPLC-verified retatrutide pens for in-vitro laboratory research. Current batch flow: Retatrutide Pen 30 mg, 300 clicks at 0.1 mg per click, 99.262% HPLC purity, Janoshik Analytical Batch RETP002. Reference the COA library for batch documents. For reconstitution and handling, see the bacteriostatic water guide and the reconstitution calculator.
Retatrutide is not approved for human therapeutic use in any territory. Remy Peptides material is supplied strictly for in-vitro research. For regional research context, see the retatrutide in Dubai guide and Retatrutide UAE availability page.
All Remy Peptides products are supplied for in-vitro laboratory research only. Not for human or veterinary use. UAE MoHAP Circular 17/2022 compliance statement.
Further reading
Our Research Standards
This article cites peer-reviewed studies, FDA filings, and ClinicalTrials.gov data. All claims are cross-referenced against primary sources. We update articles when new trial data or regulatory decisions are published. Read our editorial policy →
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- Eli Lilly. TRIUMPH programme: Phase 3 clinical trials of retatrutide in obesity. Pipeline overview. investor.lilly.com
- ClinicalTrials.gov. TRIUMPH-1: A Study of Retatrutide (LY-3437943) in Participants With Obesity (NCT05929066). clinicaltrials.gov
- ClinicalTrials.gov. TRIUMPH-3: A Study of Retatrutide in Participants With Obesity and Cardiovascular Disease (NCT05882045). clinicaltrials.gov
- ClinicalTrials.gov. TRIUMPH-4: A Study of Retatrutide in Participants With Obesity and Osteoarthritis of the Knee (NCT05816642). clinicaltrials.gov
- Coskun T, Urva S, Roell WC, et al. LY-3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metab. 2022;34(9):1234-1247. cell.com
- Eli Lilly and Company. Lilly’s retatrutide (LY-3437943) met primary endpoint in TRIUMPH-4 Phase 3 obesity trial. Press release, December 11, 2025. investor.lilly.com
- Eli Lilly and Company. TRANSCEND-T2D-1 topline results — Phase 3 type 2 diabetes trial. Press release, March 19, 2026. investor.lilly.com
- Eli Lilly and Company. Lilly’s triple agonist retatrutide delivered powerful weight loss in TRIUMPH-1 Phase 3 pivotal trial. Press release, May 21, 2026. investor.lilly.com
- TCTMD. Retatrutide achieves large weight decreases in patients without diabetes: TRIUMPH-1. May 2026. tctmd.com
- AJMC. Retatrutide achieves up to 30.3% average weight loss in Phase 3 TRIUMPH-1 trial. May 2026. ajmc.com
- U.S. Food and Drug Administration. Prescribing information for tirzepatide (Mounjaro/Zepbound) and semaglutide (Wegovy/Ozempic) — class warnings reference. accessdata.fda.gov
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