Investigational science LY3437943
Retatrutide: the investigational triple-receptor agonist
What the Phase 3 evidence shows, and what remains unknown. A physician-reviewed science briefing for India.
Retatrutide (LY3437943) is an investigational once-weekly triple agonist that activates the GIP, GLP-1 and glucagon receptors. In the Phase 3 TRIUMPH-1 trial of 2,339 adults it produced a mean weight loss of 28.3% at 80 weeks. It is not approved for prescription or purchase anywhere in the world, including India, as of June 2026.
What it is
Three control levers, one weekly injection
Your body makes three gut hormones that regulate weight and blood sugar: GLP-1, GIP, and glucagon. Think of them as three control levers. Most approved weight-loss injections pull only one or two. Retatrutide pulls all three at once.
Signals the brain to feel full and helps the pancreas release insulin. Semaglutide pulls only this lever.
Pulled by: semaglutide (Ozempic, Wegovy)
Boosts the insulin signal and amplifies GLP-1's appetite effect. Tirzepatide pulls GLP-1 and GIP, which is why it produces more weight loss than semaglutide alone.
Pulled by: tirzepatide (Mounjaro)
When balanced against the other two, it tells the liver to release stored fat for energy and turns up the body's calorie-burning furnace. No approved drug pulls this lever at the same time as the other two.
Pulled by: retatrutide (investigational)
For clinicians
- Molecule: LY3437943, an acylated 36-amino-acid synthetic peptide with fatty-acid-driven, FcRn-independent half-life extension.
- Receptor potency vs endogenous ligands: GIPR ~8.9x (supraphysiological), GLP-1R ~0.4x (partial), GCGR ~0.3x (attenuated). The profile is intentionally GIPR-dominant.
- Half-life ~6 days, supporting once-weekly subcutaneous dosing.
- Titration in the trials: 2 mg, 4 mg, 9 mg, 12 mg in 4-week steps.
- Source: Coskun et al., Cell Metabolism 2022; Urva et al., Lancet 2022.
Mechanism, visualised
Watch the three levers fire
A stylised cell membrane. As the drug engages each receptor, the signal cascades to its target organ. The glucagon receptor, the third lever, fires last.
Retatrutide, one weekly injection, approaches the cell membrane.
Three receptors, one molecule. GLP-1R and GIPR are pulled by approved drugs today. The glucagon receptor is the lever no approved drug pulls at the same time.
The evidence so far
From first-in-human to pivotal Phase 3
The retatrutide programme moved from a 2022 Phase 1 study to a 2,339-patient Phase 3 obesity trial in four years. Some results are peer-reviewed; the largest are topline or congress-stage, with full manuscripts pending.
- 2022 Peer-reviewed
Phase 1 first-in-human
Phase 1Established once-weekly dosing and the GIPR-dominant receptor profile.
Urva et al., Lancet 2022
- Jun 2023 Peer-reviewed
Phase 2 obesity
Phase 2, n=33824.2% mean weight loss at 48 weeks (12 mg).
Jastreboff et al., NEJM June 2023
- 2024 Peer-reviewed
Phase 2 MASLD substudy
Phase 282.4% liver-fat reduction at 24 weeks; 93% normalised by 48 weeks.
Sanyal et al., Nature Medicine 2024
- Dec 2025 Topline
TRIUMPH-4 (osteoarthritis)
Phase 3, n~80028.7% weight loss at 68 weeks; WOMAC knee pain down 73.1%.
Eli Lilly topline, December 2025
- Mar 2026 Peer-reviewed
TRANSCEND-T2D-1 topline
Phase 3, n=537HbA1c down 1.94%; 16.8% weight loss in type 2 diabetes, with India trial sites.
Bajaj HS et al., Lancet 2026
- May 2026 Topline
TRIUMPH-1 topline
Phase 3, n=2,33928.3% weight loss at 80 weeks (12 mg); 30.3% at 104 weeks in a higher-BMI cohort.
Eli Lilly topline, May 2026
- Jun 2026 Topline
ADA congress presentation
Phase 3TRIUMPH-1 and TRANSCEND-T2D-1 detailed data presented at the ADA Scientific Sessions.
ADA 86th Scientific Sessions, June 2026
- Future Projected
NDA filing and DCGI pathway
RegulatoryNo application filed yet. Analyst projection: US NDA late 2026 to early 2027; India access realistically 2028 to 2030.
Projection, not a confirmed date
TRANSCEND-T2D-1 enrolled participants at trial sites in India, so Indian patients are part of the primary type 2 diabetes dataset, not an afterthought. (Bajaj HS et al., Lancet 2026)
Weight loss in context
Dose response in TRIUMPH-1
Weight loss rose with dose. The dashed band marks the range typically seen after bariatric surgery. Toggle to see how discontinuation, on its own scale, also rose with dose.
TRIUMPH-1 NCT05929066 · n=2,339 · 80 weeks
Eli Lilly topline + ADA 86th Scientific Sessions, June 2026. Topline plus congress presentation. Full peer-reviewed manuscript pending.
104-week extension (BMI 35 and above cohort): up to 30.3% (38.6 kg). 45.3% of 12 mg participants lost at least 30% of body weight.
Beyond the scale
What changed besides body weight
In TRIUMPH-1 and the diabetes and MASLD studies, retatrutide moved several cardiometabolic markers at the 12 mg dose. Each figure below names its trial.
TRIUMPH-1 (80 wk, 12 mg); TRANSCEND-T2D-1 (Lancet 2026); Sanyal et al. Nature Medicine 2024
The South Asian thin-fat phenotype carries high visceral and hepatic fat at a normal body weight, which is why MASLD and metabolic disease appear early here. India uses ICMR 2023 thresholds: overweight at BMI 23 and above, obese at BMI 25 and above, lower than the older Caucasian criteria. A triple agonist whose glucagon leg targets hepatic and visceral fat directly is mechanistically interesting for exactly this risk profile, though no India-specific retatrutide outcome data exist yet.
Safety, the full picture
Side effects rose with dose
Gastrointestinal effects are dose-dependent, most pronounced during escalation, and mostly mild to moderate.
| Adverse event | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 29% | 38% | 42.4% | 15% |
| Diarrhoea | 25% | 34% | 32% | 14% |
| Vomiting | 11% | 23% | 25.3% | 5% |
| Constipation | 24% | 26% | 26.1% | 11% |
| Discontinuation (AE) | 4.1% | 6.9% | 11.3% | 4.9% |
TRIUMPH-1 (ADA 2026); TRANSCEND-T2D-1 (Lancet 2026). Dysesthesia (tingling) and urinary tract infection were each reported in roughly 10% of participants, generally mild and mostly resolving.
What we do not yet know
Honest gaps- Does it reduce heart attacks, strokes, or cardiovascular death? The dedicated outcomes trial (CVOT) is years from reading out, around 2029.
- What proportion of the weight lost is lean muscle mass at Phase 3 scale?
- Does the observed heart-rate increase carry long-term clinical significance?
- What happens to weight after a patient stops the drug?
- What is the safety profile beyond two years of continuous use?
- How do outcomes compare specifically in the South Asian thin-fat phenotype?
The honest reading of these numbers is not “best drug,” it is “most studied drug at this dose, for this duration, in this population.”Dr. Rejeesh M. Menon, MD
How it compares
Triple, dual, and single agonists side by side
The numbers below come from separate trials. They show where each drug landed in its own study, not which drug is better.
| Drug | Mechanism | Peak weight loss | Trial | Stage | India status |
|---|---|---|---|---|---|
| Retatrutide | GIPGLP-1GCG | 28.3% / 80 wk | TRIUMPH-1 | Phase 3, investigational | Not filed |
| Tirzepatide (Mounjaro) | GIPGLP-1 | 22.5% / 72 wk | SURMOUNT-1 | Approved | DCGI approved |
| Semaglutide (Wegovy) | GLP-1 | ~15% / 68 wk | STEP-1 | Approved | DCGI approved; generic from Rs 750 |
| Survodutide | GLP-1GCG | 16.6% / 76 wk | SYNCHRONIZE-1 | Phase 3, not filed | Not filed |
| CagriSema | GLP-1AMY | 22.7% / 68 wk | REDEFINE-1 | NDA filed Dec 2025 | Not filed |
Sources: SURMOUNT-1, STEP-1, SYNCHRONIZE-1, REDEFINE-1, TRIUMPH-1 (topline / congress). Weight loss values are trial means.
What does "indirect comparison" mean, and why does it matter?
These figures come from separate clinical trials with different patient populations, durations, and designs. They cannot prove one drug is superior to another. The only randomised direct comparison, TRIUMPH-5 (NCT06662383, retatrutide versus tirzepatide), is still ongoing.
Until a randomised head-to-head trial reports, the only fair reading is that each drug produced its own result in its own study. Cross-trial percentage gaps can reflect differences in baseline weight, trial length, titration, and dropout handling, not the molecules themselves.
Regulatory status
Where approval actually stands
No agency has approved retatrutide, and no marketing application has been filed. The tracker below is a status board, not a forecast.
- US FDA Phase 3 complete, NDA pendingPhase 3NDA filedUnder reviewApproved
- EU EMA Awaiting US filingPhase 3NDA filedUnder reviewApproved
- India DCGI Not filedEarliest 2028 to 2030 (projection)Phase 3NDA filedUnder reviewApproved
Last updated: June 2026
- No FDA, EMA, or DCGI approval exists as of June 2026.
- No New Drug Application has been filed with any agency. Analyst projection: US NDA late 2026 to early 2027, FDA decision 2027 to 2028.
- India: no DCGI application is known. Realistic earliest access is 2028 to 2030 (a projection, not a fact).
- An April 2026 MoHFW and CDSCO advisory restricts GLP-1 prescribing to endocrinologists, internal medicine physicians, and cardiologists.
- A March 2026 CDSCO advisory directs all GLP-1 manufacturers to avoid direct and indirect public advertising.
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Why you cannot buy this drug
The grey market, in plain terms
Vials sold online as retatrutide are not the trial drug. There is no legal, supervised route to retatrutide outside a clinical trial, and self-injection of unregulated peptides carries real risk.
- "Research use only" peptides are intended for laboratory or animal use, not human injection.
- There is no GMP quality control. A vial may contain the wrong dose, the wrong substance, or contamination.
- No prescribing information or titration supervision exists outside the clinical trials.
- CDSCO is actively auditing unauthorised GLP-1 sellers.
- Importing an unapproved drug without a DCGI licence violates the Drugs and Cosmetics Act 1940.
Available now
Proven options exist while retatrutide is still in trials
While retatrutide remains investigational, physician-supervised metabolic health therapies are available now. Our team uses DCGI-approved GLP-1 therapies and India-specific metabolic assessment protocols, with Indian BMI thresholds (overweight at 23, obese at 25).
Questions patients ask
Retatrutide, answered honestly
What is retatrutide and how does it work?
Retatrutide (LY3437943) is an investigational once-weekly injection that activates three metabolic hormone receptors at the same time: GIP, GLP-1, and glucagon. It is being developed by Eli Lilly and is not approved anywhere in the world as of June 2026.
How much weight loss does retatrutide cause in clinical trials?
In the Phase 3 TRIUMPH-1 trial (n=2,339), the 12 mg dose produced a mean weight loss of 28.3% at 80 weeks, and up to 30.3% at 104 weeks in a higher-BMI cohort. These are trial averages, not guaranteed individual outcomes.
Is retatrutide approved in India?
No. Retatrutide has no DCGI or CDSCO approval and no approval from any regulatory agency worldwide. It cannot be legally prescribed or purchased in India.
When will retatrutide be available in India?
No one can say with certainty. No application has been filed with the DCGI. A realistic earliest estimate is 2028 to 2030, depending on US FDA approval and a subsequent India filing. This is a projection, not a confirmed date.
What are the side effects of retatrutide?
The most common side effects are gastrointestinal: nausea (42% at 12 mg), diarrhoea (32%), and vomiting (25%). Dysesthesia (tingling) and urinary tract infection were also reported at around 10%. Side effects are dose-dependent and mostly mild to moderate.
Is retatrutide better than semaglutide or tirzepatide?
Cross-trial numbers suggest greater weight loss, but these are indirect comparisons from different studies and cannot establish superiority. No completed head-to-head trial exists. TRIUMPH-5 (retatrutide versus tirzepatide) is the ongoing direct comparison.
Can I buy retatrutide in India?
No. Any product marketed as retatrutide for human use in India is unauthorised. "Research use only" peptides are not manufactured to pharmaceutical standards and are not safe for self-injection. CDSCO is actively auditing unauthorised GLP-1 sellers.
What is the TRIUMPH-1 trial?
TRIUMPH-1 (NCT05929066) is the pivotal Phase 3 obesity trial of retatrutide. It enrolled 2,339 adults with obesity or overweight and tested 4 mg, 9 mg, and 12 mg doses over 80 weeks. Topline results were announced in May 2026 and presented at ADA in June 2026.
Does retatrutide help with fatty liver (MASLD)?
In a Phase 2 substudy, retatrutide 12 mg reduced liver fat by 82.4% at 24 weeks, with 93% of participants reaching normal levels at 48 weeks. This is the largest pharmacological liver-fat reduction reported so far. Phase 3 MASLD data are awaited.
What is the BMI threshold for metabolic treatment in India?
India uses ICMR 2023 thresholds: overweight at BMI 23 and above, and obese at BMI 25 and above. These are lower than the older Caucasian criteria of 25 and 30 because South Asians develop metabolic complications at lower body weights.
What GLP-1 options are available in India right now?
DCGI-approved options include semaglutide (Ozempic, Wegovy, and generics from around Rs 750 per dose), tirzepatide (Mounjaro), and liraglutide (Victoza). These must be prescribed by a qualified physician, such as an endocrinologist, internal medicine specialist, or cardiologist, under the April 2026 advisory.
What does "investigational" mean?
It means the drug is still being studied in clinical trials and has not received regulatory approval for prescription, sale, or use outside those trials. It is not commercially available, and its benefit-to-risk balance has not been fully established by any regulatory authority.
Internal Medicine, Founder and Chairman, DermaVue Clinics
Every clinical figure on this page was checked against the underlying trial releases and publications listed below. Where data is topline or congress-stage rather than peer-reviewed, the page says so. Retatrutide is investigational; nothing here is a recommendation to obtain or use it. Last reviewed: June 2026.
Sources and references
- Coskun et al., Cell Metabolism 2022. LY3437943 molecular pharmacology and receptor potency profile.
- Urva et al., Lancet 2022. Phase 1 first-in-human pharmacokinetics and once-weekly dosing.
- Jastreboff et al., NEJM 2023. Phase 2 obesity trial, 48-week weight-loss outcomes.
- Sanyal et al., Nature Medicine 2024. Phase 2 MASLD substudy, liver-fat reduction.
- Bajaj HS et al., Lancet 2026. TRANSCEND-T2D-1 Phase 3 type 2 diabetes trial with India sites.
- Eli Lilly topline releases 2025 to 2026; ADA 86th Scientific Sessions, June 2026. TRIUMPH-1 and TRIUMPH-4 results (topline plus congress, full manuscripts pending).
- ICMR 2023 consensus guidelines. Indian BMI thresholds: overweight 23 and above, obese 25 and above.
- CDSCO advisories, March and April 2026. GLP-1 advertising restriction and prescriber-specialty restriction.
Trial registry: TRIUMPH-1 (NCT05929066) TRIUMPH-5 (NCT06662383)
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