Research Compound Profile

Retatrutide

LY3437943  ·  Triple GLP-1 / GIP / GCGR Agonist

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Research Areas

Obesity, Type 2 Diabetes, Fatty liver disease (MASLD)

FDA Status

Not FDA-approved

WADA Status

Prohibited (S0)

Routes

SC Injection (clinical)

Overview

Retatrutide (LY3437943) is a synthetic 39-amino acid peptide developed by Eli Lilly and Company as a next-generation incretin-based metabolic therapy [1]. It is conjugated to a C20 fatty diacid moiety, which prolongs its plasma half-life and enables once-weekly subcutaneous dosing. As a first-in-class "triple G" or "tri-agonist," retatrutide is specifically engineered to simultaneously activate three distinct metabolic receptors: GLP-1, GIP, and the glucagon receptor (GCGR) [1].

Retatrutide is currently an investigational compound. It is not approved by the FDA for any commercial use. Phase 3 registrational trials (the TRIUMPH program) are actively ongoing as of early 2026.

Research Areas and Claims

In Phase 2 clinical trials, retatrutide has demonstrated significant effects across several metabolic disease areas:

  • Obesity & Weight Loss: At 48 weeks, the 12 mg dose produced a mean body weight reduction of 24.2% — among the highest ever recorded in a clinical obesity trial [2].

  • Type 2 Diabetes (Glycemic Control): HbA1c reduced by up to 2.16 percentage points at 36 weeks, significantly outperforming placebo and an active comparator (dulaglutide 1.5 mg) [3].

  • Fatty Liver Disease (MASLD/NAFLD): Liver fat reduced by up to 82.4% in 24 weeks; 86% of participants on the 12 mg dose achieved completely normal liver fat levels (<5%) [4].

  • Body Composition: DEXA substudy confirmed significant reductions in total fat mass; lean mass loss was proportionally similar to other obesity treatments [5].

  • Appetite Suppression: Higher doses significantly reduced overall appetite, hunger, and tendency to overeat; these behavioral changes correlated strongly with weight lost [6].

Mechanism of Action

Retatrutide activates three distinct hormone receptors simultaneously — a key distinction from dual-agonists like tirzepatide (GLP-1 + GIP only).

  1. GLP-1 Receptor Agonism: Slows gastric emptying, increases glucose-dependent insulin secretion, and signals the brain to reduce appetite and increase satiety [1].
  2. GIP Receptor Agonism: Synergizes with GLP-1 to enhance insulin secretion and further suppress appetite, while also regulating energy storage [1].
  3. Glucagon Receptor (GCGR) Agonism: The unique addition compared to dual-agonists. GCGR activation directly increases hepatic lipid metabolism (clearing liver fat) and raises systemic energy expenditure — effectively increasing the body's basal metabolic rate [1][2].

Dosing Schedule (Clinical Context)

Important: Retatrutide is an investigational drug. It is not currently FDA-approved for commercial use, and there is no approved commercial dosing guideline. The following reflects Phase 2 clinical trial parameters only.

  • Route: Subcutaneous (SC) injection — abdomen, thigh, or upper arm [2].

  • Frequency: Once-weekly injection [2].

  • Starting dose: 1 mg or 2 mg per week, escalated gradually every 4 weeks to mitigate GI side effects [2].

  • Maintenance doses studied: 4 mg, 8 mg, and 12 mg per week [2][3].

Clinical Trials

The following Phase 2 trials are published in PubMed. Phase 3 registrational trials (the TRIUMPH program — TRIUMPH-1, 2, 3, 4) are currently ongoing; no primary Phase 3 efficacy results are published as of early 2026.

Phase 2 Obesity Trial (2023)

Phase Phase 2
Route SC
Subjects 338 adults with obesity
Duration 48 weeks
Key Finding 24.2% mean weight reduction at 12 mg dose; 100% lost ≥5% body weight at 8 mg and 12 mg
Ref [2]

Phase 2 Type 2 Diabetes Trial (2023)

Phase Phase 2
Route SC
Subjects 281 with Type 2 Diabetes
Duration 36 weeks
Key Finding HbA1c reduced up to 2.16%; up to 16.9% weight loss; outperformed dulaglutide
Ref [3]

Phase 2a MASLD/NAFLD Trial (2024)

Phase Phase 2a
Route SC
Subjects 98 with MASLD (liver fat ≥10%)
Duration 24 weeks
Key Finding Up to 82.4% liver fat reduction; 86% of 12 mg group achieved normal liver fat (<5%)
Ref [4]

Phase 2 Body Composition Substudy (2025)

Phase Phase 2 (substudy)
Route SC
Subjects 189 with Type 2 Diabetes
Duration 36 weeks
Key Finding Significant fat mass reduction vs. placebo (via DEXA); lean mass loss proportionally similar to other obesity treatments
Ref [5]

Phase 2 Appetite Substudy (2025)

Phase Phase 2 (substudy)
Route SC
Subjects Adults with Type 2 Diabetes
Duration 36 weeks
Key Finding Higher doses significantly reduced appetite, hunger, and overeating; behavioral changes correlated strongly with weight lost
Ref [6]

Phase 3 (TRIUMPH): Four large-scale registrational trials are actively enrolling as of early 2026, evaluating retatrutide for weight management, obesity with obstructive sleep apnea, cardiovascular outcomes, and knee osteoarthritis. No primary Phase 3 results are published yet.

Regulatory Status & Limitations

  • FDA Status: Not FDA-Approved. Retatrutide is an investigational drug with no approved commercial formulation, indication, or dosing guideline as of March 2026.
  • Sports Compliance: Prohibited. As a non-approved peptide, retatrutide falls under WADA's S0 (Non-approved substances) category and is prohibited in sport.
  • Research-Chemical Market: Current grey-market availability is sold strictly as research chemicals. Purity, authenticity, and long-term safety are not independently verified.
  • Product Name Obfuscation: Due to regulatory and marketing sensitivities, most vendors list retatrutide under alternate names (GLP-RT, GLP-3 Retatrutide, R3tatrutide, LY3437943, Reta 10mg GLP-3). Always verify the CAS number: 2381089-83-2.
  • What We Don't Know: No Phase 3 efficacy results are published. Long-term safety, optimal dosing, and durability of effects beyond 48 weeks in humans remain under investigation.

Market Overview

Please note: The following data is based on March 2026 pricing from Finnrick A-rated vendors only. All products are strictly sold as research chemicals. Prices fluctuate based on volume, batch, purity, and presentation. Retatrutide is not yet commercially approved.

Injectable

SC

Lyophilized powder vials for subcutaneous research use. Kit pricing available from select vendors.

  • Price Range: $2.67 – $37.02 per mg
  • Typical Sizes: 5mg – 480mg (kits available)
  • Vendors with pricing: 7

Vendor Directory

Data collected March 2026. Finnrick A-rated vendors only. Tables sorted by $/mg ascending.

SC Injection — Lyophilized Powder

Peptide Haven

Sizes (mg) 10 / 30 / 60 / 100 (kit) / 300 (kit)
Price Range ($/mg) $2.67 – $8.00
Listed as GLP-RT
Website thepeptidehaven.com

Peptide Partners Finnrick #2

Sizes (mg) 48 / 120 / 240 / 480 (kits)
Price Range ($/mg) $3.50 – $5.69
Listed as GLP-3 Retatrutide
Website peptide.partners

Paradigm Peptide Finnrick #1

Sizes (mg) 20 / 50
Price Range ($/mg) $9.00 – $10.00
Listed as R3tatrutide
Website paradigm-peptide.com

NuScience Peptides

Sizes (mg) 5 / 10 / 20 / 25 / 30 / 40 / 50 / 100 / 150
Price Range ($/mg) $9.66 – $17.80
Listed as GLP-3 RT
Website nusciencepeptides.com

NUPEPS Peptides

Sizes (mg) 10
Price ($/mg) $13.00
Website nupeps.com

Loti Labs

Sizes (mg) 10
Price ($/mg) $16.00 – $20.00 †
Listed as Reta 10mg (GLP-3)
Website lotilabs.com

Pure Rawz

Sizes (mg) 5 / 8 / 10 / 12
Price Range ($/mg) $33.90 – $37.02
Listed as LY3437943
Website purerawz.co

† Kit / multi-pack pricing. Best $/mg at Peptide Haven 300mg kit ($2.67/mg). Loti Labs tiers: single $20.00/mg → 6+ vials $16.00/mg.

No Public Price / Not Available

20 Finnrick A-rated vendors have no public pricing for retatrutide as of March 2026.

Vendor Reason
Orbitrex Peptides (#3) Website "Coming Soon" as of Mar 2026
Atomik Labz Gated website; all pages redirect to login
Peptide Crafters Gated website (login required)
NuLife Peptides Gated website; redirects to guest login
Bulk Peptide Wholesale Perfect Finnrick score (10.0); no retatrutide product found on site
NextechLabs Domain for sale ($19,995); defunct as of Mar 2026
SubQ Society Private membership community; not a public retail site
9 Reddit/direct vendors Operate exclusively via r/saferpeptides; no public retail website (Lipeptides, Shandong Shengyuan, Huaian Hanyou, GYC, YB Peptide, Lisa Biopeptide, Zhang TY, Lux Synth Aminos, OmegAmino)
Zenith Jove / Risynth Bio / PurePeptides China-based direct only, private/restricted, or no website found

References

  1. [1]

    Coskun T, et al. "LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss." Cell Metab. 2022. pubmed.ncbi.nlm.nih.gov/36001968

  2. [2]

    Jastreboff AM, et al. "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial." N Engl J Med. 2023. pubmed.ncbi.nlm.nih.gov/37366315

  3. [3]

    Rosenstock J, et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial." Lancet. 2023. pubmed.ncbi.nlm.nih.gov/37385280

  4. [4]

    Sanyal AJ, et al. "Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial." Nat Med. 2024. pubmed.ncbi.nlm.nih.gov/38858523

  5. [5]

    Frias JP, et al. "Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial." Lancet Diabetes Endocrinol. 2025. pubmed.ncbi.nlm.nih.gov/40609566

  6. [6]

    Wharton S, et al. "Appetite, eating attitudes, and eating behaviours during treatment with retatrutide in adults with type 2 diabetes: Results of a phase 2 study." Diabetes Obes Metab. 2025. pubmed.ncbi.nlm.nih.gov/40916752

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