VK2735 vs Retatrutide: Which Investigational Incretin Agonist Leads the Injectable Obesity Pipeline?
VK2735's Phase 2 VENTURE trial showed 14.7% weight loss at 13 weeks; retatrutide's TRIUMPH-1 reported 28.3% at 80 weeks. Compare mechanisms and trial data.
Research reference only. The information in this article is a summary of peer-reviewed scientific literature. It does not constitute medical advice and is not intended to guide human use. See our full disclaimer.
VK2735 vs retatrutide are the two multi-receptor incretin agonists furthest along in the investigational obesity pipeline behind tirzepatide, and researchers comparing them are really comparing two different bets on how many metabolic receptors are worth targeting at once. VK2735, developed by Viking Therapeutics, is a dual GLP-1/GIP receptor agonist available in both subcutaneous and oral formulations. Retatrutide (LY3437943), from Eli Lilly, goes a step further as a balanced triple agonist engaging the GLP-1, GIP, and glucagon receptors simultaneously. Both compounds are unapproved and under active Phase 2–3 evaluation, but the data reported so far diverges sharply in magnitude, mechanism, and regulatory distance from a filing.
Research reference only. All information on this page is a summary of peer-reviewed scientific literature and does not constitute medical advice. See individual library profiles for full compound data.
Quick Answer: VK2735's Phase 2 VENTURE trial reported up to 14.7% mean weight loss at 13 weeks for the subcutaneous formulation, while retatrutide's Phase 3 TRIUMPH-1 topline data reported 28.3% mean weight loss at 80 weeks — the two trials differ enough in duration and phase that the numbers are not directly comparable, but retatrutide is substantially further along in Phase 3 development with an NDA submission anticipated, while VK2735's pivotal Phase 3 VANQUISH program is not expected to read out until 2027.
TL;DR:
- VK2735 is a dual GLP-1/GIP receptor agonist with both injectable and oral formulations in active trials; retatrutide is a triple GLP-1/GIP/glucagon receptor agonist, injectable only.
- Retatrutide's Phase 3 TRIUMPH program has already reported topline data (28.3% weight loss at 80 weeks in TRIUMPH-1); VK2735's Phase 3 VANQUISH-1 and VANQUISH-2 trials are still enrolled and not expected to read out until 2027.
- A preclinical mechanistic study (PMID 41997446) found that GIPR:GCGR co-agonism can correct obesity independent of GLP-1 receptor activity, informing why retatrutide's added glucagon-receptor component is mechanistically distinct from VK2735's GLP-1/GIP-only design.
- Neither compound has FDA approval; both remain investigational and are not eligible for 503A bulk compounding.
- VK2735's oral tablet formulation is a meaningful differentiator, since retatrutide has no oral program in the public trial registry.
VK2735: Mechanism and Evidence Base
VK2735 activates both the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor. Fatty-acid conjugation on the subcutaneous formulation is designed to extend the compound's half-life to support once-weekly dosing, while a separate oral tablet formulation relies on an absorption-enhancing excipient platform rather than the fatty-acid approach. Combining GLP-1 receptor agonism (appetite suppression, slowed gastric emptying) with GIP receptor engagement (glucose-dependent insulinotropic and adipocyte-modulating effects) places VK2735 mechanistically in the same class as tirzepatide, though the two are distinct molecules from different sponsors. Full chemistry and mechanism detail is available on the VK2735 library profile.
The evidence base to date comes from two completed Phase 2 trials and two ongoing Phase 3 trials. The Phase 2 VENTURE study, published in Obesity (2026, PMID 41508550), was a 13-week, randomized, double-blind, placebo-controlled trial in adults with obesity or overweight plus at least one weight-related comorbidity. Enrollment was expanded from 125 to 176 participants due to strong interest. All active dose groups produced statistically significant weight reduction versus placebo, with the highest dose reaching 14.7% mean weight loss from baseline at 13 weeks. Adverse events were primarily gastrointestinal and decreased in frequency with continued dosing — a pattern broadly consistent with other incretin-class agents, including tirzepatide.
A companion trial, VENTURE-Oral Dosing (NCT06828055), tested the once-daily oral tablet formulation over the same 13-week window. Topline results, presented at the European Congress on Obesity (ECO) 2026, reported up to 12.2% mean weight loss from baseline with a strong dose-response relationship — a notable finding because oral peptide delivery has historically underperformed injectable formulations in this class.
Viking initiated the Phase 3 VANQUISH program in mid-2025. VANQUISH-1 (NCT07104500) enrolled approximately 4,500 adults with obesity or overweight, completing enrollment in November 2025; it is a 78-week, randomized, double-blind, placebo-controlled trial with percent change in body weight as the primary endpoint. VANQUISH-2 (NCT07104383) enrolled approximately 1,000 adults with type 2 diabetes and obesity or overweight, completing enrollment in March 2026, with co-primary endpoints covering body weight and HbA1c change. Topline data for both trials is anticipated in 2027.
Retatrutide: Mechanism and Evidence Base
Retatrutide is a balanced unimolecular tri-agonist engaging the GLP-1 receptor, the GIP receptor, and the glucagon receptor (GCGR) simultaneously — one additional receptor target beyond VK2735's dual-agonist design. Preclinical mechanistic work (PMID 41997446) is particularly relevant to understanding why the third receptor matters: researchers demonstrated that obesity could be corrected in diet-induced obese mice through combined GIPR and GCGR agonism even in the complete absence of functional GLP-1 receptor signaling, using GLP-1R knockout mice as a model. Retatrutide, tested as a balanced triagonist in that same knockout model, normalized body weight despite the missing GLP-1 receptor pathway — evidence that the glucagon-receptor component contributes an independent, non-redundant mechanism rather than simply adding to GLP-1-driven effects. Full mechanism and chemistry data is available on the retatrutide library profile.
Retatrutide's human evidence base is now considerably further along than VK2735's. The Phase 3 TRIUMPH program includes several parallel trials. TRIUMPH-1, the pivotal master trial in adults with obesity or overweight (including comorbidity subsets for knee osteoarthritis and obstructive sleep apnea), reported topline results in May 2026: in 2,339 participants, the 12 mg dose produced a mean body weight reduction of 28.3% (average 70.3 lbs) over 80 weeks, with 45.3% of participants achieving at least 30% weight loss. A 104-week extension subgroup in participants with BMI ≥35 reached an average 30.3% loss. TRIUMPH-4, evaluating retatrutide in participants with obesity and knee osteoarthritis, reported a 28.7% mean body weight reduction alongside a 75.8% reduction in WOMAC pain scores, with more than 1 in 8 retatrutide-treated participants reporting complete freedom from knee pain at week 68. TRIUMPH-7, evaluating chronic low back pain in the same population, remains ongoing.
Retatrutide's diabetes-focused evidence is peer-reviewed and published: TRANSCEND-T2D-1, a 40-week Phase 3 trial across 48 sites in the United States, Mexico, and India, was published simultaneously in The Lancet and presented at the 2026 American Diabetes Association Scientific Sessions (PMID 42250575). Retatrutide reduced HbA1c by 1.69–1.94 percentage points across doses versus 0.81 points for placebo, with the 12 mg dose producing 16.8% mean weight loss and no apparent plateau by week 40. A head-to-head trial against semaglutide in type 2 diabetes, TRANSCEND-T2D-2, is ongoing. A large cardiovascular and kidney outcomes trial, TRIUMPH-Outcomes, is enrolling roughly 10,000 participants but is not expected to read out until 2028–2029 and is not required for the initial obesity indication. Eli Lilly has stated it plans to submit a New Drug Application based on the TRIUMPH program data.
Side-by-Side Comparison
| VK2735 | Retatrutide | |
|---|---|---|
| Receptor targets | GLP-1R, GIPR (dual agonist) | GLP-1R, GIPR, GCGR (triple agonist) |
| Sponsor | Viking Therapeutics | Eli Lilly |
| Formulations | Once-weekly subcutaneous; once-daily oral tablet | Once-weekly subcutaneous only |
| Furthest human trial phase | Phase 3 (VANQUISH-1/2, enrollment complete, data 2027) | Phase 3 (TRIUMPH-1/4 topline reported; TRANSCEND-T2D-1 published) |
| Reported weight loss (obesity trials) | Up to 14.7% at 13 weeks (subcutaneous, Phase 2); 12.2% at 13 weeks (oral, Phase 2) | 28.3% at 80 weeks (TRIUMPH-1, Phase 3 topline); 28.7% at 68 weeks with comorbidity (TRIUMPH-4) |
| Type 2 diabetes data | VANQUISH-2 ongoing, no results yet | TRANSCEND-T2D-1 published (Lancet, PMID 42250575); HbA1c −1.94% at 12 mg |
| Regulatory status | Investigational; no approval | Investigational; NDA submission planned |
Differential Research Applications
Researchers select between these two compounds based on the specific mechanistic question being asked. Studies isolating the marginal contribution of glucagon-receptor agonism to weight loss and glycemic effects have used retatrutide as the reference triagonist, since it is the most clinically advanced compound combining all three receptor targets in a single molecule. By contrast, researchers interested in oral peptide delivery as a variable — a persistent challenge in incretin pharmacology given first-pass metabolism and low bioavailability — have more reason to work with VK2735, given its active Phase 2 oral tablet program with no retatrutide equivalent currently in the public trial registry. Researchers tracking how each program's Phase 3 milestones compare over time can cross-reference active and completed trial records using the clinical trial tracker.
The knockout-mouse mechanistic work underlying retatrutide's triagonist rationale (PMID 41997446) also illustrates why receptor-count comparisons should not be treated as a simple "more is better" hierarchy: the study's core finding was that GIPR and GCGR co-agonism alone, without any GLP-1 receptor activity, was sufficient to correct obesity in the animal model — meaning the clinical relevance of each receptor's contribution needs to be evaluated per compound and per endpoint rather than assumed from the agonist count alone.
Regulatory and Compounding Status
Both compounds are investigational and neither holds FDA approval as of this writing. VK2735 has no regulatory filings reported; both VANQUISH Phase 3 trials remain in progress with data anticipated in 2027, and any approval timeline would follow that readout. Retatrutide is further along procedurally — Eli Lilly has stated its intent to submit a New Drug Application based on the completed TRIUMPH programme data — but as of this writing no NDA has been approved and retatrutide remains investigational. Neither compound is eligible for 503A bulk drug substance compounding while investigational status persists; that status is distinct from the compounds discussed in the FDA's ongoing PCAC review process for a separate set of research peptides.
Cited Studies
- PMID 41508550 — "Weekly Subcutaneous VK2735, a GIP/GLP-1 Receptor Dual Agonist, for Weight Management: Phase 2, Randomized, 13-Week VENTURE Study." (Obesity, 2026). https://doi.org/10.1002/oby.70106
- PMID 41997446 — "GIPR:GCGR co-agonism restores normal weight in obese rodents." (2026).
- PMID 42250575 — "Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial." (The Lancet, 2026).
- NCT07104500 — VANQUISH-1, Phase 3 trial of VK2735 in obesity/overweight, ClinicalTrials.gov.
- NCT07104383 — VANQUISH-2, Phase 3 trial of VK2735 in type 2 diabetes with obesity/overweight, ClinicalTrials.gov.
Frequently asked questions
Q: What is the main mechanistic difference between VK2735 and retatrutide?
A: VK2735 is a dual agonist activating the GLP-1 and GIP receptors, while retatrutide is a triple agonist that adds glucagon receptor activity on top of the same two targets. Preclinical research (PMID 41997446) indicates the glucagon-receptor component contributes weight-correcting effects independent of GLP-1 receptor signaling, rather than simply amplifying it.
Q: Which compound has stronger clinical trial data so far?
A: Retatrutide's Phase 3 TRIUMPH program has reported topline data showing 28.3% mean weight loss at 80 weeks, and its diabetes-focused TRANSCEND-T2D-1 trial is already published in The Lancet. VK2735's furthest data is from 13-week Phase 2 trials; its Phase 3 VANQUISH program has completed enrollment but has not yet reported results, expected in 2027.
Q: Does VK2735 or retatrutide have an oral formulation?
A: VK2735 has an oral tablet formulation in an active Phase 2 program (VENTURE-Oral Dosing), which reported up to 12.2% weight loss at 13 weeks. Retatrutide does not currently have a public oral formulation trial; its Phase 3 program is subcutaneous-injectable only.
Q: Is VK2735 or retatrutide FDA approved?
A: Neither compound is FDA approved as of this writing. Both remain investigational. Retatrutide is procedurally closer to a regulatory filing, with Eli Lilly stating its intent to submit a New Drug Application based on TRIUMPH programme data, while VK2735's pivotal Phase 3 trials are not expected to read out until 2027.
Q: Can VK2735 or retatrutide be obtained through 503A compounding pharmacies?
A: No. Both compounds are investigational new drugs without FDA approval, which places them outside the scope of standard 503A bulk drug substance compounding intended for approved or historically compounded substances. Their regulatory pathway is separate from the FDA's PCAC review process governing a different set of already-marketed research peptides.
See also:
- Retatrutide vs Tirzepatide: Triple vs Dual Agonist Mechanism Comparison — compares retatrutide's triagonist design against tirzepatide's established dual-agonist mechanism.
- Next-Generation GLP-1/Incretin Pipeline 2026 — situates VK2735 and retatrutide among the broader field of investigational incretin compounds.
- Survodutide vs Tirzepatide: GLP-1/Glucagon vs GLP-1/GIP Dual Agonism — a related comparison of a different dual-receptor combination strategy.
For laboratory research purposes only. Not for human or animal consumption. Compounds described are not approved by the FDA for human or veterinary use unless explicitly stated.