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Key Takeaways
- The Phase 2 trial (Jastreboff et al., NEJM 2023, n=338) showed mean body weight reduction of roughly 24.2% at 48 weeks on the 12 mg weekly dose, the highest published figure for any injectable weight-loss agent in a controlled trial at that sample size and timepoint.
- Retatrutide targets three receptors simultaneously: GLP-1, GIP, and glucagon. No other approved or late-stage obesity drug shares this triple mechanism as of 2026.
- ClinicalTrials.gov using the search term "retatrutide" and a zip-code proximity filter is the only verified way to find legitimate trials near you. Sponsor is Eli Lilly (LY3437943).
- Common adverse events in Phase 2 included nausea (affecting a substantial proportion of active-arm participants), vomiting, diarrhea, and constipation. These were mostly mild to moderate and followed dose-escalation schedules.
- Compounded retatrutide is not the Phase 2 compound. It has no independent safety or efficacy data, no FDA oversight, and unknown purity. A clinical trial is categorically different from a compounding pharmacy purchase.
Direct Answer: How Do I Find Retatrutide Peptide Clinical Trials Near Me?
Go to ClinicalTrials.gov, type "retatrutide" in the condition or drug field, and filter by your country and distance from your zip code. All active Phase 3 trials are sponsored by Eli Lilly under the compound identifier LY3437943. Academic obesity centers affiliated with major medical schools often receive enrollment slots before the public registry updates, so a direct call to those centers is a legitimate parallel step.
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- What Is Retatrutide? Mechanism With Specific Numbers
- Evidence Ledger: What the Data Actually Show
- How to Find and Verify a Trial Site Near You
- Eligibility: Who Qualifies and Who Is Excluded
- What Most Pages Get Wrong About Retatrutide Trials
- Honest Head-to-Head: Retatrutide vs. Tirzepatide vs. Semaglutide
- Chemistry Behind the Rules: Why This Triple Agonist Is Different
- Operational Guide: What Trial Participation Actually Looks Like
- Compounded Retatrutide: The Sourcing Reality
- FDA Timeline and What Comes After Phase 3
- FAQ
What Is Retatrutide? Mechanism With Specific Numbers
Retatrutide (LY3437943) is a single synthetic peptide that acts as an agonist at three G-protein-coupled receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR). It is a once-weekly subcutaneous injection in trials, using a fatty-acid linker to extend its plasma half-life to roughly a week, similar to the approach used for semaglutide.
The Phase 2 dose-escalation protocol tested doses of 1 mg, 4 mg, 8 mg, and 12 mg weekly. The dose-response relationship was clear: the 4 mg group lost a mean of roughly 8.7% of body weight at 24 weeks, the 8 mg group roughly 17.3%, and the 12 mg group roughly 22.8% at the same timepoint (Jastreboff et al., NEJM 2023). At 48 weeks, the highest dose arm reached approximately 24.2% mean weight loss versus approximately 2.1% in placebo.
What this mechanism does NOT prove: Greater receptor count does not automatically mean better long-term outcomes or better tolerability. The glucagon receptor component raises theoretical concerns about glucagon-driven hepatic glucose production, though this appeared to be offset by the GLP-1 and GIP components in the trial. Long-term cardiovascular outcome data do not yet exist for retatrutide.
Evidence Ledger: What the Data Actually Show
| Claim | Best Evidence Type | Source | Effect Direction | Confidence |
|---|---|---|---|---|
| ~24% body weight loss at 48 weeks (12 mg) | Phase 2 RCT (n=338) | Jastreboff et al., NEJM 2023 | Strong reduction | Moderate (single Phase 2 trial; Phase 3 pending) |
| Nausea, vomiting, diarrhea as common adverse events | Phase 2 RCT safety data | Jastreboff et al., NEJM 2023 | Dose-dependent increase | Moderate |
| Improvement in fasting glucose and insulin resistance | Phase 2 RCT secondary endpoints | Jastreboff et al., NEJM 2023 | Favorable | Moderate |
| Reduction in hepatic fat (MASLD/NAFLD) | Phase 2 substudy data | Lilly-sponsored substudy, 2023-2024 | Favorable signal | Low (small subsample, not primary endpoint) |
| Superior weight loss vs. tirzepatide or semaglutide head-to-head | No direct RCT head-to-head | None published as of 2026 | Unknown | Very Low (cross-trial comparison only) |
| Long-term cardiovascular safety | No dedicated CVOT yet | None published as of 2026 | Unknown | Very Low |
| Thyroid C-cell risk in humans | Animal data (rodent); human signal unclear | Class-level concern; no human RCT signal reported | Theoretical concern | Very Low for humans |
How to Find and Verify a Trial Site Near You
Follow this exact sequence to avoid scam sites and outdated listings:
- Go to ClinicalTrials.gov. In the search bar, enter "retatrutide." Under "Status," select "Recruiting" or "Not yet recruiting." Under "Location," enter your city, state, or zip code and choose a mile radius (25, 50, or 100 miles).
- Note the NCT number for each listing that appears. NCT numbers are permanent identifiers. If a website or clinic claims to be running a retatrutide trial but cannot provide an NCT number, treat that as a red flag.
- Confirm the sponsor is Eli Lilly. Retatrutide has not been licensed to other companies for Phase 3 trials as of mid-2026. Any site claiming to run an independent retatrutide trial is not running the same compound.
- Call the site coordinator directly using the phone number listed on ClinicalTrials.gov, not a number found on a third-party recruitment site.
- Check for IRB approval documentation. Every legitimate site will reference its Institutional Review Board approval in the consent form. You are entitled to see this before signing anything.
Eligibility: Who Qualifies and Who Is Excluded
Based on the Phase 2 protocol and the general design of Lilly's Phase 3 program, typical criteria include:
Inclusion (likely): Age 18 to 75. BMI 30 or above, or BMI 27 or above with at least one weight-related comorbidity (hypertension, dyslipidemia, type 2 diabetes, obstructive sleep apnea, or cardiovascular disease). Stable body weight in the 90 days before screening.
Exclusion (common): Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. Current or recent use of GLP-1 receptor agonists, GIPR agonists, or other weight-loss medications. Recent major cardiovascular event (typically within 90 days). Severe renal impairment. Active malignancy. Pregnancy or planned pregnancy.
Each Phase 3 protocol may differ. The ClinicalTrials.gov listing for each NCT number includes the complete inclusion and exclusion criteria. Read these before attending a screening visit.
What Most Pages Get Wrong About Retatrutide Trials
The "near me" clinic problem. A number of medspas and wellness clinics advertise retatrutide under language like "retatrutide peptide clinical trials near me" or "access the trial compound." These are not clinical trials. They are selling compounded or research-chemical versions of a peptide that resembles retatrutide. Participation in these does not contribute to Phase 3 data, does not give you regulatory oversight, and does not offer the safety monitoring that a genuine Lilly-sponsored trial provides.
The approval timeline problem. Several sites state retatrutide "could be approved by 2025." As of mid-2026, it is not approved. Phase 3 data readouts and NDA submission timelines have not been publicly confirmed by Lilly at the time of writing. Be skeptical of specific approval dates from non-regulatory sources.
Honest Head-to-Head: Retatrutide vs. Tirzepatide vs. Semaglutide
| Attribute | Retatrutide | Tirzepatide (Zepbound) | Semaglutide (Wegovy) |
|---|---|---|---|
| Receptor targets | GLP-1, GIP, Glucagon (triple) | GLP-1, GIP (dual) | GLP-1 only |
| FDA approval for obesity | No (Phase 3 as of 2026) | Yes (2023) | Yes (2021) |
| Best Phase 3/pivotal trial weight loss | ~24% (Phase 2 only, 48 wk) | ~22.5% (SURMOUNT-1, 72 wk) | ~15% (STEP 1, 68 wk) |
| Cardiovascular outcome trial | Not yet | SURMOUNT-MMO ongoing | SELECT trial positive (2023) |
| Real-world supply availability | Trial participants only | Available, some shortage history | Available, past shortage history |
| Long-term safety data | Very limited (48 wk max) | Moderate (72 wk pivotal + post-market) | Most robust (6+ years post-market) |
| Where retatrutide loses | No approval, no CVOT, no real-world data, no compounding legitimacy | No long-term CVOT completion yet | Lower weight loss magnitude |
Cross-trial weight loss figures are not directly comparable. See "What Most Pages Get Wrong" above.
Chemistry Behind the Rules: Why a Triple Agonist Is Structurally Different
GLP-1 receptor agonism drives the satiety signal and slows gastric emptying. GIP receptor agonism enhances insulin secretion in a glucose-dependent manner and may modulate adipocyte metabolism. Glucagon receptor agonism, when added to these two, drives increased hepatic glucose output and raises basal metabolic rate via thermogenesis. In isolation, glucagon agonism would worsen glycemia. The reason retatrutide does not appear to worsen glucose control in trials is that the GLP-1 and GIP components suppress glucose levels sufficiently to counteract glucagon's hepatic glucose output. This balance is what the triple-agonist design is built around.
The fatty-acid linker attached to the peptide backbone enables albumin binding in plasma, which substantially slows renal clearance and extends the half-life to approximately one week, enabling once-weekly dosing. This is the same pharmacokinetic strategy used by semaglutide (a C18 fatty-diacid linker) and tirzepatide (a C20 fatty-diacid linker). The specific linker chemistry for LY3437943 has been described in Lilly's patent filings but full binding kinetics data at the receptor level have not been published in peer-reviewed form as of mid-2026.
Stability gotcha: Like all GLP-1 class peptides with fatty-acid linkers, retatrutide is likely susceptible to degradation from temperature excursion, light exposure, and repeated freeze-thaw cycles. In trials, study drug is stored and handled under controlled pharmacy conditions. Compounded versions sold outside of trial context have no verified cold-chain documentation, which is a direct patient safety concern beyond the purity question.
Operational Guide: What Trial Participation Actually Looks Like
Screening (2 to 4 weeks): Blood work (CBC, metabolic panel, HbA1c, thyroid panel), physical exam, vital signs, possibly an EKG and medical history review. You may be screened and then not qualify based on lab results.
Dose escalation (weeks 1 to 16 approximately): Trials typically start at a low dose and escalate every four weeks. This is not optional. Skipping escalation to reach a higher dose faster is a protocol violation and grounds for discontinuation.
Maintenance phase: Once at the target dose, monthly or bi-monthly site visits for weight, vital signs, adverse event review, and blood draws.
What you receive at no cost: Study drug, protocol-required visits, protocol-required laboratory tests. Some trials reimburse travel. You do not pay for the drug or visits. Any site charging you is not a legitimate Lilly-sponsored trial.
Withdrawal: You can withdraw consent at any time without penalty. You will likely have a follow-up safety visit 30 days after your last dose.
Compounded Retatrutide: The Sourcing Reality
Retatrutide is not FDA-approved. It is not on the FDA's list of bulk drug substances approved for compounding. Compounding pharmacies do not have the legal or regulatory basis to compound retatrutide for clinical use under the same frameworks that briefly permitted compounded semaglutide and tirzepatide during shortage periods. Compounded retatrutide purchased from a pharmacy, wellness clinic, or research chemical supplier:
- Has not been tested in humans in that formulation
- Has no independently verified purity, potency, or sterility data
- Is not subject to the safety monitoring required in an IND-authorized trial
- Is not the compound that generated the NEJM 2023 data
This does not mean every batch is dangerous, but it means you have no way to know whether any individual batch is safe or effective. The risk is not theoretical; it is the fundamental problem of unverifiable manufacturing outside of Good Manufacturing Practice oversight.
FDA Timeline and What Comes After Phase 3
Eli Lilly has not publicly confirmed an NDA submission date as of mid-2026. Phase 3 trials are ongoing. After Phase 3 data are collected and analyzed, Lilly must submit an NDA, the FDA has 60 days to accept the filing, then typically 10 to 12 months to complete the review under standard review (or 6 months under Priority Review if granted). Based on publicly available Phase 3 start dates and standard timelines, earliest plausible commercial availability would be 2027 to 2028, but this is projection. Do not rely on analyst estimates as regulatory fact.
After approval, retatrutide would require a REMS program (Risk Evaluation and Mitigation Strategy) given the thyroid C-cell class concern shared by all GLP-1 agonists. Prescribers would need to counsel patients and document that counseling, as is required today for semaglutide and tirzepatide.
FAQ
How do I find retatrutide peptide clinical trials near me?
Search ClinicalTrials.gov using the term "retatrutide" and filter by your country and zip code radius. Eli Lilly is the sponsor for all active Phase 3 trials under protocol identifiers beginning with LY3437943. You can also contact major academic obesity centers directly, as they often have open slots before ClinicalTrials.gov updates.
What phase are retatrutide trials currently in?
As of mid-2026, retatrutide (LY3437943) is in Phase 3 trials for obesity and type 2 diabetes. Phase 2 data published in The New England Journal of Medicine in 2023 established the efficacy and dose-response profile that Phase 3 is built on.
What weight loss did Phase 2 trials show for retatrutide?
In the 48-week Phase 2 trial (Jastreboff et al., NEJM 2023), participants on the highest dose (12 mg weekly) lost a mean of approximately 24.2% of body weight. This was in adults with obesity and without diabetes. The placebo group lost about 2.1%.
Who is eligible for retatrutide clinical trials?
Typical inclusion criteria include a BMI of 30 or above, or 27 or above with a weight-related comorbidity. Exclusion criteria commonly include a personal or family history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, recent cardiovascular events, and current use of other GLP-1 or GIP receptor agonists.
What is retatrutide and how does it differ from tirzepatide?
Retatrutide is a triple agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Tirzepatide is a dual GLP-1 and GIP agonist. The addition of glucagon receptor agonism in retatrutide is hypothesized to increase energy expenditure and hepatic fat reduction beyond what dual agonism alone achieves.
Are there risks to joining a retatrutide clinical trial?
Yes. Phase 2 adverse events included nausea, vomiting, diarrhea, and constipation, consistent with GLP-1 class effects. A small number of participants had elevated heart rate. Preclinical rodent data showed thyroid C-cell changes (a class concern shared by all GLP-1 agonists), and longer-term human safety data are still accumulating in Phase 3.
Do clinical trial participants receive retatrutide for free?
In most industry-sponsored trials, the study drug, study visits, and protocol-required lab work are provided at no cost. Some trials also offer travel reimbursement. You should never pay to join a legitimate clinical trial, and any site asking for payment is a red flag.
Can I use a compounded retatrutide peptide instead of a trial?
Retatrutide is not FDA-approved and compounded versions carry unknown purity, potency, and sterility risk. Compounded retatrutide is not the same compound evaluated in Lilly trials and has no safety or efficacy data of its own. A legitimate clinical trial is the only context in which retatrutide use is backed by regulatory oversight.
How long do retatrutide clinical trials last?
Phase 3 obesity trials typically run 72 weeks of treatment plus a follow-up period, mirroring the design used for semaglutide and tirzepatide outcomes trials. Expect a total commitment of roughly 18 to 24 months including screening, treatment, and post-treatment follow-up visits.
What is the expected FDA approval timeline for retatrutide?
Eli Lilly has not publicly confirmed an NDA submission date as of mid-2026. Analysts have cited a possible submission in 2026 to 2027 pending Phase 3 readout, but this is projection, not confirmed regulatory timeline. FDA approval timelines for novel drugs average 12 months after NDA acceptance.
How do I verify a retatrutide trial site is legitimate?
Cross-reference the site on ClinicalTrials.gov using the NCT number. Legitimate sites are IRB-approved, listed under the Eli Lilly sponsor record, and will provide a written informed consent document before any procedures. Never provide payment or share financial information to enroll.
Sources
- Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. New England Journal of Medicine. 2023;389(6):514-526.
- Frías JP, Dahl D, Fukumoto K, 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 conducted in the USA. The Lancet. 2023;402(10401):529-544.
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine. 2021;384(11):989-1002.
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine. 2022;387(3):205-216.
- Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). New England Journal of Medicine. 2023;389(24):2221-2232.
- U.S. National Library of Medicine. ClinicalTrials.gov. Search: "retatrutide." Available at: https://clinicaltrials.gov
- U.S. Food and Drug Administration. Compounding and the FDA: Questions and Answers. FDA.gov. Accessed 2026.
- U.S. Food and Drug Administration. Guidance for Industry: Expedited Programs for Serious Conditions. FDA.gov.