Retatrutide vs tirzepatide: trials and access

Sources checked October 26, 2026. This is a comparison of documents and study measurements, not a recommendation, safety assessment or dosing guide.

Are retatrutide and tirzepatide the same thing?

They have different receptor-target descriptions. Lilly describes retatrutide as a single molecule with three targets, not three medicines mixed together.[2] Zepbound's August 2026 prescribing information describes tirzepatide as a GIP and GLP-1 receptor agonist.[1]

A receptor count identifies the molecule's pharmacology. This page does not use that count to rank either medicine or predict an individual's response.

For the broader research history, see our retatrutide study guide. Here, the comparison separates the product label, two placebo-controlled studies and the registry for the direct comparison.

What are the other names for each medicine?

Retatrutide carries the Lilly research code LY3437943 and is often called a triple agonist or triple hormone receptor agonist.[7] Tirzepatide is a dual GIP and GLP-1 receptor agonist, marketed in the US as Zepbound for weight management and as Mounjaro for type 2 diabetes. Both belong to the wider incretin medicine family that also includes semaglutide, compared in our semaglutide and tirzepatide breakdown.

How do retatrutide and tirzepatide compare at a glance?

The two medicines differ in receptor targets, regulatory status and the routes a patient can use to receive them. The table restates attributes already documented in the sources below, so each row can be checked against its reference.

What do the separate weight-loss trials actually compare?

TRIUMPH-1 and SURMOUNT-1 each randomized participants against placebo, not against the other molecule.[5][6] The table preserves their different populations and follow-up periods; it is not a head-to-head result.[5][6]

The milligram amounts identify published research arms only. They are not starting doses, a switching schedule or a conversion between the medicines.

An earlier phase 2 retatrutide trial by Jastreboff and colleagues, published in NEJM in 2023, enrolled 338 adults and reported a least-squares mean weight change of -24.2% at 48 weeks in the 12-mg group, against -2.1% with placebo.[7] The same report described gastrointestinal adverse events as the most common in the retatrutide groups, and dose-related.[7] For tirzepatide outside the trial setting, our tirzepatide weight loss overview covers the prescription product.

Why is 25.0% versus 20.9% not a head-to-head answer?

Those percentages come from separate randomized populations, different follow-up lengths and separate placebo groups.[5][6] Subtracting them would not produce an observed randomized retatrutide-versus-tirzepatide treatment difference.

Both reports identify a treatment-regimen analysis for these weight endpoints.[5][6] SURMOUNT-1 describes that analysis as assessing outcomes regardless of treatment discontinuation in the intention-to-treat population.[6]

An estimand specifies the question an analysis addresses. Retain the study, analysis definition, comparator and time point whenever you copy a percentage. The figures here are group means, not forecasts for an individual. We reviewed the original author abstracts, not the complete papers.

Is there a direct retatrutide versus tirzepatide trial?

Yes. ClinicalTrials.gov identifies TRIUMPH-5 as NCT06662383, a randomized, double-blind phase 3 comparison in adults with obesity.[3] Its primary outcome is percentage change in body weight from baseline to week 80.[3]

The record retrieved October 26, 2026 was last updated July 20, 2026 and listed active, not recruiting status, estimated enrollment of 800, estimated primary completion in November 2026 and estimated study completion in December 2026.[3]

That retrieved record contained no posted results.[3] Estimated enrollment and completion dates are plans, not completed outcome data. This registry observation is narrower than claiming that no results exist anywhere.

What is NCT07629401?

NCT07629401 is the ClinicalTrials.gov identifier for "Pre-approval Expanded Access of Retatrutide (LY3437943)," a program sponsored by Eli Lilly and Company with the Lilly study code J1I-MC-Y001.[4] The record was first posted June 5, 2026, last updated August 6, 2026, and lists its status as available.[4] It is an expanded-access record, not a randomized trial, so it has no comparison arm and no planned efficacy results.

Who is eligible for retatrutide expanded access under NCT07629401?

The record lists every one of these criteria as required:[4]

• Age 18 years or older.
• Refractory obesity, defined as a BMI of 35 kg/m² or higher despite adherence to and tolerance of the highest available dose of a chronic weight management therapy.
• Two or more serious or life-threatening obesity-related complications that are currently receiving standard care.
• Inability to join an ongoing retatrutide trial or a comparable investigational trial, because of trial eligibility rules or no reasonably accessible enrolling site.
• A shared decision-making discussion of all standard options, including bariatric surgery.

A medical contraindication to retatrutide excludes a patient.[4] In practice, the criteria describe people for whom approved therapy such as tirzepatide has already been tried at its highest available dose.

How is an NCT07629401 request made?

The treating physician starts the request with Lilly on the patient's behalf, and the record directs patients and caregivers to their own physician rather than to Lilly.[4] Availability depends on geography, product supply and a detailed individual eligibility assessment.[4] The usual clinicians involved are obesity medicine physicians, endocrinologists and primary care doctors who already manage the patient's weight-related conditions.

Can retatrutide be prescribed like Zepbound?

The documents describe different access situations. Zepbound has US prescribing information; the version checked here was revised August 2026.[1] Lilly's September 29, 2026 announcement calls retatrutide investigational and gives a planned FDA application window of the first quarter of 2027, not an approval or launch date.[2]

ClinicalTrials.gov separately lists a pre-approval, single-patient expanded-access program for retatrutide, NCT07629401. Its August 6, 2026 update describes requests initiated by a treating physician and availability dependent on geography, supply and individual eligibility assessment.[4]

That access program is separate from TRIUMPH-5 enrollment.[3][4] A broad peptide-service listing does not establish participation in either route, nor does it confirm that a clinic prescribes a specific branded product.

Products sold online as "research peptide" retatrutide sit outside both documented routes, because neither the label nor the expanded-access record describes them. Compounded tirzepatide is a separate question again, covered in our compounded tirzepatide guide, which explains how pharmacy-made versions differ from the labeled product.

What should you ask a provider about this comparison?

Ask for the exact medicine and product name under discussion, then ask which document describes the proposed access route. Separate a prescription-product discussion from trial enrollment or a physician-initiated expanded-access request.

If a weight-change percentage is quoted, request the study name, participant population, follow-up time and analysis definition. Ask whether it is a direct comparison or a result from a different placebo-controlled trial.

Bring questions about personal suitability, adverse effects and any proposed change in treatment to the prescribing clinician. This page does not answer those individualized questions, compare safety or supply a switching protocol.

1. Which product is being proposed, and is it the labeled medicine, a compounded preparation or an investigational drug?
2. Which document supports the access route: a prescribing label, a trial registry entry such as NCT06662383, or the expanded-access record NCT07629401?
3. If expanded access is discussed, which of the NCT07629401 eligibility criteria do I meet, and who will submit the request?
4. How will side effects, lab work and weight-related conditions be monitored, and by which clinician?

Where can you compare Peptide Therapy clinics?

Regenerated.com's September 2026 export of 9,042 published US clinic records contains 2,743 records listing Peptide Therapy, across 49 states plus Washington, DC. Source: the September clinic export, counted in the directory-facts snapshot generated October 17, 2026. This is directory coverage, not a count of retatrutide providers, tirzepatide prescribers or trial sites.

Browse the Peptide Therapy clinic directory for recorded services and locations. For state-level browsing, compare Peptide Therapy clinics in Iowa, Peptide Therapy clinics in Kansas or Peptide Therapy clinics in Maine. Live inventory can differ from the dated export.

Two profiles currently listing the broad Peptide Therapy category are IV Theory in Boca Raton, Florida and Perfect Balance Health in San Diego, California. They are navigation examples, not a ranking or confirmation of access to either molecule. A listing is not an endorsement.

Listing order in the directory is not paid ranking, Featured slots are labeled and capped, and Verified means the clinic completed credential checks rather than paid for placement, as the guide to Featured, Verified and organic listings explains. Regenerated.com is free for patients. Before a visit, use the nationwide list of peptide therapy providers to confirm each clinic's stated services directly.

Frequently asked questions

Does retatrutide have an extra receptor target?

Yes. Lilly describes retatrutide as targeting GIP, GLP-1 and glucagon receptors, while Zepbound's label describes tirzepatide as targeting GIP and GLP-1.[1][2] The extra target is the glucagon receptor, which is why retatrutide is called a triple agonist and tirzepatide a dual agonist. This identifies pharmacology, not a clinical ranking, and it does not predict how any one person will respond to either medicine.

Has TRIUMPH-5 posted comparison results?

No results were posted in the ClinicalTrials.gov record for TRIUMPH-5, NCT06662383, retrieved October 26, 2026, and the record still carried estimated completion dates of November 2026 for the primary outcome and December 2026 for the study.[3] TRIUMPH-5 is the randomized, double-blind phase 3 trial that compares retatrutide directly with tirzepatide. That observation describes the retrieved registry record, not every possible publication.

Is retatrutide access limited to trial enrollment?

No. A separate pre-approval expanded-access record, NCT07629401, describes single-patient requests initiated by a treating physician, subject to eligibility, geography and supply.[4] Its criteria require adults with a BMI of 35 or higher, at least two serious obesity-related complications and an inadequate response to the highest available dose of approved weight therapy. It does not establish access for every reader, and retatrutide has no US prescription label.

Does a Peptide Therapy listing mean a clinic offers retatrutide?

No. Peptide Therapy is a broad directory category that covers many products, and a listing does not identify a TRIUMPH-5 trial site or establish expanded-access eligibility under NCT07629401. Confirm the exact product and the documented access route with the provider before booking. Retatrutide outside a trial or expanded access is not described by any document cited on this page, and inclusion in the directory is not an endorsement.

Is NCT07629401 a clinical trial for retatrutide?

NCT07629401 is an expanded-access program, not a clinical trial. Eli Lilly and Company registered it on ClinicalTrials.gov to provide pre-approval, single-patient access to retatrutide for adults with severe, refractory obesity who cannot join a retatrutide study.[4] Because it has no randomized comparison, it will not produce efficacy results. Treating physicians, not patients, start each request with Lilly.

Is retatrutide stronger than tirzepatide for weight loss?

The cited records do not answer that yet, because the head-to-head trial TRIUMPH-5 had no posted results in the record retrieved October 26, 2026.[3] Separate placebo-controlled trials reported -25.0% at 80 weeks with 12 mg retatrutide in TRIUMPH-1 and -20.9% at 72 weeks with 15 mg tirzepatide in SURMOUNT-1.[5][6] Different populations and follow-up lengths make those figures unsuitable for ranking.

Sources

1. DailyMed: Lilly Zepbound prescribing information. Checked October 26, 2026.
2. Eli Lilly: retatrutide development announcement, September 29, 2026. Checked October 26, 2026.
3. ClinicalTrials.gov: TRIUMPH-5, NCT06662383. Checked October 26, 2026.
4. ClinicalTrials.gov: retatrutide pre-approval expanded access, NCT07629401. Checked October 26, 2026; eligibility criteria rechecked November 5, 2026.
5. Jastreboff et al., NEJM: TRIUMPH-1, September 29, 2026. Checked October 26, 2026.
6. Jastreboff et al., NEJM: SURMOUNT-1, June 4, 2022. Checked October 26, 2026.
7. Jastreboff et al., NEJM: Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial, 2023. Checked November 5, 2026.