Retatrutide vs Tirzepatide: Not a Head-to-Head Yet — Only Tirzepatide Is Approved

As of 26 August 2026, only tirzepatide is FDA-approved — as Mounjaro and as Zepbound. Retatrutide is not approved and is not for sale (Eli Lilly, 23 July 2026 and 12 August 2026).

Lilly’s published TRIUMPH Phase 3 weight-change numbers are from placebo-controlled trials. They are not a head-to-head versus tirzepatide. The dedicated comparison, TRIUMPH-5 (NCT06662383), has not reported.

Status as of 26 August 2026

This is not a head-to-head

A head-to-head trial randomizes the same population to both drugs under one protocol. TRIUMPH-1, TRIUMPH-2, TRIUMPH-3, and TRIUMPH-4 compared retatrutide with placebo, not with tirzepatide.

Lilly reports a primary efficacy estimand (effect if participants stayed on study drug without starting prohibited weight-management treatments) and, for some trials, a treatment-regimen estimand (effect regardless of discontinuation). Efficacy-estimand percentages are higher. Those figures still are not versus tirzepatide. This page does not turn them into a ranking against Zepbound or Mounjaro.

Phase 3 numbers (efficacy estimand, not versus tirzepatide)

The figures below are Lilly’s efficacy estimand unless labeled otherwise. They are placebo-controlled TRIUMPH results. They are not versus tirzepatide.

• TRIUMPH-4 — 11 December 2025. Adults with obesity or overweight and knee osteoarthritis. n=445. At 68 weeks, 12 mg −28.7%. Source: Lilly, 11 Dec 2025.
• TRIUMPH-1 — 21 May 2026. Obesity without type 2 diabetes. n=2,339. At 80 weeks, 12 mg −28.3%; treatment-regimen −25.0%. Source: Lilly, 21 May 2026.
• TRIUMPH-2 — 23 July 2026. Obesity or overweight plus type 2 diabetes. At 80 weeks, 12 mg −20.8%. Source: Lilly, 23 Jul 2026.
• TRIUMPH-3 — 23 July 2026. Severe obesity and established cardiovascular disease. 12 mg −22.6%. Source: Lilly, 23 Jul 2026.

The leftover −24.2% at 48 weeks is Phase 2 (Jastreboff et al., New England Journal of Medicine, 2023). It is not a Phase 3 TRIUMPH result and it is not versus Zepbound.

Tirzepatide is the prescribe-today medicine

Tirzepatide is FDA-approved. Lilly’s Mounjaro (tirzepatide) was approved on 13 May 2022. Lilly’s Zepbound (tirzepatide) was approved for chronic weight management on 8 November 2023. Current Lilly label language includes OSA. A licensed clinician has to decide whether any of that is appropriate for you.

Retatrutide is a different investigational molecule. It has no brand name. It is not Mounjaro and not Zepbound. A Q1 2027 BLA filing plan is not a prescription you can fill in 2026.

Lilly’s oral GLP-1 Foundayo (orforglipron) received FDA approval on 1 April 2026. That is an educational status note, not a partner offer on this page.

Mechanism is a description, not a scoreboard

Tirzepatide is a dual agonist: it activates GIP and GLP-1 receptors. Retatrutide is a triple agonist: it activates GIP, GLP-1, and glucagon receptors. That is how the two molecules are described. It is not a published ranking of weight-loss outcomes. Extra receptors are not a substitute for a head-to-head trial.

TRIUMPH-5 has not reported

TRIUMPH-5 (NCT06662383) is the Phase 3 trial designed as a comparison that includes tirzepatide. It has not reported. ClinicalTrials.gov lists a primary completion in November 2026; that date can slip. A registry date is not a news day, not a result, and not a reason to treat placebo-controlled TRIUMPH percentages as a Zepbound comparison. Source: ClinicalTrials.gov NCT06662383.

What you can do now

Affiliate disclosure: NextGenGLP1 may earn a commission if you use the partner links below, at no cost to you. Neither partner sells retatrutide. Compounded medication is not FDA-approved. A prescription is issued only after a medical consultation. Pricing is on the partner sites and can change; this page does not quote it.

1. Talk with a licensed clinician about FDA-approved options that exist today, including tirzepatide, if weight-management care is appropriate for you.
2. TrimRX (primary partner) offers a compounded GLP-1 + GIP option through a telehealth consult. That is not Zepbound, not Mounjaro, and not retatrutide. Compounded medication is not FDA-approved. A medical consultation is required. This page does not quote a price. See if you qualify with TrimRX.
3. Medvi (secondary partner) offers licensed semaglutide and tirzepatide with a medical consultation. This page does not call Medvi compounded. See Medvi.
4. Join this site’s email list if you want a note when Lilly files or if FDA acts. The NextGenGLP1 waitlist is not a Lilly program.
5. Do not buy retatrutide, “research peptides,” or compounded retatrutide. See Can you buy retatrutide?

Safety (one paragraph)

Incretin trials commonly report gastrointestinal effects such as nausea, diarrhea, vomiting, and constipation. In TRIUMPH-4, Lilly reported dysesthesia in 20.9% of participants on 12 mg versus 0.7% on placebo. That is a retatrutide trial finding versus placebo, not a published comparison with tirzepatide, and it is not a complete safety list. Read the retatrutide side-effects and safety guide and talk with a clinician.

What this page will not say

• It will not rank retatrutide as the weight-loss winner against tirzepatide, Zepbound, or Mounjaro.
• It will not treat leftover Phase 2 percentages, or a separate tirzepatide trial, as a published head-to-head.
• It will not invent a retatrutide list price.
• It will not assign a 2027 or 2028 approval year. Q1 2027 is Lilly’s BLA filing plan. There is no PDUFA date.
• It will not treat TRIUMPH-5’s ClinicalTrials.gov primary-completion date as a result.

Sources

• Lilly, Mounjaro FDA approval, 13 May 2022
• Lilly, Zepbound FDA approval for chronic weight management, 8 November 2023
• Lilly TRIUMPH-4 topline, 11 December 2025
• Lilly TRIUMPH-1 topline, 21 May 2026
• Lilly TRIUMPH-2 / TRIUMPH-3 and Q1 2027 BLA, 23 July 2026
• Lilly, 12 August 2026 (retatrutide not approved; illegal market)
• Lilly, Foundayo (orforglipron) FDA approval, 1 April 2026
• Jastreboff et al., Phase 2, N Engl J Med 2023 (−24.2% at 48 weeks)
• TRIUMPH-5, NCT06662383
• Retatrutide FDA approval status 2026: not approved
• Can you buy retatrutide?
• Retatrutide cost: no list price