The short answer
Retatrutide's clinical timeline began with Phase 1 first-in-human dosing around 2020 and Phase 2 results in the New England Journal of Medicine in 2023. The Phase 3 TRIUMPH programme launched in 2023 and reported across December 2025 to July 2026, with all pivotal trials meeting their primary endpoints. An FDA filing has been signalled for Q1 2027.
Key facts
- Phase 1
- ~2020 (NCT04143802)
- Phase 2
- Published NEJM 2023 (Jastreboff et al.)
- Phase 3 launch
- 2023 (TRIUMPH programme)
- First Phase 3 readout
- TRIUMPH-4, December 2025
- Pivotal readout
- TRIUMPH-1, 21 May 2026
- Comorbid populations
- TRIUMPH-2 and -3, July 2026
- Signalled FDA filing
- Q1 2027
What is the TRIUMPH programme?
TRIUMPH is Eli Lilly's Phase 3 development umbrella for retatrutide, comprising multiple trials across obesity, type 2 diabetes and cardiovascular populations, with more than 5,800 participants enrolled in total. Registrations are listed on ClinicalTrials.gov.
How the Phase 3 readouts landed
TRIUMPH-4 reported first in December 2025. The pivotal obesity study, TRIUMPH-1, reported topline results on 21 May 2026 across 2,339 randomised adults. TRIUMPH-2, in obesity with type 2 diabetes, and TRIUMPH-3, in severe obesity with established cardiovascular disease, both reported in July 2026 and both met their primary endpoints.
Research material referenced
Retatrutide 10mg, third-party HPLC tested
What comes next
Further Phase 3 readouts were expected across 2026, including maintenance-dosing studies examining what happens when the dose is reduced or withdrawn. Lilly has signalled an FDA Biologics License Application in the first quarter of 2027; regulatory review commonly adds a year or more, and retatrutide remains investigational throughout.
Quick reference
| Stage | Date | Outcome |
|---|---|---|
| Phase 1 | 2020 | First-in-human, single/multiple ascending doses |
| Phase 2 | 2022–2023 | Obesity + T2D; NEJM publication 2023 |
| TRIUMPH-4 | Dec 2025 | First Phase 3 readout |
| TRIUMPH-1 | 21 May 2026 | 28.3% mean reduction at 80 wks (12 mg) |
| TRIUMPH-2 / -3 | July 2026 | Both met primary endpoints |
| FDA filing | Q1 2027 (planned) | Not yet submitted |
Frequently asked questions
- How long are Phase 3 trials?
- TRIUMPH trials run multi-year. TRIUMPH-1 had its primary analysis at 80 weeks with a 104-week extension.
- Is the Phase 3 programme finished?
- The pivotal trials have reported, but the programme continues. Maintenance-dosing studies were still outstanding.
- When could retatrutide reach the market?
- No date exists. A filing was signalled for Q1 2027, and review typically takes a year or more with no guaranteed outcome.
Extended research context
The Retatrutide Research deep dive
Deep dive: how the triple-agonist scaffold was engineered
Retatrutide's 39-residue backbone was designed by Eli Lilly's peptide chemistry team to preserve the pharmacophores of three glucagon-family receptors on a single chain. The N-terminal domain retains GIP-receptor contacts, mid-chain substitutions restore GLP-1-receptor affinity lost in native GIP, and additional residue swaps confer glucagon-receptor engagement. A γGlu-2xOEG linker anchors a C20 fatty diacid at Lys17, which reversibly binds serum albumin and slows renal clearance. This is the same albumin-tethering strategy Novo Nordisk pioneered with semaglutide and Lilly refined further in tirzepatide.
The TRIUMPH Phase 3 programme in context
TRIUMPH is Lilly's global Phase 3 development umbrella for retatrutide, spanning obesity (TRIUMPH-1 through TRIUMPH-4), type 2 diabetes, MASH (metabolic dysfunction-associated steatohepatitis), and knee osteoarthritis linked to obesity. Readouts began in 2025 and continue through 2026. Because the compound is investigational, no regulator (FDA, EMA, or MHRA) has issued marketing authorisation, and legitimate supply exists only for laboratory reference and research contexts, never for human administration.
How retatrutide differs from tirzepatide and semaglutide at the mechanism level
Semaglutide is a mono-agonist (GLP-1 only). Tirzepatide is a dual agonist (GIP + GLP-1). Retatrutide adds glucagon-receptor activity, which pre-clinical and Phase 2 data suggest contributes to energy expenditure in addition to appetite regulation and glucose-dependent insulin release. This three-receptor combination is why retatrutide is sometimes called a 'metabolic multi-tool' peptide in the trade press, but the pharmacology is more nuanced than the label implies.
Research applications
- ▸In vitro receptor-binding assays across GIP-R, GLP-1R and GCGR panels
- ▸Comparator studies alongside semaglutide, tirzepatide and liraglutide reference standards
- ▸Analytical-method development: HPLC retention profiling and LC-MS confirmation
- ▸Stability testing of lipidated 39-residue peptides in aqueous and lyophilised forms
- ▸Reference material for teaching incretin pharmacology in university-level courses
Handling checklist
- ✓Store lyophilised vials at −20 °C; protect from light and humidity
- ✓Reconstitute with bacteriostatic water; avoid vortexing (foams the peptide)
- ✓Once reconstituted, store at 2–8 °C and use within 28 days
- ✓Verify batch CoA: HPLC ≥98%, mass matches ~4,731 Da, endotoxin low
- ✓Do not administer to humans or animals. Research use only
Common research-handling mistakes
Learnt from thousands of researcher orders across our UK labs.
✗ Confusing retatrutide with tirzepatide in supplier catalogues
Fix: Cross-check the LY code (LY3437943 = retatrutide; LY3298176 = tirzepatide) and the receptor profile on the CoA.
✗ Using tap or filtered water for reconstitution
Fix: Only use bacteriostatic water for injection (0.9% benzyl alcohol) or sterile water, never lab DI water.
✗ Storing reconstituted solution at room temperature
Fix: Refrigerate at 2–8 °C immediately after reconstitution; discard after 28 days.
Continue researching
Peer-reviewed guides, comparators and matched reference materials.
Related questions researchers ask
- Is retatrutide the same molecule as LY3437943?
- What is the correct spelling: retatrutide or retatrutid?
- Is retatrutide a GLP-1 drug?
- Which company makes retatrutide?
- When will retatrutide be FDA approved?
- Is retatrutide legal in the UK?
Primary sources & clinical trials
Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.
- RefJastreboff et al., NEJM 2023 (Phase 2)nejm.org
- RefTRIUMPH-1 topline results: Eli Lillyinvestor.lilly.com
- RefTwo additional Phase 3 obesity trials. Eli Lillyinvestor.lilly.com
- TrialClinicalTrials.gov: retatrutideclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-1 (NCT05929066). Retatrutide Phase 3 obesity trialclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-2 (NCT05929079). Retatrutide in type 2 diabetesclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-3 (NCT05882045). Retatrutide + established CVDclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-4 (NCT05931367). Retatrutide once weeklyclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-5 (NCT06662383). Retatrutide vs tirzepatideclinicaltrials.gov
- TrialClinicalTrials.gov · TRIUMPH-6 (NCT06859268). Maintenance of weight reductionclinicaltrials.gov
- PubMedJastreboff AM et al., Triple-Hormone-Receptor Agonist Retatrutide for Obesity. NEJM 2023 (PMID 37366315)pubmed.ncbi.nlm.nih.gov
- PubMedRosenstock J et al., Retatrutide for people with type 2 diabetes. Lancet 2023 (PMID 37385280)pubmed.ncbi.nlm.nih.gov
Written and reviewed by
The UK Peptides Editorial Team · Research library, UK Peptides
The editorial team is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate. Corrections are made in place and the review date updated.
More Retatrutide Research articles
- Who Develops Retatrutide?Eli Lilly, under the code LY3437943. Why that matters for reading trial data, and why no licensed retatrutide product exists.
- Retatrutide Half-Life: Where It Comes FromThe C20 diacid binds albumin reversibly, supporting once-weekly trial dosing. Why chain length sets duration across the whole incretin family.
- Retatrutide Chemical Identity: What Can Actually Be VerifiedRetatrutide has no findable PubChem record. What that means for its reported CAS and molecular weight, and why one widely cited identifier is tirzepatide's.
- How the Incretin Field Got HereExenatide from lizard venom, liraglutide's fatty acid, semaglutide's weekly dosing, then multi-agonism. Each generation solved the previous one's limit.
- Retatrutide Storage and StabilityA lipidated 39-mer is more surface-active than most peptides. Why foaming matters more here, and what the fatty acid changes about handling.
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