UK Peptides · Research Index

Every Retatrutide Research Question Answered, in 27 Studies

Investigational GIP/GLP-1/glucagon triple-agonist peptide (LY3437943).

Molecular weight
4810.5 g/mol
Also written
LY3437943, Reta

Reference records: DrugBank · Wikidata

27 referenced articles

Open research questions

  • 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?

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 — 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.

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 mistakes

Confusing retatrutide with tirzepatide in supplier catalogues
Cross-check the LY code (LY3437943 = retatrutide; LY3298176 = tirzepatide) and the receptor profile on the CoA.
Using tap or filtered water for reconstitution
Only use bacteriostatic water for injection (0.9% benzyl alcohol) or sterile water — never lab DI water.
Storing reconstituted solution at room temperature
Refrigerate at 2–8 °C immediately after reconstitution; discard after 28 days.

Related reading

Reference material for laboratory research. Not medical advice, and not an offer to supply any compound for human use.