Retatrutide is one of the newest compounds in metabolic research, but the science it’s built on goes back more than four decades — and, oddly enough, it starts with a venomous lizard. Here’s the story of how one molecule ended up doing the work of three.
Mapping the incretin system (1960s–1980s)
Long before anyone drew up retatrutide, researchers were working out the hormones that tell the body how to handle food. Through the 1960s and 70s, radioimmunoassay work led to GIP — the first “incretin,” a gut hormone that prompts insulin release after eating.
The bigger break came in 1983, when Bell and colleagues cloned the human proglucagon gene and uncovered two more peptides hidden inside it: GLP-1 and GLP-2. Between 1985 and 1987, Svetlana Mojsov identified the active fragment of GLP-1 and, with Habener, Drucker and Holst, showed it stimulated insulin secretion. That’s the moment GLP-1 became a target worth chasing.
The lizard that changed everything (1992)
There was one problem: natural GLP-1 breaks down within minutes, which makes it useless as a drug. The fix came from an unlikely place. Screening venoms for active peptides, John Eng — a researcher at a New York VA hospital — found a 39-amino-acid peptide in Gila monster (Heloderma suspectum) venom and named it exendin-4. It behaved like GLP-1 but resisted the enzyme that degrades it, stretching its active life from minutes to hours. Eng published it in 1992, and the entire GLP-1 class traces back to that find.
From venom to designed molecules (2005–2022)
Exendin-4 was licensed in 1996, developed as exenatide, and became the first GLP-1 receptor agonist on the market in 2005. The field moved fast from there. At Novo Nordisk, a team led by Lotte Bjerre Knudsen developed a fatty-acid “acylation” method that let these peptides last far longer — the platform behind liraglutide and later semaglutide. Then Eli Lilly’s tirzepatide combined GLP-1 with GIP in one molecule, which raised the obvious question: what if you added a third receptor?
Retatrutide arrives (2016–2023)
That third target was the glucagon receptor. Building on the same framework that produced tirzepatide, Eli Lilly engineered a molecule — coded LY3437943 — that activates GLP-1, GIP and glucagon receptors at once. It was designed in the mid-to-late 2010s, first dosed in humans in 2019, and its pharmacology was disclosed in 2022 (Coskun et al., Cell Metabolism). In June 2023, Jastreboff and colleagues published Phase 2 results in the New England Journal of Medicine: in a 338-person study, the highest dose produced a mean body-weight reduction of 24.2% over 48 weeks — numbers that turned serious heads across the research community.
Where it stands now
Retatrutide advanced into Eli Lilly’s large-scale Phase 3 TRIUMPH program, with the first positive readout reported in December 2025. It remains one of the most actively studied peptides in metabolic science.
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Research use only
Everything above is scientific and historical background. Retatrutide is supplied strictly as a research compound — not for human or animal use. Every batch of R3TA we stock is independently third-party lab-tested with a published Certificate of Analysis (COA), so researchers know exactly what they’re working with.