Retatrutide
Chemical compound
From Wikipedia, the free encyclopedia
Retatrutide (LY-3437943) is an experimental drug[1] for obesity developed by the American pharmaceutical company Eli Lilly and Company. It is a triple hormone receptor agonist on the GLP-1, GIP, and glucagon receptors.[2][3][4]
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| Other names | LY-3437943 |
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Adverse effects
The safety profile of retatrutide is still under investigation. Reported side effects have been gastrointestinal symptoms, such as nausea, vomiting, diarrhea, constipation, and abdominal discomfort. An increase in side effects occurred with increased dosages. Less commonly reported side effects have included fatigue, headaches, and mild increases to heart rate. All drugs targeting GLP-1 receptors currently have the potential risk for pancreatitis, gallbladder disease, and gastrointestinal intolerance. These effects have not been linked to retatrutide in current trials. However, long-term outcomes of side effects are still being established.[5]
Mechanism of action
GLP-1 receptors improve insulin sensitivity and increase satiety. Retatrutide has shown to increase insulin secretion. Furthermore, agonism of the glucagon receptor increases energy expenditure and promotes fat loss and metabolic activity. With current research, activation of these receptors has overall reduced caloric intake and increased energy expenditure, successfully leading to higher weight loss compared to alternative treatments.[2]
Chemistry
Retatrutide is a peptide with the following amino acid sequence[6]
YA¹QGTFTSDYSIL²LDKK⁴AQA¹AFIEYLLEGGPSSGAPPPS³
where letters with superscripted numbers refer to the following chemical modifications:
- A¹ – 2-aminoisobutyric acid (Aib).
- L² – leucine modified with an α-methyl substituent (MeL, 2-methylleucine).
- S³ – L-serinamide (L-serine with the carboxylic acid group replaced with a carboxamide).
- K⁴ – L-lysine with the amino group at position 6 modified with a side chain; specifically, (AEEA)-(γ-Glu)-(C20 diacid) (where AEEA is 2-[2-(2-aminoethoxy)ethoxy]acetic acid, commonly used as a spacer group in synthetic peptides).
Retatrutide is synthetically engineered and produced using solid-phase peptide synthesis (SPPS). This is when amino acids are added to a peptide chain and attached to solid resin forming a backbone. After the backbone is synthesized, the molecule is cleaved chemically, then purified. Lipidation modifications also occur, meaning a fatty-acid side chain is added to promote reversible binding to albumin. This modification allows for a longer drug half-life, raising compliance as it enables once-weekly dosing.[2]
History
Clinical trials
Retatrutide has been studied in a phase 2 trial involving adults without diabetes but with obesity or preobesity (overweight).[7][8][5] Retatrutide is also being evaluated in phase 3 clinical trials.[9] Two trials in the phase 3 TRIUMPH program reached primary completion in April 2026: TRIUMPH-1, a master protocol in adults with obesity or overweight, and TRIUMPH-3, in participants with severe obesity and established cardiovascular disease.[10][11][12] A substudy in adults with type 2 diabetes reported differences in total body fat mass between study groups at 36 weeks.[13]
Preclinical and biochemical studies describe receptor activity at GLP-1, GIP, and glucagon receptors.[14] Reports on its development state that it was engineered for activity across these targets.[2]
Systematic reviews and meta-analyses of randomized controlled trials report that retatrutide produces substantial reductions in body weight in adults with obesity, with mean percentage weight loss typically between 15 and 24 percent over 48 to 72 weeks, depending on study protocols and populations.[15][16][17][18][19] Adverse events are most commonly gastrointestinal symptoms such as nausea and diarrhea, with relatively low rates of study discontinuation and infrequent serious adverse events reported during trials.[15][16][17] Safety assessments also indicate a low risk of hypoglycemia and no significant elevation in cardiovascular or hepatic adverse events in non-diabetic populations across published studies.[18][19]
Society and culture
Multiple black market sellers of the peptide emerged before approval of the Lilly drug, leading to multiple lawsuits with Lilly as the plaintiff.[1]
Research
Retatrutide is under preliminary research for how it may influence obesity-associated cancer progression.[20]