Retatrutide

Obesity and type 2 diabetes mellitus (T2DM) are global health crises with significant morbidity and mortality. Retatrutide, a novel triple receptor agonist targeting glucagon-like peptide-1 (GLP-1), Glucose-Dependent Insulinotropic Polypeptide (GIP), and glucagon receptors, represents a groundbreaking advancement in obesity and T2DM pharmacotherapy. This review synthesizes findings from preclinical and clinical studies, highlighting retatrutide's mechanisms, efficacy, and safety profile. Retatrutide's unique molecular structure enables potent activation of GLP-1, GIP, and glucagon receptors, leading to significant weight reduction, improved glycemic control, and favorable metabolic outcomes. Animal studies demonstrate retatrutide's ability to delay gastric emptying, reduce food intake, and promote weight loss, with superior efficacy compared to other incretin-based therapies. Phase I and II clinical trials corroborate these findings, showing dose-dependent weight loss, reductions in Glycated Hemoglobin (HbA1c) levels, and improvements in liver steatosis and diabetic kidney disease. Common adverse effects are primarily gastrointestinal and dose-related. Ongoing Phase III trials, such as the TRIUMPH studies, aim to further evaluate retatrutide's long-term safety and efficacy in diverse patient populations. While retatrutide shows immense promise, considerations regarding cost and the quality of weight loss beyond BMI reduction warrant further investigation. Retatrutide heralds a new era in obesity and T2DM treatment, offering hope for improved patient outcomes.

INTRODUCTION: Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are increasingly used for T2DM and obesity. AREAS COVERED: An electronic search was conducted in Scopus, PubMed/MEDLINE, and Google Scholar databases. Retatrutide (LY3437943) is a novel triple agonist targeting glucagon receptor (GCGR), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon-like peptide-1 receptor (GLP-1 R). In subjects with type 2 diabetes mellitus (T2DM), decreased glycated hemoglobin (HbA1c) by up to 2.16% and decreased fasting glucose by up to 69.1 mg/dL have been seen. Weight loss up to 16.94% was observed in subjects with T2DM. Subjects with overweight or obesity experienced a greater weight loss by up to 26.56% (24.15 kg). Reductions in body-mass index and waist circumference were achieved. In subjects with T2DM and overweight or obesity, decreased systolic blood pressure was found. Finally, relative liver fat count in subjects with metabolic dysfunction-associated steatotic liver disease (MASLD) was reduced by up to 86%. Increased frequency of mild-to-moderate gastrointestinal adverse events (mainly nausea, vomiting, constipation, and diarrhea) was reported in participants on the highest retatrutide doses, likely due to rapid dose escalation and higher starting dose. EXPERT OPINION: These promising effects on glycemic control, weight loss, and emerging pleiotropic actions merit further investigation.

BACKGROUND: Retatrutide, a glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1, and glucagon receptor agonist, has demonstrated robust glucose and bodyweight reductions in participants with type 2 diabetes. This substudy assessed percent change from baseline to week 36 in total body fat mass versus placebo and dulaglutide. METHODS: This phase 2, double-blind, parallel-group, placebo-controlled, randomised controlled trial was done in 42 medical centres in the USA. Eligible participants were adults aged 18-75 years with type 2 diabetes, HbA1c of 7·0-10·5%, stable bodyweight, and BMI of 25-50 kg/m2. Eligible participants were randomly assigned in a 2:2:2:1:1:1:1:2 ratio to once-weekly subcutaneous placebo, dulaglutide 1·5 mg, or retatrutide 0·5 mg, 4 mg (2 mg initial dose), 4 mg (4 mg initial dose), 8 mg (2 mg initial dose), 8 mg (4 mg initial dose), or 12 mg. The prespecified primary substudy endpoint was percent change from baseline to week 36 in total fat mass, as measured by dual-energy X-ray absorptiometry (DXA). Regression methods with on-treatment data before study drug discontinuation from all randomly assigned participants with non-missing DXA scans were included in efficacy analysis. All participants who received at least one dose of study drug were included in the safety analysis population. The completed trial is registered with ClinicalTrials.gov, NCT04867785. FINDINGS: Between May 13, 2021 and June 13, 2022, 534 participants were screened for inclusion into the main study. 253 were excluded and 281 participants were enrolled and randomly assigned to the main study. Of the main study participants, 189 participants were enrolled to the body composition substudy (29 in the placebo group, 32 in the retatrutide 0·5 mg group, 31 in the retatrutide 4 mg groups [pooled], 33 in the retatrutide 8 mg group [pooled], 30 in the retatrutide 12 mg group, and 34 in the dulaglutide 1·5 mg group). Of these, 155 had a baseline DXA scan and 103 completed treatment and both baseline and week 36 DXA scans. 105 (56%) of 189 participants were female and 84 (44%) were male. 160 (85%) of 189 participants were White, 24 (13%) were Black, and five (3%) were Asian. Percent reduction from baseline in total fat mass was 4·9% (SE 1·4%) with retatrutide 0·5 mg, 15·2% (3·2%) with retatrutide 4 mg (pooled), 26·1% (2·5%) with retatrutide 8 mg (pooled), 23·2% (3·0%) with retatrutide 12 mg, 2·6% (1·6%) with dulaglutide, and 4·5% (1·2%) with placebo. Least squares mean change from baseline in total fat mass compared to placebo was -0·4 (95% CI -4·0 to 3·2, p=0·83 with retatrutide 0·5 mg, -10·7 (-17·2 to -4·2, p=0·0013) with retatrutide 4 mg (pooled), -21·6 (-27·1 to -16·1, p<0·0001) with retatrutide 8 mg (pooled), and -18·7 (-25·1 to -12·3, p<0·0001) with retatrutide 12 mg. Adverse events were similar between groups. Serious adverse events occurred in two (7%) of 29 participants in the placebo group, two (6%) of 32 participants in the retatrutide 0·5 mg group, zero of 31 participants in the retatrutide 4 mg group, three (9%) of 33 participants in the retatrutide 8 mg group, one (3%) of 30 participants in the retatrutide 12 mg group, and zero of 34 participants in the dulaglutide group. Gastrointestinal events were the most frequently reported adverse events, and no deaths were reported. INTERPRETATION: In adults with type 2 diabetes, retatrutide significantly improved total body fat mass reduction compared with placebo and dulaglutide. The proportion of lean mass loss to weight loss was similar to other obesity treatments. These findings could provide reassurance that a greater proportion of lean mass is not lost with retatrutide despite the overall increased weight loss. FUNDING: The study was funded by Eli Lilly and Company.

Retatrutide is a novel triple agonist of the glucose-dependent insulinotropic polypeptide, glucagon-like peptide 1 and glucagon receptors. A 48-week phase 2 obesity study demonstrated weight reductions of 22.8% and 24.2% with retatrutide 8 and 12 mg, respectively. The primary objective of this substudy was to assess mean relative change from baseline in liver fat (LF) at 24 weeks in participants from that study with metabolic dysfunction-associated steatotic liver disease and ≥10% of LF. Here, in this randomized, double-blind, placebo-controlled trial, participants (n = 98) were randomly assigned to 48 weeks of once-weekly subcutaneous retatrutide (1, 4, 8 or 12 mg dose) or placebo. The mean relative change from baseline in LF at 24 weeks was -42.9% (1 mg), -57.0% (4 mg), -81.4% (8 mg), -82.4% (12 mg) and +0.3% (placebo) (all P < 0.001 versus placebo). At 24 weeks, normal LF (<5%) was achieved by 27% (1 mg), 52% (4 mg), 79% (8 mg), 86% (12 mg) and 0% (placebo) of participants. LF reductions were significantly related to changes in body weight, abdominal fat and metabolic measures associated with improved insulin sensitivity and lipid metabolism. The ClinicalTrials.gov registration is NCT04881760 .

BACKGROUND: Retatrutide is a GIP, GLP-1, and glucagon triple hormone receptor agonist, under clinical development for type 2 diabetes, obesity, and related complications. We aimed to assess the efficacy and safety of retatrutide as a monotherapy in people with type 2 diabetes that is inadequately controlled by diet and exercise alone. METHODS: In this 40-week, phase 3, randomised, double-blind, placebo-controlled trial at 48 sites in the USA, Mexico, and India, we recruited adults (aged ≥18 years) with type 2 diabetes that is inadequately controlled by diet and exercise alone, glycated haemoglobin (HbA1c) between 7·0% and 9·5% (53-80 mmol/mol), and BMI of at least 23 kg/m2. Participants were randomly assigned (1:1:1:1) to receive retatrutide (4 mg, 9 mg, or 12 mg) or placebo by once-weekly subcutaneous injection. The primary endpoint was the change in HbA1c concentration from baseline to week 40. A key secondary endpoint was the percentage change in bodyweight from baseline to week 40. This trial is registered with ClinicalTrials.gov, NCT06354660, and is completed. FINDINGS: Between April 10, 2024, and April 21, 2025, 930 participants were screened and 537 (296 [55%] female and 241 [45%] male) were randomly assigned: 134 to retatrutide 4 mg, 133 to retatrutide 9 mg, 136 to retatrutide 12 mg, and 134 to placebo. Baseline mean age was 48·8 years (SD 12·1), mean HbA1c concentration was 7·9% (SD 1·1), mean duration of diabetes was 2·5 years (SD 4·4), and mean BMI was 35·8 kg/m2 (SD 7·0). 490 (91%) participants completed the treatment period on study drug and 504 (94%) completed the study. For the treatment regimen estimand, the mean change from baseline in HbA1c concentration was -1·69% (SE 0·11) with retatrutide 4 mg, -1·86% (0·10) with 9 mg, and -1·94% (0·08) with 12 mg, versus -0·81% (0·12) with placebo, resulting in estimated treatment differences versus placebo of -0·88% (95% CI -1·18 to -0·59) with retatrutide 4 mg, -1·04% (-1·32 to -0·76) with 9 mg, and -1·12% (-1·39 to -0·85) with 12 mg (all p<0·0001). The mean percentage change from baseline in bodyweight was -11·5% (SE 0·7) with retatrutide 4 mg, -13·9% (0·8) with 9 mg, and -15·3% (0·8) with 12 mg, versus -2·6% (0·5) with placebo. The most frequent adverse events with retatrutide were generally mild to moderate gastrointestinal events, which subsided over time. Study intervention discontinuations due to adverse events were 2-5% with retatrutide and 0% with placebo. No severe hypoglycaemia was reported. Two deaths occurred during the study, both in the retatrutide 4 mg group and unrelated to the study drug. INTERPRETATION: Retatrutide showed significant improvements in glycaemic control and bodyweight reduction as a monotherapy in adults with type 2 diabetes that is inadequately controlled with diet and exercise alone, with an adverse event profile consistent with molecules with GLP-1 agonist activity, supporting its potential as an effective treatment for type 2 diabetes. FUNDING: Eli Lilly and Company.

BACKGROUND: Retatrutide (LY3437943) is an agonist of the glucose-dependent insulinotropic polypeptide, glucagon-like peptide 1, and glucagon receptors. Its dose-response relationships with respect to side effects, safety, and efficacy for the treatment of obesity are not known. METHODS: We conducted a phase 2, double-blind, randomized, placebo-controlled trial involving adults who had a body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) of 30 or higher or who had a BMI of 27 to less than 30 plus at least one weight-related condition. Participants were randomly assigned in a 2:1:1:1:1:2:2 ratio to receive subcutaneous retatrutide (1 mg, 4 mg [initial dose, 2 mg], 4 mg [initial dose, 4 mg], 8 mg [initial dose, 2 mg], 8 mg [initial dose, 4 mg], or 12 mg [initial dose, 2 mg]) or placebo once weekly for 48 weeks. The primary end point was the percentage change in body weight from baseline to 24 weeks. Secondary end points included the percentage change in body weight from baseline to 48 weeks and a weight reduction of 5% or more, 10% or more, or 15% or more. Safety was also assessed. RESULTS: We enrolled 338 adults, 51.8% of whom were men. The least-squares mean percentage change in body weight at 24 weeks in the retatrutide groups was -7.2% in the 1-mg group, -12.9% in the combined 4-mg group, -17.3% in the combined 8-mg group, and -17.5% in the 12-mg group, as compared with -1.6% in the placebo group. At 48 weeks, the least-squares mean percentage change in the retatrutide groups was -8.7% in the 1-mg group, -17.1% in the combined 4-mg group, -22.8% in the combined 8-mg group, and -24.2% in the 12-mg group, as compared with -2.1% in the placebo group. At 48 weeks, a weight reduction of 5% or more, 10% or more, and 15% or more had occurred in 92%, 75%, and 60%, respectively, of the participants who received 4 mg of retatrutide; 100%, 91%, and 75% of those who received 8 mg; 100%, 93%, and 83% of those who received 12 mg; and 27%, 9%, and 2% of those who received placebo. The most common adverse events in the retatrutide groups were gastrointestinal; these events were dose-related, were mostly mild to moderate in severity, and were partially mitigated with a lower starting dose (2 mg vs. 4 mg). Dose-dependent increases in heart rate peaked at 24 weeks and declined thereafter. CONCLUSIONS: In adults with obesity, retatrutide treatment for 48 weeks resulted in substantial reductions in body weight. (Funded by Eli Lilly; ClinicalTrials.gov number, NCT04881760.).