{"id":67,"slug":"67-retatrutide-trp-25-7-aza-tryptophan-7-aza-trp-single-non-canonical-subst","title":"Retatrutide Trp-25 → 7-aza-Trp: tune GCGR aromatic contact for selectivity rebalancing","status":"PENDING","fold_verdict":"DISCARDED","discard_reason":null,"peptide":{"name":"Retatrutide","class":"METABOLIC","sequence":"YAQGTFTSDYSIYLDKQAAKDFVQWLLAGGPSSGAPPPS","modified_sequence":"YAQGTFTSDYSIYLDKQAAKDFVQ-[7azaW]-LLAGGPSSGAPPPS","modification_description":"Trp-25 → 7-aza-tryptophan (7-aza-Trp) single non-canonical substitution; replace the C7 carbon of the indole ring with nitrogen, preserving ring geometry and aromaticity but adding an H-bond acceptor and altering π-electronics. All other residues including native Lys-20 lipidation site are preserved."},"target":{"protein":"Glucagon receptor","uniprot_id":"P47871","chembl_id":"CHEMBL2069","gene_symbol":"GCGR"},"rationale":{"hypothesis":"Substituting Trp-25 of Retatrutide with 7-aza-tryptophan will subtly rebalance triple-agonist selectivity by altering the aromatic ring's electrostatics at a position that contacts the extracellular domain (ECD) hydrophobic groove of class B GPCRs. We hypothesize the aza-nitrogen will form a new H-bond with a polar GCGR ECD residue while disfavoring the more hydrophobic GLP-1R/GIPR pockets, biasing the agonist toward GCGR engagement (a pharmacology of interest for hepatic lipid mobilization in obesity).","rationale":"In glucagon and GLP-1 cocrystal structures, the conserved Trp-25 sits in the ECD hydrophobic cleft and its indole nitrogen geometry differs in contact preferences across GLP-1R, GIPR, and GCGR. 7-aza-Trp is an isosteric replacement (same ring footprint, same NH donor) but introduces a ring-N H-bond acceptor that distinguishes the three receptors' local environments — GCGR has a more polar floor at this position than GLP-1R. This is a single-atom electronic tuning experiment, distinct from steric/cyclization strategies. Per rotation rule, the last three folds were CONFORMATION (stapled), D-amino acid, and non-canonical AA on a non-class-B target; my SELECTIVITY focus diverges from the recent CONFORMATION/STABILITY runs, and I'm targeting GCGR (class B) — but with a single ring-atom isostere rather than the AlphaFold-blind chemistries (Aib, hexenoyl, hydrocarbon staples) that the tool-limit guidance flags. 7-aza-Trp is a benign aromatic isostere that AF-family models handle as standard Trp geometry-wise.","predicted_outcome":"We expect a fold with pLDDT comparable to Trp-25 wildtype Retatrutide (≥0.7), preserved central helix and C-terminal ECD-binding segment, and at the Trp-25/GCGR ECD interface a new H-bond from the 7-aza nitrogen to a backbone amide or polar side chain (e.g., Asp/Asn) on the receptor — absent or weaker in the GLP-1R/GIPR equivalent contact when modeled comparatively.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":0.7774884700775146,"ptm":0.7560876607894897,"iptm":0.1744716763496399,"chai_agreement":null,"chai1_gated_decision":"SKIPPED_HIGH_CONFIDENCE","binding_probability":null,"binding_pic50":null,"predicted_binding_change":null},"profile":{"aggregation_propensity":0.197,"stability_score":0.647,"bbb_penetration_score":0.063,"half_life_estimate":"long (>6 hours, depends on modifications)"},"narrative":{"tldr":null,"detailed_analysis":null,"executive_summary":null,"tweet_draft":null,"research_brief_markdown":null,"structural_caption":"No reliable 3D structure could be obtained for this peptide.","key_findings_summary":"Retatrutide (LY3437943) is a synthetic peptide triple agonist at the GIP, GLP-1, and glucagon receptors (GCGR), developed by Eli Lilly, that has demonstrated exceptional efficacy in Phase 2 clinical trials for obesity and type 2 diabetes. The clinical literature (Jastreboff et al. 2023, Rosenstock et al. 2023) establishes dose-dependent weight reductions of up to 24.2% at 48 weeks and robust improvements in glycemic control, with the glucagon receptor component credited with enhancing energy expenditure and hepatic lipid mobilization beyond what GLP-1/GIP co-agonism alone achieves. The MASLD substudy (Sanyal et al. 2024) is particularly relevant: retatrutide produced up to 82.4% relative reduction in liver fat at 24 weeks, an effect partially attributed to GCGR-driven hepatic lipid oxidation and lipolysis — directly supporting the hypothesis that enhanced GCGR engagement could be metabolically valuable in the context of hepatic lipid mobilization and obesity.\n\nThe pharmacological rationale for the hypothesis rests on the known biology of glucagon receptor signaling in the liver. GCGR activation promotes hepatic glycogenolysis, fatty acid oxidation, and ketogenesis, effects that complement rather than overlap with GLP-1R-mediated insulin secretion and GIP receptor-mediated incretin effects. Multiple reviews (Abdul-Rahman et al. 2024, Katsi et al. 2025) emphasize that retatrutide's differentiation from dual agonists like tirzepatide stems in part from its glucagon receptor activity, making selective enhancement of GCGR engagement a conceptually grounded pharmacological objective. However, the existing literature provides no direct structural or sequence-level characterization of retatrutide's interactions with individual receptor ECDs, so the molecular rationale for the Trp-25 → 7-aza-Trp substitution must be inferred from general class B GPCR structural biology rather than retatrutide-specific crystallography.\n\nThe structural basis of the hypothesis — that position 25 of retatrutide contacts the extracellular domain hydrophobic groove of class B GPCRs, and that an aza-nitrogen at the 7-position of the indole ring could form a new hydrogen bond with a polar GCGR ECD residue while disfavoring the more hydrophobic GLP-1R/GIPR binding pockets — is not addressed by any of the retrieved papers. The available literature is entirely clinical or pharmacological in nature; no structural studies of retatrutide bound to any of its three receptors, no SAR campaigns involving non-canonical amino acid substitutions, and no ECD-binding domain mapping studies are represented in this abstract set. This is a significant knowledge gap: the hypothesis requires specific structural assumptions (that Trp-25 is in ECD contact, that GCGR ECD has a proximal polar residue, that GLP-1R/GIPR ECD pockets are more hydrophobic at the equivalent position) that cannot be validated or refuted from the available literature alone.\n\nThe preprint evidence base is limited and predominantly clinical/meta-analytic in scope. The Windram et al. (2025) preclinical preprint is notable for showing that retatrutide, like semaglutide and tirzepatide, attenuates interoceptive alcohol effects in rats, suggesting CNS receptor engagement, but provides no mechanistic specificity relevant to the Trp-25 modification hypothesis. The gray market peptide quality study (Mendias & Awan 2026) is irrelevant to the hypothesis but flags that retatrutide analogs circulate in unregulated channels with highly variable purity — a practical concern for any research use of modified analogs. Overall, the literature strongly supports retatrutide's therapeutic profile and the importance of GCGR engagement for hepatic metabolic effects, but is silent on the molecular pharmacology and structural biology needed to directly evaluate the proposed modification."},"structured":{"known_activity":null,"known_binders":null,"candidate_variants":null,"domain_annotations":null,"literature_context":{"pubmed":[{"pmid":"37366315","title":"Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial.","abstract":"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.\n\nMETHODS: 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.\n\nRESULTS: 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.\n\nCONCLUSIONS: In adults with obesity, retatrutide treatment for 48 weeks resulted in substantial reductions in body weight. (Funded by Eli Lilly; ClinicalTrials.gov number, NCT04881760.).","authors":["Jastreboff Ania M","Kaplan Lee M","Frías Juan P","Wu Qiwei","Du Yu","Gurbuz Sirel","Coskun Tamer","Haupt Axel","Milicevic Zvonko","Hartman Mark L"],"year":2023,"journal":"The New England journal of medicine"},{"pmid":"40563436","title":"Retatrutide-A Game Changer in Obesity Pharmacotherapy.","abstract":"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.","authors":["Katsi Vasiliki","Koutsopoulos Georgios","Fragoulis Christos","Dimitriadis Kyriakos","Tsioufis Konstantinos"],"year":2025,"journal":"Biomolecules"},{"pmid":"37385280","title":"Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.","abstract":"BACKGROUND: According to current consensus guidelines for type 2 diabetes management, bodyweight management is as important as attaining glycaemic targets. Retatrutide, a single peptide with agonist activity at the glucose-dependent insulinotropic polypeptide (GIP), GLP-1, and glucagon receptors, showed clinically meaningful glucose-lowering and bodyweight-lowering efficacy in a phase 1 study. We aimed to examine the efficacy and safety of retatrutide in people with type 2 diabetes across a range of doses.\n\nMETHODS: In this randomised, double-blind, double-dummy, placebo-controlled and active comparator-controlled, parallel-group, phase 2 trial, participants were recruited from 42 research and health-care centres in the USA. Adults aged 18-75 years with type 2 diabetes, glycated haemoglobin (HbA1c) of 7·0-10·5% (53·0-91·3 mmol/mol), and BMI of 25-50 kg/m2 were eligible for enrolment. Eligible participants were treated with diet and exercise alone or with a stable dose of metformin (≥1000 mg once daily) for at least 3 months before the screening visit. Participants were randomly assigned (2:2:2:1:1:1:1:2) using an interactive web-response system, with stratification for baseline HbA1c and BMI, to receive once-weekly injections of placebo, 1·5 mg dulaglutide, or retatrutide maintenance doses of 0·5 mg, 4 mg (starting dose 2 mg), 4 mg (no escalation), 8 mg (starting dose 2 mg), 8 mg (starting dose 4 mg), or 12 mg (starting dose 2 mg). Participants, study site personnel, and investigators were masked to treatment allocation until after study end. The primary endpoint was change in HbA1c from baseline to 24 weeks, and secondary endpoints included change in HbA1c and bodyweight at 36 weeks. Efficacy was analysed in all randomly assigned, except inadvertently enrolled, participants, and safety was assessed in all participants who received at least one dose of study treatment. The study is registered at ClinicalTrials.gov, NCT04867785.\n\nFINDINGS: Between May 13, 2021, and June 13, 2022, 281 participants (mean age 56·2 years [SD 9·7], mean duration of diabetes 8·1 years [7·0], 156 [56%] female, and 235 [84%] White) were randomly assigned and included in the safety analysis (45 in the placebo group, 46 in the 1·5 mg dulaglutide group, and 47 in the retatrutide 0·5 mg group, 23 in the 4 mg escalation group, 24 in the 4 mg group, 26 in the 8 mg slow escalation group, 24 in the 8 mg fast escalation group, and 46 in the 12 mg escalation group). 275 participants were included in the efficacy analyses (one each in the retatrutide 0·5 mg group, 4 mg escalation group, and 8 mg slow escalation group, and three in the 12 mg escalation group were inadvertently enrolled). 237 (84%) participants completed the study and 222 (79%) completed study treatment. At 24 weeks, least-squares mean changes from baseline in HbA1c with retatrutide were -0·43% (SE 0·20; -4·68 mmol/mol [2·15]) for the 0·5 mg group, -1·39% (0·14; -15·24 mmol/mol [1·56]) for the 4 mg escalation group, -1·30% (0·22; -14·20 mmol/mol [2·44]) for the 4 mg group, -1·99% (0·15; -21·78 mmol/mol [1·60]) for the 8 mg slow escalation group, -1·88% (0·21; -20·52 mmol/mol [2·34]) for the 8 mg fast escalation group, and -2·02% (0·11; -22·07 mmol/mol [1·21]) for the 12 mg escalation group, versus -0·01% (0·21; -0·12 mmol/mol [2·27]) for the placebo group and -1·41% (0·12; -15·40 mmol/mol [1·29]) for the 1·5 mg dulaglutide group. HbA1c reductions with retatrutide were significantly greater (p<0·0001) than placebo in all but the 0·5 mg group and greater than 1·5 mg dulaglutide in the 8 mg slow escalation group (p=0·0019) and 12 mg escalation group (p=0·0002). Findings were consistent at 36 weeks. Bodyweight decreased dose dependently with retatrutide at 36 weeks by 3·19% (SE 0·61) for the 0·5 mg group, 7·92% (1·28) for the 4 mg escalation group, 10·37% (1·56) for the 4 mg group, 16·81% (1·59) for the 8 mg slow escalation group, 16·34% (1·65) for the 8 mg fast escalation group, and 16·94% (1·30) for the 12 mg escalation group, versus 3·00% (0·86) with placebo and 2·02% (0·72) with 1·5 mg dulaglutide. For retatrutide doses of 4 mg and greater, decreases in weight were significantly greater than with placebo (p=0·0017 for the 4 mg escalation group and p<0·0001 for others) and 1·5 mg dulaglutide (all p<0·0001). Mild-to-moderate gastrointestinal adverse events, including nausea, diarrhoea, vomiting, and constipation, were reported in 67 (35%) of 190 participants in the retatrutide groups (from six [13%] of 47 in the 0·5 mg group to 12 [50%] of 24 in the 8 mg fast escalation group), six (13%) of 45 participants in the placebo group, and 16 (35%) of 46 participants in the 1·5 mg dulaglutide group. There were no reports of severe hypoglycaemia and no deaths during the study.\n\nINTERPRETATION: In people with type 2 diabetes, retatrutide showed clinically meaningful improvements in glycaemic control and robust reductions in bodyweight, with a safety profile consistent with GLP-1 receptor agonists and GIP and GLP-1 receptor agonists. These phase 2 data also informed dose selection for the phase 3 programme.\n\nFUNDING: Eli Lilly and Company.","authors":["Rosenstock Julio","Frias Juan","Jastreboff Ania M","Du Yu","Lou Jitong","Gurbuz Sirel","Thomas Melissa K","Hartman Mark L","Haupt Axel","Milicevic Zvonko","Coskun Tamer"],"year":2023,"journal":"Lancet (London, England)"},{"pmid":"39515565","title":"The power of three: Retatrutide's role in modern obesity and diabetes therapy.","abstract":"The increasing prevalence of obesity and type 2 diabetes mellitus has resulted in a significant challenge to public health throughout the globe. It required the development of novel therapeutic approaches. Retatrutide is a groundbreaking triple agonist that targets glucagon receptors, gastric inhibitory polypeptide, and glucagon-like peptide-1. Retatrutide's complex mechanism of action involves a synergistic interaction among these receptors, resulting in increased insulin secretion, improved glucose homeostasis, and refined appetite modulation. Clinical trials in phases 1 to 3 have demonstrated significant efficacy, highlighted by significant reductions in body weight and favorable glycemic control outcomes. Additionally, retatrutide shows promise in mitigating cardiovascular risk factors and addressing metabolic dysfunction-associated steatotic liver disease. However, careful attention is required to delineate its long-term safety profile, explore its potential in special populations, unravel its adjunctive therapeutic roles, and elucidate its mechanisms in pediatric cohorts. As a transformative therapeutic modality, retatrutide represents a beacon of hope, signifying transformative changes in the management landscape of obesity and type 2 diabetes mellitus (T2DM), and warranting continued exploration and refinement in clinical practice. This narrative review examines the therapeutic potential of retatrutide in the management of obesity and T2DM.","authors":["Abdul-Rahman Toufik","Roy Poulami","Ahmed Fatma Kamal","Mueller-Gomez Jann Ludwig","Sarkar Sarmistha","Garg Neil","Femi-Lawal Victor Oluwafemi","Wireko Andrew Awuah","Thaalibi Hala Ibrahim","Hashmi Muhammad Usman","Dzebu Andrew Sefenu","Banimusa Sewar Basheer","Sood Aayushi"],"year":2024,"journal":"European journal of pharmacology"},{"pmid":"39318607","title":"Effects of once-weekly subcutaneous retatrutide on weight and metabolic markers: A systematic review and meta-analysis of randomized controlled trials.","abstract":"AIM: To assess the effects of once-weekly subcutaneous retatrutide on weight and metabolic markers and the occurrence of side effects in patients with overweight, obesity and/or type 2 diabetes (T2D).\n\nMETHODS: PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were systematically searched for placebo-controlled, randomized clinical trials (RCTs) published up until February 23, 2024. Weighted mean differences (WMDs) for continuous outcomes and risk ratios (RRs) for binary endpoints were computed, with 95 % confidence intervals (CIs).\n\nRESULTS: A total of three studies were included, comprising 640 patients, of whom 510 were prescribed retatrutide. Compared with placebo, retatrutide significantly reduced body weight (WMD -10.66 kg; 95 % CI -17.63, -3.69), body mass index (WMD -4.53 kg/m2; 95 % CI -7.51, -1.55), and waist circumference (WMD -6.61 cm; 95 % CI -13.17, -0.05). In addition, retatrutide significantly increased the proportion of patients who achieved a weight reduction of ≥5 % (RR 2.92; 95 % CI 2.17-3.93), ≥10 % (RR 9.32; 95 % CI 4.56-19.06), ≥15 % (RR 18.40; 95 % CI 6.00-56.42), and ≥20 % (RR 16.61; 95 % CI 4.17-66.12).\n\nCONCLUSIONS: In this meta-analysis, the use of once-weekly subcutaneous retatrutide was associated with a significant reduction in body weight and improvement of metabolic markers in patients with overweight, obesity and/or T2D, compared with placebo, with an increase in non-severe gastrointestinal and hypersensitivity adverse events. Phase 3 RCTs are expected to shed further light on the efficacy and safety of once-weekly subcutaneous retatrutide over the long term.","authors":["Pasqualotto Eric","Ferreira Rafael Oliva Morgado","Chavez Matheus Pedrotti","Hohl Alexandre","Ronsoni Marcelo Fernando","Pasqualotto Tales","Moraes Francisco Cezar Aquino de","Hespanhol Larissa","Figueiredo Watanabe Janine Midori","Lütkemeyer Carine","van de Sande-Lee Simone"],"year":2024,"journal":"Metabolism open"},{"pmid":"38858523","title":"Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial.","abstract":"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 .","authors":["Sanyal Arun J","Kaplan Lee M","Frias Juan P","Brouwers Bram","Wu Qiwei","Thomas Melissa K","Harris Charles","Schloot Nanette C","Du Yu","Mather Kieren J","Haupt Axel","Hartman Mark L"],"year":2024,"journal":"Nature medicine"},{"pmid":"41090431","title":"Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials.","abstract":"AIMS: Retatrutide, a novel synthetic molecule, is a triple agonist activating the glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1 and glucagon receptors. The TRIUMPH clinical development program evaluates its safety and efficacy concurrently for the treatment of obesity and two related complications-obstructive sleep apnea (OSA) and knee osteoarthritis (OA). A novel basket trial design simultaneously evaluates retatrutide treatment across these multiple adiposity-related disease states.\n\nMATERIALS AND METHODS: TRIUMPH consists of four Phase 3, multicenter, randomized, double-blind studies assessing weekly subcutaneous retatrutide compared to placebo, in conjunction with healthy diet and physical activity in over 5800 participants. The four trials consist of two weight management basket trials (TRIUMPH-1 and TRIUMPH-2) with OSA and/or OA protocols nested within the weight management trial; one weight management trial in a population with CVD (TRIUMPH-3); and one stand-alone OA trial (TRIUMPH-4). The primary endpoint for weight management is percent change in body weight, for OSA is change in Apnea-Hypopnea Index and for knee OA includes change in the Western Ontario and McMaster Universities Osteoarthritis Index pain subscale score. The basket trial permits independent analysis of weight management, OSA and OA studies with type I error rate controlled at α = 0.05, split between the overarching weight management and each basket trial.\n\nCONCLUSIONS: By recruiting participants with shared disease exposures, the TRIUMPH program will assess the safety and efficacy of retatrutide for the treatment of adults with obesity and two of its common complications-OSA and OA.","authors":["Giblin Kathryn","Kaplan Lee M","Somers Virend K","Le Roux Carel W","Hunter David J","Wu Qiwei","Lalonde Amy","Ahmad Nadia","Bethel Mary Angelyn"],"year":2026,"journal":"Diabetes, obesity & metabolism"},{"pmid":"40609566","title":"Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial.","abstract":"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.\n\nMETHODS: 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.\n\nFINDINGS: 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.\n\nINTERPRETATION: 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.\n\nFUNDING: The study was funded by Eli Lilly and Company.","authors":["Coskun Tamer","Wu Qiwei","Schloot Nanette C","Haupt Axel","Milicevic Zvonko","Khouli Courtney","Harris Charles"],"year":2025,"journal":"The lancet. Diabetes & endocrinology"},{"pmid":"39761578","title":"Efficacy and Safety of Glucagon-Like Peptide-1 Receptor Agonists for Weight Loss Among Adults Without Diabetes : A Systematic Review of Randomized Controlled Trials.","abstract":"BACKGROUND: Recent randomized controlled trials (RCTs) have investigated glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and dual or triple co-agonists for weight loss among adults with overweight or obesity and without diabetes.\n\nPURPOSE: To assess the efficacy and safety of GLP-1 RAs and co-agonists for the treatment of obesity among adults without diabetes.\n\nDATA SOURCES: MEDLINE, Embase, and Cochrane CENTRAL from inception to 4 October 2024.\n\nSTUDY SELECTION: Placebo-controlled RCTs in otherwise healthy participants with overweight or obesity.\n\nDATA EXTRACTION: The primary outcome was change in relative or absolute body weight from baseline to maximum on-treatment follow-up. Safety outcomes included death, serious adverse events (SAEs), any adverse events (AEs), and gastrointestinal AEs.\n\nDATA SYNTHESIS: A total of 26 RCTs comprising 15 491 participants (72% female; mean body mass index, 30 to 41 kg/m2; mean age, 34 to 57 years) and 12 agents (3 commercially available agents [liraglutide, semaglutide, and tirzepatide] and 9 premarket agents for long-term weight management) were included. Treatment ranged from 16 to 104 weeks (median, 43 weeks). Compared with placebo, tirzepatide (15 mg once weekly) resulted in weight loss of up to 17.8% (95% CI, 16.3% to 19.3%) after 72 weeks of therapy; semaglutide (2.4 mg once weekly), up to 13.9% (CI, 11.0% to 16.7%) after 68 weeks; and liraglutide (3.0 mg once daily), up to 5.8% (CI, 3.6% to 8.0%) after 26 weeks. Retatrutide (12 mg once weekly) produced greater weight loss of up to 22.1% (CI, 19.3% to 24.9%) after 48 weeks; other novel single and combination GLP-1 agents were also efficacious to varying degrees. Although AEs were frequent (GLP-1 RA vs. placebo: 80% to 97% vs. 63% to 100%), the majority were gastrointestinal-related (47% to 84% vs. 13% to 63%, respectively), most commonly nausea, vomiting, diarrhea, and constipation. AEs requiring treatment discontinuation (0% to 26% vs. 0% to 9%, respectively) and SAEs (0% to 10% vs. 0% to 12%, respectively) were rare.\n\nLIMITATIONS: No head-to-head RCTs were available. Heterogeneity prevented meta-analysis.\n\nCONCLUSION: GLP-1 RAs and co-agonists are efficacious for weight loss, with reported safety concerns predominantly gastrointestinal in nature, when used among adults with overweight or obesity and without diabetes.\n\nPRIMARY FUNDING SOURCE: None. (PROSPERO: CRD42024505558).","authors":["Moiz Areesha","Filion Kristian B","Toutounchi Helia","Tsoukas Michael A","Yu Oriana H Y","Peters Tricia M","Eisenberg Mark J"],"year":2025,"journal":"Annals of internal medicine"},{"pmid":"38843460","title":"Efficacy and Safety of GLP-1 Medicines for Type 2 Diabetes and Obesity.","abstract":"The development of glucagon-like peptide 1 receptor agonists (GLP-1RA) for type 2 diabetes and obesity was followed by data establishing the cardiorenal benefits of GLP-1RA in select patient populations. In ongoing trials investigators are interrogating the efficacy of these agents for new indications, including metabolic liver disease, peripheral artery disease, Parkinson disease, and Alzheimer disease. The success of GLP-1-based medicines has spurred the development of new molecular entities and combinations with unique pharmacokinetic and pharmacodynamic profiles, exemplified by tirzepatide, a GIP-GLP-1 receptor coagonist. Simultaneously, investigational molecules such as maritide block the GIP and activate the GLP-1 receptor, whereas retatrutide and survodutide enable simultaneous activation of the glucagon and GLP-1 receptors. Here I highlight evidence establishing the efficacy of GLP-1-based medicines, while discussing data that inform safety, focusing on muscle strength, bone density and fractures, exercise capacity, gastrointestinal motility, retained gastric contents and anesthesia, pancreatic and biliary tract disorders, and the risk of cancer. Rapid progress in development of highly efficacious GLP-1 medicines, and anticipated differentiation of newer agents in subsets of metabolic disorders, will provide greater opportunities for use of personalized medicine approaches to improve the health of people living with cardiometabolic disorders.","authors":["Drucker Daniel J"],"year":2024,"journal":"Diabetes care"}],"biorxiv":[{"pmid":"","doi":"10.21203/rs.3.rs-7103001/v1","title":"Efficacy and safety of retatrutide for overweight/obesity or type 2 diabetes: a systematic review and meta-analysis","abstract":"<title>Abstract</title>  <p>Aim To perform a meta-analysis to evaluate the efficacy and safety of retatrutide in patients with overweight/obesity and/or type 2 diabetes (T2D). Methods We systematically searched PubMed, Embase, Cochrane Library, Scopus, Web of Science, and ClinicalTrials.gov. Randomized controlled trials (RCTs) evaluating the efficacy and safety of retatrutide for overweight/obesity or T2D were included, with the date up to June 16, 2025. Outcomes were analysed using RevMan 5.4 and Stata 17.0. Weighted mean differences (WMDs) and risk ratios (RRs) were computed for continuous outcome variables and dichotomous data, respectively. Heterogeneity was assessed using the I² statistic. Results Retatrutide significantly reduced hemoglobin A1c (HbA1c) by 0.9% (95% CI: [-1.63, -0.17], P = 0.015), fasting blood glucose (FBG) by 21.87 mg/dL (95% CI: [-39.66, -4.09], P = 0.016), body weight by 10.66 kg (95% CI: [-17.64, -3.67], P = 0.003), and body mass index (BMI) by 4.55 kg/m<sup>2</sup> (95% CI: [-7.59, -1.51], P = 0.003). Additionally, retatrutide modestly reduced blood pressure and significantly reduced lipid profiles compared with placebo. However, treatment- emergent adverse events (TEAEs) and gastrointestinal adverse events, particularly nausea, vomiting, and constipation, were more frequent with retatrutide. Conclusions Retatrutide showed robust reductions in body weight and clinically meaningful improvements in glycemic control and cardiometabolic measures for patients with overweight/obesity and/or T2D. However, there was an increased risk of TEAEs, especially gastrointestinal adverse events. Further long-term, multicenter, large-sample RCTs are necessary to confirm these findings.</p>","authors":["Xiao Y","Chen J","Guo M","Liu X","Xu X","Liu Y","Jiang Z","Xu Y","Deng C."],"year":2025,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202604.1748.v1","title":"Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured Abundance","abstract":"Peptides are a rapidly expanding drug class with a parallel and largely unregulated gray market that sells preparations directly to consumers for self-administration. The use of gray market peptides has grown substantially, with patients self-administering these compounds for purported benefits including accelerated musculoskeletal injury recovery, muscle hypertrophy, fat loss, and athletic performance enhancement. The objective of this study was to evaluate the purity, measured abundance, and endotoxin burden of gray market research peptides using a large, publicly available independent testing dataset, and to compare their cost to compounded and FDA-approved alternatives. A total of 6441 peptide samples across fourteen compounds, including BPC-157, cagrilintide, CJC-1295, GHK-Cu, ipamorelin, PT-141, retatrutide, semaglutide, sermorelin, survodutide, TB-500, tesamorelin, thymosin beta-4, and tirzepatide, were analyzed. Two quality acceptance frameworks were applied: a model that approximated regulatory standards for 503A compounded medications, and a more conservative model that utilized regulatory standards often applied to the production of FDA approved peptide drugs. Between the two models, 41.6% to 71.1% of samples failed to meet basic quality criteria, and measurable endotoxin contamination was present in 15% of samples. Gray market compounds were consistently less expensive than FDA-approved peptides, but there were considerable differences in the cost differential. Compared with gray market preparations, the estimated cost of a clinically relevant treatment course for FDA-approved peptides was 72.8% higher for tirzepatide, and 3850% higher for PT-141. These findings indicate that many peptides used for sports medicine and performance-related purposes fail basic quality benchmarks. Further, consumer-directed third-party testing improves transparency, but captures only a small fraction of the safety profile relevant to patients self-administering injectable peptide preparations.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.07.05.25330933","title":"Differential effects of glucagon-like peptide-1 receptor agonist classes on blood pressure: a systematic review and network meta-analysis of randomised controlled trials with meta-regression","abstract":"<h4>Background and Aims: </h4> Recent clinical trials have reported blood pressure (BP)-lowering effects of glucagon-like peptide-1 receptor agonists (GLP1Ra). A recent systematic review has focused on the effects of semaglutide. However, there has been no comprehensive evaluation of the BP effects of all GLP1Ra available, including the double agonist tirzepatide and the triple agonist retatrutide. Additionally, the extent to which BP reduction is mediated by weight loss remains unclear. This systematic review and network meta-analysis aimed to evaluate the impact of GLP1Ra on systolic and diastolic BP across randomized controlled trials (RCTs). <h4>Methods:</h4> PubMed/MEDLINE, Web of Science and Ovid/Embase were searched from their inception until 31st July 2024. RCTs involving adult patients treated with GLP1Ra that reported BP and weight changes were included. Pair-wise meta-analysis and meta-regression models were utilised. Network meta-analysis was conducted. Mean difference (MD) and its 95% confidence intervals (CIs) were reported. <h4>Results:</h4> A total of 75 RCTs, including 114352 participants, were included. Retatrutide demonstrated the greatest reduction in systolic BP (MD: −7.0 mmHg; 95% CI: −10.5 to −3.5, followed by tirzepatide (MD: −5.2 mmHg; 95% CI: −6.9 to −3.5) and semaglutide (MD: −3.4 mmHg; 95% CI: −4.7 to −2.1). For diastolic BP, tirzepatide showed the largest reduction (MD: −1.7 mmHg; 95% CI: −2.6 to −0.8), followed by semaglutide (MD: −0.8 mmHg; 95% CI: −1.4 to −0.2). Mediation analysis indicated that weight loss partially mediated the BP-lowering effects of GLP1Ra. Conclusion: Retatrutide, tirzepatide and semaglutide reduced systolic blood pressure compared to placebo. Tirzepatide and semaglutide also led to significant diastolic BP reductions. The triple agonist retatrutide emerged as the most effective agent for lowering systolic BP among all GLP1Ra classes.","authors":["Chou OHI","Zhou H","Waraich H","Wu D","Razzaghi K","Chan JSK","Liu T","Cheung BM","Tse G","McEniery CM","Wilkinson IB."],"year":2025,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.04.17.649402","title":"Semaglutide, Tirzepatide, and Retatrutide Attenuate the Interoceptive Effects of Alcohol in Male and Female Rats","abstract":"<h4>Rationale</h4>  Alcohol use disorder (AUD) remains a major public health challenge, yet effective pharmacotherapies are limited. As such, there is growing interest in repurposing medications with novel mechanisms of action. Glucagon-like peptide-1 (GLP-1) receptor agonists, originally developed for type 2 diabetes, have emerged as promising candidates due to effects on intake regulation and reward processing. GLP-1 receptor agonists, including semaglutide, reduce alcohol intake and relapse-like behaviors in rodent and non-human primate models, and a recent clinical trial found that semaglutide decreased alcohol craving and drinking in adults with AUD. Modulation of the subjective/interoceptive effects of alcohol may contribute to the therapeutic potential of GLP-1 receptor agonists. <h4>Objectives</h4>  This study used operant drug discrimination in male and female rats to assess how acute and repeated semaglutide treatment affects alcohol’s discriminative stimulus (interoceptive) effects. We hypothesized that GLP-1 receptor activation would disrupt alcohol’s interoceptive effects. We also evaluated acute treatment with tirzepatide, a dual GLP-1/gastric inhibitory peptide (GIP) receptor agonist, and retatrutide, a triple GIP/GLP-1/glucagon receptor agonist, to determine whether broader receptor activity would differentially influence alcohol’s subjective effects. <h4>Results</h4>  Acute administration of semaglutide, tirzepatide, and retatrutide each attenuated alcohol discrimination, suggesting modulation of subjective alcohol effects. Repeated semaglutide maintained efficacy across the 15-day treatment period; alcohol discrimination returned to control levels three days after treatment cessation. <h4>Conclusions</h4>  Building on prior work with GLP-1 receptor agonists, these results provide important context for interpreting clinical observations of reduced drinking behavior among individuals receiving this class of therapeutics.","authors":["Windram M","Lovelock DF","Carew JM","Krieman CG","Hendershot CS","Besheer J."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"preprints":[{"pmid":"","doi":"10.21203/rs.3.rs-7103001/v1","title":"Efficacy and safety of retatrutide for overweight/obesity or type 2 diabetes: a systematic review and meta-analysis","abstract":"<title>Abstract</title>  <p>Aim To perform a meta-analysis to evaluate the efficacy and safety of retatrutide in patients with overweight/obesity and/or type 2 diabetes (T2D). Methods We systematically searched PubMed, Embase, Cochrane Library, Scopus, Web of Science, and ClinicalTrials.gov. Randomized controlled trials (RCTs) evaluating the efficacy and safety of retatrutide for overweight/obesity or T2D were included, with the date up to June 16, 2025. Outcomes were analysed using RevMan 5.4 and Stata 17.0. Weighted mean differences (WMDs) and risk ratios (RRs) were computed for continuous outcome variables and dichotomous data, respectively. Heterogeneity was assessed using the I² statistic. Results Retatrutide significantly reduced hemoglobin A1c (HbA1c) by 0.9% (95% CI: [-1.63, -0.17], P = 0.015), fasting blood glucose (FBG) by 21.87 mg/dL (95% CI: [-39.66, -4.09], P = 0.016), body weight by 10.66 kg (95% CI: [-17.64, -3.67], P = 0.003), and body mass index (BMI) by 4.55 kg/m<sup>2</sup> (95% CI: [-7.59, -1.51], P = 0.003). Additionally, retatrutide modestly reduced blood pressure and significantly reduced lipid profiles compared with placebo. However, treatment- emergent adverse events (TEAEs) and gastrointestinal adverse events, particularly nausea, vomiting, and constipation, were more frequent with retatrutide. Conclusions Retatrutide showed robust reductions in body weight and clinically meaningful improvements in glycemic control and cardiometabolic measures for patients with overweight/obesity and/or T2D. However, there was an increased risk of TEAEs, especially gastrointestinal adverse events. Further long-term, multicenter, large-sample RCTs are necessary to confirm these findings.</p>","authors":["Xiao Y","Chen J","Guo M","Liu X","Xu X","Liu Y","Jiang Z","Xu Y","Deng C."],"year":2025,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202604.1748.v1","title":"Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured Abundance","abstract":"Peptides are a rapidly expanding drug class with a parallel and largely unregulated gray market that sells preparations directly to consumers for self-administration. The use of gray market peptides has grown substantially, with patients self-administering these compounds for purported benefits including accelerated musculoskeletal injury recovery, muscle hypertrophy, fat loss, and athletic performance enhancement. The objective of this study was to evaluate the purity, measured abundance, and endotoxin burden of gray market research peptides using a large, publicly available independent testing dataset, and to compare their cost to compounded and FDA-approved alternatives. A total of 6441 peptide samples across fourteen compounds, including BPC-157, cagrilintide, CJC-1295, GHK-Cu, ipamorelin, PT-141, retatrutide, semaglutide, sermorelin, survodutide, TB-500, tesamorelin, thymosin beta-4, and tirzepatide, were analyzed. Two quality acceptance frameworks were applied: a model that approximated regulatory standards for 503A compounded medications, and a more conservative model that utilized regulatory standards often applied to the production of FDA approved peptide drugs. Between the two models, 41.6% to 71.1% of samples failed to meet basic quality criteria, and measurable endotoxin contamination was present in 15% of samples. Gray market compounds were consistently less expensive than FDA-approved peptides, but there were considerable differences in the cost differential. Compared with gray market preparations, the estimated cost of a clinically relevant treatment course for FDA-approved peptides was 72.8% higher for tirzepatide, and 3850% higher for PT-141. These findings indicate that many peptides used for sports medicine and performance-related purposes fail basic quality benchmarks. Further, consumer-directed third-party testing improves transparency, but captures only a small fraction of the safety profile relevant to patients self-administering injectable peptide preparations.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.07.05.25330933","title":"Differential effects of glucagon-like peptide-1 receptor agonist classes on blood pressure: a systematic review and network meta-analysis of randomised controlled trials with meta-regression","abstract":"<h4>Background and Aims: </h4> Recent clinical trials have reported blood pressure (BP)-lowering effects of glucagon-like peptide-1 receptor agonists (GLP1Ra). A recent systematic review has focused on the effects of semaglutide. However, there has been no comprehensive evaluation of the BP effects of all GLP1Ra available, including the double agonist tirzepatide and the triple agonist retatrutide. Additionally, the extent to which BP reduction is mediated by weight loss remains unclear. This systematic review and network meta-analysis aimed to evaluate the impact of GLP1Ra on systolic and diastolic BP across randomized controlled trials (RCTs). <h4>Methods:</h4> PubMed/MEDLINE, Web of Science and Ovid/Embase were searched from their inception until 31st July 2024. RCTs involving adult patients treated with GLP1Ra that reported BP and weight changes were included. Pair-wise meta-analysis and meta-regression models were utilised. Network meta-analysis was conducted. Mean difference (MD) and its 95% confidence intervals (CIs) were reported. <h4>Results:</h4> A total of 75 RCTs, including 114352 participants, were included. Retatrutide demonstrated the greatest reduction in systolic BP (MD: −7.0 mmHg; 95% CI: −10.5 to −3.5, followed by tirzepatide (MD: −5.2 mmHg; 95% CI: −6.9 to −3.5) and semaglutide (MD: −3.4 mmHg; 95% CI: −4.7 to −2.1). For diastolic BP, tirzepatide showed the largest reduction (MD: −1.7 mmHg; 95% CI: −2.6 to −0.8), followed by semaglutide (MD: −0.8 mmHg; 95% CI: −1.4 to −0.2). Mediation analysis indicated that weight loss partially mediated the BP-lowering effects of GLP1Ra. Conclusion: Retatrutide, tirzepatide and semaglutide reduced systolic blood pressure compared to placebo. Tirzepatide and semaglutide also led to significant diastolic BP reductions. The triple agonist retatrutide emerged as the most effective agent for lowering systolic BP among all GLP1Ra classes.","authors":["Chou OHI","Zhou H","Waraich H","Wu D","Razzaghi K","Chan JSK","Liu T","Cheung BM","Tse G","McEniery CM","Wilkinson IB."],"year":2025,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.04.17.649402","title":"Semaglutide, Tirzepatide, and Retatrutide Attenuate the Interoceptive Effects of Alcohol in Male and Female Rats","abstract":"<h4>Rationale</h4>  Alcohol use disorder (AUD) remains a major public health challenge, yet effective pharmacotherapies are limited. As such, there is growing interest in repurposing medications with novel mechanisms of action. Glucagon-like peptide-1 (GLP-1) receptor agonists, originally developed for type 2 diabetes, have emerged as promising candidates due to effects on intake regulation and reward processing. GLP-1 receptor agonists, including semaglutide, reduce alcohol intake and relapse-like behaviors in rodent and non-human primate models, and a recent clinical trial found that semaglutide decreased alcohol craving and drinking in adults with AUD. Modulation of the subjective/interoceptive effects of alcohol may contribute to the therapeutic potential of GLP-1 receptor agonists. <h4>Objectives</h4>  This study used operant drug discrimination in male and female rats to assess how acute and repeated semaglutide treatment affects alcohol’s discriminative stimulus (interoceptive) effects. We hypothesized that GLP-1 receptor activation would disrupt alcohol’s interoceptive effects. We also evaluated acute treatment with tirzepatide, a dual GLP-1/gastric inhibitory peptide (GIP) receptor agonist, and retatrutide, a triple GIP/GLP-1/glucagon receptor agonist, to determine whether broader receptor activity would differentially influence alcohol’s subjective effects. <h4>Results</h4>  Acute administration of semaglutide, tirzepatide, and retatrutide each attenuated alcohol discrimination, suggesting modulation of subjective alcohol effects. Repeated semaglutide maintained efficacy across the 15-day treatment period; alcohol discrimination returned to control levels three days after treatment cessation. <h4>Conclusions</h4>  Building on prior work with GLP-1 receptor agonists, these results provide important context for interpreting clinical observations of reduced drinking behavior among individuals receiving this class of therapeutics.","authors":["Windram M","Lovelock DF","Carew JM","Krieman CG","Hendershot CS","Besheer J."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"consensus_view":"The literature consensus is that retatrutide is a potent triple agonist with clinically meaningful superiority over GLP-1R monoagonists for weight loss, glycemic control, and hepatic steatosis reduction, with the glucagon receptor component contributing meaningfully to energy expenditure and hepatic lipid mobilization. There is general agreement that GCGR co-agonism is a valuable pharmacological feature distinguishing retatrutide from tirzepatide. However, the literature is exclusively clinical and pharmacological — there is no published consensus on the structural determinants of retatrutide's receptor selectivity profile, no SAR data on individual residue contributions to receptor binding or bias, and no precedent in this literature set for non-canonical amino acid substitutions in triple agonist peptides. The concept of 7-aza-tryptophan as a tool for class B GPCR ECD selectivity modulation has no direct literature support in this corpus.","knowledge_gaps":"Major knowledge gaps relevant to this hypothesis include: (1) No published crystal structures or cryo-EM structures of retatrutide bound to GCGR, GLP-1R, or GIPR, meaning the claim that Trp-25 contacts the ECD hydrophobic groove cannot be directly verified from available literature. (2) No published SAR studies on retatrutide's individual residue contributions to receptor binding affinity or selectivity — it is unknown from the literature whether position 25 is pharmacophoric for any of the three receptors. (3) No published data on 7-aza-tryptophan substitutions in class B GPCR-targeting peptides more broadly, leaving the electronic and H-bonding consequences at the receptor interface entirely predictive. (4) The comparative hydrophobicity of the ECD binding pockets of GCGR versus GLP-1R versus GIPR at the position corresponding to Trp-25 of retatrutide has not been characterized in any retrieved literature. (5) The downstream signaling consequences of partial GCGR bias (Gαs/cAMP vs. β-arrestin recruitment) in the context of triple agonism are not addressed. These gaps make the hypothesis novel and potentially illuminating but also structurally speculative given available literature.","supporting_evidence":"The strongest supporting evidence is indirect but coherent: (1) Multiple clinical studies (Sanyal et al. 2024, Jastreboff et al. 2023) demonstrate that GCGR engagement in retatrutide drives hepatic lipid mobilization and fat mass reduction, establishing that enhanced GCGR activity at the level of the hypothesis is pharmacologically meaningful and therapeutically valuable for the stated indication (hepatic lipid mobilization in obesity). (2) The mechanistic reviews (Katsi et al. 2025, Abdul-Rahman et al. 2024) explicitly attribute retatrutide's differentiation from GLP-1/GIP dual agonists to its glucagon receptor component, supporting the premise that selective GCGR enhancement within the triple agonist framework is a worthwhile pharmacological objective. (3) The body composition substudy (Coskun et al. 2025) shows preferential fat mass reduction over lean mass loss with retatrutide, an effect consistent with GCGR-mediated lipolysis, suggesting that further GCGR bias could amplify this metabolically favorable phenotype. (4) General class B GPCR structural biology (not directly represented in retrieved abstracts but well-established in the field) does support that the N-terminal helix of glucagon-family peptides engages the ECD hydrophobic groove and that residues at positions 22–26 of glucagon-like peptides modulate receptor selectivity — making position 25 a structurally plausible target for selectivity engineering.","challenging_evidence":"Several considerations complicate or challenge the hypothesis: (1) No retrieved paper addresses the molecular pharmacology of Trp-25 in retatrutide specifically, meaning the assumption that this residue is a selectivity determinant rather than a structural scaffold residue is unverified. (2) Glucagon receptor agonism raises legitimate safety concerns: excessive GCGR activation increases hepatic glucose output and can worsen hyperglycemia — the clinical data show that retatrutide's current GCGR activity is carefully balanced against GLP-1R-mediated insulinotropic effects. A GCGR-biased variant could disrupt this balance and produce hyperglycemic liability, a risk not discussed in the hypothesis. (3) The Drucker (2024) review notes that retatrutide and survodutide (a GLP-1/GCGR dual agonist) represent a specific strategy of pairing glucagon with GLP-1 activity precisely to counteract glucagon's glycemic risks — reinforcing that unbalanced GCGR enhancement is pharmacologically risky. (4) The 7-aza-Trp substitution's predicted preference for GCGR over GLP-1R/GIPR based on ECD pocket polarity is entirely computational/structural in premise and could be confounded by the dominant role of transmembrane domain interactions (rather than ECD contacts) in determining agonist efficacy and signaling bias for class B GPCRs. (5) The gray market peptide quality data (Mendias & Awan 2026) highlight that even unmodified retatrutide has variable purity in research-grade preparations, raising practical concerns about experimental reproducibility for modified analogs. (6) None of the retrieved literature provides any precedent for 7-aza-Trp substitution in any incretin or glucagon-family peptide, so the impact on overall peptide fold, proteolytic stability, or receptor docking geometry is entirely uncharacterized."},"caveats":null,"works_cited":[{"pmid_or_doi":"37366315","title":"Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial","year":2023,"relevance":"Establishes the clinical efficacy and dose-response profile of retatrutide as a triple GIP/GLP-1/GCGR agonist, providing the pharmacological baseline against which any selectivity-shifted analog (such as the proposed 7-aza-Trp variant) would need to be compared."},{"pmid_or_doi":"37385280","title":"Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial","year":2023,"relevance":"Confirms retatrutide's multi-receptor pharmacology and superior metabolic outcomes versus GLP-1R monoagonism, supporting the value of the GCGR component that the hypothesis seeks to selectively enhance."},{"pmid_or_doi":"38858523","title":"Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial","year":2024,"relevance":"Directly relevant: demonstrates profound hepatic lipid reduction with retatrutide, an effect attributed in part to GCGR-driven hepatic lipid mobilization, which is the precise metabolic outcome the hypothesis aims to augment via GCGR-biased selectivity."},{"pmid_or_doi":"40563436","title":"Retatrutide-A Game Changer in Obesity Pharmacotherapy","year":2025,"relevance":"Synthesizes preclinical and clinical mechanisms of retatrutide, explicitly attributing weight loss and liver fat reduction partly to glucagon receptor-mediated energy expenditure and hepatic lipid oxidation, supporting the therapeutic rationale for GCGR bias."},{"pmid_or_doi":"39515565","title":"The power of three: Retatrutide's role in modern obesity and diabetes therapy","year":2024,"relevance":"Describes the synergistic mechanism among retatrutide's three receptor targets and highlights glucagon receptor activation as a distinct contributor to metabolic outcomes, relevant to understanding consequences of shifting triple-agonist selectivity toward GCGR."},{"pmid_or_doi":"38843460","title":"Efficacy and Safety of GLP-1 Medicines for Type 2 Diabetes and Obesity","year":2024,"relevance":"Provides authoritative context on the pharmacological landscape of incretin-based therapies, distinguishing retatrutide's glucagon receptor co-agonism as a differentiating feature relevant to the selectivity-rebalancing hypothesis."},{"pmid_or_doi":"39318607","title":"Effects of once-weekly subcutaneous retatrutide on weight and metabolic markers: A systematic review and meta-analysis of randomized controlled trials","year":2024,"relevance":"Meta-analytic confirmation of retatrutide's metabolic efficacy, providing quantitative benchmarks for body weight and metabolic marker changes that a modified analog would need to be assessed against."},{"pmid_or_doi":"40609566","title":"Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2 trial","year":2025,"relevance":"Demonstrates retatrutide's preferential reduction of fat mass over lean mass, an outcome linked in part to GCGR-mediated lipolysis; relevant as a benchmark for evaluating whether GCGR-biased analogs preserve or enhance this body composition profile."},{"pmid_or_doi":"10.1101/2025.04.17.649402","title":"Semaglutide, Tirzepatide, and Retatrutide Attenuate the Interoceptive Effects of Alcohol in Male and Female Rats","year":2025,"relevance":"Preclinical data showing retatrutide's CNS pharmacological activity relative to mono- and dual agonists; provides indirect evidence that GCGR co-agonism may produce distinct CNS effects, though not directly relevant to the ECD structural hypothesis."},{"pmid_or_doi":"10.21203/rs.3.rs-7103001/v1","title":"Efficacy and safety of retatrutide for overweight/obesity or type 2 diabetes: a systematic review and meta-analysis","year":2025,"relevance":"Preprint meta-analysis confirming robust clinical efficacy across glycemic and lipid endpoints, useful for contextualizing the metabolic impact of GCGR engagement in the retatrutide pharmacological profile."}]},"onchain":{"hash":null,"signature":null,"data_hash":null,"logged_at":null,"explorer_url":null},"ipfs_hash":null,"created_at":"2026-05-04T14:59:07.544427+00:00","updated_at":"2026-05-04T15:03:53.091022+00:00"}