Post-hoc analyzes of two phase 2 trials associate letaltortide with changes in fatty acid oxidation, insulin resistance biomarkers, and lipid metabolism, providing new clues about how triple receptor drugs can improve cardiometabolic health.
Study: Retatortide, lipid, and metabolite profiles in obese participants with and without type 2 diabetes. Image credit: khomkrit sunkatechon / Shutterstock
Recent research published in Journal of Clinical Endocrinology and Metabolism Retatrutide treatment was shown to alter metabolites associated with insulin resistance and fatty acid oxidation (FAO) in obese patients with and without type 2 diabetes (T2D). These changes were consistent with improved metabolic health. This finding supports further large-scale investigations into the use of letaltortide to improve overall health in people with commonly observed comorbidities such as obesity and T2D. If validated in subsequent trials in different populations, such therapies could help reduce the burden of cardiometabolic disease and improve the overall quality of life of patients worldwide.
Retatortide is a synthetic drug that acts on multiple receptors simultaneously. This drug may modulate blood sugar levels and energy balance by acting simultaneously on glucagon-like peptide-1 (GLP-1), glucagon (GCG), and glucose-dependent insulinotropic polypeptide (GIP) receptors. Scientists are studying the effects of letartortide in treating obesity and T2D. In a phase 2 clinical trial, the drug improved body weight, body fat, and glycated hemoglobin (HbA1c) levels in obese patients with and without T2D. Participants also showed almost complete removal of liver fat in the previous MASLD substudy, as well as reductions in waist circumference, blood pressure, fasting blood sugar, and insulin levels. Retaltortide is generally well tolerated and no significant safety concerns have been reported.
Phase 2 trial metabolomics analysis
In this study, researchers conducted a post hoc exploratory analysis to measure changes in the fasting plasma lipidome and metabolome in letatoltide recipients. They also investigated the biochemical changes underlying the participants’ metabolic changes.
This study analyzed fasting plasma samples from two previously conducted phase 2 randomized controlled trials (RCTs). These trials included individuals living with obesity, with or without T2D. The obesity study included individuals with a body mass index (BMI) between 27 and 30 kg m-2 with at least one weight-related disease and a BMI ≥30 kg m-2. In this study, participants received letaltortide (1.0 mg, 4.0 mg, 8.0 mg, 12 mg) or a placebo subcutaneously once a week for 48 weeks.
The T2D study included individuals with HbA1c between 7.0 and 10.5% and BMI between 25 and 50 kg m-². These patients were treated with metformin or diet and exercise for at least 3.0 months before the study. Participants received weekly subcutaneous injections of 0.5 mg, 4.0 mg, 8.0 mg, or 12 mg of letaltortide, placebo, or 1.5 mg of dulaglutide for 36 weeks.
The post hoc analysis included 282 obesity trial participants and 213 patients with T2D. Researchers collected samples from participants in the obesity trial at the start of the study, at 24 weeks, and at 48 weeks. Sample collection time points were baseline, week 24, and week 36 for T2D study participants. The research team performed liquid chromatography tandem mass spectrometry (LC-MS/MS) to monitor metabolic and lipidomic changes after retatortide therapy. They used mixed models for statistical analysis. They also performed mediation analyzes to assess the contribution of treatment to the observed changes.
Fatty acid oxidation and insulin resistance
High doses of retatortide resulted in changes in metabolite concentrations. Researchers noted significant changes in acetylcarnitine (C2), 3-hydroxybutyric acid (3-HB), medium- and long-chain acylcarnitines (AC), and free carnitine (C0). A key player in mitochondrial fatty acid metabolism, they work together to shuttle, process, and regulate fatty acids for energy production. C2 and 3-HB increased and C0 decreased, while several medium- and long-chain acylcarnitines increased initially and FAO-related responses were attenuated by 48 weeks. Joint changes in 3-HB and C2/C0 ratio accounted for approximately 23% of the weight loss treatment effect in participants without T2D. In T2D patients, the effect was weaker, less than 13%.
Retatortide treatment also resulted in changes in branched chain amino acids (BCAAs) and their catabolites, which are associated with insulin resistance. The drug reduced levels of 2-aminoadipic acid (2-AAA), short- and saturated-chain fatty acid-rich triglycerides (TG), and uric acid in both study populations, but 2-hydroxybutyrate (2-HB) levels were reduced more strongly in the T2D cohort and primarily by week 48 in the obesity study.
At 24 weeks, participants in the obesity trial showed dose-dependent metabolic changes. The researchers observed a significant increase in 3-HB of nearly 198% and C2/C0 ratio of 95% at the 12 mg dose in these participants. Valine and alanine levels were significantly reduced. By week 48, FAO-related responses had weakened, but metabolic changes associated with insulin resistance persisted. In T2D participants, the decrease in BCAAs was comparable to that observed in the obese cohort, but the increases in 3-HB and C2/C0 ratio were much smaller.
Retatortide treatment was also associated with reduced levels of the inflammatory marker 2,3-dinor-11β-PGF2α in the T2D cohort where lipid mediators were analyzed. This reduction was sustained for 36 weeks in the 8 mg and 12 mg dose groups. In parallel, levels of the PPARγ agonist 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) increased by approximately 40% at week 36 with both high-dose regimens.
Retatortide biomarker findings require validation
Study results demonstrate that letaltortide treatment alters metabolites associated with insulin resistance and fatty acid oxidation in a manner consistent with improved metabolic health and a reduced cardiovascular risk profile based on changes in biomarkers, rather than demonstrating a reduction in cardiovascular events.
Although these findings link the previously reported robust clinical outcomes to the underlying biochemical mechanisms, post-hoc exploratory analyzes remain hypothesis-generating and do not prove causality.
Future studies should determine whether the metabolic effects of letaltortide arise from direct tissue effects or from secondary weight loss mechanisms. Researchers should also investigate potential benefits such as cardiovascular, neuroprotective, and bariatric surgery as hypotheses for future studies.
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