Precision Obesity Medicine: Genetic Prediction of Response to GLP-1/GIP Agonists.

Registered clinical trial record on ClinicalTrials.gov (NCT07653412). This describes a planned, ongoing, or completed study — it is NOT peer-reviewed results. Status: recruiting. Study type: observational. Sponsor: National and Kapodistrian University of Athens. Conditions: Obesity (Disorder), Anti-obesity Agents, Precision Medicine. Interventions: Semaglutide or Tirzepatide. Summary: Obesity is a chronic multifactorial disease with a strong genetic component. Although glucagon-like peptide-1 (GLP-1) receptor agonists such as semaglutide and dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists, such as tirzepatide, are highly effective treatments for obesity, substantial inter-individual variability in weight loss response remains. Genetic factors may contribute to these differences in treatment outcomes. The aim of this prospective cohort study is to investigate whether a Genetic Risk Score (GRS) and selected obesity-related single nucleotide polymorphisms (SNPs) can predict weight loss response to semaglutide or tirzepatide in adults with obesity. Participants initiating treatment with either medication will undergo clinical, biochemical, and genetic assessment at baseline and will be followed for six months. The study will evaluate the association between genetic markers and treatment response and develop predictive models integrating genetic and clinical variables. The findings may contribute to the development of personalized treatment strategies for obesity. Obesity is a chronic disease resulting from complex interactions between genetic, environmental, and behavioral factors. Genetic influences account for a substantial proportion of obesity susceptibility, with heritability estimates ranging from 40% to 75%. Genome-wide association studies have identified numerous genetic variants associated with body mass index, appetite regulation, energy homeostasis, and metabolic function. Glucagon-like peptide-1 (GLP-1) receptor agonists and dual GIP/GLP-1 receptor agonists have significantly improved the pharmacological management of obesity. Semaglutide and tirzepatide produce clinically meaningful weight reduction and improvement in metabolic outcomes. However, treatment response varies considerably among individuals, and the factors underlying this variability are not fully understood. Genetic Risk Scores (GRS), which combine the effects of multiple obesity-related genetic variants, have emerged as potential tools for predicting disease risk and therapeutic response. Their role in predicting response to anti-obesity pharmacotherapy remains largely unexplored. This prospective observational cohort study aims to evaluate whether a GRS and selected obesity-related single nucleotide polymorphisms (SNPs) can predict weight loss response to semaglutide or tirzepatide in adults with obesity. Eligible participants initiating treatment with semaglutide or tirzepatide will be consecutively recruited and followed for six months. At baseline, demographic, clinical, anthropometric, biochemical, and genetic data will be collected. Approximately 18 obesity-related SNPs, including variants in genes involved in appetite regulation, energy balance, and glucose metabolism, will be analyzed. An additive Genetic Risk Score will be calculated based on the cumulative number of risk alleles. The primary outcome will be percentage weight loss at six months. Participants will subsequently be classified according to treatment response. Associations between genetic markers, GRS categories, and treatment outcomes will be evaluated using multivariable regression models. Receiver operating characteristic (ROC) curve analyses will be performed to assess the predictive performance of genetic and combined genetic-clinical models. The study is expected to identify genetic predictors of response to GLP-1/GIP receptor agonist therapy and contribute to the development of precision medicine approaches in obesity management. Improved prediction of treatment response may facilitate individualized therapeutic selection, optimize clinical outcomes, and reduce the trial-and-error approach currently used in obesity pharmacotherapy. Primary outcome measures: Percentage weight loss at 6 months. Eligibility: Inclusion Criteria: Age ≥18 years BMI ≥40 kg/m² or ≥37 kg/m² with comorbidities Initiation of semaglutide or tirzepatide Exclusion Criteria: Prior bariatric surgery Secondary causes of obesity Active malignancy Chronic pancreatitis Family history of medullary thyroid carcinoma