A Million Veteran Program preprint on medRxiv ↗ reports that the GLP-1 receptor gene (GLP1R), the molecular target of semaglutide ↗, tirzepatide ↗, and the rest of the obesity-drug class, has at least two independent genetic variants that each raise body mass index, and that the two variants have different effects on type 2 diabetes risk. The result has implications for how the field thinks about pharmacogenomic variation at this target.
The data. 431,107 participants of genetically inferred European ancestry from the Million Veteran Program, an active research cohort drawn from the US Veterans Affairs healthcare system. The analysis focused on a 1-megabase window centered on GLP1R, with conditional analyses to identify independent sentinel variants. Bayesian fine-mapping was used to construct credible sets of variants likely to be causal. Both BMI and T2D outcomes were modeled, controlling for age, sex, and ten principal components.
The two variants. The primary sentinel is rs12213929, located upstream of GLP1R, with each copy of the risk allele associated with a 0.11 kg/m² higher BMI (95% CI 0.09-0.14, p = 1.94×10⁻¹⁷). The secondary sentinel, rs13216992, is in an intron of GLP1R, with each copy associated with a 0.10 kg/m² BMI increase (95% CI 0.07-0.13, p = 7.88×10⁻¹⁴). The two are in low linkage disequilibrium (r² = 0.03), the technical statement that they are not just two markers of the same underlying variant. They are independent. A four-allele dose score (0-4 risk alleles across both variants) tracks linearly with BMI: participants with all four risk alleles have 0.47 kg/m² higher BMI than those with none.
The diabetes layer. Both variants associate with higher T2D risk, but the two associations behave differently when adjusted for BMI. The rs12213929-T2D association persists after BMI adjustment (OR 1.02, 95% CI 1.01-1.03, p = 0.0004), meaning the variant influences diabetes through pathways that are not entirely explained by weight. The rs13216992-T2D association is fully attenuated by BMI adjustment (OR 1.00, 95% CI 0.99-1.01, p = 0.68), meaning that variant's diabetes effect runs entirely through adiposity. Same gene, two independent variants, two different mechanisms.
Why this matters for the drug class. GLP-1 receptor agonists are designed to bind and activate the GLP-1 receptor as a single pharmacological target. The genetic data say the receptor's natural variation produces two independent metabolic phenotypes, and those phenotypes have different mechanistic relationships to diabetes. If the same heterogeneity exists at the level of drug response (which is the open pharmacogenomic question), patients carrying different combinations of these variants may respond to GLP-1 receptor agonists in qualitatively different ways. Some patients may be receptor-modulated through weight loss alone; others may have a BMI-independent receptor pathway that GLP-1 drugs also engage.
The fine-mapping result. The 95% credible set for BMI contains 17 variants. The 95% credible set for T2D contains 42 variants. All 17 BMI variants are inside the 42-variant T2D set. That nested structure is consistent with the hypothesis that BMI-acting variants are a subset of T2D-acting variants, which is what the conditional analyses already suggested. The fine-mapping refines the search space for functional follow-up and gives the laboratory side of the field a smaller list of candidates for direct experimental work.
The pharmacogenomic frontier. The April 30 peptide news digest noted a separate Stanford-led Genome Medicine paper identifying PAM-enzyme variants that may explain why approximately one in ten people get a weaker glycemic response to incretin drugs. The Million Veteran preprint adds a parallel finding at the GLP-1R locus itself: not whether the body processes incretin signals well, but whether the receptor variant determines which kind of metabolic phenotype the patient has at baseline. Both lines of work point at the same near-term application: identifying patient subgroups in whom GLP-1 drug response is predictably different.
What this is not. A medRxiv preprint, not yet peer-reviewed. The Million Veteran cohort is overwhelmingly male and middle-aged-or-older European-ancestry; generalization to other ancestry groups and to younger or female populations is the standard caveat. Effect sizes are small in absolute terms (0.11 kg/m² per allele is real but modest at the individual level), and the practical pharmacogenomic translation requires demonstration that the variants predict drug response rather than just baseline phenotype. The next step the authors flag is functional and pharmacogenomic follow-up to test whether GLP1R variation can inform precision prevention and treatment.
The platform read. The GLP-1R target page ↗ currently anchors the platform's metabolic-disease corner. The genetic-architecture finding does not change which peptide candidates are useful designs against the receptor, but it does add a layer of patient-stratification context that pharmacogenomic scaffolds in future cards may want to reference. As the field's GLP-1 secondary-effects literature continues to expand into psychiatric, ocular, kidney, and now genetic-architecture domains, the receptor's clinical relevance keeps widening relative to its original glycemic-control role.