Multi-Ancestry Genome-wide Association Analyses Identify Shared and Specific Genetic Architecture in Mild and Moderate-to-Severe Asthma

Background: Moderate-to-severe asthma affects 15-30% of asthma patients, but accounts for over 50% of healthcare costs and disproportionate morbidity. However, the genetic mechanisms underlying moderate-to-severe versus mild asthma remain poorly understood. Methods: We performed separate pooled multi-ancestry GWAS of mild (N = 14,372) and moderate-to-severe asthma (N = 7,096) versus non-asthma controls (N = 28,816) among adult participants in the NIH All of Us Research Program (version 8). European, African, and Latino/admixed ancestry-specific GWAS were combined using fixed-effect meta-analysis. Lung expression quantitative trait loci (eQTL) and pathway analyses were performed to identify candidate genes and biological pathways across asthma phenotypes. Results: Mild and moderate-to-severe asthma shared susceptibility loci at IL1RL1, IKZF3, and the GTF3AP1-IL33, GTF3AP1-RANBP6, LINC02757-EMSY and HLA-DRB1-HLA-DQA1 regions. Shared lung eQTLs implicated IL18R1, IL18RAP, HLA genes, IL33, LRRC32, GRB7, MIEN1 and GSDMB. In contrast, the phenotypes exhibited distinct genetic architectures. Mild asthma was characterized by broader HLA class II signals and associations at SMAD3 and GSDMB, with enrichment of antigen presentation, T-helper cell differentiation, and TGF-β regulation, consistent with adaptive immune mechanisms. Moderate-to-severe asthma was characterized by WDR36 and PTCH1, with lung eQTLs implicating TSLP, CAMK4, and FANCC. Pathway analysis identified enrichment of IL-13, IL-6, and IL-10 production, myeloid leukocyte differentiation, and oxidative stress responses, consistent with innate inflammation and pathways implicated in steroid resistance. The IL33 signals showed a severity-gradient effect, with stronger associations in moderate-to-severe asthma. Conclusion: Mild and moderate-to-severe asthma exhibit shared and distinct genetic architectures that support existing biologic targets and suggest novel therapeutic candidates.