Genetic drivers of severe skin toxicity with immune checkpoint inhibitors (ICIs) in Asian patients.

2667 Background: ICIs may cause severe skin toxicity associated with significant patient (pt) impact. Published data suggests Asian pts might be at higher risk of skin immune-related adverse events (SirAEs). Variation in human leukocyte antigen (HLA) is known to predispose to autoimmune (AI) conditions, but there is limited data to understand genetic drivers of severe SirAEs. Methods: The incidence of severe SirAEs was correlated with 30 HLA alleles of interest in 2 cohorts totaling 18 Asian pts (Dermatitis bullous n=4, Erythema multiforme n=10, Stevens-Johnson syndrome n=3, Toxic skin eruption n=1) treated with atezolizumab (A) across tumor types as monotherapy or as part of combinations- 8 Japanese pts received A in a non-interventional study (trial ID: UMIN000048702) and 10 Asian pts were enrolled in Roche trials with A. Data from the 18 cases was compared to 3 different controls of Asian pts identified from Roche trials with A (i.e. pts without any irAEs n=148, pts without SirAEs n=225, pts without severe SirAEs n=390). For each HLA allele, positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity, (unadjusted) odds ratio (OR) and corresponding 95%-confidence interval (CI) were evaluated. Case-control populations were obtained by risk-set sampling with exact matching on indication, treatment arm and sex, and used in age-adjusted conditional logistic regression models to assess associations between each HLA allele and severe SirAEs. Results: There was an association between some HLA alleles and severe SirAEs, but sensitivity was low (<30%) and 1-NPV was only slightly smaller than background prevalence. Results for five HLA alleles with OR>1.5 in either the unadjusted or adjusted analysis compared to controls without severe SirAEs are presented in table. Results were consistent across the three control populations. Conclusions: Five HLA alleles previously reported in AI disorders were associated with severe SirAEs in Asian pts receiving A. Although the effect size is insufficient to be considered clinically relevant, further research is warranted to better characterize the pt-level drivers of severe SirAEs in Asians pts. Clinical trial information: UMIN000048702 . [Table: see text]