HLA‐B27 association of autoimmune encephalitis induced by PD‐L1 inhibitor

OBJECTIVE: While immune checkpoint inhibitors are increasingly used for various cancers, unpredictable immune‐related adverse events (irAEs) such as autoimmune encephalitis is life‐threatening. Here, we report an association between human leukocyte antigen (HLA) and atezolizumab‐induced encephalitis. METHODS: From an institutional prospective cohort for encephalitis, we identified patients with autoimmune encephalitis after the use of atezolizumab, a PD‐L1 (programmed death‐ligand 1) inhibitor, from August 2016 to September 2019 and analyzed their HLA genotypes. RESULTS: A total of 290 patients received atezolizumab, and seven patients developed autoimmune encephalitis, and five of whom were enrolled for the analysis. The patients presented altered mentality, seizures, or myelitis. Three patients had the HLA‐B*27:05 genotype in common (60%), which is significantly frequent given its low frequency in the general population (2.5%). After Bonferroni correction, HLA‐B*27:05 was significantly associated with autoimmune encephalitis by atezolizumab (corrected P < 0.001, odds ratio 59, 95% CI = 9.0 ~ 386.9). INTERPRETATION: Here we found that three in five patients with autoimmune encephalitis associated with atezolizumab had the rare HLA‐B*27:05 genotype. Further systematic analyses in larger cohorts are necessary to investigate the value of HLA screening to prevent the life‐threatening adverse events.