Severe immune-related adverse events in anti-PD-1-treated patients are clustered into distinct subtypes by peripheral blood T-cell profiles.

Abstract

2564 Background: Although anti-programmed death-1 (PD-1) treatment has shown remarkable anti-tumor efficacy, immune-related adverse events (irAEs) develop with heterogeneous clinical manifestations. Immunological understanding of irAEs is currently limited. In the present study, we analyzed peripheral blood T cells obtained from cancer patients who received anti-PD-1 treatment to determine the immunological characteristics of severe irAEs. Methods: This study included 31 patients with refractorythymic epithelial tumor (TET) who were enrolled in a phase II trial of pembrolizumab (NCT02607631) and 60 patients with metastatic non-small cell lung cancer (NSCLC) who received pembrolizumab or nivolumab. T-cell profiling was performed by multi-color flow cytometry using peripheral blood obtained immediately before treatment and 7 days after the first dose of anti-PD-1 antibodies. Results: Severe irAEs (≥ grade 3) occurred in 7 TET patients (22.6%) and 6 NSCLC patients (10.0%). Patients with severe irAEs exhibited a significantly lower fold increase in the frequency of effector regulatory T (eTreg) cells after anti-PD-1 treatment, higher ratio of T helper-17 (Th17) and T helper-1 cells at baseline, and higher percentage of Ki-67+cells among PD-1+CD8+T cells post-treatment. In clustering analysis, patients with severe irAEs were grouped into four distinct subtypes: Th17-related, TNF-related,Treg-related, and CD8-related. Conclusions: Severe irAEs after anti-PD-1 treatment were clustered into four immunological subtypes, indicating that development of severe irAEs is not attributed to a single mechanism. Further investigations in larger cohorts are needed to validate our current findings.