Immune Thrombocytopenia—A Neglected Adverse Event of PD-1 and PD-L1 Inhibitors in Clinical Trials

To the Editor In a systematic review and meta-analysis, Wang et al¹ investigated the incidence of treatment-related adverse events (AEs) associated with programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) inhibitors in clinical trials. They reported that the incidence of all-grade AEs was 66% (12 277 of 18 610 patients), with fatigue, pruritus, and diarrhea most commonly reported. Fatigue, anemia, and elevated levels of aspartate aminotransferase were the most common AEs with a grade of 3 or higher. For immune-related AEs (irAEs), the authors mainly described endocrine disorders that had aroused concern in recent years. Although this study represented the largest and most comprehensive overview regarding AEs associated with PD-1 and PD-L1 inhibitors, questions regarding the development and management of irAEs remain unanswered.² Notably, the hematological irAEs were not fully reported; immune thrombocytopenia, in particular, should not be neglected because of its potentially life-threatening risks.