Tumor Regression and Allograft Rejection after Administration of Anti–PD-1

Cancers, especially skin cancers, may develop in patients undergoing solid-organ transplantation who receive long-term immunosuppression. The use of anti–PD-1 in one such patient produced an antitumor response but led to rejection of the transplanted kidney. To the Editor: Although antibodies against the programmed death 1 (PD-1) receptor and one of its ligands (PD-L1) have produced tumor regressions in multiple cancer types, these therapies are untested in patients treated with long-term immunosuppressive medications. 1 Here, we report a case in which PD-1 antibody was administered to a solid-organ transplant recipient with metastatic cutaneous squamous-cell carcinoma. The patient had a robust antitumor response along with allograft rejection. This case suggests that anti–PD-1 can be highly effective against cancers arising in the context of chronic immunosuppression. It also suggests that the PD-1 pathway may be critical in maintaining the . . .