Immune checkpoint inhibitor-induced diabetes mellitus (ICI-DM) is a rare irAE that typically presents with acute onset and often requires lifelong insulin therapy.[2] Serplulimab, a programmed cell death protein 1 (PD-1) inhibitor, has been approved for the treatment of various cancers, including SCLC and non-small cell lung cancer. Here, PDCD1 is linked to diabetes mellitus.