Sintilimab-Induced Autoimmune Diabetes in a Patient With the Anti-tumor Effect of Partial Regression

CONTEXT: Immune checkpoint blockades (ICBs) have been approved widely to treat various malignancies. Autoimmune diabetes mellitus, which can be caused by programmed cell death protein 1 (PD-1) inhibitors, is rare. Sintilimab, a monoclonal anti-PD-1 antibody, has been approved in China for the treatment of Hodgkin’s lymphoma and was used in our clinical trial for patients with unresectable hepatocellular carcinoma (HCC). CASE PRESENTATION: We present the first case of autoimmune diabetes during Sintilimab treatment in a patient with unresectable HCC, accompanied by a remarkable anti-tumor effect of partial regression. A 56-year-old male with typical symptoms presented with diabetic ketoacidosis (DKA) at 24 weeks after Sintilimab initiation. His fasting plasma glucose level was 22.2 mmol/L, HbA1c was 7.8%, fasting insulin was 1.5 mIU/L, and fasting C-peptide was 1.12 ng/mL, which further decreased to 0.21 ng/mL 4 days later. The patient was diagnosed with new-onset diabetes mellitus using the oral glucose tolerance test. The anti-glutamic acid decarboxylase 65 antibody, anti-islet cell antibody, and anti-insulin antibody tests were all negative. For the type 1 diabetes-associated alleles of human leukocyte antigen (HLA) class I and II, the most relevant type was identified as HLA-A(∗)0201. A diagnosis of PD-1 inhibitor-induced autoimmune diabetes was made. After rectification of DKA, he was treated with insulin therapy daily, which has since controlled his plasma glucose well. Thereafter, Sintilimab was been continued with sustained therapeutic effect. CONCLUSION: Due to unpredictability of this rare immune related adverse event (irAE), diabetes-related autoantibodies and C-peptide are recommended to be tested before immunotherapy, and plasma glucose monitoring should be performed. After plasma glucose is well controlled using insulin therapy, PD-1 inhibitor treatment might be continued, especially when the immunotherapy is effective.