Hypothalamic-Pituitary Autoimmunity in Patients Treated with Anti-PD-1 and Anti-PD-L1 Antibodies

Autoimmune hypophysitis is a frequent immune-related adverse event (irAE) in cancer patients treated with immunecheckpoint inhibitors. Studies seeking anti-pituitary (APA) and anti-hypothalamus (AHA) antibodies in patients treated with anti-PD-1 and anti-PD-L1 are scarce. The aim of this study is to search for APA and AHA and related pituitary dysfunction in patients treated with these agents.

Cross-sectional and preliminary longitudinal studies were conducted at the Medical Oncology Unit and Endocrinology and Metabolic Diseases Unit of the University of Campania "Luigi Vanvitelli". Fifty-four cancer patients on treatments with anti-PD-1 or anti-PD-L1 (Group 1) and 50 healthy controls were enrolled for a cross-sectional study; 13 cancer patients (Group 2) were enrolled for our preliminary longitudinal study. APA/AHA titers and changes in biochemical and hormonal profile were evaluated in Group 1; in Group 2, they were evaluated before and after nine weeks from the start of immunotherapy.

Patients of Group 1 showed a higher prevalence of APA and AHA than controls: 21 of them had APA, 16 had AHA, and 11 had both autoantibodies. In total, 7 of 13 patients in Group 2 became APA-positive and 3 became AHA-positive after nine weeks of immunotherapy, showing an increase in prolactin and a decrease in ACTH and IGF-1 levels compared with basal values.

Anti-pituitary and anti-hypothalamus antibodies seem to play a pivotal role in hypothalamic-pituitary autoimmunity and secondary endocrine-related alterations evoked by anti-PD-1 and PD-L1 antibodies.