AbstractPurpose:Androgen deprivation regenerates the thymus in adults, expanding of T-cell receptor V β repertoire in blood and lymphoid organs and tumor-infiltrating lymphocytes in human prostate tumors. In melanoma murine models, androgen receptor promotes metastases and androgen blockade potentiates antitumor vaccine efficacy. This phase I study evaluated the safety, efficacy, and pharmocodynamics of androgen deprivation with the gonadotropin releasing hormone (GnRH) agonist triptorelin combined with nivolumab in male patients with melanoma resistant to anti–PD-1.Patients and Methods:Adult male patients with advanced melanoma who progressed under anti–PD-1 containing regimens received triptorelin 3.75 mg every 4 weeks, nivolumab 3 mg/kg every 2 weeks, and bicalutamide 50 mg once daily during the first 28 days. Tumor response was first assessed after 3 months; adverse events (AE) were monitored throughout the study. T-cell receptor excision circles (TREC), a biomarker of thymus activity, were explored throughout the study.Results:Of 14 patients, 4 were locally advanced and 10 had distant metastases. There were no grade 4 or 5 AEs. Five grade three AEs were reported in 4 patients. According to RECIST v1.1, best overall response was partial response (PR) in one patient with a pancreas metastasis, stable disease (SD) in 5 patients, and progressive disease in 8 patients. According to iRECIST, a second PR occurred after an initial pseudoprogression, TRECs increased in 2 patients, one with PR who also had an increase in TILs, and the second with SD.Conclusions:This combination was well tolerated. Disease control was obtained in 42.8% (RECIST) and 50% (iRECIST). The evidence for thymus rejuvenation was limited.