Pilot Trial of Arginine Deprivation plus Nivolumab and Ipilimumab in Patients with Metastatic Uveal Melanoma. Pilot Trial of Arginine Deprivation plus Nivolumab and Ipilimumab in Patients with Metastatic Uveal Melanoma

Metastatic uveal melanoma (UM) remains challenging to treat, with objective response rates to immune checkpoint blockade (ICB) much lower than in primary cutaneous melanoma (CM). Besides a lower mutational burden, the overall immune-excluded tumor microenvironment of UM might contribute to the poor response rate. We therefore aimed at targeting deficiency in argininosuccinate synthase 1, which is a key metabolic feature of UM. This study aimed at investigating safety and tolerability of a triple combination consisting of ipilimumab and nivolumab immunotherapy and the metabolic therapy ADI-PEG 20. 9 patients were enrolled in this pilot study. The combination therapy was safe and tolerable with absence of immune related adverse events (irAE) of special interest but with 4 of 9 patients experiencing a CTCAE grade 3 AE. No objective responses were observed. All except one patient developed anti-drug antibodies (ADA) within a month of treatment initiation and therefore did not maintain arginine depletion. Further, an IFNg-dependent inflammatory signature was observed in metastatic lesions in patients pre-treated with ICB compared with patients with no pretreatment. Multiplex immunohistochemistry demonstrated variable presence of tumor infiltrating CD8 lymphocytes and PD-L1 expression at baseline in metastases. Overall design: Patients with metastatic uveal melanoma with various pretreatments/first line were enrolled in this pilot clinical trial. Samples were collected at baseline.