Pegargiminase Suppresses the Fanconi Anemia Pathway and Promotes Melphalan-Induced DNA Double-Strand Breaks in Uveal Melanoma.

Uveal melanoma is a hard-to-treat arginine-dependent cancer secondary to argininosuccinate synthetase 1 (ASS1) loss with half of patients succumbing to liver-dominant metastases. Arginine deprivation with pegargiminase is a novel antimetabolite strategy for patients with uveal melanoma. We investigated the preclinical rationale for combining pegargiminase with melphalan, an alkylating agent approved recently for the treatment of hepatic-centric disease. Drug sensitivity of ASS1-deficient uveal melanoma cell lines was performed in 2D culture using proliferation and cytotoxicity assays, with analysis of cell death, cell cycle, DNA double-strand breaks, and interrogation of the molecular mechanism of action by RNA-seq. ADI-PEG20 and melphalan suppressed uveal melanoma cell line proliferation and triggered cytotoxicity, effects which were enhanced with the drug combination. ADI-PEG20 downregulated multiple genes of the Fanconi anemia pathway and synergized with melphalan to increase DNA double-strand breaks. Melphalan and pegargiminase is a rational new drug combination that warrants clinical testing in uveal melanoma.