Single agent recombinant, pegylated ADI‐PEG20 (ADI; pegargiminase) has efficacy with low toxicity in clinical trials in ASS1‐deficient tumours including hepatocellular carcinoma (Glazer et al., 2010), mesothelioma (Szlosarek et al., 2017) and cutaneous melanoma (Ascierto et al., 2005; Feun et al., 2012). This evidence concerns the gene ASS1 and cutaneous melanoma.