PDCD1 and melanoma: In a 2021 Australian study, plasma DNA from patients with advanced melanoma who were treated with anti-PD-1 antibodies (nivolumab or pembrolizumab) was analysed for five specific PD-1 SNPs: PD1.1 (rs36084323, G>A), PD1.3 (rs11568821, G>A), PD1.5 (rs2227981, C>T), PD1.6 (rs10204225, G>A), and PD1.9 (rs2227982, C>T).