The UV potentiated mutational signature of clinical stage G-quadruplex binder CX5461

Abstract Drug-related UVA-induced photoreactions have been reported for several therapeutic compounds, including fluoroquinolones. CX5461 is a clinically relevant quinolone-derived anti-cancer small molecule with documented UVA-sensitising activity. Here we compared, by bulk and clonal whole genome sequencing (WGS) under light-protected conditions, the mutational signatures in human retinal pigment epithelial cells (RPE1) exposed to UVA, CX5461, or co-exposed to UVA and CX5461. Treatment with CX5461 or UVA alone resulted in a low SNV burden and background-like mutational profiles. In contrast, bulk sequencing of human cells co-exposed to UVA and CX5461 had a markedly higher SNV burden characterized by T>A and T>C substitutions. Furthermore, single-cell clonal expansion and sequencing of CX5461 alone, UVA alone or CX5461+UVA treatments confirmed that the pattern was only observed when cells were exposed to both UVA and CX5461. The CX5461+UVA-associated SNV signature we report arises only when CX5461-treated cells are exposed to UVA, and is not observed when CX5461-treated cells are shielded from light. We do not observe strong single base mutagenic activity of CX5461 alone, under light protected conditions. Our data emphasise the need for appropriate controls and light-exposure precautions when studying base mutagenesis activity of known photosensitiser molecules. Competing Interest Statement John Hilton: Consulting: Merck, AZ, Novartis, Pfizer, Lilly, BMS; Research Funds: GSK,Lilly; DMC Committees: BMS. Karen Gelmon: Consulting/Advisory: AstraZeneca,Pfizer, Novartis, Lilly, Mylan, Merck, Gilead, Roche, Ayala, Nanostring, Genomic Health.Expert Testimony: Genentech. Research Funding: AstraZeneca, Pfizer, BMS, Roche. Lesley Seymour: Research support to CCTG from Senhwa Biosciences for IND231. Samuel Aparici: SAp is a cofounder of Genome Therapeutics Ltd. Funding: SAp is supported by Canada Research Chairs Program, Canada Foundation for Innovation.Work supported by StandUptoCancer, BC Cancer Foundation, Canadian CancerResearch Society, Canada Institutes for Health Research. David Cescon: Consulting/Advisory: AstraZeneca, Eisai, Exact Sciences, Gilead, GlaxoSmithKline, Merck, Novartis,Pfizer, and Roche. Research funding to institutions: AstraZeneca, Gilead, GlaxoSmithKline,Inivata, Merck, Pfizer, and Roche. Patent (US62/675,228) for methods of treating cancers characterized by a high expression level of spindle and kinetochore associated complex subunit 3 (ska3) gene. All other authors declare no potential conflicts of interest.