John F.X. Diffley

John F.X. Diffley is a world authority on DNA replication and replication stress biology at the Francis Crick Institute, London. His laboratory has provided foundational mechanistic understanding of how cells license and initiate DNA replication, how replication stress checkpoints are activated, and how cancer cells become uniquely dependent on the ATR-CHK1-WEE1 replication checkpoint axis due to elevated oncogene-driven replication stress. These insights have been instrumental in establishing the scientific rationale for ATR inhibitors (berzosertib, ceralasertib, elimusertib), WEE1 inhibitors (adavosertib), and CHK1 inhibitors as selective cancer therapeutic strategies — exploiting the synthetic lethal relationship between high replication stress in tumor cells and checkpoint inhibition. Diffley's biochemical reconstitution of the eukaryotic replication machinery (CMG helicase assembly, origin firing) using purified components has also enabled high-throughput drug screening assays against replication initiation components including CDC7/DDK, a clinically pursued target. His work on replication fork stability, PCNA modification, and the interplay between replication and transcription has clarified mechanisms of genome instability that underlie carcinogenesis and inform therapeutic vulnerability. He is an elected Fellow of the Royal Society and has received the Royal Society Croonian Medal.