CYT01B

CYT01B is a small molecule inhibitor of the homologous recombination factor RAD51, developed by Cyteir Therapeutics. The compound is designed to exploit a synthetic lethal vulnerability in cancer cells that overexpress Activation-Induced Cytidine Deaminase (AID). AID is an enzyme that induces DNA damage through cytidine deamination; while essential for antibody diversity in B-cells, its ectopic expression in various solid tumors and lymphomas creates a critical dependency on RAD51-mediated DNA repair. By inhibiting RAD51, CYT01B prevents the repair of these double-strand breaks, selectively inducing apoptosis in AID-positive malignant cells. Preclinical data presented at AACR 2019 demonstrated its efficacy in models of breast, lung, pancreatic, and other solid cancers, as well as lymphoma. Development of the program was overseen by Cyteir Therapeutics until the company's liquidation in 2023.