FIT-039

**FIT-039** is a selective small molecule inhibitor of cyclin-dependent kinase 9 (CDK9), developed by researchers at Kyoto University. It binds competitively to the ATP-binding pocket of CDK9/cyclin T1 (IC50 5.8 μM), suppressing transcriptional elongation by inhibiting phosphorylation of the RNA polymerase II C-terminal domain, thereby preventing replication of multiple DNA viruses including HSV-1 (including acyclovir-resistant strains), HCMV, HAdV, HPV, KSHV, and HBV. Unlike broader CDK inhibitors like flavopiridol, FIT-039 exhibits minimal cytotoxicity, limited impact on host cell transcriptome and cell cycle, and good tolerability in preclinical rodent models (up to 1000 mg/kg oral daily) and early clinical trials. It has advanced to phase I/II trials for topical/transdermal treatment of common warts (verruca vulgaris caused by HPV) and transvaginal tablets for cervical intraepithelial neoplasia (CIN1/2), showing safety with mild, self-limiting adverse events like vaginal discharge.[1][2][3][5][7]

Other names

CIN Vaginal TabletKinoPharma CIN treatment