Samuraciclib (CT7001) hydrochloride hydrate is a potent, selective, ATP-competitive and orally active CDK7 inhibitor, with an IC50 of 41 nM. Samuraciclib hydrochloride hydrate displays 45-, 15-, 230- and 30-fold selectivity over CDK1, CDK2 (IC50 of 578 nM), CDK5 and CDK9, respectively. Samuraciclib hydrochloride hydrate inhibits the growth of breast cancer cell lines with GI50 values between 0.2-0.3 µM. Samuraciclib hydrochloride hydrate has anti-tumor effects.