THZ1 inhibits Jurkat cell and Loucy cell with IC50 of 50 nM, and 0.55 nM, respectively. THZ1 (9, 27, 83, 250, 750, and 2500 nM) inhibits CDK12 but at higher concentrations compared to CDK7. THZ1 (1 μM) irreversibly inhibits RNAPII CTD and CAK phosphorylation. THZ1 (2.5 µM) irreversibly inhibits RNAPII CTD phosphorylation by covalently targeting a unique cysteine located outside the kinase domain of CDK7 in Hela S3 cells. THZ1 (250 nM) causes decreased cellular proliferation and an increase in apoptotic index with concomitant reduction in anti-apoptotic proteins, most notably MCL-1 and XIAP in T-ALL cell lines.
All genotypically-distinct human (hSCLC) cell lines exhibit high sensitivity to THZ1, with an IC50 in the range of 5-20 nM.