THZ531 is a covalent inhibitor of both CDK12(IC50=158 nM) and CDK13(IC50=69 nM).

In Jurkat cell, THZ531(IC50=50 nM) treatment leads to a dramatic and irreversible decrease proliferation.THZ531 potently inhibits CDK12(IC50=158 nM) and CDK13 (IC50=69 nM).

Cells are treated with THZ531 for 6 hours.After treatment cells are washed 2-fold with cold PBS and then lysed in the following lysis buffer: Hepes(50 mM, pH 7.4), NaCl（150 mM）, 1% Nonidet P40 substitute, EDTA（5 mM）, DTT（1 mM）, and protease/phosphatase cocktails.Lysates are treated with bio-THZ1 or bio-TH531 for pulldown overnight at 4°C.

Jurkat cells are plated in 96-well plates at 20,000 cells/well in fresh media and treated with THZ531 or DMSO at the indicated concentrations for 72 hours. HAP1 cells are seeded in 96-well plates at 12,000 cells/well in fresh media and 24 hours later are treated with THZ531 at the indicated concentrations for 72 hours. Anti-proliferative effect of THZ531 is assessed. To assess the effect of inhibitor washout on anti-proliferation of Jurkat cells, cells are treated with THZ531 or DMSO for 6 hrs. Inhibitor-containing medium is then removed and incubated with or without THZ531 for 66 hrs. Anti-proliferative effect of THZ531 is assessed. All proliferation assays are performed in biological triplicate. IC50s are determined using non-linear regression curve fit.