In Vitro: CDK9-IN-18 (compound 12i) (0-20 μM, 3 hours; NH2 cells) suppress both HIV-1 transcription and the phosphorylation at Serine 2 of the RNAPII CTD in a dose-dependent manner. CDK9-IN-18 (compound 12i) (0-5.0 μM, 24 hours; human tumor cell lines) exerts antiproliferative effect through the induction of apoptosis in HepG2 cells.