hCYP3A4-IN-1 (compound C6) is a potent, orally active hCYP3A4 inhibitor. hCYP3A4-IN-1 shows the IC 50 values of 43.93 nM and 153.00 nM against hCYP3A4 in human liver microsomes (HLMs) and CHO-3A4 stably transfected cell line, respectively. hCYP3A4-IN-1 potently inhibits CYP3A4-catalyzed N-ethyl-1,8-naphthalimide (NEN) hydroxylation in a competitive manner (Ki = 30.00 nM).