Discovery and Characterization of Potent Dual P‑Glycoprotein and CYP3A4 Inhibitors: Design, Synthesis, Cryo-EM Analysis, and Biological Evaluations

Targeted
concurrent inhibition of intestinal drug efflux transporter
P-glycoprotein (P-gp) and drug metabolizing enzyme cytochrome P450
3A4 (CYP3A4) is a promising approach to improve oral bioavailability
of their common substrates such as docetaxel, while avoiding side
effects arising from their pan inhibitions. Herein, we report the
discovery and characterization of potent small molecule inhibitors
of P-gp and CYP3A4 with encequidar (minimally absorbed P-gp inhibitor)
as a starting point for optimization. To aid in the design of these
dual inhibitors, we solved the high-resolution cryo-EM structure of
encequidar bound to human P-gp. The structure guided us to prudently
decorate the encequidar scaffold with CYP3A4 pharmacophores, leading
to the identification of several analogues with dual potency against
P-gp and CYP3A4. In vivo, dual P-gp and CYP3A4 inhibitor 3a improved the oral absorption of docetaxel by 3-fold as
compared to vehicle, while 3a itself remained poorly
absorbed.