Structure–Activity Relationship Studies of Antimalarial <i>Plasmodium</i> Proteasome Inhibitors─Part II
Hao Zhang, John D. Ginn, Wenhu Zhan, Annie Leung, Yi J. Liu, Akinori Toita, Rei Okamoto, Tzu‐Tshin Wong, Toshihiro Imaeda, Ryoma Hara, Mayako Michino, Takafumi Yukawa, Sevil Chelebieva, Patrick K. Tumwebaze, Jérémie Vendôme, Thijs Beuming, Kenjiro Sato, Kazuyoshi Aso, Philip J. Rosenthal, Roland A. Cooper, Nigel J. Liverton, Michael A. Foley, Peter T. Meinke, Carl Nathan, Laura A. Kirkman, Gang Lin
Abstract
With increasing reports of resistance to artemisinins and artemisinin-combination therapies, targeting the Plasmodium proteasome is a promising strategy for antimalarial development. We recently reported a highly selective Plasmodium falciparum proteasome inhibitor with anti-malarial activity in the humanized mouse model. To balance the permeability of the series of macrocycles with other drug-like properties, we conducted further structure–activity relationship studies on a biphenyl ether-tethered macrocyclic scaffold. Extensive SAR studies around the P1, P3, and P5 groups and peptide backbone identified compound TDI-8414. TDI-8414 showed nanomolar antiparasitic activity, no toxicity to HepG2 cells, high selectivity against the Plasmodium proteasome over the human constitutive proteasome and immunoproteasome, improved solubility and PAMPA permeability, and enhanced metabolic stability in microsomes and plasma of both humans and mice.