Discovery of Alternative Binding Poses through Fragment-Based Identification of DHODH Inhibitors

Abstract

Dihydroorotate dehydrogenase (DHODH) is a mitochondrial enzyme that affects many aspects essential to cell proliferation and survival. Recently, DHODH has been identified as a potential target for acute myeloid leukemia therapy. Herein, we describe the identification of potent DHODH inhibitors through a scaffold hopping approach emanating from a fragment screen followed by structure-based drug design to further improve the overall profile and reveal an unexpected novel binding mode. Additionally, these compounds had low P-gp efflux ratios, allowing for applications where exposure to the brain would be required.

Figure 1

Prior work progressing a virtual screening hit to lead 1.

Figure 2

Crystal structure of 2 (PDB entry 8VHM) and lead 1 (PDB entry 8DHG) bound to DHODH.

Scheme 1. Synthesis of Compounds: (a) Acid Chloride, Et₃N, DCM, −10 °C; (b) Phenyl Chloroformate, Pyridine, DCM, 0 °C to r.t., 12 h, 89%; (c) Et₃N, DCM, r.t.; (d) Isocyanatoethane, Et₃N, DCM, 0 to 40 °C, 12 h then DCE, 80 °C, 12 h, 16%; (e) AlMe₃, DCM, 10 to 60 °C, 12 h, 88%; (f) TBAF, THF, 15 °C, 1 h, 71%; (g) 10% Pd/C, EtOAc, 15 psi, 15 °C, 2 h, 66%

Figure 3

Crystal structure of 17 (PDB entry 8VHL) bound to DHODH.