Targeting Acute Myelogenous Leukemia Using Potent Human Dihydroorotate Dehydrogenase Inhibitors Based on the 2-Hydroxypyrazolo[1,5-a]pyridine Scaffold: SAR of the Aryloxyaryl Moiety

Abstract

In recent years, human dihydroorotate dehydrogenase inhibitors have been associated with acute myelogenous leukemia as well as studied as potent host targeting antivirals. Starting from MEDS433 (IC50 1.2 nM), we kept improving the structure–activity relationship of this class of compounds characterized by 2-hydroxypyrazolo­[1,5-a]­pyridine scaffold. Using an in silico/crystallography supported design, we identified compound 4 (IC50 7.2 nM), characterized by the presence of a decorated aryloxyaryl moiety that replaced the biphenyl scaffold, with potent inhibition and pro-differentiating abilities on AML THP1 cells (EC50 74 nM), superior to those of brequinar (EC50 249 nM) and boosted when in combination with dipyridamole. Finally, compound 4 has an extremely low cytotoxicity on non-AML cells as well as MEDS433; it has shown a significant antileukemic activity in vivo in a xenograft mouse model of AML.

Biochemical characterization of Mycobacterium tuberculosis dihydroorotate dehydrogenase and identification of a selective inhibitor

“…MEDS322, whose synthesis is described below and in the Scheme 1, inhibits Mt DHODH with an IC 50 = 43 μ m (Fig. 5A) and represents the first selective inhibitor of Mt DHODH, since it showed no inhibitory activity on the human orthologue (produced as already described in reference [35]) (Fig. S1).…”

“…In order to identify a selective MtDHODH inhibitor to be considered as potential antimycobacterial agent, we screened our in-house chemical library consisting in more than 1200 compounds based on the hydroxyazoles scaffold and other heterocycles, with the characteristic of being carboxylic acid bioisosteres and able of establishing strong interactions with the positive ionized residues of proteins as arginine. Among them, we also included molecules, derived from the research pipelines aimed at identifying human [32][33][34][35] and Plasmodium falciparum DHODH inhibitors [36], that did not show activity toward their targets. The selection of potential MtDHODH inhibitors from the in-house library has been performed following two basic principles: (i) identification of molecules having a chemical scaffold similar to others that have been reported with antimycobacterial activity; and (ii) presence of the carboxylic acid terminal or bioisosteres, potentially able of establishing strong interactions with the arginine located in the MQ binding pocket that is highly conserved and interacts with most of the well-known DHODH inhibitors.…”

Hydrogel-Based Pre-Clinical Evaluation of Repurposed FDA-Approved Drugs for AML

“…Vidofludimus is a DHODH inhibitor with potential anti-inflammatory, immunomodulating, and anti-viral activities, recently shown to promote cell cycle arrest in lymphoblastoid and lymphoma cell lines [ 34 ]. Although the MLL-AF9 harboring THP-1 and mAF9 cells showed limited sensitivity to Vidofludimus, recent reports suggest that second-generation DHODH inhibitors may have a particular role to play in MLL-AF9 AML and are now available at low concentrations (74 nM) with low toxicity [ 35 ].…”

Expected and unexpected products from reacting Sanger’s reagent with p-phenylenediamine

“…18,19 DNFB 1 was reacted with aniline 14 to compare with the products formed from p-phenylenediamine 6 (Figure 8). The expected and known substitution product 15 was formed 20 in which the fluorine atom has been displaced. No other products were formed in significant amounts.…”