Design and synthesis of substituted pyridine derivatives as HIF-1α prolyl hydroxylase inhibitors

Benzimidazole-2-pyrazole HIF Prolyl 4-Hydroxylase Inhibitors as Oral Erythropoietin Secretagogues

“…8,9 Because of their key role in the regulation of HIF levels, inhibition of PHD enzymes is an attractive strategy by which to potentiate the transcriptional activity of HIF in a therapeutically relevant manner. Indeed, during the last several years, intense efforts to discover PHD inhibitors have been adumbrated primarily in the patent literature, 10 and to a much lesser degree in the peer-reviewed literature, [11][12][13][14][15][16][17][18][19] leading to four compounds entering clinical trials. 20,21 In this letter, we report our efforts in this area, which led to the discovery of novel PHD inhibitors that are potent, orally active erythropoietin secretagogues.…”

Novel Approach to High Throughput Screening for Activators of Transcription Factors

“…The best inhibition constant among substituted pyridine derivatives was exhibited by p-chloro phenyl-substituted 5-pyridine carboxyamide (15 µM) and those with the pyrazole moiety in the 5 th position of the pyridine ring (5-20 µM) (Warshakoon et al, 2006a); the further work resulted in the significantly improved affinity (1-2 µM) of the newly designed inhibitors of pyrazolopyrimidines series (Warshakoon et al, 2006a). Imidazo[1,2-a]pyridine derivatives showed the apparent inhibition constants in the 4-27 M range (Warshakoon et al, 2006b), and 8-hydroxyquinoline derivates exhibited the apparent inhibition constants in the range of 3-10 µM (Warshakoon et al, 2006c). However, taking into account that the screening for potential inhibitors was performed using a 19-mer peptide, which shows at least 1 order of magnitude worse K m than HIF-ODD, the range of the apparent inhibitor constants obtained may be insufficient for the inhibition of the enzyme activity in vivo.…”

“…Two primary modes of screening for HIF activators have been well described: a recombinant enzyme-based screen for PHD2 inhibitors (used by Fibrogen (Ivan et al 2002), Amgen , Allen et al 2008), Procter and Gamble Pharmaceuticals Inc. (Warshakoon et al 2006a, Warshakoon et al 2006b, Warshakoon et al 2006c, Warshakoon et al 2006d, and other teams (Nangaku et al 2007)); and a cell-based screen using HREluciferase reporter construct used by a number of labs including our own. The cell-based assay with HRE-luc reporter system, a promoter-reporter construct that contained 68 bp of a known hypoxia and HIF-1 regulated gene, enolase, containing a wild type HRE (5'-RCTGT-3'), is a widely used approach for screening of HIF activators with diverse mechanisms of action (Semenza et al 1996).…”

“…The recently reported crystal structure of PHD2 with a 17-mer HIF peptide (Chowdhury et al 2009) shows no active site water displacement, which appears to be a mandatory requirement for the initiation of the catalytic cycle. Given these biases, it is not surprising that all PHD inhibitors developed using the recombinant enzyme explored only the KG-binding motif inside PHD2 active site and had a carboxyl group interacting with Arg-383 in addition to a clearly defined iron-binding motif , Warshakoon et al 2006a, Warshakoon et al 2006b, Warshakoon et al 2006c, Warshakoon et al 2006d, Ivan et al 2002. The reaction mixture has to be supplemented with excess of iron, alpha-ketoglutarate, and HIF peptide, making the selection of mild inhibitors impossible.…”

Effects of Clioquinol Analogues on the Hypoxia-Inducible Factor Pathway and Intracelullar Mobilization of Metal Ions

“…Considering that 8-hydroxyquinoline derivatives are well-known Fe 2+ chelators in solution, and Fe 2+ is an important cofactor of HIF hydroxylases, 40) 8-hydroxyquinoline derivatives would be expected to exert their physiological effects by inhibiting the hydroxylation activity via bidentate chelation of the Fe 2+ ion. 41) In fact, we observed the blockage of the ubiquitination of HIF-1α after treatment with CQ analogues, suggesting the inhibition of its hydroxylation (data not shown).…”