Inhibition of hypoxia inducible factor prolyl hydroxylase (PHD) represents a promising strategy for the discovery of a next generation treatment for renal anemia. We identified several 5,6-fused ring systems as novel scaffolds of the PHD inhibitor on the basis of pharmacophore analysis. In particular, triazolopyridine derivatives showed potent PHD2 inhibitory activities. Examination of the predominance of the triazolopyridines in potency by electrostatic calculations suggested favorable π-π stacking interactions with Tyr310. Lead optimization to improve the efficacy of erythropoietin release in cells and by improving cell permeability led to the discovery of JTZ-951 (compound), with a 5-phenethyl substituent on the triazolopyridine group, which increased hemoglobin levels with daily oral dosing in rats. Compound was rapidly absorbed after oral administration and disappeared shortly thereafter, which could be advantageous in terms of safety. Compound was selected as a clinical candidate.

Infiltrating polymorphonuclear leukocytes (PMN) in the peritoneal cavity were found to express L-histidine decarboxylase (HDC), the rate-limiting enzyme of histamine synthesis, in a csein-induced peritonitis model. Expression of HDC was detected in the elicited PMN, but not in the peripheral blood leukocytes. The peritoneal lavage fluids in this model were found to augment histamine synthesis in PMN isolated from the bone marrow. Rapid posttranslational processing of HDC was observed in PMN, and the dominant form of HDC was the mature 53-kDa form, which was found to co-localize with a granule enzyme, matrix metalloproteinase-9 (MMP-9). Treatment of PMN with the phorbol ester PMA, which stimulates the release of MMP-9, did not liberate the granular HDC. Immunofluorescence studies using an anti-HDC antibody strongly suggested that HDC is bound to the cytosolic side of the granule membranes. These observations suggest that HDC is induced upon infiltration of PMN into the mouse peritoneal cavity and that histamine is synthesized by HDC attached to the granule membranes of PMN.

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G-CSF is a hemopoietic growth factor involved in granulocytic differentiation of progenitor cells. In this study, we investigated the effects of PGE2 on G-CSF production in murine peritoneal neutrophils in vitro and in vivo. PGE2 augmented LPS-primed G-CSF release from peritoneal neutrophils. This augmentation was mimicked by a type E prostanoid receptor (EP)2-selective agonist but not by other EP-specific agonists. Indeed, the effect of PGE2 on G-CSF release was abolished in neutrophils isolated from EP2-deficient mice. PGE2 and an EP2 agonist have the ability to stimulate G-CSF gene expression even in the absence of LPS. In the casein-induced peritonitis model, the appearance of G-CSF in the casein-injected peritoneal cavity associated well with the timing of neutrophil infiltration as well as PGE2 levels in exudates, with a peak value at 6 h postinjection. Inhibition of endogenous PG synthesis by indomethacin resulted in a marked decrease in G-CSF content and neutrophil number in the peritoneal cavity. Moreover, EP2-deficient mice exhibited a strikingly reduced G-CSF content in peritoneal exudates with comparable responses in neutrophil migration and local PGE2 production at 6 h postinjection. These results suggest that the PGE2-EP2 system contributes to the local production of G-CSF during acute inflammation.