Iron Therapy in Chronic Kidney Disease: Days of Future Past.

Anemia affects millions of patients with chronic kidney disease (CKD) and prompt iron supplementation can lead to reductions in the required dose of erythropoiesis-stimulating agents, thereby reducing medical costs. Oral and intravenous (IV) traditional iron preparations are considered far from ideal, primarily due to gastrointestinal intolerability and the potential risk of infusion reactions, respectively. Fortunately, the emergence of novel iron replacement therapies has engendered a paradigm shift in the treatment of iron deficiency anemia in patients with CKD. For example, oral ferric citrate is an efficacious and safe phosphate binder that increases iron stores to maintain hemoglobin levels. Additional benefits include reductions in fibroblast growth factor 23 levels and the activation of 1,25 dihydroxyvitamin D. The new-generation IV iron preparations ferumoxytol, iron isomaltoside 1000, and ferric carboxymaltose are characterized by a reduced risk of infusion reactions and are clinically well tolerated as a rapid high-dose infusion. In patients undergoing hemodialysis (HD), ferric pyrophosphate citrate (FPC) administered through dialysate enables the replacement of ongoing uremic and HD-related iron loss. FPC transports iron directly to transferrin, bypassing the reticuloendothelial system and avoiding iron sequestration. Moreover, this paper summarizes recent advancements of hypoxia-inducible factor prolyl hydroxylase inhibitors and future perspectives in renal anemia management.

Effects of orally active hypoxia inducible factor alpha prolyl hydroxylase inhibitor, FG4592 on renal fibrogenic potential in mouse unilateral ureteral obstruction model.

Orally active hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors that stabilize HIF protein and stimulate the production of erythropoietin have been approved to treat renal anemia. Our previous report suggested that HIF-1α dependent fibrogenic mechanisms are operating at the early onset of renal fibrosis and its contribution declines with the progression in mouse unilateral ureteral obstruction (UUO) model. The aim of the study is to evaluate the renal fibrogenic potential of FG4592, a recently approved orally active HIF prolyl hydroxylase inhibitor in mouse UUO model. Male C57BL/6J mice orally given FG-4592 (12.5 mg/kg/day and 50 mg/kg/day) were subjected to UUO. Neither dose of FG-4592 affected renal fibrosis or macrophage infiltration. FG-4592 had no effects on increased mRNA of collagen I, collagen III or transforming growth factor-ß1. At 3 days after UUO, higher dose of FG-4592 potentiated the increased mRNA expression of profibrogenic molecules, plasminogen activator inhibitor 1 (Pai-1) and connective tissue growth factor (Ctgf) but such potentiation disappeared at 7 days after UUO. It is suggested that FG-4592 used in the present study had little effects on renal fibrosis even though high dose of FG-4592 used in the present study transiently potentiated gene expression of Pai-1 and Ctgf in the UUO kidney.

Iron Regulation by Molidustat, a Daily Oral Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor, in Patients with Chronic Kidney Disease.

BACKGROUND/AIMS: The current treatment for anemia associated with chronic kidney disease (CKD) includes the administration of erythropoiesis stimulating agents (ESAs) combined with iron supplementation. Molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, has potential to treat anemia associated with CKD through increased erythropoietin production and improved iron availability. Here, we report the effect of molidustat on iron metabolism. METHOD: Parameters of iron metabolism were monitored in three 16-week, randomized, controlled, phase 2 studies assessing the safety and efficacy of molidustat in the treatment of anemia associated with CKD in different populations: treatment-naïve and previously ESA-treated patients not on dialysis, and previously ESA-treated patients on hemodialysis. Iron supplementation was left at the discretion of the investigator. RESULTS: In treatment-naïve patients not on dialysis, transferrin saturation (TSAT), hepcidin, ferritin, and iron concentrations decreased with molidustat, whereas total iron binding capacity (TIBC) increased. Similar results were observed in previously ESA-treated patients not on dialysis, although changes in those parameters were larger in treatment-naïve than in previously ESA-treated patients. In previously ESA-treated patients receiving hemodialysis, hepcidin concentration and TIBC remained stable with molidustat, whereas TSAT and ferritin and iron concentrations increased. Generally, similar trends were observed in secondary analyses of subgroups of patients not receiving iron supplementation. CONCLUSIONS: Molidustat is a potential alternative to standard treatment of anemia associated with CKD, with a different mechanism of action. In patients not receiving dialysis, molidustat increases iron availability. In patients receiving hemodialysis, further investigation is required to understand fully the mechanisms underlying iron mobilization associated with molidustat.

First-in-man-proof of concept study with molidustat: a novel selective oral HIF-prolyl hydroxylase inhibitor for the treatment of renal anaemia.

AIMS: Insufficient erythropoietin (EPO) synthesis is a relevant cause of renal anaemia in patients with chronic kidney disease. Molidustat, a selective hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, increases endogenous EPO levels dose dependently in preclinical models. We examined the pharmacokinetics, safety, tolerability and effect on EPO levels of single oral doses of molidustat in healthy male volunteers. METHODS: This was a single-centre, randomized, single-blind, placebo-controlled, group-comparison, dose-escalation study. Molidustat was administered at doses of 5, 12.5, 25, 37.5 or 50 mg as a polyethylene glycol-based solution. RESULTS: In total, 45 volunteers received molidustat and 14 received placebo. Molidustat was absorbed rapidly, and the mean maximum plasma concentration and area under the concentration-time curve increased dose dependently. The mean terminal half-life was 4.64-10.40 h. A significant increase in endogenous EPO was observed following single oral doses of molidustat of 12.5 mg and above. Geometric mean peak EPO levels were 14.8 IU l-1 (90% confidence interval 13.0, 16.9) for volunteers who received placebo and 39.8 IU l-1 (90% confidence interval: 29.4, 53.8) for those who received molidustat 50 mg. The time course of EPO levels resembled the normal diurnal variation in EPO. Maximum EPO levels were observed approximately 12 h postdose and returned to baseline after approximately 24-48 h. All doses of molidustat were well tolerated and there were no significant changes in vital signs or laboratory safety parameters. CONCLUSIONS: Oral administration of molidustat to healthy volunteers elicited a dose-dependent increase in endogenous EPO. These results support the ongoing development of molidustat as a potential new treatment for patients with renal anaemia.

Pharmacologic stabilization of hypoxia-inducible transcription factors protects developing mouse brain from hypoxia-induced apoptotic cell death.

OBJECTIVE: Accumulation of hypoxia-inducible transcription factors (HIFs) by prolyl-4-hydroxylase inhibitors (PHI) has been suggested to induce neuroprotection in the ischemic rodent brain. We aimed to investigate in vivo effects of a novel PHI on HIF-regulated neurotrophic and pro-apoptotic factors in the developing normoxic and hypoxic mouse brain. METHODS: Neonatal mice (P7) were treated with PHI FG-4497 (30-100mg/kg, i.p.) followed by exposure to systemic hypoxia (8% O2, 6h) 4h later. Cerebral expression of HIFα-subunits, specific neurotrophic and vasoactive target genes (vascular endothelial growth factor (VEGF), adrenomedullin (ADM), erythropoietin (EPO), inducible nitric oxide synthase (iNOS)) as well as pro-apoptotic (BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 gene (BNIP3), immediate early response 3 (IER3)) and migratory factors (chemokine receptor 4 (CXCR4), stromal cell-derived factor 1 (SDF-1)) was determined (quantitative real-time (RT)., Western blot analysis) in comparison to controls. Apoptotic cell death was analyzed by terminal desoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and cleaved caspase 3 (CC3) staining. RESULTS: Under normoxic conditions, FG-4497 treatment significantly induced the accumulation of both HIF-1α and HIF-2α isoforms in developing mouse brain. In addition, there was a significant up-regulation of HIF target genes (VEGF, ADM, EPO, CXCR4, p<0.01) with FG-4497 treatment compared to controls supporting functional activation of the HIF proteins. Under hypoxia, differential target gene activation was observed in the developing brain including additive effects of FG-4497 and hypoxia on mRNA expression of VEGF and ADM as well as a dose-dependent down-regulation of iNOS. BNIP3 but not IER3 mRNA levels significantly increased in hypoxic brains pre-treated with high-dose FG-4497 compared to controls. Of special interest, FG-4497 treatment significantly diminished apoptotic cell death, quantified by TUNEL and CC3-positive cells, in hypoxic developing brains compared to controls. CONCLUSIONS: PHI treatment modulates neurotrophic factors known to be crucially involved in hypoxia-induced cerebral adaptive mechanisms as well as early brain maturation. Pre-treatment with FG-4497 seems to protect the developing brain from hypoxia-induced apoptosis. Present observations provide basic information for further evaluation of neuroprotective properties of PHI treatment in hypoxic injury of the developing brain. However, potential effects on maturational processes need special attention in experimental research targeting HIF-dependent neuroprotective interventions during the very early stage of brain development.