Zinc Supplementation Enhances the Hematopoietic Activity of Erythropoiesis-Stimulating Agents but Not Hypoxia-Inducible Factor-Prolyl Hydroxylase Inhibitors.

Since zinc is involved in many aspects of the hematopoietic process, zinc supplementation can reduce erythropoiesis-stimulating agents (ESAs) in patients undergoing hemodialysis. However, it remains unclear whether hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) have similar reduction effects. HIF-PHI stabilizes HIF, which promotes hematopoiesis, although HIF-1α levels are downregulated by zinc. This study aimed to investigate the effect of zinc supplementation on the hematopoietic effect of HIF-PHI in patients undergoing hemodialysis. Thirty patients undergoing maintenance hemodialysis who underwent periods of treatment with roxadustat or darbepoetin alfa during the past 3 years were retrospectively observed. Participants who underwent periods with and without zinc supplementation were selected, with nine treated with darbepoetin alfa and nine treated with roxadustat. Similarly to the ESA responsiveness index (ERI), the hematopoietic effect of zinc supplementation was determined by the HIF-PHI responsiveness index (HRI), which was calculated by dividing the HIF-PHI dose (mg/week) by the patient's dry weight (kg) and hemoglobin level (g/L). Zinc supplementation significantly increased ERI (p < 0.05), but no significant change was observed (p = 0.931) in HRI. Although zinc supplementation did not significantly affect HRI, adequate zinc supplementation is required to alleviate concerns such as vascular calcification and increased serum copper during the use of HIF-PHI.

HIF-PHD inhibitor desidustat ameliorates iron deficiency anemia.

Iron deficiency anemia is caused by many pathological conditions like chronic kidney disease (CKD), inflammation, malnutrition and gastrointestinal abnormality. Current treatments that are erythropoiesis stimulating agents (ESAs) and iron supplementation are inadequate and often lead to tolerance and/or toxicity. Desidustat, a prolyl hydroxylase (PHD) inhibitor, is clinically used for the treatment of anemia with CKD. In this study, we investigated the effect of desidustat on iron deficiency anemia (IDA). IDA was induced in C57BL6/J mice by iron deficient diet feeding. These mice were then treated with desidustat (15 mg/kg, PO) and FeSO4 (20 mg/kg) for five weeks and effect of the treatment on hematology, iron homeostasis, and bone marrow histology was observed. Effect of desidustat on iron metabolism in inflammation (LPS)-induced iron deficiency was also assessed. Both, Desidustat and FeSO4, increased MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), hemoglobin, and HCT (hematocrit) in blood and increased iron in serum, liver, and spleen. Desidustat increased MCHC (mean corpuscular hemoglobin concentration) while FeSO4 treatment did not alter it. FeSO4 treatment significantly increased iron deposition in liver, and spleen, while desidustat increased iron in circulation and demonstrated efficient iron utilization. Desidustat increased iron absorption, serum iron and decreased hepcidin without altering tissue iron, while FeSO4 increased serum and tissue iron by increasing hepcidin in LPS-induced iron deficiency. Desidustat increased erythroid population, especially iron-dependent polychromatic normoblasts and orthochromatic normoblasts, while FeSO4 did not improve cell architecture. PHD inhibition by desidustat improved iron utilization in iron deficiency anemia, by efficient erythropoiesis.

Nonclinical Pharmacokinetic Evaluation of Desidustat: a Novel Prolyl Hydroxylase Inhibitor for the Treatment of Anemia.

BACKGROUND AND OBJECTIVES: Desidustat is a novel prolyl hydroxylase domain (PHD) inhibitor for the treatment of anemia. The objective of this study was to investigate the pharmacokinetics and drug-drug interaction properties of desidustat using in vitro and in vivo nonclinical models. METHODS: In vitro, Caco2 cell permeability, plasma protein binding, metabolism, cytochrome P450 (CYP) inhibition, and CYP induction were examined. In vivo, pharmacokinetic studies of oral bioavailability in mice, rats, dogs and monkeys, dose linearity, tissue distribution, and excretion in rats were conducted. RESULTS: In Caco-2 cells, the apparent permeability of desidustat was high at low pH and low at neutral pH. The oral bioavailability (%F) of desidustat was 43-100% with a median time to reach peak concentration (Tmax) of about 0.25-1.3 h across species. Desidustat displayed a low mean plasma clearance (CL) of 1.3-4.1 mL/min/kg (approximately 1.8-7.4% of hepatic blood flow), and the mean steady-state volume of distribution (Vss) was 0.2-0.4 L/kg (approximately 30-61% of the total body water). Desidustat showed a dose-dependent increase in exposures over the 15-100 mg/kg dose range. It was rapidly distributed in various tissues, with the highest tissue-to-blood ratio in the liver (1.8) and kidney (1.7). Desidustat showed high plasma protein binding and was metabolically stable in human liver microsomes, hepatocytes, and recombinant CYPs. It did not show significant inhibition of major drug-metabolizing CYP enzymes (IC50 > 300 µM) or the potential to induce CYP1A2 and CYP3A4/5 (up to 100 µM) in HepG2 cells. It may have minimal potential of clinical drug-drug interaction when used in combination with iron supplements or phosphate binders. Desidustat was primarily excreted unchanged in urine (25% of the oral dose) and bile (25% of the oral dose) in rats. The mean elimination half-life of desidustat ranged from 1.0 to 5.3 h and 1.3 to 5.7 h across species after intravenous and oral administration, respectively. CONCLUSION: Taken together, desidustat is well absorbed orally. It showed a dose-dependent increase in exposure, did not accumulate in tissue, and was eliminated via dual routes. It is metabolically stable, has minimal potential to cause clinical drug-drug interactions (DDIs), and demonstrates discriminable pharmacokinetic properties for the treatment of anemia.

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.

Discovery of prolyl hydroxylase 2 inhibitors with new chemical scaffolds as in vivo active erythropoietin inducers through a combined virtual screening strategy.

Hypoxia-inducible factor (HIF) is identified to be a promising target to mediate the response to hypoxia. Its stability and activation are negatively controlled by prolyl hydroxylase 2 (PHD2). Thus, PHD2 inhibition has been perceived as a promising anti-anemia therapy. In this study, we carried out a structure-based virtual screening followed by in vitro and in vivo biological validation, with the goal to identify novel PHD2 inhibitors. As a result, a set of hits with new chemical scaffolds were revealed to be active in vitro for PHD2 inhibition. Compounds 2 and 3 were revealed to be capable of stabilizing HIF-α and stimulating erythropoietin (EPO) expression in cell-based assays. Notably, further in vivo assays revealed that 2 was capable of elevating the EPO plasma levels in C57BL/6 mice model. These findings provide new chemical scaffolds for further development of PHD2 inhibitors.

HIF stabilizers in the management of renal anemia: from bench to bedside to pediatrics.

Anemia is a common complication of chronic kidney disease (CKD) in adult and pediatric patients. It has traditionally been treated with erythropoietin therapy and iron supplementation, with great success. With the discovery of the major transcription factor hypoxia inducible factor (HIF) for the erythropoietin gene in 1992, molecules were created that inhibit the HIF prolyl-hydroxylase enzyme. This new class of drug-called HIF stabilizers, or HIF prolyl-hydroxylase inhibitors-prevents the proteasomal degradation of HIF-α, thereby inducing upregulation of the erythropoietin gene. This new strategy for treating CKD anemia is already in phase III clinical trials in adults, and the potential advantages of this therapy are that it is orally active (thereby avoiding injections), and patients are exposed to lower circulating levels of erythropoietin. The long-term safety of this strategy, however, requires elucidation in these trials, particularly since there are many other hypoxia-sensitive genes, notably, angiogenic factors such as vascular endothelial growth factors (VEGF), as well as glycolytic enzymes. As with all new therapies, it is only once a positive benefit: risk profile has been ascertained in adults that the treatment will translate across into pediatrics. Specific issues in the pediatric CKD population are discussed in this review.

"Branched Tail" Oxyquinoline Inhibitors of HIF Prolyl Hydroxylase: Early Evaluation of Toxicity and Metabolism Using Liver-on-a-chip.

BACKGROUND: "Branched tail" oxyquinolines, and adaptaquin in particular, are potent HIF prolyl hydroxylase inhibitors showing promising results in in vivo hemorrhagic stroke models. The further improvement of the potency resulted in identification of a number of adaptaquin analogs. Early evaluation of toxicity and metabolism is desired right at the step of lead selection. OBJECTIVE: The aim of the study is to characterize the toxicity and metabolism of adaptaquin and its new improved analogs. METHOD: Liver-on-a-chip technology with differentiated HepaRG cells followed by LC-MS detection of the studied compounds and metabolites of the P450 substrate-inhibitor panel for CYP2B6, CYP2C9, CYP2C19, and CYP3A4. RESULTS: The optimized adaptaquin analogs show no toxicity up to a 100-fold increased range over EC50. The drugs are metabolized by CYP3A4 and CYP2B6 as shown with the use of the cytochrome P450 substrate-inhibitor panel designed and optimized for preclinical evaluation of drugs' in vitro biotransformation on a 3D human histotypical cell model using "liver-on-a-chip" technology. Activation of CYP2B6 with the drugs tested has been observed. A scheme for adaptaquin oxidative conversion is proposed. CONCLUSION: The optimized adaptaquin analogs are suitable for further preclinical trials. Activation of CYP2B6 with adaptaquin and its variants points to a potential increase in Tylenol toxicity if administered together.

Iron therapy for managing anaemia in chronic kidney disease.

PURPOSE OF REVIEW: Iron deficiency is a major contributory cause to the development of anaemia in chronic kidney disease (CKD), and thus, iron replacement therapy plays a critical role in the management of this condition. The two main routes for administering iron are oral and intravenous, and there have been a number of new publications relevant to both routes of administration. RECENT FINDINGS: Recent developments on the topic of iron management in CKD include the introduction of new oral iron preparations, as well as two recent meta-analyses on iron therapy in CKD (one on oral versus intravenous iron, and one on high- versus low-dose intravenous iron in haemodialysis patients). There is also increasing interest in other strategies to improve iron availability, such as intradialytic iron, hypoxia-inducible factor stabilization and antihepcidin strategies. SUMMARY: Even despite the latest publications in this field, we are still left with serious gaps in our evidence base on how best to provide supplemental iron to CKD patients. Most of the evidence suggests that intravenous iron is superior to oral iron in increasing haemoglobin and minimizing the use of erythropoiesis-stimulating agents, but the safety of intravenous iron remains a controversy. The PIVOTAL study will hopefully provide informative data to fill some of the gap in the evidence-base and inform best clinical practice.

Application of in-vitro screening methods on hypoxia inducible factor prolyl hydroxylase inhibitors.

Anemia resulting from the reduced expression of erythropoietin (EPO) is a common complication of patients with chronic kidney diseases (CKD). Hypoxia inducible transcription factor-α (HIF-α), which adapts cellular hypoxia condition, regulates the expression of many downstream genes including the EPO gene. Hypoxia inducible transcription factor prolyl hydroxylase 2 (HIF-PHD2), as the key regulator of hypoxia response, is function of hydroxylating specify proline residues of HIF-α, which may lead to the degradation of HIF-α and eventually cause disenabling the expression of erythropoietin. Therefore, it is valid to improve anemia by inhibiting HIF-PHD2. In-vitro screening plays a vital role in searching for novel small molecule HIF-PHD2 inhibitors, thus, this review classified in-vitro screening methods which are used to hit novel HIF-PHD2 inhibitors.

Recent Advances in Developing Inhibitors for Hypoxia-Inducible Factor Prolyl Hydroxylases and Their Therapeutic Implications.

Hypoxia-inducible factor (HIF) prolyl hydroxylases (PHDs) are members of the 2-oxoglutarate dependent non-heme iron dioxygenases. Due to their physiological roles in regulation of HIF-1α stability, many efforts have been focused on searching for selective PHD inhibitors to control HIF-1α levels for therapeutic applications. In this review, we first describe the structure of PHD2 as a molecular basis for structure-based drug design (SBDD) and various experimental methods developed for measuring PHD activity. We further discuss the current status of the development of PHD inhibitors enabled by combining SBDD approaches with high-throughput screening. Finally, we highlight the clinical implications of small molecule PHD inhibitors.

Bone substitute materials supplemented with prolyl hydroxylase inhibitors decrease osteoclastogenesis in vitro.

BACKGROUND AND OBJECTIVE: Inhibition of prolyl hydroxylases stimulates bone regeneration. Consequently, bone substitute materials were developed that release prolyl hydroxylase inhibitors. However, the impact of prolyl hydroxylase inhibitors released from these carriers on osteoclastogenesis is not clear. We therefore assessed the effect of bone substitute materials that release prolyl hydroxylase inhibitors on osteoclastogenesis. MATERIAL AND METHODS: Dimethyloxalylglycine, desferrioxamine, and l-mimosine were lyophilized onto bovine bone mineral and hydroxyapatite, and supernatants were generated. Osteoclastogenesis was induced in murine bone marrow cultures in the presence of the supernatants from bone substitute materials. The formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and TRAP activity were determined. To test for possible effects on osteoclast progenitor cells, we measured the effect of the supernatants on proliferation and viability. In addition, experiments were performed where prolyl hydroxylase inhibitors were directly added to the bone marrow cultures. RESULTS: We found that prolyl hydroxylase inhibitors released within the first hours from bone substitute materials reduce the number and activity of TRAP-positive multinucleated cells. In line with this, addition of prolyl hydroxylase inhibitors directly to the bone marrow cultures dose-dependently reduced the number of TRAP-positive multinucleated cells and the overall resorption activity. Moreover, the released prolyl hydroxylase inhibitors decreased proliferation but not viability of osteoclast progenitor cells. CONCLUSION: Our results show that prolyl hydroxylase inhibitors released from bone substitute materials decrease osteoclastogenesis in murine bone marrow cultures.