Effects of vadadustat on hemoglobin concentrations in patients receiving hemodialysis previously treated with erythropoiesis-stimulating agents

Quantitative systems pharmacology model of erythropoiesis to simulate therapies targeting anemia due to chronic kidney disease

Anemia induced by chronic kidney disease (CKD) has multiple underlying mechanistic causes and generally worsens as CKD progresses. Erythropoietin (EPO) is a key endogenous protein which increases the number of erythrocyte progenitors that mature into red blood cells that carry hemoglobin (Hb). Recombinant human erythropoietin (rHuEPO) in its native and re-engineered forms is used as a therapeutic to alleviate CKD-induced anemia by stimulating erythropoiesis. However, due to safety risks associated with erythropoiesis-stimulating agents (ESAs), a new class of drugs, prolyl hydroxylase inhibitors (PHIs), has been developed. Instead of administering exogenous EPO, PHIs facilitate the accumulation of HIF-α, which results in the increased production of endogenous EPO. Clinical trials for ESAs and PHIs generally involve balancing decisions related to safety and efficacy by carefully evaluating the criteria for patient selection and adaptive trial design. To enable such decisions, we developed a quantitative systems pharmacology (QSP) model of erythropoiesis which captures key aspects of physiology and its disruption in CKD. Furthermore, CKD virtual populations of varying severities were developed, calibrated, and validated against public data. Such a model can be used to simulate alternative trial protocols while designing phase 3 clinical trials, as well as an asset for reverse translation in understanding emerging clinical data.

An Overview of Safety and Efficacy Between Hypoxia-Inducible Factor-Prolyl-Hydroxylase Inhibitors and Erythropoietin-Stimulating Agents in Treating Anemia in Chronic Kidney Disease Patients

Anemia is one of the common complications in chronic kidney disease (CKD) patients. Erythropoietin and iron deficiencies are the major causes to develop anemia in CKD patients. Untreated anemia is associated with increased morbidity and mortality. Erythropoietin-stimulating agents (ESA) with iron supplementation are the standard for treating renal anemia. Although ESA with iron supplementation is an effective therapy in maintaining serum hemoglobin (Hb) levels, it increases the risk of several life-threatening adverse events such as hypertension, thromboembolism, cardiovascular morbidity, and mortality with long-term use. Therefore, effective alternate therapy with better safety and efficacy is needed to treat renal anemia. The newer oral therapy hypoxia-inducible factor-prolyl-hydroxylase inhibitors (HIF-PHI) can potentially be an effective alternative therapy in treating renal anemia. This review article compares the safety and efficacy between HIF-PHI and ESA in treating anemia in CKD patients. We conducted a comprehensive literature review of articles, including clinical trials, meta-analyses, and reviews, that compared the safety and efficacy between HIF-PHI and ESA. Studies have shown that the newer oral therapy, HIF-PHI, was non-inferior to ESA to maintain serum Hb levels in CKD patients. Moreover, the adverse event profile was almost similar in both groups. However, as the studies we reviewed have small sample sizes and short duration periods, the long-term effectiveness and safety of HIF-PHI over ESA in treating renal anemia cannot be established.

Overall Adverse Event Profile of Vadadustat versus Darbepoetin Alfa for the Treatment of Anemia Associated with Chronic Kidney Disease in Phase 3 Trials

INTRODUCTION

Anemia frequently occurs in chronic kidney disease (CKD), is associated with poor quality of life and cardiovascular outcomes, and its treatment represents a considerable economic burden to the healthcare system. Although effective, the current standard of care for the treatment of anemia in chronic kidney disease patients with erythropoiesis-stimulating agents requires chronic/ongoing injections, making the treatment less accessible or desirable to patients not treated by in-center maintenance hemodialysis. Furthermore, safety concerns, including an increased risk of cardiovascular events and mortality, have emerged from their use in studies targeting hemoglobin concentrations in the normal or near-normal range. The orally active hypoxia-inducible factor prolyl hydroxylase inhibitor vadadustat may offer advantages over erythropoiesis-stimulating agents by correcting anemia via pathways activating endogenous erythropoietin production.

METHODS

To comprehensively analyze the safety profile of vadadustat in patients with dialysis-dependent and non-dialysis-dependent CKD-related anemia, we pooled the safety populations from each of the four trials in the phase 3 clinical program (n = 7,373) and compared the risk of treatment-emergent adverse events (TEAEs) for each treatment arm.

RESULTS

In patients randomized to vadadustat versus darbepoetin alfa, rates of TEAEs (88.9% vs. 89.3%), treatment-emergent serious adverse events (58.0% vs. 59.3%), and TEAEs leading to death (16.1% vs. 16.2%) were similar, as were rates of adverse events of special interest, including cardiovascular-, hepatic-, and neoplasm-related adverse events.

DISCUSSION/CONCLUSION

Among patients with CKD-related anemia treated with vadadustat, we observed similar rates of adverse events relative to those treated with darbepoetin alfa.

Preclinical Characterization of Vadadustat (AKB-6548), an Oral Small Molecule Hypoxia-Inducible Factor Prolyl-4-Hydroxylase Inhibitor, for the Potential Treatment of Renal Anemia

Pharmacological inhibition of prolyl-4-hydroxylase domain (PHD) enzymes stabilizes hypoxia-inducible factors (HIFs), transcription factors that activate target genes that, among others, increase erythropoietin (EPO) synthesis, resulting in the production of new red blood cells (RBCs). Herein, we summarize the preclinical characteristics of the small molecule HIF prolyl-4-hydroxylase inhibitor vadadustat (AKB-6548), which is in development for the treatment of anemia in patients with chronic kidney disease (CKD). Vadadustat inhibits the enzyme activity of all three human PHD isozymes, PHD1, PHD2, and PHD3, with similar low nanomolar inhibitory constant values. PHD enzyme inhibition by vadadustat is competitive with endogenous cofactor 2-oxoglutarate and is insensitive to free iron concentration. In the human hepatocellular carcinoma cell line (Hep 3B) and human umbilical vein endothelial cells, PHD inhibition by vadadustat leads to the time- and concentration-dependent stabilization of HIF-1α and HIF-2α In Hep 3B cells, this in turn results in the synthesis and secretion of EPO; vascular endothelial growth factor is not measured at detectable levels. A single oral dose of vadadustat in rats potently increases circulating levels of EPO, and daily oral dosing for 14 days increases RBC indices in healthy rats and in the 5/6 nephrectomy model of CKD. In mice and dogs, once-daily repeat oral dosing increases hemoglobin and hematocrit. Vadadustat has a relatively short half-life in all nonclinical species evaluated and does not accumulate when administered as a single bolus dose (oral or intravenous) or upon repeat oral dosing. The pharmacological profile of vadadustat supports continued development for treatment of renal anemia. SIGNIFICANCE STATEMENT: Vadadustat (AKB-6548) is an orally bioavailable small molecule prolyl-4-hydroxylase inhibitor in development for anemia of chronic kidney disease. It is an equipotent inhibitor of the three human prolyl-4-hydroxylase domain isoforms, which activates erythropoiesis through stabilization of hypoxia-inducible factor (HIF)-1α and HIF-2α, increasing production of erythropoietin, without detectable stimulation of vascular endothelial growth factor.

Generic approach for the discovery of drug metabolites in horses based on data-dependent acquisition by liquid chromatography high-resolution mass spectrometry and its applications to pharmacokinetic study of daprodustat

In drug metabolism studies in horses, non-targeted analysis by means of liquid chromatography coupled with high-resolution mass spectrometry with data-dependent acquisition (DDA) has recently become increasingly popular for rapid identification of potential biomarkers in post-administration biological samples. However, the most commonly encountered problem is the presence of highly abundant interfering components that co-elute with the target substances, especially if the concentrations of these substances are relatively low. In this study, we evaluated the possibility of expanding DDA coverage for the identification of drug metabolites by applying intelligently generated exclusion lists (ELs) consisting of a set of chemical backgrounds and endogenous substances. Daprodustat was used as a model compound because of its relatively lower administration dose (100 mg) compared to other hypoxia-inducible factor stabilizers and the high demand in the detection sensitivity of its metabolites at the anticipated lower concentrations. It was found that the entire DDA process could efficiently identify both major and minor metabolites (flagged beyond the pre-set DDA threshold) in a single run after applying the ELs to exclude 67.7-99.0% of the interfering peaks, resulting in a much higher chance of triggering DDA to cover the analytes of interest. This approach successfully identified 21 metabolites of daprodustat and then established the metabolic pathway. It was concluded that the use of this generic intelligent "DDA + EL" approach for non-targeted analysis is a powerful tool for the discovery of unknown metabolites, even in complex plasma and urine matrices in the context of doping control.

Erythropoietic effects of vadadustat in patients with anemia associated with chronic kidney disease

Patients with chronic kidney disease (CKD) develop anemia largely because of inappropriately low erythropoietin (EPO) production and insufficient iron available to erythroid precursors. In four phase 3, randomized, open-label, clinical trials in dialysis-dependent and non-dialysis-dependent patients with CKD and anemia, the hypoxia-inducible factor prolyl hydroxylase inhibitor, vadadustat, was noninferior to the erythropoiesis-stimulating agent, darbepoetin alfa, in increasing and maintaining target hemoglobin concentrations. In these trials, vadadustat increased the concentrations of serum EPO, the numbers of circulating erythrocytes, and the numbers of circulating reticulocytes. Achieved hemoglobin concentrations were similar in patients treated with either vadadustat or darbepoetin alfa, but compared with patients receiving darbepoetin alfa, those receiving vadadustat had erythrocytes with increased mean corpuscular volume and mean corpuscular hemoglobin, while the red cell distribution width was decreased. Increased serum transferrin concentrations, as measured by total iron-binding capacity, combined with stable serum iron concentrations, resulted in decreased transferrin saturation in patients randomized to vadadustat compared with patients randomized to darbepoetin alfa. The decreases in transferrin saturation were associated with relatively greater declines in serum hepcidin and ferritin in patients receiving vadadustat compared with those receiving darbepoetin alfa. These results for serum transferrin saturation, hepcidin, ferritin, and erythrocyte indices were consistent with improved iron availability in the patients receiving vadadustat. Thus, overall, vadadustat had beneficial effects on three aspects of erythropoiesis in patients with anemia associated with CKD: increased endogenous EPO production, improved iron availability to erythroid cells, and increased reticulocytes in the circulation.

Pharmacokinetic Study of Vadadustat and High-Resolution Mass Spectrometric Characterization of its Novel Metabolites in Equines for the Purpose of Doping Control

BACKGROUND

Vadadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitor, is a substance which carries a lifetime ban in both horse racing and equestrian competition. A comprehensive metabolic study of vadadustat in horses has not been previously reported.

OBJECTIVE

Metabolism and elimination profiles of vadadustat in equine plasma and urine were studied for the purpose of doping control.

METHODS

A nasoesophageal administration of vadadustat (3 g/day for 3 days) was conducted on three thoroughbred mares. Potential metabolites were comprehensively detected by differential analysis of full-scan mass spectral data obtained from both in vitro studies with liver homogenates and post-administration samples using liquid chromatography high-resolution mass spectrometry. The identities of metabolites were further substantiated by product ion scans. Quantification methods were developed and validated for the establishment of the excretion profiles of the total vadadustat (free and conjugates) in plasma and urine.

RESULTS

A total of 23 in vivo and 14 in vitro metabolites (12 in common) were identified after comprehensive analysis. We found that vadadustat was mainly excreted into urine as the parent drug together with some minor conjugated metabolites. The elimination profiles of total vadadustat in post-administration plasma and urine were successfully established by using quantification methods equipped with alkaline hydrolysis for cleavage of conjugates such as methylated vadadustat, vadadustat glucuronide, and vadadustat glucoside.

CONCLUSION

Based on our study, for effective control of the misuse or abuse of vadadustat in horses, total vadadustat could successfully be detected for up to two weeks after administration in plasma and urine.

Renal hypoxia-HIF-PHD-EPO signaling in transition metal nephrotoxicity: friend or foe?

The kidney is the main organ that senses changes in systemic oxygen tension, but it is also the key detoxification, transit and excretion site of transition metals (TMs). Pivotal to oxygen sensing are prolyl-hydroxylases (PHDs), which hydroxylate specific residues in hypoxia-inducible factors (HIFs), key transcription factors that orchestrate responses to hypoxia, such as induction of erythropoietin (EPO). The essential TM ion Fe is a key component and regulator of the hypoxia–PHD–HIF–EPO (HPHE) signaling axis, which governs erythropoiesis, angiogenesis, anaerobic metabolism, adaptation, survival and proliferation, and hence cell and body homeostasis. However, inadequate concentrations of essential TMs or entry of non-essential TMs in organisms cause toxicity and disrupt health. Non-essential TMs are toxic because they enter cells and displace essential TMs by ionic and molecular mimicry, e. g. in metalloproteins. Here, we review the molecular mechanisms of HPHE interactions with TMs (Fe, Co, Ni, Cd, Cr, and Pt) as well as their implications in renal physiology, pathophysiology and toxicology. Some TMs, such as Fe and Co, may activate renal HPHE signaling, which may be beneficial under some circumstances, for example, by mitigating renal injuries from other causes, but may also promote pathologies, such as renal cancer development and metastasis. Yet some other TMs appear to disrupt renal HPHE signaling, contributing to the complex picture of TM (nephro-)toxicity. Strikingly, despite a wealth of literature on the topic, current knowledge lacks a deeper molecular understanding of TM interaction with HPHE signaling, in particular in the kidney. This precludes rationale preventive and therapeutic approaches to TM nephrotoxicity, although recently activators of HPHE signaling have become available for therapy.

Clinical Potential of Hypoxia Inducible Factors Prolyl Hydroxylase Inhibitors in Treating Nonanemic Diseases

Hypoxia inducible factors (HIFs) and their regulatory hydroxylases the prolyl hydroxylase domain enzymes (PHDs) are the key mediators of the cellular response to hypoxia. HIFs are normally hydroxylated by PHDs and degraded, while under hypoxia, PHDs are suppressed, allowing HIF-α to accumulate and transactivate multiple target genes, including erythropoiesis, and genes participate in angiogenesis, iron metabolism, glycolysis, glucose transport, cell proliferation, survival, and so on. Aiming at stimulating HIFs, a group of small molecules antagonizing HIF-PHDs have been developed. Of these HIF-PHDs inhibitors (HIF-PHIs), roxadustat (FG-4592), daprodustat (GSK-1278863), vadadustat (AKB-6548), molidustat (BAY 85-3934) and enarodustat (JTZ-951) are approved for clinical usage or have progressed into clinical trials for chronic kidney disease (CKD) anemia treatment, based on their activation effect on erythropoiesis and iron metabolism. Since HIFs are involved in many physiological and pathological conditions, efforts have been made to extend the potential usage of HIF-PHIs beyond anemia. This paper reviewed the progress of preclinical and clinical research on clinically available HIF-PHIs in pathological conditions other than CKD anemia.

Erythropoietin-Stimulating Agent Hyporesponsiveness in Patients Living with Chronic Kidney Disease

BACKGROUND

Erythropoietin-stimulating agent (ESA) hyporesponsiveness is commonly observed in patients with anemia secondary to chronic kidney disease (CKD). Because of its complexity, a global consensus on how we should define ESA hyporesponsiveness remains unavailable. The reported prevalence and demographic information on ESA hyporesponsiveness within the CKD population are variable with no consensus definition.

SUMMARY

ESA hyporesponsiveness is defined as having no increase in hemoglobin concentration from baseline after the first month of treatment on appropriate weight-based dosing. The important factors associated with ESA hyporesponsiveness include absolute or functional iron deficiency, inflammation, and uremia. Hepcidin has been demonstrated to play an important role in this process. Mineral bone disease secondary to CKD and non-iron malnutrition among other factors are also associated with ESA hyporesponsiveness. There is continued debate toward determining a gold-standard treatment pathway to manage ESA hyporesponsiveness. The development of hypoxia-inducing factor-stabilizers brings new insights and opportunities in the management of ESA hyporesponsiveness.

KEY MESSAGE

Management of ESA hyporesponsiveness involves a comprehensive multidisciplinary team approach to address its risk factors. The progression of basic and clinical research on identifying risk factors and management of ESA hyporesponsiveness brings greater hope on finding solutions to eventually tackling one of the most difficult problems in the topic of anemia in CKD.

Effect of Phosphate Binders and a Dietary Iron Supplement on the Pharmacokinetics of a Single Dose of Vadadustat in Healthy Adults

Vadadustat is a hypoxia-inducible factor prolyl-hydroxylase inhibitor being developed for the treatment of anemia in patients with chronic kidney disease. Sequelae of chronic kidney disease include hyperphosphatemia and anemia, which are frequently treated with phosphate binders and iron supplements, respectively. Two studies evaluating the pharmacokinetics, safety, and tolerability of a single oral dose of vadadustat coadministered with a phosphate binder or iron supplement were conducted in healthy adult participants. In study 1, 54 healthy women and men were administered vadadustat (300 mg) alone and 1 hour before, concurrently with, or 2 hours after a phosphate binder (sevelamer carbonate 1600 mg, calcium acetate 1334 mg, or ferric citrate 2000 mg). In study 2, 10 healthy men were administered vadadustat (450 mg) alone and concomitantly with the oral iron supplement ferrous sulfate (325 mg [equivalent to 65 mg of elemental iron]). Vadadustat exposure was reduced by coadministration with sevelamer carbonate, calcium acetate, ferric citrate, or ferrous sulfate. Geometric least squares mean ratios for area under the concentration-time curve from time 0 to infinity were reduced 37% to 55% by phosphate binders and 46% by ferrous sulfate. However, when vadadustat was administered 1 hour before phosphate binders, 90% confidence intervals for vadadustat exposure were within the no-effect boundaries of +50% to -33%, indicating that drug-drug interactions can be reduced by administering vadadustat 1 hour before phosphate binders. Vadadustat was well tolerated when administered in conjunction with phosphate binders or an iron supplement.

Hypoxia-inducible factor-prolyl hydroxylase inhibitors for renal anemia in chronic kidney disease: Advantages and disadvantages

Anemia is a common feature and complication of chronic kidney disease (CKD). Erythropoiesis-stimulating agents (ESAs) and recombinant human erythropoietin have been used widely in renal anemia treatment. Recently, hypoxia-inducible factor-prolyl hydroxylase domain inhibitors (HIF-PHIs) that may improve the treatment of renal anemia patients were launched. Previous studies indicated that HIF-PHIs may decrease hepcidin levels and modulate iron metabolism, thereby increasing total iron-binding capacity and reducing the need for iron supplementation. Furthermore, HIF-PHIs can reduce inflammation and oxidative stress in CKD. Recombinant erythropoietin has become a routine treatment for patients with CKD and end-stage renal disease with relatively few adverse effects. However, higher doses of recombinant erythropoietin have been demonstrated to be an independent predictor of mortality in patients under hemodialysis. Phase III clinical trials of HIF-PHIs in patients with anemia and dialysis-dependent CKD have shown their efficacy and safety in both non-dialysis and dialysis CKD patients. However, HIFα binds to specific hypoxia-response elements in the vascular endothelial growth factor or retinoic acid-related orphan receptor gamma t (RORγt) promoter, which may be involved in the progression of cancer, psoriasis, and rheumatoid arthritis. In this paper, we have summarized the mechanism, clinical application, and clinical trials of HIF-PHIs in the treatment of renal anemia and aimed to provide an overview of the new drugs in clinical practice, as well as reconsider the advantages and disadvantages of HIF-PHIs and ESAs. Presently, there are not enough clinical studies examining the effects of long-term administration of HIF-PHIs. Therefore, further studies will be needed.

Global Phase 3 programme of vadadustat for treatment of anaemia of chronic kidney disease: rationale, study design and baseline characteristics of dialysis-dependent patients in the INNO2VATE trials

Background

Erythropoiesis-stimulating agents (ESAs) are currently the mainstay of treatment for anaemia of chronic kidney disease (CKD). Vadadustat is an investigational oral hypoxia-inducible factor prolyl-hydroxylase inhibitor that stimulates endogenous erythropoietin formation. The INNO₂VATE programme comprises two studies designed to evaluate the safety and efficacy of vadadustat versus the ESA darbepoetin alfa in ameliorating anaemia in patients with dialysis-dependent CKD (DD-CKD). Here we describe the trial design along with patient demographics and baseline characteristics.

Methods

Two Phase 3, open-label, sponsor-blind, active-controlled trials enrolled adults with anaemia of CKD who recently initiated dialysis and had limited ESA exposure (incident DD-CKD trial) or were receiving maintenance dialysis with ESA treatment (prevalent DD-CKD trial). Study periods include correction/conversion (Weeks 0–23), maintenance (Weeks 24–52), long-term treatment (Weeks 53 to end of treatment) and safety follow-up. The primary safety endpoint is the time to the first major adverse cardiovascular event and the primary efficacy endpoint is the change in haemoglobin (baseline to Weeks 24–36).

Results

A total of 369 and 3554 patients were randomized in the incident DD-CKD and prevalent DD-CKD trials, respectively. Demographics and baseline characteristics were similar among patients in both trials and comparable to those typically observed in DD-CKD.

Conclusions

The two INNO₂VATE trials will provide important information on the safety and efficacy of a novel approach for anaemia management in a diverse DD-CKD population. Demographics and baseline characteristics of enrolled patients suggest that study results will be representative for a large proportion of the DD-CKD population.

Challenging patient phenotypes in the management of anaemia of chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is often complicated by anaemia, which is associated with disease progression and increased hospital visits, decreased quality of life, and increased mortality.

METHODS

A comprehensive literature search of English language peer-reviewed articles in PubMed/MedLine published between 1998 and 2020 related to the treatment of anaemia of CKD was conducted. The United States Renal Database System and Dialysis Outcomes and Practice Patterns Study (DOPPS) data reports, the Centers for Disease Control and Prevention and the US Food and Drug Administration websites, and published congress abstracts in 2020 were surveyed for relevant information.

RESULTS

Subgroups of patients with anaemia of CKD present a clinical challenge throughout the disease spectrum, including those with end-stage kidney disease, advanced age or resistance to or ineligibility for current standards of care (ie, oral or intravenous iron supplementation, erythropoietin-stimulating agents and red blood cell transfusions). In addition, those with an increased risk of adverse events because of comorbid conditions, such as cardiovascular diseases or diabetes, comprise special populations of patients with an unmet need for interventions to improve clinical outcomes. These comorbidities must be managed in parallel and may have a synergistic effect on overall disease severity.

CONCLUSIONS

Several therapies provide promising opportunities to address gaps with a standard of care, including hypoxia-inducible factor prolyl hydroxylase inhibitors, which stimulate haematopoiesis through promoting modest increases in serum erythropoietin and improved iron homeostasis. The critical issues in the management of anaemia of CKD in these challenging phenotypes and the clinical utility of new therapeutic agents in development for the treatment of anaemia of CKD should be assessed and the information should be made available to healthcare providers.

Current Status of Renal Anemia Pharmacotherapy-What Can We Offer Today

Chronic kidney disease (CKD) is one of the fastest-growing major causes of death internationally. Better treatment of CKD and its complications is crucial to reverse this negative trend. Anemia is a frequent complication of CKD and is associated with unfavorable clinical outcomes. It is a devastating complication of progressive kidney disease, that negatively affects also the quality of life. The prevalence of anemia increases in parallel with CKD progression. The aim of this review is to summarize the current knowledge on therapy of renal anemia. Iron therapy, blood transfusions, and erythropoietin stimulating agents are still the mainstay of renal anemia treatment. There are several novel agents on the horizon that might provide therapeutic opportunities in CKD. The potential therapeutic options target the hepcidin–ferroportin axis, which is the master regulator of iron homeostasis, and the BMP-SMAD pathway, which regulates hepcidin expression in the liver. An inhibition of prolyl hydroxylase is a new therapeutic option becoming available for the treatment of anemia in CKD patients. This new class of drugs stimulates the synthesis of endogenous erythropoietin and increases iron availability. We also summarized the effects of prolyl hydroxylase inhibitors on iron parameters, including hepcidin, as their action on the hematological parameters. They could be of particular interest in the out-patient population with CKD and patients with ESA hyporesponsiveness. However, current knowledge is limited and still awaits clinical validation. One should be aware of the potential risks and benefits of novel, sophisticated therapies.

In Vitro and Clinical Pharmacokinetic Studies of the Effects of Iron-containing Agents on Vadadustat, an Oral Hypoxia-inducible Factor-Prolyl Hydroxylase Inhibitor

PURPOSE

Vadadustat is an oral hypoxia-inducible factor-prolyl hydroxylase inhibitor approved in Japan for the treatment of anemia in chronic kidney disease. This study investigated drug-drug interactions between vadadustat and oral iron supplements or iron-containing phosphate binders commonly used in Japanese clinical practice by conducting in vitro mechanistic and clinical pharmacokinetic studies.

METHODS

In the in vitro assessment, chelate formation of vadadustat with iron-containing agents was investigated in water and in a fed-state simulated intestinal fluid. Chelate formation was assessed by observation of a chelate-specific color, and the concentration of vadadustat was determined. In the single-dose, open-label, randomized, crossover clinical study, healthy male participants received 150 mg of vadadustat with or without oral iron-containing agents. Pharmacokinetic data were collected for up to 24 hours after vadadustat administration. Participants were monitored for adverse events during the study.

FINDINGS

Vadadustat formed a chelate precipitate with ferrous sulfate and ferric nitrate, as shown by development of a specific bright orange color in water. The proportions of vadadustat dissolved in the supernatant were 2% and 18%, respectively. Vadadustat did not form a chelate precipitate in a fed-state simulated intestinal fluid in the presence of sodium ferrous citrate, ferric citrate hydrate, or sucroferric oxyhydroxide; the proportion of vadadustat in supernatant ranged from 63% to 89%. In the clinical pharmacokinetic study, coadministration of vadadustat with sodium ferrous citrate, ferric citrate hydrate, sucroferric oxyhydroxide, or ferrous sulfate decreased the AUC_0-∞ by 54.0% to 89.7% and C_max by 42.1% to 91.9%. No serious adverse events were reported.

IMPLICATIONS

Chelate formation of vadadustat with iron-containing agents was confirmed by in vitro analysis and depended on the type of iron-containing agent. The AUC_0-∞ and C_max of vadadustat decreased when coadministered with oral iron-containing agents. Our data suggest that the decreases in AUC_0-∞ and C_max are a result of chelation in the gastrointestinal tract; therefore, coadministration of iron-containing agents with vadadustat should use a dosing interval. ClinicalTrials.gov Identifier: NCT03645863.

Anemia: A Connection Between Heart Failure and Kidney Failure

Erythropoiesis-stimulating agents (ESAs) have improved the quality of life and reduced the need for transfusions in patients with chronic kidney disease. However, randomized trials showed no benefit but possible safety issues following high doses of ESAs given to reach normal hemoglobin levels. Iron therapy is used together with ESA; when given proactively, it may reduce the risk of mortality and cardiovascular events in hemodialysis patients. Recent trials also showed benefits of intravenous iron therapy in patients with heart failure. New drugs for correcting anemia may retain the present efficacy of ESAs as antianemic drugs and reduce cardiovascular risks.

Managing Anemia across the Stages of Kidney Disease in Those Hyporesponsive to Erythropoiesis-Stimulating Agents

BACKGROUND

Patients with CKD frequently have anemia that results from iron-restricted erythropoiesis and inflammation. Anemia of CKD is currently managed with iron supplements and erythropoiesis-stimulating agents (ESAs) to promote erythropoiesis and with RBC transfusion in severe cases. Hyporesponse to ESAs, or the need for larger than usual doses to attain a given hemoglobin (Hb) level, is associated with increased morbidity and mortality and presents a pressing clinical challenge, particularly for patients on dialysis. This paper reviews ESA hyporesponse and potential new therapeutic options in the management of anemia of CKD.

SUMMARY

The most common causes of ESA hyporesponse include iron deficiency and inflammation, and to a lesser degree, secondary hyperparathyroidism, inadequate dialysis, malnutrition, and concomitant medications. Management of ESA hyporesponse is multipronged and involves treating low level infections, ensuring adequate nutrition, and optimizing iron status and dialysis modality, although some patients can remain refractory. Inflammation directly increases production and secretion of hepcidin, contributes to an impaired response to hypoxia, and suppresses proliferation of erythroid progenitors. Coordination of renal and hepatic erythropoietin (EPO) production and iron metabolism is under the control of hypoxia-inducible factors (HIF), which are in turn regulated by HIF-prolyl hydroxylases (HIF-PHs). HIF-PHs and hepcidin are therefore attractive potential drug targets particularly in patients with ESA hyporesponse. Several oral HIF-PH inhibitors have been evaluated in patients with anemia of CKD and have been shown to increase Hb and reduce hepcidin regardless of inflammation, iron status, or dialysis modality. These sustained effects are achieved through more modest increases in endogenous EPO compared with ESAs. Key Messages: Treatments that address ESA hyporesponse remain a significant unmet clinical need in patients with anemia of CKD. New therapies such as HIF-PH inhibitors have the potential to address fundamental aspects of ESA hyporesponse and provide a new therapeutic option in these patients.

Phase 3 Randomized Study Comparing Vadadustat with Darbepoetin Alfa for Anemia in Japanese Patients with Nondialysis-Dependent CKD

BACKGROUND

Standard care for treating anemia in patients with CKD includes use of erythropoiesis-stimulating agents, which sometimes involves increased risks of cardiovascular morbidity and mortality. Previous studies in patients with anemia and nondialysis-dependent CKD (NDD-CKD) found significantly elevated hemoglobin levels with use of vadadustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, compared with placebo.

METHODS

In this phase 3, open-label, active-controlled noninferiority trial, we randomized 304 Japanese adults with anemia in NDD-CKD (including erythropoiesis-stimulating agent users and nonusers) to oral vadadustat or subcutaneous darbepoetin alfa for 52 weeks. The primary efficacy end point was average hemoglobin at weeks 20 and 24. Safety data included adverse events (AEs) and serious AEs.

RESULTS

A total of 151 participants received vadadustat and 153 received darbepoetin alfa. Least squares mean of the average hemoglobin at weeks 20 and 24 was 11.66 (95% confidence interval [95% CI], 11.49 to 11.84) g/dl for vadadustat and 11.93 (95% CI, 11.76 to 12.10) g/dl for darbepoetin alfa. The 95% CIs for both treatments were within the target hemoglobin range (11.0-13.0 g/dl), and the lower 95% confidence limit for the difference between groups (-0.50 g/dl) was above the predefined noninferiority margin (-0.75 g/dl), demonstrating noninferiority of vadadustat to darbepoetin alfa. Similar proportions of patients in each group reported AEs and serious AEs. The most frequent AEs with vadadustat were nasopharyngitis, diarrhea, and constipation.

CONCLUSIONS

In Japanese patients with NDD-CKD, vadadustat was noninferior to darbepoetin alfa, was effective up to week 52 in terms of average hemoglobin, and was generally well tolerated. These results suggest that vadadustat may be a potential treatment for anemia in this patient population.

Vadadustat: First Approval

Vadadustat (VAFSEO^®) is a prolyl hydroxylase inhibitor being developed by Akebia Therapeutics, Inc. (Akebia) for the treatment of anaemia associated with chronic kidney disease (CKD). Akebia is collaborating with Mitsubishi Tanabe Pharma Corporation on the development and commercialization of vadadustat in Japan and with Otsuka Pharmaceutical Co. Ltd on the development and commercialization of vadadustat in the USA, the EU and certain other territories. The drug is approved in Japan for use in adult patients with anaemia associated with CKD and regulatory submissions are planned in the USA and the EU. This article summarizes the milestones in the development of vadadustat leading to this first approval.

A phase 3, open-label, single-arm study of vadadustat for anemia in chronic kidney disease for Japanese patients on hemodialysis not receiving erythropoiesis-stimulating agents

Vadadustat is an oral hypoxia‐inducible factor prolyl hydroxylase inhibitor approved in Japan for the treatment of anemia in patients with chronic kidney disease (CKD). This phase 3, open‐label, single‐arm study evaluated the efficacy and safety of vadadustat in 24 Japanese patients with CKD‐associated anemia on hemodialysis who were not receiving erythropoiesis‐stimulating agents (ESAs). Patients received vadadustat for 24 weeks; the starting dose was 300 mg/day and doses were adjusted to achieve the target hemoglobin (Hb) range of 10.0–12.0 g/dL. The least squares mean of average Hb at Weeks 20 and 24 (95% confidence interval) was 10.75 g/dL (10.35, 11.14). The most common adverse event was shunt stenosis (25.0%). Adverse drug reactions (diarrhea and vomiting) occurred in two patients (8.3%) and the severity was mild. Vadadustat increased and maintained Hb levels within the target range and was generally well‐tolerated in Japanese patients with anemia on hemodialysis not receiving ESAs.

Cardiovascular safety and efficacy of vadadustat for the treatment of anemia in non-dialysis-dependent CKD: Design and baseline characteristics

Current clinical practice guidelines for anemia management in non-dialysis-dependent chronic kidney disease (NDD-CKD) recommend the use of erythropoiesis-stimulating agents (ESAs) as standard of care. Vadadustat, an investigational oral hypoxia-inducible factor prolyl-hydroxylase inhibitor, stimulates endogenous erythropoietin production. The PRO₂TECT program comprises 2 global, Phase 3, randomized, open-label, active-controlled, sponsor-blind clinical trials to evaluate safety and efficacy of vadadustat vs darbepoetin alfa in adult patients with anemia associated with NDD-CKD. Patients recruited into the ESA-untreated NDD-CKD trial (N = 1751) had hemoglobin <10 g/dL and had not received an ESA within 8 weeks prior to inclusion in the study. Patients recruited into the ESA-treated NDD-CKD trial (N = 1725) had hemoglobin between 8 and 11 g/dL (US) or 9 and 12 g/dL (non-US) and were actively treated with an ESA for anemia associated with CKD. Trial periods in both trials include (1) correction/conversion (weeks 0-23); (2) maintenance (weeks 24-52); (3) long-term treatment (week 53 to end of treatment); and (4) safety follow-up (end-of-treatment to 4 weeks later). The primary safety endpoint is time to first adjudicated major adverse cardiovascular event, defined as all-cause mortality, nonfatal myocardial infarction, or nonfatal stroke, pooled across both trials. The primary efficacy endpoint in each trial is change in hemoglobin from baseline to primary evaluation period (weeks 24-36), comparing vadadustat vs darbepoetin alfa treatment groups. Demographics and baseline characteristics are similar among patients in both trials and broadly representative of the NDD-CKD population. These trials will help to evaluate the safety and efficacy of vadadustat for management of anemia associated with NDD-CKD.

Safety and Efficacy of Vadadustat for Anemia in Patients Undergoing Dialysis

BACKGROUND

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, a class of compounds that stimulate endogenous erythropoietin production.

METHODS

We conducted two randomized, open-label, noninferiority phase 3 trials to evaluate the safety and efficacy of vadadustat, as compared with darbepoetin alfa, in patients with anemia and incident or prevalent dialysis-dependent chronic kidney disease (DD-CKD). The primary safety end point, assessed in a time-to-event analysis, was the first occurrence of a major adverse cardiovascular event (MACE, a composite of death from any cause, a nonfatal myocardial infarction, or a nonfatal stroke), pooled across the trials (noninferiority margin, 1.25). A key secondary safety end point was the first occurrence of a MACE plus hospitalization for either heart failure or a thromboembolic event. The primary and key secondary efficacy end points were the mean change in hemoglobin from baseline to weeks 24 to 36 and from baseline to weeks 40 to 52, respectively, in each trial (noninferiority margin, -0.75 g per deciliter).

RESULTS

A total of 3923 patients were randomly assigned in a 1:1 ratio to receive vadadustat or darbepoetin alfa: 369 in the incident DD-CKD trial and 3554 in the prevalent DD-CKD trial. In the pooled analysis, a first MACE occurred in 355 patients (18.2%) in the vadadustat group and in 377 patients (19.3%) in the darbepoetin alfa group (hazard ratio, 0.96; 95% confidence interval [CI], 0.83 to 1.11). The mean differences between the groups in the change in hemoglobin concentration were -0.31 g per deciliter (95% CI, -0.53 to -0.10) at weeks 24 to 36 and -0.07 g per deciliter (95% CI, -0.34 to 0.19) at weeks 40 to 52 in the incident DD-CKD trial and -0.17 g per deciliter (95% CI, -0.23 to -0.10) and -0.18 g per deciliter (95% CI, -0.25 to -0.12), respectively, in the prevalent DD-CKD trial. The incidence of serious adverse events in the vadadustat group was 49.7% in the incident DD-CKD trial and 55.0% in the prevalent DD-CKD trial, and the incidences in the darbepoetin alfa group were 56.5% and 58.3%, respectively.

CONCLUSIONS

Among patients with anemia and CKD who were undergoing dialysis, vadadustat was noninferior to darbepoetin alfa with respect to cardiovascular safety and correction and maintenance of hemoglobin concentrations. (Funded by Akebia Therapeutics and Otsuka Pharmaceutical; INNO₂VATE ClinicalTrials.gov numbers, NCT02865850 and NCT02892149.).

Targeting alveolar-specific succinate dehydrogenase A attenuates pulmonary inflammation during acute lung injury

Acute lung injury (ALI) is an inflammatory lung disease, which manifests itself in patients as acute respiratory distress syndrome (ARDS). Previous studies have implicated alveolar-epithelial succinate in ALI protection. Therefore, we hypothesized that targeting alveolar succinate dehydrogenase SDH A would result in elevated succinate levels and concomitant lung protection. Wild-type (WT) mice or transgenic mice with targeted alveolar-epithelial Sdha or hypoxia-inducible transcription factor Hif1a deletion were exposed to ALI induced by mechanical ventilation. Succinate metabolism was assessed in alveolar-epithelial via mass spectrometry as well as redox measurements and evaluation of lung injury. In WT mice, ALI induced by mechanical ventilation decreased SDHA activity and increased succinate in alveolar-epithelial. In vitro, cell-permeable succinate decreased epithelial inflammation during stretch injury. Mice with inducible alveolar-epithelial Sdha deletion (Sdha^loxp/loxp SPC-CreER mice) revealed reduced lung inflammation, improved alveolar barrier function, and attenuated histologic injury. Consistent with a functional role of succinate to stabilize HIF, Sdha^loxp/loxp SPC-CreER experienced enhanced Hif1a levels during hypoxia or ALI. Conversely, Hif1a^loxp/loxp SPC-CreER showed increased inflammation with ALI induced by mechanical ventilation. Finally, wild-type mice treated with intra-tracheal dimethlysuccinate were protected during ALI. These data suggest that targeting alveolar-epithelial SDHA dampens ALI via succinate-mediated stabilization of HIF1A. Translational extensions of our studies implicate succinate treatment in attenuating alveolar inflammation in patients suffering from ARDS.

Hypoxia-inducible factor-prolyl hydroxylase inhibitors in the treatment of anemia of chronic kidney disease

Hypoxia-inducible factor-prolyl hydroxylase domain inhibitors (HIF-PHIs) are a promising new class of orally administered drugs currently in late-stage global clinical development for the treatment of anemia of chronic kidney disease (CKD). HIF-PHIs activate the HIF oxygen-sensing pathway and are efficacious in correcting and maintaining hemoglobin levels in patients with non-dialysis- and dialysis-dependent CKD. In addition to promoting erythropoiesis through the increase in endogenous erythropoietin production, HIF-PHIs reduce hepcidin levels and modulate iron metabolism, providing increases in total iron binding capacity and transferrin levels, and potentially reducing the need for i.v. iron supplementation. Furthermore, HIF-activating drugs are predicted to have effects that extend beyond erythropoiesis. This review summarizes clinical data from current HIF-PHI trials in patients with anemia of CKD, discusses mechanisms of action and pharmacologic properties of HIF-PHIs, and deliberates over safety concerns and potential impact on anemia management in patients with CKD.

Anemia of cardiorenal syndrome

Cardiorenal syndrome includes a spectrum of disorders of the kidneys and heart in which loss of function in one organ contributes to reduced function in the other organ. Cardiorenal syndrome is frequently complicated by comorbid anemia, which leads to reciprocal and progressive cardiac and renal deterioration. The triad of heart failure, chronic kidney disease (CKD), and anemia is termed cardiorenal anemia syndrome (CRAS). There are currently no evidence-based recommendations for managing patients with CRAS; however, the treatment of these patients is multifactorial. Not only must the anemia be controlled, but heart failure and kidney injury must be addressed, in addition to other comorbidities. Intravenous iron and erythropoiesis-stimulating agents are the mainstays of treatment for anemia of CKD, addressing both iron and erythropoiesis deficiencies. Since erythropoiesis-stimulating agent therapy can be associated with adverse outcomes at higher doses in patients with CKD and is not used in routine practice in patients with heart failure, treatment options for managing anemia in patients with CRAS are limited. Several new therapies, particularly the hypoxia-inducible factor-prolyl hydroxylase inhibitors, are currently under clinical development. The hypoxia-inducible factor-prolyl hydroxylase inhibitors have shown promising results for treating anemia of CKD in clinical trials and may confer benefits in patients with CRAS, potentially addressing some of the limitations of erythropoiesis-stimulating agents. Updated clinical practice guidelines for the screening and management of anemia in cardiorenal syndrome, in light of potential new therapies and clinical evidence, would improve the clinical outcomes of patients with this complex syndrome.

Iron metabolism and management: focus on chronic kidney disease

Anemia is common in patients with chronic kidney disease (CKD) and results from the dysregulation of iron metabolism and erythropoiesis. Hepcidin is a key regulator of iron availability and leads to iron sequestration during the state of iron repletion. Decreases in the level of hepcidin in the presence of hypoxia and/or iron limitation allow for greater iron availability for erythropoiesis. However, kidney excretion of hepcidin decreases as the severity of CKD increases, whereas production of hepcidin is increased under inflammatory conditions often present in patients with CKD, both of which contribute to anemia. Assessment of iron status is, therefore, essential in the treatment of anemia. However, current laboratory tests for the determination of the adequate supply of iron have many limitations, including diurnal variation in the levels of biomarkers, lack of standardized reference methods across laboratories, and confounding by the presence of inflammation. In addition, the current treatment paradigm for anemia of CKD can further disrupt iron homeostasis; for example, treatment with erythropoiesis-stimulating agents in the absence of supplemental iron can induce functional iron deficiency. Moreover, supplemental iron can further increase levels of hepcidin. Several novel therapies, including hypoxia-inducible factor prolyl hydroxylase inhibitors and hepcidin inhibitors/antagonists, have shown promise in attenuating the levels and/or activity of hepcidin in anemia of CKD, thus ensuring the availability of iron for erythropoiesis.

Amelioration of chronic kidney disease-associated anemia by vadadustat in mice is not dependent on erythroferrone

Vadadustat is an investigational hypoxia-inducible factor prolyl hydroxylase inhibitor that increases endogenous erythropoietin production and has been shown to decrease hepcidin levels, ameliorate iron restriction, and increase hemoglobin concentrations in anemic patients with chronic kidney disease (CKD). In studies of physiological responses to other erythropoietic stimuli, erythropoietin induced erythroblast secretion of erythroferrone (ERFE), which acts on the liver to suppress hepcidin production and mobilize iron for erythropoiesis. We therefore investigated whether vadadustat effects on erythropoiesis and iron metabolism are dependent on ERFE. Wild type and ERFE knockout mice with and without CKD were treated with vadadustat or vehicle. In both wild type and ERFE knockout CKD models, vadadustat was similarly effective, as evidenced by normalized hemoglobin concentrations, increased expression of duodenal iron transporters, lower serum hepcidin levels, and decreased tissue iron concentrations. This is consistent with ERFE-independent increased iron mobilization. Vadadustat treatment also lowered serum urea nitrogen and creatinine concentrations and decreased expression of kidney fibrosis markers. Lastly, vadadustat affected fibroblast growth factor 23 (FGF23) profiles: in non-CKD mice, vadadustat increased plasma total FGF23 out of proportion to intact FGF23, consistent with the known effects of hypoxia-inducible factor-1α and erythropoietin on FGF23 production and metabolism. However, in the mice with CKD, vadadustat markedly decreased both total and intact FGF23, effects likely contributed to by the reduced loss of kidney function. Thus, in this CKD model, vadadustat ameliorated anemia independently of ERFE, improved kidney parameters, and decreased FGF23. How vadadustat affects CKD progression in humans warrants future studies.

Effect of Moderate Hepatic Impairment on the Pharmacokinetics of Vadadustat, an Oral Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor

Vadadustat is a hypoxia-inducible factor prolyl hydroxylase inhibitor in development for the treatment of anemia of chronic kidney disease. This phase 1, open-label, parallel-group, single-dose study evaluated the pharmacokinetics of 450-mg vadadustat in adults with moderate hepatic impairment (Child-Pugh class B) vs those with normal hepatic function. Primary end points were area under the plasma concentration-time curve (AUC) from dosing to last concentration and to infinity, as well as maximum concentration (C_max ); additional pharmacokinetic parameters included time to C_max (T_max ) and half-life. Safety and tolerability were also assessed. All enrolled participants (n = 16) completed the study. Demographics were similar in both groups (overall, 100% White; 62.5% female; mean age, 59.2 years). Vadadustat plasma exposure was higher in the moderate hepatic impairment group, whereas maximum concentration was similar between groups. Point estimates of the hepatic impairment : normal geometric mean ratios (90% confidence interval) for AUC from dosing to last concentration, AUC from dosing to infinity, and C_max were 1.05 (0.82-1.35), 1.06 (0.82-1.36), and 1.02 (0.79-1.32), respectively. Mean elimination half-life was 5.8 and 7.8 hours in the normal and hepatic impairment groups, respectively. Treatment-emergent adverse events were mostly mild in severity, and vadadustat was generally well tolerated. In conclusion, moderate hepatic impairment did not significantly impact vadadustat systemic exposure, and mild hepatic impairment is unlikely to alter vadadustat exposure.

ESA, Iron Therapy and New Drugs: Are There New Perspectives in the Treatment of Anaemia?

Anemia is a well-known consequence of chronic kidney disease (CKD); it is mainly due to a relative insufficiency of erythropoietin synthesis by the failing kidneys. Over the years, the combination of erythropoiesis stimulating agents (ESA) and iron has become the standard of care of anemia. All ESAs effectively increase hemoglobin (Hb) levels in a substantial percentage of patients. However, in the last decade, their use has been surrounded by safety issues in increased cardiovascular risk, especially when used at high doses in inflamed and hyporesponsive patients. This has led to the definition of a more cautious Hb target. Iron deficiency is very frequent in CKD patients, with a higher frequency in non-dialysis patients. Traditionally, iron supplementation is mostly used as supportive therapy for anemia control. However, the concept is growing that intravenous iron therapy per se could be beneficial in the presence of heart failure. A new class of drugs, prolyl hydroxylase domain (PHD) inhibitors (PHD inhibitors) is becoming available for the treatment of anemia in CKD patients. Theoretically, these agents have a number of advantages, the main ones being that of stimulating the synthesis of endogenous erythropoietin and increasing iron availability. The impact of their future use in clinical practice is still to be defined. Another possible strategy could be targeting serum hepcidin and its related pathways. This possibility is fascinating from the scientific point of view, but at present its development phase is still far from clinical application.

Adenosine at the Interphase of Hypoxia and Inflammation in Lung Injury

Hypoxia and inflammation often coincide in pathogenic conditions such as acute respiratory distress syndrome (ARDS) and chronic lung diseases, which are significant contributors to morbidity and mortality for the general population. For example, the recent global outbreak of Coronavirus disease 2019 (COVID-19) has placed viral infection-induced ARDS under the spotlight. Moreover, chronic lung disease ranks the third leading cause of death in the United States. Hypoxia signaling plays a diverse role in both acute and chronic lung inflammation, which could partially be explained by the divergent function of downstream target pathways such as adenosine signaling. Particularly, hypoxia signaling activates adenosine signaling to inhibit the inflammatory response in ARDS, while in chronic lung diseases, it promotes inflammation and tissue injury. In this review, we discuss the role of adenosine at the interphase of hypoxia and inflammation in ARDS and chronic lung diseases, as well as the current strategy for therapeutic targeting of the adenosine signaling pathway.

Burden of Anemia in Chronic Kidney Disease: Beyond Erythropoietin

Anemia is a frequent comorbidity of chronic kidney disease (CKD) and is associated with a considerable burden because of decreased patient health-related quality of life and increased healthcare resource utilization. Based on observational data, anemia is associated with an increased risk of CKD progression, cardiovascular events, and all-cause mortality. The current standard of care includes oral or intravenous iron supplementation, erythropoiesis-stimulating agents, and red blood cell transfusion. However, each of these therapies has its own set of population-specific patient concerns, including increased risk of cardiovascular disease, thrombosis, and mortality. Patients receiving dialysis or those who have concurrent diabetes or high blood pressure may be at greater risk of developing these complications. In particular, treatment with high doses of erythropoiesis-stimulating agents has been associated with increased rates of hospitalization, cardiovascular events, and mortality. Resistance to erythropoiesis-stimulating agents remains a therapeutic challenge in a subset of patients. Hypoxia-inducible factor transcription factors, which regulate several genes involved in erythropoiesis and iron metabolism, can be stabilized by a new class of drugs that act as inhibitors of hypoxia-inducible factor prolyl-hydroxylase enzymes to promote erythropoiesis and elevate hemoglobin levels. Here, we review the burden of anemia of chronic kidney disease, the shortcomings of current standard of care, and the potential practical advantages of hypoxia-inducible factor prolyl-hydroxylase inhibitors in the treatment of patients with anemia of CKD.

Vadadustat for anemia in chronic kidney disease patients on peritoneal dialysis: A phase 3 open-label study in Japan

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor for the treatment of anemia in patients with chronic kidney disease (CKD). This phase 3, open-label, 24-week single-arm study evaluated the efficacy and safety of vadadustat in 42 Japanese CKD patients with anemia undergoing peritoneal dialysis. Patients received oral vadadustat for 24 weeks, initiated at 300 mg/day and doses were adjusted to achieve the target hemoglobin (Hb) range of 11.0-13.0 g/dL. Least squares mean of average Hb at weeks 20 and 24 was 11.35 g/dL, which was within the target range. The most frequent adverse events were catheter site infections (23.8%), which were not related to vadadustat treatment. Vadadustat was generally well tolerated and effective in controlling Hb levels within the target range, indicating the usefulness of vadadustat for treating anemia in Japanese CKD patients undergoing peritoneal dialysis.

Hypoxia-Inducible Factor-Proline Hydroxylase Inhibitor in the Treatment of Renal Anemia

Background

Anemia is a common complication in CKD patients. Despite the use of iron and erythropoietin-stimulating agents, the control rate of anemia in CKD is not satisfying. Novel drugs are needed for anemia correction.

Summary

HIF-PHI, hypoxia-inducible factor-proline hydroxylase inhibitor, a novel class of therapeutic agents, has been developed to treat anemia in CKD patients. Its main effects comprised boosting EPO production, enhancing iron utilization, and suppressing hepcidin production. Several stage 2 and stage 3 clinical trials have been run to test its efficacy and safety in both nondialysis and dialysis patients, of which the results are very encouraging. Here, we summarize the mechanism, clinical applications, and clinical trials of HIF-PHI in treating renal anemia in order to give an overview of the new drug in clinical practices.

Key Messages

HIF-PHI is a novel therapeutic agent of treating renal anemia in CKD patients. It is quite effective in improving anemia, which is unaffected by inflammation. Besides, it may ameliorate lipid metabolism as well. Furthermore, the oral form may improve patients' compliances with treatment. Thus, it may be a good alternative of anemia correction in CKD patients.

Recommendations by the Asian Pacific society of nephrology (APSN) on the appropriate use of HIF-PH inhibitors

Renal anaemia is a common and important complication in patients with chronic kidney disease (CKD). The current standard‐of‐care treatment for renal anaemia in CKD patients involves ensuring adequate iron stores and administration of erythropoietin stimulating agents (ESA). Hypoxia inducible factor (HIF) is a key transcription factor primarily involved in the cellular regulation and efficiency of oxygen delivery. Manipulation of the HIF pathway by the use of HIF‐prolyl hydroxylase inhibitors (HIF‐PHI) has emerged as a novel approach for renal anaemia management. Despite it being approved for clinical use in various Asia‐Pacific countries, its novelty mandates the need for nephrologists and clinicians generally in the region to well understand potential benefits and harms when prescribing this class of drug. The Asian Pacific society of nephrology HIF‐PHI Recommendation Committee, formed by a panel of 11 nephrologists from the Asia‐Pacific region who have clinical experience or have been investigators in HIF‐PHI studies, reviewed and deliberated on the clinical and preclinical data concerning HIF‐PHI. This recommendation summarizes the consensus views of the committee regarding the use of HIF‐PHI, taking into account both available data and expert opinion in areas where evidence remains scarce.

The Asian Pacific society of nephrology HIF‐PHI Recommendation Committee summarizes the consensus views of the committee regarding the use of HIF‐PHI, taking into account both available data and expert opinion in areas where evidence remains scarce.

A new insight into the treatment of renal anemia with HIF stabilizer

The long-term clinical experiences with recombinant human erythropoietin (rHuEPO) and its analog derivatives have clearly proven that correction of anemia with erythropoiesis stimulating agent (ESA) not only reduces blood transfusion and improves patients’ QOL but has multiple benefits for the concurrent complications of CKD such as Cardio-Renal–Anemia (CRA) syndrome and/or malnutrition-inflammation-atherosclerosis (MIA) syndrome.

Unlike ESA, the newly available agent, hypoxia-inducible factor (HIF) stabilizer, stimulates endogenous erythropoietin (EPO) by mimicking hypoxia with HIF prolyl hydroxylase domain enzyme (HIF-PHD) inhibition. The phase 2 and 3 clinical studies have shown that HIF stabilizers are as efficacious as ESA in ameliorating renal anemia. Whether the same clinical benefits on CRA and MIA syndrome hold true in patients given HIF stabilizers is a matter for future debate. Given that HIF stabilizers act on the multiple target genes, the use of this novel agent may lead to unwanted adverse events.

Launching HIF stabilizers into the treatment of renal anemia provokes a concern about how this alternative treatment will be taken up in the daily clinical practice. However, guideline-oriented strategies on how to use HIF stabilizer is not available at this limited point due to scant clinical information. Nevertheless, this opinion-based review provides a future insight into the management of renal anemia with HIF stabilizer by reference to the past experiences with ESA. HIF stabilizers can preferably be indicated for CRA syndrome at pre-dialysis stage, ESA resistant anemia at advanced CKD stage, and perhaps for dysregulated iron metabolism akin to MIA syndrome in patients on dialysis.

Disease Mechanisms of Perioperative Organ Injury

Despite substantial advances in anesthesia safety within the past decades, perioperative mortality remains a prevalent problem and can be considered among the top causes of death worldwide. Acute organ failure is a major risk factor of morbidity and mortality in surgical patients and develops primarily as a consequence of a dysregulated inflammatory response and insufficient tissue perfusion. Neurological dysfunction, myocardial ischemia, acute kidney injury, respiratory failure, intestinal dysfunction, and hepatic impairment are among the most serious complications impacting patient outcome and recovery. Pre-, intra-, and postoperative arrangements, such as enhanced recovery after surgery programs, can contribute to lowering the occurrence of organ dysfunction, and mortality rates have improved with the advent of specialized intensive care units and advances in procedures relating to extracorporeal organ support. However, no specific pharmacological therapies have proven effective in the prevention or reversal of perioperative organ injury. Therefore, understanding the underlying mechanisms of organ dysfunction is essential to identify novel treatment strategies to improve perioperative care and outcomes for surgical patients. This review focuses on recent knowledge of pathophysiological and molecular pathways leading to perioperative organ injury. Additionally, we highlight potential therapeutic targets relevant to the network of events that occur in clinical settings with organ failure.

Effectiveness of hypoxia-induced factor prolyl hydroxylase inhibitor for managing anemia in chronic kidney disease: a systematic review and meta-analysis

PURPOSE

To meta-statistically compare the efficiency of hypoxia-induced factor prolyl hydroxylase inhibitor on hemoglobin, ferritin, hepcidin rate, and adverse events.

METHODS

A systematic identification of literature was performed according to PRISMA guidelines on 4 academic databases: MEDLINE, Scopus, EMBASE, and CENTRAL. A meta-analysis evaluating the influence of hypoxia-induced factors was performed for patients undergoing/not undergoing hemodialysis. The analysis evaluated the efficacy of hypoxia-induced factors on hemoglobin, ferritin, hepcidin rate, and the number of adverse events.

RESULTS

Out of 1052 records, 15 articles including 2045 patients (mean age 62.1 ± 5.4 years) were included in this review. The systematic review presents a 1a level of evidence supporting the use of hypoxia-induced factor for mediating anemia in patients with chronic kidney disease. The meta-analysis reveals medium to large beneficial effects of the hypoxia-induced factor on hemoglobin rate for patients receiving (0.72) and not receiving (1.04) hemodialysis. Moreover, the administration of hypoxia-induced factors was reported to reduce ferritin rate and the hepcidin rate, and the number of adverse events in patients with chronic kidney disease.

CONCLUSION

The current meta-analysis recommends the use of hypoxia-induced factor prolyl hydroxylase inhibitor for managing anemia in chronic kidney disease.

Hypoxia-inducible factors not only regulate but also are myeloid-cell treatment targets

Hypoxia describes limited oxygen availability at the cellular level. Myeloid cells are exposed to hypoxia at various bodily sites and even contribute to hypoxia by consuming large amounts of oxygen during respiratory burst. Hypoxia-inducible factors (HIFs) are ubiquitously expressed heterodimeric transcription factors, composed of an oxygen-dependent α and a constitutive β subunit. The stability of HIF-1α and HIF-2α is regulated by oxygen-sensing prolyl-hydroxylases (PHD). HIF-1α and HIF-2α modify the innate immune response and are context dependent. We provide a historic perspective of HIF discovery, discuss the molecular components of the HIF pathway, and how HIF-dependent mechanisms modify myeloid cell functions. HIFs enable myeloid-cell adaptation to hypoxia by up-regulating anaerobic glycolysis. In addition to effects on metabolism, HIFs control chemotaxis, phagocytosis, degranulation, oxidative burst, and apoptosis. HIF-1α enables efficient infection defense by myeloid cells. HIF-2α delays inflammation resolution and decreases antitumor effects by promoting tumor-associated myeloid-cell hibernation. PHDs not only control HIF degradation, but also regulate the crosstalk between innate and adaptive immune cells thereby suppressing autoimmunity. HIF-modifying pharmacologic compounds are entering clinical practice. Current indications include renal anemia and certain cancers. Beneficial and adverse effects on myeloid cells should be considered and could possibly lead to drug repurposing for inflammatory disorders.

Current treatment practices for anemia in patients with chronic kidney disease and future opportunities with hypoxia-inducible factor prolyl hydroxylase inhibitors: a narrative review

PURPOSE

To investigate current treatment practices for anemia in patients with chronic kidney disease (CKD), issues surrounding current treatment practices, and the hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHI) that are currently in clinical trials. Treatment of anemia in patients with CKD has traditionally included iron supplementation and erythropoiesis-stimulating agents (ESAs). However, due to adverse cardiovascular (CV) events and hypo-responsiveness to ESA therapy, new agents are currently in clinical trials to treat anemia in patients with CKD. The HIF-PHIs stimulate erythropoiesis and regulate iron metabolism and are attractive alternatives to iron supplementation and ESAs.

Vadadustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, for treatment of anemia of chronic kidney disease: two randomized Phase 2 trials in Japanese patients

BACKGROUND

Vadadustat is an investigational, oral hypoxia-inducible factor prolyl hydroxylase inhibitor in development in Japan for the treatment of chronic kidney disease (CKD)-induced anemia.

METHODS

Two Phase 2, multicenter, double-blind, placebo-controlled studies randomized Japanese patients with nondialysis-dependent (NDD, n = 51) or dialysis-dependent (DD, n = 60) CKD-induced anemia to once-daily vadadustat (150, 300 or 600 mg) or placebo. A 6-week, fixed-dose primary efficacy period was followed by a 10-week vadadustat dose adjustment/maintenance period. The primary endpoint was the mean change in hemoglobin (Hb) level from pretreatment to Week 6.

RESULTS

Statistically significant (P < 0.01) dose-dependent increases in mean Hb values were observed at Week 6 in all vadadustat groups versus placebo [placebo and vadadustat 150, 300 and 600 mg: -0.47, 0.43, 1.13 and 1.62 (NDD-CKD) and -1.48, -0.28, 0.08 and 0.41 (DD-CKD), respectively]. By Week 16, 91% (NDD-CKD) and 71% (DD-CKD) of vadadustat-treated participants achieved target Hb levels (10.0-12.0 g/dL) and significant dose-dependent changes in iron utilization and mobilization biomarkers were observed with vadadustat. During the primary efficacy period, the incidence of treatment-emergent adverse events (AEs) with placebo and vadadustat 150, 300 and 600 mg was 36, 33, 58 and 54% (NDD-CKD) and 40, 53, 73 and 40% (DD-CKD), respectively. The most common AEs during the primary efficacy period were nausea and hypertension (NDD-CKD) and diarrhea, nasopharyngitis and shunt stenosis (DD-CKD). Of 23 serious AEs in 18 patients, 1 was deemed related (hepatic function abnormal); no deaths were reported.

CONCLUSIONS

The efficacy and safety results from these studies support the development of vadadustat for the treatment of anemia in patients with CKD.

Roxadustat (FG-4592) accelerates pulmonary growth, development, and function in a compensatory lung growth model

Children with hypoplastic lung disease associated with congenital diaphragmatic hernia (CDH) continue to suffer significant morbidity and mortality secondary to progressive pulmonary disease. Current management of CDH is primarily supportive and mortality rates of the most severely affected children have remained unchanged in the last few decades. Previous work in our lab has demonstrated the importance of vascular endothelial growth factor (VEGF)-mediated angiogenesis in accelerating compensatory lung growth. In this study, we evaluated the potential for Roxadustat (FG-4592), a prolyl hydroxylase inhibitor known to increase endogenous VEGF, in accelerating compensatory lung growth. Treatment with Roxadustat increased lung volume, total lung capacity, alveolarization, and exercise tolerance compared to controls following left pneumonectomy. However, this effect was likely modulated not only by increased VEGF, but rather also by decreased pigment epithelium-derived factor (PEDF), an anti-angiogenic factor. Furthermore, this mechanism of action may be specific to Roxadustat. Vadadustat (AKB-6548), a structurally similar prolyl hydroxylase inhibitor, did not demonstrate accelerated compensatory lung growth or decreased PEDF expression following left pneumonectomy. Given that Roxadustat is already in Phase III clinical studies for the treatment of chronic kidney disease-associated anemia with minimal side effects, its use for the treatment of pulmonary hypoplasia could potentially proceed expeditiously.

Hypoxia in chronic kidney disease: towards a paradigm shift?

Chronic kidney disease (CKD) is defined as an alteration of kidney structure and/or function lasting for >3 months [1]. CKD affects 10% of the general adult population and is responsible for large healthcare costs [2]. Since the end of the last century, the role of hypoxia in CKD progression has controversially been discussed. To date, there is evidence of the presence of hypoxia in late-stage renal disease, but we lack time-course evidence, stage correlation and also spatial co-localization with fibrotic lesions to ensure its causative role. The classical view of hypoxia in CKD progression is that it is caused by peritubular capillary alterations, renal anaemia and increased oxygen consumption regardless of the primary injury. In this classical view, hypoxia is assumed to further induce pro-fibrotic and pro-inflammatory responses, as well as oxidative stress, leading to CKD worsening as part of a vicious circle. However, recent investigations tend to question this paradigm, and both the presence of hypoxia and its role in CKD progression are still not clearly demonstrated. Hypoxia-inducible factor (HIF) is the main transcriptional regulator of the hypoxia response. Genetic HIF modulation leads to variable effects on CKD progression in different murine models. In contrast, pharmacological modulation of the HIF pathway [i.e. by HIF hydroxylase inhibitors (HIs)] appears to be generally protective against fibrosis progression experimentally. We here review the existing literature on the role of hypoxia, the HIF pathway and HIF HIs in CKD progression and summarize the evidence that supports or rejects the hypoxia hypothesis, respectively.

Are prolyl-hydroxylase inhibitors potential alternative treatments for anaemia in patients with chronic kidney disease?

Prolyl-hydroxylase (PHD) inhibitors (PHD-I) are the most appealing drugs undergoing clinical development for the treatment of anaemia in patients with chronic kidney disease. PHD inhibition mimics the exposure of the body to hypoxia and activates the hypoxia-inducible factor system. Among many other pathways, this activation promotes the production of endogenous erythropoietin (EPO) and the absorption and mobilization of iron. PHD-I are given orally and, differing from erythropoiesis-stimulating agents (ESAs), they correct and maintain haemoglobin levels by stimulating endogenous EPO production. Their efficacy and safety are supported by several Phases I and II studies with relatively short follow-up. This class of drugs has the potential to have a better safety profile than ESAs and there may be additional advantages for cardiovascular disease (CVD), osteoporosis and metabolism. However, possible adverse outcomes are feared. These span from the worsening or occurrence of new cancer, to eye complications or pulmonary hypertension. The data from the ongoing Phase III studies are awaited to better clarify the long-term safety and possible advantages of PHD-I.

The problem with transferrin saturation as an indicator of iron 'sufficiency' in chronic kidney disease

After a brief review of physiological iron metabolism, we describe diagnostic tests for iron status and iron deficiency anemia in patients without chronic kidney disease (CKD) or inflammation. Thereafter we review the dysregulation of iron metabolism in CKD. Specific emphasis is placed on the role of the 'inflammatory' state that develops with the progression of CKD. It invokes changes in iron metabolism that are the exact opposite of those occurring during pure iron deficiency. As a result, transferrin saturation (TSAT) becomes a poorer index of iron availability to the bone marrow and serum ferritin no longer represents iron that can be used during erythropoiesis. We argue that serum iron may provide more information to guide iron therapy than TSAT. In other words, the emphasis on TSAT is misplaced. With the development of a number of hypoxia-inducible factor prolyl hydroxylase inhibitors, which restore iron metabolism toward the 'physiologic state', the iron indices indicating sufficient iron availability to avoid functional iron deficiency during therapy of CKD-associated anemia are likely to change. We summarize these changes in the section 'A peek into things to come!', citing the available data.

Anemia management in dialysis patients: a PIVOT and a new path?

PURPOSE OF REVIEW

We will examine the current and future options in management of anemia in dialysis patients focusing on recent trials in iron supplementation and alternatives to erythropoietin-stimulating agents (ESAs).

RECENT FINDINGS

We review the literature on Erythropoietin (EPO)-stimulating agents, focusing on the risk benefits of various options available. We review the recent practice changing trial in iron supplementation in dialysis patients with chronic kidney disease and movements in the research on alternatives to EPO-stimulating agents primarily hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs).

SUMMARY

ESAs constitute the mainstay of treatment of anemia in dialysis and evidence does not support the preference of any one type over the other. But concerns exist about the cardiovascular safety of supra-physiological ESA levels. Iron supplementation has been shown to be a well tolerated method to decrease ESA doses while maintaining hemoglobin levels and recent evidence should result in a revisiting of the guidelines for iron supplementation. HIF-PHIs are potentially safe alternatives to ESAs that correct and maintain hemoglobin while maintaining physiological levels of erythropoietin. Ongoing phase III trials for these drugs will likely answer questions of long-term safety regarding these drugs.