Hypoxia-Inducible Factor-Prolyl Hydroxyl Domain Inhibitors: From Theoretical Superiority to Clinical Noninferiority Compared with Current ESAs?

Hypoxia-inducible factor prolyl hydroxylase inhibitors for anaemia in chronic kidney disease: a clinical practice document by the European Renal Best Practice board of the European Renal Association

Anaemia is a common complication of chronic kidney disease (CKD) and is associated with poor long-term outcomes and quality of life. The use of supplemental iron, erythropoiesis-stimulating agents (ESAs) and blood transfusions has been the mainstay for treatment of anaemia in CKD for more than 3 decades. Despite available treatments, CKD patients with anaemia are undertreated and moderate-severe anaemia remains prevalent in the CKD population. Anaemia has consistently been associated with greater mortality, hospitalization, cardiovascular events and CKD progression in CKD patients, and the risk increases with anaemia severity. Hypoxia-inducible factor (HIF) prolyl hydroxylase (PH) inhibitors have a novel mechanism of action by mimicking the body's response to hypoxia and have emerged as an alternative to ESAs for treatment of anaemia in CKD. Their efficacy in correcting and maintaining haemoglobin has been demonstrated in >30 phase 3 clinical trials. Additionally, HIF activation results in various pleiotropic effects beyond erythropoiesis, with cholesterol reduction and improved iron homeostasis and potential anti-inflammatory effects. The long-term safety of these agents, particularly with respect to cardiovascular and thromboembolic events, and their possible effect on tumour growth needs to be fully elucidated. This article presents in detail the effects of HIF-PH inhibitors, describes their mechanisms of action and pharmacologic properties and discusses their place in the treatment of anaemia in CKD according to the available evidence.

Renoprotective Effects of Daprodustat in Patients with Chronic Kidney Disease and Renal Anemia

Many large-scale studies revealed that exogenous erythropoietin, erythropoiesis-stimulating agents, have no renoprotective effects. We reported the renoprotective effects of endogenous erythropoietin production on renal function in ischemic reperfusion injury (IRI) of the kidney using the prolyl hydroxylase domain (PHD) inhibitor, Roxadustat. The purpose of this study was to investigate the effects of daprodustat on the progression of chronic renal failure. We retrospectively investigated the effects of daprodustat on the progression of chronic renal failure and renal anemia in patients with stages 3a-5 chronic kidney diseases (estimated glomerular filtration rate, eGFR < 60 mL/min/1.73 m2). The results show that daprodustat largely slowed the reduction in eGFR. The recovery of renal function was observed in some patients. Daprodustat is useful not only for renal anemia but also for the preservation of renal function. The renoprotective effect of daprodustat was small in patients with serum creatinine larger than 3-4 mg/dL because of low residual renal function. The appearance of renal anemia would be a sign of the time to start using daprodustat.

The Comparison between Vadadustat and Daprodustat Regarding Dose, Cost, and Safety of Treatment for Renal Anemia in Non-dialysis Patients with Chronic Kidney Diseases

Objective We retrospectively compared the dose, cost, and safety of vadadustat and daprodustat for the treatment of renal anemia in patients with chronic kidney diseases who were not undergoing dialysis. Methods The primary outcome of this study was the change in dose and cost from the initiation of vadadustat and daprodustat treatment. The secondary outcome was the drug safety. Patients We treated 30 patients each with the hypoxia-inducible factor prolyl-hydroxylase inhibitors (HIF-PHIs) daprodustat and vadadustat. The hemoglobin (Hb) concentration was targeted at 11-13 g/dL, and transferrin saturation was maintained at ≥20%, as per the 2018 Japanese guidelines for the diagnosis and treatment of chronic kidney disease. Results Hb levels increased from 10.7 to 11.5 g/dL after the first month of daprodustat administration, whereas those for vadadustat patients remained relatively stable, going from 10.7 to 10.6 g/dL. After six months, the Hb level reached 12.1 g/dL and 11.3 g/dL for daprodustat and vadadustat, respectively. The dosage of vadadustat was significantly increased by 46% and 70% after 3 and 12 months, respectively, compared with the initial doses, whereas that of daprodustat did not change substantially. The average cost of vadadustat also increased in the first 3 months and remained over 500 yen/day after 3 months, while that of daprodustat showed little change from the initial cost of 360 yen/day. Conclusion These results suggest that heterogeneity exists in the drug potency and dosage required for treatment between daprodustat and vadadustat. Serious adverse events [death, cardiovascular disease, end stage renal disease (ESRD), and malignancy] occurred in more than 20% of participants with both HIF-PHIs. Further studies are required to confirm the safety of HIF-PHIs.

Targeting inflammation in perivascular cells and neuroimmune interactions for treating kidney disease

Inflammation plays a crucial role in the pathophysiology of various kidney diseases. Kidney perivascular cells (pericytes/fibroblasts) are responsible for producing proinflammatory molecules, promoting immune cell infiltration, and enhancing inflammation. Vascular adhesion protein-1, expressed in kidney perivascular cells, is an ectoenzyme that catalyzes the oxidative deamination of primary amines with the production of hydrogen peroxide in the extracellular space. Our study demonstrated that blocking this enzyme suppressed hydrogen peroxide production and neutrophil infiltration, thereby reducing renal ischemia-reperfusion injury. Sphingosine 1-phosphate (S1P) signaling was also observed to play an essential role in the regulation of perivascular inflammation. S1P, which is produced in kidney perivascular cells, is transported into the extracellular space via spinster homolog 2, and then binds to S1P receptor-1 expressed in perivascular cells. Upon injury, inflammatory signaling in perivascular cells is enhanced by this pathway, thereby promoting immune cell infiltration and subsequent fibrosis. Furthermore, inhibition of S1P transport by spinster homolog 2 reduces kidney fibrosis. Hypoxia-inducible factor-prolyl hydroxylase inhibitors can restore the capacity for erythropoietin production in kidney perivascular cells. Animal data suggested that these drugs could also alleviate kidney and lipid inflammation although the precise mechanism is still unknown. Neuroimmune interactions have been attracting significant attention due to their potential to benefit patients with inflammatory diseases. Vagus nerve stimulation is one of the most promising strategies for harnessing neuroimmune interactions and attenuating inflammation associated with various diseases, including kidney disease. Using cutting-edge tools, the vagal afferents-C1 neurons-sympathetic nervous system-splenic nerve-spleen-kidney axis responsible for kidney protection induced by vagus nerve stimulation was identified in our study. Further research is required to decipher other crucial systems that control kidney inflammation and to determine whether these novel strategies can be applied to patients with kidney disease.

Evaluating the safety and efficacy of vadadustat for the treatment of anemia associated with chronic kidney disease

INTRODUCTION

The breakthrough in erythropoietin-stimulating agents in the 1990s improved the prognosis and treatment of complications in chronic kidney disease patients and renal anemia. Discovery of the novel molecular mechanisms for hypoxia-inducible factor (HIF) transcription factor under hypoxic conditions has led to the development of oral drugs, HIF-Prolyl Hydroxylase inhibitors (HIF-PHIs), that constantly activate erythropoietin by inhibiting prolyl hydroxylase. HIF-PHIs have gained rapid approval in Asian countries, including Japan, with six distinct types entering clinical application.

AREAS COVERED

This article provides a comprehensive review of the latest literature, with a particular focus on the effectiveness and safety of vadadustat.

EXPERT OPINION

A phase 3, randomized, open-label, clinical trial (PRO2TECT) demonstrated that vadadustat had the prespecified non-inferiority for hematologic efficacy as compared with darbepoetin alfa in non-dialysis-dependent patients not previously treated with ESA. However, vadadustat did not show non-inferiority in major adverse cardiovascular events in the non-US/non-Europe patients. It may partly because of imbalances of the baseline eGFR level in those countries. In dialysis-dependent patients, a phase 3 clinical trial (INNO2VATE) showed vadadustat was non-inferior to darbepoetin alfa in cardiovascular safety and maintenance of hemoglobin levels. Adverse events including cancer, retinopathy, thrombosis, and vascular calcification should be evaluated in future clinical studies.

A nomogram for predicting the risk of treatment failure of roxadustat in peritoneal dialysis with renal anemia

The determinants of roxadustat treatment failure in renal anemia remain elusive. This study sought to develop a nomogram for predicting the risk of treatment failure of roxadustat in peritoneal dialysis (PD) with renal anemia. A retrospective cohort analysis from January 1, 2019, to January 31, 2023, included 204 PD patients with renal anemia, stratified by attainment group (Hb ≥ 110 g/L, n = 103) or non-attainment (Hb < 110 g/L, n = 101) within 1 year treatment. Univariate and multivariate Cox proportional hazards regressions were employed to ascertain predictive factors and construct the nomogram. Nomogram efficacy was evaluated via C-index, time-dependent ROC, calibration plots, and decision curve analysis, with internal validation via tenfold cross-validation and 1000 bootstrap resampling iterations. The study identified PD duration, serum transferrin, cardiovascular comorbidities, and stains as significant predictors. The nomogram demonstrated moderate discrimination at 6 months (AUC: 0.717) and enhanced predictive accuracy at 12 months (AUC: 0.741). The predicted and actual risk probabilities were concordant, with clinical net benefits observed at six-month (8 to 53%) and twelve-month (27 to 84%) risk thresholds. This nomogram is a valuable tool for effectively predicting non-attainment risk and facilitating personalized management of renal anemia in PD patients treated with roxadustat.

Tubular Endogenous Erythropoietin Protects Renal Function against Ischemic Reperfusion Injury

Many large-scale studies show that exogenous erythropoietin, erythropoiesis-stimulating agents, lack any renoprotective effects. We investigated the effects of endogenous erythropoietin on renal function in kidney ischemic reperfusion injury (IRI) using the prolyl hydroxylase domain (PHD) inhibitor, Roxadustat (ROX). Four h of hypoxia (7% O2) and 4 h treatment by ROX prior to IRI did not improve renal function. In contrast, 24-72 h pretreatment by ROX significantly improved the decline of renal function caused by IRI. Hypoxia and 4 h ROX increased interstitial cells-derived Epo production by 75- and 6-fold, respectively, before IRI, and worked similarly to exogenous Epo. ROX treatment for 24-72 h increased Epo production during IRI by 9-fold. Immunohistochemistry revealed that 24 h ROX treatment induced Epo production in proximal and distal tubules and worked similarly to endogenous Epo. Our data show that tubular endogenous Epo production induced by 24-72 h ROX treatment results in renoprotection but peritubular exogenous Epo production by interstitial cells induced by hypoxia and 4 h ROX treatment did not. Stimulation of tubular, but not peritubular, Epo production may link to renoprotection.

Budget impact analysis on the Italian healthcare system of roxadustat for the treatment of anemia due to chronic kidney disease

Objective: The aim of this study was to evaluate the economic consequences of the introduction of roxadustat on the market as treatment for chronic kidney disease (CKD)-related anaemia in Italy. Method: A budget impact model was developed to assess the economic impact of the introduction of roxadustat for the management of patient with CKD-related anaemia. The analysis was conducted considering National Health Service (NHS) perspective and three years’ time horizon. Eligible population for the treatment with roxadustat was estimated through published literature and clinicians’ support. Direct healthcare costs included drug acquisition (list prices for base case) and administration costs, monitoring costs, cost per blood transfusion, costs related to the management of adverse events and dialysis costs. Results: The model estimated a three years expenditure associated with the management of patients with CKD-related incident anaemia in Italy of about € 260 and € 44.6 million for non-dialysis dependent (NDD) and dialysis-dependent (DD) patients respectively. The introduction of roxadustat on the market could generate a reduction in the expenditure related to the iron supplementation both for NDD and for DD patients (−€ 397,305 and −€ 50,135 over three years of the analysis, respectively) and a reduction in the pharmaceutical expenditure for NDD patients (−€ 2.3 million, −€ 7.5 million and −€ 13 million at first, second and third year of the analysis). Overall, the introduction of roxadustat could generate a saving for NHS approximately equal to € 2.3, € 7.5 and € 13 million at first, second and third year of the analysis. Conclusion: The introduction of roxadustat could generate a reduction in the expenditure for the management of patients with CKD anaemia. A scenario analysis which used tender prices for ESAs and hypothesis of confidential discount for roxadustat showed that the saving for NHS will be kept if roxadustat’s discount is greater than 60.3%.

Effect of roxadustat on iron metabolism in patients with peritoneal dialysis: a real-world 24-week study

BACKGROUND

Roxadustat is an oral hypoxia inducing factor-prolyl hydroxylase inhibitor (HIF-PHI) that regulates iron metabolism in patients with chronic kidney disease (CKD) primarily by reducing hepcidin levels and mobilizing internal iron stores. More data are needed to demonstrate the efficacy of roxadustat in regulating iron metabolism in patients with peritoneal dialysis (PD) compared with erythropoiesis stimulating agents (ESAs).

METHODS

This prospective cohort study enrolled PD patients with a mean hemoglobin level of 60-100 g/L. All subjects were randomized into two groups at a ratio of 2:1 the roxadustat group (106 cases), and the ESA group (53 cases). The primary endpoint was the change in the iron biomarker levels and the proportion of patients with absolute iron deficiency and functional iron deficiency.

RESULTS

Compared with ESAs, roxadustat significantly decreased hepcidin level (difference, - 20.09 ng/mL; 95% CI, - 30.26 to - 9.92), attenuated the increase in serum soluble transferrin receptor (sTFR) level (difference, - 7.87 nmol/L; 95% CI, - 12.11 to - 3.64), and reduced the proportion of patients with functional iron deficiency (roxadustat, 11.43%; ESA, 33.33%). There was no significant difference in safety of the two groups over the duration of the study.

CONCLUSIONS

Compared with ESA group, roxadustat group showed significant differences in all iron biomarker levels except serum ferritin (sFt) and transferrin saturation (TSAT). These results suggest that roxadustat was superior to ESAs as a therapy for iron metabolism in PD patients.

TRIAL REGISTRATION

This study completed Chinese Clinical Trial Registration on March 4, 2022 (registration number: ChiCTR2200057231).

Role of perivascular cells in kidney homeostasis, inflammation, repair and fibrosis

Perivascular niches in the kidney comprise heterogeneous cell populations, including pericytes and fibroblasts, with distinct functions. These perivascular cells have crucial roles in preserving kidney homeostasis as they maintain microvascular networks by stabilizing the vasculature and regulating capillary constriction. A subset of kidney perivascular cells can also produce and secrete erythropoietin; this ability can be enhanced with hypoxia-inducible factor-prolyl hydroxylase inhibitors, which are used to treat anaemia in chronic kidney disease. In the pathophysiological state, kidney perivascular cells contribute to the progression of kidney fibrosis, partly via transdifferentiation into myofibroblasts. Moreover, perivascular cells are now recognized as major innate immune sentinels in the kidney that produce pro-inflammatory cytokines and chemokines following injury. These mediators promote immune cell infiltration, leading to persistent inflammation and progression of kidney fibrosis. The crosstalk between perivascular cells and tubular epithelial, immune and endothelial cells is therefore a key process in physiological and pathophysiological states. Here, we examine the multiple roles of kidney perivascular cells in health and disease, focusing on the latest advances in this field of research.

The anaemia treatment journey of CKD patients: from epoetins to hypoxia-inducible factor-prolyl hydroxylase inhibitors

The discovery and development of erythropoiesis-stimulating agents was a journey lasting more than a century, leading to the cloning and approval of recombinant human erythropoietin (rHuEpo). This was an impressive clinical advance, providing the possibility of correcting the symptoms associated with anaemia in chronic kidney disease. Associated iron use was needed to produce new haemoglobin-containing blood red cells. Partial anaemia correction became the standard of care since trials aiming for near-normal haemoglobin levels showed a higher risk of adverse cardiovascular events. Hoping to reduce the cardiovascular risks, a new category of drugs was developed and tested. Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are small molecules than can be formulated into orally active pills. They simulate reduced tissue oxygen pressure, thus stimulating the production of endogenous erythropoietin (Epo) by the kidneys and liver. Clinical trials with these compounds demonstrated that HIF-PHIs are at least as effective as rHuEpo in treating or correcting anaemia in non-dialysis and dialysis patients. Trials with HIF-PHIs did not demonstrate superiority in safety outcomes and in some trials, outcomes were worse. There was also a focus on oral delivery, a possible beneficial iron-sparing effect and the ability to overcome Epo resistance in inflamed patients. A negative effect is possible iron depletion, which may explain adverse outcomes.

Mitochondrial iron regulation as an emerging target in ischemia/reperfusion injury during kidney transplantation

The injury caused by ischemia and subsequent reperfusion (I/R) is inevitable during kidney transplantation and its current management remains unsatisfactory. Iron is considered to play a remarkable pathologic role in the initiation or progression of tissue damage induced by I/R, whereas the effects of iron-related therapy remain controversial owing to the complicated nature of iron's involvement in multiple biological processes. A significant portion of the cellular iron is located in the mitochondria, which exerts a central role in the development and progression of I/R injury. Recent studies of iron regulation associated with mitochondrial function represents a unique opportunity to improve our knowledge on the pathophysiology of I/R injury. However, the molecular mechanisms linking mitochondria to the iron homeostasis remain unclear. In this review, we provide a comprehensive analysis of the alterations to iron metabolism in I/R injury during kidney transplantation, analyze the current understanding of mitochondrial regulation of iron homeostasis and discussed its potential application in I/R injury. The elucidation of regulatory mechanisms regulating mitochondrial iron homeostasis will offer valuable insights into potential therapeutic targets for alleviating I/R injury with the ultimate aim of improving kidney graft outcomes, with potential implications that could also extend to acute kidney injury or other I/R injuries.