Targeting Hypoxia-Inducible Factors for the Treatment of Anemia in Chronic Kidney Disease Patients

A Phase 3 Study of Enarodustat in Anemic Patients with CKD not Requiring Dialysis: The SYMPHONY ND Study

Introduction

Enarodustat (JTZ-951) is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that might be a new therapeutic approach for managing anemia in patients with chronic kidney disease (CKD). We evaluated the efficacy (noninferiority to darbepoetin alfa [DA]) and safety of enarodustat in Japanese anemic patients with CKD not requiring dialysis.

Methods

Erythropoiesis-stimulating agent (ESA)-naïve patients and ESA-treated patients were randomized at a 1:1 ratio to receive enarodustat orally once daily or DA subcutaneously every 2 or 4 weeks for 24 weeks, respectively. Subjects in each arm had dose adjustments every 4 weeks to maintain their hemoglobin (Hb) level within the target range (10 to 12 g/dl). The primary endpoint was the difference in the mean Hb level between arms during the evaluation period defined as weeks 20 to 24 (noninferiority margin: -0.75 g/dl).

Results

The mean Hb level during the evaluation period in the enarodustat arm was 10.96 g/dl (95% confidence interval [CI]: 10.84 to 11.07 g/dl) with a difference of 0.09 g/dl (95% CI: -0.07 to 0.26 g/dl) between arms, establishing its noninferiority to DA. Nearly 90% of subjects in both arms maintained a mean Hb level within the target range. Compared with DA, enarodustat was associated with decreased hepcidin and ferritin, and increased total iron-binding capacity. There were no apparent differences in the incidence of adverse events between arms (65.4% [enarodustat], 82.6% [DA]).

Conclusions

The efficacy of enarodustat was comparable to DA in anemic patients with CKD not requiring dialysis. No new safety concerns were identified compared with DA.

Effect of the Phosphate Binders Sevelamer Carbonate and Calcium Acetate on the Pharmacokinetics of Roxadustat After Concomitant or Time-Separated Administration in Healthy Individuals

PURPOSE

Roxadustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, treats anemia in chronic kidney disease. Hyperphosphatemia, a common complication in chronic kidney disease, is treated with phosphate binders (PBs). This study in healthy individuals investigated the effect of 2 PBs, sevelamer carbonate and calcium acetate, on the pharmacokinetic properties of a single oral dose of roxadustat administered concomitantly or with a time lag.

METHODS

This 2-part, Phase I study was conducted with an open-label, randomized, 3-way (part 1) or 5-way (part 2) crossover design, with 5-day treatment periods. On day 1 of each period, participants received 200 mg roxadustat administered alone or (1) concomitantly with sevelamer carbonate (2400 mg) or calcium acetate (1900 mg) (part 1) or (2) 1 hour before or 1, 2, or 3 hours after sevelamer carbonate (part 2A) or calcium acetate (part 2B); 5 additional PB doses were administered during 2 days. In both parts, PBs were administered with meals. Primary pharmacokinetic variables were AUC_0-∞ and C_max. FINDINGS: Twenty-four individuals were randomized in part 1; 60 individuals were randomized in part 2 (part 2A, n = 30; part 2B, n = 30). All participants completed the study in part 1; 28 and 27 individuals completed the study in part 2A and part 2B, respectively. Compared with roxadustat alone, concomitant sevelamer carbonate and calcium acetate administration reduced roxadustat's AUC_0-∞ by 67% (90% CI, 63.5%-69.3%) and 46% (90% CI, 41.7%-50.9%), respectively, and reduced roxadustat's C_max by 66% (90% CI, 61.6%-69.4%) and 52% (90% CI, 46.2%-57.2%), respectively. This effect was attenuated when roxadustat and PB administration occurred with a time lag. Roxadustat's AUC_0-∞ was reduced by 41% and 22% to 25%, respectively, when roxadustat was administered 1 hour before or 1 to 3 hours after sevelamer carbonate and by 31% and 14% to 18%, respectively, when administered 1 hour before or 1 to 3 hours after calcium acetate. Roxadustat's C_max was reduced by 26% and 12%, respectively, when roxadustat was administered 1 hour before and 1 hour after sevelamer carbonate; it was reduced by 19% when administered 1 hour before calcium acetate and was not affected when administered 1 hour after. Roxadustat was well tolerated.

IMPLICATIONS

Concomitant administration of roxadustat with sevelamer carbonate or calcium acetate reduced exposure to roxadustat in healthy individuals. This effect was attenuated when roxadustat was administered ≥1 hour before or after either PB. Results from this study helped inform dosing and administration guidelines aimed at reducing interactions between roxadustat and these PBs. (Clin Ther. 2021;XX:XXX-XXX) © 2021 Elsevier HS Journals, Inc.

Phase 3 Study of Roxadustat to Treat Anemia in Non-Dialysis-Dependant CKD

Introduction

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that has demonstrated safety and efficacy versus placebo in phase III trials in patients with anemia of chronic kidney disease (CKD) who were not on dialysis (NDD).

Methods

This was a phase III, active-controlled, multicenter, partially randomized, open-label study in Japanese patients with NDD CKD. Patients who had used recombinant human erythropoietin or darbepoetin alfa (DA) before conversion were randomized to roxadustat or DA (comparative arms). Patients who had used epoetin beta pegol before conversion were allocated to roxadustat (reference arm). The primary endpoint was change in average hemoglobin (Hb) level from baseline during the evaluation period (Weeks 18–24). Longer term efficacy and safety were evaluated in roxadustat-treated patients over 52 weeks.

Results

In this study, 334 patients were randomized/allocated to receive treatment (n = 132, roxadustat [comparative]; n = 131, DA [comparative]; n = 71, roxadustat [reference]). The estimated difference between the roxadustat (comparative) and DA (comparative) groups in the least squares mean of change of average Hb levels of Weeks 18 to 24 from baseline was –0.07 g/dl, with the lower limit of 95% confidence interval of –0.23 g/dl, thereby confirming the noninferiority of roxadustat to DA. Common treatment-emergent adverse events (≥3% of patients in any treatment group) observed during the 24-week treatment period included nasopharyngitis, CKD, hyperkalemia, and hypertension.

Conclusion

Roxadustat maintained Hb within 10 to 12 g/dl in NDD CKD patients and was noninferior to DA. The safety profiles observed in this study are consistent with previous studies performed in this patient population.

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.

Roxadustat for the treatment of anemia in chronic kidney disease patients not on dialysis: a Phase 3, randomized, double-blind, placebo-controlled study (ALPS)

BACKGROUND

Roxadustat is an orally active hypoxia-inducible factor prolyl hydroxylase inhibitor for the treatment of chronic kidney disease (CKD) anemia.

METHODS

This Phase 3, multicenter, randomized, double-blind, placebo-controlled study examined patients with Stages 3-5 CKD, not on dialysis (NCT01887600). Patients were randomized (2:1) to oral roxadustat or placebo three times weekly for 52-104 weeks. This study examined two primary efficacy endpoints: European Union (European Medicines Agency)-hemoglobin (Hb) response, defined as Hb ≥11.0 g/dL that increased from baseline (BL) by ≥1.0 g/dL in patients with Hb >8.0 g/dL or ≥2.0 g/dL in patients with BL Hb ≤8.0 g/dL, without rescue therapy, during the first 24 weeks of treatment; US Food and Drug Administration-change in Hb from BL to the average Hb level during Weeks 28-52, regardless of rescue therapy. Secondary efficacy endpoints and safety were examined.

RESULTS

A total of 594 patients were analyzed (roxadustat: 391; placebo: 203). Superiority of roxadustat versus placebo was demonstrated for both primary efficacy endpoints: Hb response [odds ratio = 34.74, 95% confidence interval (CI) 20.48-58.93] and change in Hb from BL [roxadustat - placebo: +1.692 (95% CI 1.52-1.86); both P < 0.001]. Superiority of roxadustat was demonstrated for low-density lipoprotein cholesterol change from BL, and time to first use of rescue medication (both P < 0.001). The incidences of treatment-emergent adverse events were comparable between groups (roxadustat: 87.7%, placebo: 86.7%).

CONCLUSIONS

Roxadustat demonstrated superior efficacy versus placebo in terms of both Hb response rate and change in Hb from BL. The safety profiles of roxadustat and placebo were comparable.

Whether Prolyl Hydroxylase Blocker-Roxadustat-In the Treatment of Anemia in Patients with Chronic Kidney Disease Is the Future?

In patients with chronic kidney disease (CKD), anemia develops gradually, which is primarily due to an inadequate synthesis of erythropoietin by the kidneys, as well as to iron disorders in the body, blood loss, shortened erythrocyte survival and inflammation. The currently accepted treatment employs iron, vitamin B12, folic acid supplementation and the use of erythropoiesis stimulants, which are administered only parenterally. Research is currently underway on the new erythropoiesis drugs that can be orally administered, i.e., hypoxia-inducible factor-propyl hydroxylase inhibitor (HIF-PHI) inhibitors which temporarily block propyl hydroxylase [PHD] catalysis and promote a transient increase in the expression of genes regulated by HIF, including kidney and liver erythropoietin [EPO]. Roxadustat is the first oral drug in this class and a potent HIF-PHD inhibitor, exerted to treat anemia in patients with CKD. In phase 1, 2 and 3 studies with CKD-affected patients, roxadustat was more effective to stimulate erythropoiesis for anemia correction than previously used drugs. Roxadustat can be orally given, unlike other erythropoiesis drugs with parenteral administration only, which grants roxadustat a considerable advantage. Our paper presents the results of studies with roxadustat applied for the treatment of anemia in CKD patients with or without dialysis. We are currently not yet able to know the exact role of roxadustat in the treatment of anemia in patients with CKD, but time will tell. It is possible that roxadustat has benefits an iron metabolism and cardiovascular risk.

The efficacy and safety of roxadustat treatment for anemia in patients with kidney disease: a meta-analysis and systematic review

BACKGROUND

Anemia is a common complication for patients with kidney disease. Roxadustat is an oral hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor (PHI), which is a newly approved oral drug for anemia. We performed this study to build evidence regarding efficacy and safety of roxadustat in kidney disease patients with or without dialysis.

METHODS

We searched the databases of PubMed, Embase, Cochrane library and clinicaltrials.gov from the inception to July 20, 2020. The randomized controlled trials (RCTs) which compared roxadustat with placebo or other therapies in the treatment of anemia in kidney disease patients were included. Data were extracted from eligible studies and pooled in a meta-analysis model using RevMan5.3 and stata13.0 software.

RESULTS

Eight RCTs with 1010 patients were included in our analysis. We found that roxadustat significantly increased hemoglobin (Hb) level (1.10 g/dL, 95% CI [0.52 g/dL, 1.67 g/dL], p = 0.0002), total iron-binding capacity (TIBC) (58.71 µg/dL, 95% CI [44.10 µg/dL, 73.32 µg/dL], p < 0.00001), iron level (9.28 µg/dL, 95% CI [0.11 µg/dL, 18.45 µg/dL], p = 0.05) compared with control group in kidney disease patients. In addition, our result showed that a significant reduction in hepcidin level (- 31.96 ng/mL, 95% CI [- 35.05 ng/mL, - 28.87 ng/mL], p < 0.00001), ferritin (- 44.82 ng/mL, 95% CI [- 64.42 ng/mL, - 25.23 ng/mL], p < 0.00001) was associated with roxadustat. No difference was found between roxadustat and control group in terms of oral iron supplementation, adverse events (AEs), serious adverse events (SAEs), infection, myocardial infraction, stroke, heart failure and death.

CONCLUSIONS

Roxadustat has higher mean Hb level than placebo or EPO. Due to the short follow-up period and the lack of critical data, more RCTs are needed to prove long-term safety and effectiveness of roxadustat in the future.

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.

Iron and Chronic Kidney Disease: Still a Challenge

Anemia is a clinical feature of chronic kidney disease (CKD). Most common causes are iron and erythropoietin deficiency. The last two decades have yielded significant advances in understanding iron balance's physiology, including iron trafficking and the crosstalk between iron, oxygen, and erythropoiesis. This knowledge sheds new light on the regulation and disturbance of iron homeostasis in CKD and holds the promise for developing new diagnostic and therapeutic tools to improve the management of iron disorders. Hepcidin-ferroportin axis has a central role in regulating body iron balance and coordinating communication between tissues and cells that acquire, store, and utilize iron. Recent research has revealed a bidirectional relationship between fibroblast growth factor 23 (FGF23) and iron status, anemia, and inflammation, as well as the role of erythroferrone (ERFE) in iron homeostasis. However, ERFE concentrations and actions are not well-characterized in CKD patients. Studies on ERFE in CKD are limited with slightly conflicting results. Despite general interest in iron metabolism in kidney diseases, studies on the less prevalent renal replacement therapy mode, such as peritoneal dialysis or hemodiafiltration, are scarce. Slightly more was published on hemodialysis. There are several novel options on the horizon; however, clinical data are limited. One should be aware of the potential risks and benefits of the novel, sophisticated therapies. An inhibition of hepcidin on the different pathways might be also a viable adjunctive therapeutic option in other clinical situations.

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.

Drug-drug interaction of atazanavir on UGT1A1-mediated glucuronidation of molidustat in human

Molidustat is an oral inhibitor of hypoxia‐inducible factor (HIF) prolyl‐hydroxylase enhancing the erythropoietin (EPO) response to HIF; it is in clinical development for the treatment of anaemia related to chronic kidney disease. The predominant role of glucuronidation for molidustat clearance (formation of N‐glucuronide metabolite M1) and subsequent renal excretion was confirmed in a human mass balance study, with about 85% of the drug being excreted as M1 in urine. The inhibitory effects of 176 drugs and xenobiotics from various compound classes on the UGT‐mediated glucuronidation of molidustat in human liver microsomes (HLMs) were investigated. Based on preclinical findings, glucuronidation of molidustat was predominantly mediated by the 5'‐diphospho‐glucuronosyltransferase (UGT) isoform UGT1A1. Therefore, atazanavir, which is a potent inhibitor of UGT1A1, was chosen for the evaluation of pharmacokinetics and EPO release following a single oral dose of 25 mg molidustat. Molidustat exposure increased about twofold upon coadministration with atazanavir when considering area under plasma concentration‐time curve from zero to infinity (AUC) and maximum plasma concentration (C_max). Baseline‐corrected increase of EPO was 14% and 34% for C_max and AUC (calculated over 24 hours), respectively. Coadministration of molidustat and atazanavir was well tolerated.

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.

Effect of Kidney Function and Dialysis on the Pharmacokinetics and Pharmacodynamics of Roxadustat, an Oral Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor

Background and Objectives

Roxadustat is an orally active hypoxia-inducible factor prolyl hydroxylase inhibitor for anemia in chronic kidney disease. The pharmacokinetics, metabolic profile, and pharmacodynamics of roxadustat were investigated in subjects with different degrees of kidney function.

Methods

This phase 1 open-label study enrolled subjects with normal and severely impaired kidney function, and end-stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD) or hemodialysis/hemodiafiltration (HD/HDF). All subjects received a single 100-mg dose of oral roxadustat. Within a single-sequence, two-treatment period design (P1/P2), subjects with ESRD on HD/HDF received roxadustat 2 h after (P1) and 2 h before (P2) a dialysis session. Area under the plasma concentration–time curve (AUC) from administration to infinity (AUC_inf), maximum concentration (C_max), and terminal elimination half-life (t_1/2) were assessed for roxadustat; AUC and C_max were assessed for erythropoietin.

Results

Thirty-four subjects were enrolled and received roxadustat (normal kidney function, n = 12; severely impaired kidney function, n = 9; ESRD on CAPD/APD, n = 1; ESRD on HD/HDF, n = 12). The geometric least-square mean ratio of AUC_inf was 223% and 195% in subjects with severely impaired kidney function and ESRD on HD/HDF, respectively, relative to subjects with normal kidney function; C_max and t_1/2 were comparable. The pharmacokinetic profile of roxadustat was not affected by HD/HDF. AUC_inf and t_1/2 for the metabolites of roxadustat increased in subjects with kidney impairment. The AUC and C_max of erythropoietin increased in subjects with severely impaired kidney function or ESRD on HD/HDF. Roxadustat was well tolerated.

Conclusions

Kidney function impairment increased the AUC of roxadustat and its metabolites. The C_max and t_1/2 of roxadustat were comparable among groups. Roxadustat and its metabolites were not cleared by HD/HDF.

Clinical Trials Registration Number: NCT02965040.

Electronic supplementary material

The online version of this article (10.1007/s13318-020-00658-w) contains supplementary material, which is available to authorized users.

Jian-Pi-Yi-Shen Regulates EPO and Iron Recycling Protein Expressions in Anemic Rats with Chronic Kidney Disease: Accumulation of Hypoxia Inducible Factor-2α via ERK Signaling

Jian-Pi-Yi-Shen (JPYS), the traditional Chinese medicine (TCM) decoction, has been commonly used to treat chronic kidney disease (CKD) and its complications such as anemia. JPYS has been previously found to induce erythropoietin (EPO) production in HEK293T cells and CKD rats. However, the mechanism of JPYS in treating anemia of CKD rats has remained largely unknown. Here, we further extend our effort to investigate the translational control of hypoxia inducible factor- (HIF-) α protein via ERK signaling and the effect on iron recycling-related protein expression by JPYS, thus revealing the mechanism of JPYS in correcting anemia in CKD. Experimental CKD rats with anemia were induced by 5/6 nephrectomy. Rats were administrated orally with high dose (6.0 g/kg/d) and low dose (1.5 g/kg/d) of JPYS for 90 days. Serum hepcidin level was determined to evaluate iron homeostasis. The protein expressions of HIF-2α, erythropoietin (EPO), ferritin, and ferroportin (FPN) and the phosphorylation level of extracellular signal-regulated kinase 1/2 (ERK1/2) were detected by Western blot. The results showed that JPYS treatment significantly ameliorated kidney function by reducing increased levels of blood urea nitrogen (BUN), serum creatinine (Scr), and urine protein (UPRO). Periodic acid-Schiff (PAS) and Masson staining observation showed that the renal pathological damage was restored in JPYS-treated CKD rats. In parallel, JPYS markedly improved CKD anemia through upregulation of red blood cell (RBC), hemoglobin (HGB), and hematocrit (HCT). JPYS stimulated EPO and HIF-2α protein expressions in both the kidney and liver of CKD rats. Furthermore, JPYS induced the phosphorylation of ERK1/2 protein. In addition, JPYS regulated protein expression of ferritin and FPN in both the liver and spleen of CKD rats and the serum level of hepcidin. In conclusion, JPYS induces the expression of EPO through ERK-mediated HIF-2α protein accumulation and regulates systemic iron recycling, supporting its role in promoting erythropoiesis and improvement of anemia in CKD.

Hypoxia Pathway Proteins are Master Regulators of Erythropoiesis

Erythropoiesis is a complex process driving the production of red blood cells. During homeostasis, adult erythropoiesis takes place in the bone marrow and is tightly controlled by erythropoietin (EPO), a central hormone mainly produced in renal EPO-producing cells. The expression of EPO is strictly regulated by local changes in oxygen partial pressure (pO₂) as under-deprived oxygen (hypoxia); the transcription factor hypoxia-inducible factor-2 induces EPO. However, erythropoiesis regulation extends beyond the well-established hypoxia-inducible factor (HIF)-EPO axis and involves processes modulated by other hypoxia pathway proteins (HPPs), including proteins involved in iron metabolism. The importance of a number of these factors is evident as their altered expression has been associated with various anemia-related disorders, including chronic kidney disease. Eventually, our emerging understanding of HPPs and their regulatory feedback will be instrumental in developing specific therapies for anemic patients and beyond.

Circulating levels of hydroxylated bradykinin function as an indicator of tissue HIF-1α expression

The critical roles of oxygen homeostasis in metabolism are indisputable and hypoxic responses are correlated with the pathogenesis of gastrointestinal, pulmonary, renal diseases and cancers. Evaluating tissue hypoxia to predict treatment outcome is challenging, however, due to the lack of rapid, accurate and non-invasive methods. Hypoxia enhances prolyl-4-hydroxylase α1 (P4HA1) expression, which can convert bradykinin (BK) to hydroxyprolyl-BK (Hyp-BK), leading us to hypothesize that circulating Hyp-BK/BK ratios may reflect tissue hypoxia and predict treatment outcomes. Direct quantification of Hyp-BK peptides in serum or plasma by conventional MALDI-TOF MS analysis is technically challenging. In our study, a nanopore-based fractionation and enrichment protocol was utilized to allow the simple workflow for circulating Hyp-BK/BK analysis. Hypoxia is linked to poor prognosis due to its role in promoting pancreatic cancer progression and metastasis. Here we show that P4HA1 expression was increased in pancreatic tumors versus adjacent tissue, associated with poor survival, and corresponded with tumor expression of the hypoxia inducible factor 1α (HIF-1α) and carbonic anhydrase 9 (CA9). Hypoxia-induced P4HA1 expression and BK conversion to Hyp-BK were found to be HIF-1α dependent, pre-treatment serum Hyp-BK/BK ratios corresponded with tissue HIF-1α and P4HA1 expression, and high Hyp-BK/BK levels corresponded with poor response to therapy. These results suggest that pre-treatment circulating Hyp-BK/BK ratios may have value as a non-invasive, surrogate indicator of tissue hypoxia and tumor responses to therapy.

Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors in Patients with Renal Anemia: A Meta-Analysis of Randomized Trials

BACKGROUND

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of treatment for renal anemia in patients with chronic kidney disease (CKD). This meta-analysis was designed to evaluate their efficacy and safety.

METHOD

Eight databases were searched for randomized controlled trials (RCTs). Information about efficacy and safety was extracted and combined using random-effects or fixed-effects models, depending on heterogeneity. Risk of bias was assessed using the method recommended by the Cochrane Centre.

RESULTS

Nineteen articles on RCTs were selected, involving 3,289 participants. We found that HIF-PHIs improved the level of hemoglobin (Hb) (weighted mean difference [WMD] 1.40; 95% CI: 0.96-1.84; p < 0.001), response rate of Hb (risk ratio [RR] 5.95; 95% CI: 3.95-8.96; p < 0.001), and total iron-binding capacity (WMD 42.94; 95% CI: 31.39-54.49; p < 0.001), while reducing the level of hepcidin (WMD -40.42; 95% CI: -50.44 to -30.39; p < 0.001), ferritin (WMD -64.60; 95% CI: -78.56 to -50.64; p < 0.001), and transferrin saturation (WMD -5.57; 95% CI: -8.53 to -2.61; p < 0.001). Meanwhile, there was no evidence of effect on serum iron (WMD 1.60; 95% CI: -3.72 to 6.93; p = 0.55), nor on the incidence of adverse events (AEs) (RR 1.06; 95% CI: 0.99-1.15; p = 0.51) or of serious adverse events (SAEs) (RR 1.14; 95% CI: 0.88-1.46; p = 0.32).

CONCLUSION

HIF-PHIs ameliorate renal anemia and rectify iron metabolism in the short term without increasing the incidence of AEs and SAEs.

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.

Phase 3, Randomized, Double-Blind, Active-Comparator (Darbepoetin Alfa) Study of Oral Roxadustat in CKD Patients with Anemia on Hemodialysis in Japan

BACKGROUND

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor approved in China for dialysis-dependent CKD anemia.

METHODS

This phase 3, 24-week, double-blind, double-dummy study evaluated roxadustat's noninferiority to darbepoetin alfa for hemodialysis-dependent CKD anemia. We randomly assigned Japanese patients to oral roxadustat three times weekly or to darbepoetin alfa injections once weekly, titrating doses to maintain hemoglobin between 10-12 g/dl. The primary end point was change of average hemoglobin from baseline to weeks 18-24 (∆Hb_18-24). Secondary end points were average hemoglobin and proportion of patients with hemoglobin between 10-12 g/dl (maintenance rate) at weeks 18-24, and iron parameters. Safety assessments included treatment-emergent adverse events and adjudicated ophthalmologic findings.

RESULTS

We randomly assigned 303 patients to roxadustat (n=151) or darbepoetin alfa (n=152). The difference between roxadustat and darbepoetin alfa in ∆Hb_18-24 was -0.02 g/dl (95% confidence interval, -0.18 to 0.15), confirming roxadustat's noninferiority to darbepoetin alfa. Average hemoglobin at weeks 18-24 with roxadustat was 10.99 g/dl (95% confidence interval: 10.88 to 11.10), confirming its efficacy. Among patients with one or more hemoglobin value during weeks 18-24, the maintenance rate was 95.2% with roxadustat and 91.3% with darbepoetin alfa. Serum iron, ferritin, and transferrin saturation remained clinically stable with roxadustat; transferrin and total iron binding capacity increased through week 4 before stabilizing. Common treatment-emergent adverse events were nasopharyngitis, shunt stenosis, diarrhea, contusion, and vomiting. The proportion of patients with new or worsening retinal hemorrhage was 32.4% with roxadustat and 36.6% with darbepoetin alfa. We observed no clinically meaningful changes in retinal thickness groups.

CONCLUSIONS

Roxadustat maintained hemoglobin within 10-12 g/dl in patients on hemodialysis and was noninferior to darbepoetin alfa. Treatment-emergent adverse events were consistent with previous reports.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

A Study of Intermittent Oral Dosing of ASP1517 in Hemodialysis Chronic Kidney Disease Patients with Anemia, NCT02952092 (ClinicalTrials.gov).

A Phase 3, Multicenter, Randomized, Two-Arm, Open-Label Study of Intermittent Oral Dosing of Roxadustat for the Treatment of Anemia in Japanese Erythropoiesis-Stimulating Agent-Naïve Chronic Kidney Disease Patients Not on Dialysis

INTRODUCTION

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor approved for the treatment of anemia in Japan for patients with dialysis-dependent (DD) chronic kidney disease (CKD).

OBJECTIVE

Multicenter, randomized, open-label, noncomparative, phase 3 study to evaluate roxadustat for anemia of non-dialysis-dependent (NDD) CKD in Japan.

METHODS

Erythropoiesis stimulating agent (ESA)-naïve NDD-CKD patients were randomized to roxadustat (initial dose, 50 or 70 mg 3 times weekly), titrated to maintain hemoglobin (Hb) within 10.0-12.0 g/dL, for ≤24 weeks. Patients with either transferrin saturation of ≥5% or serum ferritin of ≥30 ng/mL during the screening period were eligible. Endpoints included response rate (proportion of patients achieving Hb ≥10.0 or ≥10.5 g/dL and Hb increase ≥1.0 g/dL from baseline) at end of treatment; average Hb (weeks 18-24); change of average Hb from baseline to weeks 18-24; maintenance rate (proportion of patients achieving Hb 10.0-12.0 g/dL at weeks 18-24); rate of rise (RoR) of Hb from weeks 0-4, discontinuation, or dose adjustment. Adverse events were monitored throughout the study.

RESULTS

Of 135 patients who provided informed consent, 100 were randomized and 99 received roxadustat (50 mg, n = 49; 70 mg, n = 50). The mean (SD) dose of roxadustat per intake at week 22 was 36.3 (22.7) mg in the roxadustat 50 mg group and 36.8 (16.0) mg in the roxadustat 70 mg group. Prior medications included oral iron therapy (20.2%) and intravenous iron therapy (1.0%). Overall response rate (95% CI) was 97.0% (91.4, 99.4; Hb ≥10.0 g/dL) and 94.9% (88.6, 98.3; Hb ≥10.5 g/dL). Mean (SD) Hb (weeks 18-24) was 11.17 (0.62) g/dL. Mean (SD) change of Hb from baseline (weeks 18-24) was 1.34 (0.86) g/dL. Maintenance rate (95% CI) was 88.8% (80.3, 94.5) among patients with ≥1 Hb measurement during weeks 18-24. Mean (SD) RoR of Hb was 0.291 (0.197) g/dL/week (50 mg) and 0.373 (0.235) g/dL/week (70 mg). Nasopharyngitis and hypertension were the most common adverse events.

CONCLUSION

Roxadustat increased and maintained Hb in ESA-naïve, partially iron-depleted NDD-CKD patients with anemia.

Hypoxia-inducible factor prolyl hydroxylase inhibitors: a paradigm shift for treatment of anemia in chronic kidney disease?

INTRODUCTION

The hypoxia-inducible factor prolyl hydroxylase (HIF-PH) pathway is responsible for regulating the biosynthesis of erythropoietin (EPO) and maintaining iron homeostasis. Investigational drugs that target the HIF-PH pathway are promising alternatives for treating anemia in Chronic Kidney Disease (CKD).

AREAS COVERED

This review summarizes recent advances focused on the clinical development of HIF-PH inhibitors (HIF-PHIs) as potentially novel therapies in the treatment of anemia in CKD based on publications available on PubMed and restricted Google searches. We provide a comparison between HIF-PHIs regarding their pharmacokinetics, dosing regimens and safety concerns, structure-activity relationships, and alterations in key laboratory parameters observed in animal models and clinical trials.

EXPERT OPINION

HIF-PHIs may be advantageous in some aspects compared to the conventional erythropoiesis-stimulating agents (ESAs). While ESAs could increase the risk of cardiovascular events due to rapid rises in ESA blood levels, HIF-PHIs have been reported to maintain EPO concentrations at levels that are closer to the normal physiological ranges. Although HIF-PHIs have been demonstrated to be relatively safe and effective in clinical trials, long-term safety data are needed in order to establish whether these therapeutic agents will lead to a major paradigm change in the treatment of anemia of CKD.

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.

Oral roxadustat three times weekly in ESA-naïve and ESA-converted patients with anemia of chronic kidney disease on hemodialysis: Results from two phase 3 studies

Roxadustat is a hypoxia-inducible factor prolyl hydroxylase inhibitor approved in China for anemia of dialysis-dependent chronic kidney disease (CKD). Japanese hemodialysis patients with anemia of CKD previously naïve to, or converted from, erythropoiesis-stimulating agents (ESAs) were enrolled in two open-label, noncomparative studies of titrated oral roxadustat administered three times weekly. ESA-naïve patients (n = 75) were randomized to roxadustat (initial dose, 50 or 70 mg) for 24 weeks; ESA-converted patients (n = 164) were assigned to roxadustat (initial dose, 70 or 100 mg based on prior ESA dose) for 52 weeks. Efficacy outcomes included average hemoglobin (Hb, weeks 18-24 or 46-52), change of Hb from baseline to weeks 18 to 24 (ΔHb_18-24 ) or weeks 46 to 52 (ΔHb_46-52 ), and maintenance rate (proportion of patients who achieved average Hb of 10.0-12.0 g/dL for weeks 18-24 or weeks 46-52). Treatment-emergent adverse events (TEAEs) were monitored. Mean (SD) Hb was 10.93 (0.79) g/dL (weeks 18-24) (ESA-Naïve Study), and 10.93 (0.69; weeks 18-24) g/dL and 11.11 (0.67; weeks 46-52) g/dL (ESA-Converted Study). Mean (SD) ΔHb_18-24 was 2.26 (1.02) g/dL (ESA-Naïve Study) and -0.03 (0.90) g/dL (ESA-Converted Study); mean (SD) ΔHb_46-52 was 0.12 (0.83) g/dL (ESA-Converted Study). The overall maintenance rate was 73.0% (54/74) (ESA-Naïve Study) (weeks 18-24), and 79.1% (129/163; weeks 18-24) and 71.2% (116/163; weeks 46-52) (ESA-Converted Study). Nasopharyngitis was the most common TEAE. Two deaths, considered unrelated to roxadustat, occurred in the ESA-Converted Study. Roxadustat effectively corrected and maintained Hb, regardless of previous ESA treatment, in Japanese anemic CKD patients on hemodialysis.

Roxadustat: First Global Approval

Roxadustat (Ai Rui Zhuo^® in China) is an orally administered, small molecule hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor that is being developed by FibroGen, in collaboration with Astellas and AstraZeneca, for the treatment of anaemia in patients with dialysis-dependent chronic kidney disease (CKD), non-dialysis-dependent CKD and in patients with myelodysplastic syndromes. The drug reversibly binds to and inhibits HIF-prolyl hydroxylase enzymes that are responsible for the degradation of transcription factors in the HIF family under normal oxygen conditions. Inhibition of these enzymes reduces HIF breakdown and promotes HIF activity, leading to an increase in endogenous erythropoietin production, thereby enhancing erythropoiesis. It also reduces the expression of the peptide hormone hepcidin, improves iron availability and increases haemoglobin levels. HIF regulates the expression of genes in response to reduced oxygen levels, including genes required for erythropoiesis and iron metabolism. Roxadustat is approved in China and is under regulatory review in Japan for the treatment of anaemia in patients with dialysis-dependent CKD. Studies are underway to investigate long-term cardiovascular outcomes with roxadustat versus placebo (for non-dialysis-dependent CKD) or standard of care (for dialysis-dependent CKD). This article summarizes the milestones in the development of roxadustat leading to this first approval.

Anemia management in cancer patients with chronic kidney disease

Cancer and kidney disease are linked by causality and comorbidities. Observational data show an increased risk of malignancy as renal function declines. Erythropoietin stimulating agents (ESAs), which are the cornerstone therapy for anemia patients with chronic kidney disease and cancer, are associated with increased risks for cancer, cancer-related mortality, progression of disease, and thromboembolic events. This article examines the recently published guidelines for ESA use in cancer patients from the American Society of Clinical Oncology and American Society of Hematology and attempts to contextualize them to the care of patients with coexistent CKD, cancer, and anemia.

Intermittent Oral Dosing of Roxadustat in Peritoneal Dialysis Chronic Kidney Disease Patients with Anemia: A Randomized, Phase 3, Multicenter, Open-Label Study

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor developed to treat anemia in chronic kidney disease (CKD) patients. This Phase 3, randomized, open-label, 24-week study investigated the efficacy and safety of roxadustat in Japanese CKD patients with anemia on peritoneal dialysis (PD) who were previously treated or not treated with erythropoiesis stimulating agents (ESAs). Patients not previously receiving ESA (ESA-Naïve group) were randomized to roxadustat at a starting dose of 50 or 70 mg three times weekly; patients previously receiving ESA (ESA-Converted group) switched from ESA to roxadustat 70 or 100 mg three times weekly depending on the prior ESA dose. Outcomes included maintenance rate of average hemoglobin (Hb) level within 10-12 g/dL at weeks 18-24, cumulative response rate at end of treatment (Hb thresholds, 10.0 g/dL or 10.5 g/dL; Hb increase, ≥1.0 g/dL), and average Hb levels at weeks 18-24. Safety was assessed by occurrence of treatment-emergent adverse events (TEAEs). Fifty-six patients were enrolled (ESA-Naïve, n = 13; ESA-Converted, n = 43). Maintenance rates (weeks 18-24) were 92.3% (95% CI: 64.0-99.8; ESA-Naïve) and 74.4% (95% CI: 58.8-86.5; ESA-Converted). Cumulative response rate was 100.0% in the ESA-Naïve group. Average Hb levels (weeks 18-24) were 11.05 g/dL (95% CI: 10.67-11.42; ESA-Naïve) and 10.93 g/dL (95% CI: 10.73-11.13; ESA-Converted). Common TEAEs included nasopharyngitis and back pain. Roxadustat was well tolerated and effective in maintaining target Hb levels in CKD patients on PD who were previously treated or not treated with ESA.

Roxadustat Treatment of Chronic Kidney Disease-Associated Anemia in Japanese Patients Not on Dialysis: A Phase 2, Randomized, Double-Blind, Placebo-Controlled Trial

Introduction

This study evaluated efficacy and safety/tolerability of roxadustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, in Japanese anemic non-dialysis-dependent chronic kidney disease (NDD-CKD) patients.

Methods

In this phase 2, double-blind, 24-week study, NDD-CKD patients were randomized to oral placebo or roxadustat (50, 70, or 100 mg) three times weekly (TIW) for 6 weeks followed by dose adjustments to maintain hemoglobin (Hb) at 10–12 g/dL for 18 weeks; patients meeting pre-defined criteria were re-randomized to TIW or once-weekly dosing. The primary end point was rate of rise of Hb (g/dL/week) during the first 6 weeks; secondary end points included response rate (Hb ≥ 10.0 g/dL and increase in Hb from baseline ≥ 1 g/dL) and mean Hb and change from baseline in Hb at weeks 18–24. The main safety outcomes were vital signs, laboratory test results, electrocardiograms, and frequency of treatment-emergent adverse events.

Results

Of 107 patients randomized, 83 completed the study. The mean (SD) rate of rise of Hb during the first 6 weeks was − 0.052 (0.142) for placebo and + 0.200 (0.160), + 0.453 (0.256), and + 0.570 (0.240) for roxadustat 50-, 70-, and 100-mg TIW groups, respectively (p < 0.001). Response rate was 14.8% for placebo and 81.5%, 100%, and 100% for roxadustat TIW groups (p < 0.001). Change in Hb from baseline at weeks 18–24 was − 0.17 (0.61) for placebo and + 1.10 (0.71), + 1.33 (0.82), and + 1.55 (0.88) g/dL for roxadustat TIW groups (p < 0.001). No deaths or major adverse cardiac events occurred with roxadustat.

Conclusion

Roxadustat was well tolerated and effective in correcting Hb levels within 6 weeks in Japanese anemic NDD-CKD patients.

Trial registration

ClinicalTrials.gov: NCT01964196. Registered 15 October 2013 (retrospectively registered).

Funding

Astellas Pharma Inc.

Electronic supplementary material

The online version of this article (10.1007/s12325-019-00943-4) contains supplementary material, which is available to authorized users.

Stabilization of hypoxia-inducible factor 1α by cobalt chloride impairs podocyte morphology and slit-diaphragm function

Glomerular podocytes are the major components of the renal filtration barrier, and altered podocyte permselectivity is a key event in the pathogenesis of proteinuric conditions. Clinical conditions such as ischemia and sleep apnea and extreme physiological conditions such as high-altitude sickness are presented with renal hypoxia and are associated with significant proteinuria. Hypoxia is considered as an etiological factor in the progression of acute renal injury. A sustained increase in hypoxia-inducible factor 1α (HIF1α) is a major adaptive stimulus to the hypoxic conditions. Although the temporal association between hypoxia and proteinuria is known, the mechanism by which hypoxia elicits proteinuria remains to be investigated. Furthermore, stabilization of HIF1α is being considered as a therapeutic option to treat anemia in patients with chronic kidney disease. Therefore, in this study, we induced stabilization of HIF1α in glomerular regions in vivo and in podocytes in vitro upon exposure to cobalt chloride. The elevated HIF1α expression is concurrence with diminished expression of nephrin and podocin, podocyte foot-processes effacement, and significant proteinuria. Podocytes exposed to cobalt chloride lost their arborized morphology and cell-cell connections and also displayed cytoskeletal derangements. Elevation in expression of HIF1α is in concomitance with loss of nephrin and podocin in patients with diabetic nephropathy and chronic kidney disease. In summary, the current study suggests that HIF1α stabilization impairs podocyte function vis-à-vis glomerular permselectivity.

Review of WADA Prohibited Substances: Limited Evidence for Performance-Enhancing Effects

The World Anti-Doping Agency is responsible for maintaining a Prohibited List that describes the use of substances and methods that are prohibited for athletes. The list currently contains 23 substance classes, and an important reason for the existence of this list is to prevent unfair competition due to pharmacologically enhanced performance. The aim of this review was to give an overview of the available evidence for performance enhancement of these substance classes. We searched the scientific literature through PubMed for studies and reviews evaluating the effects of substance classes on performance. Findings from double-blind, randomized controlled trials were considered as evidence for (the absence of) effects if they were performed in trained subjects measuring relevant performance outcomes. Only 5 of 23 substance classes show evidence of having the ability to enhance actual sports performance, i.e. anabolic agents, β2-agonists, stimulants, glucocorticoids and β-blockers. One additional class, growth hormone, has similar evidence but only in untrained subjects. The observed effects all relate to strength or sprint performance (and accuracy for β-blockers); there are no studies showing positive effects on reliable markers of endurance performance. For 11 classes, no well-designed studies are available, and, for the remaining six classes, there is evidence of an absence of a positive effect. In conclusion, for the majority of substance classes, no convincing evidence for performance enhancement is available, while, for the remaining classes, the evidence is based on a total of only 266 subjects from 11 studies.

mRNA-to-protein translation in hypoxia

Cells respond to hypoxia by shifting cellular processes from general housekeeping functions to activating specialized hypoxia-response pathways. Oxygen plays an important role in generating ATP to maintain a productive rate of protein synthesis in normoxia. In hypoxia, the rate of the canonical protein synthesis pathway is significantly slowed and impaired due to limited ATP availability, necessitating an alternative mechanism to mediate protein synthesis and facilitate adaptation. Hypoxia adaptation is largely mediated by hypoxia-inducible factors (HIFs). While HIFs are well known for their transcriptional functions, they also play imperative roles in translation to mediate hypoxic protein synthesis. Such adaptations to hypoxia are often hyperactive in solid tumors, contributing to the expression of cancer hallmarks, including treatment resistance. The current literature on protein synthesis in hypoxia is reviewed here, inclusive of hypoxia-specific mRNA selection to translation termination. Current HIF targeting therapies are also discussed as are the opportunities involved with targeting hypoxia specific protein synthesis pathways.

Effect of Multiple Doses of Omeprazole on the Pharmacokinetics, Safety, and Tolerability of Roxadustat in Healthy Subjects

BACKGROUND AND OBJECTIVES

Roxadustat is an orally active hypoxia-inducible factor prolyl hydroxylase inhibitor for the treatment of anemia in chronic kidney disease. This study investigated the effect of multiple daily oral doses of omeprazole on the pharmacokinetics, safety, and tolerability of a single oral dose of roxadustat.

METHODS

This phase 1, open-label, two-period, one-sequence, crossover study enrolled healthy subjects. During Period 1, subjects received a single oral dose of 100 mg roxadustat. After a ≥ 7-day washout, subjects started Period 2 and received daily oral doses of 40 mg omeprazole on Days 1-9, and a single oral dose of 100 mg roxadustat on Day 7. Roxadustat pharmacokinetics were assessed on Days 1-4 in Period 1 and on Days 7-10 in Period 2. Primary endpoints were area under the concentration-time profile from the time of dosing extrapolated to infinity (AUC_inf) and maximum concentration (C_max). Safety was assessed by vital signs, laboratory tests, electrocardiograms, and nature, frequency, and severity of treatment-emergent adverse events (TEAEs).

RESULTS

Eighteen subjects were enrolled. The geometric least squares mean ratio for both AUC_inf and C_max of roxadustat (with omeprazole/alone) was 104.5%; 90% confidence intervals were within the no-effect boundaries of 80.0 and 125.0%, indicating no significant effect of omeprazole on the pharmacokinetics of roxadustat. No serious TEAEs were reported.

CONCLUSION

Multiple daily oral doses of 40 mg omeprazole had no significant effect on the pharmacokinetics of a single oral dose of 100 mg roxadustat. Roxadustat was considered safe and well tolerated when administered alone or in combination with multiple daily oral doses of 40 mg omeprazole in healthy subjects.

Jian-Pi-Yi-Shen Decoction Relieves Renal Anemia in 5/6 Nephrectomized Rats: Production of Erythropoietin via Hypoxia Inducible Factor Signaling

Jian-Pi-Yi-Shen (JPYS) is one of the herbal medicines for treatment of anemic patients with chronic kidney disease (CKD). However, less of scientific evidence to support JPYS involved in treating anemia has been revealed. Here, an animal study was performed to investigate its hematopoietic activities and the underlying mechanism. The 5/6 nephrectomized inductions of CKD anemic rats were randomly divided into two groups: CKD group and JPYS group. Sham-operated rats served as sham group. JPYS (1.36 g/kg/d) was administered orally to CKD rats daily for six consecutive weeks. Results showed that JPYS treatment notably improved renal function and pathological injury in CKD rats. JPYS also restored the hematological parameters, including red blood cells, hemoglobin, and hematocrit. In parallel, the reduction level of EPO was reversed by JPYS. Furthermore, JPYS induced the accumulation of hypoxia inducible factor (HIF)-α protein expression. Collectively, these results provide convincing evidence for JPYS decoction in ameliorating CKD-associated anemia, and its mechanism might be related to regulate EPO production via HIF signaling pathway.

A Placebo-Controlled, Randomized Trial of Enarodustat in Patients with Chronic Kidney Disease Followed by Long-Term Trial

BACKGROUND

Enarodustat (JTZ-951) is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that mimics adaptive responses to hypoxic conditions and may provide a new therapeutic approach for managing anemia in patients with chronic kidney disease (CKD). We evaluated the efficacy, safety, and maintenance dose of enarodustat in anemic patients with CKD not on dialysis.

METHODS

Erythropoiesis-stimulating agent (ESA) naïve patients (correction group) and patients on a stable dose of ESA (conversion group) were randomized to receive 2, 4, or 6 mg of enarodustat or placebo once daily for 6 weeks in a double-blind manner (Period 1) followed by 24 weeks of open enarodustat treatment to maintain their hemoglobin (Hb) levels within a target range of 10.0-12.0 g/dL in reference to a dose adjustment algorithm (Period 2).

RESULTS

In the correction group, Hb level increase rate per week increased in a dose-response manner. The proportion of subjects in the conversion group who maintained Hb levels within ± 1.0 g/dL of baseline did not differ between each enarodustat arm and placebo arm during Period 1. Over 70% of subjects in both groups maintained Hb levels within the target range at the end of treatment in Period 2. The mean prescribed doses were 3.58 and 3.74 mg/day in the correction group and the conversion group, respectively. Enarodustat was associated with decreases in hepcidin and ferritin and increased total iron-binding capacity and was generally well tolerated.

CONCLUSIONS

Enarodustat corrects and maintains Hb levels in anemic patients with CKD not on dialysis.

RNA-seq analysis of PHD and VHL inhibitors reveals differences and similarities to the hypoxia response

Background: Hypoxia-inducible factor (HIF) transcription factors are well known to control the transcriptional response to hypoxia. Given the importance of cellular response to hypoxia, a number of pharmacological agents to interfere with this pathway have been developed and entered pre-clinical or clinical trial phases. However, how similar or divergent the transcriptional response elicited by different points of interference in cells is currently unknown. Methods: We performed RNA-sequencing to analyse the similarities and differences of transcriptional response in HeLa cells treated with hypoxia or chemical agents that stabilise HIF by inhibiting components of the hypoxia signalling pathway - prolyl hydroxylase (PHD) inhibitor or von Hippel-Lindau (VHL) inhibitor. Results: This analysis revealed that hypoxia produces the highest changes in gene transcription, with activation and repression of genes being in large numbers. Treatment with the PHD inhibitor IOX2 or the VHL inhibitor VH032 led mostly to gene activation, majorly via a HIF-dependent manner. These results were also confirmed by qRT-PCR using more specific and/or efficient inhibitors, FG-4592 (PHDs) and VH298 (VHL). Conclusion: PHD inhibition and VHL inhibition mimic gene activation promoted by hypoxia via a HIF-dependent manner. However, gene repression is mostly associated with the hypoxia response and not common to the response elicited by inhibitors of the pathway.

Protective Role of Histidine Supplementation Against Oxidative Stress Damage in the Management of Anemia of Chronic Kidney Disease

Anemia is a major health condition associated with chronic kidney disease (CKD). A key underlying cause of this disorder is iron deficiency. Although intravenous iron treatment can be beneficial in correcting CKD-associated anemia, surplus iron can be detrimental and cause complications. Excessive generation of reactive oxygen species (ROS), particularly by mitochondria, leads to tissue oxidation and damage to DNA, proteins, and lipids. Oxidative stress increase in CKD has been further implicated in the pathogenesis of vascular calcification. Iron supplementation leads to the availability of excess free iron that is toxic and generates ROS that is linked, in turn, to inflammation, endothelial dysfunction, and cardiovascular disease. Histidine is indispensable to uremic patients because of the tendency toward negative plasma histidine levels. Histidine-deficient diets predispose healthy subjects to anemia and accentuate anemia in chronic uremic patients. Histidine is essential in globin synthesis and erythropoiesis and has also been implicated in the enhancement of iron absorption from human diets. Studies have found that L-histidine exhibits antioxidant capabilities, such as scavenging free radicals and chelating divalent metal ions, hence the advocacy for its use in improving oxidative stress in CKD. The current review advances and discusses evidence for iron-induced toxicity in CKD and the mechanisms by which histidine exerts cytoprotective functions.

Metabolic syndrome: an update on diagnostic criteria, pathogenesis, and genetic links

Metabolic syndrome (MetS), today a major global public health problem, is a cluster of clinical, metabolic, and biochemical abnormalities, such as central adiposity, hypertension, insulin resistance, and dyslipidemias. These MetS-related traits significantly increase the risk of type 2 diabetes mellitus, adverse cardiac events, stroke, and hepatic steatosis. The pathogenesis of MetS is multifactorial, with the interplay of environmental, nutritional, and genetic factors. Chronic low-grade inflammation together with visceral adipose tissue, adipocyte dysfunction, and insulin resistance plays a major role in the progression of the syndrome by impairing lipid and glucose homeostasis in insulin-sensitive tissues, such as the liver, muscle, and adipocytes. Adipose-derived inflammatory cytokines and non-esterified fatty acids establish the link between central obesity IR, inflammation, and atherogenesis. Various studies have reported an association between MetS and related traits with single-nucleotide polymorphisms of different susceptibility genes. Modulation of cytokine levels, pro-oxidants, and disturbed energy homeostasis, in relation to the genetic variations, is described in this review of the recent literature, which also provides updated data regarding the epidemiology, diagnostic criteria, and pathogenesis of MetS.

Correction of Anemia in Chronic Kidney Disease With Angelica sinensis Polysaccharide via Restoring EPO Production and Improving Iron Availability

Given the limited efficacy and potential disadvantages of erythropoiesis-stimulating agents (ESAs) in treating anemia of chronic kidney disease (CKD), the development of better alternative therapies has become a priority. The primary purpose of this study is to investigate the effects of Angelica sinensis polysaccharide (ASP) and its underlying mechanism in the treatment of renal anemia. In the present study, we found that ASP could enhance hypoxic induction of EPO in Hep3B cells, with a mechanism that involved the stabilization of HIF-2α protein. In parallel, ASP rescued the inhibition of EPO, induced by proinflammatory factor TNF-α through blocking GATA2 and NF-κB activation. In a rat model of adenine-induced anemia of CKD, oral administration of ASP corrected anemia and alleviated renal damage and inflammation. By increasing the accumulation of HIF-2α protein and reducing the expression of NF-κB and GATA2 as well as pro-inflammatory cytokines, ASP stimulated both renal and hepatic EPO production, and resulted in an elevation of serum EPO. The restoration of EPO production and EPOR mRNA expression with ASP treatment activated EPOR downstream JAK2/STAT5 and PI3K/Akt signaling, induced their target genes, such as Bcl-xL, Fam132b and Tfrc, and increased Bcl-2/Bax ratio in bone marrow-derived mononuclear cells of CKD rats. Furthermore, we found that ASP suppressed hepatic hepcidin expression, mobilized iron from spleen and liver and increased serum iron. These findings demonstrate that ASP elicits anti-anemic action by restoring EPO production and improving iron availability in the setting of CKD in rats.

Iron therapy for managing anaemia in chronic kidney disease

PURPOSE OF REVIEW

Iron deficiency is a major contributory cause to the development of anaemia in chronic kidney disease (CKD), and thus, iron replacement therapy plays a critical role in the management of this condition. The two main routes for administering iron are oral and intravenous, and there have been a number of new publications relevant to both routes of administration.

RECENT FINDINGS

Recent developments on the topic of iron management in CKD include the introduction of new oral iron preparations, as well as two recent meta-analyses on iron therapy in CKD (one on oral versus intravenous iron, and one on high- versus low-dose intravenous iron in haemodialysis patients). There is also increasing interest in other strategies to improve iron availability, such as intradialytic iron, hypoxia-inducible factor stabilization and antihepcidin strategies.

SUMMARY

Even despite the latest publications in this field, we are still left with serious gaps in our evidence base on how best to provide supplemental iron to CKD patients. Most of the evidence suggests that intravenous iron is superior to oral iron in increasing haemoglobin and minimizing the use of erythropoiesis-stimulating agents, but the safety of intravenous iron remains a controversy. The PIVOTAL study will hopefully provide informative data to fill some of the gap in the evidence-base and inform best clinical practice.

Discovery of Molidustat (BAY 85-3934): A Small-Molecule Oral HIF-Prolyl Hydroxylase (HIF-PH) Inhibitor for the Treatment of Renal Anemia

Small-molecule inhibitors of hypoxia-inducible factor prolyl hydroxylases (HIF-PHs) are currently under clinical development as novel treatment options for chronic kidney disease (CKD) associated anemia. Inhibition of HIF-PH mimics hypoxia and leads to increased erythropoietin (EPO) expression and subsequently increased erythropoiesis. Herein we describe the discovery, synthesis, structure-activity relationship (SAR), and proposed binding mode of novel 2,4-diheteroaryl-1,2-dihydro-3H-pyrazol-3-ones as orally bioavailable HIF-PH inhibitors for the treatment of anemia. High-throughput screening of our corporate compound library identified BAY-908 as a promising hit. The lead optimization program then resulted in the identification of molidustat (BAY 85-3934), a novel small-molecule oral HIF-PH inhibitor. Molidustat is currently being investigated in clinical phase III trials as molidustat sodium for the treatment of anemia in patients with CKD.

Hypoxia-inducible factor activation in diabetic kidney disease

PURPOSE OF REVIEW

Tissue hypoxia is present in kidneys from diabetic patients and constitutes a central pathway to diabetic kidney disease (DKD). This review summarizes regulation of hypoxia inducible factor (HIF) and interventions towards the same for treatment of DKD.

RECENT FINDINGS

In the hypoxic diabetic kidney, HIF activity and the effects of HIF signaling seem to be cell-specific. In mesangial cells, elevated glucose levels induce HIF activity by a hypoxia-independent mechanism. Elevated HIF activity in glomerular cells promotes glomerulosclerosis and albuminuria, and inhibition of HIF protects glomerular integrity. However, tubular HIF activity is suppressed and HIF activation protects mitochondrial function and prevents development of diabetes-induced tissue hypoxia, tubulointerstitial fibrosis and proteinuria. No clinical treatment targeting kidney hypoxia is currently available, but development of prolyl hydroxylase inhibitors to promote HIF activity to treat renal anemia could potentially also target diabetes-induced kidney hypoxia.

SUMMARY

Increasing HIF activity in the diabetic kidney may possess a novel target for treatment of DKD by improving kidney oxygen homeostasis. However, HIF-mediated glomerulosclerosis may be a concern. The kidney outcomes from the ongoing clinical trials using prolyl hydroxylase inhibitors may provide additional insights into the complex role of HIF signaling in the diabetic kidney.

The Hypoxia-Adenosine Link during Intestinal Inflammation

Intestinal inflammation is a key element in inflammatory bowel disease and is related to a combination of factors, including genetics, mucosal barrier dysfunction, bacteria translocation, deleterious host-microbe interactions, and dysregulated immune responses. Over the past decade, it has been appreciated that these inflammatory lesions are associated with profound tissue hypoxia. Interestingly, an endogenous adaptive response under the control of hypoxia signaling is enhancement in adenosine signaling, which impacts these different endpoints, including promoting barrier function and encouraging anti-inflammatory activity. In this review, we discuss the hypoxia-adenosine link in inflammatory bowel disease, intestinal ischemia/reperfusion injury, and colon cancer. In addition, we provide a summary of clinical implications of hypoxia and adenosine signaling in intestinal inflammation and disease.

Anemia in chronic kidney disease

Anemia is common and associated with adverse outcomes in children with chronic kidney disease (CKD). Many factors contribute to declining hemoglobin as CKD progresses, but impaired production of erythropoietin by failing kidneys is a central cause. Hepcidin-mediated iron restriction also contributes to anemia by downregulating both intestinal iron absorption and release of stored iron for erythropoiesis. The core components of anemia management remain erythropoiesis-stimulating agents (ESA) and iron supplementation, but despite these therapies, a substantial number of children remain anemic. Although escalating ESA dose to target higher hemoglobin has been associated with adverse outcomes in adults, no trials have investigated this association in children, and maintaining hemoglobin levels in a narrow range with conservative ESA dosing is challenging. Judicious use of iron supplementation can enhance the response to ESAs, but the iron storage markers most commonly used in clinical practice have limitations in distinguishing which patients will benefit most from additional iron. Several novel anemia therapies, including hypoxia-inducible factor stabilizers, prolyl hydroxylase inhibitors, and dialysate-delivered iron supplements, have been developed and may offer options for alternative anemia management. However, the safety and efficacy of these agents in children with CKD has yet to be assessed.

Treatment of renal anemia: Erythropoiesis stimulating agents and beyond

Anemia, complicating the course of chronic kidney disease, is a significant parameter, whether interpreted as subjective impairment or an objective prognostic marker. Renal anemia is predominantly due to relative erythropoietin (EPO) deficiency. EPO inhibits apoptosis of erythrocyte precursors. Studies using EPO substitution have shown that increasing hemoglobin (Hb) levels up to 10–11 g/dL is associated with clinical improvement. However, it has not been unequivocally proven that further intensification of erythropoiesis stimulating agent (ESA) therapy actually leads to a comprehensive benefit for the patient, especially as ESAs are potentially associated with increased cerebro-cardiovascular events. Recently, new developments offer interesting options not only via stimulating erythropoeisis but also by employing additional mechanisms. The inhibition of activin, a member of the transforming growth factor superfamily, has the potential to correct anemia by stimulating liberation of mature erythrocyte forms and also to mitigate disturbed mineral and bone metabolism as well. Hypoxia-inducible factor prolyl hydroxylase inhibitors also show pleiotropic effects, which are at the focus of present research and have the potential of reducing mortality. However, conventional ESAs offer an extensive body of safety evidence, against which the newer substances should be measured. Carbamylated EPO is devoid of Hb augmenting effects whilst exerting promising tissue protective properties. Additionally, the role of hepcidin antagonists is discussed. An innovative new hemodialysis blood tube system, reducing blood contact with air, conveys a totally different and innocuous option to improve renal anemia by reducing mechanical hemolysis.

Iron-based phosphate binders: a paradigm shift in the treatment of hyperphosphatemic anemic CKD patients?

The partial correction of anemia and the normalization of phosphate and blood pressure are the mainstay of treatment of patients with chronic kidney disease (CKD). Available anti-hypertensive drugs, erythropoiesis stimulating agents (ESAs) and iron supplements have resolved quite satisfactorily the goal of controlling hypertension and partially correcting anemia. Unfortunately, the treatment of hyperphosphatemia is still far from resolved. Phosphate binders have poor tolerability and/or limited efficacy, leading to the prescription of many tablets that achieve only a mild-to-moderate effect. Moreover, increased consumption of tablets is associated with increased low tolerability, thus jeopardizing patient compliance and, in turn, the efficacy of phosphate binding. Compared to calcium-free binders, the cheaper calcium salts increase the risk of hypercalcemia, calciphylaxis and vascular calcification and possibly all-cause mortality. Calcium-free phosphate binders decrease serum phosphate levels without increasing the serum calcium concentration. The higher phosphate-binding efficacy of lanthanum carbonate compared to sevelamer should be balanced against its lack of pleiotropic effects on lipid metabolism and inflammation and the accumulation in bones. New iron-based phosphate binders are available. In addition to their phosphate binding capacity, they could also be useful to treat anemia. Iron citrate is seeking for such an indication because its iron absorption is significant. This could be of clinical importance, particularly in CKD patients not on dialysis, obviating the need for extra oral iron administration and possibly favoring compliance. In conclusion, the use of iron-based phosphate binders with significant iron absorption properties could represent a novel paradigm for correcting anemia and hyperphosphatemia in CKD patients.