The Safety of Erythropoiesis-Stimulating Agents for the Treatment of Anemia Resulting from Chronic Kidney Disease

Hypoxia-inducible factor activation promotes osteogenic transition of valve interstitial cells and accelerates aortic valve calcification in a mice model of chronic kidney disease

Introduction

Valve calcification (VC) is a widespread complication in chronic kidney disease (CKD) patients. VC is an active process with the involvement of in situ osteogenic transition of valve interstitial cells (VICs). VC is accompanied by the activation of hypoxia inducible factor (HIF) pathway, but the role of HIF activation in the calcification process remains undiscovered.

Methods and result

Using in vitro and in vivo approaches we addressed the role of HIF activation in osteogenic transition of VICs and CKD-associated VC. Elevation of osteogenic (Runx2, Sox9) and HIF activation markers (HIF-1α and HIF-2α) and VC occurred in adenine-induced CKD mice. High phosphate (Pi) induced upregulation of osteogenic (Runx2, alkaline-phosphatase, Sox9, osteocalcin) and hypoxia markers (HIF-1α, HIF-2α, Glut-1), and calcification in VICs. Down-regulation of HIF-1α and HIF-2α inhibited, whereas further activation of HIF pathway by hypoxic exposure (1% O₂) or hypoxia mimetics [desferrioxamine, CoCl₂, Daprodustat (DPD)] promoted Pi-induced calcification of VICs. Pi augmented the formation of reactive oxygen species (ROS) and decreased viability of VICs, whose effects were further exacerbated by hypoxia. N-acetyl cysteine inhibited Pi-induced ROS production, cell death and calcification under both normoxic and hypoxic conditions. DPD treatment corrected anemia but promoted aortic VC in the CKD mice model.

Discussion

HIF activation plays a fundamental role in Pi-induced osteogenic transition of VICs and CKD-induced VC. The cellular mechanism involves stabilization of HIF-1α and HIF-2α, increased ROS production and cell death. Targeting the HIF pathways may thus be investigated as a therapeutic approach to attenuate aortic VC.

Daprodustat Accelerates High Phosphate-Induced Calcification Through the Activation of HIF-1 Signaling

Aims: Chronic kidney disease (CKD) is frequently associated with other chronic diseases including anemia. Daprodustat (DPD) is a prolyl hydroxylase inhibitor, a member of a family of those new generation drugs that increase erythropoiesis via activation of the hypoxia-inducible factor 1 (HIF-1) pathway. Previous studies showed that HIF-1 activation is ultimately linked to acceleration of vascular calcification. We aimed to investigate the effect of DPD on high phosphate-induced calcification.

Methods and Results: We investigated the effect of DPD on calcification in primary human aortic vascular smooth muscle cells (VSMCs), in mouse aorta rings, and an adenine and high phosphate-induced CKD murine model. DPD stabilized HIF-1α and HIF-2α and activated the HIF-1 pathway in VSMCs. Treatment with DPD increased phosphate-induced calcification in cultured VSMCs and murine aorta rings. Oral administration of DPD to adenine and high phosphate-induced CKD mice corrected anemia but increased aortic calcification as assessed by osteosense staining. The inhibition of the transcriptional activity of HIF-1 by chetomin or silencing of HIF-1α attenuated the effect of DPD on VSMC calcification.

Conclusion: Clinical studies with a long follow-up period are needed to evaluate the possible risk of sustained activation of HIF-1 by DPD in accelerating medial calcification in CKD patients with hyperphosphatemia.

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

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

Effect of hypoxia-inducible factor-prolyl hydroxylase inhibitors on anemia in patients with CKD: a meta-analysis of randomized controlled trials including 2804 patients

Hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) are orally active first-in-class new generation drugs for renal anemia. This extensive meta-analysis of randomized controlled trials (RCTs) was designed to provide clear information on the efficacy and safety of HIF-PHIs on anemia in chronic kidney disease (CKD) patients. Searches included PubMed, Web of Science, Ovid MEDLINE, and Cochrane Library database up to October 2019. RCTs of patients with CKD comparing HIF-PHIs with erythropoiesis-stimulating agents (ESAs) or placebo in the treatment of anemia. The primary outcome was hemoglobin change from baseline (Hb CFB); the secondary outcomes included iron-related parameters and the occurrence of each adverse event. 26 trials in 17 articles were included, with a total of 2804 dialysis or patients with CKD. HIF-PHIs treatment produced a significant beneficial effect on Hb CFB compared with the placebo group (MD, 0.69; 95% CI, 0.36 to 1.02). However, this favored effect of HIF-PHIs treatment was not observed in subgroup analysis among trials compared with ESAs (MD, 0.06; 95% CI, -0.20 to 0.31). The significant reduction in hepcidin by HIF-PHIs was observed in all subgroups when compared with the placebo group, whereas this effect was observed only in NDD-CKD patients when compared with ESAs. HIF-PHIs increased the risk of nausea (RR, 2.20; 95% CI, 1.06 to 4.53) and diarrhea (RR, 1.75; 95% CI, 1.06 to 2.92). We conclude that orally given HIF-PHIs are at least as efficacious as ESAs treatment to correct anemia short term in patients with CKD. In addition, HIF-PHIs improved iron metabolism and utilization in patients with CKD.

Treatment of Renal Anemia with Roxadustat: Advantages and Achievement

Background

Although renal anemia has attracted widespread attention, a large proportion of chronic kidney disease (CKD) patients with anemia still do not meet the hemoglobin (Hb) targets. The discovery of prolyl hydroxylase domain (PHD) enzymes as regulators of hypoxia-inducible factor (HIF)-dependent erythropoiesis has led to the development of novel therapeutic agents for renal anemia. Roxadustat, the first small-molecule HIF-PHD inhibitor, has completed the phase 3 trials. There are currently more than 15 phase 3 clinical trials worldwide assessing the efficacy and safety of roxadustat in CKD patients with anemia. This review will summarize recent findings of roxadustat in the treatment of renal anemia.

Summary

Although the administration of erythropoiesis-stimulating agents (ESAs) and iron supplementation are a well-established and highly effective therapeutic approach for renal anemia, there are several safety concerns. Current findings from phase 2 and 3 trials suggest that roxadustat is clinically effective and well tolerated. On the one hand, roxadustat could increase endogenous erythropoietin (EPO) levels within or near physiological range in a titratable manner by inducing HIF pathway activation transiently. On the other hand, roxadustat also improves iron metabolism by decreasing serum hepcidin and increasing intestinal iron absorption, which is beneficial to functional iron deficiency and absolute iron deficiency. More importantly, the erythropoietic response of roxadustat is independent of baseline inflammatory state of CKD patients. Thus, the discovery of roxadustat will revolutionize the treatment strategy for renal anemia.

Key Messages

Roxadustat is an emerging and promising therapeutic approach against anemia in CKD patients, which differs from those of conventional ESAs. Roxadustat corrects anemia of CKD patients through multiple pathways, beyond elevating EPO levels within physiological range, and also by handling iron metabolism (particularly decreasing the hepcidin levels). Furthermore, the Hb response of roxadustat is independent of the inflammatory microenvironment.

Novel Oral Iron Therapies for Iron Deficiency Anemia in Chronic Kidney Disease

Iron deficiency anemia (IDA) is a frequent complication of chronic kidney disease (CKD) and is associated with adverse outcomes in these patients. Patients with CKD and IDA remain largely undertreated. Conventional oral iron agents are insufficiently effective due to poor absorption and cause gastrointestinal side effects; thus, novel oral iron preparations are needed. This article covers current treatment guidelines for patients with anemia and CKD and clinical trial data for iron-repletion agents currently in use, as well as for novel oral iron therapies in development. Ferric citrate, a novel oral iron-repletion agent approved for patients with non-dialysis-dependent CKD and IDA, demonstrated improvements in hemoglobin levels and iron parameters, with good tolerability in patients with non-dialysis-dependent CKD. When used as a phosphate binder, ferric citrate also improves hemoglobin and iron parameters in dialysis-dependent CKD, but additional trials are needed to evaluate its efficacy as an iron-repletion agent in this setting. Other novel oral iron preparations in development for IDA in patients with CKD include ferric maltol, which is approved in Europe and the United States for IDA in adult patients, and sucrosomial iron, which has been evaluated in IDA associated with CKD and several other clinical settings.

Long-Term Efficacy and Safety of Molidustat for Anemia in Chronic Kidney Disease: DIALOGUE Extension Studies

BACKGROUND

Molidustat, a novel hypoxia-inducible factor-prolyl hydroxylase inhibitor, is being investigated for the treatment of anemia associated with chronic kidney disease (CKD). The efficacy and safety of molidustat were recently evaluated in three 16-week phase 2b studies. Here, we report the results of two long-term extension studies of molidustat.

METHODS

Both studies were parallel-group, open-label, multicenter studies of ≤36 months' duration, in patients with anemia due to CKD, and included an erythropoiesis-stimulating agent as active control. One study enrolled patients not receiving dialysis (n = 164), and the other enrolled patients receiving hemodialysis (n = 88). The primary efficacy variable for both studies was change in blood hemoglobin (Hb) level from baseline to each post-baseline visit, and safety outcomes included adverse events (AEs).

RESULTS

In patients not on dialysis, the mean ± SD Hb concentrations at baseline were 11.28 ± 0.55 g/dL for molidustat and 11.08 ± 0.51 g/dL for darbepoetin. The mean ± SD blood Hb concentrations throughout the study (defined as mean of each patient's overall study Hb levels) were 11.10 ± 0.508 and 10.98 ± 0.571 g/dL in patients treated with molidustat and darbepoetin, respectively. Similar proportions of patients reported at least one AE in the molidustat (85.6%) and darbepoetin (85.7%) groups. In patients on dialysis, mean ± SD Hb levels at baseline were 10.40 ± 0.70 and 10.52 ± 0.53 g/dL in the molidustat and epoetin groups, respectively. The mean ± SD blood Hb concentrations during the study were 10.37 ± 0.56 g/dL in the molidustat group and 10.52 ± 0.47 g/dL in the epoetin group. Proportions of patients who reported at least one AE were 91.2% in the molidustat group and 93.3% in the epoetin group.

CONCLUSIONS

Molidustat was well tolerated for up to 36 months and appears to be an effective alternative to darbepoetin and epoetin in the long-term management of anemia associated with CKD.

Recombinant human erythropoietin does not affect several microvascular parameters in well-trained cyclists

Recombinant human erythropoietin (rHuEPO) has been used as a performance-enhancing agent by athletes in a variety of sports. The resulting increase in hematocrit levels leads to increased blood viscosity and can affect blood flow, potentially increasing the athlete's risk of developing health complications. However, the actual effects of using rHuEPO on microvascular blood flow and post-occlusive reactive hyperemia are currently unknown. We therefore evaluated the effect of rHuEPO on the cutaneous microcirculation in well-trained cyclists using laser speckle contrast imaging (LSCI). This study was part of a randomized, double-blind, placebo-controlled, parallel trial designed to investigate the effects of rHuEPO in 47 well-trained adult cyclists (age 18-50 years). Subjects received a weekly dose of either rHuEPO or placebo for 8 weeks, and LSCI was performed at baseline, after a maximal exercise test in week 6, and before maximal exercise in week 8. Endpoints included basal blood flux, maximum post-occlusion reperfusion, and time to return to baseline. Despite an increase in hematocrit levels in the rHuEPO-treated group, we found no statistically significant difference in microvascular function measured between the rHuEPO-treated group and the placebo group. Our results suggest that the increased hematocrit levels in rHuEPO-treated well-trained cyclists are not associated with changes in microvascular blood flow or post-occlusive reactive hyperemia measured using LSCI.