Inhibition of prolyl hydroxylases increases erythropoietin production in ESRD

Explore the effect of HIF-PHI on blood pressure variation rate and anemia efficacy in maintenance hemodialysis patients

OBJECTIVE

This study aims to investigate the impact of hypoxia-inducing factor prolyl hydroxylase inhibitor (HIF-PHI), specifically Roxadustat, on blood pressure variability, blood pressure indices, hemoglobin, and other biochemical markers in maintenance hemodialysis (MHD) patients.

METHODS

In this retrospective, self-controlled study, regular hemodialysis and consistent use of Roxadustat for at least six months were conducted at the Hemodialysis Unit of the First Affiliated Hospital of Nanchang University between June 2019 and November 2022. The study involved MHD patients who had been using erythropoiesis-stimulating agents (ESAs) for at least six months prior to transitioning to Roxadustat. Blood pressure, routine blood data, biochemical parameters, and clinical data were collected before, during, and after dialysis over a 12-month period. Statistical comparisons were made of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and true variability in SBP (SBP-ARV), DBP (DBP-ARV), and MAP (MAP-ARV) in the patients before and after the transition to Roxadustat. Hemoglobin levels and daily antihypertensive drug dosage (DDD) were also analyzed.

RESULTS

A total of 54 MHD patients (32 males and 22 females) were included in the study. Primary diagnoses included chronic nephritis, hypertensive nephropathy, diabetic nephropathy, obstructive nephropathy, polycystic kidney disease, nephrotic syndrome, scleroderma-related kidney injury, and cases of unknown etiology. Repeated measures variance analysis indicated that blood pressure fluctuations during Roxadustat treatment were significantly smaller than during ESA treatment. Statistically significant differences were observed in SBP, DBP, and MAP before and after dialysis (P-values: 0.046, < 0.001, 0.028, and 0.014, respectively). Paired t-tests revealed a significant reduction in SBP-ARV and MAP-ARV before and during dialysis in the Roxadustat group (P = 0.0018, 0.008, and 0.006). Hemoglobin, erythrocyte count, and serum calcium were significantly higher in the Roxadustat group compared to ESA treatment (P = 0.013, 0.012, and 0.003, respectively). In the high SBP variability group, a higher proportion of males, increased hospitalization rates, older age, and a higher prevalence of diabetes were observed.

CONCLUSION

MHD patients treated with Roxadustat experienced fewer fluctuations in blood pressure compared to those treated with rHuEPO, and Roxadustat was more effective at increasing hemoglobin levels without compromising efficacy relative to ESAs.

CLINICAL TRIAL NUMBER

Not applicable.

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

ABSTRACT

Anemia of chronic disease (ACD) is the most frequent clinical issue in patients with chronic disease, ACD is usually secondary to chronic kidney disease (CKD), cancer, and chronic infection, which is associated with poor health outcomes, increased morbidity and mortality, and substantial economic costs. Current treatment options for ACD are very limited. The discovery of the hypoxia-inducible factor-prolyl hydroxylase (HIF-PHD) pathway made it possible to develop novel therapeutic agents (such as hypoxia-inducible factor-prolyl hydroxylase inhibitor, HIF-PHI) to treat ACD by stabilizing HIF and subsequently promoting endogenous erythropoietin (EPO) production and iron absorption and utilization. Thus, HIF-PHIs appear to open a new door for the treatment of ACD patients with a novel mechanism. Here, we comprehensively reviewed the latest advancements in the application of HIF-PHIs in ACD. Specifically, we highlighted the key features of HIF-PHIs on ACD, such as stimulation of endogenous EPO, handling iron metabolism, inflammation-independent, and prolonging lifespan of red blood cells. In conclusion, the success of HIF-PHIs in the treatment of ACD may expand the therapeutic opportunity for other types of anemia beyond renal anemia.

Highlights on U.S. FDA-approved halogen-containing drugs in 2024

This comprehensive review offers an update on the FDA-approved halogen-containing drugs in 2024. The agency approved a total of 50 drugs, including small molecules and macromolecules. Excitingly, 16 out of 50 are halogen-containing drugs, indicated to diagnose, mitigate and treat the various human diseases. Among halogens, fluorine and chlorine are highly prevalent in drug discovery and development. Therefore, the properties of fluorine and chlorine and their impact on the drug profile are briefly discussed. In addition, the specific role of halogens in these drugs has been discussed with the help of structure-activity relationships (SARs), co-crystal structures, and closely related literature precedents. This review also provides the additional information for each drug, such as trade name, active ingredients, route of administration, approval date, sponsors, indication, mode of action, major drug metabolizing enzyme(s), and route of elimination. We expect that the present review may garner the attention of drug discovery researchers and inspire them toward the potential applications of halogens to discover novel therapeutics in the future.

Anemia in diabetes mellitus: Pathogenetic aspects and the value of early erythropoietin therapy

Anemia is a frequent, yet increasingly recognized, comorbidity in diabetes mellitus (DM), with prevalence often driven by multifactorial mechanisms. Hematinic deficiencies, common in this population, may arise from associated comorbidities or medications, such as metformin, as well as other drugs commonly employed for DM-related conditions. Among contributing factors, diabetic kidney disease (DKD) plays a pivotal role, with anemia developing more frequently and being more pronounced in earlier stages, than in CKD of other causes. This enhanced susceptibility stems primarily from the combined impact of impaired renal oxygen sensing and deficient erythropoietin (EPO) production linked to tubulointerstitial fibrosis. Additional mechanisms comprise glomerular dysfunction, shortened erythrocyte lifespan, uremia-induced bone marrow suppression, and increased bleeding risk. DM is also recognized as a chronic low-grade inflammatory condition, with its inflammatory burden driving iron maldistribution, suppression of erythropoiesis, and resistance to EPO. The diagnostic approach of anemia in DM mirrors that in the general population. Addressing modifiable causes such as hematinic deficiencies, and other chronic conditions, such as DKD and bone marrow disorders, is paramount. In total, the underlying pathophysiology of anemia in DM primarily reflects a state of absolute or relative EPO deficiency and/or diminished bone marrow responsiveness, effectively corresponding to 'anemia of chronic disease. Early initiation of EPO therapy, even in DM patients without overt DKD, may mitigate disease progression and improve outcomes. Future research should focus on diabetes-specific strategies integrating optimal EPO use, potentially implementing targeted management of renal and inflammatory contributors to anemia.

Research progress of hypoxia-inducible factor-1α and zinc in the mechanism of diabetic kidney disease

Diabetic kidney disease is one of the common complications in diabetic patients and has gradually become an important pathogenic factor in chronic kidney disease. Therefore, studying the mechanisms of its occurrence and development is of great significance for the prevention and treatment of diabetic kidney disease. Some researchers have pointed out that there is a phenomenon of hypoxia in diabetic kidney tissue and believe that hypoxia-inducible factor-1α is closely related to the occurrence and progression of diabetic kidney disease. Additionally, the homeostasis of zinc plays a key role in the body's adaptation to hypoxic environments. However, the specific relationship among these three factors remains unclear. This article provides a detailed review of the multiple roles of hypoxia-inducible factor-1α in the pathogenesis of diabetic kidney disease, including: regulating angiogenesis, increasing the expression of erythropoietin, modulating oxidative stress through the PI3K/AKT and HIF-1α/HO-1 pathways, promoting inflammatory cell infiltration and the release of inflammatory factors to induce inflammatory responses, facilitating epithelial-mesenchymal transition, pathological angiogenesis, and promoting the release of fibrotic factors, ultimately leading to renal fibrosis. Furthermore, HIF-1α also participates in the occurrence and development of diabetic kidney disease through mechanisms such as regulating apoptosis, inducing mitochondrial autophagy, and vascular calcification. At the same time, this article clarifies the regulatory role of the trace element zinc on hypoxia-inducible factor-1α in diabetic kidney disease. This article provides references and insights for further research on the pathogenesis and progression of diabetic kidney disease.

Appropriate Use of Inpatient Erythropoiesis Stimulating Agents

Background: Anemia is a significant global public health issue, and is associated with lethargy, weakness, tiredness, and shortness of breath. Erythropoiesis stimulating agents (ESAs) are recombinant/synthetic erythropoietin and can increase hemoglobin (Hb) levels. There are increased risks of cardiovascular events and death associated with the use of ESAs when raising Hb levels above 12 g/dL. Methods: The objective was to assure safety and appropriate use of ESA. We performed a baseline assessment via a retrospective chart review, including patients who recently received an inpatient dose of an ESA within Mount Sinai Hospital (MSH) from November 1, 2015 (after MSH ESA guideline revision) to August 1, 2023. All adult patients who received an ESA (originator or biosimilar products) during hospitalization were included. Data collection was in reverse chronology, and the most recent dose administered to each unique patient was collected. Results: If an ESA dose was dispensed when the Hb was less than the upper limit of the target Hb for the specific indication, this was considered appropriate use. Based on data from June 15 to August 1, 2023 (~47 days of inpatient utilization), for the primary outcome, 169 out of 171 doses (98.8%) met the predefined criteria for appropriateness. One dose was dispensed when the Hb was 11.1 g/dL to a patient on renal replacement therapy, and one dose was dispensed when the Hb was 13.8 g/dL to a surgical patient who refused blood transfusions. Among secondary outcomes of interest, there was a difference in blood transfusions administered in critical versus non-critical care settings. Conclusion: Inpatient use of ESA at MSH was appropriate when looking at Hb targets. There are currently no formal order sets, service-line restrictions, or additional chairperson approvals needed at MSH. Despite this, there remained significant adherence to prevailing Hb targets, reflecting provider and pharmacy teams' knowledge and awareness of contemporary best practices.

Renal anemia: from relative insufficiency of EPO to imbalance of erythropoiesis and eryptosis

Chronic kidney disease has emerged as a major health issue both in China and worldwide. Renal anemia frequently occurs in patients with chronic kidney disease, and its severity and incidence rate increase as the disease progresses. Over the last 30 years, the administration of exogenous EPO and EPO stimulants has been employed to alleviate renal anemia, suggesting that a relative deficiency in EPO may be a primary cause. However, this approach has overshadowed other contributing factors, particularly eryptosis, which results from the reduced lifespan of red blood cells. Numerous studies reveal that there are nephrogenic and extrarenal EPO secretion indicating that an absolute deficiency of EPO is not always present in patients. Therefore, this paper speculates that renal anemia may arise when EPO-driven erythropoiesis fails to adequately compensate for aggravating eryptosis. Other factors including iron metabolism disorder, uremic toxin accumulation, inflammatory state, oxidative stress, and secondary hyperparathyroidism affect EPO reactivity bone marrow hematopoiesis and eryptosis, leading to an imbalance between red blood cell production and destruction, and cause anemia ultimately. More further studies on the pathogenesis and treatment of renal anemia would be expected to provide evidence to support our opinion.

The drug-specific properties of hypoxia-inducible factor-prolyl hydroxylase inhibitors in mice reveal a significant contribution of the kidney compared to the liver to erythropoietin induction

AIMS

Kidney disease often leads to anemia due to a defect in the renal production of the erythroid growth factor erythropoietin (EPO), which is produced under the positive regulation of hypoxia-inducible transcription factors (HIFs). Chemical compounds that inhibit HIF-prolyl hydroxylases (HIF-PHs), which suppress HIFs, have been developed to reactivate renal EPO production in renal anemia patients. Currently, multiple HIF-PH inhibitors, in addition to conventional recombinant EPO reagents, are used for renal anemia treatment. This study aimed to elucidate the therapeutic mechanisms and drug-specific properties of HIF-PH inhibitors.

METHODS AND KEY FINDINGS

Gene expression analyses and mass spectrometry revealed that HIF-PH inhibitors (daprodustat, enarodustat, molidustat, and vadadustat) alter Epo gene expression levels in the kidney and liver in a drug-specific manner, with different pharmacokinetics in the plasma and urine after oral administration to mice. The drug specificity revealed the dominant contribution of EPO induction in the kidneys rather than in the liver to plasma EPO levels after HIF-PH inhibitor administration. We also found that several HIF-PH inhibitors directly induce duodenal gene expression related to iron intake, while these drugs indirectly suppress hepatic hepcidin expression to mobilize stored iron for hemoglobin synthesis through induction of the EPO-erythroferrone axis.

SIGNIFICANCE

Renal EPO induction is the major target of HIF-PH inhibitors for their therapeutic effects on erythropoiesis. Additionally, the drug-specific properties of HIF-PH inhibitors in EPO induction and iron metabolism have been shown in mice, providing useful information for selecting the proper HIF-PH inhibitor for each renal anemia patient.

Discovery of DS44470011: An oral hypoxia-inducible factor prolyl hydroxylase inhibitor for the treatment of renal anemia

Inhibition of the hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) represents a promising strategy for discovering next-generation treatments for renal anemia. We identified a pyrimidine core with HIF-PHD inhibitory activity based on scaffold hopping of FG-2216 using crystal structures of HIF-PHD2 in complex with compound. By optimizing the substituents at the 2- and 6- positions of the pyrimidine core, we discovered DS44470011, which improves the effectiveness of erythropoietin (EPO) release in cells. Oral administration of DS44470011 to cynomolgus monkeys increased plasma EPO levels.

Anaemia in CKD-treatment standard

Anaemia is one of the most common complications of chronic kidney disease (CKD), having a significant impact on quality of life, and is also associated with a number of adverse clinical outcomes. Its pathogenesis is multifactorial, caused largely by an inadequate production of erythropoietin from the diseased kidneys, with iron deficiency, inflammation, shortened red cell lifespan and enhanced blood loss also being contributory factors. The management of this condition was transformed in the late 1980s by the advent of recombinant human erythropoietin (epoetin), and treatment paradigms have developed over the last three decades, largely focusing on a combination of epoetin or its analogues (erythropoiesis-stimulating agents; ESAs) along with iron supplementation, often administered intravenously due to increased hepcidin levels limiting iron absorption from the gut. Indeed, in patients with early CKD and iron deficiency, iron per se may be sufficient to improve the anaemia, delaying the need for ESA therapy. Other causes of anaemia should be excluded and corrected (if possible) before resorting to treatment with ESAs and iron. More recently, the hypoxia-inducible factor-prolyl hydroxylase inhibitors have entered the therapeutic arena; these are orally active agents that upregulate endogenous erythropoietin production as well as a number of iron-regulatory genes which may also enhance erythropoiesis. The latter drugs are highly efficacious, and may have advantages in inflammatory conditions causing resistance to conventional ESA therapy, but concerns exist regarding their safety, particularly in the longer term. This article reviews the current standards of treatment, as well as recent novel developments in the management of anaemia in CKD.

Iron Metabolism and Inflammatory Mediators in Patients with Renal Dysfunction

Chronic kidney disease (CKD) affects around 850 million people worldwide, posing significant challenges in healthcare due to complications like renal anemia, end-stage kidney disease, and cardiovascular diseases. This review focuses on the intricate interplay between iron metabolism, inflammation, and renal dysfunction in CKD. Renal anemia, prevalent in CKD, arises primarily from diminished erythropoietin (EPO) production and iron dysregulation, which worsens with disease progression. Functional and absolute iron deficiencies due to impaired absorption and chronic inflammation are key factors exacerbating erythropoiesis. A notable aspect of CKD is the accumulation of uremic toxins, such as indoxyl sulfate (IS), which hinder iron metabolism and worsen anemia. These toxins directly affect renal EPO synthesis and contribute to renal hypoxia, thus playing a critical role in the pathophysiology of renal anemia. Inflammatory cytokines, especially TNF-α and IL-6, further exacerbate CKD progression and disrupt iron homeostasis, thereby influencing anemia severity. Treatment approaches have evolved to address both iron and EPO deficiencies, with emerging therapies targeting hepcidin and employing hypoxia-inducible factor (HIF) stabilizers showing potential. This review underscores the importance of integrated treatment strategies in CKD, focusing on the complex relationship between iron metabolism, inflammation, and renal dysfunction to improve patient outcomes.

Beyond the horizon: emerging therapeutic approaches in myelodysplastic neoplasms

Management of myelodysplastic neoplasms (MDS) requires a personalized approach, with a focus on improving quality of life and extending lifespan. The International Prognostic Scoring System-Revised and the molecular International Prognostic Scoring System are key tools for risk stratification and management of MDS. They provide a framework for predicting survival and the risk of transformation to acute myeloid leukemia. However, a major challenge in MDS management remains the limited therapeutic options available, especially after the failure of first-line therapies. In lower-risk MDS, the failure of erythropoietin-stimulating agents often leaves few alternatives, although in higher-risk MDS, the prognosis after hypomethylating agent failure is dismal. This highlights the urgent need for novel, more personalized therapeutic approaches. In this review, we discuss emerging novel therapeutic approaches in the treatment of MDS. Several new therapeutic targets are currently being evaluated, offering hope for improved management of MDS in the future.

Comparison of outcomes on hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) in anaemia associated with chronic kidney disease: network meta-analyses in dialysis and non-dialysis dependent populations

Background

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are oral alternatives to current standard-of-care treatments for anaemia in chronic kidney disease (CKD). We conducted network meta-analyses to indirectly compare clinical outcomes for three HIF-PHIs in dialysis and non-dialysis populations with anaemia in CKD.

Methods

The evidence base comprised phase III, randomised, controlled trials evaluating daprodustat, roxadustat, or vadadustat. Three outcomes were evaluated: efficacy [change from baseline in haemoglobin (Hgb)], cardiovascular safety [time to first major adverse cardiovascular event (MACE)] and quality of life [change from baseline in 36-Item Short Form Health Survey (SF-36) Vitality score]. Analyses were performed separately for all patients and for erythropoiesis-stimulating agent (ESA) non-users at baseline (non-dialysis population) or prevalent dialysis patients (dialysis population). Bayesian Markov Chain Monte Carlo methods with non-informative priors were used to estimate the posterior probability distribution and generate pairwise treatment comparisons. Point estimates (medians of posterior distributions) and 95% credible intervals (CrI) were calculated.

Results

Seventeen trials were included. In non-dialysis patients, there were no clinically meaningful differences between the three HIF-PHIs with respect to Hgb change from baseline [all patients analysis (total n = 7907): daprodustat vs. roxadustat, 0.09 g/dL (95% CrI -0.14, 0.31); daprodustat vs. vadadustat, 0.09 g/dL (-0.04, 0.21); roxadustat vs. vadadustat, 0.00 g/dL (-0.22, 0.22)] or risk of MACE [all patients analysis (total n = 7959): daprodustat vs. roxadustat, hazard ratio (HR) 1.16 (95% CrI 0.76, 1.77); daprodustat vs. vadadustat, 0.88 (0.71, 1.09); roxadustat vs. vadadustat, 0.76 (0.50, 1.16)]. Daprodustat showed a greater increase in SF-36 Vitality compared with roxadustat [total n = 4880; treatment difference 4.70 points (95% CrI 0.08, 9.31)]. In dialysis patients, Hgb change from baseline was higher with daprodustat and roxadustat compared with vadadustat [all patients analysis (total n = 11 124): daprodustat, 0.34 g/dL (0.22, 0.45); roxadustat, 0.38 g/dL (0.27, 0.49)], while there were no clinically meaningful differences in the risk of MACE between the HIF-PHIs [all patients analysis (total n = 12 320): daprodustat vs. roxadustat, HR 0.89 (0.73, 1.08); daprodustat vs. vadadustat, HR 0.99 (0.82, 1.21); roxadustat vs. vadadustat, HR 1.12 (0.92, 1.37)]. Results were similar in analyses of ESA non-users and prevalent dialysis patients.

Conclusions

In the setting of anaemia in CKD, indirect treatment comparisons suggest that daprodustat, roxadustat, and vadadustat are broadly clinically comparable in terms of efficacy and cardiovascular safety (precision was low for the latter), while daprodustat may be associated with reduction in fatigue to a greater extent than roxadustat.

Investigation of the human metabolism and disposition of the prolyl hydrolase inhibitor daprodustat using IV microtracer with Entero-Test bile string

Daprodustat is an oral small molecule hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor (PHI) approved in Japan and the United States for the treatment of anemia associated with chronic kidney disease. This phase 1, nonrandomized, 2-period, crossover study in 6 healthy men characterized and quantified the metabolites generated after a microtracer IV infusion of 50 μg (125 nCi) [14 C]-daprodustat administered concomitantly with a nonradiolabeled therapeutic dose of a 6-mg daprodustat tablet, followed by a single oral solution dose of 25 mg (62.5 μCi) [14 C]-daprodustat. High-performance liquid chromatography (HPLC) coupled with radioactivity detection (TopCount or AMS) and HPLC-tandem mass spectrometry (HPLC-MSn ) were used for quantitative measurement and structural identification of radioactive metabolites in plasma, urine, feces, and bile. Following oral administration of [14 C]-daprodustat, unchanged daprodustat was the principal circulating drug-related component, accounting for 40% of plasma radioactivity. Predominant oxidative metabolites M2, M3, M4, and M13 individually represented 6-8% of the plasma radioactivity and together accounted for the majority of radioactivity in urine and feces (53% in both matrices; 12% and 41% of dose, respectively). Unchanged daprodustat was not detected in urine and was only 0.7% of total radioactivity in feces (<0.5% of dose), with the remainder of the dose accounted for by oxidative metabolites. The radio-metabolic profile of duodenal bile following IV infusion of [14 C]-daprodustat was similar to that observed in feces after oral administration. The data suggested that oral daprodustat was extensively absorbed, cleared exclusively by oxidative metabolism, and eliminated via hepatobiliary (primary) and urinary (secondary) excretion.

Poor recognition and undertreatment of anemia in patients with chronic kidney disease managed in primary care

BACKGROUND

Anemia is a common complication of chronic kidney disease (CKD), but limited awareness and treatment options may hinder its management among CKD patients followed in primary care.

METHODS

We evaluated adults with CKD stages 3-5 attending primary care in Stockholm, Sweden, 2012-2018. We assessed the incidence of anemia, clinical reactions, and association with subsequent major adverse cardiovascular events (MACE) and death.

RESULTS

We identified 45,637 patients with CKD stages 3-5 free from anemia (mean age 78 years; 64% females; 79% CKD stage 3b). During a median follow-up of 2.4 years, 26% of patients developed anemia, and 10.4% developed severe anemia (hemoglobin <10 g/dL). Within 6 months from the anemia event, iron tests were infrequent; ferritin and transferrin saturation were tested in 27% and 11% of anemia cases, respectively, and 49% and 24% of severe anemia cases. Few patients were recognized with a clinical diagnosis (15% of anemia cases; 68% of severe anemias). Only 19% of patients with anemia received treatment, primarily iron (10%) and blood transfusions (7%); erythropoietin-stimulating agent use was anecdotal (∼1%). Treatment rates for severe anemia were higher, but 43% of patients still failed to receive treatment. Developing anemia was associated with a higher risk of MACE and death.

CONCLUSION

Anemia was common and associated with adverse outcomes among patients with CKD stages 3-5 managed in primary care. Iron stores were infrequently tested, and a large proportion of patients with anemia remained untreated/under-recognized.

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.

Hypoxia and renal fibrosis

Renal fibrosis is the final stage of most progressive kidney diseases. Chronic kidney disease (CKD) is associated with high comorbidity and mortality. Thus, preventing fibrosis and thereby preserving kidney function increases the quality of life and prolongs the survival of patients with CKD. Many processes such as inflammation or metabolic stress modulate the progression of kidney fibrosis. Hypoxia has also been implicated in the pathogenesis of renal fibrosis, and oxygen sensing in the kidney is of outstanding importance for the body. The dysregulation of oxygen sensing in the diseased kidney is best exemplified by the loss of stimulation of erythropoietin production from interstitial cells in the fibrotic kidney despite anemia. Furthermore, hypoxia is present in acute or chronic kidney diseases and may affect all cell types present in the kidney including tubular and glomerular cells as well as resident immune cells. Pro- and antifibrotic effects of the transcription factors hypoxia-inducible factors 1 and 2 have been described in a plethora of animal models of acute and chronic kidney diseases, but recent advances in sequencing technologies now allow for novel and deeper insights into the role of hypoxia and its cell type-specific effects on the progression of renal fibrosis, especially in humans. Here, we review existing literature on how hypoxia impacts the development and progression of renal fibrosis.

Hydrophobic constituents of Polygonum multiflorum roots promote renal erythropoietin expression in healthy mice

The roots of Polygonum multiflorum Thunberg (Polygonaceae) are used as a crude drug Kashu that is considered to improve blood deficiency based on a Kampo concept. Kashu has been included in Kampo formulas, such as Tokiinshi, which is used to treat eczema and dermatitis with itchiness by inhibiting inflammation and facilitating blood circulation in the skin. However, the effects of P. multiflorum roots on erythropoiesis are unclear. Previously, we isolated six phenolic constituents from an ethyl acetate (EtOAc)-soluble fraction of P. multiflorum root extract and identified them as (E)-2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucopyranoside [(E)-THSG], emodin, emodin-8-O-β-D-glucopyranoside, physcion, physcion-8-O-β-D-glucopyranoside, and catechin. To examine whether P. multiflorum roots facilitate erythropoiesis, the EtOAc-soluble fraction was orally administered to healthy ICR mice. When compared with mice fed a standard diet alone (Controls), the mice fed a diet including the EtOAc-soluble fraction exhibited significantly higher serum erythropoietin (Epo) levels. The renal Epo mRNA levels in EtOAc-soluble fraction-administered mice were significantly higher than those in the control mice. Then, we administered roxadustat, which is a drug to treat the patient suffering with renal anemia by specifically inhibiting hypoxia-inducible factor prolyl hydroxylases. Roxadustat slightly increased renal Epo mRNA levels in healthy mice. Administration of (E)-THSG, a major constituent, significantly increased serum Epo levels. It is likely that (E)-THSG may facilitate the process to convert inactive renal Epo-producing cells to active Epo-producing cells. Collectively, it is implied that (E)-THSG in the EtOAc-soluble fraction of P. multiflorum roots may primarily improve blood deficiency of Kampo concept by promoting erythropoiesis.

Anemia Treatment, Hemoglobin Variability, and Clinical Events in Patients With Nondialysis-Dependent CKD in Japan

Key Points

This large, contemporary study reports the management of anemia in a real-world cohort of patients with nondialysis-dependent CKD from multifaceted aspects. This study highlights the suboptimal and heterogeneous treatment of anemia in clinical practice. The findings also underscore the importance of maintaining a stable hemoglobin concentration within the target range to reduce the risk of mortality and morbidity.

Background

Anemia management in patients with nondialysis-dependent CKD has attracted attention with the introduction of novel therapeutic agents; however, few studies have provided comprehensive epidemiologic information.

Methods

A retrospective cohort study was conducted in adult patients with stage ≥3a nondialysis-dependent CKD and hemoglobin (Hb) <11 g/dl (January 2013–November 2021; N =26,626) to assess longitudinal treatment patterns, Hb, and iron parameters (ferritin and transferrin saturation) for anemia management. Time-dependent Cox proportional hazard models were applied to assess the risk of clinical events, including death, cardiovascular events, dialysis introduction, and red blood cell transfusion, associated with temporal fluctuation patterns of Hb levels.

Results

The cumulative incidence of anemia treatment initiation within 12 months was 37.1%, including erythropoiesis-stimulating agents 26.5%, iron oral 16.8%, iron intravenous 5.1%, and hypoxia-inducible factor prolyl hydroxylase inhibitor 0.2%. The mean (±SD) Hb levels were improved from 9.9±1.2 to 10.9±1.6 g/dl at 12 months. Despite erythropoiesis-stimulating agents or hypoxia-inducible factor prolyl hydroxylase inhibitor therapy, 30.1% of patients remained Hb <10 g/dl. The risks of premature death, cardiovascular events, dialysis introduction, and red blood cell transfusion were significantly higher in groups with consistently low Hb or low-amplitude Hb fluctuation around the lower limit of target Hb range than in patients with target Hb range (P < 0.05). Similarly, significantly higher risks for dialysis introduction and red blood cell transfusion were associated with high-amplitude Hb fluctuation across target Hb range were observed.

Conclusions

The findings underscore the importance of stable Hb control within the target range to reduce the mortality and morbidity risks in patients with nondialysis-dependent CKD while highlighting the suboptimal and heterogeneous treatment of anemia in clinical practice.

Iron Parameters in Patients Treated with Roxadustat for Anemia of Chronic Kidney Disease

Roxadustat is a novel agent with a distinct mechanism of action compared to erythropoiesis-stimulating agents (ESAs) and a potentially different combination of effects on iron parameters. This narrative review describes the effects of roxadustat on iron parameters and on hemoglobin levels in the context of iron supplementation in patients with anemia of non-dialysis-dependent (NDD) or dialysis-dependent (DD) chronic kidney disease (CKD). Roxadustat use was associated with a greater reduction in serum ferritin levels than seen with ESAs and an increase in serum iron levels compared to a decrease with ESAs. Decreases in transferrin saturation in patients treated with roxadustat were relatively small and, in the case of patients with NDD CKD, not observed by Week 52. These changes reflect the concomitant increases in both serum iron and total iron-binding capacity. Compared to placebo and an ESA, roxadustat improved iron availability and increased erythropoiesis while requiring less intravenous iron use. Hepcidin levels generally decreased in patients who received roxadustat compared to baseline values in all CKD populations; these decreases appear to be more robust with roxadustat than with an ESA or placebo. The mechanisms behind the effects of roxadustat and ESAs on iron availability and stores and erythropoiesis appear to differ and should be considered holistically when treating anemia of CKD.

Managing Anemia: Point of Convergence for Heart Failure and Chronic Kidney Disease?

The pathologic triangle formed by chronic heart failure (HF), chronic kidney disease (CKD), and anemia carries high morbidity and mortality rates and decreases quality of life. Anemia represents a common condition in patients with advanced HF and CKD, with a total prevalence in cardiorenal syndrome (CRS) ranging from 5% to 55%. Searching for a pragmatic approach for these patients with guided and disease-specific recommendations beyond just targeted hemoglobin therapeutic behavior represents the core of research for ongoing clinical trials. It is well known that the prevalence of anemia increases with the advancement of CKD and HF. The physiopathological mechanisms of anemia, such as the reduction of endogenous erythropoietin and the decrease in oxygen transport, are leading to tissue hypoxia, peripheral vasodilation, stimulating neurohormonal activity, and maintenance of the progressive renal and cardiac dysfunction. Given the challenges with the treatment options for patients with cardiorenal anemia syndrome (CRSA), new therapeutic agents such as hypoxia-inducible factor-prolyl hydroxylase domain inhibitors (HIF-PH) or hepcidin antagonists are emerging in the light of recent research. This review summarizes the potential therapeutic tools for anemia therapy in the cardiorenal population.

Regulation of Erythropoiesis by the Hypoxia-Inducible Factor Pathway: Effects of Genetic and Pharmacological Perturbations

Red blood cells transport O₂ from the lungs to body tissues. Hypoxia stimulates kidney cells to secrete erythropoietin (EPO), which increases red cell mass. Hypoxia-inducible factors (HIFs) mediate EPO gene transcriptional activation. HIF-α subunits are subject to O₂-dependent prolyl hydroxylation and then bound by the von Hippel-Lindau protein (VHL), which triggers their ubiquitination and proteasomal degradation. Mutations in the genes encoding EPO, EPO receptor, HIF-2α, prolyl hydroxylase domain protein 2 (PHD2), or VHL cause familial erythrocytosis. In addition to O₂, α-ketoglutarate is a substrate for PHD2, and analogs of α-ketoglutarate inhibit hydroxylase activity. In phase III clinical trials evaluating the treatment of anemia in chronic kidney disease, HIF prolyl hydroxylase inhibitors were as efficacious as darbepoetin alfa in stimulating erythropoiesis. However, safety concerns have arisen that are focused on thromboembolism, which is also a phenotypic manifestation of VHL or HIF-2α mutation, suggesting that these events are on-target effects of HIF prolyl hydroxylase inhibitors.

VHL-recruiting PROTAC attenuates renal fibrosis and preserves renal function via simultaneous degradation of Smad3 and stabilization of HIF-2α

BACKGROUND

Renal fibrosis is the pathological foundation of various chronic kidney diseases progressing to end stage renal failure. However, there are currently no nephroprotective drugs targeted to the fibrotic process in clinical practice. Proteolytic targeting chimeras (PROTACs), which reversibly degrade target proteins through the ubiquitin-proteasome pathway, is a novel therapeutic modality. Smad3 is a key pathogenic factor in fibrogenesis while HIF-2α exhibits prominent renal protective effects, which is the natural substrate of von Hippel-Lindau (VHL) E3 Ligase. We hypothesied the construction of VHL-recruiting, Smad3-targeting PROTAC might combine the effects of Smad3 degradation and HIF-2α stabilization, which not only improving the clinical efficacy of PROTAC but also avoiding its potential off-target effects, could greatly improve the possibility of its translation into clinical drugs.

METHODS

By joining the Smad3-binding small molecule compound (SMC) to VHL-binding SMC with a linker, we designed and synthesized a Smad3-targeting, VHL-based PROTAC. The effects of this PROTAC on targeted proteins were verified both in vitro and in vivo. The toxicity and pharmacokinetic (PK) evaluations were conducted with both male and female mice. The renal protection effects and mechanism of PROTAC were evaluated in unilateral ureteral obstruction (UUO) and 5/6 subtotal nephrectomy (5/6Nx) mouse model.

RESULTS

By optimizing the linker and the Smad3-binding SMC, we got a stable and high efficient PROTAC which simultaneously degraded Smad3 and stabilized HIF-2α both in vivo and in vitro. The acute toxicity evaluation showed a pretty large therapeutic window of the PROTAC. The prominent renal protection effects and its underlying mechanism including anti-fibrosis and anti-inflammatory, improving renal anemia and promoting kidney repair, had all been verified in UUO and 5/6Nx mouse model.

CONCLUSION

By accurate combination of PROTAC targeted protein and E3 ligase, we got a Smad3-targeting, VHL-recruting PROTAC which caused Smad3 degradation and HIF-2α stabilization effects simultaneously, and led to the strong renal function protection effects.

Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Significance: The disturbance of the hypoxia response system is closely related to human diseases, because it is essential for the maintenance of homeostasis. Given the significant role of the hypoxia response system in human health, therapeutic applications targeting prolyl hydroxylase-hypoxia-inducible factor (HIF) signaling have been attempted. Thus, systemically reviewing the hypoxia response-based therapeutic strategies is of great significance. Recent Advances: Disturbance of the hypoxia response is a characteristic feature of various diseases. Targeting the hypoxia response system is, thus, a promising therapeutic strategy. Interestingly, several compounds and drugs are currently under clinical trials, and some have already been approved for use in the treatment of certain human diseases. Critical Issues: We summarize the molecular mechanisms of the hypoxia response system and address the potential therapeutic implications in kidney diseases. Given that the effects of hypoxia response in kidney diseases are likely to depend on the pathological context, specific cell types, and the differences in the activation pattern of HIF isoforms, the precise application is critical for the treatment of kidney diseases. Although HIF-PHIs (HIF-PHD inhibitors) have been proven to be effective and well tolerated in chronic kidney disease patients with anemia, the potential on-target consequence of HIF activation and some outstanding questions warrant further consideration. Future Direction: The mechanism of the hypoxia response system disturbance remains unclear. Elucidation of the molecular mechanism of hypoxia response and its precise effects on kidney diseases warrants clarification. Considering the complexity of the hypoxia response system and multiple biological processes controlled by HIF signaling, the development of more specific inhibitors is highly warranted. Antioxid. Redox Signal. 37, 936-955.

The hypoxia-inducible factor-α prolyl hydroxylase inhibitor FG4592 ameliorates renal fibrosis by inducing the H3K9 demethylase JMJD1A

The transcription factors hypoxia-inducible factor-1α and -2α (HIF-1α/2α) are the major regulators of the cellular response to hypoxia and play a key role in renal fibrosis associated with acute and chronic kidney disease. Jumonji domain-containing 1a (JMJD1A), a histone H3 lysine 9 (H3K9) demethylase, is reported to be an important target gene of HIF-α. However, whether JMJD1A and H3K9 methylation status play a role in renal fibrosis is unclear. Here, we investigated the involvement of HIF-α, JMJD1A, and monomethylated/dimethylated H3K9 (H3K9me1/H3K9me2) levels in unilateral ureteral obstruction (UUO)-induced renal fibrosis in mice. Intraperitoneal administration of FG4592, an inhibitor of HIF-α prolyl hydroxylase, which controls HIF-α protein stability, significantly attenuated renal fibrosis on days 3 and 7 following UUO. FG4592 concomitantly increased JMJD1A expression, decreased H3K9me1/me2 levels, reduced profibrotic gene expression, and increased erythropoietin expression in renal tissues of UUO mice. The beneficial effects of FG4592 on renal fibrosis were inhibited by the administration of JMJD1A-specific siRNA to mice immediately following UUO. Incubation of normal rat kidney-49F and/or -52E cells with transforming growth factor-β1 (TGF-β1) in vitro resulted in upregulated expression of α-smooth muscle actin and H3K9me1/me2, and these effects were inhibited by cotreatment with FG4592. In contrast, FG4592 treatment further enhanced the TGF-β1-stimulated upregulation of JMJD1A but had no effect on TGF-β1-stimulated expression of the H3K9 methyltransferase euchromatic histone-lysine N-methyltransferase 2. Collectively, these findings establish a crucial role for the HIF-α1/2-JMJD1A-H3K9me1/me2 regulatory axis in the therapeutic effect of FG4592 in renal fibrosis.NEW & NOTEWORTHY Using a mouse model of renal fibrosis and transforming growth factor-β1-stimulated rat cell lines, we show that treatment with FG4592, an inhibitor of hypoxia-inducible factor-1α and -2α (HIF-1α/2α) prolyl hydroxylase decreases renal fibrosis and concomitantly reduces methylated lysine 9 of histone H3 (H3K9) levels via upregulation of Jumonji domain-containing 1a (JMJD1A). The results identify a novel role for the HIF-1α/2α-JMJD1A-H3K9 regulatory axis in suppressing renal fibrosis.

Evolving Strategies in the Treatment of Anaemia in Chronic Kidney Disease: The HIF-Prolyl Hydroxylase Inhibitors

Chronic kidney disease (CKD) affects approximately 10% of the worldwide population; anaemia is a frequent complication. Inadequate erythropoietin production and absolute or functional iron deficiency are the major causes. Accordingly, the current treatment is based on iron and erythropoiesis stimulating agents (ESAs). Available therapy has dramatically improved the management of anaemia and the quality of life. However, safety concerns were raised over ESA use, especially when aiming to reach near-to-normal haemoglobin levels with high doses. Moreover, many patients show hypo-responsiveness to ESA. Hypoxia-inducible factor (HIF) prolyl hydroxylase domain (PHD) inhibitors (HIF-PHIs) were developed for the oral treatment of anaemia in CKD to overcome these concerns. They simulate the body's exposure to moderate hypoxia, stimulating the production of endogenous erythropoietin. Some molecules are already approved for clinical use in some countries. Data from clinical trials showed non-inferiority in anaemia correction compared to ESA or superiority for placebo. Hypoxia-inducible factor-prolyl hydroxylase domain inhibitors may also have additional advantages in inflamed patients, improving iron utilisation and mobilisation and decreasing LDL-cholesterol. Overall, non-inferiority was also shown in major cardiovascular events, except for one molecule in the non-dialysis population. This was an unexpected finding, considering the lower erythropoietin levels reached using these drugs due to their peculiar mechanism of action. More data and longer follow-ups are necessary to better clarifying safety issues and further investigate the variety of pathways activated by HIF, which could have either positive or negative effects and could differentiate HIF-PHIs from ESAs.

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

Anemia is a common complication of chronic kidney disease; it is mainly treated with erythropoiesis-stimulating agents (ESAs) and iron. Experimental studies extensively investigated the mechanisms involved in the body's response to hypoxia and led to the discovery of the hypoxia-inducible factor (HIF) pathway and the enzymes regulating its function. HIF-prolyl-hydroxyl domain (PHD) inhibitors are a new class of oral drugs developed to treat anemia in chronic kidney disease. By inhibiting the function of PHD enzymes, they mimic the exposure to moderate hypoxia and stimulate the production of endogenous erythropoietin and very likely increase iron availability. Some data also suggest that their efficacy and, consequently, dose needs are less influenced by inflammation than ESAs. Overall, data from phases 2 and 3 clinical development showed efficacy in anemia correction and maintenance for all of the class molecules compared with placebo (superiority) or erythropoiesis-stimulating agents (noninferiority). Three molecules, roxadustat, vadadustat, and daprodustat, underwent extensive clinical investigation to assess their safety on hard cardiovascular end points, mortality, and special interest events (including cancer and thrombosis). Aside from vadadustat in the nondialysis population, at the prespecified primary analyses, all three molecules met the noninferiority margin for the risk of major cardiovascular events compared with erythropoiesis-stimulating agents or placebo. The reason for this discrepancy is difficult to explain. Other safety signals came from secondary analyses of some of the other randomized clinical trials, including a higher incidence of thrombosis. A more extensive clinical experience with post-marketing data on hard safety issues is needed to define better when and how to use HIF-PHD inhibitors compared with already available ESAs.

Toward evaluation of multiresolution cortical thickness estimation with FreeSurfer, MaCRUISE, and BrainSuite

Advances in Magnetic Resonance Imaging hardware and methodologies allow for promoting the cortical morphometry with submillimeter spatial resolution. In this paper, we generated 3D self-enhanced high-resolution (HR) MRI imaging, by adapting 1 deep learning architecture, and 3 standard pipelines, FreeSurfer, MaCRUISE, and BrainSuite, have been collectively employed to evaluate the cortical thickness. We systematically investigated the differences in cortical thickness estimation for MRI sequences at multiresolution homologously originated from the native image. It has been revealed that there systematically exhibited the preferences in determining both inner and outer cortical surfaces at higher resolution, yielding most deeper cortical surface placements toward GM/WM or GM/CSF boundaries, which directs a consistent reduction tendency of mean cortical thickness estimation; on the contrary, the lower resolution data will most probably provide a more coarse and rough evaluation in cortical surface reconstruction, resulting in a relatively thicker estimation. Although the differences of cortical thickness estimation at the diverse spatial resolution varied with one another, almost all led to roughly one-sixth to one-fifth significant reduction across the entire brain at the HR, independent to the pipelines we applied, which emphasizes on generally coherent improved accuracy in a data-independent manner and endeavors to cost-efficiency with quantitative opportunities.

Hypoxia-inducible factor stabilisers for the anaemia of chronic kidney disease

BACKGROUND

Anaemia occurs in chronic kidney disease (CKD) and is more prevalent with lower levels of kidney function. Anaemia in CKD is associated with death related to cardiovascular (CV) disease and infection. Established treatments include erythropoiesis-stimulating agents (ESAs), iron supplementation and blood transfusions. Oral hypoxia-inducible factors (HIF) stabilisers are now available to manage anaemia in people with CKD.

OBJECTIVES

We aimed to assess the benefits and potential harms of HIF stabilisers for the management of anaemia in people with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 22 November 2021 through contact with the Information Specialist using search terms relevant to our review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised and quasi-randomised studies evaluating hypoxia-inducible factors stabilisers compared to placebo, standard care, ESAs or iron supplementation in people with CKD were included.

DATA COLLECTION AND ANALYSIS

Five authors independently extracted data and assessed the risk of bias. Treatment estimates were summarised using random effects pair-wise meta-analysis and expressed as a relative risk (RR) or mean difference (MD), with a corresponding 95% confidence interval (CI). Evidence certainty was assessed using GRADE.

MAIN RESULTS

We included 51 studies randomising 30,994 adults. These studies compared HIF stabilisers to either placebo or an ESA. Compared to placebo, HIF stabiliser therapy had uncertain effects on CV death (10 studies, 1114 participants): RR 3.68, 95% CI 0.19 to 70.21; very low certainty evidence), and nonfatal myocardial infarction (MI) (3 studies, 822 participants): RR 1.29, 95% CI 0.31 to 5.36; I² = 0%; very low certainty evidence), probably decreases the proportion of patients requiring blood transfusion (8 studies, 4329 participants): RR 0.51, 95% CI 0.44 to 0.60; I² = 0%; moderate certainty evidence), and increases the proportion of patients reaching the target haemoglobin (Hb) (10 studies, 5102 participants): RR 8.36, 95% CI 6.42 to 10.89; I² = 37%; moderate certainty evidence). Compared to ESAs, HIF stabiliser therapy may make little or no difference to CV death (17 studies, 10,340 participants): RR 1.05, 95% CI 0.88 to 1.26; I² = 0%; low certainty evidence), nonfatal MI (7 studies, 7765 participants): RR 0.91, 95% CI 0.76 to 1.10; I² = 0%; low certainty evidence), and nonfatal stroke (5 studies, 7285 participants): RR 1.06, 95% CI 0.71 to 1.56; I² = 8%; low certainty evidence), and had uncertain effects on fatigue (2 studies, 3471 participants): RR 0.80, 95% CI 0.56 to 1.16; I² = 0%; very low certainty evidence). HIF stabiliser therapy probably decreased the proportion of patients requiring blood transfusion (11 studies, 10,786 participants): RR 0.87, 95% CI 0.76 to 1.00; I² = 25%; moderate certainty evidence), but may make little or no difference on the proportion of patients reaching the target Hb (14 studies, 4601 participants): RR 1.00, 95% CI 0.93 to 1.07; I² = 70%; low certainty evidence), compared to ESA. The effect of HIF stabilisers on hospitalisation for heart failure, peripheral arterial events, loss of unassisted dialysis vascular access patency, access intervention, cancer, infection, pulmonary hypertension and diabetic nephropathy was uncertain. None of the included studies reported life participation. Adverse events were rarely and inconsistently reported.

AUTHORS' CONCLUSIONS

HIF stabiliser management of anaemia had uncertain effects on CV death, fatigue, death (any cause), CV outcomes, and kidney failure compared to placebo or ESAs. Compared to placebo or ESAs, HIF stabiliser management of anaemia probably decreased the proportion of patients requiring blood transfusions, and probably increased the proportion of patients reaching the target Hb when compared to placebo.

Hypoxia-inducible factor prolyl hydroxylase inhibitors for anaemia in maintenance dialysis: a meta-analysis

BACKGROUND

Anaemia is a common complication of end-stage renal disease (ESRD) that relies on dialysis. Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHI) is a new class of small-molecule oral drugs for the treatment of anaemia in chronic kidney disease. They demonstrate several advantages over traditional exogenous erythropoietin (EPO). We conducted a meta-analysis of studies that compared the efficacy of HIF-PHI in erythropoiesis and iron metabolism, and its safety with EPO in maintenance dialysis patients.

METHODS

A sensitive search strategy in the PubMed, EMBASE and Cochrane databases identified all citations for randomised controlled trials (RCTs) comparing HIF-PHI agents with EPO/placebo through December 2021.

RESULTS

Fourteen RCTs were identified, which included 2738 patients. No statistical difference was found in haemoglobin increase (p = 0.37) between HIF-PHI treatment and EPO using the random-effects model. HIF-PHI administration upregulated transferrin (MD 36.12, 95% CI 27.04-45.20) and soluble transferrin receptors (sTfR) (MD 1.28, 95% CI 0.44-2.13), but did not statistically reduce hepcidin level (p = 0.37). Total and LDL-cholestrol levels were suppressed by HIF-PHI (MD - 0.99, 95% CI - 1.34 to  - 0.63) (MD - 0.99, 95% CI - 1.34 to - 0.64), while triglyceride (TG) was not different between HIF-PHI and EPO (p = 0.74). The total incident rates of treatment-emergent adverse events (TEAE) (p = 0.20) from HIF-PHI treatment were not different from those of erythropoietin, while the treatment-emergent serious adverse events (TSAE) (p = 0.02) were higher in the HIF-PHI group than those in the EPO controls with the fixed-effect model.

CONCLUSION

HIF-PHI could effectively upregulate and maintain haemoglobin levels in patients with anaemia receiving maintenance dialysis. Furthermore, HIF-PHI could elevate iron metabolism activity and utility without inducing treatment-associated serious adverse events. Robust data from larger RCTs with longer treatment duration and follow-up are needed.

EPO synthesis induced by HIF-PHD inhibition is dependent on myofibroblast transdifferentiation and colocalizes with non-injured nephron segments in murine kidney fibrosis

AIM

Erythropoietin (EPO) is regulated by hypoxia-inducible factor (HIF)-2. In the kidney, it is produced by cortico-medullary perivascular interstitial cells, which transdifferentiate into collagen-producing myofibroblasts in response to injury. Inhibitors of prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-2 and stimulate kidney and liver EPO synthesis in patients with anemia of chronic kidney disease (CKD). We examined whether HIF-PHIs can reactivate EPO synthesis in interstitial cells that have undergone myofibroblast transdifferentiation in established kidney fibrosis.

METHODS

We investigated Epo transcription in myofibroblasts and characterized the histological distribution of kidney Epo transcripts by RNA in situ hybridization combined with immunofluorescence in mice with adenine nephropathy (AN) treated with HIF-PHI molidustat.  Lectin absorption chromatography was used to assess liver-derived EPO.  In addition, we examined kidney Epo transcription in Phd2 knockout mice with obstructive nephropathy.

RESULTS

In AN, molidustat-induced Epo transcripts were not found in areas of fibrosis and did not colocalize with interstitial cells that expressed α-smooth muscle actin, a marker of myofibroblast transdifferentiation. Epo transcription was associated with megalin-expressing, kidney injury molecule 1-negative nephron segments and contingent on residual renal function. Liver-derived EPO did not contribute to serum EPO in molidustat-treated mice. Epo transcription was not associated with myofibroblasts in Phd2 knockout mice with obstructive nephropathy.

CONCLUSIONS

Our studies suggest that HIF-PHIs do not reactivate Epo transcription in interstitial myofibroblasts and that their efficacy in inducing kidney EPO in CKD is dependent on the degree of myofibroblast formation, the preservation of renal parenchyma and the level of residual renal function.

Fount, fate, features, and function of renal erythropoietin-producing cells

Renal erythropoietin (Epo)-producing (REP) cells represent a rare and incompletely understood cell type. REP cells are fibroblast-like cells located in close proximity to blood vessels and tubules of the corticomedullary border region. Epo mRNA in REP cells is produced in a pronounced "on-off" mode, showing transient transcriptional bursts upon exposure to hypoxia. In contrast to "ordinary" fibroblasts, REP cells do not proliferate ex vivo, cease to produce Epo, and lose their identity following immortalization and prolonged in vitro culture, consistent with the loss of Epo production following REP cell proliferation during tissue remodelling in chronic kidney disease. Because Epo protein is usually not detectable in kidney tissue, and Epo mRNA is only transiently induced under hypoxic conditions, transgenic mouse models have been developed to permanently label REP cell precursors, active Epo producers, and inactive descendants. Future single-cell analyses of the renal stromal compartment will identify novel characteristic markers of tagged REP cells, which will provide novel insights into the regulation of Epo expression in this unique cell type.

Effects of HIF-1α, hepcidin and PTH on RankL in patients with chronic kidney disease in different stages

OBJECTIVE

To investigate the effects of hypoxia-inducible factor-1α (HIF-1α), hepcidin, and parathyroid hormone (PTH) on the serum nuclear factor κB and receptor activating factor ligand (RankL) in patients with chronic kidney disease (CKD) stages 3-5.

METHODS

A total of 90 patients admitted to our hospital's Department of Nephrology from March 2018 to December 2019 were randomly selected as the subjects (30 patients with CKD3, CKD4, and CKD5 each). A total of 30 healthy volunteers receiving a physical examination in our hospital during the same period were selected for the control group. Then, the participants' HIF-1α, hepcidin, and RankL levels were detected by double-antibody sandwiched enzyme-linked immunosorbent assay. The serum creatinine, serum iron, hemoglobin, and phosphorus (P³⁺) levels were determined by BeckMAN-c800 automatic biochemical analysis. The glomerular filtration rate (eGFR) was calculated by the CKD-EPI formula.

RESULTS

(1) The levels of HIF-1α, RankL, hepcidin, and PTH were all elevated, and the serum ferritin and P³⁺ were elevated in each stage; (2) Linear correlation analysis: The HIF-1α and hepcidin showed a higher correlation with RankL in CKD3 and CKD4(CKD3: The correlation coefficient r = 0.558 between HIF-1α and RankL, and r = 0.604 between HEpcidin and RankL; CKD4: Correlation coefficient r = 0.840 between HIF-1α and RankL, and r = 0.753 between HEpcidin and RankL), while the PTH showed a higher correlation with RankL in CKD5 (correlation index r = 0.631). Multiple linear stepwise regression analysis: RankL was independently correlated with HIF-1α, hepcidin, and PTH. Regression coefficient B of HIF-1α was the highest in both CKD3 and CKD4. The coefficient B value of PTH in CKD5 was 3.971; HIF-1α and hepcidin were not included in the regression equation.

CONCLUSION

The levels of RankL in both CKD3 and CKD4 were increased and mainly affected by HIF-1α, followed by hepcidin. Moreover, HIF-1α and PTH had a combined effect on the RankL level in CKD5, and PTH was the main influencing factor.

Clinical parameters among patients in Japan with anemia and non-dialysis-dependent chronic kidney disease with and without diabetes mellitus who received roxadustat

Background

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor for treating anemia of chronic kidney disease (CKD). This post hoc analysis of a Japanese, open-label, partially randomized, phase 3 study in patients with non-dialysis-dependent (NDD) CKD evaluated disease state–related parameters among patients with and without diabetes mellitus who received roxadustat. In the 1517-CL-0310 study (NCT02988973), roxadustat was noninferior to darbepoetin alfa for change in average hemoglobin levels at Weeks 18–24 from baseline who received roxadustat.

Methods

Patients enrolled in the 1517-CL-0310 study who received roxadustat were included in this post hoc analysis. Hematologic (hemoglobin, reticulocyte/erythrocyte ratio, mean corpuscular volume [MCV], and mean corpuscular hemoglobin [MCH]), iron-related (ferritin, total iron-binding capacity, transferrin, ceruloplasmin, and hepcidin), metabolic (HbA1c, glycated albumin, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol), and renal (eGFR) parameters were summarized descriptively by visit through Week 52.

Results

Among 201 included patients, 105 (52.2%) and 96 (47.8%) were in the Diabetes and No Diabetes subgroups, respectively. There were no clinically meaningful differences through Week 52 for most hematologic, iron-related, metabolic, or renal parameters between patients in the Diabetes and No Diabetes subgroups. MCV and MCH remained lower and HbA1c and glycated albumin remained higher in patients in the Diabetes subgroup through Week 52. Both subgroups experienced a similar benefit from roxadustat in maintaining hemoglobin levels in the target range of 10–12 g/dL.

Conclusion

Roxadustat maintained hemoglobin levels in the target range with similar clinical parameters irrespective of diabetes mellitus presence at baseline.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10157-022-02225-w.

WT1: The Hinge Between Anemia Correction and Cancer Development in Chronic Kidney Disease

Hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) emerge as promising agents to treat anemia in chronic kidney disease (CKD) but the major concern is their correlated risk of cancer development and progression. The Wilms’ tumor gene, WT1, is transcriptionally regulated by HIF and is known to play a crucial role in tumorigenesis and invasiveness of certain types of cancers. From the mechanism of action of HIF–PHIs, to cancer hypoxia and the biological significance of WT1, this review will discuss the link between HIF, WT1, anemia correction, and cancer. We aimed to reveal the research gaps and offer a focused strategy to monitor the development and progression of specific types of cancer when using HIF–PHIs to treat anemia in CKD patients. In addition, to facilitate the long-term use of HIF–PHIs in anemic CKD patients, we will discuss the strategy of WT1 inhibition to reduce the development and progression of cancer.

The hypoxia-inducible factor prolyl hydroxylase inhibitor FG4592 promotes natriuresis through upregulation of COX2 in the renal medulla

The renal medulla is a key site for the regulation of renal sodium excretion. However, the molecular mechanism remains unclear. Cyclooxygenase 2 (COX2) is specifically expressed in the renal medulla and contributes to the maintenance of the electrolyte/water balance in the body. Hypoxia-inducible factors (HIFs) have also been found to be expressed in the renal medulla, probably owing to the hypoxic conditions in the renal medulla. This study was designed to test the effects of HIF activation on renal sodium handling and renal medullary COX2 expression. Our data showed that HIF activation by the prolyl hydroxylase inhibitor (PHI) FG4592 enhanced natriuresis in mice challenged with a high-salt diet. In addition, FG4592 upregulated the expression of COX2 in the renal medulla. An in vitro study further supported the finding that HIF can induce the expression of COX2 and that this induction is mediated through direct binding to the promoter region of the Cox2 gene, facilitating its transcription. In addition, the COX2 inhibitor celecoxib diminished the natriuretic effect of FG4592. Together, these results suggest that HIF activation promotes sodium excretion through upregulation of COX2 in the renal medulla and therefore maintains sodium homeostasis in the body.

Fate-mapping of erythropoietin-producing cells in mouse models of hypoxaemia and renal tissue remodelling reveals repeated recruitment and persistent functionality

Aim

Fibroblast‐like renal erythropoietin (Epo) producing (REP) cells of the corticomedullary border region “sense” a decrease in blood oxygen content following anaemia or hypoxaemia. Burst‐like transcription of Epo during tissue hypoxia is transient and is lost during fibrotic tissue remodelling, as observed in chronic kidney disease. The reason for this loss of Epo expression is under debate. Therefore, we tested the hypothesis that REP cell migration, loss and/or differentiation may cause Epo inhibition.

Methods

Using a reporter mouse that allows permanent labelling of active REP cells at any given time point, we analysed the spatiotemporal fate of REP cells following their initial hypoxic recruitment in models of hypoxaemia and renal tissue remodelling.

Results

In long‐term tracing experiments, tagged REP reporter cells neither died, proliferated, migrated nor transdifferentiated into myofibroblasts. Approximately 60% of tagged cells re‐expressed Epo upon a second hypoxic stimulus. In an unilateral model of tissue remodelling, tagged cells proliferated and ceased to produce Epo before a detectable increase in myofibroblast markers. Treatment with a hypoxia‐inducible factor (HIF) stabilizing agent (FG‐4592/roxadustat) re‐induced Epo expression in the previously active REP cells of the damaged kidney to a similar extent as in the contralateral healthy kidney.

Conclusions

Rather than cell death or differentiation, these results suggest cell‐intrinsic transient inhibition of Epo transcription: following long‐term dormancy, REP cells can repeatedly be recruited by tissue hypoxia, and during myofibrotic tissue remodelling, dormant REP cells are efficiently rescued by a pharmaceutic HIF stabilizer, demonstrating persistent REP cell functionality even during phases of Epo suppression.

The Impact of Obesity, Adipose Tissue, and Tumor Microenvironment on Macrophage Polarization and Metastasis

Tumor metastasis is a major cause of death in cancer patients. It involves not only the intrinsic alterations within tumor cells, but also crosstalk between these cells and components of the tumor microenvironment (TME). Tumorigenesis is a complex and dynamic process, involving the following three main stages: initiation, progression, and metastasis. The transition between these stages depends on the changes within the extracellular matrix (ECM), in which tumor and stromal cells reside. This matrix, under the effect of growth factors, cytokines, and adipokines, can be morphologically altered, degraded, or reorganized. Many cancers evolve to form an immunosuppressive TME locally and create a pre-metastatic niche in other tissue sites. TME and pre-metastatic niches include myofibroblasts, immuno-inflammatory cells (macrophages), adipocytes, blood, and lymphatic vascular networks. Several studies have highlighted the adipocyte-macrophage interaction as a key driver of cancer progression and dissemination. The following two main classes of macrophages are distinguished: M1 (pro-inflammatory/anti-tumor) and M2 (anti-inflammatory/pro-tumor). These cells exhibit distinct microenvironment-dependent phenotypes that can promote or inhibit metastasis. On the other hand, obesity in cancer patients has been linked to a poor prognosis. In this regard, tumor-associated adipocytes modulate TME through the secretion of inflammatory mediators, which modulate and recruit tumor-associated macrophages (TAM). Hereby, this review describes the cellular and molecular mechanisms that link inflammation, obesity, and cancer. It provides a comprehensive overview of adipocytes and macrophages in the ECM as they control cancer initiation, progression, and invasion. In addition, it addresses the mechanisms of tumor anchoring and recruitment for M1, M2, and TAM macrophages, specifically highlighting their origin, classification, polarization, and regulatory networks, as well as their roles in the regulation of angiogenesis, invasion, metastasis, and immunosuppression, specifically highlighting the role of adipocytes in this process.

Roxadustat for the treatment of anemia in patients with lower-risk myelodysplastic syndrome: Open-label, dose-selection, lead-in stage of a phase 3 study

Anemia is the predominant cytopenia in myelodysplastic syndromes (MDS) and treatment options are limited. Roxadustat is a hypoxia-inducible factor prolyl hydroxylase inhibitor approved for the treatment of anemia of chronic kidney disease in the UK, EU, China, Japan, South Korea, and Chile. MATTERHORN is a phase 3, randomized, double-blind, placebo-controlled study to assess the efficacy and safety of roxadustat in anemia of lower risk-MDS. Eligible patients had baseline serum erythropoietin ≤ 400 mIU/mL, and a low packed RBC transfusion burden. In this open-label (OL), dose-selection, lead-in phase, enrolled patients were assigned to 1 of 3 roxadustat starting doses (n = 8 each): 1.5, 2.0, and 2.5 mg/kg. The primary efficacy endpoint of the OL phase was the proportion of patients with transfusion independence (TI) for ≥ 8 consecutive weeks in the first 28 treatment weeks. A secondary efficacy endpoint was the proportion of patients with a ≥ 50% reduction in RBC transfusions over an 8-week period compared with baseline. Adverse events were monitored. Patients were followed for 52 weeks. Of the 24 treated patients, TI was achieved in 9 patients (37.5%) at 28 and 52 weeks; 7 of these patients were receiving 2.5 mg/kg dose when TI was achieved. A ≥ 50% reduction in RBC transfusions was achieved in 54.2% and 58.3% of patients at 28 and 52 weeks, respectively. Oral roxadustat dosed thrice weekly was well tolerated. There were no fatalities or progression to acute myeloid leukemia. Based on these outcomes, 2.5 mg/kg was the chosen starting roxadustat dose for the ongoing double-blind study phase.

New developments in anaemia treatment - erythropoietin versus prolyl hydroxylase inhibitors?

Anaemia is a very common complication of chronic kidney disease (CKD) and renal failure. The view of the treatment of anaemia has changed considerably since the introduction of ESAs (erythropoiesis-stimulating agents) into clinical practice, and the safety of this treatment is now prioritised over complete normalisation of haemoglobin (Hb) values. Iron administration is the mainstay of treatment in this group of patients, with intravenous administration proving to be both more effective and safer in both predialysis and dialysis patients. In addition to the long-used ESAs, a number of new agents developed to favourably influence erythropoiesis have recently been tested for the correction of anaemia. Among those with the greatest potential are the HIF-stabilizers (roxadustat, molidustat, vadadustat and daprodustat), which act through stimulation of erythropoiesis genes and thus represent a novel mechanism of action in the treatment of anaemia. In phase 3 clinical trials, these agents have shown the same efficacy in increasing Hb levels as ESAs, but much emphasis has recently been placed on their safety profile. They are orally administered agents and some of them are already approved and used in clinical practice. The first of these, roxadustat, is currently reimbursed also in the Czech Republic. Other molecules affecting anaemia, such as sotatercept, have also been confirmed to be effective in phase 1 and 2 clinical trials and are awaiting results from larger randomised trials.

Dysregulation of the sensory and regulatory pathways controlling cellular iron metabolism in unilateral obstructive nephropathy

Chronic kidney disease involves disturbances in iron metabolism including anemia caused by insufficient erythropoietin (EPO) production. However, underlying mechanisms responsible for the dysregulation of cellular iron metabolism are incompletely defined. Using the unilateral ureteral obstruction (UUO) model in Irp1+/+ and Irp1-/- mice, we asked if iron regulatory proteins (IRPs), the central regulators of cellular iron metabolism and suppressors of EPO production, contribute to the etiology of anemia in kidney failure. We identified a significant reduction in IRP protein level and RNA binding activity that associates with a loss of the iron uptake protein transferrin receptor 1 (TfR1), increased expression of the iron storage protein subunits H- and L-ferritin, and a low but overall variable level of stainable iron in the obstructed kidney. This reduction in IRP RNA binding activity and ferritin RNA levels suggests the concomitant rise in ferritin expression and iron content in kidney failure is IRP dependent. In contrast, the reduction in the Epo mRNA level in the obstructed kidney was not rescued by genetic ablation of IRP1, suggesting disruption of normal hypoxia-inducible factor (HIF)-2α regulation. Furthermore, reduced expression of some HIF-α target genes in UUO occurred in the face of increased expression of HIF-α proteins and prolyl hydroxylases 2 and 1, the latter of which is not known to be HIF-α mediated. Our results suggest that the IRP system drives changes in cellular iron metabolism that are associated with kidney failure in UUO but that the impact of IRPs on EPO production is overridden by disrupted hypoxia signaling.NEW & NOTEWORTHY This study demonstrates that iron metabolism and hypoxia signaling are dysregulated in unilateral obstructive nephropathy. Expression of iron regulatory proteins (IRPs), central regulators of cellular iron metabolism, and the iron uptake (transferrin receptor 1) and storage (ferritins) proteins they target is strongly altered. This suggests a role of IRPs in previously observed changes in iron metabolism in progressive renal disease. Hypoxia signaling is disrupted and appeared to dominate the action of IRP1 in controlling erythropoietin expression.

Daprodustat for the Treatment of Anemia in Patients Undergoing Dialysis

BACKGROUND

Among patients with chronic kidney disease (CKD), the use of recombinant human erythropoietin and its derivatives for the treatment of anemia has been linked to a possibly increased risk of stroke, myocardial infarction, and other adverse events. Several trials have suggested that hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors (PHIs) are as effective as erythropoiesis-stimulating agents (ESAs) in increasing hemoglobin levels.

METHODS

In this randomized, open-label, phase 3 trial, we assigned patients with CKD who were undergoing dialysis and who had a hemoglobin level of 8.0 to 11.5 g per deciliter to receive an oral HIF-PHI (daprodustat) or an injectable ESA (epoetin alfa if they were receiving hemodialysis or darbepoetin alfa if they were receiving peritoneal dialysis). The two primary outcomes were the mean change in the hemoglobin level from baseline to weeks 28 through 52 (noninferiority margin, -0.75 g per deciliter) and the first occurrence of a major adverse cardiovascular event (a composite of death from any cause, nonfatal myocardial infarction, or nonfatal stroke), with a noninferiority margin of 1.25.

RESULTS

A total of 2964 patients underwent randomization. The mean (±SD) baseline hemoglobin level was 10.4±1.0 g per deciliter overall. The mean (±SE) change in the hemoglobin level from baseline to weeks 28 through 52 was 0.28±0.02 g per deciliter in the daprodustat group and 0.10±0.02 g per deciliter in the ESA group (difference, 0.18 g per deciliter; 95% confidence interval [CI], 0.12 to 0.24), which met the prespecified noninferiority margin of -0.75 g per deciliter. During a median follow-up of 2.5 years, a major adverse cardiovascular event occurred in 374 of 1487 patients (25.2%) in the daprodustat group and in 394 of 1477 (26.7%) in the ESA group (hazard ratio, 0.93; 95% CI, 0.81 to 1.07), which also met the prespecified noninferiority margin for daprodustat. The percentages of patients with other adverse events were similar in the two groups.

CONCLUSIONS

Among patients with CKD undergoing dialysis, daprodustat was noninferior to ESAs regarding the change in the hemoglobin level from baseline and cardiovascular outcomes. (Funded by GlaxoSmithKline; ASCEND-D ClinicalTrials.gov number, NCT02879305.).

Clinical Pharmacokinetics and Pharmacodynamics of Roxadustat

The pharmacokinetics of roxadustat are well characterized, with an apparent volume of distribution after oral administration of 22–57 L, apparent clearance of 1.2–2.65 L/h, and renal clearance of 0.030–0.026 L/h in healthy volunteers; the elimination half-life is 9.6–16 h. Plasma binding is 99% and the fraction eliminated by hemodialysis is 2.34%. As an interpretation of the pharmacodynamics of roxadustat, we proposed a concept with a hypothetical cascade of two subsequent effects, first on erythropoetin (EPO) and second on hemoglobin (delta Hb). The primary effect on EPO is observed within a few hours after roxadustat administration and can be modeled using the sigmoidal Hill equation. The concentration at half-maximum effect can be inferred at 10–36 µg/mL, the Hill coefficient at 3.3, and the effect bisection time at 10–17 h, corresponding to EPO half-life. The subsequent effect on hemoglobin (delta Hb) is observed after several weeks and can be interpreted as an irreversible, dose proportional, unsaturable effect, continuing in agreement with the lifespan of red blood cells of 63–112 days.

Hypoxia-Inducible Factor Stabilizers in End Stage Kidney Disease: "Can the Promise Be Kept?"

Anemia is a common complication of chronic kidney disease (CKD). The prevalence of anemia in CKD strongly increases as the estimated Glomerular Filtration Rate (eGFR) decreases. The pathophysiology of anemia in CKD is complex. The main causes are erythropoietin (EPO) deficiency and functional iron deficiency (FID). The administration of injectable preparations of recombinant erythropoiesis-stimulating agents (ESAs), especially epoetin and darbepoetin, coupled with oral or intravenous(iv) iron supplementation, is the current treatment for anemia in CKD for both dialysis and non-dialysis patients. This approach reduces patients' dependence on transfusion, ensuring the achievement of optimal hemoglobin target levels. However, there is still no evidence that treating anemia with ESAs can significantly reduce the risk of cardiovascular events. Meanwhile, iv iron supplementation causes an increased risk of allergic reactions, gastrointestinal side effects, infection, and cardiovascular events. Currently, there are no studies defining the best strategy for using ESAs to minimize possible risks. One class of agents under evaluation, known as prolyl hydroxylase inhibitors (PHIs), acts to stabilize hypoxia-inducible factor (HIF) by inhibiting prolyl hydroxylase (PH) enzymes. Several randomized controlled trials showed that HIF-PHIs are almost comparable to ESAs. In the era of personalized medicine, it is possible to envisage and investigate specific contexts of the application of HIF stabilizers based on the individual risk profile and mechanism of action.

Inhibition of AlkB Nucleic Acid Demethylases: Promising New Epigenetic Targets

The AlkB family of nucleic acid demethylases is currently of intense chemical, biological, and medical interest because of its critical roles in several key cellular processes, including epigenetic gene regulation, RNA metabolism, and DNA repair. Emerging evidence suggests that dysregulation of AlkB demethylases may underlie the pathogenesis of several human diseases, particularly obesity, diabetes, and cancer. Hence there is strong interest in developing selective inhibitors for these enzymes to facilitate their mechanistic and functional studies and to validate their therapeutic potential. Herein we review the remarkable advances made over the past 20 years in AlkB demethylase inhibition research. We discuss the rational design of reported inhibitors, their mode-of-binding, selectivity, cellular activity, and therapeutic opportunities. We further discuss unexplored structural elements of the AlkB subfamilies and propose potential strategies to enable subfamily selectivity. It is hoped that this perspective will inspire novel inhibitor design and advance drug discovery research in this field.