Evaluation of Food and Spherical Carbon Adsorbent Effects on the Pharmacokinetics of Roxadustat in Healthy Nonelderly Adult Male Japanese Subjects

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.

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Targeting hypoxia-inducible factors: therapeutic opportunities and challenges

Hypoxia-inducible factors (HIFs) are highly conserved transcription factors that are crucial for adaptation of metazoans to limited oxygen availability. Recently, HIF activation and inhibition have emerged as therapeutic targets in various human diseases. Pharmacologically desirable effects of HIF activation include erythropoiesis stimulation, cellular metabolism optimization during hypoxia and adaptive responses during ischaemia and inflammation. By contrast, HIF inhibition has been explored as a therapy for various cancers, retinal neovascularization and pulmonary hypertension. This Review discusses the biochemical mechanisms that control HIF stabilization and the molecular strategies that can be exploited pharmacologically to activate or inhibit HIFs. In addition, we examine medical conditions that benefit from targeting HIFs, the potential side effects of HIF activation or inhibition and future challenges in this field.

Roxadustat: Not just for anemia

Roxadustat is a recently approved hypoxia-inducible factor prolyl hydroxylase inhibitor that has demonstrated favorable safety and efficacy in the treatment of renal anemia. Recent studies found it also has potential for the treatment of other hypoxia-related diseases. Although clinical studies have not yet found significant adverse or off-target effects of roxadustat, clinicians must be vigilant about these possible effects. Hypoxia-inducible factor regulates the expression of many genes and physiological processes in response to a decreased level of oxygen, but its role in the pathogenesis of different diseases is complex and controversial. In addition to increasing the expression of hypoxia-inducible factor, roxadustat also has some effects that may be HIF-independent, indicating some potential off-target effects. This article reviews the pharmacological characteristics of roxadustat, its current status in the treatment of renal anemia, and its possible effects on other pathological mechanisms.

Effect of Roxadustat on the Pharmacokinetics of Simvastatin, Rosuvastatin, and Atorvastatin in Healthy Subjects: Results From 3 Phase 1, Open-Label, 1-Sequence, Crossover Studies

Roxadustat inhibits breast cancer resistance protein and organic anion transporting polypeptide 1B1, which can affect coadministered statin concentrations. Three open‐label, 1‐sequence crossover phase 1 studies in healthy subjects were conducted to assess effects from steady‐state 200‐mg roxadustat on pharmacokinetics and tolerability of 40‐mg simvastatin (CL‐0537 and CL‐0541), 40‐mg atorvastatin (CL‐0538), or 10‐mg rosuvastatin (CL‐0537). Statins were dosed concomitantly with roxadustat in 28 (CL‐0537) and 24 (CL‐0538) healthy subjects, resulting in increases of maximum plasma concentration (C_max) and area under the plasma concentration–time curve from the time of dosing extrapolated to infinity (AUC_inf) 1.87‐ and 1.75‐fold for simvastatin, 2.76‐ and 1.85‐fold for simvastatin acid, 4.47‐ and 2.93‐fold for rosuvastatin, and 1.34‐ and 1.96‐fold for atorvastatin, respectively. Additionally, simvastatin dosed 2 hours before, and 4 and 10 hours after roxadustat in 28 (CL‐0541) healthy subjects, resulted in increases of C_max and AUC_inf 2.32‐ to 3.10‐fold and 1.56‐ to 1.74‐fold for simvastatin and 2.34‐ to 5.98‐fold and 1.89‐ to 3.42‐fold for simvastatin acid, respectively. These increases were not attenuated by time‐separated statin dosing. No clinically relevant differences were observed for terminal elimination half‐life. Concomitant 200‐mg roxadustat and a statin was generally well tolerated during the study period. Roxadustat effects on statin C_max and AUC_inf were statin and administration time dependent. When coadministered with roxadustat, statin‐associated adverse reactions and the need for statin dose reduction should be evaluated.

Esterification promotes the intracellular accumulation of roxadustat, an activator of hypoxia-inducible factors, to extend its effective duration

Kidney injury often causes anemia due to a lack of production of the erythroid growth factor erythropoietin (EPO) in the kidneys. Roxadustat is one of the first oral medicines inducing EPO production in patients with renal anemia by activating hypoxia-inducible factors (HIFs), which are activators of EPO gene expression. In this study, to develop prodrugs of roxadustat with improved permeability through cell membrane, we investigated the effects of 8 types of esterification on the pharmacokinetics and bioactivity of roxadustat using Hep3B hepatoma cells that HIF-dependently produce EPO. Mass spectrometry of cells incubated with the esterified roxadustat derivatives revealed that the designed compounds were deesterified after being taken up by cells and showed low cytotoxicity compared to the original compound. Esterification prolonged the effective duration of roxadustat with respect to EPO gene induction and HIF activation in cells transiently exposed to the compounds. In the kidneys and livers of mice, both of which are unique sites of EPO production, a majority of the methyl-esterified roxadustat was deesterified within 6 h after drug administration. The deesterified roxadustat derivative was continuously detectable in plasma and urine for at least 48 h after administration, while the administered compound became undetectable 24 h after administration. Additionally, we confirmed that methyl-esterified roxadustat activated erythropoiesis in mice by inducing Epo mRNA expression exclusively in renal interstitial cells, which have intrinsic EPO-producing potential. These data suggest that esterification could lead to the development of roxadustat prodrugs with improvements in cell membrane permeability, effective duration and cytotoxicity.

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.

Population pharmacokinetics of roxadustat in Japanese dialysis-dependent chronic kidney disease patients with anaemia

Aims

Our objective was to develop a population pharmacokinetic (PK) model to describe roxadustat plasma concentrations in Japanese dialysis‐dependent chronic kidney disease (DD‐CKD) patients with renal anaemia and to identify the covariate factors that affect exposure of roxadustat.

Methods

In total, 367 patients (male, 256; female, 111) contributing 1285 concentration values from 4 clinical studies were analysed using a nonlinear mixed‐effects modelling approach. Candidate covariates included clinical characteristics hypothesized to affect roxadustat clearance and bioavailability, such as demographics, hepatic parameters and concomitant drugs.

Results

The roxadustat PK data in Japanese DD‐CKD patients with renal anaemia were well described by a 2‐compartment disposition model with first‐order absorption and interindividual variability on clearance, central volume of distribution and absorption rate constant. Age was identified as a significant covariate on clearance. PK profiles of haemodialysis and peritoneal dialysis patients were comparable. Eighty‐two percent of patients were administered at least 1 phosphate binder (PB). The effect of PBs on roxadustat concentration was modelled as a decrease in bioavailability. Staggered administration of PBs reduced the effect on roxadustat bioavailability. The clinical impact of all covariates on roxadustat PK was mild and manageable as the roxadustat dose was titrated based on haemoglobin level and administered starting from a low dose.

Conclusion

Roxadustat PK in Japanese DD‐CKD patients were successfully described by a population PK model. The identified key covariates included coadministration of PBs on the roxadustat bioavailability and age on clearance of roxadustat.

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

PURPOSE

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

METHODS

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

IMPLICATIONS

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

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

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

Pharmacokinetics of Roxadustat: A Population Analysis of 2855 Dialysis- and Non-Dialysis-Dependent Patients with Chronic Kidney Disease

BACKGROUND

Roxadustat is a novel, small-molecule, first-in-class therapeutic that stimulates erythropoiesis by inhibiting hypoxia-inducible factor prolyl hydroxylase enzymes. This agent (roxadustat) is in clinical development for the treatment of anemia in patients with non-dialysis-dependent (NDD) and dialysis-dependent (DD) chronic kidney disease. A population pharmacokinetic analysis was undertaken to evaluate the effect of intrinsic and extrinsic factors on roxadustat pharmacokinetics.

METHODS

Non-linear mixed-effects models implemented in NONMEM software were fitted to 8209 pharmacokinetic samples from 2855 DD and NDD subjects enrolled in four phase III studies with roxadustat dose concentrations of 20-400 mg as orally administered tablets. Effects of intrinsic and extrinsic factors were evaluated using a stepwise covariate modeling procedure in combination with the full covariate approach, and defined no-effect boundaries for exposure were based on the difference in exposure between 70 and 100 mg of roxadustat (i.e., - 30%, + 43%).

RESULTS

A two-compartment model with first-order absorption adequately described roxadustat pharmacokinetics, with parameter estimates (relative standard error) for apparent clearance of 1.1 (0.0223) L/h in NDD subjects, and apparent central and peripheral volumes of distribution of 14.9 (0.0278) L and 9.5 (0.0872) L, respectively. Stepwise covariate modeling identified bodyweight, dialysis status, race, and dose as statistically significant covariates on apparent clearance, and bodyweight, sex, and albumin as statistically significant covariates on apparent central volume of distribution. However, the effects of these covariates did not result in roxadustat area under the curve or maximum plasma concentration changes outside of the defined no-effect boundaries. The effects of concomitant oral iron, clopidogrel, and staggered sevelamer, calcium carbonate, or calcium acetate were investigated using a full covariate approach but did not result in roxadustat area under the curve or maximum plasma concentration changes outside of the defined no-effect boundaries.

CONCLUSIONS

A population pharmacokinetic model was developed for the pharmacokinetics of roxadustat in the target population. None of the investigated intrinsic or extrinsic factors resulted in a significant change in roxadustat exposure outside of the defined no-effect boundaries.

Burden of Anemia in Chronic Kidney Disease: Beyond Erythropoietin

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

The prolyl hydroxylase inhibitor roxadustat: Paradigm in drug discovery and prospects for clinical application beyond anemia

Prolyl hydroxylase (PHD) inhibitors, such as roxadustat, can stabilize hypoxia-inducible factor (HIF)-2α and induce erythropoietin (EPO) production under normal conditions. Roxadustat was recently approved as a first-in-class orally active drug for the treatment of renal anemia. In addition, it has garnered growing therapeutic interest for use against various diseases, such as carcinoma, neurological diseases, ocular diseases, and tissue and organ injuries. In this review, we systemically review target validation, hit identification, and further key clinical trials of roxadustat. The prospective clinical applications of PHD inhibitors are then discussed based on this marketed drug.

Evidence for the Capability of Roxadustat (FG-4592), an Oral HIF Prolyl-Hydroxylase Inhibitor, to Perturb Membrane Ionic Currents: An Unidentified yet Important Action

Roxadustat (FG-4592), an analog of 2-oxoglutarate, is an orally-administered, heterocyclic small molecule known to be an inhibitor of hypoxia inducible factor (HIF) prolyl hydroxylase. However, none of the studies have thus far thoroughly investigated its possible perturbations on membrane ion currents in endocrine or heart cells. In our studies, the whole-cell current recordings of the patch-clamp technique showed that the presence of roxadustat effectively and differentially suppressed the peak and late components of I_K(DR) amplitude in response to membrane depolarization in pituitary tumor (GH₃) cells with an IC₅₀ value of 5.71 and 1.32 μM, respectively. The current inactivation of I_K(DR) elicited by 10-sec membrane depolarization became raised in the presence of roxadustatt. When cells were exposed to either CoCl₂ or deferoxamine (DFO), the I_K(DR) elicited by membrane depolarization was not modified; however, nonactin, a K⁺-selective ionophore, in continued presence of roxadustat, attenuated roxadustat-mediated inhibition of the amplitude. The steady-state inactivation of I_K(DR) could be constructed in the presence of roxadustat. Recovery of I_K(DR) block by roxadustat (3 and 10 μM) could be fitted by a single exponential with 382 and 523 msec, respectively. The roxadustat addition slightly suppressed erg-mediated K⁺ or hyperpolarization-activated cation currents. This drug also decreased the peak amplitude of voltage-gated Na⁺ current with a slowing in inactivation rate of the current. Likewise, in H9c2 heart-derived cells, the addition of roxadustat suppressed I_K(DR) amplitude in combination with the shortening in inactivation time course of the current. In high glucose-treated H9c2 cells, roxadustat-mediated inhibition of I_K(DR) remained unchanged. Collectively, despite its suppression of HIF prolyl hydroxylase, inhibitory actions of roxadustat on different types of ionic currents possibly in a non-genomic fashion might provide another yet unidentified mechanism through which cellular functions are seriously perturbed, if similar findings occur in vivo.

Roxadustat: First Global Approval

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