Editorials: Recombinant Human Erythropoietin: Has Treatment Reached its Full Potential?

Engineering Strategies for Immunomodulatory Cytokine Therapies - Challenges and Clinical Progress

Cytokines are immunoregulatory proteins involved in many pathological states with promising potential as therapeutic agents. A diverse array of cytokines have been studied in preclinical disease models since the 1950s, some of which became successful biopharmaceutical products with the advancement of recombinant protein technology in the 1980s. However, following these early approvals, clinical translation of these natural immune signaling molecules has been limited due to their pleiotropic action in many cell types, and the fact that they have evolved to act primarily locally in tissues. These characteristics, combined with poor pharmacokinetics, have hindered the delivery of cytokines via systemic administration routes due to dose-limiting toxicities. However, given their clinical potential and recent clinical successes in cancer immunotherapy, cytokines continue to be extensively pursued in preclinical and clinical studies, and a range of molecular and formulation engineering strategies are being applied to reduce treatment toxicity while maintaining or enhancing therapeutic efficacy. This review provides a brief background on the characteristics of cytokines and their history as clinical therapeutics, followed by a deeper discussion on the engineering strategies developed for cytokine therapies with a focus on the translational relevance of these approaches.

Is there an established hemoglobin target range for patients undergoing chronic dialysis?

Anemia is a common complication of advanced chronic kidney disease (CKD). Treatment with erythropoiesis-stimulating agents (ESAs) remains a common approach in managing anemia of CKD. The 2012 Kidney Disease Improving Global Outcomes Clinical Practice Guideline for Anemia in CKD suggests avoiding ESA therapy use to maintain Hb level above 11.5 g/dL. However, optimal Hb target range in adult patients undergoing chronic dialysis remains unknown. Clinical studies suggest risks associated with normalization of Hb levels in adult patients with CKD. In this article, we briefly review some of these studies and the concerns associated with higher Hb targets in this patient population. We also suggest a target Hb range for adult chronic dialysis patients receiving ESAs. It is currently undetermined if this target Hb range would apply to newer agents that are being studied for anemia management in this population.

Conversion from epoetin and darbepoetin to C.E.R.A. in non-dialysis CKD patients: a multicenter Italian prospective study in nephrology practice

BACKGROUND

In non-dialysis patients (ND-CKD), C.E.R.A. has been extensively investigated in ESA-naïve subjects but no data are available on its efficacy after switch from other ESA.

METHODS

In this prospective, multicenter, open-label study lasting 24 weeks, ND-CKD patients (n = 157) receiving ESA were converted to C.E.R.A. at doses lower than recommended. Primary outcome was the prevalence of Hb target (11-12.5 g/dl).

RESULTS

Age was 73 ± 13 years and GFR was 26.2 ± 9.4 ml/min/1.73 m(2); male gender, diabetes and prior cardiovascular disease were 49, 33 and 19%, respectively. Doses of darbepoetin (25 ± 16 µg/week, n = 124) and epoetin (5,702 ± 3,190 IU/week, n = 33) were switched to low dose C.E.R.A. (87 ± 17 µg/month). During the study, prevalence of Hb target increased from 60% to 68% at week-24, while that of Hb < 11 g/dl declined from 32% to 16% (p < 0.001). Hb increased from 11.3 ± 0.8 at baseline to 11.7 ± 0.9 g/dl at week-24 (p = 0.01) without changes in C.E.R.A. dose. Significant predictors of Hb increase were low BMI, low Hb and longer dosing intervals before switch. These factors also predicted the risk of Hb overshooting (Hb > 12.5 g/dl) occurring in 57 patients.

CONCLUSIONS

In ND-CKD, conversion from other ESAs to C.E.R.A. is associated with a better anemia control induced by a greater Hb increase in patients previously treated with ESAs at extended dosing interval. This parameter should be considered when switching to long-acting ESA for its potential impact on the risk of overshooting.

Herpesvirus entry mediator regulates hypoxia-inducible factor-1α and erythropoiesis in mice

Erythropoiesis, the production of red blood cells, must be tightly controlled to ensure adequate oxygen delivery to tissues without causing thrombosis or stroke. Control of physiologic and pathologic erythropoiesis is dependent predominantly on erythropoietin (EPO), the expression of which is regulated by hypoxia-inducible factor (HIF) activity in response to low oxygen tension. Accumulating evidence indicates that oxygen-independent mediators, including inflammatory stimuli, cytokines, and growth factors, also upregulate HIF activity, but it is unclear whether these signals also result in EPO production and erythropoiesis in vivo. Here, we found that signaling through herpesvirus entry mediator (HVEM), a molecule of the TNF receptor superfamily, promoted HIF-1α activity in the kidney and subsequently facilitated renal Epo production and erythropoiesis in vivo under normoxic conditions. This Epo upregulation was mediated by increased production of NO by renal macrophages. Hvem-deficient mice displayed impaired Epo expression and aggravated anemia in response to erythropoietic stress. These data reveal that HVEM signaling functions to promote HIF-1α activity and Epo production, and thus to regulate erythropoiesis. Furthermore, our findings suggest that this molecular mechanism could represent a therapeutic target for Epo-responsive diseases, including anemia.

Simplifying anemia management in hemodialysis patients: ESAs administered at longer dosing intervals can enhance opportunities to provide patient-focused care

OBJECTIVE

To review issues and challenges in caring for hemodialysis patients with anemia of chronic kidney disease, specifically focusing on the effects of longer erythropoiesis-stimulating agent (ESA) dosing intervals on processes of care.

METHODS

PubMed searches were performed limited to the last 10 years to February 2011, focusing on articles in English that were 'clinical trials,' assessed processes of care, measured associations of hemoglobin (Hb) with outcomes, and explored/analyzed extended dosing intervals of ESAs in hemodialysis patients and recommendations for increasing the quality of care of these patients. Some limitations included the fact that a meta-analysis was not conducted; many studies were associative and therefore unable to prove causality; and none of the clinical trials directly compared the impact of more frequent or less frequent ESA dosing strategies on patient care and outcomes.

FINDINGS

Progress over the past several decades has been substantial; however, unmet needs remain and there is room for improvement in efficiencies of care. Many patients fail to meet Hb targets, and nephrology professionals' time is consumed with preparing, administering, and monitoring therapy. Direct interaction between patients and care providers has been lost as attention has shifted to 'cost-effective' (not necessarily patient-centered) ways to deliver care. Use of ESAs at longer dosage intervals represents one opportunity to improve efficiency of care. Newer ESAs have been developed for less frequent dosing. Once-monthly dosing decreases time spent administering/monitoring therapy and allows nephrology professionals to provide comprehensive renal care, wherein the patient rather than task-oriented processes becomes the primary focus.

CONCLUSIONS

A fragmented, uncoordinated care-delivery model heightens the urgency to systematically address issues related to delivery of care and improve efficiencies in anemia management as part of the patient-centered approach. ESAs designed for administration at longer intervals may effectively and reliably achieve Hb targets with once-monthly dosing, thereby decreasing time spent administering/monitoring therapy.

Haemoglobin fluctuations in patients on haemodialysis treated with ESAs: clinical observations from two centres

BACKGROUND

The purpose of this analysis was to quantify haemoglobin (Hb) variability in patients receiving haemodialysis (HD) and erythropoiesis-stimulating agent (ESA) treatment from data independently collected in two different geographical settings. STUDY DESIGN, SETTINGS AND PATIENTS: Two studies retrospectively reviewed patients undergoing HD and stable ESA treatment at centres in Australia and the UK (56 and 154 patients, respectively). Monthly Hb values were obtained over a 12-month period. The frequency, duration, amplitude and direction of Hb fluctuations (Hb outside the range 11-12 g/dl in the Australian data-set and 11-12.5 g/dl in the UK data-set) were evaluated.

RESULTS

The overall mean Hb level was 11.27 and 11.71 g/dl in the Australian and UK data-set, respectively. All patients experienced > or =1 Hb fluctuation and 68-73% had > or =3 fluctuations over the study period. Upward and downward Hb fluctuations occurred with similar frequency and were of similar amplitude. Fluctuations of more extreme amplitude (high amplitude fluctuations) were more common than fluctuations of lesser amplitude. The total duration of time spent outside the Hb range (mean +/- standard deviation) was 8.6 +/- 2.5 and 7.4 +/- 2.5 months in the Australian and UK data-set, respectively. The total duration with Hb <11 g/dl was 3.7 +/- 3.0 and 3.7 +/- 2.7 months, respectively. Most patients (95%) required ESA dose adjustment; the median number of dose adjustments per patient was 2 (range 0-5).

CONCLUSIONS

Despite the study limitations of retrospectivity and its cross-sectional nature, the reported observations that Hb fluctuations outside target ranges occur frequently in patients on HD receiving ESAs are clearly confirmed and were strikingly similar in the two different geographical locations.

Arterial hypertension induced by erythropoietin and erythropoiesis-stimulating agents (ESA)

This review summarizes the evidence for a hypertensinogenic effect of Erythropoietin (Epo) in normal human subjects and predialysis, hemodialysis, and continuous ambulatory peritoneal dialysis (CAPD) patients. The possible mechanisms of Epo-induced hypertension are examined with in vivo animal and in vitro data, as well as pathophysiological human studies in both normal subjects and CKD patients. The evidence for a hypertensinogenic effect of erythropoiesis-stimulating agents (ESAs) in normal subjects, predialysis CKD, hemodialysis, and CAPD patients is compelling. Epo increases BP directly and notably independently of its erythropoietic effect and its effect on blood rheology. The potential for the development of future agents that might act as specific stimulators of erythropoiesis, devoid of direct hemodynamic side effects is underscored.

Anemia and cardiovascular risk in the patient with kidney disease

Patients with chronic kidney disease (CKD) often experience anemia, which causes fatigue and diminished quality of life. In addition, anemia in CKD has been associated with increased risk for cardiovascular events and left ventricular hypertrophy. To the extent that anemia plays a causal role in these relationships, treatment with erythropoiesis-stimulating agents (ESAs) could potentially help improve outcomes. To date, however, results from interventional studies have been disappointing in this regard. This article reviews the relationship between anemia in CKD and cardiovascular risk and explores current knowledge on ESA treatment.

Extended administration of erythropoiesis-stimulating agents for optimising the management of renal anaemia: what is the evidence?

BACKGROUND

Erythropoiesis-stimulating agents (ESAs) have transformed the management of anaemia in patients with chronic kidney disease (CKD), reducing transfusion requirements and leading to improved quality of life. However, effective anaemia management with current ESAs is labour-intensive and time-consuming. Approaches are required to simplify anaemia management and reduce the burden on healthcare systems. There is increasing interest in extending the administration interval of ESAs. This would result in considerable time-savings, reducing the workload of healthcare providers and potentially reducing healthcare system costs. Time saved could be utilised in improving other aspects of patient care, such as implementation of guidelines, or treating more patients. Potential benefits of extended administration intervals for patients include a less demanding regimen and fewer injections, which could lead to improved adherence to treatment.

AIM

This article reviews studies of the efficacy of current ESAs in maintaining stable haemoglobin (Hb) levels when used at extended administration intervals of up to once monthly.

SUMMARY OF FINDING

Patients who are already stable on more frequent ESA therapy and who respond well to treatment may be able to maintain stable Hb with extended dosing regimens with established ESAs. However, few patients with CKD currently receive ESAs once-monthly in clinical practice. New agents with long half-lives offer the potential for extended dosing regimens in all patients with CKD.

Secondary analysis of the CHOIR trial epoetin-alpha dose and achieved hemoglobin outcomes

Trials of anemia correction in chronic kidney disease have found either no benefit or detrimental outcomes of higher targets. We did a secondary analysis of patients with chronic kidney disease enrolled in the Correction of Hemoglobin in the Outcomes in Renal Insufficiency trial to measure the potential for competing benefit and harm from achieved hemoglobin and epoetin dose trials. In the 4 month analysis, significantly more patients in the high-hemoglobin compared to the low-hemoglobin arm were unable to achieve target hemoglobin and required high-dose epoetin-alpha. In unadjusted analyses, the inability to achieve a target hemoglobin and high-dose epoetin-alpha were each significantly associated with increased risk of a primary endpoint (death, myocardial infarction, congestive heart failure or stroke). In adjusted models, high-dose epoetin-alpha was associated with a significant increased hazard of a primary endpoint but the risk associated with randomization to the high hemoglobin arm did not suggest a possible mediating effect of higher target via dose. Similar results were seen in the 9 month analysis. Our study demonstrates that patients achieving their target had better outcomes than those who did not; and among subjects who achieved their randomized target, no increased risk associated with the higher hemoglobin goal was detected. Prospective studies are needed to confirm this relationship and determine safe dosing algorithms for patients unable to achieve target hemoglobin.

Health-related quality of life in the era of erythropoietin

Patients with end-stage renal disease treated with maintenance hemodialysis suffer substantial impairments in health-related quality of life (HRQOL). Despite widespread efforts, there are few interventions that improve the overall well-being and quality of life of this patient population. The current review provides a description of HRQOL as an essential, yet arguably overlooked health-related domain in hemodialysis patients, and discusses interventions that have been evaluated to improve the functional status and well-being of this population, with a particular focus on therapy with recombinant human erythropoietin. We review the controversy surrounding recombinant human erythropoietin as it relates to HRQOL, and describe the delicate balance faced by renal providers who seek to reduce hemodialysis patients' morbidity and mortality while simultaneously striving to improve patients' HRQOL.

Use of erythropoiesis-stimulating agents in patients with anemia of chronic kidney disease: overcoming the pharmacological and pharmacoeconomic limitations of existing therapies

Stage 3 chronic kidney disease (CKD), which is characterized by a glomerular filtration rate of 30 to 60 mL/min/1.73 m2 (reference range, 90-200 mL/min/1.73m2 for a 20-year-old, with a decrease of 4 mL/min per decade), affects approximately 8 million people in the United States. Anemia is common in patients with stage 3 CKD and, if not corrected, contributes to a poor quality of life. Erythropoiesis-stimulating agents (ESAs), introduced almost 2 decades ago, have replaced transfusions as first-line therapy for anemia. This review summarizes the current understanding of the role of ESAs in the primary care of patients with anemia of CKD and discusses pharmacological and pharmacoeconomic issues raised by recent data. Relevant studies in the English language were identified by searching the MEDLINE database (1987-2006). Two ESAs are currently available in the United States, epoetin alfa and darbepoetin alfa. More frequent dosing with epoetin alfa is recommended by the labeled administration guidelines because it has a shorter half-life than darbepoetin alfa. Clinical experience also supports extended dosing intervals for both these ESAs. Use of ESAs in the management of anemia of CKD is associated with improved quality of life, increased survival, and decreased progression of renal failure. Some evidence suggests that ESAs have a cardioprotective effect. However, correction of anemia to hemoglobin levels greater than 12 g/dL (to convert to g/L, multiply by 10) appears to increase the risk of adverse cardiac outcomes and progression of kidney disease in some patients. The prescription of ESAs in the primary care setting requires an understanding of the accepted use of these agents, the associated pharmacoeconomic challenges, and the potential risks. This review considers the need to balance effective ESA dosing intervals against the potential risks of treatment.

Pathophysiology of anemia and erythrocytosis

An increasing understanding of the process of erythropoiesis raises some interesting questions about the pathophysiology, diagnosis and treatment of anemia and erythrocytosis. The mechanisms underlying the development of many of the erythrocytoses, previously characterised as idiopathic, have been elucidated leading to an increased understanding of oxygen homeostasis. Characterisation of anemia and erythrocytosis in relation to serum erythropoietin levels can be a useful addition to clinical diagnostic criteria and provide a rationale for treatment with erythropoiesis stimulating agents (ESAs). Recombinant human erythropoietin as well as other ESAs are now widely used to treat anemias associated with a range of conditions, including chronic kidney disease, chronic inflammatory disorders and cancer. There is also heightened awareness of the potential abuse of ESAs to boost athletic performance in competitive sport. The discovery of erythropoietin receptors outside of the erythropoietic compartment may herald future applications for ESAs in the management of neurological and cardiac diseases. The current controversy concerning optimal hemoglobin levels in chronic kidney disease patients treated with ESAs and the potential negative clinical outcomes of ESA treatment in cancer reinforces the need for cautious evaluation of the pleiotropic effects of ESAs in non-erythroid tissues.

Comparative Erythropoietin Receptor Binding Kinetics of C.E.R.A. and Epoetin-β Determined by Surface Plasmon Resonance and Competition Binding Assay

C.E.R.A., a continuous erythropoietin (EPO) receptor activator, has been developed to provide stable maintenance of hemoglobin levels at once-monthly dosing intervals and smooth and steady anemia correction. The comparative EPO receptor binding properties of C.E.R.A. and epoetin-beta were assessed by surface plasmon resonance using soluble recombinant EPO receptors and by competition binding on cultured UT-7 cells. Calculated equilibrium dissociation constants (surface plasmon resonance assay) for C.E.R.A. and epoetin-beta were 140 and 2.9 nmol/l, respectively. Respective IC(50) values (competition binding assay) were 200 and 1.5 nmol/l. Compared with epoetin-beta, C.E.R.A. has approximately 50- to 100-fold lower affinity for EPO receptor binding sites. Analysis of the equilibrium binding curves indicates that the difference in affinity is mainly due to slower association. The different receptor binding properties of C.E.R.A. may enable continuous stimulation of erythropoiesis and, combined with a long half-life and slow systemic clearance, permit administration at extended intervals.

The new FDA label for erythropoietin treatment: how does it affect hemoglobin target?

The erythropoietin analogs have been an important advance for the treatment of the anemia of kidney disease, resulting in reduced need for blood transfusion and improved quality of life. Recent studies, however, have indicated risks associated with targeting higher levels of hemoglobin (Hb). As a result, in March 2007, the US Food and Drug Administration (FDA) substantially changed prescribing information for these drugs to alert clinicians to these risks. In this review, we consider the recent literature, the change in FDA warnings, and new National Kidney Foundation Anemia Guidelines. Suggestions for new Hb targets during erythropoiesis-stimulating agent treatment are presented.

Implications of Neocytolysis for Optimal Management of Anaemia in Chronic Kidney Disease

Erythropoietin is the major hormone regulator of erythrocyte production promoting the survival, as well as the differentiation and maturation, of erythroid progenitor cells. In addition to these well-characterized effects, it appears that an erythropoietin-responsive non-erythroid mechanism also mediates the selective destruction of young circulating erythrocytes (neocytes) when red cell mass becomes excessive - a process termed 'neocytolysis'. Endothelial cells appear to respond to a rapid decrease in circulating levels of erythropoietin by secreting cytokines (including TGF-alpha), which signal reticuloendothelial phagocytes to destroy neocytes. The result is a more rapid decrease in red cell mass than can be explained by natural erythrocyte senescence alone. The current pharmacologic approach to treatment of anaemia in chronic kidney disease may cause neocytolysis and could keep therapy from reaching its full potential. Understanding neocytolysis and its relationship to fluctuating serum erythropoietin levels might help to better understand optimal treatment with erythropoietic agents.

HIF prolyl hydroxylase inhibition results in endogenous erythropoietin induction, erythrocytosis, and modest fetal hemoglobin expression in rhesus macaques

The hypoxia-inducible factor (HIF) pathway is crucial in mitigating the deleterious effects of oxygen deprivation. HIF-alpha is an essential component of the oxygen-sensing mechanisms and under normoxic conditions is targeted for degradation via hydroxylation by HIF-prolyl hydroxylases. Several HIF-prolyl hydroxylase inhibitors (PHIs) induced erythropoietin (epo) expression in vitro and in mice, with peak epo expression ranging from 5.6- to 207-fold above control animals. Furthermore, several PHIs induced fetal hemoglobin (HbF) expression in primary human erythroid cells in vitro, as determined by flow cytometry. One PHI, FG-2216, was further tested in a nonhuman primate model without and with chronic phlebotomy. FG-2216 was orally bioavailable and induced significant and reversible Epo induction in vivo (82- to 309-fold at 60 mg/kg). Chronic oral dosing in male rhesus macaques was well tolerated, significantly increased erythropoiesis, and prevented anemia induced by weekly phlebotomy. Furthermore, modest increases in HbF-containing red cells and reticulocytes were demonstrated by flow cytometry, though significant increases in HbF were not demonstrated by high-pressure liquid chromatography (HPLC). HIF PHIs represent a novel class of molecules with broad potential clinical application for congenital and acquired anemias.

Effect of a continuous erythropoietin receptor activator (C.E.R.A.) on stable haemoglobin in patients with CKD on dialysis: once monthly administration

AIMS

This Phase II study aimed to determine the optimal dose and administration schedule of continuous erythropoietin receptor activator (C.E.R.A.) given subcutaneously (s.c.) in patients receiving dialysis converting directly from s.c. epoetin therapy 1-3 times/week. An extension phase examined long-term safety and efficacy.

METHODS

Patients were assigned to one of three C.E.R.A. dose groups determined by multiplying the previous weekly dose of epoetin by one of three ratios (0.4/150, 0.8/150, 1.2/150 for groups A, B and C, respectively). Within each group, patients were randomized to once weekly (QW), once every 3 weeks (Q3W) and once monthly (Q4W) schedules. Dose adjustments were not permitted for the first 6 weeks. The core study period was 19 weeks (21 weeks in the Q4W cohorts). Patients could enter a 12-month extension period at the same schedule, aiming to maintain haemoglobin (Hb) at 11-12 g/dL.

RESULTS

137 patients entered the core period, and 62 continued into the extension period. A dose-dependent relationship was seen in the primary efficacy variable, change in Hb standardized to a 6 week period (p < 0.0001), but effect was independent of schedule. Hb levels were maintained throughout the study, with few dose changes. C.E.R.A. was generally well tolerated and the most frequent adverse event was hypotension.

CONCLUSION

The results suggest that s.c. C.E.R.A. at up to once monthly intervals provides stable maintenance of Hb levels in dialysis patients converting directly from epoetin 1-3 times/week. Achieving tight Hb control with few dose adjustments at extended administration intervals may offer health benefits and improvements in resource management.

What is needed to achieve a hemoglobin of 11.0-13.0 g/dl in end-stage renal disease

Effective treatment of anemia in end-stage renal disease (ESRD) results in reduced fatigue and improved quality of life. The National Kidney Foundation's 2006 anemia treatment guidelines recommend maintaining hemoglobin (Hb) at >11 g/dl, while noting that there is insufficient evidence to routinely maintain Hb levels > or =13.0 g/dl. Success in achieving Hb levels within these targets requires careful monitoring and adjustments to treatment. In addition, causes for diminished response and refractory anemia must be adequately evaluated. In this article, factors important for achieving Hb 11-13 g/dl in patients with ESRD are reviewed.