Pure red-cell aplasia and recombinant erythropoietin

Pure Red-Cell Aplasia “Epidemic”—Mystery Completely Revealed?

Starting in 1998, the number of pure red-cell aplasia (PRCA) cases in patients treated with recombinant human erythropoietin (rHuEPO) increased dramatically. Most cases were observed in patients treated with epoetin alfa produced outside the United States. The peak was observed in 2002; since then, the PRCA incidence has declined.

Many factors are likely to have contributed to this upsurge. The molecular structure of the various epoetins and patient characteristics do not seem to play a major role. The route of administration holds some importance, because most PRCA patients received rHuEPO subcutaneously. The peak of PRCA cases overlapped with the removal of human serum albumin from the Eprex formulation (Janssen-Pharmaceutica NV, Beerse, Belgium), for which polysorbate 80 and glycine were substituted. Polysorbate 80 may have increased the immunogenicity of Eprex by eliciting the formation of epoetin-containing micelles or by interacting with leachates released by the uncoated rubber stoppers of prefilled syringes. Compared with the previous formulation, the polysorbate 80 formulation has lower stability, making it more susceptible to stress conditions such as insufficient attention to the cold chain. This situation could facilitate protein denaturation or aggregate formation.

Uncoated rubber stoppers were replaced with coated stoppers, and the cold chain was reinforced; the Eprex formulation has remained unchanged.

Even though the incidence of PRCA returned to very low levels, discriminating the cause–effect relationship of a single action is difficult, given that all occurred with a similar chronology, and that PRCA develops after a relatively long exposure period. Careful observation of future trends of new PRCA cases is thus mandatory.

Updates on Novel Erythropoiesis-Stimulating Agents: Clinical and Molecular Approach

Erythropoietin (EPO) is an important hormone responsible for the stimulation of hematopoiesis which is impaired in a variety of diseases, such as chronic kidney disease, cancer chemotherapy, and the use of some anti-HIV drugs. Difficulties in the purification of endogenous EPO due to problems such as technical limitations, heterogeneity of target cells, inadequate amount and immunogenicity of the resultant product, had limited the entry of endogenous EPO in the clinical applications. The integration of medical biotechnology and hematology has introduced novel procedures for the production of human recombinant erythropoietin (rHuEPO), and other erythropoiesis-stimulating agents (ESAs). To investigate and produce rHuEPO, the first step is to recognize the molecular biology and functional pathways, structure, metabolism, and basic physiology of EPO. In this review, all clinical indications, side effects, challenges and notable points regarding EPO, rHuEPO, and other ESAs have also been addressed along with its molecular characterization, such as the modifications needed to optimize their rHuEPO biosynthesis.

Addressing barriers to effective cancer immunotherapy with nanotechnology: achievements, challenges, and roadmap to the next generation of nanoimmunotherapeutics

Cancer is a complex systemic disorder that affects many organs and tissues and arises from the altered function of multiple cellular and molecular mechanisms. One of the systems malfunctioning in cancer is the immune system. Restoring and improving the ability of the immune system to effectively recognize and eradicate cancer is the main focus of immunotherapy, a topic which has garnered recent and significant interest. The initial excitement about immunotherapy, however, has been challenged by its limited efficacy in certain patient populations and the development of adverse effects such as therapeutic resistance and autoimmunity. At the same time, a number of advances in the field of nanotechnology have sought to address the challenges faced by modern immunotherapeutics and allow these therapeutic strategies to realize their full potential. This endeavour requires an understanding of not only the immunological barriers in cancer but also the mechanisms by which modern technologies and immunotherapeutics modulate the function of the immune system. Herein, we summarize the major barriers relevant to cancer immunotherapy and review current progress in addressing these obstacles using various approaches and clinically approved therapies. We then discuss the remaining challenges and how they can be addressed by nanotechnology. We lay out translational considerations relevant to the therapies described and propose a framework for the development of next-generation nanotechnology-enabled immunotherapies.

CT-P13 in the treatment of rheumatoid arthritis

INTRODUCTION

The first biosimilar infliximab, CT-P13 infliximab-dyyb was approved in 2013 by the European Medicines Agency (EMA) and in 2016 by the United States Food and Drug Administration (FDA) and has been used for the treatment of rheumatoid arthritis (RA) for 4 years. Areas covered: CT-P13 with the three brand names on the market has highly similar efficacy and safety profiles but lower price than originator infliximab and are approved in more than 80 countries. One of the most important determinants of the implementation of CT-P13 in the treatment of RA is scientific evidence from clinical studies and real-world pharmacovigilance data. Here, we review all available clinical data supporting the similarity of CT-P13 to originator infliximab in its clinical efficacy and safety for the treatment of RA and related arthritis. In addition, we consider the role of CT-P13 in therapeutic strategies for RA treatment. Expert commentary: With its highly similar efficacy and safety profile to originator infliximab and its lower price, CT-P13 is expected to be very useful in RA treatment, whether it is applied earlier or switched from originator infliximab or other biologics. Future educational initiatives will be important to overcome misunderstandings about biosimilars and to improve the implementation of CT-P13.

An overview on safety issues related to erythropoiesis-stimulating agents for the treatment of anaemia in patients with chronic kidney disease

INTRODUCTION

Erythropoiesis stimulating agents (ESA) are effective drugs, which have been used for decades in patients with chronic kidney disease (CKD) with few side effects. More recently, concern has been raised around their safety, from higher cardiovascular and thrombosis risk to cancer progression and increased mortality.

AREAS COVERED

We made a literature search on PubMed looking for adverse effects of ESA in CKD patients. The topics covered are cardiovascular adverse events, thrombosis, increased mortality, hypertension, cancer progression, diabetic retinopathy, pure red cell aplasia and anaphylactic reactions.

EXPERT OPINION

Concerns around ESA therapy have questioned treatment indications in high-risk CKD patients (those with cancer, diabetes and cardiovascular comorbidities). A more cautious approach has then prevailed. In our opinion, intermediate Hb values (Hb 10-12 g/dl) should be aimed with ESA therapy, being more cautious in high-risk patients. As a consequence, IV iron is administered more frequently. However, excessive iron use may cause iron overload and in rare cases severe anaphylactic reactions. There are expectations of new erythropoietic agents, such as those manipulating the hypoxia-inducible transcription factors (HIF) system. Differing from ESAs, they stimulate the production of endogenous EPO, avoiding over-physiological plasmatic levels.

Pure red cell aplasia induced by epoetin zeta

Pure red cell aplasia (PRCA) may develop in patients with chronic kidney disease receiving erythropoiesis-stimulating agents (ESA). We report on a 72-year-old patient who developed hypo-proliferative anaemia unresponsive to ESA following the administration of epoetin zeta subcutaneously for 7 months. On the basis of severe isolated hypoplasia of the erythroid line in the bone marrow and high-titre neutralizing anti-erythropoietin antibodies (Ab), a diagnosis of Ab-mediated PRCA was made. Epoetin zeta was discontinued and the patient was given steroids. This was associated with anaemia recovery. To our knowledge this is the first PRCA case related to epoetin zeta.

Understanding the immunogenicity and antigenicity of nanomaterials: Past, present and future

Nanoparticle immunogenicity and antigenicity have been under investigation for many years. During the past decade, significant progress has been made in understanding what makes a nanoparticle immunogenic, how immune cells respond to nanoparticles, what consequences of nanoparticle-specific antibody formation exist and how they challenge the application of nanoparticles for drug delivery. Moreover, it has been recognized that accidental contamination of therapeutic protein formulations with nanosized particulate materials may contribute to the immunogenicity of this type of biotechnology products. While the immunological properties of engineered nanomaterials and their application as vaccine carriers and adjuvants have been given substantial consideration in the current literature, little attention has been paid to nanoparticle immuno- and antigenicity. To fill in this gap, we herein provide an overview of this subject to highlight the current state of the field, review past and present research, and discuss future research directions.

Association of Erythropoietin Dose and Route of Administration with Clinical Outcomes for Patients on Hemodialysis in the United States

BACKGROUND AND OBJECTIVES

Recombinant human erythropoietin (epoetin) is used routinely to increase blood hemoglobin levels in patients with ESRD and anemia. Although lower doses of epoetin are required to achieve equivalent hemoglobin responses when administered subcutaneously rather than intravenously, standard practice has been to administer epoetin to patients on hemodialysis intravenously. Randomized trials of alternative epoetin treatment regimens in patients with kidney failure have shown that risks of cardiovascular complications and death are related to the dose levels of epoetin used. Therefore, given the dose-sparing advantages of subcutaneous epoetin administration, the possibility that treatment of patients on hemodialysis with subcutaneous epoetin might be associated with more favorable outcomes compared with intravenous treatment was investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A retrospective cohort study of 62,710 adult patients on hemodialysis treated with either intravenous or subcutaneous epoetin-α and enrolled in the Centers for Medicare and Medicaid Services ESRD Clinical Performance Measures Project from 1997 to 2005 was carried out. Risks of death and/or hospitalization for cardiovascular complications (adverse composite event outcomes) during 2 years of follow-up were determined in relationship to epoetin dose and route of administration (intravenous versus subcutaneous) by multivariate Cox proportional hazard modeling adjusted for demographics and clinical parameters.

RESULTS

Epoetin doses used to achieve equivalent hemoglobin responses in study patients were, on average, 25% higher when epoetin was administered intravenously rather than subcutaneously (as expected). Moreover, adverse composite event outcomes were found to be significantly more likely to occur during follow-up for patients on hemodialysis managed with intravenous rather than subcutaneous epoetin (adjusted hazard ratio for adverse events within 1 year [intravenous versus subcutaneous] was 1.11 [95% confidence interval, 1.04 to 1.18]).

CONCLUSIONS

This study finds that treatment of patients on hemodialysis with subcutaneous epoetin is associated with more favorable clinical outcomes than those associated with intravenous epoetin treatment.

Strategies to compare clinical antitherapeutic antibody data when changing assay platforms: a case study

Zhihua Julia Qiu has over 20 years post PhD experience in academic institutes, pharmaceutical industry and biotechnology startup settings; focused on novel therapeutics discovery and development and diagnostic tools. She is currently a Scientist in the Bioanalytical Sciences department at Genentech; responsible for developing, evaluating and implementing Bioanalytical strategy to support protein therapeutics development. That includes assay development and validation to evaluate PK, antitherapeutic antibodies as well as biomarkers in both nonclinical and clinical studies for Immunology and Oncology indications. In addition, she has led the evaluation of multiple novel technology platforms and transitioning assay platform to enable continuous support for the development of protein therapeutics and antibody-drug conjugates.

Protein comparability assessments and potential applicability of high throughput biophysical methods and data visualization tools to compare physical stability profiles

In this review, some of the challenges and opportunities encountered during protein comparability assessments are summarized with an emphasis on developing new analytical approaches to better monitor higher-order protein structures. Several case studies are presented using high throughput biophysical methods to collect protein physical stability data as function of temperature, agitation, ionic strength and/or solution pH. These large data sets were then used to construct empirical phase diagrams (EPDs), radar charts, and comparative signature diagrams (CSDs) for data visualization and structural comparisons between the different proteins. Protein samples with different sizes, post-translational modifications, and inherent stability are presented: acidic fibroblast growth factor (FGF-1) mutants, different glycoforms of an IgG1 mAb prepared by deglycosylation, as well as comparisons of different formulations of an IgG1 mAb and granulocyte colony stimulating factor (GCSF). Using this approach, differences in structural integrity and conformational stability profiles were detected under stress conditions that could not be resolved by using the same techniques under ambient conditions (i.e., no stress). Thus, an evaluation of conformational stability differences may serve as an effective surrogate to monitor differences in higher-order structure between protein samples. These case studies are discussed in the context of potential utility in protein comparability studies.

Evaluating the immunogenicity of protein drugs by applying in vitro MHC binding data and the immune epitope database and analysis resource

The immune system has evolved to become highly specialized in recognizing and responding to pathogens and foreign molecules. Specifically, the function of HLA class II is to ensure that a sufficient sample of peptides derived from foreign molecules is presented to T cells. This leads to an important concern in human drug development as the possible immunogenicity of biopharmaceuticals, especially those intended for chronic administration, can lead to reduced efficacy and an undesired safety profile for biological therapeutics. As part of this review, we will highlight the molecular basis of antigen presentation as a key step in the induction of T cell responses, emphasizing the events associated with peptide binding to polymorphic and polygenic HLA class II molecules. We will further review methodologies that predict HLA class II binding peptides and candidate epitopes. We will focus on tools provided by the Immune Epitope Database and Analysis Resource, discussing the basic features of different prediction methods, the objective evaluation of prediction quality, and general guidelines for practical use of these tools. Finally the use, advantages, and limitations of the methodology will be demonstrated in a review of two previous studies investigating the immunogenicity of erythropoietin and timothy grass pollen.

Acquired red cell aplasia in association with the use of recombinant erythropoietin in chronic renal failure

Acquired pure red cell aplasia (PRCA) is a rare condition. Traditionally it has been described in association with various etiologies such as parvovirus B19 infection, auto-immune disorders and drugs. Immunologically mediated PRCA is by far the commonest cause in adults, particularly since 1998, when a marked increased incidence of PRCA was noted in chronic renal failure patients receiving subcutaneous (SC) recombinant erythropoietin (rEpo). Typically these patients had been given erythropoietin for correction of anemia of renal failure and subsequently present with severe transfusion dependent anemia. Most cases were associated with SC administration of human serum albumin (HSA) free erythropoieitin alfa product (Eprex). Early recognition and withdrawal of erythropoietin therapy is essential. Treatment with immunosuppressive therapy, particularly in conjunction with renal transplant results in good response with resolution in the majority of cases. The pathogenesis is related to interaction of multiple factors such as formulation change and improper storage leading to increased immunogenicity of the recombinant product. The incidence peaked in 2001 and 2002, subsequently dropping considerably from 2003. This can be explained by the institution of measures such as more stringent handling and storage conditions, improvements in formulation of HSA free Eprex and switch to intravenous (IV) administration for Eprex in dialysis patients. The evidence to date on this condition is summarized in this review.

Clinical development of biosimilars: an evolving landscape

Biosimilars, or similar biological medicinal products, can provide a meaningful option for patients and physicians provided they deliver the therapeutic value of a reference product at a more modest cost. Unlike generic small-molecule drugs that require primarily the demonstration of pharmaceutical equivalence, the complex nature of protein therapeutics warrants a rigorous evaluation of both pharmaceutical and therapeutic equivalence to the reference product in an abbreviated clinical program. Furthermore, the lack of comprehensive structure–activity relationship data increases the burden on appropriately designed human clinical studies with predefined acceptance criteria to demonstrate the absence of clinically meaningful differences between the biosimilar and reference product. Although a number of biosimilar proteins have been approved, especially in Europe, issues on substitutability, extrapolation to other disease indications, and selection of reference standards and comparators, remains to be standardized at a global level.

A peptide-based erythropoietin-receptor agonist for pure red-cell aplasia

BACKGROUND

We investigated whether a novel, synthetic, peptide-based erythropoietin-receptor agonist (Hematide, Affymax) can stimulate erythropoiesis in patients with anemia that is caused by antierythropoietin antibodies.

METHODS

In this open-label, single-group trial, we enrolled patients with chronic kidney disease who had pure red-cell aplasia or hypoplasia due to antierythropoietin antibodies and treated them with a synthetic peptide-based erythropoietin-receptor agonist. The agonist was administered by subcutaneous injection at an initial dose of 0.05 mg per kilogram of body weight every 4 weeks. The primary end point was a hemoglobin concentration above 11 g per deciliter without the need for transfusions.

RESULTS

We treated 14 patients with the peptide agonist for a median of 28 months. The median hemoglobin concentration increased from 9.0 g per deciliter (with transfusion support in the case of 12 patients) before treatment to 11.4 g per deciliter at the time of the last administration of the agonist; transfusion requirements diminished within 12 weeks after the first dose, after which 13 of the 14 patients no longer required regular transfusions. Peak reticulocyte counts increased from a median of 10x10(9) per liter before treatment to peak counts of greater than 100x10(9) per liter. The level of antierythropoietin antibodies declined over the course of the study and became undetectable in six patients. One patient who initially responded to treatment had a diminished hematologic response a few months later despite increased doses of the agonist and required transfusions again; this patient was found to have antibodies against the agonist. One patient died 4 months after the last dose of the agonist, and a grade 3 or 4 adverse event occurred in seven other patients during the study period.

CONCLUSIONS

This novel agonist of the erythropoietin receptor can correct anemia in patients with pure red-cell aplasia caused by antierythropoietin antibodies. (ClinicalTrials.gov number, NCT00314795.).

Immunogenicity of aggregates of recombinant human growth hormone in mouse models

Aggregation of recombinant therapeutic protein products is a concern due to their potential to induce immune responses. We examined the immunogenicity of protein aggregates in commercial formulations of recombinant human growth hormone produced by freeze-thawing or agitation, two stresses commonly encountered during manufacturing, shipping and handling of therapeutic protein products. In addition, we subjected each preparation to high-pressure treatment to reduce the size and concentration of aggregates present in the samples. Aggregates existing in a commercial formulation, as well as aggregates induced by freeze-thawing and agitation stresses enhanced immunogenicity in one or more mouse models. The use of high-pressure treatment to reduce size and concentrations of aggregates within recombinant human growth hormone formulations reduced their overall immunogenicity in agreement with the "immunon" hypothesis.

Immunogenicity of bone morphogenetic proteins

Object

The object of this paper is to review the immunogenicity of bone morphogenetic proteins (BMPs) and to compare the results of the immunogenicity characterization and clinical consequences between recombinant human (rh)BMP-2 and recombinant human osteogenic protein-1 (rhOP-1/BMP-7).

Methods

The immunogenicity of therapeutic proteins and its clinical effects were reviewed. The characteristics of BMPs were also described in terms of immunogenicity. The methods and results of antibody detection in various clinical trials of rhBMP-2 and rhOP-1 were compared, including the most recent studies using a systematic characterization strategy with both a binding assay and bioassay.

Results

Similar to all recombinant human proteins, rhBMPs induce immune responses in a select subgroup of patients. Adverse effects from this response in these patients, however, have not been reported with antibody formation to either rhBMP-2 or rhOP-1. Overall, the incidence of antibody formation was slightly higher in rhOP-1 trials than in rhBMP-2 trials.

Conclusions

Although they occur in a subgroup of patients, the immune responses against rhBMPs have no correlation with any clinical outcome or safety parameter. Clinicians, however, must be aware of the potential complications caused by the immunogenicity of BMPs until more studies clearly elucidate their safety.

Immunogenicity of biologically-derived therapeutics: assessment and interpretation of nonclinical safety studies

An evaluation of potential antibody formation to biologic therapeutics during the course of nonclinical safety studies and its impact on the toxicity profile is expected under current regulatory guidance and is accepted standard practice. However, approaches for incorporating this information in the interpretation of nonclinical safety studies are not clearly established. Described here are the immunological basis of anti-drug antibody formation to biopharmaceuticals (immunogenicity) in laboratory animals, and approaches for generating and interpreting immunogenicity data from nonclinical safety studies of biotechnology-derived therapeutics to support their progression to clinical evaluation. We subscribe that immunogenicity testing strategies should be adapted to the specific needs of each therapeutic development program, and data generated from such analyses should be integrated with available clinical and anatomic pathology, pharmacokinetic, and pharmacodynamic data to properly interpret nonclinical studies.

Biosimilar therapeutics-what do we need to consider?

Patents for the first generation of approved biopharmaceuticals have either expired or are about to expire. Thus the market is opening for generic versions, referred to as 'biosimilars' (European Union) or 'follow-on protein products' (United States). Healthcare professionals need to understand the critical issues surrounding the use of biosimilars to make informed treatment decisions.The complex high-molecular-weight three-dimensional structures of biopharmaceuticals, their heterogeneity and dependence on production in living cells makes them different from classical chemical drugs. Current analytical methods cannot characterize these complex molecules sufficiently to confirm structural equivalence with reference molecules. Verification of the similarity of biosimilars to innovator biopharmaceuticals remains a key challenge. Furthermore, a critical safety issue, the immunogenicity of biopharmaceuticals, has been highlighted in recent years, confirming a need for comprehensive immunogenicity testing prior to approval and extended post-marketing surveillance.Biosimilars present a new set of challenges for regulatory authorities when compared with conventional generics. While the demonstration of a pharmacokinetic similarity is sufficient for conventional, small-molecule generic agents, a number of issues will make the approval of biosimilars more complicated. Documents recently published by the European Medicines Agency (EMEA) outlining requirements for the market approval of biosimilars provide much-needed guidance. The EMEA has approved a number of biosimilar products in a scientifically rigorous and balanced process. Outstanding issues include the interchangeability of biosimilars and innovator products, the possible need for unique naming to differentiate the various biopharmaceutical products, and more comprehensive labelling for biosimilars to include relevant clinical data.

Epoetin-associated pure red cell aplasia: past, present, and future considerations

BACKGROUND

Since 1988, millions of patients have received epoetin products intravenously (IV) and subcutaneously. In 1998, epoetin-associated pure red cell aplasia (PRCA) was first reported and causation was attributed to formulations without human serum albumin (HSA), subcutaneous administration, and uncoated rubber stoppers.

STUDY DESIGN AND METHODS

Data on erythropoietin (EPO)-associated PRCA were obtained from the Food and Drug Administration (FDA), regulatory authorities in other countries, and the manufacturers of epoetin alfa, epoetin beta, and darbepoetin. The data included information on numbers of PRCA cases and estimated exposure-adjusted incidence rates by EPO product, anemia etiology, administration route, country of PRCA identification, and date reported.

RESULTS

In 1999, academicians in Paris identified 12 EPO-treated patients with antibody-mediated PRCA; 11 of these patients were on hemodialysis and had received subcutaneous Eprex (Johnson & Johnson). In 2002, authorities in Europe, Australia, Singapore, and Canada mandated Eprex by IV route to hemodialysis patients, and the relevant manufacturers added Teflon coating to prefilled syringes of Eprex; PRCA cases subsequently decreased by 90 percent. By 2003, 180 Eprex-associated PRCA cases were identified in Europe, Canada, Australia, and Asia, despite improvements in handling. Since 2002, FDA safety databases include information on 59 new cases of antibody-associated PRCA, primarily associated with subcutaneous epoetin alfa and darbepoetin that does not contain HSA.

CONCLUSION

Independent actions by regulatory authorities, manufacturers, and academic researchers identified significant numbers of PRCA cases between 1998 and 2003 and characterized the probable etiology. Today, antibody-mediated PRCA is an infrequent class toxicity occurring among some hemodialysis patients on EPOs.

New alternatives for erythropoietin therapy in chronic renal failure

Erythropoietin (EPO) is one of the main cytokines involved in the regulation of erythropoiesis. The main site of EPO production are the kidneys. An altered EPO production leads to pathological conditions such as anemia and polycythaemia. Due to the progressive loss of renal peritubular cells, patients with chronic kidney disease (CKD) have low EPO plasma levels. This decreases erythron stimulation with the direct consequence of developing anemia. Before the introduction in the clinical practice of rHuEpo, in the late 1980s, the only solution for treating this type of anemia were blood transfusions and anabolic steroids. Even rHuEpo has proven to be safe and effective for treatment of anemias, there are some concerns about its cost, the need for frequent parenteral administration, and development of anti-EPO antibodies. These inconveniences prompted the search for novel erythropoiesis stimulating agents. Different strategies lead to isolation or chemical synthesis of such agents as darbepoetin alfa and EPO mimetics. In this review, we present some general aspects of EPO biology, with emphasis on chronic renal failure, and expose some of the alternatives to EPO used for anemia correction.

Risks and benefits of erythropoiesis-stimulating agents in cancer management

Anemia is frequently diagnosed in patients with cancer and its treatment is an important clinical problem. The deficiency in red blood cells (RBCs) can be a debilitating problem, and anemia correlates with poor performance status, deteriorates quality of life, and may negatively influence the prognosis of cancer patients. The development of recombinant human erythropoietins (rhEPO) provides a therapeutic option in patients with mild to moderate anemia. However, clinical experience demonstrates that more than half of anemic cancer patients are not treated. There is clear evidence that rhEPO reliably increases haemoglobin (Hb) levels in patients suffering from cancer-related or treatment-associated anemia. The dosing and management of these patients should strictly follow evidence-based guidelines of the clinical societies, as well as the manufacturer's recommendations. Furthermore, treatment of patients beyond the correction of anemia must be regarded as potentially harmful and should only be conducted in an experimental clinical setting. In this review, recently published recommendations and standards for the use of rhEPO will be discussed.

Toxicity as a result of immunostimulation by biologics

The immune system has evolved highly effective mechanisms of surveillance and defense against foreign pathogens, and is also thought to act in surveillance and suppression of cancer. Thus, a predominant goal of immune system-based therapies is to normalize or enhance the host immune response in the areas of infectious disease and oncology. This review considers general approaches used for therapeutic immunostimulation, alterations in immune response mechanisms that occur with these treatments and the syndromes that commonly arise as a result of these changes. Because nonclinical studies of these therapies are conducted in animal models as the basis for predicting potential human toxicities, this review also considers the value of nonclinical testing to predict human toxicity.

An IL-7 fusion protein that shows increased thymopoietic ability

The role of IL-7 during thymopoiesis has led to it being the focus of a number of therapeutic interventions. However, its small size and pleiotropic nature present problems for thymus-directed therapies. We have created a fusion molecule between the extracellular N-terminal domain of CCR9 and IL-7, which has the potential to overcome these difficulties. This novel fusion protein retains the thymopoietic activity of IL-7 and the ligand-binding ability of CCR9. As a thymopoietic agent, compared with IL-7, it shows an enhanced retention in the thymus, increased de novo T cell production, and increased thymic output. Old mice receiving the fusion protein show improved CD8 T cell responses and reduced viral load after infection with influenza virus compared with those receiving IL-7. This chimeric molecule offers a novel therapeutic strategy that may result in the production of an effective immunorestorative agent.

Erythropoietin-alpha dosage requirements in a provincial hemodialysis population: effect of switching from subcutaneous to intravenous administration

BACKGROUND

The purpose of this initiative was to compare erythropoietin-alpha doses in hemodialysis patients who changed from subcutaneous to intravenous administration. The Manitoba Renal Program switched routes due to concern about erythropoietin-associated pure red cell aplasia.

METHODS

We compared the erythropoietin-alpha dosage requirements during subcutaneous administration (3 months pre-switch) and intravenous administration (months 4-6 post-switch). We also compared: hemoglobin, transferrin saturation (Tsat%), ferritin, and percent of patients receiving intravenous iron. The same erythropoietin-alpha regimen was initially used when patients were switched.

RESULTS

Of the 628 patients receiving erythropoietin-alpha, the data were complete for 400. The dose increased 26% (mean +/- SD, 10,425 +/- 7,330 vs. 13,125 +/- 8,638 IU/week; p < 0.0001), despite similar hemoglobin, (mean +/- SD, 11.5 +/- 1.1g/dl (114.9 +/- 11.2 g/l) vs. 11.3 +/- 1.0 g/dl (113.5 +/- 10.4 g/l); p = 0.0450) and iron parameters (Tsat 30.9%, ferritin 464 ng/ml (microg/l) vs. Tsat 28.7%, ferritin 538 ng/ml (microg/l)). For the subgroup of 84 patients who maintained target hemoglobin (10-11 g/dl or 110-120 g/l) for both periods, the dose increased 26% (mean +/- SD, 8,393 +/- 6,242 vs. 10,589 +/- 7,049 IU/week; p < 0.0001) without a change in hemoglobin, (mean +/- SD, 11.5 +/- 0.3 g/dl (115.2 +/- 3.0 g/l) vs. 11.5 +/- 0.3 g/dl (114.9 +/- 3.3 g/l); p = 0.5789). When stratified by subcutaneous dose, patients with the lowest dose (<5,000 IU/week) demonstrated the greatest increase (89%), and those with the highest dose (>20,000 IU/week) experienced no increase (-3%).

CONCLUSION

Overall, erythropoietin-alpha doses increased by 26% when patients were converted from subcutaneous to intravenous administration.

Recombinant human erythropoietin in the treatment of nonrenal anemia

Recombinant human erythropoietins (rhEPO) reliably increase hemoglobin levels in cancer patients experiencing chemotherapy-associated anemia. However, in patients with "anemia of cancer" not being treated with chemotherapy, rhEPO appears less effective. Recently, two studies have been broadly discussed which have raised concern on the concomitant use of erythropoietin and chemo- or radiation therapy in cancer patients. In addition, use of rhEPO is generally not considered cost-effective. Thus, the application of rhEPO should be limited to indications with proven clinical benefit. This review will provide an overview of the state of the art use of rhEPO in anemic patients and will discuss future developments.

[New indications for erythropoietin in clinical practice]

The utilization of rHuEp changed definitively the treatment and the natural history of anemia in patients with chronic renal insufficiency (CRI), and now is modifying the treatment of anemia of other non-renal patients as anemia of premature, anemia in onco-hematological illnesses, anemia in human immunodeficiency virus (HIV) infection, and for reduction of allogenic blood transfusions in surgery. We analyze briefly the clinical indications of rHuEpo and the possible complications secondary to its use.

Antibody-mediated side effects of recombinant proteins

This brief review is focused on the unwanted clinical effects mediated by antibodies against genetechnologically produced drugs. While many antibodies binding biotech-drugs may not be harmful, others may have deleterious clinical effects exposing patients to high risks. These antibodies can cause either lack of efficacy or hypersensitivity reactions. Examples for antibody-mediated lack of efficacy are inhibitors in hemophiliacs treated with Factor VIII, evidence of decreasing therapeutic efficacy of beta-interferons in MS-patients and pure red cell aplasia (PRCA) in patients with chronic renal failure treated with erythropoietin. Antibody-mediated hypersensitivity reactions have to be expected with all recombinant proteins. The mechanisms and causes of antibody production against biotech-drugs in patients are discussed.

Rationally engineered therapeutic proteins with reduced immunogenicity

Chronic administration of protein therapeutics may elicit unacceptable immune responses to the specific protein. Our hypothesis is that the immunogenicity of protein drugs can be ascribed to a few immunodominant helper T lymphocyte (HTL) epitopes, and that reducing the MHC binding affinity of these HTL epitopes contained within these proteins can generate drugs with lower immunogenicity. To test this hypothesis, we studied the protein therapeutic erythropoietin (Epo). Two regions within Epo, designated Epo 91-120 and Epo 126-155, contained HTL epitopes that were recognized by individuals with numerous HLA-DR types, a property common to immunodominant HTL epitopes. We then engineered analog epitopes with reduced HLA binding affinity. These analog epitopes were associated with reduced in vitro immunogenicity. Two modified forms of Epo containing these substitutions were shown to be bioactive and nonimmunogenic in vitro. These findings support our hypothesis and demonstrate that immunogenicity of protein drugs can be reduced in a systematic and predictable manner.

Pharmacotherapy of chemotherapy-induced anaemia

Anaemia in cancer patients is multifactorial. Anaemia of chronic disease due to the effects of cancer, as well as side effects of cancer treatment, are important factors. The impact of anaemia on the quality of life and social function of cancer patients has recently become more acknowledged. The traditional treatment for chemotherapy-induced anaemia (CIA) has been the use of red blood cell transfusions, with only short-lived effects and all their inherent risks. The finding of deficiency in erythropoietin, the endogenous hormone responsible for the production and maintenance of red blood cells in these patients, was the basis for the therapeutic development of erythropoietic proteins. With the introduction of epoetins (recombinant forms of human erythropoietin) in oncology and more recently, the novel long-acting darbepoetin alpha, physicians gained new pharmacotherapeutic approaches to treat CIA. Several forms of erythropoietic proteins are available in various regions of the world. Their characteristics, clinical evidence for use, guidelines for clinical administration and their safety are described in this review.

Expression, bioactivity, and clinical assessment of recombinant feline erythropoietin

OBJECTIVE

To determine the activity of recombinant feline erythropoietin (rfEPO) in murine bioassays and evaluate its efficacy and safety in cats with erythropoietin-dependent nonregenerative anemia.

ANIMALS

26 cats (group 1, 19 cats with anemia attributed to chronic kidney disease [CKD]; group 2, 7 cats with CKD and recombinant human erythropoietin [rhEPO]-induced red cell aplasia [RCA]).

PROCEDURE

The rfEPO was synthesized by use of Chinese hamster ovary (CHO) cells transfected with feline erythropoietin complementary DNA. Preclinical assessments of rfEPO included an erythroid cell proliferation assay and measurements of reticulocytosis in Balb/C mice. Clinical assessments of cats included hematologic, biochemical, and clinical examinations during 12 (group 1) or 6 (group 2) months of rfEPO treatment.

RESULTS

Biological activity of rfEPO was broadly equivalent to rhEPO in preclinical murine bioassays. Median Hct and absolute reticulocyte count in cats increased significantly during the first 3 weeks of rfEPO treatment, and median Hct generally could be maintained within a target range of 30% to 40% with periodic adjustments of rfEPO doses. Unexpectedly, 5 cats in group 1 and 3 cats in group 2 that initially responded to rfEPO treatment again developed anemia that was refractory to additional rfEPO treatments, even at higher doses.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment with rfEPO can reestablish active erythropoiesis in most cats with CKD, even those with anemia attributable to rhEPO-induced RCA. Unfortunately, development of RCA during treatment with CHO cell-derived recombinant erythropoietin proteins was not eliminated as a serious safety concern, even for this feline-specific preparation.

Pure red-cell aplasia caused by the antibody to recombinant erythropoietin, epoetin-beta, in a Japanese patient with chronic renal failure

A 68-year-old male with chronic renal failure and anemia received recombinant human erythropoietin (rHuEPO), epoetin beta, for approximately 1 year. Although the agent was initially effective for improving anemia, anemia refractory to EPO administration appeared and then worsened later, and pure red-cell aplasia (PRCA) was diagnosed. Anti-EPO antibody was detected by radioimmunoprecipitation (RIP) assay in the patient's serum. The antibody inhibited the proliferation of EPO-dependent cell line in a dose-dependent manner neutralizing EPO activity. The antibody also reacted with the other epoetin alfa products. The antibody did not recognize the carbohydrate moieties or denatured epoetin beta. The result suggested that the antibody recognized the conformational epitope of epoetin beta peptide molecule. Withdrawal of EPO and administration of cyclosporine decreased the titers of antibody; however, erythroid progenitor has not yet regenerated although the requirement for red blood cell transfusion is decreasing.

Differentiating factors between erythropoiesis-stimulating agents: a guide to selection for anaemia of chronic kidney disease

Endogenous erythropoietin (EPO) consists of a central polypeptide core covered by post-translationally linked carbohydrates. Three of the four currently available erythropoiesis stimulating agents (ESA)--epoetin-alpha, epoetin-beta and epoetin-omega- are composed of an identical amino acid sequence, but glycosylation varies as a result of type- and host cell-specific differences in the production process. Epoetin-alpha and epoetin-beta resemble each other with respect to molecular characteristics and pharmacokinetic data, although epoetin-beta has a higher molecular weight, a lower number of sialylated glycan residues and possibly slight pharmacokinetic advantages such as a longer terminal elimination half-life. A serious adverse effect of long-term administration of ESA is pure red cell aplasia. This effect has been observed predominantly with subcutaneous use of epoetin-alpha produced outside the US after albumin was removed from the formulation. In comparison with the intravenous route, subcutaneous administration of epoetin has been reported to have a dose-sparing effect in some studies. Epoetin-beta has been the subject of studies aimed at proving efficacy with a reduced administration frequency but results are not unequivocal. Epoetin-omega is produced in a different host cell than all other erythropoietic agents, hence glycosylation and pharmacokinetics are different. Small-scale clinical studies found epoetin-omega to be slightly more potent than epoetin-alpha. Epoetin-delta is a recently approved agent produced by human cells that are genetically engineered to transcribe and translate the EPO gene under the control of a newly introduced regulatory DNA sequence. However, epoetin-delta is not yet on the market and few data are available. The erythropoietin analogue darbepoetin-alpha carries two additional glycosylation sites that permit a higher degree of glycosylation. Consequently, in comparison with the other epoetins, darbepoetin-alpha has a longer serum half-life and a higher relative potency, which further increases with extension of the administration interval. Dosage requirements of darbepoetin-alpha do not appear to differ between the intravenous and subcutaneous routes of administration. The less frequent administration of darbepoetin-alpha in comparison to the other epoetins may reduce drug costs in the long term, but the variability in dosage or dosage frequency required within a single patient is high. Further studies should be aimed at defining predictors of the individual demand for erythropoietic agents, thereby allowing nephrologists to prescribe a cost-effective, individualised regimen.

Development and evaluation of a new ELISA for the detection and quantification of antierythropoietin antibodies in human sera

Assays for the analysis of antierythropoietin antibodies (anti-EPO Abs) currently suffer from a high degree of nonspecificity or are cumbersome and time consuming to perform. They are therefore not well suited for the analysis of large numbers of human sera samples, a task that has become increasingly important due to an increase in the number of patients developing anti-EPO Abs. The objective of this study was to develop and validate a sensitive and specific ELISA for the determination of anti-EPO Abs that would suit these purposes. In this new double antigen bridging ELISA, anti-EPO Abs bind via one site to recombinant human erythropoietin (rhEPO)-biotin immobilized to streptavidin-coated microtiter plates (MTPs) and by a second site to rhEPO labelled with digoxigenin (DIG). The amount of bound antibody is determined using an anti-DIG antibody coupled to peroxidase. A rabbit polyclonal anti-EPO Ab purified by immunoadsorption is used as reference antibody preparation. The dynamic range of this ELISA was 1-75 ng/ml per assay calibrated with the reference antibody preparation. The assay was specific for anti-EPO Abs and did not react with other immunoglobulins (Ig) present in human serum. The lower limit of detection (LLD) of the assay was 0.5 ng/ml, and the lower limit of quantitation (LLQ) was 1.0 ng/ml. Anti-EPO Abs could be detected in the sera of pure red cell aplasia (PRCA) patients. In contrast to previous reports, no anti-EPO Abs could be detected in the sera of patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS), or in the sera of dialysis patients.