Antibody-mediated Pure Red Cell Aplasia Research Articles

A detailed examination of the antibody prevalence and characteristics of anti-ESA antibodies

The antibody characteristics in erythropoiesis-stimulating agent (ESA)-treated patients who develop antibody-mediated pure red cell aplasia (PRCA; amPRCA) can be described as high-affinity, neutralizing anti-ESA antibodies with a mixed immunoglobulin G (IgG) subclass. The characteristics of an early-onset anti-ESA antibody response are not well documented, especially in the months prior to the development of amPRCA. Therefore, a detailed characterization of anti-ESA antibodies was performed in patients in both clinical studies and in a post-market setting. Both baseline and post-dose samples were tested and antibody-positive samples were characterized. Antibody characteristics such as concentration, isotype and specificity were evaluated in subjects with non-neutralizing anti-ESA antibodies and subjects that developed neutralizing anti-ESA antibodies associated with amPRCA. Serum samples were analyzed for the presence of anti-ESA antibodies, using a validated surface plasmon resonance (SPR)-based immunoassay or SPRIA. Among the clinical studies, pre-existing non-neutralizing anti-ESA antibodies were found in 6% of the subjects from clinical studies in nephrology, oncology and congestive heart failure (CHF). After ESA treatment, 2.3% of the subjects developed binding, non-neutralizing antibodies with 0.1% confirmed as having an IgG isotype and were specific to the ESA protein. IgM antibodies were detected at baseline and post-ESA treatment and reported to be specific to the glycosylation of the ESA. No clinical study subjects progressed to amPRCA. In contrast, anti-ESA antibody-positive subjects from the post-market setting with a confirmed IgG subclass were specific to the ESA protein. Subjects that had progressed to amPRCA were noted to have high antibody concentrations with neutralizing activity and a diverse IgG subtype. A low prevalence of non-neutralizing anti-ESA IgM specific to glycosylation on the ESA and IgG1 antibodies specific to the ESA protein was detected across all clinical patient populations. Patients with amPRCA were noted to have high IgG antibody concentrations, neutralizing antibodies and the presence of anti-ESA IgG4 antibodies.

Development and characterization of a human antibody reference panel against erythropoietin suitable for the standardization of ESA immunogenicity testing

Recombinant human erythropoietin (EPO) has been used therapeutically for more than two decades in the treatment of anemia. Although EPO is generally well tolerated, in rare cases, patients have developed anti-EPO antibodies that can negatively impact safety and efficacy. Therefore, the detection of antibodies against EPO is a regulatory requirement during clinical development and post-approval. Although it is a rare phenomenon, antibody-mediated pure red cell aplasia (PRCA) is a serious complication than can result from antibodies that develop and neutralize EPO as well as endogenous erythropoietin.Currently, there are no universally accepted analytical methods to detect the full repertoire of binding and neutralizing anti-EPO antibodies. A number of different methods that differ in terms of antibodies detected and assay sensitivities are used by different manufacturers. There is also a lack of antibody reference reagents, and therefore no consistent basis for detecting and measuring anti-EPO antibodies. Reference reagents, with established ranges, are essential to monitor the safety and efficacy of all erythropoiesis-stimulating agents (ESAs) structurally related to human erythropoietin.This is the first report of the development and characterization of a panel of fully human antibodies against EPO suitable as reference reagents. The characteristics of antibodies within the panel were selected based on the prevalence of non-neutralizing IgG and IgM antibodies in non-PRCA patients and neutralizing IgG antibodies, including IgG1 and IgG4, in antibody-mediated PRCA subjects. The reference panel includes antibodies of high- and low-affinity with binding specificity to neutralizing and non-neutralizing erythropoietin epitopes. The subclass of human antibodies in this reference panel includes an IgG1, IgG2, and IgG4, as well as an IgM isotype. This antibody panel could help select appropriate immunogenicity assays, guide validation, and monitor assay performance. Further, this human anti-ESA antibody panel may help set the limits of each assay platform in terms of the full repertoire of the anti-ESA antibodies, and may facilitate standardization of ESA immunogenicity reporting across assay platforms.

Antibody-mediated pure red cell aplasia in chronic kidney disease patients receiving erythropoiesis-stimulating agents: new insights

Antibody-mediated pure red cell aplasia is a very rare but devastating condition affecting patients receiving treatment with erythropoiesis-stimulating agents. New cases continue to emerge, generally in clusters, consistent with an 'environmental' trigger to its pathogenesis. Defining the causes of antibody-mediated pure red cell aplasia is clearly of importance for patients with chronic kidney disease, but any developments in this area may also have relevance to other disease areas as therapeutic delivery of endogenous proteins rapidly increases. This review focuses on the current knowledge regarding the etiology of antibody-mediated pure red cell aplasia and the current approach to therapy.

Impact of ribavirin dose reduction during treatment in chronic hepatitis C genotype 1 patients

Impact of ribavirin dose reduction during treatment in chronic hepatitis C genotype 1 patients

Early onset of anti- erythropoietin antibody-mediated pure red cell aplasia after commencement of subcutaneous administration of epoetin-β

Early onset of anti- erythropoietin antibody-mediated pure red cell aplasia after commencement of subcutaneous administration of epoetin-β

Detection of anti-ESA antibodies in human samples from PRCA and non-PRCA patients: an immunoassay platform comparison

The immunological methods for detecting antibodies to erythropoiesis-stimulating agents (ESAs) differ in assay sensitivity. However, this parameter, routinely determined in clinical assays using a high-affinity non-human polyclonal antibody, gives a one-dimensional assessment of antibody detection. We compare three widely used immunological methods and evaluate the ability of each to detect mature human antibodies and human antibodies characteristic of an early immune response. The detection of anti-ESA antibodies was compared between a radioimmunoprecipitation (RIP) assay, an electrochemiluminescence (ECL) bridging enzyme-linked immunosorbent assay and a surface plasmon resonance (SPR)-based immunoassay. All three methods were validated for sensitivity, specificity and precision. Specimens from clinical studies or post market testing were categorized as pure red cell aplasia (PRCA) or non-PRCA and then analyzed in each method. Among the antibody-mediated PRCA samples, which contain high affinity neutralizing antibodies, there was strong correlation between all methods. The results from non-PRCA sample analysis show high correlation between RIP and ECL methods; however, differences between the SPR immunoassay and the ECL and RIP were demonstrated. The samples that scored positive in the SPR immunoassay and negative by RIP and ECL were characterized to be of low antibody concentration, contained a high percentage of rapidly dissociating antibodies, or were antibodies of the IgM isotype. All three immunological methods are appropriate for detection of antibodies associated with antibody-mediated PRCA. However, the SPR immunoassay platform detected an early, low affinity IgG and IgM antibody response as well as detected and characterized a pathogenic antibody response associated with antibody-mediated PRCA.

Biosimilars: Is absence of proof of difference, proof of absence of difference?

Biosimilars have been available for a short period of time in hematology-oncology, and prescribing physicians have been wondering about their similarity in terms of safety and efficacy compared with standard comparator. In general, the market penetration in various countries is very similar to that of generic drugs, following prescription habits of the medical profession, variously dependent on the financial and administrative pressures of the country’s environment. A major difference compared to generics is that for biosimilars, before marketing, the European Medicines Agency (EMEA) and the US Food and Drug Administration (FDA) require producers to carry out additional clinical trials for efficacy and safety, as well as formal postmarketing surveillance. These requirements are therefore fulfilled at the time of marketing, at least in those countries dependent on these regulatory authorities. The European Union (EU) has developed a legal basis for biosimilars. EMA regulations require that the reference product be authorized in the EU. If this is also the case for other non-EU countries, it could require duplication of studies for each region. International guidelines can facilitate bringing to market and approvals. The World Health Organisation (WHO) has and is developing EU-similar procedures, as are many countries. It is interesting that Australia more or less adopted EMA regulations for biosimilars in 2008. With regards to the original natural human product, standard drugs produced by genetic engineering are already biosimilars. Over time, due to technical changes in cell cultures and other changes, these have also changed and are not necessarily identical to the initially marketed product (various insulins, erythropoietin [EPO], granulocytopoietins, thrombopoietins, etc.). Standard generic drugs were accepted a few years ago, albeit with some difficulties, and the discussion of biosimilars is a different one. In this issue of “Targeted Oncology”, a panel of international authors explores various regulatory, clinical and economic aspects. The topics are of direct interest to hematologists and oncologists. The area of biosimilars started in other medical areas with insulin, human growth hormone, etc., and will develop more in hematology and oncology in the near future with monoclonal antibodies and others. For presently available biosimilars, a measurable endpoint is, for the most part, proof of efficacy. For instance, for EPO, the standard parameter of response is the hemoglobin level, and the other aspects of this cytokine’s effects on angiogenesis, apoptosis, cellular differentiation, etc., are clinically less marked. Nevertheless, lately the association with thromboembolic disorders, possibly secondary to the effect on vascular endothelium has been widely discussed. The same applies to an effect on tumor progression that is still not fully settled. Long-term follow-up is necessary, due to the fact that, as seen in the present example, years after usage an unexpected adverse effect in relation to a production change, such as antibody-mediated pure red blood cell aplasia, has been noted. The example of low molecular weight heparins (LMWH) demonstrates other practical and conceptual difficulties. Heparins have a pleotrophic effect. Measuring the effect of LMWH is not limited to pharmacokinetics or pharmacodynamics laboratory parameters. It is not enough to determine This article is a modified reprint of Dicato M (2011) Biosimilars: Is absence of proof of difference, proof of absence of difference? Oncologie 13:181–182

Quantification of the preexisting CD4 T-cell repertoire specific for human erythropoietin reveals its immunogenicity potential

Antibody-mediated pure red cell aplasia is a rare but serious event resulting from the induction of neutralizing erythropoietin (Epo)-specific antibodies provoked by treatment with recombinant Epo. Because of the crucial role of CD4 T cells in humoral response, we have quantified the number of Epo-specific CD4 T cells in the blood of normal donors by in vitro stimulation. An important repertoire of preexisting Epo-specific T cells was observed in almost half of the donors, comparable with that of non-self-proteins. This observation suggests that, at the steady state, endogenous Epo weakly contributes to tolerance induction and may be ignored by the immune system. As a result, circulating Epo-specific CD4 T cells could be prone to be activated by altered batches of Epo, providing them with costimulatory signals. Our data also highlight the relevance of T-cell assays performed with normal donors to evaluate the potential immunogenicity of therapeutic proteins.

Detection of circulating antierythropoietin antibodies in patients with end stage renal disease on regular hemodialysis

Recombinant human erythropoietin (rHuEPO) has been successfully and safely used to treat anemia in patients with end stage renal disease (ESRD). The safety profile of rHuEPO had been considered to be excellent with possible exception of hypertension and increased risk of dialysis access thrombosis. Recently, antibody-mediated pure red cell aplasia associated with administration of rHuEPO has been identified as a cause of major concern; we aimed to detect and evaluate the presence of anti-EPO antibodies in patients with ESRD on regular dialysis who are using rHuEPO. Serum anti-EPO antibodies were detected by enzyme-linked immunosorbant assay technique in a total of 90 patients who are currently on regular hemodialysis and using rHuEPO alpha subcutaneously for more than 6 months. All patients were subjected to full history taking and clinical examination. Complete blood count, reticulocytes count, serum creatinine, blood urea, serum albumin, serum ferritin, and hepatitis markers were performed for all patients. Our results showed that 35 patients (38.9%) had the anti-EPO antibodies in their blood, while 55 patients (61.1%) did not have the circulating antibodies. The mean hemoglobin (Hb) level was significantly lower in the antibody positive group (8.8 g/dl +/- 1.35) than in the antibody negative group (9.42 g/dl +/- 1.32) (P = 0.000). The reticulocytes count was also significantly much lower in the patients who had anti-EPO antibodies with mean of (1.99 +/- 1.14) vs. (3.15 +/- 0.89) in the antibody negative (P = 0.000). The dose of EPO administrated in both studied groups was insignificantly different. The incidence of anti-EPO antibodies is high in ESRD patients on maintenance hemodialysis. Its presence is associated with increased incidence of anemia possibly due to immune-mediated inhibition of erythropoiesis as evidenced by reticulocytopenia.

Anti-epoetin-antibody-induced anemia in a child with chronic renal failure

Sirs, Recombinant human erythropoietin was introduced in 1988 for the treatment of anemia in chronic kidney disease (CKD). The development of antibodies against epoetin was a rare complication during the first decade of its use. However, in 1998 there was a sudden increase in epoetin-induced antibodies associated with pure red cell aplasia (PRCA) in patients with CKD who had been using Eprex, a subcutaneous epoetin-alfa product marketed in Europe [1, 2]. Although the recombinant epoetin products differ in glycosylation, the increase in PRCA was probably caused by a change in the formulation of Eprex in which human serum albumin was replaced by glycine and polysorbate 80 [3]. Switching patients from subcutaneous to intravenous administration and adding Teflon to the rubber stopper of prefilled Eprex syringes subsequently eliminated nearly all antibody formation. For epoetin-beta, antibody-associated PRCA is even rarer, as evidence by the very few cases that have been published. We present here the first report of a child who developed antibody-associated PRCA elicited by the use of epoetin-beta. The patient was born on the Dutch Antilles. In 2004, at the age of 5 years, he developed renal failure due to persistent obstructive uropathy. His CKD-related anemia was treated with epoetin-beta subcutaneously from 2004 onwards (2 × 2000 IE/week). After 1.5 year of use, he developed a progressive transfusion-dependent anemia unresponsive to recombinant epoetin-beta (Neorecormon: maximum 5 × 2000 IE/week) and presented at our hospital (Fig. 1). An increase in the epoetin-beta dose to 5 × 6000 IE/week had no effect on the reticulocyte count, demonstrating that the anemia was unresponsive to epoetin-beta. Fig. 1 Treatment regimen of progressive transfusion-dependent anemia unresponsive to recombinant epoetin-beta in our young patient with chronic kidney failure. Hb hemoglobin Laboratory testing revealed the following: hemoglobin (Hb), 2.8 mmol/L; reticulocyt count, <0.1%; MCV, 83; white blood cells (WBC), 11.7 × 109/L; platelet count, 228 × 109/L. There were no signs of hemolysis: lactate dehydrogenase, 184 U/L; haptoglobin, 0.99 g/L. The combination of anemia, low reticulocyte count, and normal leukocyte and trombocyte count with the use of epoetin-beta suggested a diagnosis of antibody-mediated PRCA. Anti-epoetin immunoglobulin (Ig) G antibodies identified by means of an antigen binding assay, essentially as described by Aalberse et al. [4], were indeed elevated. Treatment was initiated with one pulse methylprednisolone (15 mg/kg), followed by prednisone 1 mg/kg/day, and cyclosporine 4 mg/kg/day (trough levels 50–100 mg/l). Within days of starting this treatment, anti-epoetin-antibodies levels declined and were undetectable after 2 months of treatment (Fig. 1). The reticulocyte count increased to 2% after 3 months, and from then on Hb remained at acceptable levels between 5 and 7 mmol/L without the need for blood transfusions (Fig. 1). After 3 months, the prednisone dosage was reduced to 7.5 mg (0.3 mg/kg/day) and the cyclosporine dosage to 3 mg/kg/day until transplantation. One year later a successful family kidney transplantation was performed, and Hb was stable at 6.5 mmol/L 4 months after transplantation (Fig. 1). This 5-year-old boy developed PRCA caused by anti-epoetin-antibodies following exclusive treatment with epoetin-beta subcutaneously. The subcutaneous administration of epoetin may have rendered the immune system of this boy more susceptible to antibody formation. Treatment options for antibody-associated PRCA are invariably based on case reports or case-series. Several immunosuppressive drugs have been tried: corticosteroids alone, cyclophosphamide, cyclosporine, mycophenolate mofetil, intravenous immunoglobulin, and anti-CD20 monoclonal antibodies, with or without corticosteroid treatment. Although the results of different strategies vary, all patients who had a kidney transplant showed a full recovery of erythropoiesis [5]. Our patient responded well to a pulse of methylprednisolone followed by prednisone and low-dose cyclosporine. After this treatment the Hb remained stable, indicating the permanent disappearance of antibodies. No side-effects of our treatment were noted, and a successful renal transplantation was ultimately performed. In conclusion, the combination of prednisone and cyclosporine in a low dose was successful in the treatment of anti-epoetin-antibody-induced anemia in a child with chronic renal failure.

Evaluation of the Immuno-Stimulatory Potential of Stopper Extractables and Leachables by Using Dendritic Cells as Readout

Recombinant protein pharmaceuticals may bear some risks and undesirable side effects, such as the appearance of immunogenic reactions. The increased incidence of antibody-mediated pure red cell aplasia (PRCA) outside the United States after administration of a human serum albumin (HSA)-free EPREX® (recombinant human erythropoietin alpha) formulation was explained with the generation of rubber stopper related leachables, possibly acting as immunogenic adjuvants. In our study, we have investigated the potential of extractable and leachable preparations of three different pharmaceutical relevant stoppers to generate a “danger signal” in a dendritic cell assay. Furthermore, the investigated extractable and leachable preparations were characterized by NMR and a micelle-based polysorbate quantification method. In summary, we could demonstrate that stopper extractables, either generated by extraction or by leaching conditions, were not acting as danger signals for dendritic cells. Instead we identified degradation products of polysorbate 80, oleic acid and follow-up products, occur only under very accelerated conditions (100°C for 4 days) as a potential stimulator for these immune cells. As this degradation did not occur at real-time, the authors however do not consider their finding to be linked to any direct safety implications of polysorbate-containing formulations in clinical practice. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3548–3561, 2009

Current and Upcoming Erythropoiesis-Stimulating Agents, Iron Products, and Other Novel Anemia Medications

Treatment for anemia has come a long way in the last 20 years since the first recombinant human erythropoietins were licensed for the management of anemia in chronic kidney disease. The first-generation epoetins were succeeded by the development and production of a longer-acting erythropoietin (EPO) analog, darbepoetin alpha, which allowed less frequent dosing, usually once weekly or once every 2 weeks. More recently, another EPO-related molecule has been manufactured called Continuous Erythropoietin Receptor Activator with an even longer half-life, and although for patent reasons this is not available in the United States, it is licensed and is already being used in Europe. Other molecules are in development or are becoming licensed in Europe, including biosimilar epoetin products/follow-on biologics, and elsewhere in the world there are cheaper-production "copy" epoetins. Indeed, it is estimated that up to 80 such products may be sold in countries with less stringent regulatory control of pharmaceutical products. Two different biosimilar epoetins have already been licensed in Europe, one under 2 different brand names and one under 3 different brand names, and others may follow. Hematide is a synthetic peptide-based EPO receptor agonist that, interestingly, has no structural homology with EPO, and yet is still able to activate the EPO receptor and stimulate erythropoiesis. This agent is currently in phase III clinical trials. Research continues for orally active antianemic therapies, and several strategies are being investigated, although none is imminently available. Two new intravenous iron preparations have recently been developed, one in the United States (Ferumoxytol; AMAG Pharmaceuticals, Inc., Cambridge, MA) and one recently licensed in Europe (ferric carboxymaltose [Ferinject; Vifor Pharma, Zurich, Switzerland]). In conclusion, the development of effective therapies for the treatment of anemia has been a highly active field, both scientifically and economically, over the last two decades.

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

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. 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. 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. 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.

Epoetin-induced pure red cell aplasia: diagnosis and treatment

Antibody-mediated pure red cell aplasia is now recognized as a rare complication of erythropoiesis-stimulating agent therapy. The incidence of this adverse effect peaked in 2002, but new cases still appear sporadically. The aim of this review is to discuss the latest opinions regarding the detection and management of this condition. The diagnosis of classical erythropoiesis-stimulating agent induced pure red cell aplasia is made by a constellation of clinical features, including severe transfusion-dependent anaemia, reticulocytopenia, low or absent erythroblasts in the bone marrow, and the presence of circulating antierythropoietin antibodies. Recently, some cases have been reported in which the bone marrow findings show red cell hypoplasia rather than aplasia; this may represent earlier presentations of the same condition. Management of pure red cell aplasia as a complication of erythropoiesis-stimulating agent therapy consists of stopping the drug and implementing an immunosuppressive regimen to reduce or abolish erythropoietin antibody production. A recent animal study suggested that a possible alternative strategy may be to administer a novel peptide-based erythropoietin receptor agonist called Hematide that does not cross react with antierythropoietin antibodies, and will allow ongoing stimulation of erythropoiesis; this is the subject of a current clinical trial.

Feasibility of a Multiplex Flow Cytometric Bead Immunoassay for Detection of Anti-Epoetin Alfa Antibodies

Immunogenicity profiles of recombinant therapeutic proteins are important to understand because antibodies raised against these molecules may have important clinical sequelae. The purpose of the present study was to demonstrate that a flow cytometric bead array could be used to detect clinically relevant antibodies with specificity to such therapeutics. We chose to evaluate well-characterized specimens from persons treated with epoetin alfa that developed antibody-mediated pure red blood cell aplasia as a means to demonstrate the utility of this platform. Our data show that this assay is capable of detecting anti-epoetin alfa antibodies with a relative antibody concentration of 50 ng/ml, where 25 of 25 sera spiked with antibodies at this concentration scored positive. Moreover, the assay was designed to include positive and negative control beads for each specimen that is processed to ensure the specificity of the signal when detected. Measurement of interassay precision supports quantitative estimates of relative antibody concentrations in the range of 313 to 5,000 ng/ml, where the percent coefficient of variation did not exceed 20%. With respect to clinical specimens, antibodies with specificity for epoetin alfa could be easily detected in a set of specimens from persons with pure red blood cell aplasia that had prior exposure to the EPREX brand of recombinant epoetin alfa. Further development and validation of this approach may facilitate successful widespread application of the method for detection of anti-epoetin alfa antibodies, as well as antibodies directed against other recombinant therapeutic proteins.

Erythropoiesis‐stimulating agent hyporesponsiveness (Review Article)

Approximately 5-10% of patients with chronic kidney disease demonstrate hyporesponsiveness to erythropoiesis-stimulating agents (ESA), defined as a continued need for greater than 300 IU/kg per week erythropoietin or 1.5 mug/kg per week darbepoetin administered by the subcutaneous route. Such hyporesponsiveness contributes significantly to morbidity, mortality and health-care economic burden in chronic kidney disease and represents an important diagnostic and management challenge. The commonest causes of ESA resistance are non-compliance, absolute or functional iron deficiency and inflammation. It is widely accepted that maintaining adequate iron stores, ideally by administering iron parenterally, is the most important strategy for reducing the requirements for, and enhancing the efficacy of ESA. There have been recent epidemiologic studies linking parenteral iron therapy to an increased risk of infection and atherosclerosis, although other investigations have refuted this. Inflammatory ESA hyporesponsiveness has been reported to be improved by a number of interventions, including the use of biocompatible membranes, ultrapure dialysate, transplant nephrectomy, ascorbic acid therapy, vitamin E supplementation, statins and oxpentifylline administration. Other variably well-established causes of ESA hyporesponsiveness include inadequate dialysis, hyperparathyroidism, nutrient deficiencies (vitamin B12, folate, vitamin C, carnitine), angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aluminium overload, antibody-mediated pure red cell aplasia, primary bone marrow disorders, myelosuppressive agents, haemoglobinopathies, haemolysis and hypersplenism. This paper reviews the causes of ESA hyporesponsiveness and the clinical evidence for proposed therapeutic interventions. A practical algorithm for approaching the investigation and management of patients with ESA hyporesponsiveness is also provided.

Anti-erythropoietin antibody–mediated pure red cell aplasia in a living donor liver transplant recipient treated for hepatitis C virus

After liver transplantation, reinfection of the newly engrafted liver with hepatitis C virus is essentially universal in patients who are viremic at the time of transplantation. Treatment with interferon preparations with or without ribavirin is recommended in patients with marked histologic injury; however, hematologic toxicity associated with therapy has been reported, which is usually treated with growth factor support, including erythropoietin analogues. We present the first reported case of anti-erythropoietin antibody-mediated pure red cell aplasia arising in the setting of hepatitis C virus therapy in a patient who underwent living donor liver transplantation.

Antibody-mediated pure red cell aplasia in a dialysis patient receiving darbepoetin alfa as the sole erythropoietic agent

Antibody-mediated pure red cell aplasia in a dialysis patient receiving darbepoetin alfa as the sole erythropoietic agent

Antibody-mediated pure red cell aplasia in a dialysis patient receiving darbepoetin alfa as the sole erythropoietic agent

The introduction of recombinant human erythro-poietin (epoetin) transformed the management ofanaemia for the vast majority of dialysis patients.The immediate benefit of transfusion-independencewas a lower risk of contracting blood-borne infectionsand iron overload. The raised haematocrit ledto improvements in quality of life, which in turn hasbeen associated with improved long term survival [1,2].For the first decade or so, various brands orformulations of epoetin were available, includingepoetin alfa (Epogen, Procrit in the US; Eprex,Erypro in Europe). A second-generation erythropoieticagent (darbepoetin alfa) was developed by incorporat-ing an additional two glycosylation chains to theerythropoietin molecule, resulting in a product with alonger half-life and a consequent reduced dosingfrequency [3].Since 1998, there has been a rapid increase in theincidence of epoetin therapy-associated pure red cellaplasia (PRCA), largely associated with the Eprexbrand of epoetin, but described with the Epogen andNeoRecormon brands of epoetin. In 2002, Casadevallet al. [4] described a new complication of epoetintherapy, that of PRCA associated with anti-erythropoietin antibodies.To date, however, no cases of anti-erythropoietinmediated PRCA has been described with darbepoetinalfa, and indeed it has been suggested that theadditional glycosylation may cause this molecule tobe more resistant to antibody generation than epoetin.We describe what we believe to be the first case ofantibody-mediated PRCA associated with the admin-istration of darbepoetin alfa alone.

Multiple Cause of Loss of Recombinant Erythropoietin Efficacy: Physicians Beware.

Introduction: Loss of response to recombinant erythropoietin is a rare event typically seen only in the setting of iron deficiency or serious blood dyscrasia. In 2004, the Research on Adverse Drug Events and Reports group reported on 191 cases of antibody-mediated pure red cell aplasia (PRCA) primarily associated with the human albumin free formulation of Eprex. There were no reports of loss of response to darbepoetin alfa at that time. Since 2004, additional causes of loss of efficacy of epoetin therapy have been identified or described in detail.Methods: Data were obtained from the FDA's adverse event reporting system (AERS), and published literature, both medical and non-medical.Results: In the AERS system, we found nine reports of patients who developed anti-erythropoietin antibodies after exposure to darbepoetin alfa, seven of which occurred after recent exposure to Eprex. All of these patients received darbepoetin alfa for the anemia of chronic kidney disease (CKD). We also identified eight cases of loss of efficacy due to counterfeit epoetin in the literature and AERS reports. All of these patients received epoetin alfa for an indication other than anemia of CKD. Of the seven counterfeit cases found in AERS, five were reported by pharmacists, one by a consumer, and one by a nurse. In contrast, more than 90% of the 191 initial cases of antibody-mediated PRCA and all 9 cases associated with darbepoietin alfa were reported by physicians. Three cases of exposure to counterfeit epoetin in our series were linked to a single counterfeit supplier. Only two of these three cases were found in AERS out of an estimated 25,000–75,000 patients exposed to epoetin vials from that counterfeit supplier, for a reporting rate of less than 1/12,000 (.01%). This is lower than the estimated reporting rate for all adverse events of 1% to 10%, and markedly lower than the 90% or greater estimated reporting rate for antibody associated PRCA.Conclusion: Physicians should be aware of multiple the multiple possible etiologies for decreased recombinant erythropoietin efficacy, including the possible link between darbepoetin alfa and antibody mediated PRCA in patients with CKD. In addition, loss of efficacy related to counterfeit recombinant erythropoietin should be considered, especially in patients with anemia from conditions other than CKD. Underreporting of counterfeit epoetin exposure occurred despite the fact that “dear doctor” warning letters were sent to physicians at the time of two major counterfeit events. Unlike the warning letters for antibody-mediated PRCA, these letters did not contain information about clinical signs and symptoms that could be observed or elicited from patient history. In the future, warning letters for counterfeit pharmaceutical products should describe the potential clinical effects of the counterfeit medications in an effort to improve reporting and tracking of counterfeit medications through AERS.Table of Findingsdarbepoetin alfaepoetin alfa/betacounterfeit epoetin alfaNumber of cases91918Causality establishedNoYesYesReported by MD100%>90%0%Reported in AERS100%95%88%Clinical findingsLoss of Efficacy, rapid onset anemia, transfusion requirementLoss of efficacy, rapid onset anemia, transfusion requirementLoss of efficacy, slow onset anemia, may need transfusionClinical findings described in warning letterYesYesNo