Pure red-cell aplasia and antierythropoietin antibodies in patients treated with recombinant erythropoietin

Once-weekly epoetin alfa improves anemia and facilitates maintenance of ribavirin dosing in hepatitis C virus-infected patients receiving ribavirin plus interferon alfa

OBJECTIVE

The aim of this study was to determine the efficacy of epoetin alfa in alleviating anemia and minimizing ribavirin (RBV) dose reductions in patients with chronic hepatitis C virus (HCV) infection receiving combination RBV/interferon alfa (IFN) therapy.

METHODS

HCV-infected patients who had Hb levels of 12 g/dl or less during the first 24 wk of combination RBV/IFN therapy (n=64) were randomized to treatment with epoetin alfa (40,000 units) s.c. q.w. or to standard of care (SOC) for anemia management (RBV dose reduction or discontinuation, transfusions). Primary and secondary efficacy endpoints were changes in Hb level and RBV dosage, respectively, from baseline to week 16 of epoetin alfa therapy. Based on intent-to-treat analysis, the mean changes from baseline Hb levels at week 16 were +2.8 g/dl for epoetin alfa versus +0.4 g/dl for SOC (p<0.0001), and the mean changes in RBV dosage were -34 mg/day for epoetin alfa versus -146 mg/day (p=0.060) for SOC. The mean Hb level at week 16 in the epoetin alfa group (13.8 g/dl) was significantly (p<0.0001) higher than that of the SOC group (11.4 g/dl). At week 4 and subsequently, significantly more patients in the epoetin alfa group did not have RBV dosage reductions (p<0.011). At study end, 83% of epoetin alfa-treated patients maintained RBV dosages of at least 800 mg/day, compared with 54% of patients receiving SOC (p=0.022). Epoetin alfa was well tolerated.

CONCLUSIONS

In anemic HCV-infected patients treated with RBV/IFN, epoetin alfa increases Hb levels and maintains RBV dosing. Based on these results, epoetin alfa seems to be promising in the treatment of HCV treatment-related anemia. Further research is warranted to determine the potential impact on outcomes, including quality of life and sustained viral response rate.

Sugar coating extends half-lives and improves effectiveness of cytokine hormones

Recombinant human erythropoietin (rhEPO) is an effective and widely used therapeutic agent that is produced by bioengineering. Modification of the rhEPO protein by glycoengineering increased its already abundant N-glycosylation, which enhances its erythropoietic activity in vivo by decreasing its metabolic clearance. Elliott et al. recently reported increased in vivo activities of thrombopoietin (Mpl ligand) and leptin following carbohydrate addition to both, which suggests that such glycoengineering could be applied to a variety of hormones, cytokines and growth factors.

The use of erythropoietin

EPO is a hematopoietic growth factor produced in the kidney that stimulates erythropoiesis. It effectively treats hypoproliferative anemia associated with CRF, improving quality of life in these patients. Other uses that are poorly characterized in veterinary medicine include treatment of cancer patients on chemotherapy, hematologic disorders, and anemic FeLV-infected cats as well as preoperative conditioning for elective surgeries that may involve significant blood loss. Careful monitoring of therapy is necessary for optimal results. Several complications are associated with rHuEPO therapy. The production of anti-rHuEPO antibodies is the most significant and can be a life-threatening event. Alternatives to human EPO are being sought to provide beneficial effects while avoiding antibody formation.

Dissemination of information on potentially fatal adverse drug reactions for cancer drugs from 2000 to 2002: first results from the research on adverse drug events and reports project

PURPOSE

To describe the clinical findings, occurrence rates, causality evidence, and dissemination media for serious cancer drug-associated adverse drug reactions (ADRs) reported in the postmarketing setting.

METHODS

ADRs were termed serious if they resulted in death or severe organ failure. ADR information for oncology drugs from package insert (PI) revisions, so-called Dear Doctor letters, and journal articles was evaluated to identify serious ADRs reported from 2000 to 2002. Timing and content of information disseminated was assessed.

RESULTS

Twenty-five serious ADRs associated with 22 oncology drugs were identified after approval. Approximately half of these serious ADRs are associated with drugs approved before 1995. ADRs were described in articles in medical journals (17 ADRs), PI revisions (18 ADRs), and Dear Doctor letters (12 ADRs). PI revisions occurred less than 1 year after peer-reviewed publication for four ADRs. These revisions often differed for similar ADRs that occurred with drugs of the same class. Five of the seven ADRs lacking PI changes occurred with off-label use, for which PI change is not recommended by US Food and Drug Administration (FDA) policy. No cancer drug was withdrawn from the market during the observation period.

CONCLUSION

Our findings demonstrate that serious ADRs may be discovered as long as 36 years after a drug receives FDA approval. This suggests a need for continued vigilance and efficient strategies for dissemination of information about ADRs associated with cancer drugs.

Function of a conserved residue in the amino terminal alpha-helix of four helical bundle cytokines

The Glu residue in the helix A is conserved among many cytokines. Mutation in this residue converts some cytokines to an antagonist. Such an artificial cytokine with an antagonist activity may be useful in a clinical area. In this study we generated a mutant granulocyte colony-stimulating factor (G-CSF) termed G-CSF.E20K in which this residue is substituted to Lys. It is known that G-CSF binds to a homodimeric receptor, while other cytokines which can be converted to antagonists bind to heterodimeric receptors. We showed that G-CSF.E20K does not bind to the receptor at all, and that it fails to stimulate proliferation. Thus, the mutant did not act as an antagonist. We propose that the nature of the receptor, namely whether it is a homodimer or heterodimer, determines the antagonist activity of the mutant.

Safety of donating multiple products in a single apheresis collection: Are we expecting too much?

Modern blood separators rapidly process many liters of donor blood and efficiently collect vast quantities of blood components from donors, who may be stimulated with potent recombinant hematopoietic growth factors or cytokines. Accordingly, the potential risks of modern multiple product/unit apheresis donations and recombinant growth factors is analyzed in this report. As is true for all medical procedures, risks are associated with apheresis donations. Risks of a "standard" apheresis donation, in which one unit of PLTs or plasma is collected, are comparable to the risks of whole blood donation. Risks of multiple unit apheresis donations, in which either vast quantities of a single blood component or multiple units of various components are collected, are incompletely understood, particularly, when donors are stimulated with recombinant hematopoietic growth factors to increase component yields. To minimize donor risks and to increase knowledge of multiple component apheresis donations, both short-term problems (e.g., donor reactions accompanying apheresis procedures and pre- vs. post-procedure changes in results of donor laboratory studies) and long-term problems (e.g., medical diagnoses/problems and abnormalities of donor blood counts and laboratory test results) should be monitored, ideally, by a repeat donor registry. When recombinant hematopoietic growth factors are prescribed, donors should give informed consent, and blood center professionals must be aware of 1) the effects of these drugs given at pharmacologic, rather than physiologic, doses; 2) the differences between the molecular structure of recombinant vs. natural/endogenous growth factors; 3) the fact that recombinant growth factors have both narrow/focused and broad biological activities; and 4) the probability that results of studies in sick/immunosuppressed patients may not be applicable to healthy/immunocompetent donors.

Acquired pure red cell aplasia in a hemodialyzed patient

A 68-year-old male had end-stage renal disease secondary to hypertension. He was placed on chronic dialytic therapy and was given recombinant human erythropoietin (epoetin) for renal anemia. One month later, rapidly progressing anemia was noted. The anemia was unresponsive to maximal doses of epoetin and the patient soon became transfusion-dependent. Erythroid hypoplasia was demonstrated by bone marrow biopsy. A detailed search for the cause of the erythroblastopenia revealed nothing. A diagnosis of acquired pure red cell aplasia was made. The use of immunosuppressive agents improved the patient's symptoms and laboratory data. Antibodies for erythropoietin (EPO) were negative after the treatment. It is suggested that patients with EPO-resistant anemia with no obvious etiology should be examined for underlying hematologic disorders.

Hemodynamic changes in anemic premature infants: are we allowing the hematocrits to fall too low?

OBJECTIVE

Currently, many nurseries allow hematocrits to fall to <21% in apparently "stable" premature infants before considering a blood transfusion. We evaluated clinical changes and hemodynamic changes by echocardiogram in "stable" anemic premature infants before, during, and after transfusion.

METHODS

"Stable" premature infants (< or =32 weeks' gestation) who were to receive transfusions (2 aliquots of 10 mL/kg packed red blood cells, 12 hours apart) were eligible for prospective enrollment. Cardiac function by echocardiography and vital signs were measured 4 times: 1 to 3 hours before and 2 to 4 hours after the initial aliquot and 4 to 7 hours and 27 to 34 hours after the second aliquot. Infants were grouped prospectively according to pretransfusion hematocrit ranges for analysis: < or =21% (low), 22% to 26% (mid), and > or =27% (high).

RESULTS

Thirty-two infants were enrolled. No differences were observed between the groups in sex, birth weight, postconceptional age, or postnatal weight at enrollment. Before transfusion, low- and mid-range groups had higher left ventricular end systolic and diastolic diameters, in comparison with high range. Low range had increased stroke volume in comparison with the high-range group. These changes persisted after transfusion. Mean diastolic blood pressure rose and peak velocity in the aorta fell in the low-range group after transfusion. Pretransfusion hematocrit was correlated with but poorly predictive of echocardiographic measurements. Infants with inappropriate weight gain had increased ventricular end diastolic diameters, consistent with congestive heart failure.

CONCLUSIONS

Apparently "stable" anemic premature infants may be in a clinically unrecognized high cardiac output state, and some echocardiographic measurements do not improve within 48 hours after transfusion. The benefits of transfusion practices guided by measures of cardiac function should be evaluated.

Enhancing incretin action for the treatment of type 2 diabetes

OBJECTIVE

To examine the mechanisms of action, therapeutic potential, and challenges inherent in the use of incretin peptides and dipeptidyl peptidase-IV (DPP-IV) inhibitors for the treatment of type 2 diabetes.

RESEARCH DESIGN AND METHODS

The scientific literature describing the biological importance of incretin peptides and DPP-IV inhibitors in the control of glucose homeostasis has been reviewed, with an emphasis on mechanisms of action, experimental diabetes, human physiological experiments, and short-term clinical studies in normal and diabetic human subjects.

RESULTS

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) exert important effects on beta-cells to stimulate glucose-dependent insulin secretion. Both peptides also regulate beta-cell proliferation and cytoprotection. GLP-1, but not GIP, inhibits gastric emptying, glucagon secretion, and food intake. The glucose-lowering actions of GLP-1, but not GIP, are preserved in subjects with type 2 diabetes. However, native GLP-1 is rapidly degraded by DPP-IV after parenteral administration; hence, degradation-resistant, long-acting GLP-1 receptor (GLP-1R) agonists are preferable agents for the chronic treatment of human diabetes. Alternatively, inhibition of DPP-IV-mediated incretin degradation represents a complementary therapeutic approach, as orally available DPP-IV inhibitors have been shown to lower glucose in experimental diabetic models and human subjects with type 2 diabetes.

CONCLUSIONS

GLP-1R agonists and DPP-IV inhibitors have shown promising results in clinical trials for the treatment of type 2 diabetes. The need for daily injections of potentially immunogenic GLP-1-derived peptides and the potential for unanticipated side effects with chronic use of DPP-IV inhibitors will require ongoing scrutiny of the risk-benefit ratio for these new therapies as they are evaluated in the clinic.

Recovery of pure red-cell aplasia secondary to antierythropoietin antibodies after cessation of recombinant human erythropoietin

We describe a patient with end-stage renal failure (ESRF) who developed anti-erythropoietin (anti-EPO) antibodies and pure red-cell aplasia (PRCA) after using Eprex (Janssen-Cilag, Sydney). Anti-EPO antibodies were detected with an immunoprecipitation technique and were shown to inhibit erythropoiesis in vitro. Antibody levels waned upon ceasing Eprex. The patient required transfusions for 21 months then recovered after immunosuppression.

Defect in the lymphoid compartment might account for CD8+-mediated effects in the pathophysiology of pure red cell aplasia

Pure red cell aplasia (PRCA) is a rare hematological syndrome characterized by the lack of red cell progenitors in an otherwise normocellular bone marrow. Many agents and mechanisms have been implicated in the pathophysiology of PRCA, including immune-mediated dysfunctions. This report describes three patients with PRCA with unknown underlying cause and showed that for each, increases in CD8+ cells blunted the maturation of early erythroid (BFU-E). Each patient subsequently responded to immunosuppressive therapy. Peripheral blood mononuclear cells from age- and sex-matched healthy controls showed comparable distribution of CD3, CD4 and CD16, but significant increase in CD8 and decreased CD19. The distribution of lymphocyte subsets correlated with mitogen responses, but showed no difference in allogeneic responses when compared to controls. The adherent population in PRCA is important for mediating the hyper-immune state of patients, when IL-2 levels were used as readout. There was a trend for decreased BFU-E in patients, but marked reduction for late erythroid progenitors (CFU-E). CD8+ cells from PRCA blunted the maturation of BFU-E, despite increasing erythropoietin concentrations. These results strongly suggest that there are defects in the lymphoid compartment that feedback on the erythroid lineage of PRCA.

Anemia in acute renal failure: role for erythropoiesis-stimulating proteins?

The use of recombinant human erythropoietin (rHuEpo) has revolutionized anemia management of early and late stages of chronic kidney disease. Darbopoietin is also now available for the treatment of anemia of chronic kidney disease. In addition, rHuEpo has been used for the treatment of anemia observed in critical illness. Unfortunately, the existing clinical studies of anemia in critically ill patients do not distinguish between those with and without acute renal failure (ARF). This review summarizes the existing experimental and clinical studies supporting the use of rHuEpo in ARF due to ischemic/nephrotoxic injury and conclusions are drawn on the rationale for further research into the use of this drug in ARF.

Myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are characterized by hemopoietic insufficiency associated with cytopenias leading to serious morbidity plus the additional risk of leukemic transformation. Therapeutic dilemmas exist in MDS because of the disease's multifactorial pathogenetic features, heterogeneous stages, and the patients' generally elderly ages. Underlying the cytopenias and evolutionary potential in MDS are innate stem cell lesions, cellular/cytokine-mediated stromal defects, and immunologic derangements. This article reviews the developing understanding of biologic and molecular lesions in MDS and recently available biospecific drugs that are potentially capable of abrogating these abnormalities. Dr. Peter Greenberg's discussion centers on decision-making approaches for these therapeutic options, considering the patient's clinical factors and risk-based prognostic category. One mechanism underlying the marrow failure present in a portion of MDS patients is immunologic attack on the hemopoietic stem cells. Considerable overlap exists between aplastic anemia, paroxysmal nocturnal hemoglobinuria, and subsets of MDS. Common or intersecting pathophysiologic mechanisms appear to underlie hemopoietic cell destruction and genetic instability, which are characteristic of these diseases. Treatment results and new therapeutic strategies using immune modulation, as well as the role of the immune system in possible mechanisms responsible for genetic instability in MDS, will be the subject of discussion by Dr. Neal Young. A common morphological change found within MDS marrow cells, most sensitively demonstrated by electron microscopy, is the presence of ringed sideroblasts. Such assessment shows that this abnormal mitochondrial iron accumulation is not confined to the refractory anemia with ring sideroblast (RARS) subtype of MDS and may also contribute to numerous underlying MDS pathophysiological processes. Generation of abnormal sideroblast formation appears to be due to malfunction of the mitochondrial respiratory chain, attributable to mutations of mitochondrial DNA, to which aged individuals are most vulnerable. Such dysfunction leads to accumulation of toxic ferric iron in the mitochondrial matrix. Understanding the broad biologic consequences of these derangements is the focus of the discussion by Dr. Norbert Gattermann.

Pharmacokinetics/pharmacodynamics of recombinant human erythropoietins in doping control

The purpose of this paper is: (i) to compare recombinant human erythropoietin (rHuEPO) pharmacokinetics in athletes and healthy individuals; and (ii) to report pharmacokinetic/pharmacodynamic (PK/PD) studies performed in athletes. Effect parameters in PK/PD studies included: (i) red blood cell variables (haematocrit, reticulocyte count); and (ii) markers of iron metabolism (serum soluble transferrin receptors [sTfR], ferritin [fr] and sTfR : fr ratio). To understand the choice of these markers, we first performed a brief review of the pharmacological effects of rHuEPO. Few studies have been conducted in healthy individuals and there are minimal references concerning pharmacokinetics in athletes. A 'flip-flop' phenomenon was noted after subcutaneous administration. The pharmacokinetics appeared linear from 50-1000 U/kg, but this linearity was not observed at the lowest dose of 10 U/kg. A negative-feedback loop of endogenous erythropoietin production occurred at the end of treatment. The half-life of the terminal part of the curves seemed to be slightly higher in athletes (36-42 vs 32 hours) than in untrained individuals and total clearance tended to be greater (17.5 vs 6.5 mL/h/kg). In conclusion, more investigations are needed to better understand the relationship between rHuEPO administration and changes in haematological and iron-metabolism parameters in athletes, particularly after chronic low-dose administration of rHuEPO.

Drugs for increasing oxygen and their potential use in doping: a review

Blood oxygenation is a fundamental factor in optimising muscular activity. Enhancement of oxygen delivery to tissues is associated with a substantial improvement in athletic performance, particularly in endurance sports. Progress in medical research has led to the identification of new chemicals for the treatment of severe anaemia. Effective and promising molecules have been created and sometimes used for doping purposes. The aim of this review is to present methods, and drugs, known to be (or that might be) used by athletes to increase oxygen transport in an attempt to improve endurance capacity. These methods and drugs include: (i) blood transfusion; (ii) endogenous stimulation of red blood cell production at altitude, or using hypoxic rooms, erythropoietins (EPOs), EPO gene therapy or EPO mimetics; (iii) allosteric effectors of haemoglobin; and (iv) blood substitutes such as modified haemoglobin solutions and perfluorochemicals. Often, new chemicals are used before safety tests have been completed and athletes are taking great health risks. Such new chemicals have also created the need for new instrumental strategies in doping control laboratories, but not all of these chemicals are detectable. Further progress in analytical research is necessary.

The management of anemia in pediatric peritoneal dialysis patients. Guidelines by an ad hoc European committee

Anemia is common in chronic renal failure. Guidelines for the diagnosis and treatment of anemia in adult patients are available. With respect to the diagnosis and treatment in children on peritoneal dialysis, the European Pediatric Peritoneal Dialysis Working Group (EPPWG) has produced guidelines. After a thorough diagnostic work-up, treatment should aim for a target hemoglobin concentration of at least 11 g/l. This can be accomplished by the administration of erythropoietin and iron preparations. Although there is sufficient evidence to advocate the intraperitoneal administration of erythropoietin, most pediatric nephrologists still apply erythropoietin by the subcutaneous route. Iron should preferably be prescribed as an oral preparation. Sufficient attention has to be paid to the nutritional intake in these children. There is no place for carnitine supplementation in the treatment of anemia in pediatric peritoneal dialysis patients.

The Implications of Anemia in Multiple Myeloma

Multiple myeloma (MM) is commonly associated with anemia. Several causes have been implicated, but anemia of chronic disease with inadequate erythropoietin (EPO) production related to the inflammatory cytokines appears to be of utmost importance. Interleukin-1 and tumor necrosis factor are capable of suppressing erythropoiesis. Anemia has broad implications. First, the low hemoglobin and hematocrit are associated with poor quality of life and performance and affect daily activity. Second, anemia has an impact on the cardiovascular system. Considering that most MM patients are elderly, this may be even more important. Anemia has been shown to induce or aggravate hypoxia and ischemic complications. Third, anemia has been shown to be a poor prognostic factor in MM. Traditionally, patients with symptomatic anemia were treated with red blood cell transfusions as needed. The introduction of epoetin alfa and epoetin beta into clinical practice opened new avenues to these patients. The administration of epoetins to patients with MM and anemia have been shown to be very useful. Several studies in more than 1000 patients have demonstrated a high response rate (range, 25%-85%; mean, 60%). This response is characterized by a significant increase of hemoglobin, hematocrit, and the number of red blood cells together with a reduction in the blood transfusion requirements. This is also associated with an improved quality of life. Although there is no complete agreement about the role of pretreatment serum EPO levels, many investigators believe that relatively low levels may help in predicting response, thereby limiting the number of potential candidates to receive this expensive therapy. The epoetins are safe and well tolerated with minimal toxicity; however, some concern has been recently raised regarding several dozen patients who developed pure red cell aplasia while on epoetin therapy. However, this adverse effect appears to be extremely rare. Recent data suggest that EPO has additional biologic effects, such as longer-than-expected survival in patients with MM. This observation is further supported by animal studies, demonstrating an antimyeloma effect of EPO in mice models. This effect has been shown to be immune mediated. If these exciting data are confirmed in future clinical trials, this may have significant implications on the treatment of MM.

Once-weekly epoetin beta is highly effective in treating anaemic patients with lymphoproliferative malignancy and defective endogenous erythropoietin production

Epoetin beta, three-times weekly (t.i.w.), is effective in reversing anaemia in lymphoproliferative disorders. The current study investigated whether an epoetin beta dose of 30,000 IU given subcutaneously once weekly (q.w.) was at least as effective as 10,000 t.i.w. administration in anaemic patients with lymphoproliferative malignancy and defective endogenous erythropoietin (Epo) production. Overall, 241 anaemic patients with multiple myeloma, low-grade non-Hodgkin's lymphoma or chronic lymphocytic leukaemia, all with serum Epo values </= 100 mU/ml, were randomized to receive the q.w. (n = 119) or t.i.w. (n = 122) regimen for 16 weeks. The primary efficacy criterion, i.e. the time-adjusted area under the haemoglobin-time curve from weeks 5-16, was comparable between the q.w. and t.i.w. groups [difference = - 0.20 g/dl (90% confidence interval - 0.52-0.11)]. Moreover, response rates were high and similar in both arms (72%vs 75%, q.w. and t.i.w. groups respectively). Baseline serum Epo was predictive of response: the lower serum Epo, the higher the likelihood of response (P = 0.002). Thus, epoetin beta administered q.w. is an effective and convenient treatment for anaemia in patients with lymphoproliferative disorders. Tailoring this treatment modality to subjects with defective endogenous Epo production represents a rational use of epoetin from both a medical and a community perspective.

Anemia in children after transplantation: etiology and the effect of immunosuppressive therapy on erythropoiesis

Anemia in children after renal transplantation is more common than previously appreciated. Multiple factors appear to play roles in the development of post-transplant anemia, the most common of which is absolute and/or functional iron deficiency anemia. Most experts recommend that iron limited anemias in transplant patients should be diagnosed using the same criteria as for chronic renal failure patients. Serum erythropoietin (EPO) levels are expected to normalize after a successful renal transplantation with a normal kidney function, yet both EPO deficiency and resistance have been reported. While no large controlled trials comparing the effect of different immunosuppressive agents on erythropoiesis after transplantation have been performed, generalized bone marrow suppression attributable to azathioprine (AZA), mycophenolate mofetil (MMF), tacrolimus, antithymocyte preparations has been reported. Pure red cell aplasia (PRCA) occurs rarely after transplantation and is characterized by the selective suppression of erythroid cells in the bone marrow. PRCA has been reported with the use of AZA, MMF, tacrolimus, angiotensin converting enzyme inhibitors (ACEI), but not with cyclosporine (CSA) use. Post-transplant hemolytic uremic syndrome has been reported with orthoclone anti T-cell antibody (OKT3), CSA and tacrolimus therapy. Viral infections including cytomegalovirus, Epstein-Barr virus and human parvovirus B19 have been reported to cause generalized marrow suppression. Management of severe anemia associated with immunosuppressive drugs generally requires lowering the dose, drug substitution or, when possible, discontinuation of the drug. Because this topic has been incompletely studied, our recommendation as to the best immunosuppressive protocol after renal transplantation remains largely dependent on the clinical response of the individual patient.

Stem cell factor protects erythroid precursor cells from chemotherapeutic agents via up-regulation of BCL-2 family proteins

Suppression of red blood cell production is a common complication of chemotherapy, causing anemia in a significant number of cancer patients. We have evaluated the sensitivity of human hematopoietic progenitors and erythroid precursor cells to chemotherapeutic drugs and found that probasophilic erythroblasts represent the stage of erythroid differentiation more vulnerable to the cytotoxic effects of myelosuppressive agents. Stem cell factor (SCF) supports proliferation and survival of early hematopoietic cells by binding to the c-kit receptor. In unilineage erythropoietic culture of CD34+ progenitors, short-term pretreatment of immature erythroid precursors with SCF results in protection from apoptosis induced by chemotherapeutic agents and restores normal proliferation and differentiation after removal of the cytotoxic stimulus. The levels of drug-induced caspase processing are significantly reduced in erythroblasts treated with SCF, indicating that activation of the c-kit receptor generates antiapoptotic signals acting before amplification of the caspase cascade. Accordingly, we found that SCF up-regulates Bcl-2 and Bcl-X L in erythroid precursors and that exogenous expression of these proteins protects erythroblasts from caspase activation and death induced by chemotherapeutic agents. These results suggest a possible mechanism for SCF-mediated protection of erythroid precursor cells from apoptosis and may contribute to devise new strategies for prevention and treatment of chemotherapy-induced anemia.

Recombinant erythropoietin in clinical practice

The introduction of recombinant human erythropoietin (RHuEPO) has revolutionised the treatment of patients with anaemia of chronic renal disease. Clinical studies have demonstrated that RHuEPO is also useful in various non-uraemic conditions including haematological and oncological disorders, prematurity, HIV infection, and perioperative therapies. Besides highlighting both the historical and functional aspects of RHuEPO, this review discusses the applications of RHuEPO in clinical practice and the potential problems of RHuEPO treatment.

Strategies for detection, measurement and characterization of unwanted antibodies induced by therapeutic biologicals

An important aspect of evaluating the safety of therapeutic biologicals is the assessment of the unwanted immunogenicity of such biologicals in recipients. Properly planned immunogenicity studies with appropriately devised strategies are critical if valid conclusions concerning the unwanted immunogenicity are to be derived. Such studies need to be conducted using carefully selected and validated procedures. Several techniques are available for detection and measurement of immunogenicity including immunoassays, radioimmunoprecipitation assays (RIPAs), surface plasmon resonance (SPR) and bioassays. A combination of methods for characterization of the induced antibodies is usually necessary for a detailed understanding of the type(s) of antibodies generated against a therapeutic product. This review considers the benefits and limitations of the various techniques available for antibody detection and outlines a strategy for the assessment of unwanted immunogenicity of therapeutic products.

Neutralization of the biological activity of cytokines and other protein effectors by antibody: theoretical formulation of antibody titration curves in relation to antibody affinity

Patients treated with interferons, other cytokines, or various biologically active proteins may form neutralizing antibodies, which can adversely affect clinical outcome. It is therefore important to understand how antibodies neutralize such soluble protein antigens and how best to quantitate such antibodies. By applying the mass action law to antigen-antibody reactions, we previously developed a mathematical model applicable in two situations: first, for antibodies having low affinity for the antigen concerned (the Constant Proportion (CP) case), and, second, for antibodies having high affinity (the Fixed Amount (FA) case). The results allowed calculation of neutralization titers which were independent of the particular assay method used. Neutralization by antibodies of intermediate affinity, however, requires different mathematical treatment because the mode of neutralization does not fit the two cases mentioned above. In this paper, theoretical neutralization curves were derived, based on the same mathematical model, for antibodies of intermediate affinity. We show that the slope of the neutralization curve relating residual active antigen to the concentration of antibodies is determined by the antibody association constant and the molar concentration of the effector antigen. It is therefore possible to infer the magnitude of the association constant from the observed neutralization curve. We show that values obtained for the neutralization titer of antibodies of intermediate affinity by the use of the formula previously described for the Fixed Amount and Constant Proportion cases may deviate from the theoretically sound values; the magnitude of the deviation can be estimated by applying the formulas described herein. These relationships should apply generally to antibody neutralization reactions with all biologically active soluble protein effector molecules that have a single and nonrepetitive epitope.

Development of an animal–human antibody complex for use as a control in ELISA

In order to provide the equivalent of a human anti-human protein antibody as positive control in ELISAs, a goat-human antibody complex was created using chemical cross-linking. The resulting hybrid complex had a larger molecular size on HPLC and SDS-PAGE. In ELISA, the goat-human complex bound to human antigen and was detectable by a secondary anti-human conjugate. The method to make the hybrid complex is simple, cost-effective and can be used to make human-like antibodies to many human proteins.

[Recombinant Human Erythropoietin (r-HuEPO) therapy in a newborn with hereditary spherocytosis]

The newborn with hereditary spherocytosis can develop severe anemia, requiring red blood cell transfusions. Therapy with r-HuEPO has been proposed to avoid transfusions.

CASE REPORT

Hereditary spherocytosis was diagnosed in a newborn who had severe and early jaundice. He was treated with r-HuEPO, and did not require red blood cells transfusion.

CONCLUSION

Recombinant erythropoïetin might be an interesting alternative to red blood cells transfusions during the neonatal period in newborns with hereditary spherocytosis.

What is the rationale for the use of granulocyte and granulocyte-macrophage colony-stimulating factors in the neonatal intensive care unit?

Neonatal sepsis remains an unsolved major contributor to morbidity and mortality. In the 1980s the promise of augmenting immune function using pooled intravenous gammaglobulin to supplement the exceedingly low levels of immunoglobulin G in premature infants failed to demonstrate a clear advantage. Similarly, cytokine augmentation of cellular function in the 1990s largely appeared to be suffering the same fate. However, both results may arise from a problem in experimental design where the combination of both treatments may be necessary along with specific antibody. For example, in vitro, independently of an array of other humoral and cellular immature immune system issues, opsonization of bacteria is improved in the presence of antibody. The question is whether the same result can be achieved in vivo. No experiments have been reported that directly test this hypothesis.

CONCLUSION

More investigation is needed in this challenging area of neonatal research.

Cyclosporine treatment for patients with CRF who developed pure red blood cell aplasia following EPO therapy

Human recombinant erythropoietin is the main treatment for anemia in renal patients. Recently, there have been case reports of pure red blood cell aplasia (PRCA) developing in renal patients administered erythropoietin, probably because of neutralizing antibodies detected in all these patients. All reports were from the West, and most patients were treated with erythropoietin-alpha. Cyclosporine is an immunosuppressive agent used to treat a spectrum of autoimmune conditions. We report a series of Chinese renal patients who developed PRCA after treatment with erythropoietin-alpha, suggesting that this is a problem worldwide. They were treated successfully with cyclosporine and became transfusion independent.

Apaf-1, Bcl-xL, cytochrome c, and caspase-9 form the critical elements for cerebral vascular protection by erythropoietin

Erythropoietin (EPO) plays a prominent role in the regulation of the hematopoietic system, but the potential function of this trophic factor as a cytoprotectant in the cerebral vascular system is not known. The authors examined the ability of EPO to modulate a series of death-related cellular pathways during free radical-induced injury in cerebral microvascular endothelial cells (ECs). Endothelial cell injury was evaluated by trypan blue, DNA fragmentation, membrane phosphatidylserine exposure, apoptotic protease-activating factor-1 (Apaf-1), and Bcl-XL expression, mitochondrial membrane potential, cytochrome c release, and cysteine protease activity. They show that constitutive EPO is present in ECs but is insufficient to prevent cellular injury. Signaling through the EPO receptor, however, remains biologically responsive to exogenous EPO administration to offer significant protection against nitric oxide-induced injury. Exogenous EPO maintains both genomic DNA integrity and cellular membrane asymmetry through parallel pathways that prevent the induction of Apaf-1 and preserve mitochondrial membrane potential in conjunction with enhanced Bcl-XL expression. Consistent with the modulation of Apaf-1 and the release of cytochrome c, EPO also inhibits the activation of caspase-9 and caspase-3-like activities. Identification of novel cytoprotective pathways used by EPO may serve as therapeutic targets for cerebral vascular disease.

Erythropoietin prevents early and late neuronal demise through modulation of Akt1 and induction of caspase 1, 3, and 8

Erythropoietin (EPO) modulates primarily the proliferation of immature erythroid precursors, but little is known of the potential protective mechanisms of EPO in the central nervous system. We therefore examined the ability of EPO to modulate a series of death-related cellular pathways during anoxia and free radical induced neuronal degeneration. Neuronal injury was evaluated by trypan blue, DNA fragmentation, membrane phosphatidylserine exposure, protein kinase B phosphorylation, cysteine protease activity, mitochondrial membrane potential, and mitogen-activated protein (MAP) kinase phosphorylation. We demonstrate that constitutive neuronal EPO is insufficient to prevent cellular injury, but that signaling through the EPO receptor remains biologically responsive to exogenous EPO administration. Exogenous EPO is both necessary and sufficient to prevent acute genomic DNA destruction and subsequent phagocytosis through membrane PS exposure, because neuronal protection by EPO is completely abolished by co-treatment with an anti-EPO neutralizing antibody. Through pathways that involve the initial activation of protein kinase B, EPO maintains mitochondrial membrane potential. Subsequently, EPO inhibits caspase 8-, caspase 1-, and caspase 3-like activities linked to cytochrome c release through mechanisms that are independent from the MAP kinase systems of p38 and JNK. Elucidating some of the novel neuroprotective pathways employed by EPO may further the development of new therapeutic strategies for neurodegenerative disorders.

Iron metabolism in end stage renal failure: rationale for re-evaluation of parenteral iron therapy

PURPOSE OF REVIEW

In this article we will examine the basis for using chronic high dose parenteral iron therapy in dialysis patients.

RECENT FINDINGS

There are increasing data that dialysis patients fare better in many respects if they have higher hematocrit values although the real optimal hematocrit has not been defined. There is an increasing tendency to use parenteral iron to achieve this goal.

SUMMARY

Although parenteral iron achieves seemingly favourable short results, there are no data for its safety in the long term. On the contrary, there are reasons to suggest possible iron overload with chronic use.

Erythropoietin fosters both intrinsic and extrinsic neuronal protection through modulation of microglia, Akt1, Bad, and caspase-mediated pathways

1. Erythropoietin (EPO) plays a significant role in the hematopoietic system, but the function of EPO as a neuroprotectant and anti-inflammatory mediator requires further definition. We therefore examined the cellular mechanisms that mediate protection by EPO during free radical injury in primary neurons and cerebral microglia. 2. Neuronal injury was evaluated by trypan blue, DNA fragmentation, phosphatidylserine (PS) exposure, Akt1 phosphorylation, Bad phosphorylation, mitochondrial membrane potential, and cysteine protease activity. Microglial activation was assessed through proliferating cell nuclear antigen and PS receptor expression. 3. EPO provides intrinsic neuronal protection that is both necessary and sufficient to prevent acute genomic DNA destruction and subsequent membrane PS exposure, since protection by EPO is completely abolished by cotreatment with an anti-EPO neutralizing antibody. 4. Extrinsic protection by EPO is offered through the inhibition of cerebral microglial activation and the suppression of microglial PS receptor expression for the prevention of neuronal phagocytosis. In regards to microglial chemotaxis, EPO modulates neuronal poptotic membrane PS exposure necessary for microglial activation primarily through the regulation of caspase 1. 5. EPO increases Akt1 activity, phosphorylates Bad, and maintains neuronal nuclear DNA integrity through the downstream modulation of mitochrondrial membrane potential, cytochrome c release, and caspase 1, 3, and 8-like activities. 6. Elucidating the intrinsic and extrinsic protective pathways of EPO that mediate both neuronal integrity and inflammatory microglial activation may enhance the development of future therapies directed against acute neuronal injury.

Neutralizing antibodies in gene-defective hosts

In a host with a normal immune system and a complete gene defect, the nondefective gene product will be immunogenic. Consequently, neutralizing antibodies against the respective protein can arise either 'spontaneously' or after immunization, as shown in patients and in animal models, such as knockout mice. Accordingly, patients with X-linked or homozygous autosomal gene defects are at risk of developing neutralizing antibodies, in particular after protein substitution or gene therapy. This Review compares and exemplifies the various genetic and immunological contexts that lead to 'neutralizing and generated by gene defect' or 'nagged' antibodies, and outlines implications and solutions for therapeutic strategies.

Epoetins: differences and their relevance to immunogenicity

Recombinant human erythropoietin (epoetin) is a highly active molecule and as such is used at very low therapeutic concentrations that require stabilisation. Commercially available epoetins differ in the stabilisers used in their formulations, which result in variations between epoetin preparations in storage and handling requirements. The stability and solubility of the epoetins are also affected by differences in the carbohydrate moieties that exist between them. However, it is the difference in stabilising agents that is thought to be the major cause of the upsurge in pure red cell aplasia (PRCA) cases observed predominantly with one epoetin alfa formulation, Eprex (Johnson & Johnson). In 1998 the European formulation of Eprex was changed with the replacement of human serum albumin (HSA), by polysorbate 80 and glycine. This formulation change coincided with an increased incidence of PRCA. In contrast, the incidence of PRCA has remained low with other HSA-containing epoetin alfa products and with epoetin beta. Therefore, it appears that the change in Eprex formulation has resulted in reduced protein stability and increased immunogenicity.