Doping control of biosimilar epoetin kappa and other recombinant erythropoietins after intravenous application

Data from a microdosed recombinant human erythropoietin administration study applying the new biotinylated clone AE7A5 antibody and a further optimized sarcosyl polyacrylamide gel electrophoresis protocol

Erythropoietin (EPO) is a hormone, which stimulates the production of red blood cells. Due to its performance-enhancing effect, it is prohibited by the World Anti-Doping Agency (WADA). In order to reduce the detection window of EPO doping, athletes have been applying low doses of recombinant EPO (e.g., <10 IU/kg body weight, daily or every second day) instead of larger doses twice or more per week (e.g., 30 IU/kg). Microdoses of Retacrit (epoetin zeta), an EPO biosimilar, were administered intravenously and subcutaneously to human males and females. Urine and serum samples were collected and analysed applying the new biotinylated clone AE7A5 EPO antibody and a further optimized sarcosyl polyacrylamide gel electrophoresis (SAR-PAGE) protocol. With the improved protocol, microdosed Retacrit (7.5 IU/kg body weight [BW]) was detectable for at least 52 h after intravenous administration. Detection windows were approximately the same for serum and urine and doubled after subcutaneous administration (~104 h). Previous studies applying different electrophoretic techniques and the not further optimized SAR-PAGE protocol revealed considerably shorter detection windows for recombinant human erythropoietin (rhEPO) microdoses. Because the new biotinylated antibody performed significantly more sensitive than the nonbiotinylated version, the new protocol will improve the sensitivity and hence detectability of recombinant EPO in doping control.

Discovery of c.577del in EPO: Investigations into endogenous EPO double-band detected in blood with SAR-PAGE

Recently, some athletes were repetitively found to have rEPO positive results, including a characterized double-band pattern in blood samples, in routine doping analysis. In contrast to previous findings from excretion studies, this double-band pattern showed the same relative intensity even when the samples were collected weeks (/months) apart. We therefore suspected that these "positive" doping control samples were related with a novel pathway of endogenous EPO production. Thus, follow-up investigations were warranted to characterize the origin of such analytical test results and to avoid the issuing of adverse analytical findings in the absence of rEPO by identifying the root cause of these "constantly positives." In this study, we designed and conducted a series of causal studies, including population screening of EPO profiles, exploration of EPO de-N-glycosylation, single nucleotide polymorphism (SNP) browsing in EPO, sequencing of EPO exons, genealogical analysis of the c.577del EPO variant, and finally expression and investigation of mutant EPO. In summary, we found that these "constantly positives" were related to endogenous EPO production associated with the c.577del EPO variant. The frequency of this variant was 0.39% in our Chinese population pool. The mutant EPO encoded by this variant is 27 amino acids longer than the wild-type. The molecular weight of this mutant EPO is approximately the same as that of rEPO, exhibiting a similar electrophoretic behavior. To prevent charges against carriers of the c.577del variant, a revised rEPO testing strategy has been implemented in the new version of TD EPO.

Sensitivity and specificity of detection methods for erythropoietin doping in cyclists

Recombinant human erythropoietin (rHuEPO) is used as doping a substance. Anti‐doping efforts include urine and blood testing and monitoring the athlete biological passport (ABP). As data on the performance of these methods are incomplete, this study aimed to evaluate the performance of two common urine assays and the ABP. In a randomized, double‐blinded, placebo‐controlled trial, 48 trained cyclists received a mean dose of 6000 IU rHuEPO (epoetin β) or placebo by weekly injection for eight weeks. Seven timed urine and blood samples were collected per subject. Urine samples were analyzed by sarcosyl‐PAGE and isoelectric focusing methods in the accredited DoCoLab in Ghent. A selection of samples, including any with false presumptive findings, underwent a second sarcosyl‐PAGE confirmation analysis. Hematological parameters were used to construct a module similar to the ABP and analyzed by two evaluators from an Athlete Passport Management Unit. Sensitivity of the sarcosyl‐PAGE and isoelectric focusing assays for the detection of erythropoietin abuse were 63.8% and 58.6%, respectively, with a false presumptive finding rate of 4.3% and 6%. None of the false presumptive findings tested positive in the confirmation analysis. Sensitivity was highest between 2 and 6 days after dosing, and dropped rapidly outside this window. Sensitivity of the ABP was 91.3%. Specificity of the urine assays was high; however, the detection window of rHuEPO was narrow, leading to questionable sensitivity. The ABP, integrating longitudinal data, is more sensitive, but there are still subjects that evade detection. Combining these methods might improve performance, but will not resolve all observed shortcomings.

The Diversity of Biosimilar Design and Development: Implications for Policies and Stakeholders

Biosimilars are required to be similar or highly similar in structure to their biologic reference product but are neither expected nor required to contain identical active substances. For example, glycosylated biosimilars approved to date demonstrate quantitative and qualitative structural differences from their reference product and exemplify the latitude of variations permitted for biosimilars. Although differences between a candidate biosimilar and its reference product will be evaluated for differential clinical effects during biosimilarity assessment, it is unlikely that potential differences between any two indirectly related biosimilars will be formally evaluated. Furthermore, biosimilar pathways permit variations in pharmaceutical attributes, clinical development approaches, and regulatory outcomes, resulting in further diversity of attributes among approved biosimilars. Because biosimilars may vary across the ranges of structural and functional acceptance criteria, they should not be treated like multisource, generic drugs.

The ESA scenario gets complex: from biosimilar epoetins to activin traps

Recombinant human erythropoietin (rhEpo, epoetin) has proved beneficial in preventing transfusion-dependent anaemia in patients with chronic kidney disease. Apart from copied epoetins distributed in less regulated markets, 'biosimilar' epoetins have gained currency in many regions, where they compete with the originals and with rhEpo analogues with prolonged survival in circulation ('biobetter'). Recombinant erythropoiesis stimulating agents are potent and well tolerated. However, their production is costly, and they must be administered by the parenteral route. Hence, other anti-anaemia treatments are being evaluated. Clinical trials are being performed with stabilizers of the hypoxia-inducible transcription factors (HIFs), which increase endogenous Epo production. HIF stabilizers are chemical drugs and they are active on oral administration. However, there is fear that they may promote tumour growth. Epo mimetic peptides have also raised expectations. Yet the prototype peginesatide was recalled after just 1 year of its widespread use in the USA because of serious side-effects including cases of death. Most recently, clinical trials have been initiated with sotatercept, a recombinant soluble activin receptor type 2A IgG-Fc fusion protein. Sotatercept binds distinct members of the transforming growth factor-β family, thereby preventing the inhibitory action of these factors in erythropoiesis. Taken together, rhEpo and its long-acting recombinant analogues will likely remain mainstay of anti-anaemia therapies in the near future.

Efficacy of once or twice weekly administration of epoetin κ in patients receiving hemodialysis: A retrospective study

Several clinically approved recombinant erythropoietin (rEPO) preparations, such as epoetin-β, epoetin-δ and the epoetin-α derivative, darbepoetin-α, have been commercially produced. Since the expiration of patent protection, a number of novel rEPO biosimilars have been approved on the world market. In 2010, epoetin-κ, which is biosimilar to epoetin-α, was clinically approved. Epoetin-κ is a biopharmaceutical product that is based on serum-free media following master cell bank preparation. The present study analyzes the results obtained during a six-month observation period, in which the administration of epoetin-β was switched to that of epoetin-κ. In a cohort of patients receiving chronic dialysis, who were clinically in a state of relative calm and were in control of their renal anemia, it was possible to sustain good control of the anemia by reducing the frequency of the epoetin-β administration from the conventional and empirically determined three times a week to twice a week, and further to once a week. Furthermore, the good control was maintained upon changing from the administration of epoetin-β to that of epoetin-κ. Moreover, three months subsequent to this switch, the degree of instability observed among the patients had decreased. Despite the fact that the situation following the changeover requires further investigation, it may be concluded that the results obtained in this study are indicative of the clinical equivalence and efficacy of epoetin-κ.

Intolerability of cobalt salt as erythropoietic agent

Unfair athletes seek ways to stimulate erythropoiesis, because the mass of haemoglobin is a critical factor in aerobic sports. Here, the potential misuse of cobalt deserves special attention. Cobalt ions (Co(2+) ) stabilize the hypoxia-inducible transcription factors (HIFs) that increase the expression of the erythropoietin (Epo) gene. Co(2+) is orally active, easy to obtain, and inexpensive. However, its intake can bear risks to health. To elaborate this issue, a review of the pertinent literature was retrieved by a search with the keywords 'anaemia', 'cobalt', 'cobalt chloride', 'erythropoiesis', 'erythropoietin', 'Epo', 'side-effects' and 'treatment', amongst others. In earlier years, cobalt chloride was administered at daily doses of 25 to 300 mg for use as an anti-anaemic agent. Co(2+) therapy proved effective in stimulating erythropoiesis in both non-renal and renal anaemia, yet there were also serious medical adverse effects. The intake of inorganic cobalt can cause severe organ damage, concerning primarily the gastrointestinal tract, the thyroid, the heart and the sensory systems. These insights should keep athletes off taking Co(2+) to stimulate erythropoiesis.

Gel electrophoretic methods for the analysis of biosimilar pharmaceuticals using the example of recombinant erythropoietin

Due to their versatility and cost-effectiveness, gel electrophoretic methods provide an important set of tools for the analysis of therapeutic proteins. As an increasing number of biosimilar pharmaceuticals are entering the market, techniques are required that allow reliable demonstration of comparability of these products with the reference products. Isoelectric focusing, SDS-PAGE, native PAGE and 2D electrophoresis (2D-PAGE) have been frequently applied for this purpose. Supplementary techniques are fluorophore-assisted carbohydrate electrophoresis and sarcosyl-PAGE. Of additional importance is the comparison of recombinant with endogenously synthesized glycoproteins. Reagent array analysis combined with SDS-PAGE and western blotting proved especially useful for this purpose. As an example for the application of these methods, the analysis of recombinant originator erythropoietins and some of their biosimilar counterparts is described.