Biological evaluation of recombinant human erythropoietin in pharmaceutical products

A Reference Standard for Analytical Testing of Erythropoietin

Purpose

Erythropoietin (EPO) is a 165 amino acid protein that promotes the proliferation of erythrocytic progenitors. A decrease in endogenous EPO production causes anemia that can be treated with recombinant Human EPO (rHuEPO).

Objective

To ensure the safety and efficacy of the rHuEPO, manufacturers must use analytical methods to demonstrate similarity across batches and between different products. To do this they need reference standards to validate their equipment and methods.

Method

We used peptide mapping, size-exclusion chromatography, glycoprofiling, and isoelectric focusing to analyze a rHuEPO reference standard.

Results

Characterization demonstrates that our rHuEPO reference standard meets the criteria for quality.

Conclusion

The rHuEPO reference standard is fit for purpose as a tool for validating system suitability and methods.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03213-1.

Sustained-release of erythropoietin using a novel injectable thermosensitive hydrogel: in vitro studies, biological activity, and efficacy in rats

In the current study erythropoietin (EPO) loaded trimethyl chitosan/tripolyphosphate nanoparticles-embedded in a thermosensitive hydrogel was prepared. The influence of the main experimental factors on the properties of EPO-loaded nanoparticles were evaluated using a two-factors central composite design and the optimized formulation was then freeze dried. Sodium dodecyl sulfate-page and circular dichroismspectroscopy were used to confirm the structural stability of EPO following encapsulation and freeze drying. Rheological properties, and the release rate of EPO from the hydrogel were examined. Mean particle size, zeta potential, and entrapment efficiency of the optimized EPO-loaded nanoparticles were confirmed 151.5 ± 16 nm, 11.5 ± 1.8 mV, and 78.5 ± 5.9%, respectively. The hydrogel containing nanoparticles existed as a solution at room temperature converted to a semisolid upon increasing the temperature to 35 ± 1.2 °C and demonstrated controlled release of EPO for more than 10 days. The stability of EPO in the hydrogel system was further investigated using in vivo biological activity assay and the result revealed relative potency of 0.85 as calibrated with standard EPO. Finally, a single injection of the EPO-loaded nanoparticles-embedded in the hydrogel administered to Sprague-Dawley rats resulted in elevated reticulocytes for about 20 days compared to control group received blank hydrogel.

Synthesis in Escherichia coli and Characterization of Human Recombinant Erythropoietin with Additional Heparin-Binding Domain

Recombinant human erythropoietin (EPO) with additional N-terminal heparin-binding protein domain (HBD) from bone morphogenetic protein 2 was synthesized in Escherichia coli cells. A procedure for HBD-EPO purification and refolding was developed for obtaining highly-purified HBD-EPO. The structure of recombinant HBD-EPO was close to that of the native EPO protein. HBD-EPO contained two disulfide bonds, as shown by MALDI-TOF mass spectrometry. The protein demonstrated in vitro biological activity in the proliferation of human erythroleukemia TF-1 cell test and in vivo activity in animal models. HBD-EPO increased the number of reticulocytes in the blood after subcutaneous injection and displayed local angiogenic activity after subcutaneous implantation of demineralized bone matrix (DBM) discs with immobilized HBD-EPO. We developed a quantitative sandwich ELISA method for measuring HBD-EPO concentration in solution using rabbit polyclonal serum and commercial monoclonal anti-EPO antibodies. Pharmacokinetic properties of HBD-EPO were typical for bacterially produced EPO. Under physiological conditions, HBD-EPO can reversibly bind to DBM, which is often used as an osteoplastic material for treatment of bone pathologies. The data on HBD-EPO binding to DBM and local angiogenic activity of this protein give hope for successful application of HBD-EPO immobilized on DBM in experiments on bone regeneration.

Development of an in vitro Bioassay for Recombinant Human Erythropoietin (rHuEPO) Based on Proliferative Stimulation of an Erythroid Cell Line and Analysis of Sialic Acid Dependent Microheterogeneity: UT-7 Cell Bioassay

Determination of biological activity and its comparison with clinical behavior is important in the quality assessment of therapeutic glycoproteins. In vivo studies are usually employed for evaluating bioactivity of these glycomolecules. However, alternative methods are required to simplify the bioassay and avoid ethical issues associated with in vivo studies. Negatively charged sialic acid residues are known to be critical for in vivo bioactivity of rHuEPO. To address this need, we employed the human acute myeloid leukemia cell line UT-7 for the determination of proliferative stimulation induced by rHuEPO. Relative potencies of various intact and sugar-trimmed rHuEPO preparations were estimated using the International Standard for Human r-DNA derived EPO (87/684) as a reference for bioactivity. The cellular response was measured with a multi-channel photometer using a colorimetric microassay, based on the metabolism of the Resazurin sodium by cell viability. For a resourceful probing of physiological features of rHuEPO with significance, we obtained partly or completely desialylated rHuEPO digested by the neuraminidase enzyme without degradation of carbohydrates. Two-fold higher specific activity was shown by asialoerythropoietin in in vitro analysis compared with the sialoerythropoietin. Further, computational studies were also carried out to construct the 3D model of the erythropoietin (EPO) protein structure using standard comparative modeling methods. The quality of the model was validated using Procheck and protein structure analysis (ProSA) server tools. N-glycan units were constructed; moreover, EPO protein was glycosylated at potential glycosylation amino acid residue sites. The method described should be suitable for potency assessments of pharmaceutical formulations of rHuEPO (European Pharmacopeia, 2016).

Selective functional inhibition of JAK-3 is sufficient for efficacy in collagen-induced arthritis in mice

OBJECTIVE

All gamma-chain cytokines signal through JAK-3 and JAK-1 acting in tandem. We undertook this study to determine whether the JAK-3 selective inhibitor WYE-151650 would be sufficient to disrupt cytokine signaling and to ameliorate autoimmune disease pathology without inhibiting other pathways mediated by JAK-1, JAK-2, and Tyk-2.

METHODS

JAK-3 kinase selective compounds were characterized by kinase assay and JAK-3-dependent (interleukin-2 [IL-2]) and -independent (IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF]) cell-based assays measuring proliferation or STAT phosphorylation. In vivo, off-target signaling was measured by IL-22- and erythropoietin (EPO)-mediated models, while on-target signaling was measured by IL-2-mediated signaling. Efficacy of JAK-3 inhibitors was determined using delayed-type hypersensitivity (DTH) and collagen-induced arthritis (CIA) models in mice.

RESULTS

In vitro, WYE-151650 potently suppressed IL-2-induced STAT-5 phosphorylation and cell proliferation, while exhibiting 10-29-fold less activity against JAK-3-independent IL-6- or GM-CSF-induced STAT phosphorylation. Ex vivo, WYE-151650 suppressed IL-2-induced STAT phosphorylation, but not IL-6-induced STAT phosphorylation, as measured in whole blood. In vivo, WYE-151650 inhibited JAK-3-mediated IL-2-induced interferon-gamma production and decreased the natural killer cell population in mice, while not affecting IL-22-induced serum amyloid A production or EPO-induced reticulocytosis. WYE-151650 was efficacious in mouse DTH and CIA models.

CONCLUSION

In vitro, ex vivo, and in vivo assays demonstrate that WYE-151650 is efficacious in mouse CIA despite JAK-3 selectivity. These data question the need to broadly inhibit JAK-1-, JAK-2-, or Tyk-2-dependent cytokine pathways for efficacy.

Lessons learned from biosimilar epoetins and insulins

Patients with diabetes and renal failure may already be receiving biosimilar epoetin and may receive biosimilar insulin in the near future. Because these biosimilar pharmaceuticals (or follow-on biologics) are complex protein molecules manufactured in lengthy and inherently variable processes involving living organisms, they have the potential to induce an immunogenic, rather than a therapeutic, response. This response is dependent as much on the method of manufacture and formulation, as on the protein itself. Apparently small and innocuous differences in manufacture and formulation can lead to unforeseen clinical consequences. This article discusses two case studies illustrating this principle, that of three insulin formulations which were physicochemically similar to comparator insulins, but with pharmacokinetic and pharmacodynamic profiles sufficiently different to have potentially serious clinical consequences and that of Eprex, for which an apparently minor change in one formulation caused an upsurge of cases of pure red cell aplasia which resulted in fatalities or complete transfusion dependence. Comprehensive and rigorous testing and long-term pharmacovigilance programmes are essential to detect and forestall such consequences.

Biosimilars: recent developments

Biopharmaceuticals are recombinant protein drugs which are produced by biotechnology. The availability of such molecules has revolutionised the way we treat many diseases. However, the patents for many originator biopharmaceuticals are expiring, and a new generation of follow-on molecules, termed "biosimilars", are under development. Health care providers perceive biosimilars to be cheap replacements for originator drugs such as recombinant human erythropoietin and human growth hormone. However, concerns have been raised about the comparability of biosimilars with originator products especially in light of the complex manufacturing process required to produce biopharmaceuticals. The complexity of protein molecules renders it impossible to produce identical copies; this in turn raises questions on the safety of follow-on biosimilar products, particularly with respect to immunogenicity. This review briefly outlines the process of biopharmaceutical production, potential problems that can arise from their long-term use in patients, and the issues facing regulatory bodies as they look to institute guidelines for new biosimilar molecules.

Comparative testing and pharmacovigilance of biosimilars

Unlike traditional generic pharmaceuticals, biosimilars (also called 'follow-on biopharmaceuticals' in the USA) aim to copy a complex recombinant, three-dimensional protein structure with high molecular weight. Small changes in the manufacturing process can alter the product's effect and safety. According to the guidelines of the European Agency for the Evaluation of Medicinal products (EMEA), extensive comparability testing will be required to demonstrate that the biosimilar has a comparable profile in terms of quality, safety and efficacy as the reference product. Various analytical assays are available to compare physicochemical and biological properties between production batches of a potentially similar biopharmaceutical (comparability) and in comparison with a reference product (similarity). It is important to recognize the limits of existing assays so that the results can be accurately interpreted for market authorization. This article examines the quality and limits of such analytical methods. The analytical tests to demonstrate comparability and similarity of a biosimilar product to a reference drug with respect to protein content, activity, physiochemical integrity, stability, impurities and additives, as well as immunogenicity are discussed. Although several assays are available, reliable tests for safety and efficacy still require development. Furthermore, international standards are missing and materials and methods differ from laboratories making the comparison of results very difficult. Clinical trials and post-authorization pharmacovigilance are essential to guarantee the product's safety and efficacy over time. Pharmacovigilance, as part of a comprehensive risk management programme, will need to include regular testing for consistent manufacturing of the drug.