Development of a sensitive size exclusion HPLC method with fluorescence detection for the quantitation of recombinant human erythropoietin (r-HuEPO) aggregates.

Human erythropoietin produced by recombinant DNA technology, is now marketed worldwide for the treatment of anemias associated with chronic renal failure and chemotherapy. No sensitive methods, which can determine r-HuEPO dimer or oligomer aggregate content in formulated products, have been published to date. This report describes the development and validation of a sensitive size exclusion high performance liquid chromatography (HPLC) method for the quantitation of r-HuEPO aggregates in formulations containing 0.03% polysorbate 80. A Waters Alliance 2690 HPLC system connected to a TosoHaas TSKgel G3000 SWxl (7.8 mm x 30 cm, 250 A pore size, 5 microm particle size) column and a Waters 474 fluorescence detector was used. The mobile phase for the SEC-HPLC method consists of isopropyl alcohol-potassium phosphate (0.1 M)/potassium chloride buffer (pH 6.8+/-0.1, 0.2 M) (25:75, v/v). The flow rate was 0.3 mL/min and the method run time was 60 min. The SEC-HPLC method presented here was shown to be specific for r-HuEPO total aggregates (dimer and oligomers) and allows for their quantitation at 80 ng/mL or 4 ngs/injection, in the presence of r-HuEPO monomer and the pharmaceutical excipients, glycine (5 mg/mL), sodium chloride (4.3 mg/mL), and 0.03% polysorbate 80. The finalized method is stability-indicating and is suitable for determining r-HuEPO aggregates between 0.2 and 0.5% levels in the formulated product of r-HuEPO. This method offers a robust way to measure total aggregates on a routine basis with a high sensitivity for use in product quality control.

Recognition and identification of UV-absorbing leachables in EPREX pre-filled syringes: an unexpected occurrence at a formulation-component interface.

During the period of 1998 to 2002, there was an increase in the incidence of antibody-positive pure red cell aplasia (PRCA) in patients receiving subcutaneous administration of EPREX (epoetinum alfa). As part of the investigation of this event, the aqueous formulation containing polysorbate 80, introduced in 1998, facilitated the leaching of small-molecule, aromatic compounds from the uncoated rubber syringe stoppers. The leachables were identified using Liquid Chromatography-Mass Spectroscopy, Electrospray Ionisation-MS/MS, Dithiothreitol reduction, and Hydrogen/Deuterium exchange. The major leachable was identified as a dialkylphenol disulfide, and the majority of the remaining peaks were identified as structural variants containing different numbers of sulfur atoms in the sulfide bridge. In this report, we describe the strategies and experimental designs that were used to overcome the analytical challenges and that led to successful structural identification of the leachables in EPREX pre-filled syringes with uncoated syringe stoppers.

An in vivo model to assess factors that may stimulate the generation of an immune reaction to erythropoietin.

The incidence of pure red cell aplasia (PRCA) in patients with chronic kidney disease associated with the subcutaneous (s.c.) administration of epoetin alfa (EPREX) began to increase in 1998. As part of an intensive investigation into the reasons for this increase, in vivo models were developed to assess the ability of potential causative factors to stimulate an immune response to recombinant human erythropoietin (rHuEPO). It was difficult to generate anti-EPO antibodies in mice. In animals injected with rHuEPO alone, anti-EPO antibodies were either absent or present at very low levels. The addition of an adjuvant to the immunization protocol was able to increase both the frequency of occurrence and titer of the immune response and resulted in the generation of anti-EPO antibodies that, in most cases, recognized both human and mouse EPO. Some mice exhibited a reduction in hematocrit, suggesting neutralization of endogenous EPO by anti-EPO antibodies. To evaluate the primary lead identified in the technical investigation, leachates from the uncoated syringe stoppers of EPREX syringes, a surrogate antigen (chicken egg albumin, OVA) was used to avoid possible interferences that could arise from the use of an endogenous protein like EPO. These leachates yielded a positive, concentration-dependent antibody response in the OVA animal model, demonstrating their adjuvant properties and providing support for the hypothesis generated through the technical investigation that leachates were capable of enhancing the immune response to rHuEPO.

Interaction of polysorbate 80 with erythropoietin: a case study in protein-surfactant interactions.

PURPOSE: The cause of antibody positive pure red cell aplasia associated with the subcutaneous administration of EPREX to patients with chronic kidney failure has been determined to be due to the leaching of weakly adjuvant compounds from the uncoated rubber stoppers that were formerly used in prefilled syringes. Other researchers have suggested that polysorbate 80 micelles containing erythropoietin may be a causative factor. The purpose of this work was to repeat previously published studies in a more controlled manner and to define the precise nature of the interactions between polysorbate 80 and erythropoietin. METHODS: The contents of EPREX prefilled syringes and laboratory-prepared, well-characterized formulations of EPREX were analyzed by size exclusion chromatography. Fractions were analyzed for the presence of erythropoietin by ELISA. EPREX formulations prepared with increasing amounts of polysorbate 80 were analyzed by light scattering. RESULTS: Well-controlled chromatographic studies showed that when EPREX formulations containing no aggregate were analyzed by high-performance liquid chromatography, erythropoietin monomer could not be detected under the polysorbate 80 peak. Dimer and oligomers of erythropoietin coeluted under the polysorbate 80 peak as the molecular weights overlapped on the size exclusion chromatogram. Solution light scattering indicated that polysorbate 80 associates with erythropoietin in a defined stoichiometric ratio of 1:12. CONCLUSIONS: Based on controlled studies, previous results suggesting that EPREX contains micelle-associated erythropoietin were incorrect. As with other surfactants and proteins, polysorbate 80 associates with erythropoietin in a defined stoichiometric ratio.