ABSTRACT
BACKGROUND: RTXM83 is a rituximab biosimilar with proven clinical safety and efficacy. It is the first rituximab biosimilar developed and approved in South America and is currently marketed in several Latin American, Middle Eastern and African countries. OBJECTIVE: The aim of this study was to present the physicochemical and biological characterization studies utilized to demonstrate the similarity between RTXM83 and its reference product. METHODS: Primary and higher order protein structures were analysed using peptide mapping with liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), fluorescence spectroscopy and circular dichroism, and micro-differential scanning calorimetry, among other techniques. Charge variants were determined by cation-exchange chromatography (CEX) and capillary isoelectric focusing (cIEF). Glycosylation and glycoforms distribution were analysed using MS, normal phase high-performance liquid chromatography (NP-HPLC) and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). Size variants were evaluated by size-exclusion chromatography (SEC), sedimentation velocity analytical ultracentrifugation (SV-AUC), dynamic light scattering (DLS), and capillary electrophoresis-sodium dodecyl sulfate (CE-SDS). Biological characterization included binding assays for complement C1q, CD20, and several Fc receptors (FcRs), as well as potency determination for in vitro apoptosis induction, complement-dependent cytotoxicity (CDC), and antibody-dependent cell-mediated cytotoxicity (ADCC). RESULTS: RTXM83 and the reference product showed identical primary sequences and disulfide bridge patterns, and similarity at higher order protein structures, post-translational modification profiles (amino acid modifications, charge variants, and glycosylation) and levels of purity and process-related impurities. Functional studies demonstrated that RTXM83 is similar to the reference product regarding the three known mechanisms of action of rituximab: CDC, ADCC, and apoptosis induction. Binding affinities to CD20, complement component C1q, and different FcRs were also equivalent. CONCLUSION: RTXM83 is similar to its reference product in all critical quality attributes.
Subject(s)
Biosimilar Pharmaceuticals/chemistry , Biosimilar Pharmaceuticals/therapeutic use , Rituximab/chemistry , Rituximab/therapeutic use , Antibody-Dependent Cell Cytotoxicity/physiology , Antigens, CD20/metabolism , Chromatography, High Pressure Liquid/methods , Circular Dichroism/methods , Complement C1q/metabolism , Dynamic Light Scattering/methods , Electrophoresis, Capillary/methods , Glycosylation , Humans , Peptide Mapping/methods , Receptors, Fc/metabolism , Tandem Mass Spectrometry/methods , Ultracentrifugation/methodsABSTRACT
BACKGROUND: Biosimilars are described as biological products that resemble the structure of original biologic therapeutic products, with no clinically meaningful differences in terms of safety and effectiveness from the original. A wide range of biosimilars are under development or are already licensed in many countries. Biosimilars are earning acceptance and becoming a reality for immunotherapy treatments mainly based on the alternatives for the commercial anti-CD20 monoclonal antibody rituximab. The most important mechanism of action reported for this antibody is the induction of antibody-dependent cell cytotoxicity (ADCC), which is associated with the polymorphisms present at the 158 position in the IgG receptor FcγRIIIa. OBJECTIVE: The aim of the study was to validate the functional comparability between the proposed rituximab biosimilar RTXM83 and the original product. To achieve this we assessed the binding capacity and ADCC induction of this biosimilar, taking into account the different FcγRIIIa-158 polymorphisms. METHODS: Binding capacity was evaluated by flow cytometry using CD20 positive cells and a wide range of antibody concentrations. The FcγRIIIa-158 polymorphisms were analyzed by polymerase chain reaction (PCR) followed by allele-specific restriction enzyme digestion. ADCC was measured by a colorimetric lactate dehydrogenase-release assay, using effector cells from donors with different FcγRIIIa-158 polymorphisms. RESULTS: Binding capacity assay showed no differences between both products. Regarding ADCC, a similar relative potency was obtained between both antibodies, showing a higher response for the FcγRIIIa-158 valine/valine (V/V) polymorphism compared to the phenylalanine/phenylalanine (F/F), for both rituximab and RTXM83. CONCLUSION: Our data strongly suggest the biocomparability between the proposed biosimilar and the originator rituximab, in antibody recognition and ADCC activity. Additionally, our results suggest that donors with the FcγRIIIa-158V/V polymorphism induce a higher ADCC response, as has been reported.
