Epitope Mapping for a Preclinical Bevacizumab (Avastin) Biosimilar on an Extended Construct of Vascular Endothelial Growth Factor A Using Millisecond Hydrogen-Deuterium Exchange Mass Spectrometry.

The success of bevacizumab (Avastin), a monoclonal antibody (mAb) anticancer drug targeting vascular endothelial growth factor A (VEGF-A), has motivated the development of biosimilars. Establishing target epitope similarity using epitope mapping is a critical step in preclinical mAb biosimilar development. Here we use time-resolved electrospray ionization hydrogen-deuterium exchange (HDX) mass spectrometry to rapidly compare the epitopes of commercial Avastin and a biosimilar in preclinical development (ApoBev) on an extended construct of VEGF-A. The Avastin and ApoBev epitopes determined in our experiments agree with each other and with the known epitope derived from the Avastin Fab domain/truncated VEGF co-crystal structure. However, subtly different allosteric effects observed exclusively at short (millisecond) HDX labeling times may reflect a slightly different binding mode for ApoBev.

Part 2: Physicochemical characterization of bevacizumab in 2 mg/mL antibody solutions as used in human i.v. administration: Comparison of originator with a biosimilar candidate.

The physicochemical properties of Avastin® manufactured in the USA (Originator USA) and in Europe (Originator EU) and ABX-BEV, a bevacizumab biosimilar drug product candidate produced by Apobiologix Inc., were characterized at a clinically relevant concentration of 2 mg/mL following dilution of the 25 mg/mL drug products with 0.9% NaCl. Measurements using 14 orthogonal analytical methods performed within 5 h after dilution showed good similarity of the three antibodies as regards secondary structure, conformation, aggregation properties, subvisible and visible particles. No significant protein aggregation was observed within 5 h at 24 °C in the 2 mg/mL bevacizumab solutions. The same solutions that were measured within 5 h after dilution were analyzed again after 24 h overnight refrigeration at 2-8 °C: all 2 mg/mL bevacizumab solutions showed an increase in the number and sizes of aggregates, especially the particles larger than 10 µm and 25 µm. The data show the very good similarity in the physicochemical properties of ABX-BEV with Originators USA and EU at a clinically relevant concentration.

Part 1: Physicochemical characterization of bevacizumab in undiluted 25 mg/mL drug product solutions: Comparison of originator with a biosimilar candidate.

The biosimilarity assessment of the physicochemical properties of high-concentration biopharmaceuticals is usually performed with measurements on diluted solutions, at concentrations below 1 mg/mL. In this study 13 orthogonal, spectroscopy and particle size determination methods were used to characterize the structure and aggregation of undiluted, 25 mg/mL bevacizumab drug products Avastin® manufactured in the USA and in Europe, and ABX-BEV, a bevacizumab biosimilar candidate produced by Apobiologix Inc. Secondary structure, conformation and the potential occurrence of chemical degradation of the monoclonal antibodies were characterized and compared using infrared spectroscopy, intrinsic fluorescence and ANS fluorescence spectroscopy. Protein aggregation and particulate matter in the monoclonal antibody solutions were compared using UV-Vis absorbance, 90° light-scattering, nanoparticle tracking analysis, Nile red fluorescence microscopy, particle flow imaging, ultrasound resonance technology and a new scanner-based method that visualizes protein aggregates inside unopened vials. A data wheel representation was used to plot in one figure the results from the multiple analytical methods and to highlight differences between samples. The 25 mg/mL Avastin® drug product is stored at 2-8 °C during its 2-year shelf life. After a thermal stress of 4 weeks at 40 °C the ABX-BEV solution was turbid, containing particles of 20-100 µm diameter, accompanied by strong changes in antibody structural properties. Characterization of unstressed samples stored at 2-8 °C showed that the physicochemical properties of bevacizumab in ABX-BEV and the two originator drug products were similar, the observed differences between the originators being in the same range as those between ABX-BEV and the originator. To investigate the similarity of the antibodies under stress conditions, a freeze-thaw study was performed. Although freeze-thawing of bevacizumab products is prohibited by the package insert, after two freeze-thaw cycles (24 °C to -80 °C) small changes in the structural and aggregation properties of bevacizumab were observed, changes that were similar for the originator and ABX-BEV. Our study showed a good similarity of the investigated physicochemical properties of bevacizumab in originator and ABX-BEV products. It also provides an analytical approach, based on orthogonal methods, to compare high-concentration formulations of monoclonal antibodies.

Rapid characterization of structural and functional similarity for a candidate bevacizumab (Avastin) biosimilar using a multipronged mass-spectrometry-based approach.

The ongoing shift from small molecule drugs to protein therapeutics in the pharmaceuticals industry presents a considerable challenge to generic drug developers who are increasingly required to demonstrate biosimilarity for biological macromolecules, a task that is decidedly more complex than doing the same for small molecule drugs. In this work, we demonstrate a multipronged mass-spectrometry-based workflow that allows rapid and facile molecular characterization of antibody-based protein therapeutics, applied to biosimilars development. Specifically, we use a combination of native mass spectrometry (MS), ion mobility spectrometry (IMS), and global time-resolved hydrogen deuterium exchange (HDX) to provide an unambiguous assessment of the structural, dynamic, and chemical similarity between Avastin (bevacizumab) and a biosimilar in the late stages of pre-clinical development. Minor structural and dynamic differences between the biosimilar and Avastin, and between lots of the biosimilar, were tested for functional relevance using Surface Plasmon Resonance-derived kinetic and equilibrium binding parameters.