Comparative Stability Studies of Different Infliximab and Biosimilar CT-P13 Clinical Solutions by Combined Use of Physicochemical Analytical Techniques and Enzyme-Linked Immunosorbent Assay (ELISA)

Background There are two products in which infliximab is the active pharmaceutical ingredient. These are Remicade ® (INF; reference product) and Remsima™/Inflectra™ (CT-P13; infliximab biosimilar). Remsima™/Inflectra™ are bioidentical products. Different recommendations have been made for the clinical solutions of each brand (Remicade ® or Remsima™/Inflectra™) despite the manufacturer of the biosimilar claiming high levels of similarity to the innovator. Objective The objective of this study was to assess and compare stability against degradation and over time of different clinical infliximab solutions prepared from Remicade ® and from Remsima™/Inflectra™ using a suitable set of characterization methods in line with the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) recommendations. Methods Reconstituted solutions of INF and CT-P13 and dilutions as used in hospital were stored in glass vials (10 and 2 mg/mL) or in polyolefin infusion bags (0.4 mg/mL) refrigerated between 2 and 8 °C for 2 weeks. Regarding the physicochemical properties, the distribution of the particulates were studied over a range of 0.001–1 µm by dynamic light scattering (DLS) and oligomers up to 8 monomer were analyzed by native size-exclusion ultra-high-performance liquid chromatography with ultraviolet (UV)-visible detection coupled to (native) mass spectrometry (SE/UHPLC-UV-(native) MS); mass spectrometry was also used to evaluate natural aggregates and isoform profile; DLS was also employed to detect gross conformational changes by tracking the hydrodynamic radius (HR). The secondary structure of the proteins was studied by far UV circular dichroism (CD). The tertiary structure was investigated by intrinsic tryptophan fluorescence (IT-F). Reverse-phase ultra-high-performance liquid chromatography with UV detection (RP/UHPLC-UV) was used to analyze intact INF and CT-P13 for quantification purposes. Functionality was evaluated via the biological activity measured by the extension of the immunological reaction of the INF and the CT-P13 with its antigen, i.e., the tumor necrosis factor-α by enzyme-linked immunosorbent assay (ELISA). Results The stress applied to INF and CT-P13 solutions showed similar levels of aggregate formation, structural variation, and chemical modifications. The only noteworthy difference between INF and CT-P13 was detected in their behavior to freeze–thaw cycles, in which CT-P13 showed slightly more robustness. INF and CT-P13 showed identical CD spectra, similar to those reported for IgG1 in which there is dominance in β sheet secondary structures; this typical conformation remained unmodified over time in INF and CT-P13. No significant changes were detected in the tertiary structure and no aggregates process was noticed over the time studied. Polydispersity slightly increased for the most concentrated solutions, while there were no meaningful differences in the HR in the solutions over time. The concentration of INF and CT-P13 also remained constant. Differences in the native isoform MS profile were detected, as expected by the different glycosylation pattern, with no important modification over time. Functionality was maintained over the test period (60 days) and was similar in all the solutions tested, with no differences between INF and biosimilar solutions. Conclusions High levels of similarity were noticed in the behavior of INF and CT-P13 when subjected to stress. When stored refrigerated at between 2 and 8 °C and prepared as normally used in the hospital pharmacy, all solutions showed physicochemical and functional stability for all the concentrations tested and all containers, at least for the 14-day test period.