Background: Infliximab (IFX) biosimilars CT-P13 and SB2 have comparable efficacy, safety, and immunogenicity to the originator Remicade (RMC). However, concerns about cross-switching patients between the 3 brands were raised in the absence of cross reactivity data between them. We aimed to determine whether antibodies to infliximab (ATI) in inflammatory bowel disease (IBD) patients cross-react with RMC, CT-P13, and SB2.
Methods: Based on previous ATI status, samples from 34 patients participating in the BIOSIM01 study (13 RMC, 9 CT-P13, and 12 switchers) were selected. Patients were treated with either RMC only, or CT-P13 only, or with RMC switched to CT-P13. Additionally, 28 IFX-naïve patients were assayed as controls. In total, 180 samples were analyzed. ATI trough levels were measured in parallel with 3 different bridging Enzyme Linked Immunosorbent Assays constructed using the 3 drugs. Spearman's coefficient and percentages of agreement were used to study the correlation between each assay.
Results: In total, 76 samples out of 152 IFX-treated patient samples were ATI-positive (30 RMC, 14 CT-P13, and 32 switchers). All resulted ATI-positive when either CT-P13 or SB2 bridging assays were used. The overall percentage of agreement was 100% when compared either with CT-P13 or SB2 assays. No significant differences were found among ATI levels and coefficients (Spearman's 0.98 to 1.0, P < 0.0001).
Conclusions: ATI of RMC-treated, CT-P13-treated or RMC to CT-P13 switched patients show full cross-reactivity with CT-P13 and SB2. Findings suggest that immunodominant epitopes in the reference and CT-P13 drugs are equally present in SB2. Data support full interchangeability between biosimilars in regard to immunogenicity.