It is unknown whether the degree of anti-drug antibody (ADA) development is different between patients with Ankylosing Spondylitis (AS) and Rheumatoid Arthritis (RA).
At ACR 2014, a late breaking poster abstract has finally provided a clue to this question (abstract L21). The data were obtained from 2 recent trials that evaluated the biosimilarity between infliximab and CT-P13. There was no difference in ADA development between infliximab and CT-P13, but there was a difference between the two patient types. In patients with RA, 55-56% were found to have ever developed an ADA over a 54-week period (despite MTX use) vs. 32-34% of patients with AS. This difference was statistically significant.
This is the first study to describe the discrepancy in ADA development between patients with AS and RA. Although the etiology for this difference is not entirely clear, it is a pretty interesting observation!