Objective To study the efficacy and safety of certolizumab pegol (CZP) in patients with active rheumatoid arthritis (RA) who had discontinued an initially effective TNF inhibitor (TNF-IR).

Methods A randomised 12-week double-blind trial with CZP (n=27) or placebo (n=10) followed by an open-label 12 week extension period with CZP.

Results Baseline characteristics ofthe 2 groups were similar. ACR20 response (primary end point) at week 12 was achieved in 61.5%, and none of CZP and placebo-treated patients, respectively. Weeks 12–24 showed a maximum effect for CZP at 12 weeks, and that placebo patients switched blindly to CZP attained similar results seen with CZP in weeks 0–12. Since this result was highly significant, study inclusion was terminated after entry of 33.6% of the originally planned 102 patients. Adverse events occurred in 16/27 (59.3%) CZP subjects and 4/10 (40%) placebo subjects. There were no serious adverse events, neoplasms, opportunistic, or serious infections.

Conclusions This first, prospective, blinded trial of CZP in secondary TNF-IR shows that the ACR20 response rate observed with CZP was higher than that reported in most previous studies of TNF-IR. Additionally, CZP demonstrated good safety and tolerability. This study supports the use of CZP in RA patients who are secondary non-responders to anti-TNF therapies.