Do high rheumatoid factor levels impact response to certolizumab pegol in patients with inadequately controlled rheumatoid arthritis? A post hoc analysis of the phase IIIb REALISTIC trial.

OBJECTIVES: To assess the impact of rheumatoid factor (RF) levels and previous inadequate responses/intolerance to tumour necrosis factor inhibitors (TNFi-IR) on the efficacy of certolizumab pegol (CZP) in patients with rheumatoid arthritis (RA) through a post hoc analysis of the RA Evaluation in Subjects Receiving TNF Inhibitor CZP (REALISTIC) trial. METHODS: In the phase IIIb REALISTIC trial, patients with RA were randomised to CZP (400 mg at weeks 0, 2 and 4, then 200 mg every 2 weeks) or placebo (PBO) for 12 weeks, followed by open-label CZP (minimum 16 weeks). Outcomes reported to week 36 include Disease Activity Score 28 C-reactive protein (DAS28-CRP) and Clinical Disease Activity Index (CDAI) scores, rates of DAS28-CRP <2.6 and CDAI remission (CDAI ≤2.8) and components of each. Data were stratified by baseline RF level (≤3rd quarter (≤Q3; <180 kU/L) vs 4th quarter (Q4; 'high RF'; ≥180 kU/L)) and prior TNFi use (TNFinaïve vs TNFi-IR). RESULTS: A total of 930 patients were included: 751 CZP-randomised and 179 PBO-randomised. At week 12, CZP-randomised patients experienced marked and similar improvements in disease activity, irrespective of RF level and prior TNFi use, while PBO-randomised patients did not. Responses generally improved through week 36 in CZP-treated patients (including PBO-randomised switchers), with similar efficacy across subgroups. CONCLUSIONS: Patients with high and low RF levels experienced similar clinical responses to CZP treatment, irrespective of previous inadequate responses or intolerance to TNFis. These findings expand previous observations, supporting CZP as an effective treatment for patients with RA who have high RF levels and prior inadequate responses to TNFis. TRIAL REGISTRATION NUMBER: NCT00717236.