Impact of high rheumatoid factor levels on treatment outcomes with certolizumab pegol and adalimumab in patients with rheumatoid arthritis.

OBJECTIVES: To assess the impact of baseline RF level on drug concentrations and efficacy of certolizumab pegol [CZP; TNF inhibitor (TNFi) without a crystallizable fragment (Fc)] and adalimumab (ADA; Fc-containing TNFi) in patients with RA. METHODS: The phase 4 EXXELERATE study (NCT01500278) was a 104-week, randomized, single-blind (double-blind until week 12; investigator-blind thereafter), head-to-head study of CZP vs ADA in patients with RA. In this post hoc analysis, we report drug concentration and efficacy outcomes stratified by baseline RF quartile (≤Q3 or >Q3). RESULTS: Baseline data by RF quartiles were available for 453 CZP-randomized and 454 ADA-randomized patients (≤Q3: ≤204 IU/ml; >Q3: >204 IU/ml). From week 12, the area under the curve (AUC) of ADA concentration was lower in patients with RF >204 IU/ml vs patients with RF ≤204 IU/ml; the AUC of CZP concentration was similar in patients with RF ≤204 IU/ml and >204 IU/ml. For patients with RF ≤204 IU/ml, disease activity score (DAS28)-CRP was similar between CZP- and ADA-treated patients through week 104. For patients with RF >204 IU/ml, mean DAS28-CRP was lower in CZP- vs ADA-treated patients at week 104. The proportion of patients with RF >204 IU/ml achieving DAS28-CRP low disease activity at week 104 was greater in CZP- vs ADA-treated patients. CONCLUSION: CZP was associated with maintained drug concentration and efficacy in patients with RA and high RF and may therefore be a more suitable therapeutic option than TNFis with an Fc fragment in these patients. TRIAL REGISTRATION: Clinicaltrials.gov, http://clinicaltrials.gov, NCT01500278.