Lack of association between rheumatoid factor levels and clinical response to certolizumab pegol in patients with rheumatoid arthritis: an observational study
Abstract
Background Patients with rheumatoid arthritis (RA) generally have elevated levels of rheumatoid factor (RF), which binds to the crystallizable fraction (Fc) of monoclonal antibodies, diminishing tumour necrosis factor inhibitor (TNFi) efficacy. We assessed clinical response to PEGylated, Fc-free certolizumab pegol (CZP) across baseline RF levels in Brazilian patients with RA. Methods Reported patients (>6 months disease duration) received CZP (200 mg every 2 weeks [Q2W] or 400 mg Q4W) after failure or intolerance to conventional synthetic or biologic disease-modifying antirheumatic drugs. Data were collected from medical records before initiation, at 3 months and at 6 months of CZP. Patients were stratified by baseline RF quartiles. Disease activity was assessed by the Clinical Disease Activity Index (CDAI). Results Amongst 51 patients, 49 (96.1%) were women, the mean age (standard deviation [SD]) was 49.8 (13.7) years and 23 (45.1%) were receiving methotrexate. RA duration (SD) was 17.0 (9.5) years. Of 43 patients with baseline RF values, mean RF (SD) was 224.3 (363.5) IU/mL. At baseline, 3 months and 6 months, CDAI for patients overall was 18.6 (10.4), 9.8 (8.6) and 12.5 (11.7); for those with baseline RF≤Q3 (n=34) versus >Q3 (n=9), CDAI was 18.4 (11.0) versus 20.0 (10.7), 9.2 (7.9) versus 8.4 (9.8) and 12.8 (13.2) versus 10.9 (8.9). CDAI remission/low disease activity rates at baseline, 3 months and 6 months were 4.1%/18.4%, 23.4%/29.8% and 11.9%/40.5%; for those with baseline RF≤Q3 (n=34) versus >Q3 (n=9), CDAI remission/low disease activity rates were 2.9%/20.6% versus 11.1%/0.0% at baseline, 30.3%/24.2% versus 12.5%/50.0% at 3 months and 14.3%/42.9% versus 12.5%/37.5% at 6 months. Conclusion Baseline RF values did not appear to influence CZP clinical response in this cohort of patients with RA. However, small sample size and data heterogeneity restricted generalizability. Efficacy data from larger cohorts may further elucidate the impact of high RF levels in patients receiving Fc-free biologics.