Retention of the second-line biologic disease-modifying antirheumatic drugs in patients with rheumatoid arthritis failing one tumor necrosis factor alpha inhibitor: data from the BioRx.si registry.

This study aimed to investigate the retention of the second-line biologic disease-modifying antirheumatic drugs (bDMARDs) in rheumatoid arthritis patients failing their first tumor necrosis factor alpha inhibitor (TNFi). Data was extracted from the Slovenian registry (BioRx.si) on December 15, 2012. Baseline patient characteristics were compared between second-line TNFi and non-TNFi, and potential confounders were identified by the means of binary logistic regression. Differential drug retention was assessed using the Kaplan-Meier method and crude and inverse probability-weighted Cox proportional hazards regression models (Cox model). Two hundred thirty-eight out of 688 patients who received a TNFi as the first biologic were switched to another biologic: 130 to a second-line TNFi and 108 to either rituximab (31.5 %) or tocilizumab (68.5 %) (non-TNFi). Disease activity at starting second-line bDMARD and stopping the first-line TNFi due to either lack of effectiveness or loss of effectiveness were identified as potential confounders. There appears to be a statistically significant retention advantage of the non-TNFi over the second-line TNFi (log rank test, p = 0.000). This advantage is retained even after taking into account the possible effect of confounders which was tested using the inverse probability-weighted Cox model [hazard ratio (HR) 4.39; 95 % confidence interval (CI) 2.62-8.01, p < 0.001]. After the first-line TNFi's failure, a second-line TNFi is more likely to fail earlier than non-TNFi.