Anemia as an indicator of a higher retention rate for tocilizumab versus tumor necrosis factor inhibitors in patients with rheumatoid arthritis from a Korean multi-center registry.

Objective: To examine whether simple laboratory tests can guide selection between tocilizumab (TCZ) and tumor necrosis factor inhibitors (TNFi) in biologic-naive patients with rheumatoid arthritis (RA), by investigating their influence on drug retention. Methods: Data of RA patients prescribed TCZ or TNFi as the initial biologics from March 2013 to December 2021 were obtained from the KOrean College of Rheumatology BIOlogics and Targeted Therapy (KOBIO) registry. Propensity score matching was performed to adjust for baseline confounding factors. Hazards of drug discontinuation for TCZ were calculated compared to those for TNFi. Interaction analyses with a Bonferroni-corrected p-value threshold were conducted to determine whether the hemoglobin level, C-reactive protein level, erythrocyte sedimentation rate, and platelet count affected the hazards of drug discontinuation. Results: Overall, 893 patients were analyzed, of whom 315 and 578 were treated with TCZ and TNFi, respectively. The hazards of drug discontinuation in all patients were lower for TCZ than for TNFi (hazard ratio [HR] 0.53, 95% confidence interval [CI] 0.44~0.66). Notably, only the presence of anemia indicated a significant interaction (p for interaction=0.010); the HRs for drug discontinuation were 0.41 (95% CI 0.30~0.55) and 0.70 (95% CI 0.53~0.92) in the anemic and non-anemic groups, respectively. In the anemic subgroup, biologics were discontinued because of a lack of efficacy in 35.0% of TNFi initiators and 7.4% of TCZ initiators.Conclusion The drug discontinuation rate in biologic-naïve patients with RA was significantly lower for TCZ than for TNFi, particularly in those with anemia.