Risk of serious infection, malignancy, or death in Japanese rheumatoid arthritis patients treated with a combination of abatacept and tacrolimus: a retrospective cohort study

To evaluate whether combinatorial use of abatacept (ABT) and tacrolimus (Tac) increases the risk of adverse events compared to their individual use in Japanese rheumatoid arthritis (RA) patients. We conducted a retrospective cohort study of RA patients using the Japanese multicenter database and analyzed the data of RA patients registered from April 2010 to March 2019 by comparing three treatment groups who received Tac, ABT, or a combination of both. We included patients who had initiated treatment with ABT or Tac and excluded patients who used tumor necrosis factor inhibitors, IL-6 inhibitors, and Jak inhibitors in the first year of our study. The primary outcome was the occurrence of adverse events such as infections that required hospitalization, newly diagnosed malignancy, or death from any cause after initiation of ABT or Tac. Of the 27,032 RA patients in the registry, 2009 patients were included. The Tac, ABT, and combination groups consisted of 1328, 563, and 118 patients, respectively. Primary outcome occurred in 149 (13.4%), 62 (13.5%), and 14 (13.9%) patients of the Tac, ABT, and combination groups, respectively. The incidence of adverse events between groups was not significantly different (p = 0.638). A Cox regression analysis which was adjusted for potential confounders such as age, disease activity, and concomitant use of prednisolone revealed no significant differences between groups. The combinatorial use of ABT and Tac, or ABT alone does not increase the risk of adverse events when compared to the use of Tac alone in RA patients in Japan.