Optimal time of starting tocilizumab in acute phase of adult-onset Still's disease and comparison of its efficacy with that of methotrexate: a case series and a review of the literature.

Adult-onset still's disease is a rare condition that is generally treated by glucocorticoids. Importantly, due to the limited established treatments, glucocorticoid-refractory cases are particularly difficult to treat. Between December 2009 and August 2022, nine patients with adult-onset Still's disease were treated with tocilizumab (tocilizumab group). The therapeutic efficacy and safety of tocilizumab initiation in the acute phase were evaluated in cases of initial onset and recurrence. We also compared the efficacy of tocilizumab with that of methotrexate (methotrexate group, n = 13), which has been the drug of choice for adjunctive therapy. Tocilizumab demonstrated the expected efficacy in all four patients who received it at relapse and in three of the five patients who received it at the initial onset. However, two patients developed macrophage activation syndrome following treatment. A comparison of treatment effects between the methotrexate and tocilizumab groups revealed that the ferritin and C-reactive protein levels, severity score, and glucocorticoid doses decreased over time in both groups; nonetheless, the tocilizumab group experienced a more stable effect. Tocilizumab is undoubtedly a valuable treatment option for adult-onset Still's disease, especially when administered at relapse. This suggests that it shows both high safety and good efficacy. Nevertheless, a larger sample size is required to validate the efficacy and safety of tocilizumab compared with those of the existing alternatives. Key Points • We examined the significance of TCZ in terms of therapeutic efficacy, reduction in glucocorticoid usage, and safety in patients with AOSD. • We compared the therapeutic efficacy of TCZ with that of MTX, which is often used to treat glucocorticoid-resistant AOSD. • TCZ is undoubtedly a valuable treatment option for AOSD, especially when administered at relapse, suggesting both high safety and good efficacy.