Tocilizumab for Patients with Severe Fever with Thrombocytopenia Syndrome: Tocilizumab Observational SFTS Study-1.

There is no established treatment for severe fever with thrombocytopenia syndrome (SFTS). However, the potential role of tocilizumab (TCZ) in cytokine storm modulation warrants further investigation. In this study, we aimed to investigate the therapeutic potential of TCZ in adult patients with SFTS and provide valuable insights into the development of effective treatment strategies for this challenging infectious disease by assessing the impact of TCZ on cytokine dynamics and patient outcomes. This prospective longitudinal observational study included adult patients with SFTS at a teaching hospital in Korea between April 2013 and December 2023. Patients with SFTS and interleukin (IL)-6 levels ≥30 ng/mL received TCZ. The 14- and 28-day mortality rates were compared between the TCZ and therapeutic plasma exchange (TPE) groups during the study period. Among the total of 97 patients, the clinical characteristics showed no significant differences between the TCZ (n=10) and TPE groups (n=30). Compared with TPE, TCZ treatment showed a trend towards lower mortality rate (14-day mortality rate: 10.0% vs. 16.7%, =0.608; 28-day mortality rate: 10.0% vs. 20.0%, =0.480). Both treatments showed the potential to reduce the viral load and IL-6 levels, indicating their efficacy in managing the disease course. TCZ is a potential therapeutic option for SFTS as it modulates IL-6 levels and improves clinical outcomes.