Tocilizumab and Thromboembolism in COVID-19: A Retrospective Hospital-Based Cohort Analysis

Background Tocilizumab, an interleukin-6 (IL-6) receptor antagonist, has been used in patients with coronavirus disease 2019 (COVID-19) as an anti-cytokine agent. IL-6 also plays a complex role in hemostasis and thrombosis. We observed a transient elevation of D-dimer in our patients who received tocilizumab, which triggered this study. Methods A retrospective hospital-based cohort analysis of patients with confirmed COVID-19 who received tocilizumab during the study period of March 15, 2020, to May 20, 2020, was conducted. We retrieved demographic, clinical, and laboratory data, and patients who were receiving therapeutic anticoagulation therapy prior to tocilizumab administration were excluded. Descriptive analysis was performed, and the cause of death and trends of D-dimer and inflammatory markers were studied. Results Out of the 436 confirmed COVID-19 patients admitted during the study period, 24 met the inclusion criteria. Their median age was 47.5 years. They were 18 males and 6 females; 15 patients survived and nine expired. Of the group that survived, 12 received therapeutic anticoagulation. Of the seven patients who did not receive therapeutic anticoagulation, four expired (one from sepsis and three probably from thromboembolic complications) compared to five deaths in the 17 patients who received therapeutic anticoagulation (four from sepsis and one possibly from thromboembolic complications). Conclusions The interplay between IL-6, IL-6 receptor antagonist, and venous thromboembolism is complex. We observed a transient elevation of D-dimer in COVID-19 patients who received tocilizumab, and a trend toward increased death secondary to thromboembolism. This observation is novel and highlights the potential thrombophilic side effects of tocilizumab.