Supplementary Material for: Tocilizumab Treatment Effect on Iron Homeostasis in Severe COVID-19 Patients

Background: Tocilizumab has been proposed as an effective treatment for severe COVID-19. We aimed to investigate whether tocilizumab administration is associated with increased availability of serum iron which may possibly be associated with adverse effects on clinical outcomes.
Methods: We performed an observational, retrospective cohort study. We included adults, who were hospitalized in ICU with the diagnosis of severe COVID-19 infection eligible for tocilizumab treatment. Laboratory data including serum iron, ferritin, transferrin saturation, hemoglobin and CRP levels of all patients were collected shortly before and 24h, 48h and 72h after tocilizumab administration.
Results: During the study period fifteen patients fulfilled the inclusion criteria and were eligible to receive tocilizumab treatment. Tocilizumab therapy was associated with a prominent increase in serum iron and transferrin saturation levels (26±13 μg/dL and 15 ±8% before treatment and 79±32 μg/dL and 41±15% 72h after treatment, respectively P<0.001) and decrease in serum ferritin levels (1921±2071 ng/mL before and 1258±1140 ng/mL 72h after treatment, P=0.027).
Conclusion: Treatment of severe COVID-19 patients with tocilizumab is associated with a profound increase in serum iron and ferritin saturation levels along with a decrease in ferritin levels. This may represent an undesirable side effect that may potentiate viral replication.