Negative impact of hyperglycaemia on tocilizumab therapy in Covid-19 patients

Tocilizumab (TCZ) is used for treating moderate-to-severe Covid-19 pneumonia by targeting interleukin-6 receptors (IL-6Rs) and reducing cytokine release. Yet, in spite of this therapy, patients with vs. patients without diabetes have an adverse disease course. In fact, glucose homoeostasis has influenced the outcomes of diabetes patients with infectious diseases. Of the 475 Covid-19-positive patients admitted to infectious disease departments (University of Bologna, University Vanvitelli of Napoli, San Sebastiano Caserta Hospital) in Italy since 1 March 2020, 31 (39.7%) hyperglycaemic and 47 (60.3%) normoglycaemic patients (blood glucose levels ≥ 140 mg/dL) were retrospectively evaluated at admission and during their hospital stay. Of note, 20 (64%) hyperglycaemic and 11 (23.4%) normoglycaemic patients had diabetes (P < 0.01). At admission, hyperglycaemic vs. normoglycaemic patients had fivefold higher IL-6 levels, which persisted even after TCZ administration (P < 0.05). Intriguingly, in a risk-adjusted Cox regression analysis, TCZ in hyperglycaemic patients failed to attenuate risk of severe outcomes as it did in normoglycaemic patients (P < 0.009). Also, in hyperglycaemic patients, higher IL-6 plasma levels reduced the effects of TCZ, while adding IL-6 levels to the Cox regression model led to loss of significance (P < 0.07) of its effects. Moreover, there was evidence that optimal Covid-19 infection management with TCZ is not achieved during hyperglycaemia in both diabetic and non-diabetic patients. These data may be of interest to currently ongoing clinical trials of TCZ effects in Covid-19 patients and of optimal control of glycaemia in this patient subset.