Cytokine blockers (infliximab, adalimumab, and ustekinumab) are used to treat immune-mediated diseases that share pathophysiologic mechanisms related to excessive cytokine response. But these treatments increase the risk of viral and bacterial infections and reactivations posing major challenges in the current pandemic. Additionally, COVID-19 morbidity and mortality are higher for people with comorbidities. However, although people taking cytokine blockers should be at higher risk, no increase in viral pneumonia cases have been found to date.
The cytokine profile of severe COVID-19 cases reveals that people taking cytokine blockers could be resistant to this virus. These cases are characterised by a cytokine storm (hyperactivation of effector T cells and excessive production of inflammatory cytokines [IL-6]). In this context, blockade of IL-6 function could have useful therapeutic applications by preventing the harmful inflammation and disseminated intravascular coagulation observed in COVID-19 pneumonia.
The high level of cytokines secreted in a cytokine storm and in COVID-19, which also occur during immune-related disease exacerbations, represent major therapeutic targets. Thus, patients taking IL-6 inhibitors could potentially already be protected against COVID-19 pneumonia.
Pending additional data, physicians should stress that patients with immune-mediated disorders should continue their cytokine blocking treatment and should self-isolate because these treatments are not proven to confer protection against infection.