Tocilizumab to Prevent the Progression of Hypoxemic Respiratory Failure in Hospitalized Non-Critically Ill Patients With COVID-19

As of April 3, 2020, COVID-19 has been confirmed in over 1 million people worldwide, with an estimated symptomatic case fatality ratio of around 1.4%. Currently without an effective treatment for SARS-CoV-2 there is an urgent need for effective treatment to curtail the rate of respiratory failure, the leading cause of mortality in COVID-19 disease. Moreover, with increasing numbers of patients requiring intensive unit level care and mechanical ventilation, nations are already having to triage patients for ventilatory support due to limited resources and healthcare systems around the world being stretched to the point of collapse, highlighting the importance of identifying interventions that could prevent the development of respiratory failure for these patients.

The disease course of COVID-19 includes an incubation period, an acute viral phase that most commonly presents with flu-like symptoms that in some individuals progresses to a severe hyperinflammatory phase marked by acute respiratory distress syndrome (ARDS) and hypoxemic respiratory failure.Though there is spectrum of clinical course, many progress to the hyperinflammatory phase around day seven of symptoms, often requiring intensive care unit (ICU) level care and mechanical ventilation. Accumulating evidence suggests that the pathophysiology underlying this profound decline is a severe inflammatory response as demonstrated by multi organ system dysfunction akin to cytokine release syndrome (CRS)/macrophage activation syndrome (MAS).CRS/MAS is a systemic hyperinflammatory syndrome on a spectrum with secondary hemophagocytic lymphohistiocytosis (sHLH), typically characterized by multiorgan failure that is often triggered by viral infections in the setting of excessive immune activation, typically with marked hyperferritinemia.Postmortem assessment of patients with COVID-19 have demonstrated pathologic findings consistent with MAS such as mono/lymphocytic infiltrates within the lung parenchyma with associated edema and alveolar congestion, splenic necrosis with macrophage proliferation and hemophagocytosis, as well as a lymphocyte/histiocyte predominate infiltrate of portal vasculature accompanying liver necrosis and sinusoidal congestion.Cytokine profiling of patients with MAS/sHLH overlaps with that seen in patients with severe COVID-19 and includes elevated levels of IL-1, IL-2, IL-7, IL-6, G-CSF, MCP- 1, and TNF-α as well as elevated D-dimer, C-reactive protein, LDH and troponins.Moreover, preliminary data from a non-randomized series of COVID-19 patients with "severe or critical COVID-19" from China who were treated with tocilizumab (in addition to standard therapies) showed they had dramatic improvement in fever, arterial oxygen saturation and inflammatory markers within the first 24-hours following administration.

Taken together, these data strongly suggest an immunologic link between COVID-19 and immune dysregulation resulting in MAS. Clinical trials are already underway studying the role of immunomodulatory therapy including modulation of IL-1 and IL-6 and downstream pathways in the setting of CAR-T induced MAS (NCT04150913, NCT04071366) and agents such anakinra and tocilizumab have been used in this context with promising results and good safety profiles. There is an urgent and dire need to study the therapeutic role for immunomodulatory therapy in COVID-19 disease to both halt disease progression in patients at an individual level and prevent the inevitable saturation of healthcare resources at a systems level, to which end there are numerous ongoing international trials to expand these efforts into the setting of COVID-19 infection (ChiCTR2000029765, NCT04324021, TOCOVID-19). Based on the MGH experience thus far with COVID-19, including over 200 patients to date, the need for mechanical ventilation has been approximately 30%. With the upcoming surge anticipated between April 17th and 21st we expect the need for hundreds of additional ICU beds. Investigators propose a trial of IL-6 receptor blockade with tocilizumab given early in disease course to try to prevent progression of COVID-19.