ABSTRACT
Summary A fraction of COVID-19 patients develop the most severe form, characterized by Acute Respiratory Disease Syndrome (ARDS). The molecular mechanisms causing COVID-19-induced ARDS have yet to be defined, though many studies have documented an increase in cytokines known as a “cytokine storm.” Here, we demonstrate that cytokines that activate the NF-kappaB pathway can induce Activin A and its downstream marker, FLRG. In hospitalized COVID-19 patients elevated Activin A/FLRG at baseline were predictive of the most severe longitudinal outcomes of COVID-19, including the need for mechanical ventilation, lack of clinical improvement and all-cause mortality. Patients with Activin A/FLRG above the sample median were 2.6/2.9 times more likely to die, relative to patients with levels below the sample median, respectively. The study indicates high levels of Activin A and FLRG put patients at risk of ARDS, and blockade of Activin A may be beneficial in treating COVID-19 patients experiencing ARDS.