The ubiquitous involvement of EC in the phenotypic expression and natural history of COVID-19 establishes a firm basis for targeted therapies. Ongoing studies target one or more vascular-specific proteins and signaling pathways, including angiopoietin-2 (NCT04342897), VEGF (NCT 04344782, NCT04275414, and NCT04305106) [87]. Endothelial cell markers of injury and function are included in several of the trials as surrogate or exploratory outcomes. The biomarkers include vascular endothelial growth factor A, vascular endothelial growth factor receptor type 1, Syndecan-1 (marker of glycocalyx degradation), and VWF.