However, it does not exclude the possibility that DPP4 inhibition may indirectly attenuate the severity of COVID-19, due to the role that DPP4 plays in the pathophysiology of common comorbidities in patients with COVID-19 (Ryskjaer et al., 2006; Dos Santos et al., 2013; Zhong et al., 2013), including hypertension. Here, DPP4 is linked to hypertensive disorder.