HAS2 and COVID-19: It has already been reported that dexamethasone and metformin can significantly decrease the mortality of patients with severe COVID-19.30–32 Accordingly, these results may be explained by the reports that dexamethasone and metformin can also rapidly decline hyaluronan synthesis by downregulating HAS2 expression,33,34 which may contribute the therapeutic effects of these two drugs on COVID-19.