In fact, one of the mechanisms of action proposed for the treatment of COVID-19 concerns precisely the ability of azithromycin to inhibit the proliferation of fibroblasts, reduce the production of collagen and the levels of TGF-β (the most important path in the development of fibrosis) and, finally, inhibit the stimulation of the pro-fibrotic gene induced by TGF-β. This evidence concerns the gene TGFB1 and COVID-19.