Background: The angiotensin II type 2 receptor (AT2R) agonist, Compound 21 (C21), has well-established anti-fibrotic and organ-protective actions that have led to its clinical evaluation for various indications, including COVID-19, systemic sclerosis, and idiopathic pulmonary fibrosis (IPF). The gene discussed is AGTR2; the disease is COVID-19.