PM-43I

**PM-43I** is a potent, cell-permeable, phosphatase-stable small-molecule phosphopeptide mimetic that directly inhibits **STAT6** by targeting its Src homology 2 (SH2) domain, preventing phosphorylation at Tyr641 and blocking docking to IL-4Rα. Developed by researchers at Baylor College of Medicine, MD Anderson Cancer Center, and Atrapos Therapeutics, it also inhibits **STAT5** (IC50 ~3.8 μM) with molecular formula C38H50F2N3O10P (MW 777.8, CAS 1637532-77-4). In preclinical mouse models, PM-43I reverses preexisting allergic airway disease with ED50 0.25 μg/kg via intranasal aerosol, persists in lungs >24h, clears renally without toxicity, and controls asthma without steroids or immunosuppression.[1][2][3][4][5]