Potently and directly inhibits JAK2 tyrosine kinase autophosphorylation, specifically inhibiting ligand-dependent JAK2 activation. A 16-hour treatment with 1 μM of compound reduces JAK2 tyrosine autophosphorylation levels to ~ 50% while 50 μM elimates nearly all JAK2 activity. Non-cytotoxic at 100 μM.