Potent, selective inhibitor of Janus tyrosine kinase 3 (JAK3). pIC50 values are 7.1, 5.6, 4.4, and < 5.0 for JAK3, EGFR, JAK1 and CDK4 respectively. Breaks down in neutral buffer (t½ = 36 mins, pH 7.43, 25°C) to form ZM 449829 (Cat. No. 1366).