Fedratinib (SAR302503, TG101348) is a selective inhibitor of JAK2 with IC50 of 3 nM in cell-free assays, 35- and 334-fold more selective for JAK2 versus JAK1 and JAK3. Fedratinib also inhibits FMS-like tyrosine kinase 3 (FLT3) and RET (c-RET) with IC50 of 15 nM and 48 nM, respectively. Fedratinib has potential antineoplastic activity. Fedratinib inhibits proliferation and induces apoptosis. Phase 2.