FLT3 and myelofibrosis: Pacritinib is a small-molecule, ATP-competitive, macrocyclic inhibitor of JAK2 (IC50 23 nM), FMS-like tyrosine kinase 3 (FLT3; IC50 22 nM), IRAK1 (IC50 6 nM), and IRAK4 (IC50 177 nM) [36, 37] that has been FDA (Food and Drug Administration, USA) approved for the treatment of myelofibrosis marked by severe thrombocytopaenia.