Clinical resistance appeared not to be associated with new mutations in the JAK2 kinase drug-binding domain, but was significantly associated with the absence of JAK2, MPL, TET2, and SRSF2 mutations (P = 0.003), and was more common in high-risk MF, post-ET MF, and patients with initially smaller spleen responses [35]. This evidence concerns the gene SRSF2 and essential thrombocythemia.