Pacritinib (INN, codenamed SB1518) is a Janus kinase inhibitor that is being developed for the treatment of myelofibrosis. It mainly inhibits Janus kinase 2 (JAK2). The drug is in Phase III clinical trials as of 2013[update]. The drug was discovered in Singapore at the labs of S*BIO Pte Ltd. It is a potent JAK2 inhibitor with activity of IC50 = 23 nM for the JAK2WT variant and 19 nM for JAK2V617F with very good selectivity against JAK1 and JAK3 (IC50 = 1280 and 520 nM, respectively)The drug is acquired by Cell Therapeutics, Inc. (CTI) and Baxter international and could effectively address an unmet medical need for patients living with myelofibrosis who face treatment-emergent thrombocytopenia on marketed JAK inhibitors.
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