Momelotinib sulfate (CYT387 sulfate salt) is an ATP-competitive inhibitor of JAK1/JAK2 with IC 50 of 11 nM/18 nM, 10-fold selectivity versus JAK3 (IC 50 =155 nM). In Vitro Momelotinib sulfate (CYT387 sulfate salt) inhibits growth of Ba/F3- JAK2 V617F and human erythroleukemia (HEL) cells (IC 50 =1.5 μM) or Ba/F3- MPL W515L cells (IC 50 =200 nM), but has considerably less activity against BCR-ABL harboring K562 cells (IC 50 =58 μM) and FLT3 mutation harboring MV4-11 cells (IC 50 =3 μM). Proliferation of parental Ba/F3 cells (Ba/F3-wt) stimulated with IL-3 is inhibited with an IC 50 value of 1.4 μM, consistent with the established role of IL-3-dependent signaling in the parental cell line. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo Momelotinib sulfate (CYT387 sulfate salt) at twice the dose used in disease model (50 and 100 mg/kg) has little to no effect on peripheral blood counts over a period of 8 weeks. Median plasma peak concentrations are 7.1 μM with the lower dose and 32.1μM with the higher dose, with a half-life of approximately 2 hours. Trough levels at 12 hours are 10nM for the 25 mg/kg and 900nM for the 50 mg/kg dose. At day 34 after transplantation, the mean white blood cell counts and hematocrit values of the entire cohort exceeded the normal range for Balb/c mice by more than 1 SD. At this point, 6 mice are sacrificed and subjected to autopsy. In the remaining animals, treatment is initiated with 25 mg/kg Momelotinib sulfate (CYT387 sulfate salt), 50 mg/kg Momelotinib sulfate (CYT387 sulfate salt), or vehicle, administered twice daily by oral gavage (12 mice per treatment group). A rapid drop of the white cell counts is apparent in both dose cohorts as early as 6 days after initiation of treatment and a decline of the hematocrit is apparent after 20 days. After oral dosing, Momelotinib sulfate (CYT387 sulfate salt) exhibits high plasma concentrations (C max = 40.4 μM; T max =4 h), with quantitative absolute oral bioavailability and an apparent half life of 2.4 h. The high oral bioavailability, can likely be partly ascribed to the low blood clearance of Momelotinib sulfate (CYT387 sulfate salt) (6.3 mL/min/kg) and therefore low susceptibility to hepatic first pass metabolism. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal administration Mice On day 32 after bone marrow transplantation (when all mice exhibit severe leukocytosis and erythrocytosis), mice are assigned to 3 groups such that each group has equivalent average body weight and blood counts. Momelotinib (CYT387) is dissolved in NMP (120 mg/mL final; 1-methyl-2-pyrrolidinone, Chromasolv Plus). Subsequently, the Momelotinib/NMP mix is diluted with 0.14M Captisol to a concentration of 6 mg/mL and further diluted with 0.1M Captisol to a final concentration of 4 mg/mL. All 3 groups of mice (n=12 per group) are administered Momelotinib (CYT387) by oral gavage twice daily at 10- to 12-hour intervals from day 34 after bone marrow transplantation to day 82 (end of experiment). Mice receive NMP/Captisol without Momelotinib (CYT387) (0 mg/kg group), 25 mg/kg Momelotinib, or 50 mg/kg Momelotinib. At day 82 after bone marrow transplantation, all mice are euthanized for analysis except for 2 mice each from the 50 mg/kg and 25 mg/kg groups, which are taken off Momelotinib (CYT387) treatment and followed for 45 additional days. For assessment of the effects of Momelotinib (CYT387) on normal blood counts, naive Balb/c mice are administered vehicle control, 50 mg/kg, or 100 mg/kg Momelotinib (CYT387) in an identical fashion as described for the bone marrow transplant experimental mouse cohort. Peripheral blood is drawn at day 14, 28, 42, and 56 and levels of red cells, white cells, reticulocytes, granulocytes, lymphocytes, and monocytes are analyzed. aladdin has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:JAK1 11 nM (IC 50 ) JAK2 18 nM (IC 50 ) JAK3 155 nM (IC 50 )