Characterization of BMS-911543, a functionally selective small-molecule inhibitor of JAK2

Abstract

We report the characterization of BMS-911543, a potent and selective small-molecule inhibitor of the Janus kinase (JAK) family member, JAK2. Functionally, BMS-911543 displayed potent anti-proliferative and pharmacodynamic (PD) effects in cell lines dependent upon JAK2 signaling, and had little activity in cell types dependent upon other pathways, such as JAK1 and JAK3. BMS-911543 also displayed anti-proliferative responses in colony growth assays using primary progenitor cells isolated from patients with JAK2 V617F -positive myeloproliferative neoplasms (MPNs). Similar to these in vitro observations, BMS-911543 was also highly active in in vivo models of JAK2 signaling, with sustained pathway suppression being observed after a single oral dose. At low dose levels active in JAK2-dependent PD models, no effects were observed in an in vivo model of immunosuppression monitoring antigen-induced IgG and IgM production. Expression profiling of JAK2 V617F -expressing cells treated with diverse JAK2 inhibitors revealed a shared set of transcriptional changes underlying pharmacological effects of JAK2 inhibition, including many STAT1-regulated genes and STAT1 itself. Collectively, our results highlight BMS-911543 as a functionally selective JAK2 inhibitor and support the therapeutic rationale for its further characterization in patients with MPN or in other disorders characterized by constitutively active JAK2 signaling.

Dysregulated STAT1-SOCS1 control of JAK2 promotes mammary luminal progenitor cell survival and drives ERα+ tumorigenesis

“…Knockdown of JAK2 expression using JAK2-specific shRNAs reduced pSTAT3 levels by 70-80% and pSTAT5A/5B levels by 80-90% (Figures 2c and d and Supplementary Figure S2C). Inhibition of JAK2 activity by a small molecule JAK2-selective inhibitor, BMS-911543, 22 also caused a significant decrease in pSTAT3 and pSTAT5A/5B levels (Figure 2e), demonstrating that JAK2's kinase activity is required to activate both STAT3 and STAT5A/5B. Together, these results show that PrlR initiates the signaling cascade required for the subsequent activation of JAK2 that phosphorylates STAT3 and STAT5A/5B in STAT1 À / À mammary tumor cells.…”

“…Concentration of the inhibitor in mouse serum was consistent with levels shown to fully suppress the constitutively active JAK2 pathway in vivo. 22 To determine whether JAK2 activation was required to drive tumor development in STAT1 À / À mice, tumor-free STAT1 À / À mice approximately 8 months of age were administered BMS-911543 at 10 mg/kg or vehicle PEG490/citrate buffer (80 : 20) daily by oral gavage. Mice were scored as tumor bearing when masses reached 5 Â 5 mm 2 in size and continued to progress.…”

“…Characterization of the small molecule JAK2 inhibitor BMS-911543 was previously described. 22 To determine whether JAK2 activation was required to maintain tumor growth, STAT1 À / À mice bearing primary mammary tumors around 5 mm in diameter were treated with BMS-911543 at 10 mg/kg in PEG490/citrate buffer (80 : 20) once daily by oral gavage. Tumors were measured at two perpendicular diameters every 3-4 days and the average diameters were used for analyses.…”

Discovery of a Highly Selective JAK2 Inhibitor, BMS-911543, for the Treatment of Myeloproliferative Neoplasms

“…The excellent biochemical selectivity versus JAK1/3 translated to good cellular and functional selectivity in an IL-2 mediated Tcell proliferation assay (IC 50 990 nM). 12 Also, cell lines that rely on other JAK family members, including CTLL2 and parental BaF3 cells stimulated with IL-3, showed weak antiproliferative activity for BMS-911543 (IC 50 2.9 and 3.5 μM, respectively) ( Figure 5). 12 BMS-911543 suppressed the pSTAT5 levels (mediated by wild type JAK2) relative to vehicle control when stimulated with thrombopoetin (TPO) in a mouse pharmacodynamic model.…”

“…Earlier we have reported biological characterization of BMS-911543. 12 In vitro biotransformation studies with compound 1 using human liver microsomes revealed the formation of a thiourea metabolite in significant amounts (15%). This metabolic process presumably involves cytochrome P450-mediated oxidation of the thiazole ring to an epoxide and subsequent opening to form a diol intermediate.…”