Discovery and characterization of LY2784544, a small-molecule tyrosine kinase inhibitor of JAK2V617F

Abstract

Owing to the prevalence of the JAK2V617F mutation in myeloproliferative neoplasms (MPNs), its constitutive activity, and ability to recapitulate the MPN phenotype in mouse models, JAK2V617F kinase is an attractive therapeutic target. We report the discovery and initial characterization of the orally bioavailable imidazopyridazine, LY2784544, a potent, selective and ATP-competitive inhibitor of janus kinase 2 (JAK2) tyrosine kinase. LY2784544 was discovered and characterized using a JAK2-inhibition screening assay in tandem with biochemical and cell-based assays. LY2784544 in vitro selectivity for JAK2 was found to be equal or superior to known JAK2 inhibitors. Further studies showed that LY2784544 effectively inhibited JAK2V617F-driven signaling and cell proliferation in Ba/F3 cells (IC50=20 and 55 nM, respectively). In comparison, LY2784544 was much less potent at inhibiting interleukin-3-stimulated wild-type JAK2-mediated signaling and cell proliferation (IC50=1183 and 1309 nM, respectively). In vivo, LY2784544 effectively inhibited STAT5 phosphorylation in Ba/F3-JAK2V617F-GFP (green fluorescent protein) ascitic tumor cells (TED50=12.7 mg/kg) and significantly reduced (P<0.05) Ba/F3-JAK2V617F-GFP tumor burden in the JAK2V617F-induced MPN model (TED50=13.7 mg/kg, twice daily). In contrast, LY2784544 showed no effect on erythroid progenitors, reticulocytes or platelets. These data suggest that LY2784544 has potential for development as a targeted agent against JAK2V617F and may have properties that allow suppression of JAK2V617F-induced MPN pathogenesis while minimizing effects on hematopoietic progenitor cells.

JAK of all trades: JAK2-STAT5 as novel therapeutic targets in BCR-ABL1+ chronic myeloid leukemia

“…74 Clinical studies have only recently become possible with the availability of more specific JAK2 inhibitors (Table 2). [75][76][77][78][79][80][81][82][83][84][85][86] The IC 50 values of TG101209 (a precursor of TG101348 currently in clinical studies for use in the treatment of JAK2V617F 1 MPN) required to induce apoptosis in imatinib-sensitive and -resistant murine and human cell lines are within the low micromolar range, approaching values that may be reached in patients. 74 Moreover, CD34 1 cells derived from CP and BC imatinib-resistant CML patients proved sensitive to TG101209 treatment.…”

Discovery and Characterization of Novel GPR39 Agonists Allosterically Modulated by Zinc

“…3). Currently, LY2784544 is being evaluated in patients with myeloproliferative neoplasm in two phase I trials to investigate dose and schedule (I3X-MC-JHTA, NCT01134120; and I3X-MC-JHTC, NCT01520220) and a phase II study to investigate efficacy (I3X-MC-JHTB, NCT01594723) (Ma et al, 2013). Additionally, GSK2636771 is being tested in a phase I/II trial in patients with phosphatase and tensin homolog (PTEN)-deficient advanced solid tumors (NCT01458067) (Thorpe et al, 2015).…”

“…Indeed, when the potencies for activating GPR39 in the presence of Zn 21 were calculated, we found their EC 50 values Novel Agonists of the GPR39 Zinc Receptor were in the sub-to single-digit nanomolar range in whole-cell assays. By comparison, the potency of LY2784544 in whole-cell assays for inhibition of JAK2 proliferation was 20 nM (Ma et al, 2013), whereas GSK2636771 had a potency of 7-114 nM in whole-cell assays (Qu et al, 2015). These results indicate that, in terms of the cellular context, the activities at GPR39 could predominate.…”

Coexistence of gain-of-function JAK2 germ line mutations with JAK2V617F in polycythemia vera

“…(LY2784544) 14 was similar for both germ line and wt JAK2 variants at different concentrations of LY2784544 after 72 hours of exposure (data not shown).…”