Novel, highly potent and selective JAK3 inhibitor disrupting IL-4/IL-13 signaling in asthma therapy

Introduction: Role of interleukins 4 and 13 was confirmed in allergic asthma pathogenesis driven by Th 2 cells. Both cytokines signal through common γ-chain receptors, associated with JAK/STAT pathway. Janus kinases (JAKs) are responsible for immune signaling in response to ligands bound to IL-4Rα and IL-13Rα receptors. IL-4 involves JAK1/3, and IL-13 JAK1/2 mediated activation of STAT6 transcription factor and related eotaxin-3 (CCL26) expression. Therefore, development of JAK inhibitors seems an attractive strategy for the treatment of asthma. Results: CPL-409-057 is a JAK3 inhibitor with picomolar activity (IC 50 =19,75pM) measured in recombinant kinase activity assay. CPL-409-057 exhibits good selectivity among other JAK family kinases: JAK1/JAK2/TYK2 with IC 50 of 2,34nM, 0,93nM and 44,97nM, respectively. CPL-409-057 is also selective in a panel of diverse kinases. Cell-based proliferation assay shows that CPL-409-057 inhibits JAK2-dependent SET-2 cells with IC 50 =1,6μM and does not affect growth of JAK-independent HEK293 cells when tested at this concentration. Western Blot analysis revealed great abrogation of pSTAT3 and 5 in SET-2 cells as well as pSTAT1 and 6 in primary bronchial tracheal epithelial cells (PBTEC) after 450nM of CPL-409-057. PBTEC treatment with 150nM of CPL-409-057 reduced CCL26 secretion after IL-4/IL-13 stimulation by 60/80 percent, respectively, when measured in ELISA assay. Conclusion: Our results indicate that CPL-409-057 strongly inhibits JAK/STAT signaling and by disrupting IL-4/IL-13 signaling remarkably lowers secretion of eosinophil-attracting CCL26. Thus, CPL-409-057 emerges as an attractive candidate for development in Th 2 -driven eosinophilic asthma therapy.