NS-229, a novel Janus kinase 1 inhibitor, ameliorates eosinophilic vasculitis in an ovalbumin-induced mouse model by modulating multiple cytokine signaling pathways

Methyl (1-{[6-{[(1S)-1-cyclopropylethyl]amino}-2-(pyrazolo[5,1-b][1,3]thiazol-7-yl)pyrimidin-4-yl]carbonyl}piperidin-4-yl)carbamate mono(4-methylbenzenesulfonate) monohydrate (NS-229) is a novel Janus kinase 1 inhibitor currently being evaluated in a phase 2 global study (NCT06046222) for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA). We investigated the nonclinical efficacy of NS-229 to support its therapeutic use in treating EGPA. Its effects were investigated in human peripheral blood eosinophils, human peripheral blood mononuclear cells, and a mouse model of eosinophilic vasculitis induced by ovalbumin. In human peripheral blood eosinophils, NS-229 and an anti-interleukin (IL)-5 antibody, but not prednisolone, significantly decreased the expression of CD69 induced by IL-5. In human peripheral blood mononuclear cells, NS-229 and prednisolone, but not the anti-IL-5 antibody, significantly decreased the production of cytokines such as interferon gamma, IL-5, and IL-13, induced by anti-CD3/CD28 antibody. NS-229 inhibited the development of vascular lesions, decreased eosinophil counts in the blood and bronchoalveolar lavage fluid, and lowered bronchoalveolar lavage fluid lymphocyte counts in the ovalbumin-induced eosinophilic vasculitis mouse model. The effects of NS-229 in the mouse model were comparable to those of prednisolone and tofacitinib, a pan-Janus kinase inhibitor. Regarding safety, NS-229 did not influence the platelet or red blood cell counts, which were significantly elevated with tofacitinib and prednisolone, respectively. NS-229 did not affect body weight, which was significantly increased with tofacitinib and significantly decreased with prednisolone. Collectively, the nonclinical investigation of NS-229 showed a suppression of multiple cytokine signals and inhibition of vascular lesion formation without impacting the relevant side-effect parameters, suggesting its potential as an additional treatment option for EGPA. SIGNIFICANCE STATEMENT: NS-229 inhibited the formation of vascular lesions in a mouse model of ovalbumin-induced eosinophilic vasculitis without affecting certain side-effect parameters. The underlying mechanism of action is suggested to be the selective inhibition of multiple cytokine signals via JAK1.