In vitro pharmacological characterization of the potent, lung selective pan-JAK inhibitor TD-8236

Clinical studies with biologics have demonstrated the importance of cytokines in the pathobiology of asthma. However, redundancy and heterogeneity in the asthma cytokine networks may limit the efficacy of single cytokine-targeting biologics. Thus, we set out to discover an inhaled small molecule inhibitor of JAK enzymes, which are critical for the signaling of multiple cytokines. TD-8236 demonstrated pan-JAK inhibitory activity (pKi values 9.8-10.8 at the four JAK kinases) and inhibited IL-13-induced STAT6 phosphorylation (pIC50=8.3) and IL-13 and TNFα-induced CCL26 release (pIC50=8.2) in the bronchial epithelial cell line BEAS-2B. In human primary immune and bronchial epithelial cells, STAT-phosphorylation was potently inhibited downstream of IL-13 (JAK1/2), IL-6 (JAK1/2), IL-4 (JAK1/3), IFNγ (JAK1/2) and IL-12 (JAK2/Tyk2) (pIC50 range 6.6-8.1). TD-8236 also inhibited mediator release downstream of TSLP (CCL17; pIC50=7.1) or IL-2 plus αCD3 (IFNγ; pIC50=7.3). In assays that integrate key features of asthma pathobiology, TD-8236 inhibited IL-5-induced eosinophil survival at IL-5 concentrations relevant to levels observed in eosinophilic asthma (pIC50=6.5) whereas the steroid fluticasone propionate (FP) had no effect (pIC50>5). In 3D bronchial epithelial cell cultures derived from asthma patients, spontaneous periostin and IL-6 release was inhibited by TD-8236 to a greater extent than by FP (% max inh. 92±5 vs. 60±26). Collectively, these data show that TD-8236 is a potent pan-JAK inhibitor that blocks multiple asthma-relevant cytokine pathways in vitro. This profile supports further development of TD-8236 as a novel inhaled non-steroidal therapy to address the needs of asthma patients.