Janus kinases are a family of four enzymes; JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2) that are critical in cytokine signaling. Overall, up to 70% of human tumors are linked to persistent elevated STAT3 activity which can be associated with poorer prognosis in many of these settings. JAK1 is believed to be a primary driver of STAT3 phosphorylation and signaling. JAK2, however, is essential for signal transduction downstream of erythropoietin, thrombopoietin and other related receptors that control erythrocyte and megakaryocyte expansion. Therefore a JAK1 selective inhibitor may enable higher target coverage of the JAK1-STAT3 signaling by sparing toxicities such as thrombocytopenia and anemia, associated with JAK2 inhibition, to maximize the clinical benefit.
We will present our detailed medicinal chemistry optimization using structure-based design from a non-kinome selective screening hit to the candidate drug AZD4205, a highly selective novel JAK1 kinase inhibitor. AZD4205 displayed high levels of JAK1 biochemical and cellular potency with favorable physical properties and excellent preclinical in vivo pharmacokinetics. AZD4205, in a combination with low dose osimertinib, demonstrated a greater antitumor activity in an H1975 (T790M) NSCLC xenograft model. These findings warrant the further clinical investigation of AZD4205 to fully understand its potential as an anti-cancer therapeutic.