Discovery of Orally Bioavailable Phthalazinone Analogues as an ENPP1 Inhibitor for STING-Mediated Cancer Immunotherapy
Y. K. Cho, Miso Kang, Su Hyun Ji, Hee Jin Jeong, Jae Eun Jung, Do Hee Oh, Sunyoung Park, Yong‐Yea Park, Junghwan Choi, Junghwan Choi, Sung Joon Kim, Nam‐Jung Kim, Duck‐Hyung Lee, Chan Sun Park, Seo‐Jung Han, Sanghee Lee, Junwon Choi, Junwon Choi
Abstract
A lack of the T cell-inflamed tumor microenvironment limits the efficacy of immune checkpoint inhibitors (ICIs). Activation of stimulator of interferon genes (STING)-mediated innate immunity has emerged as a novel therapeutic approach in cancer therapy. 2′,3′-Cyclic GMP–AMP (cGAMP) is a natural STING agonist; however, cGAMP is subjected to endogenous degradation by ecto-nucleotide pyrophosphatase phosphodiesterase 1 (ENPP1). To improve the ICI response rate, we developed 29f, a novel ENPP1 inhibitor with phthalazin-1(2 H )-one as the core scaffold. 29f inhibited the cGAMP hydrolysis by ENPP1 in vitro (IC 50 = 68 nM) and enhanced the STING-mediated type I interferon response in both immune and tumor cells. 29f demonstrated excellent metabolic stability and bioavailability ( F = 65%). Orally administered 29f promoted tumor growth inhibition in a CT26 syngeneic model and increased the anti-PD-L1 response. Furthermore, 29f -induced immunological memory prevented the tumor relapse against tumor rechallenge, suggesting the promising therapeutic potential of 29f .