DDRE-25. WSD0628: A BRAIN PENETRABLE ATM INHIBITOR AS A RADIOSENSITIZER FOR THE TREATMENT OF GBM AND METASTATIC CNS TUMOR

Abstract

Abstract ATM (ataxia telangiectasia mutated) kinase, activated by DNA double-strand breaks, promotes DNA repair as well as activates DNA damage checkpoint and plays a key role for resistance to radiotherapy and chemotherapy. ATM function loss confers hypersensitivity to ionizing radiation evidenced by ataxia-telangiectasia (A-T) cells. Thus, pharmacological inhibition of ATM kinase is expected to suppress DSB DNA repair, block checkpoint controls and enhance the therapeutic effect of radiotherapy and other DNA double-strand breaks-inducing chemotherapy. Herein, we report a discovery of a potent, selective, orally bioavailable, and brain penetrable ATM inhibitor WSD0628, as a radiosensitizer for GBM and metastatic CNS tumors with IC50 against ATM < 1nM with high selectivity ( >400 folds) for ATR and DNA-PK. WSD0628 is highly selective over other kinases. In-vitro MDCKII transfected cells and Caco-2 assays have shown that WSD0628 is highly permeable and not a substrate of P-gp or BCRP, two main efflux transporters expressed on human BBB. Preclinical CNS PK studies in rat and mouse confirmed good brain penetration of WSD0628 with Kp,uu,brain and Kp,uu,csf > 0.3. Significant prolongation of overall survival for mice bearing GBM PDX intracranial model was achieved by treatment with WSD0628 (5mpk, QD) combo with radiation. Moreover, WSD0628 shows low PK variation liability without aldehyde oxidase (AO) metabolism, low hERG liability ( >30 uM), and good safety window based on DRF studies. Taken together, our data provide a good rationale for WSD0628 to be developed toward clinic combo with radiation for the treatment of patients with GBM and cancers with CNS metastasis.