CTNI-55. A PHASE 0/1B STUDY OF AZD1390 PLUS RADIOTHERAPY IN NEWLY DIAGNOSED, MGMT-UNMETHYLATED AND RECURRENT GLIOBLASTOMA PATIENTS

Abstract BACKGROUND ATM inhibition is hypothesized to potentiate the effects of radiation by preventing acute phase DNA damage repair. This Phase 0/1b study evaluated the pharmacokinetics (PK) and pharmacodynamics (PD) of AZD1390, a first-in-class ATM inhibitor, in combination with radiation in newly-diagnosed and recurrent GBM patients (NCT05182905). METHODS All patients received 3 days of AZD1390 prior to planned resection at 2-4, 4-6 or 23-25 hrs following the final dose (120/300mg for nGBM and 400mg for rGBM). Tumor tissue, cerebrospinal fluid (CSF), and plasma were collected. Total and unbound drug concentrations were measured using validated LC-MS/MS methods. ATM inhibition was assessed via ex vivo tissue radiation, quantifying pRAD50 levels compared to non-radiated control. A PK ‘trigger’ determined eligibility for Phase 1b and patients exceeding the PK threshold (2 nM unbound drug levels in Gd-non-enhancing tumor region) were eligible for therapeutic dosing of AZD1390 plus radiotherapy. RESULTS Thirty nGBM patients and twenty-nine rGBM patients were enrolled. Forty-eight out of the forty-nine evaluable patients exceeded the PK threshold and qualified for therapeutic dosing. The mean unbound concentrations of AZD1390 in Gd-nonenhancing tumors of both nGBM and rGBM patients were significantly above the threshold at all dose levels and time intervals. Following 5Gy ex vivo radiation of surgical specimens, pRAD50 expression was significantly suppressed in AZD1390-treated patients compared to untreated controls. To date, 6 MGMT-unmethylated nGBM patients and 15 rGBM patients were enrolled in the Phase 1b component of the study, with median clinical follow-up of 7.0 months. Median PFS and OS have not been reached in the nGBM population. Median OS for rGBM patients was 15.4 months. CONCLUSION AZD1390 is well-tolerated in both newly-diagnosed and recurrent GBM patients, achieving pharmacologically relevant concentrations in Gd-nonenhancing tumor tissue, and suppressing radiation-induced increase in pRAD50 levels. These data are the first to demonstrate AZD1390-mediated PD and PK responses in nGBM and rGBM patients. Clinical outcomes data are maturing and will be reported.