A phase I study of SDX-102 for the treatment of patients with MTAP-deficient recurrent malignant gliomas

Abstract

2063 Background: De novo purine biosynthesis entails two metabolic pathways of which one pathway is frequently impaired in cancer due to gene deletion of the rate limiting enzyme, methythioadenosine phosphorylase (MTAP). In MTAP-deficient cancers, SDX-102 inhibits purine biosynthesis by blocking the remaining synthetic pathway. This study was to determine the maximum tolerated dose (MTD), toxicity and pharmacokinetic activity of SDX-102 in the treatment of recurrent MTAP-deficient malignant gliomas. Methods: Eligible patients had recurrent supratentorial MTAP-deficient malignant gliomas treated previously with surgery, radiation and = 2 regimens of chemotherapy. Dose escalation was conducted separately for patients taking enzyme inducing anti-seizure drugs (EIASD+) and for those not (EIASD-). The starting dose in both groups was 80 mg/m2/day continuous infusion for 5 days every 3 weeks, cycle length was 3 weeks. Dose escalation was in a stepwise fashion in cohorts of three patients, up to a maximum dose of 125 mg/m2/day. Results: 118 patients were screened of which 39 (33%) had MTAP-deficient tumors. 21 patients (14 males/7 females) were enrolled between 9/17/04 and 3/17/06. Median age was 50 years (23–76); median KPS was 90 (60–100); 16 patients (76%) had GBM. Two dose levels of SDX-102 were tested in the EIASD+ group: 80 mg/m2/day (n=4) and 100 mg/m2/day (n=3), 3/3 dose limiting toxicity (DLT) were noted with grade 3 mucositis at 100 mg/m2/day , so in the EIASD+ group the MTD was 80 mg/m2/day. Three dose levels were tested in the EIASD- group: 80 mg/m2/day (n=4), 100 mg/m2/day (n=7), 1/3 patients had DLT (Grade 4 mucositis) at 100 mg/m2/day and the cohort was expanded for additional 3 patients without DLT noted; and 125 mg/m2/day (n=3) amongst whom no DLT was observed. No MTD was determined in the EIASD- group because the MTAP assay became unavailable through the sponsor. There were a range of 1–14 cycles administered in this patient population. Conclusions: SDX-102 infusion is safe and feasible in patients with recurrent MTAP-deficient malignant gliomas. The MTD in EIASD+ patients is 80 mg/m2/day. The EIASD-group MTD has not been determined however the highest dose tested is 125 mg/m2/day. No significant financial relationships to disclose.