ACTR-40. A PHASE 1, MULTICENTER, OPEN-LABEL STUDY OF MARIZOMIB (MRZ) WITH TEMOZOLOMIDE (TMZ) AND RADIOTHERAPY (RT) IN NEWLY DIAGNOSED WHO GRADE IV MALIGNANT GLIOMA (GLIOBLASTOMA, ndGBM): FULL ENROLLMENT RESULTS
Abstract Proteasome inhibition sensitizes glioma cells to TMZ and RT, providing a novel therapeutic strategy for ndGBM. MRZ, an irreversible, brain-penetrant, pan-proteasome inhibitor with anti-glioma activity was combined with standard-of-care (SOC) concomitant TMZ/RT followed by adjuvant TMZ in ndGBM (NCT02903069), to determine the recommended dose (RD). Patients were enrolled in separate concomitant (TMZ/RT+MRZ, N=15) and adjuvant (TMZ+MRZ, N=18) cohorts in dose-escalation (3 + 3 design), followed by dose-expansion (N=20) at RD (0.8 mg/m2) in concomitant followed by adjuvant treatment. MRZ infused IV (10 min) at increasing dose levels (0.55, 0.7, 0.8, and 1.0 mg/m2): Concomitant days 1, 8, 15, 29, 36; Adjuvant days 1, 8, 15 (28-day cycle). RESULTS (as of 02May2018): Mean age 55 years, 68% male. Most common treatment-emergent adverse events (TEAEs, 20% patients, all grades): fatigue, nausea, vomiting, hallucination, ataxia, headache. Dose-limiting toxicities (DLTs): 1 (fatigue) at 0.7 mg/m2 adjuvant cohort, 3 (ataxia/diarrhea; ataxia/confusion; myocardial infarction) in concomitant and 2 (delirium/ataxia; ataxia/fatigue) in adjuvant cohorts at 1.0 mg/m2. Grade 3 TEAEs in 11 of 12 patients at 1.0 mg/m2 including one Grade 4 and one Grade 5 TEAE; at 0.8 mg/m2 MRZ, Grade 3 TEAEs in 9 of 21 patients. MRZ demonstrated a steep dose-response with TEAEs/DLTs predominately CNS AEs (ataxia, hallucinations) which were dose-related, short-lasting, reversible and ameliorated by early dose reductions, allowing patients to remain on treatment. Currently 8 dose-escalation patients remain active in Cycle 10–23. Median OS for dose-expansion not yet estimated; 7 patients remain active, 1 death, median follow-up 4.1 months. MRZ at the RD with adjuvant TMZ+Tumor Treating Fields (Optune) is currently enrolling. An international Phase 3 trial (EORTC #1709-BTG, NCT03345095) has been launched in 2018 to assess the overall survival benefit of MRZ added to SOC in ndGBM.