CTNI-73. ASSESSMENT OF MOLECULAR ALTERATIONS IN NEWLY DIAGNOSED GBM MGMT-UNMETHYLATED PATIENTS TREATED WITH VAL-083

Abstract Glioblastoma (GBM) commonly features molecular alterations in the TERT, EGFR, PTEN, and TP53 genes, which contributes to uncontrolled cell growth, evasion of apoptosis, and enhanced tumor cell survival. VAL-083 is a bi-functional DNA-targeting agent which rapidly induces inter-strand DNA cross-links at N7 and O6-guanine inducing double-strand breaks causing cell death independently of MGMT DNA repair and DNA mismatch repair deficiency. VAL-083 was evaluated in an open-label, biomarker-driven, phase 2 trial in MGMT-unmethylated, bevacizumab-naïve GBM patients. The molecular profile of tumors from a newly diagnosed GBM patient subgroup who received VAL-083 alone after chemo-radiation with concurrent TMZ, was determined in order to correlate with clinical outcomes. Thirty-four (34/36, 94.4%) patients who received 30 mg/m2 VAL-083 (days 1-3 of 21-day cycle) had available next-generation sequencing data on their primary tissue. Patient median age was 54.8 years (5-95pth: 29.8-66.0), median KPS was 90 (5-95pth: 80-100) and 58.8% were males. The median number of cycles of VAL-083 was 7.5 (5-95pth: 1-12). There were 5 dose reductions due to toxicity. The median time to progression (PFS) and overall survival (OS) were 9.2 mo (95%CI: 7.6-10.2) and 16.5 mo (95%CI: 13.3-19.0), respectively. The mean number of molecular alterations was 3.9 (5-95pth 1-8). Six (17.6%) patients had gene fusions. The most common molecular alterations were TERT promoter (91.2%), EGFR amplification (amp) (52.9%), PTEN (50.0%), EGFR (20.6%), and TP53 (20.6%). Additional alterations (in ≥2 patients; 6%) included EGFR-EGFR (EGFRvIII), BRCA2, CDKN2A/B, CDK4/6 amp, MDM2/4 amp, NF1, NOTCH1, PIK3R1 and RB1. While TP53 mutations showed a trend as predictors for time to progression (P 0.027), this was not observed with OS. None of the molecular alterations were predictors of number of treatment cycles or dose reductions. No specific molecular alterations were identified that predicted either improved or poorer patient outcome, during treatment with VAL-083. Clinicaltrials.gov identifier: NCT02717962.