Abstract LB127: VAL-083 in patients with recurrent glioblastoma treated under expanded access program

Current standard-of-care for glioblastoma (GBM) includes surgery followed by concurrent therapy with radiation and temozolomide (TMZ) and adjuvant TMZ. Almost all GBM patients experience recurrent/progressive disease despite upfront standard of care treatment, with a median overall survival of 3-9 mo. after recurrence. There are limited treatment options available upon progression of disease which may include potential participation in clinical trials. However, patients may not meet the strictly defined entry criteria to participate in these clinical trials. VAL-083 is a first-in-class bifunctional alkylating agent that acts independent of O6-methylguanine-DNA-methyltransferase (MGMT) methylation status. Under an Expanded Access (EA) program, we have treated 24 patients with recurrent GBM, who were not eligible to participate in clinical trials with VAL-083. Four (4/24; 17%) patients had leptomeningeal disease (LMD) at time of enrolment. While safety data was assessed for all patients, those without LMD (20 patients) were evaluated for efficacy. All patients evaluated for efficacy received chemoradiation with TMZ, and the mean number of adjuvant TMZ cycles was 5 (± 6.2). The median time from last progression to start of VAL-083 was 0.65 mo. (95%CI: 0.32-1.55) and median KPS was 80 (25-75P: 70-90). Eight (8/20; 40%) patients had 2 or more prior recurrences, 9/20 (45%) patients had multifocal disease, and 5/20 (25%) had prior lomustine. Eighteen (18/20; 90%) patients had unmethylated promoter status for MGMT and 18/20 (90%) were IDH wild type. All patients had at least 1 mutation, with 11/20 (55%) having 5 or more mutations, and one patient had hypermutator phenotype with MSH6 mutation. The most common mutations were, TERT 11/20 (55%), PTEN 9/20 (45%), and TP53 6/20 (30%). All patients started treatment with VAL-083 at 30 mg/m2 administered on 3 consecutive days every 21 days. Seven patients received bevacizumab concurrently with VAL-083. VAL-083 was well tolerated and the main adverse events were consistent with prior experience, i.e., thrombocytopenia and neutropenia. Eight (8/24; 33%) patients had a dose reduction, 7 of which were due to thrombocytopenia, and 1 due to neutropenia. Five patients with thrombocytopenia had prior lomustine. As of cut-off date (05 Jan, 2023), median progression free survival (mPFS) and median overall survival (mOS) from last disease progression was 5.9 mo (95%CI: 3.9-7.9) and 9.4 mo (95%CI: 3.0-14.3), respectively. In patients