A phase 2 trial of verubulin for recurrent glioblastoma: a prospective study by the brain tumor investigational consortium (BTIC)

Treatment options are limited for recurrent glioblastoma (GBM). Verubulin is a microtubule destabilizer and vascular disrupting agent that achieve high brain concentration relative to plasma in animals. Adults with recurrent GBM who failed prior standard therapy were eligible. The primary endpoint was 1-month progression-free survival (PFS-1) for bevacizumab refractory (Group 2) and 6-month progression-free survival (PFS-6) for bevacizumab naïve patients (Group 1). Verubulin was administered at 3.3 mg/m² as a 2-h intravenous infusion once weekly for 3 consecutive weeks in a 4-week cycle. The planned sample size was 34 subjects per cohort. 56 patients (37 men, 19 women) were enrolled, 31 in Group 1 and 25 in Group 2. The PFS-6 for Group 1 was 14 % and the PFS-1 for Group 2 was 20 %. Median survival from onset of treatment was 9.5 months in Group 1 and 3.4 months in Group 2. Best overall response was partial response (n = 3; 10 % in Group 1; n = 1; 4.2 % in Group 2) and stable disease (n = 7; 23 % in Group 1; n = 5; 21 % in Group 2). In Group 1, 38.7 % of patients experienced a serious adverse event; however only 3.2 % were potentially attributable to study drug. In Group 2, 44 % of patients experienced a serious adverse event although none were attributable to study drug. Accrual was terminated early for futility. Single agent verubulin, in this dose and schedule, is well tolerated, associated with moderate but tolerable toxicity but has limited activity in either bevacizumab naïve or refractory recurrent GBM.