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Phase 1b Clinical Trial of OKN-007 in Recurrent Malignant Glioma

Background: Despite therapeutic advances, the median overall survival for patients with recurrent, high-grade gliomas remains poor. Thus, there is an urgent need for efficacious new therapies. The nitrone compound, OKN-007 (disodium 4-[(tert-butyl-imino) methyl] benzene-1,3-disulfonate N-oxide) is a promising novel anti-cancer agent. In orthotopic glioblastoma xenografts, OKN-007 reduces cell proliferation and angiogenesis, and increases apoptosis. Here we report on the safety, efficacy, and pharmacokinetics (PK) of OKN-007 in adults with recurrent glioma.

Methods: NCT01672463 is a phase 1b trial of OKN-007 in adults with recurrent gliomas previously treated with standard therapy. Patients with recurrence, adequate performance status and organ function, receiving clinically appropriate doses of steroids, with a life expectancy greater than 8 weeks were eligible. OKN-007 was administered by IV. The study comprised a 3+3 dose escalation design followed by an expansion cohort at the maximum tolerated dose (MTD). The dose escalation drug levels were 20 (n = 3), 40 (n = 3), and 60 mg/kg (n = 3), treating on a schedule of thrice weekly for 4 weeks, then twice weekly for 4 weeks, then once weekly until progression. Drug PK was determined in the dose escalation cohorts. The expansion cohort was treated with 60 mg/kg thrice weekly for 12 weeks, then twice weekly for 12 weeks, then once weekly until recurrence (n = 6). Kaplan-Meier analysis was used to determine progression-free (PFS) and overall survival (OS).

Results: Median age was 51 years (range, 25-62). No dose-limiting toxicities were observed and 60 mg/kg was chosen for the expansion dose. Of 123 adverse events (AE), 34 were deemed probably (1.6%) or possibly (26%) treatment-emergent (TEAE). The most commonly-occurring TEAE were fatigue (4.1%) and headache (3.3%). No drug-attributable grade 4 or 5 AE were observed. Grade 3 TEAE included headache, urinary tract infection, and increased prothrombin time (0.8% each). Only two grade 1 AE, hypokalemia and dizziness, were considered probably attributable to OKN-007. In patients receiving 60 mg OKN-007/kg, median PFS was 1.4 months and OS was 21 months (log rank p = 0.08 for comparison across doses). Systemic PK exposure was dose proportional. The average half-life of OKN-007 is 2.8 hours.

Conclusions: OKN-007 appears safe for patients with recurrent glioma. The MTD was not reached. Our data suggest that, compared to standard therapy, OKN-007 may prolong OS in recurrent glioma. Based on new data, a trial of OKN-007 plus temozolomide is underway in patients with newly diagnosed glioblastoma (NCT03587038).

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