1. Treatment with herpes simplex virus type 1 oncolytic virotherapy was shown not to demonstrate serious adverse events in pediatric patients with high-grade gliomas.
2. The oncolytic virotherapy was shown to increase the number of tumor-infiltrating lymphocytes.
Evidence Rating Level: 2 (Good)
Study Rundown: Pediatric high-grade glioma remains to have a grim prognosis despite the current standard of care consisting of radiotherapy and chemotherapy. High-grade gliomas characteristically have a low mutational burden with few tumor-infiltrating lymphocytes. As such, this study evaluated the safety of an oncolytic herpes simplex virus type 1 (HSV-1) termed G207 on recurrent high-grade glioma. The study determined viral replication was disabled in normal cells but retained in tumor cells. There was no evidence of viral shedding or viremia. Furthermore, no high-grade adverse events were attributable to G207. Finally, available pathological treatments post-treatment revealed increases in tumor-infiltrating lymphocytes. The study was limited by the use of the immunotherapy Response Assessment in Neuro-Oncology criteria to determine the radiographic response in the tumor. Nonetheless, the study’s results were significant, as the trial provided preliminary evidence to suggest that oncolytic viruses have an acceptable adverse-event profile.
In-Depth [prospective cohort]: In this phase 1 safety trial, 12 pediatric patients were enrolled in the study. Patients included in the study were between 3 and 18 years of age with a malignant supratentorial brain tumor of 1.0 cm or larger that has progressed after surgery radiotherapy, or chemotherapy. Patients with tumors requiring cerebellar, brainstem, ventricular inoculation were excluded from the study. The primary outcome was determining the safety profile of G207 and a response assessment based on magnetic resonance imaging. The median overall survival was 12.2 months (95% confidence interval [CI], 8.0 to 16.4 months). All adverse events related to G207 were assessed to be grade 1, and no serious adverse events were assessed by the investigators to be related to G207. There was no distinct pattern of adverse events in this cohort. Stable disease was seen in 7 of 12 patients at 1 month (58%), 4 of 11 patients at 3 months (27%), and 2 of 11 patients at 12 months (18%). In 4 patients who had pathological samples for examination post-treatment, there were increases in CD3+, CD4+, and CD8+ tumor-infiltrating lymphocytes compared to pre-treatment. In general, G207 has a reasonable safety profile in the treatment of pediatric high-grade gliomas.
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