Treovir, Inc. has announced the commencement of a Phase 2 clinical trial investigating G207, an oncolytic herpes simplex virus (HSV) immunotherapy, for pediatric patients with recurrent high-grade glioma. This single-arm study aims to evaluate the efficacy and safety of G207 in 30 children with this aggressive form of brain tumor, where no approved therapies currently exist. The trial is being conducted in collaboration with the Pediatric Brain Tumor Consortium (PBTC), supported by the National Cancer Institute (NCI), across multiple cancer centers including Memorial Sloan Kettering Cancer Center and The University of Texas MD Anderson Cancer Center.
G207: A Novel Oncolytic Immunotherapy
G207 is a genetically engineered oncolytic HSV designed to selectively infect and kill malignant brain tumor cells. This process releases tumor cell debris, which in turn elicits a potent immune response, potentially leading to the further elimination of tumor cells. The FDA has granted Fast-Track status to G207, and it holds orphan drug designations for gliomas, ependymomas, medulloblastomas, and primitive neuroectodermal tumors in the US and for gliomas in the EMA.
Phase 1 Trial Results Show Promise
Data from a Phase 1 dose-escalation study, published in the New England Journal of Medicine in 2021, showed encouraging results. Involving 12 pediatric patients with progressive high-grade glioma, the study found no dose-limiting toxic effects or serious adverse events attributed to G207. Notably, the median overall survival for patients in the trial was 12.2 months (95% confidence interval, 8.0 to 16.4), more than double the typical survival rate for children with recurrent high-grade glioma. Five of the twelve patients survived longer than 18 months. Furthermore, G207 increased the number of tumor-infiltrating lymphocytes, suggesting activation of the patient's immune system.
Unmet Need in Pediatric Brain Tumors
Brain tumors are the most common solid tumors in children, with glioblastoma exhibiting a particularly low survival rate of approximately 10% five years post-diagnosis. Malignant high-grade gliomas account for 8-10% of pediatric brain tumors, and survival rates have remained stagnant for three decades. The median life expectancy for recurrent high-grade glioma is a mere 5.6 months, underscoring the urgent need for effective therapies.
Future Directions
In addition to the Phase 2 study, G207 is also being assessed for safety in a Phase 1 clinical trial in children with recurrent or progressive malignant cerebellar gliomas or medulloblastomas at MD Anderson Cancer Center. Treovir is also planning a Phase 1/2 clinical study in newly diagnosed brain tumor patients, anticipated to begin in 2026. According to Michael Christini, CEO of Treovir, the company expects the Phase 2 data to support a BLA filing for market approval of G207, offering a potential treatment option for this underserved therapeutic area.
