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EPCT-22 SAFETY AND EFFICACY OF INTRAVENTRICULAR IMMUNOVIROTHERAPY WITH ONCOLYTIC HSV-1 G207 FOR TREATMENT OF LEPTOMENINGEAL DISEASE

ABSTRACT: Abstract Leptomeningeal metastatic disease (LMD) occurs in 30–50% of newly diagnosed and recurrent pediatric malignant cerebellar tumors and 20–45% of malignant supratentorial tumors. Radiation and chemotherapy often cause substantial long-term neurotoxicity and outcomes remain poor for patients with LMD. At recurrence, LMD is generally minimally responsive to conventional therapies. Immunovirotherapy with engineered oncolytic HSV-1 G207 has emerged as a promising treatment for children with high-grade brain tumors. G207 infects and kills tumor cells while sparing normal cells and stimulates a robust anti-tumor immune response. Intratumoral G207 inoculation demonstrated safety and preliminary efficacy in a pediatric Phase 1 trial in recurrent/progressive high-grade glioma (NCT02457845), and a Phase 2 trial (NCT04482933) is forthcoming. Additionally, a Phase 1 trial of intratumoral G207 in recurrent/progressive malignant pediatric cerebellar tumors is ongoing (NCT03911388). While intratumoral inoculation delivers G207 directly to a primary tumor, it requires neurosurgical procedures thereby limiting repeat doses. Thus, we sought to establish the safety and efficacy of intraventricular G207. Utilizing an immunocompetent, HSV-sensitive murine strain, we determined that a standard 1x107 plaque-forming units (PFU) dose of G207 resulted in damage to the ependymal lining. However, interferon induction with an intraventricular low-dose (1x104 PFU) of G207 or polyinosinic-polycytidylic acid (poly I:C), a toll-like receptor 3 agonist, three days prior to standard treatment dose protected the ependymal lining. This approach enabled safe delivery of multiple subsequent doses. Importantly, with these protective measures, G207 significantly prolonged survival in pediatric patient-derived xenograft models and an immunocompetent murine LMD model of group 3 medulloblastoma, the most aggressive and fatal subtype. Collectively, these data indicate that toxicity from intraventricular G207 can be safely mitigated prior to a therapeutic dose, and that intraventricular G207 effectively targets group 3 medulloblastoma including LMD. These findings provide support for clinical translation of intraventricular G207.

SUBMITTER: Kang K

PROVIDER: S-EPMC8168116 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundOutcomes in children and adolescents with recurrent or progressive high-grade glioma are poor, with a historical median overall survival of 5.6 months. Pediatric high-grade gliomas are largely immunologically silent or "cold," with few tumor-infiltrating lymphocytes. Preclinically, pediatric brain tumors are highly sensitive to oncolytic virotherapy with genetically engineered herpes simplex virus type 1 (HSV-1) G207, which lacks genes essential for replication in normal brain tissue.MethodsWe conducted a phase 1 trial of G207, which used a 3+3 design with four dose cohorts of children and adolescents with biopsy-confirmed recurrent or progressive supratentorial brain tumors. Patients underwent stereotactic placement of up to four intratumoral catheters. The following day, they received G207 (107 or 108 plaque-forming units) by controlled-rate infusion over a period of 6 hours. Cohorts 3 and 4 received radiation (5 Gy) to the gross tumor volume within 24 hours after G207 administration. Viral shedding from saliva, conjunctiva, and blood was assessed by culture and polymerase-chain-reaction assay. Matched pre- and post-treatment tissue samples were examined for tumor-infiltrating lymphocytes by immunohistologic analysis.ResultsTwelve patients 7 to 18 years of age with high-grade glioma received G207. No dose-limiting toxic effects or serious adverse events were attributed to G207 by the investigators. Twenty grade 1 adverse events were possibly related to G207. No virus shedding was detected. Radiographic, neuropathological, or clinical responses were seen in 11 patients. The median overall survival was 12.2 months (95% confidence interval, 8.0 to 16.4); as of June 5, 2020, a total of 4 of 11 patients were still alive 18 months after G207 treatment. G207 markedly increased the number of tumor-infiltrating lymphocytes.ConclusionsIntratumoral G207 alone and with radiation had an acceptable adverse-event profile with evidence of responses in patients with recurrent or progressive pediatric high-grade glioma. G207 converted immunologically "cold" tumors to "hot." (Supported by the Food and Drug Administration and others; ClinicalTrials.gov number, NCT02457845.).

Project description:Brain tumors represent the most common pediatric solid neoplasms and leading cause of childhood cancer-related morbidity and mortality. Although most adult brain tumors are supratentorial and arise in the cerebrum, the majority of pediatric brain tumors are infratentorial and arise in the posterior fossa, specifically the cerebellum. Outcomes from malignant cerebellar tumors are unacceptable despite aggressive treatments (surgery, radiation, and/or chemotherapy) that are harmful to the developing brain. Novel treatments/approaches such as oncolytic virotherapy are urgently needed. Preclinical and prior clinical studies suggest that genetically engineered oncolytic herpes simplex virus (HSV-1) G207 can safely target cerebellar malignancies and has potential to induce an antitumor immune response at local and distant sites of disease, including spinal metastases and leptomeningeal disease. Herein, we outline the rationale, design, and significance of a first-in-human immunotherapy Phase 1 clinical trial targeting recurrent cerebellar malignancies with HSV G207 combined with a single low-dose of radiation (5 Gy), designed to enhance virus replication and innate and adaptive immune responses. We discuss the unique challenges of inoculating virus through intratumoral catheters into cerebellar tumors. The trial utilizes a single arm open-label traditional 3 + 3 design with four dose cohorts. The primary objective is to assess safety and tolerability of G207 with radiation in recurrent/progressive malignant pediatric cerebellar tumors. After biopsy to prove recurrence/progression, one to four intratumoral catheters will be placed followed by a controlled-rate infusion of G207 for 6 h followed by the removal of catheters at the bedside. Radiation will be given within 24 h of virus inoculation. Patients will be monitored closely for toxicity and virus shedding. Efficacy will be assessed by measuring radiographic response, performance score, progression-free and overall survival, and quality of life. The data obtained will be invaluable in our efforts to produce more effective and less toxic therapies for children with high-grade brain tumors.

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EPCT-22 SAFETY AND EFFICACY OF INTRAVENTRICULAR IMMUNOVIROTHERAPY WITH ONCOLYTIC HSV-1 G207 FOR TREATMENT OF LEPTOMENINGEAL DISEASE

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