This is a multicenter, open-label study of DB107-RRV (formerly Toca 511) and DB107-FC (formerly Toca FC) when administered following surgical resection in newly diagnosed High Grade Glioma (HGG) patients. The study is designed to evaluate whether treatment with DB107-RRV in combination with DB107-FC when added to standard of care provides clinical benefit to newly diagnosed HGG when compared to historical performance previously determined in well controlled clinical trials published in the peer reviewed literature. This study is going to be conducted in newly diagnosed HGG patients receiving with maximum surgical resection treatment followed by radiation and temozolomide treatment using the established Stupp Protocol for O6-methylguanine-DNA methyl-transferase (MGMT) methylated patients or radiation therapy for MGMT unmethylated patients.

PRIMARY OBJECTIVES:

I. To evaluate the safety and tolerability of DB107-RRV administered intracranially followed by intravenous (IV) DB107-RRV and DB107-FC (Phase I).

II. To determine the median progression-free survival (PFS) (informed by biomarker status, DGM7 and patient subsets to minimally include genomic profile and histology) of newly diagnosed HGG patients treated with DB107-RRV combined with DB107-FC delivered with standard of care following tumor resection (Phase IIa).

SECONDARY OBJECTIVES:

I. To confirm the recommended Phase 2 Dose (RP2D) of DB107-RRV and DB107-FC when administered to newly diagnosed HGG patients (Phase I).

II. To evaluate radiographic response by Immunotherapy response assessment in neuro-oncology (iRANO) (Phase I).

III. To assess best overall response rates (complete response (CR), partial response (PR), stable disease (SD), progressive disease (PD)) and overall response rate (CR and PR) of each arm and subset (Phase IIa).

IV. To assess the duration of response of each arm and subset (Phase IIa). V. To assess the median overall PFS and PFS at month 6 (PFS-6) for each arm and subset (Phase IIa).

VI. To assess the median overall survival of each arm and subset (Phase IIa). VII. To evaluate the safety of DB107-RRV administered intracranially followed by IV DB107-RRV and DB107-FC (Phase IIa).

OUTLINE:

Participants will initially be enrolled in Phase I and treated with DB107-RRV intracranially, at time of surgical resection, and intravenously within 8 hours following surgery. Pathology will be performed locally as per standard practice to confirm participant's HGG diagnosis and Isocitrate dehydrogenase 1 (IDH1) mutation status. Participants in Phase I will then be assigned to one of 2 cohorts: No MGMT methylation (MGMT unmethylated) which will receive DB107-FC and RT following DB107-RRV or Low-High MGMT methylated which will receive DB107-FC, Temozolomide (TMZ) and RT following DB107-RRV. The safety and tolerability will be examined for the Phase I participants and RP2D dose confirmed. New participants will then be enrolled in Phase IIa under the established RP2D determined in Phase I, with the first 2 participants receiving a safety run-in at the RP2D. Once participant safety and tolerability are confirmed, additional participants will be enrolled in the Phase IIa portion of the study. All participants who receive DB107-RRV and DB107-FC will be followed for up to15 years.

Inclusion Criteria:

Each patient must meet all of the following inclusion criteria to be eligible for study entry:

1. Participant has provided written informed consent.

2. Participant is between 18 years of age and 75 years of age, inclusive.

3. Participant must have a Karnofsky Performance Scale (KPS) of >= 70.

4. Participant must have newly diagnosed adult-type diffuse gliomas (World Health Organization Classification 2021) that has not been previously treated with surgery, radiation or chemotherapy (specifically astrocytoma, Isocitrate dehydrogenase (IDH)-mutant or glioblastoma, IDH-wildtype).

5. Based on the pre-operative evaluation by neurosurgeon, participant is a candidate for >= 80% resection of the enhancing region.

6. The primary tumor must be made available for central testing for IDH1 mutation, O6-methylguanine-DNA methyl-transferase (MGMT) methylation status.

7. Willing to provide a blood sample to determine Denovo Genomic Marker 7 (DGM7) status.

8. Laboratory values adequate for patient to undergo surgery, including:

   1. Platelet count >= 60,000/mm^3
   2. Hemoglobin >= 10 g/dL
   3. Absolute neutrophil count (ANC) >= 1,500/mm^3
   4. Absolute lymphocyte count >= 500/mm^3
   5. Total bilirubin <=1.5 x upper limit of normal (ULN) (unless patient had Gilbert's syndrome)
   6. alanine aminotransferase (ALT) <= 2.5 x ULN
   7. Estimated glomerular filtration rate of at least 50 mL/min by Cockcroft Gault Formula

9. Female participants of child-bearing potential and male participants must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) for 30-days prior to the first administration of study drug, for the duration of study participation, and for 90-days following completion of the therapy. Should a female participant become pregnant or suspect a pregnancy while participating in this study, the treating physician must be informed immediately. IF a male participant impregnates or is suspected of impregnating a woman while participating in this study, the treating physician must be informed immediately.

   • A female of child-bearing potential is any women (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria:

   • Has not undergone a hysterectomy or bilateral oophorectomy or
   • Has not had >= 12 months of non-therapy-induced amenorrhea.

10. Participants must not be breastfeeding.

11. Participants must have the ability to understand, and the willingness to comply with the scheduled visits, treatment schedule, laboratory testing and other requirements of the study.

Exclusion Criteria:

Participants may not meet any of the following exclusion criteria to be eligible for study entry:

1. Prior treatment for High Grade Glioma (HGG).

2. History of other malignancy unless the participant has been disease-free for at least 5 years. Adequately treated basal cell carcinoma or squamous cell skin cancer is not exclusionary regardless of time, as well as localized prostate carcinoma or cervical carcinoma in situ after curative treatment.

3. Histological confirmed oligodendroglioma (IDH-mutant and 1p.19q-codeleted) or mixed glioma.

4. A contrast-enhancing brain tumor that is any of the following:

   1. Multi-focal (defined as 2 separate areas of presumed tumor whether contrast enhancing or not, measuring at least 1cm in 2 planes that are not contiguous
   2. Associated with either diffuse subependymal or leptomeningeal dissemination or
   3. > 5cm in any dimension.

5. Participant has or had an active infection requiring antibiotic, antifungal or antiviral therapy in the 4 weeks preceding study Cycle 1: Day 1.

6. Participant has any bleeding diathesis, or must take anticoagulants, or antiplatelet agents, including nonsteroidal anti-inflammatory drugs (NSAIDs), at the time of the scheduled resection that cannot be interrupted for surgery.

7. Participant is HIV positive.

8. Participant has Hepatitis B (positive test for hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb) and positive test for hepatitis B Virus (HBV) DNA) or Hepatitis C (positive tests for hepatitis C Virus (HCV) Antibody and HCV-RNA) or Hepatitis B and C co-infection (positive test for HBsAg or HBcAb and positive test for HCV Antibody).

9. Participant has a history of allergy or intolerance to flucytosine (DB107-FC).

10. Participant has a gastrointestinal disease that would, in the opinion of the Investigator, prevent him or her from being able to swallow or absorb flucytosine.

11. Participant intends to undergo treatment with the Gliadel® wafer at the time of resection surgery or has received Gliadel® wafer < 30 days from Cycle 1: Day 1.

12. Severe pulmonary, cardiac or other systemic disease, which as per Investigator assessment would prevent surgical resection.

13. Participant who have any other disease or condition, which as per Investigator assessment may affect the participant's compliance or place the participant at higher risk of potential treatment complications.

De-identified data may be shared with study collaborators and research partners

Through study closeout