Abstract 4771: The addition of toca 511 and 5-FC to temozolomide improves response in a temozolomide-resistant murine glioblastoma model and correlates with toca 511 dose

Abstract

Abstract Background: Toca 511 (vocimagene amiretrorepvec), an amphotropic retroviral replicating vector (RRV), can successfully and safely deliver a functional, optimized yeast cytosine deaminase (CD) gene to tumors. Within infected cells, CD converts 5-fluorocytosine (5-FC) to the anti-cancer drug 5-fluorouracil (5-FU). The combination of Toca 511 with oral extended release 5-FC (Toca FC), is currently being evaluated in a randomized phase III clinical trial for recurrent high grade glioma (glioblastoma (GBM) and anaplastic astrocytoma) (NCT02414165, Toca 5). Temozolomide (TMZ), in combination with radiation therapy, is the standard of care used for first-line chemotherapy treatment of patients with GBM, the most common and aggressive form of primary brain cancer. Previously, we have shown that: (1) Toca 511/5-FC treatment provides durable response in a syngeneic murine glioma model and supports anti-tumor immune memory; (2) The combination of TMZ and Toca 511/5-FC had synergistic efficacy in a TMZ-sensitive human glioma nude mouse model; (3) TMZ did not inhibit the efficacy of Toca 511/5-FC in a TMZ resistant murine glioma syngeneic model; (4) Toca 511/5-FC caused significant radiosensitization in a radioresistant murine glioma model. Results: To assess the interaction of TMZ with escalating doses of Toca 511 (as defined by percent of tumor transduction by RRV), an orthotopic TMZ-resistant murine glioma model, Tu-2449, was utilized. These results show that moderate levels of tumor transduction of Toca 511 (30% - 50%) with 5-FC treatment prolongs survival in the presence of TMZ compared with lower transduction rates (10%). Additionally, mice treated with Toca 511/5-FC and TMZ are being tested for the establishment of anti-tumor immune memory. Conclusion: These results demonstrate that (1) survival correlates with the transduction levels of Toca 511 when combined with temozolomide in the Tu-2449 orthotopic glioma model and (2) that this combination may support anti-tumor immune memory. These studies along with prior work support evaluation of the combination of Toca 511/5-FC with temozolomide in patients with newly diagnosed GBM (NRG-BN006). Citation Format: Maria E. Rodriguez-Aguirre, Sophie Viaud, Daniel Mendoza, Tiffany Montellano, Derek G. Ostertag, Harry Gruber, Douglas Jolly, Cornelia Bentley. The addition of toca 511 and 5-FC to temozolomide improves response in a temozolomide-resistant murine glioblastoma model and correlates with toca 511 dose [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4771.