Abstract 1748: Armed oncolytic adenovirus expressing the positive immune checkpoint OX40L for gastric cancer therapy
Authors: Ossimetha Ashley , Nguyen Teresa , Melendez Natalie , Fan Xuejun , Alonso Marta , Fueyo Juan , Godoy-Vitorino Filipa , Gomez-Manzano Candelaria 
Published: July 2021

Abstract
Gastric cancer is the third leading cause of cancer-related mortality worldwide, with a 5-year survival rate of 30% in the US despite standard treatment. Black, Asian, and non-white Hispanic populations have a 40-50% higher risk of gastric cancer than white people. The poor prognosis and limited therapies associated with gastric cancer has led us to investigate the use of these oncolytic adenoviruses as an alternative treatment. Viroimmunotherapy is showing promising results in preclinical and clinical studies. Our group developed an oncolytic adenovirus, Delta-24-RGD, also named DNX-2401, which has been tested in clinical trials for recurrent glioblastoma, with complete responses and durable survival in 20% of patients, which was associated with an anti-tumor immune response. To further enhance the immune effect of Delta-24-RGD, we developed the next generation virus armed with T cell co-stimulatory agonist, OX40L, termed Delta-24-RGDOX, clinically known as DNX-2440. To explore the sensitivity of gastric cancer to oncolytic adenoviruses, we performed viral infection and replication experiments in a panel of human gastric cancer cells (AGS, MKN-45, SNU-1) and a murine gastric cancer cell line, M12. Cell lines were infected in a dose-dependent experiment using an Ad-GFP-RGD vector, showing that &gt;80% of the culture was infected using a multiplicity of infection of 25 for AGS, 50 for MKN-45 and SNU-1, and 100 for M12. Viral replication in gastric cancer was assessed by hexon staining of 293HEK cells incubated with cell lysates obtained from infected gastric cancer cells, illustrating that infection with either virus resulted in the production of new virions. Consistent with these data, we detected in Delta-24-RGD- and Delta-24-RGDOX-infected gastric cancer cells expression of E1A and hexon, confirming viral infection and replication, respectively. Of interest, 74% to 81% Delta-24-RGDOX-infected gastric cancer cells expressed in their surface OX40L 48 hours post-infection as assessed by flow cytometry. Efficacy of the proposed virotherapy in gastric cancer was visualized by using cell titer blue viability assay, which showed anti-cancer efficacy of the proposed therapy. Results on the efficacy and immune effects of armed-oncolytic adenovirus expressing OX40L in a M12-C57BL/6 gastric cancer immunocompetent mouse model are in progress. Current results suggest that armed oncolytic adenoviruses with positive immunomodulators can effectively infect, replicate, and lyse gastric cancer cells. Ultimately, we aim to translate these oncolytic adenoviruses to the clinic to improve the survival of patients with gastric cancer.
Citation Format: Ashley Ossimetha, Teresa Nguyen, Natalie Melendez, Xuejun Fan, Marta Alonso, Juan Fueyo, Filipa Godoy-Vitorino, Candelaria Gomez-Manzano. Armed oncolytic adenovirus expressing the positive immune checkpoint OX40L for gastric cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1748.