Abstract 1812: ROS-dependent activation of immunogenic glioblastoma cell death & release of immunogenic particles by an autologous cell-based immunotherapeutic platform
Authors: Cultrara Christopher , Kirby Kenneth , Elrazaq Essam , Uhl Christopher , Zellander Amelia , Galluzzi Lorenzo , Exley Mark , Zilberberg Jenny 
Published: April 2023

Background: Imvax is developing a novel personalized immunotherapy platform that combines whole-tumor derived cells with an antisense oligonucleotide against insulin-like growth factor 1-receptor in implantable biodiffusion chambers (BDCs; 0.1 μm pore-size). The lead product, IGV-001, was evaluated in newly diagnosed glioblastoma (GBM) patients in a phase 1b clinical trial. Median overall survival of highest exposure IGV-001-treated ‘Stupp-eligible patients (n=10) was 38.2 months compared with 16.2 months in current standard-of-care-treated patients (p=0.044) (Andrews 2021). Imvax also reported anti-tumor activity of the murine variant of this product, mIGV-001, in the GL261 GBM mouse model and detected mIGV-001-induced immune responses in BDC-draining lymph nodes. Since reactive oxygen species (ROS) overproduction can result in immunogenic cell death, we investigated the role of ROS formation as a mediator of cell death in mIGV-001 as well as the generation of subcellular particles that, when released from the BDCs, may provide a tumor antigen payload with potential anti-tumor activity.

Methods: Mouse (m) or human (h) variants of IGV-001 were prepared using mouse GL261 or human T98G GBM cells, respectively, and BDCs were incubated for 24-48 h. ROS levels were detected by flow cytometry and fluorescence microscopy via oxidation of H2DCF (a fluorescein analog used to quantify ROS in cells) in the presence or absence of the antioxidant N-acetyl-cysteine (NAC). m/hIGV-001 viability was assessed by flow cytometry using Annexin V/7-AAD staining. Particle size distribution in hIGV-001 BDC contents was analyzed using a Nanosight NS300. The transport of subcellular particles (25-90 nm) across the BDC membrane was modeled under dynamic and static conditions using MATLAB® 2022a and confirmed by in vitro studies.

Results: After 24 h in vitro, ROS levels in mIGV-001 were significantly increased along with overt cell death. ROS scavenging with NAC resulted in a cell viability rescue of approximately 50% (from ~40% to ~60% viable cells). Similar trends, although of reduced magnitude, were observed in hIGV-001. Particle analysis within hIGV-001 BDCs showed that after 48 h in culture, dead cells produced particles small enough to diffuse through the BDC membrane. Computational models corroborated that under static conditions, particle equilibrium inside and outside BDCs was achieved after 40 h, 80 h, and 260 h for 25 nm, 50 nm, and 90 nm particles, respectively. Under dynamic conditions, equilibrium was reached in less than 5 h irrespective of particle size.

Conclusions: The use of a surgically implantable drug-device combination product induces ROS-associated immunogenic cell death and generation of a tumor-derived immunogenic payload that can be taken up by local DCs, which travel to the proximal draining lymph nodes to activate anti-tumor T cells.

Citation Format: Christopher Cultrara, Kenneth Kirby, Essam Elrazaq, Christopher Uhl, Amelia Zellander, Lorenzo Galluzzi, Mark Exley, Jenny Zilberberg. ROS-dependent activation of immunogenic glioblastoma cell death & release of immunogenic particles by an autologous cell-based immunotherapeutic platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1812.