Abstract 3253: Novel gene & protein-carrying vector BC-PIV expressing immunomodulatory molecules potently stimulates anti-tumor immunity against solid tumors in mice

Abstract Background: Cancer immunotherapy such as immune-checkpoint inhibitors or CAR-T cell therapy has emerged as an effective therapeutic modality for some cancers such as hematological malignancies. However, they still show little efficacy for many solid tumors, because of their immune suppressive microenvironment. BC-PIV is a replication-deficient viral vector derived from human parainfluenza virus type 2, that can convey two ectopic genes simuoltaneously and uniquely display ectopic proteins with intact steric structure on the surface of viral particles. Furthermore, BC-PIV itself can induce maturation of dendritic cells with efficient induction of CD80/86. These unique characteristics of BC-PIV make it an attractive tool for improving anti-tumor responses under immunesuppressive milieu of solid tumors. Aim and Methods: To develop novel immunotherapy using BC-PIV, we have introduced various immunomodulatory molecules into BC-PIV and tested their anti-tumor efficacy in vivo. To activate CD4/8 positive T cells, we introduced genes for OX-40L, 4-1BBL, GITRL, CD30L, OX40L/4-1BBL, OX40L/GITRL, or 4-1BBL/GITRL (collectively, TNFRSF ligands) to BC-PIV. All gene products were effectively presented on BC-PIV envelope. For expansion of T, B, and NK cells, or for promoting migration of immune cells, genes for IL-7, CCL19, IL-7/CCL19, IL-7/CCL21, or IL-12 (P40/P35) were introduced. CT-26 murine colon cancer cells (5 × 105) were implanted into syngeneic Balb/c mice at one or both side (s) of their ventral wall. Approximately 107 viral particles derived from BC-PIV carrying immunomodulatory molecules were directly injected into tumors that had grown to 5-7mm in diameter, and the anti-tumor efficacy was assessed by monitoring the tumor size. Results: In the mice treated with BC-PIV carrying TNFRSF ligands, tumor regression was observed at the virus administered site, but also at the non-treated, distant site, possibly due to the Abscopal effect. Moreover, these mice maintained efficient anti-tumor responses and rejected tumors when they were re-challenged with CT-26 cells at 8 months after the initial BC-PIV treatment, showing that BC-PIV/TNFRSF ligands induced sustained anti-tumor immunity. In the BC-PIV/IL-7/CCL19-treated mice, the tumors began to shrink about six days after the single injection of the virus. This effect was even more enhanced by concurrent administration of anti-PD-1 antibody. Conclusions: BC-PIV carrying TNFRSF ligands, cytokines or chemokines induced efficient, sustained anti-tumor immunity and eradicated tumors in in vivo solid tumor model. Unique characteristics of BC-PIV, being able to deliver two genes simultaneously and to display ectopic proteins with intact steric structure on the viral surface, make this vector an attractive, novel platform for next generation cancer immunotherapy. Citation Format: Masayuki Fukumura, Junpei Ohtsuka, Tomomi Ohtsuka, Hideaki Nakajima, Tetsuya Nosaka. Novel gene Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3253.