Abstract 695: Immunostimulatory gene therapy with an oncolytic virus expressing TMZ-CD40L and 4-1BBL induces oncolysis and show immunomodulatory capacity in soft tissue sarcoma
Authors: Calandigary Ahmed , Labani-Motlagh Alireza , Tamindzic Darko , Lövgren Tanja , Eriksson Emma , Loskog Angelica 
Published: April 2023

Abstract
Soft-tissue sarcoma (STS) is a heterogeneous group of cancers, affecting both children and adults that develops from muscle, fat, tendons, vessels or connective tissues. Childhood STS accounts for up to 8% of all diagnosed pediatric cancer with rhabdomyosarcoma as the most common form. Prognosis depends on the type, stage and localization of the tumor, with a general 5-year survival of 70% for all STS patients. However, for patients with metastatic disease 5-year survival is 15%. The most common treatment for pediatric STS is surgery with adjuvant chemotherapy, and if possible radiotherapy. Immunotherapy, such as checkpoint blockade inhibitors (CPI), has revolutionized treatment for other malignancies such as melanoma. However, CPIs have shown limited efficacy in STS overall, and even less in pediatric patients. Thus, there is a strong need for new treatment options. Herein, we study a novel immunostimulatory gene therapy based on an oncolytic adenovirus, LOAd703, for efficacy in STS. LOAd703 is currently under clinical evaluation for several other solid cancers. LOAd703 is derived from the LOAd family of serotype 5/35 adenoviruses dependent on host cell entry via CD46. Modification of E1A has been introduced for selective replication and lysis of tumor cells. Moreover, LOAd703 is armed with the immunostimulatory genes trimerized, membrane-bound (TMZ)-CD40L and 4-1BBL expressed under control of a CMV promoter. A panel of 11 different cell lines from different STS subtypes and from both pediatric and adult patients were shown to express CD46 by flow cytometry before treatment. The cell lines were subsequently infected with LOAd703. CD46 expression was retained after infection and the infected cells upregulated the expression of the transgenes TMZ-CD40L and 4-1BBL. In addition, qPCR analysis confirmed LOAd703 replication in all tested cell lines in a time dependent manner. Replication induced oncolysis of all investigated cell lines, as analyzed by an MTS cell viability assay. In a co-culture system with peripheral blood mononuclear cells and infected sarcoma cells, preliminary results showed an alteration of markers associated with differentiation and activation among both innate and adaptive immune cells, including myeloid cells, NK cells and T cells. In conclusion, LOAd703 demonstrated a high oncolytic capacity and expression of the immunostimulatory transgenes in STS cells. Preliminary data shows that infected STS cells stimulate immune cells via the TMZ-CD40L and 4-1BBL transgenes. More in depth analysis will be performed on co-culture experiments to pinpoint the exact effect on different immune cell compartments. We are also performing multiplex analysis of proteomic changes in infected tumor cells using the OLINK® TARGET 96 assay. Finally, we willconfirm the effect of LOAd703 in vivo in a murine xenograft model for STS.
Citation Format: Ahmed Calandigary, Alireza Labani-Motlagh, Darko Tamindzic, Tanja Lövgren, Emma Eriksson, Angelica Loskog. Immunostimulatory gene therapy with an oncolytic virus expressing TMZ-CD40L and 4-1BBL induces oncolysis and show immunomodulatory capacity in soft tissue sarcoma [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 695.