TMIC-04. TARGETING AN ECM PROTEIN INVOLVED IN BREAST CANCER BRAIN METASTASES WITH AN ONCOLYTIC HSV-1

Abstract The beta-1 subunit of integrins (CD29) is important for cell-extracellular matrix interactions. CD29 expression is increased in breast cancer cells, and it promotes their invasion, migration, and intravasation, all of which can result in breast cancer brain metastasis (BCBM). While CD29 expression can be correlated to poor prognosis of breast cancer patients, the median survival of BCBM patients predicted to have better prognosis is 36 months. Despite current BCBM treatments such as craniotomy, reaching the metastatic site is often challenging. Modified viral vectors, such as oncolytic herpes simplex virus (oHSV), have been clinically approved for the treatment of malignant melanoma and brain tumors, as they infect and selectively kill tumor cells. Previously, we identified that combination of oHSV and humanized CD29 blocking antibody (OS2966, aCD29) enhanced viral replication by reducing antiviral immune response, increased tumor cell killing, and rendered survival benefit to tumor bearing mice with intra-tumoral, but not systemic, oHSV administration. These findings suggested that the antitumor efficacy of the therapeutic combination required intratumoral delivery of anti-CD29, since the antibody could not penetrate the blood brain barrier and reach intracranial tumors. To overcome this, we report the generation of an oHSV encoding the scFv-Fc fragment of this antibody (HSV-aCD29), which retains its oncolytic function, and evaluate the impact of HSV-aCD29 on the CD29 downstream signaling. We will further characterize the safety, antitumor efficacy, and assess the immune response to HSV-aCD29 in vitro and in vivo. We anticipate that compared to our control virus, HSV-aCD29 will block CD29 activity which will reduce antiviral immune responses and enhance tumor cell lysis, thus improving oHSV efficacy. Together, this study proposes the blockade of CD29 with the targeted delivery of a CD29 blocking antibody mediated by a novel oHSV as a potential synergistic therapy against BCBM.