519. Intravenous Application of CXCR4 Targeted Conditionally Replicative Adenovirus with Fiber and Hexon Modifications to Pancreatic Cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer-related death in the United States. Most newly diagnosed patients have unresectable disease due to local spread or early aggressive metastasis and have a medial survival of 6 months. Cancer stem cells (CSC) have been found to be involved in the development of metastatic disease. CSC markers such as C-X-C chemokine receptor 4 (CXCR4) and CD133 are overexpressed on the invasive front of PDAC. In this study, we tested a CXCR4-targeted conditionally replicative adenovirus (CRAd) with fiber and hexon modifications toward systemic treatment of PDAC. Due to poor infectivity of CRAd to PDAC cells, our vector contains a modified chimeric fiber which incorporates adenovirus 5 shaft and adenovirus 3 knob (Ad5/3) in order to target PDAC cells via an alternative receptor. The CXCR-4 targeted CRAd with Ad5/3 fiber modification showed strong replication in CD133(+) primary cells isolated from human PDAC tumors. The virus copy number in CD133(+) cells was more than 5 times higher than in CD133(-) cells (p<0.0005). Virus replication capability as measured by luciferase expression from Ad major late promoter was more than double in CD133(+) cells (p<0.05). This data indicates Ad5/3 modified oncolytic adenovirus shows enhanced replication in CSC-rich CD133(+) population. To overcome the issue of adenoviral sequestration upon systemic injection by non-target organs (ie liver, lung), our vector was additionally modified by replacing the Ad5 hexon hypervariable regions 5 and 7 with those from Ad3. We assessed the hexon modified adenovirus in a human Ad replication-permissive model that is most frequently used in IND-directed distribution/toxicology studies, the Syrian hamster. When the virus copy number was assayed after systemic injection via the saphenous vein, the hexon modified virus showed decreased liver sequestration, while showing no difference in the lungs. On the other hand, the major late promoter driven luciferase expression showed much more significant reductions in both liver and lung. The difference between the assays may indicate more contribution of macrophages to the copy number. Next, antitumor effect of the fiber and hexon modified CRAd was assessed in patient-derived xenografts. After intratumoral administration, the fiber-modified CRAd showed antitumor effect compared to the untreated group regardless of the presence (AdCXCR4 E1 F5/3 H5/H3) or absence of (AdCXCR4 E1 F5/3) hexon modification (p<0.01 and 0.05, respectively). On the contrary, with intravenous infection, only the fiber and hexon modified CRAd (AdCXCR4 E1 F5/3 H5/H3) showed significant antitumor effect. We believe that our CXCR4-targeted chimeric fiber and hexon modified CRAd may be employed in advanced PDAC, and that hexon modification of oncolytic adenovirus can be advantageous with systemic administration in the clinical setting.