Ad5NULL-A20: A Tropism-Modified, αvβ6 Integrin-Selective Oncolytic Adenovirus for Epithelial Ovarian Cancer Therapies

Purpose: Virotherapies are maturing in the clinical setting. Adenoviruses (Ad) are excellent vectors for the manipulability and tolerance of transgenes. Poor tumor selectivity, off-target sequestration, and immune inactivation hamper clinical efficacy. We sought to completely redesign Ad5 into a refined, tumor-selective virotherapy targeted to alpha v beta 6 integrin, which is expressed in a range of aggressively transformed epithelial cancers but nondetectable in healthy tissues. Experimental Design: Ad5(NULL)-A20 harbors mutations in each major capsid protein to preclude uptake via all native pathways. Tumor-tropism via alpha v beta 6 targeting was achieved by genetic insertion of A20 peptide (NAVPNLRCDLQVLAQK-VART) within the fiber knob protein. The vector's selectivity in vitro and in vivo was assessed. Results: The tropism-ablating triple mutation completely blocked all native cell entry pathways of Ad5(NULL)-A20 via coxsadde and adenovirus receptor (CAR), alpha v beta 3/5 integrins, and coagulation factor 10 (FX). Ad5(NULL)-A20 efficiently and selectively transduced alpha v beta 6(+) cell lines and primary clinical ascites-derived EOC ex vivo, including in the presence of preexisting anti-Ad5 immunity. In vivo biodistribution of Ad5(NULL)-A20 following systemic delivery in non-tumorbearing mice was significantly reduced in all off-target organs, including a remarkable 10(7)-fold reduced genome accumulation in the liver compared with Ad5. Tumor uptake, transgene expression, and efficacy were confirmed in a peritoneal SKOV3 xenograft model of human EOC, where oncolytic Ad5(NULL)-A20-treated animals demonstrated significantly improved survival compared with those treated with oncolytic Ad5. Conclusions: Oncolytic Ad5(NULL)-A20 virotherapies represent an excellent vector for local and systemic targeting of alpha v beta 6-overexpressing cancers and exciting platforms for tumor-selective overexpression of therapeutic anticancer modalities, including immune checkpoint inhibitors. (C) 2018 AACR.