Ad5_NULL-A20: A Tropism-Modified, αvβ6 Integrin-Selective Oncolytic Adenovirus for Epithelial Ovarian Cancer Therapies.

Abstract

<b>Purpose:</b> 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 αvβ6 integrin, which is expressed in a range of aggressively transformed epithelial cancers but nondetectable in healthy tissues.<b>Experimental Design:</b> Ad5_NULL-A20 harbors mutations in each major capsid protein to preclude uptake via all native pathways. Tumor-tropism via αvβ6 targeting was achieved by genetic insertion of A20 peptide (NAVPNLRGDLQVLAQKVART) within the fiber knob protein. The vector's selectivity <i>in vitro</i> and <i>in vivo</i> was assessed.<b>Results:</b> The tropism-ablating triple mutation completely blocked all native cell entry pathways of Ad5_NULL-A20 via coxsackie and adenovirus receptor (CAR), αvβ3/5 integrins, and coagulation factor 10 (FX). Ad5_NULL-A20 efficiently and selectively transduced αvβ6⁺ cell lines and primary clinical ascites-derived EOC <i>ex vivo</i>, including in the presence of preexisting anti-Ad5 immunity. <i>In vivo</i> biodistribution of Ad5_NULL-A20 following systemic delivery in non-tumor-bearing mice was significantly reduced in all off-target organs, including a remarkable 10⁷-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.<b>Conclusions:</b> Oncolytic Ad5_NULL-A20 virotherapies represent an excellent vector for local and systemic targeting of αvβ6-overexpressing cancers and exciting platforms for tumor-selective overexpression of therapeutic anticancer modalities, including immune checkpoint inhibitors. <i>Clin Cancer Res; 24(17); 4215-24. ©2018 AACR</i>.