iRGD tumor-penetrating peptide-modified oncolytic adenovirus shows enhanced tumor transduction, intratumoral dissemination and antitumor efficacy.

Endovenously administered oncolytic viruses extravasate and penetrate poorly into tumors. iRGD is a cyclic peptide that enhances tumor penetration when conjugated or coadministered with different types of molecules such as drugs, nanoparticles or phages. iRGD-mediated tumor penetration occurs in three steps: binding to αv-integrins on tumor vasculature or tumor cells, exposure by proteolysis of a C-terminal motif that binds to neuropilin-1 (NRP-1) and cell internalization. We have genetically inserted the iRGD peptide in the fiber C terminus of ICOVIR15K, an oncolytic tumor-retargeted adenovirus to increase its tumor penetration. In vitro, NRP-1 interaction improved binding and internalization of the virus in different cancer cells overexpressing integrins and NRP-1. However, such NRP-1-mediated internalization did not affect transduction or cytotoxicity. In vivo, iRGD did not change the normal organ transduction pattern, with liver and spleen as main targeted organs. In tumors, however, iRGD enhanced transduction and early adenovirus dissemination through the tumor mass leading to an improved antitumor efficacy.

The combination of i-leader truncation and gemcitabine improves oncolytic adenovirus efficacy in an immunocompetent model.

Adenovirus (Ad) i-leader protein is a small protein of unknown function. The C-terminus truncation of the i-leader protein increases Ad release from infected cells and cytotoxicity. In the current study, we use the i-leader truncation to enhance the potency of an oncolytic Ad. In vitro, an i-leader truncated oncolytic Ad is released faster to the supernatant of infected cells, generates larger plaques, and is more cytotoxic in both human and Syrian hamster cell lines. In mice bearing human tumor xenografts, the i-leader truncation enhances oncolytic efficacy. However, in a Syrian hamster pancreatic tumor model, which is immunocompetent and less permissive to human Ad, antitumor efficacy is only observed when the i-leader truncated oncolytic Ad, but not the non-truncated version, is combined with gemcitabine. This synergistic effect observed in the Syrian hamster model was not seen in vitro or in immunodeficient mice bearing the same pancreatic hamster tumors, suggesting a role of the immune system in this synergism. These results highlight the interest of the i-leader C-terminus truncation because it enhances the antitumor potency of an oncolytic Ad and provides synergistic effects with gemcitabine in the presence of an immune competent system.