A novel "cap-linker" strategy to target oncolytic viruses to the tumor

About This Grant

Project Summary Colorectal cancer (CRC) is the third-leading cause of cancer related deaths in the US. Recent advances in cancer immunotherapies, such as immune checkpoint blockade (ICB) targeting PD-1 and other pathways, have gained remarkable progress in the treatment of human cancers. However, PD-1 blockade only works in a fraction of CRCs that harbor microsatellite instability (MSI). Therapeutic options are limited for most CRCs that are microsatellite stable (MSS). However, oncolytic viral therapies have shown promise as a cancer therapy and may prove instrumental for MSS CRCs, with viruses that selectively infect and lyse cancer cells, and simultaneously deliver immune modulating and/or cancer killing payloads. However, major hurdles in the development of oncolytic viral therapies exist. These include non-specific infection of normal tissues by viral vectors, and their inefficient accumulation in tumors upon systemic administration. These limitations restrict the use of oncolytic viruses carrying potent anti-cancer payloads (such as IL-12) to intratumoral injection, precluding their use in cancers that are not surgically reachable. We aim to resolve this limitation and fill the gap of medical need by developing and validating a “cap-linker” strategy to modify the vesicular stomatitis virus (VSV). Our preliminary data show a complete inhibition of viral activity when the VSV Indiana glycoprotein (VSV-GIN) is linked to the human LDL-R cysteine rich (CR)-2 domain (the “cap”) by a flexible, protease cleavable linker. Incorporation of the CR-2 cap into VSV-GIN results in a 700- fold activation of viral infection following linker cleavage. VSVIN harboring the modified VSV-GIN (Pro-VSVIN) with an MMP-cleavable linker showed marked increase in the safety profile compared to its WT counterpart. When injected i.v. into CACO2 human CRC bearing immune deficient mice, Pro-VSVIN achieved tumor-specific distribution and replication, resulting in more than 400-fold higher viral payload expression in the tumor compared to all normal tissues analyzed. When armed with a single chain, biologically active IL-12, i.v. injected Pro-VSVIN eradicates grafted colon tumors, inhibits lung metastatic growth of breast cancer, and enhances the efficacy of anti-PD-1 therapy. With these findings, we hypothesize that following systemic injection, the novel “cap- linker” modification of VSV-G specifically targets VSV to MMP overexpressing tumors, and when armed with immune activating payloads, such as IL-12, exhibits superior efficacy and safety compared to conventional oncolytic viral therapies. We will carry out the following studies to test this hypothesis: 1): Validate the specificity of Pro-VSVIN in MSS CRC; 2) Test the efficacy of Pro-VSVIN-IL-12 for the treatment of CRC; and 3) Optimize the treatment scheme for combined Pro-VSVIN-IL-12 and immune checkpoint blockade in MSS CRC. These investigations will confirm the cancer-specific targeting and efficacy of Pro-VSVIN, and pave the way for its use in human CRC treatments. As overexpression of MMP is common among solid tumors in humans, the impact of this study extends beyond MSS CRC to cancers of diverse origins.