To expand our current array of safe and potent oncolytic viruses, we screened a variety of wild-type (WT) rhabdoviruses against a panel of tumor cell lines. Our screen identified a number of viruses with varying degrees of killing activity. Maraba virus was the most potent of these strains. We built a recombinant system for the Maraba virus platform, engineered a series of attenuating mutations to expand its therapeutic index, and tested their potency in vitro and in vivo. A double mutant (MG1) strain containing both G protein (Q242R) and M protein (L123W) mutations attenuated Maraba virus in normal diploid cell lines, yet appeared to be hypervirulent in cancer cells. This selective attenuation was mediated through interferon (IFN)-dependent and -independent mechanisms. Finally, the Maraba MG1 strain had a 100-fold greater maximum tolerable dose (MTD) than WT Maraba in vivo and resulted in durable cures when systemically administered in syngeneic and xenograft models. In summary, we report a potent new oncolytic rhabdovirus platform with unique tumor-selective attenuating mutations.

Efforts to selectively target and disrupt established tumor vasculature have largely failed to date. We hypothesized that a vaccinia virus engineered to target cells with activation of the ras/MAPK signaling pathway (JX-594) could specifically infect and express transgenes (hGM-CSF, b-galactosidase) in tumor-associated vascular endothelial cells in humans. Efficient replication and transgene expression in normal human endothelial cells in vitro required either VEGF or FGF-2 stimulation. Intravenous infusion in mice resulted in virus replication in tumor-associated endothelial cells, disruption of tumor blood flow, and hypoxia within 48 hours; massive tumor necrosis ensued within 5 days. Normal vessels were not affected. In patients treated with intravenous JX-594 in a phase I clinical trial, we showed dose-dependent endothelial cell infection and transgene expression in tumor biopsies of diverse histologies. Finally, patients with advanced hepatocellular carcinoma, a hypervascular and VEGF-rich tumor type, were treated with JX-594 on phase II clinical trials. JX-594 treatment caused disruption of tumor perfusion as early as 5 days in both VEGF receptor inhibitor-na€ ve and -refractory patients. Toxicities to normal blood vessels or to wound healing were not evident clinically or on MRI scans. This platform technology opens up the possibility of multifunctional engineered vaccinia products that selectively target and infect tumorassociated endothelial cells, as well as cancer cells, resulting in transgene expression, vasculature disruption, and tumor destruction in humans systemically. Cancer Res; 73(4); 1265-75. Ó2012 AACR.