The Effects of an Angiogenesis Inhibitor, ATN-224, on the Efficacy of Oncolytic Virus Therapy

Oncolytic viruses (OV) are genetically modified viruses specifically designed to lyse cancerous cells while leaving normal tissue intact. Within the tumor microenvironment, the angiogenic and inflammatory responses following OV inoculation have significantly limited the efficacy of oncolytic herpes simplex virus (oHSV) in clinical trials. Physiological levels of copper support angiogenesis and have been shown to inhibit the infection and replication of wild-type HSV. Here, we tested if OV replication and cytotoxicity are inhibited by copper and if this inhibition can be rescued by ATN-224, a second generation analog of ammonium tetrathiomolybdate (TM). TM is a copper-chelating agent that is FDA-approved for the treatment of Wilson’s disease and is currently under investigation as an anti-angiogenic and anti-neoplastic agent in clinical trials. Under serum concentration of copper, both OV replication and glioma cell killing were significantly inhibited (P<0.001). ATN-224 treatment rescued this copper-mediated inhibition of OV replication and glioma cell destruction in vitro (P<0.01). The anti-tumor efficacy of this combination therapy was evaluated in vivo using two xenograft glioma models. First, mice implanted with subcutaneous U251T3 gliomas were treated with PBS, ATN-224, OV, or OV+ATN224 (n=10). Results indicated that average tumor size in the OV+ATN224 group was significantly smaller compared to OV alone (21.51 vs. 153.93 mm3, P=0.0383). Next, mice implanted with intracranial U87ΔEGFR gliomas were treated as previously (n=8). Kaplan-Meier analysis revealed increased mean survivals for the OV+ATN224 group compared to OV alone (43.875 vs. 24.000 days). Testing for a biological explanation for this enhanced efficacy, we treated mice daily with ATN-224 or PBS via gavage. OV was administered intravenously, and blood was drawn to detect virus presence. Serum derived from ATN-224-treated mice revealed increased viral presence in vivo compared to PBS-treated mouse serum. Analysis of subcutaneous U251T3 tumors from mice receiving intratumoral OV treatment showed that ATN-224-treated tumors had significantly increased viral replication in vivo compared to PBS-treated tumors (P<0.05). Similarly, when OV was administered intravenously, ATN-224-treated tumors again displayed increased viral presence compared to PBS-treated tumors. Therefore, the reduced tumor growth and increased survival previously shown in vivo might be associated with enhanced viral replication. Collectively, our results strongly suggest that the co-treatment of ATN-224 with OV can significantly improve the poor efficacy profile of conventional clinical oncolytic virotherapy.Pelotonia Undergraduate Student Fellowship ProgramA five-year embargo was granted for this item