ONCR-177, an Oncolytic HSV-1 Designed to Potently Activate Systemic Antitumor Immunity

Abstract ONCR-177 is an engineered recombinant oncolytic herpes simplex virus (HSV) with complementary safety mechanisms, including tissue-specific miRNA attenuation and mutant UL37 to inhibit replication, neuropathic activity, and latency in normal cells. ONCR-177 is armed with five transgenes for IL12, FLT3LG (extracellular domain), CCL4, and antagonists to immune checkpoints PD-1 and CTLA-4. In vitro assays demonstrated that targeted miRNAs could efficiently suppress ONCR-177 replication and transgene expression, as could the HSV-1 standard-of-care therapy acyclovir. Although ONCR-177 was oncolytic across a panel of human cancer cell lines, including in the presence of type I IFN, replication was suppressed in human pluripotent stem cell–derived neurons, cardiomyocytes, and hepatocytes. Dendritic cells activated with ONCR-177 tumor lysates efficiently stimulated tumor antigen–specific CD8+ T-cell responses. In vivo, biodistribution analyses suggested that viral copy number and transgene expression peaked approximately 24 to 72 hours after injection and remained primarily within the injected tumor. Intratumoral administration of ONCR-177 mouse surrogate virus, mONCR-171, was efficacious across a panel of syngeneic bilateral mouse tumor models, resulting in partial or complete tumor regressions that translated into significant survival benefits and to the elicitation of a protective memory response. Antitumor effects correlated with local and distant intratumoral infiltration of several immune effector cell types, consistent with the proposed functions of the transgenes. The addition of systemic anti–PD-1 augmented the efficacy of mONCR-171, particularly for abscopal tumors. Based in part upon these preclinical results, ONCR-177 is being evaluated in patients with metastatic cancer (ONCR-177-101, NCT04348916).