New generation of oncolytic herpesviruses embodying immunotherapeutic genes encoding IL-12 and anti-PD-1 antibody.

92 Background: Systemic administration of checkpoint inhibitors alone and especially concurrent with intratumoral administration of oncolytic herpes simplex viruses (oHSV) have a major impact on cancer therapy marred by rare failures of healthy organs. Methods: We constructed 3 recombinant oHSVs expressing no immunomodulatory genes (T1 series), murine or human IL-12 (T2 series) and murine or human IL-12 and anti-PD-1 antibody (T3 series). We compared 1) the oncolytic effects of a single or multiple intratumoral injection(s) of T1, T2 and T3 series oHSVs, 2) the effectiveness of intratumoral injection of T3 oHSV with systemic administration of anti PD-1 ab and IL12 alone or in combinations with T1. Results: Insertion of gene encoding PD-1 Ab significantly augmented the oncolytic activity of oHSV bereft of immunostimulatory genes (T1 series) or expressing IL-12 alone (T2 series). In syngeneic mice the T3 series oHSV expressing murine IL-12 and PD-1 Ab was effective against a variety of murine tumors. Concurrent with enhanced cytolytic activity the T3 induced significant intratumoral accumulation of IL-12, PD-1 Ab and IFN-γ. Consistent with an earlier report of an inverse correlation between the volume of the tumor and the quantity of retained IFN-γ. The most effective oncolytic effect resulted from the administration of T3855 expressing both IL12 and anti PD-1 antibody or T2850 concurrently with intraperitoneal administration of anti PD-1 antibody alone. The least effective were single intraperitoneal administration of IL12 or PD-1 antibody. Intratumoral injection of T3 oHSV was most effective against murine tumors in comparison of either systemic administration of anti PD-1 ab and IL12 or intratumoral injection of T1 in combinations of systemic administration of anti PD-1 ab and IL12. Conclusions: We report the marriage in a single therapeutic agent of three distinct cancer therapies: the targeting of cancer cells by oncolytic viruses, the stimulation of immune system by IL12, and the production of immunotherapeutic antibodies against PD-1. The significant finding reported in this article is that the anti-tumor responses remain concentrated in the tumor environment.