Retargeted and Multi-cytokine-Armed Herpes Virus Is a Potent Cancer Endovaccine for Local and Systemic Anti-tumor Treatment

Abstract

Oncolytic viruses (OVs) are novel anti-tumor agents with the ability to selectively infect and kill tumor cells while sparing normal tissue. Beyond tumor cytolysis, OVs are capable of priming an anti-tumor immune response via lysis and cross-presentation of locally expressed endogenous tumor antigens, acting as an “endovaccine.” The effectiveness of OVs, similar to other immunotherapies, can be hampered by an immunosuppressive tumor microenvironment. In this study, we modified a previously generated oncolytic herpes simplex virus (oHSV) retargeted to the human HER2 (hHER2) tumor molecule and encoding murine interleukin-12 (mIL-12), by insertion of a second immunomodulatory molecule, murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), to maximize therapeutic efficacy. We assessed the efficacy of this double-armed virus (R-123) compared to singly expressing GM-CSF and IL-12 oHSVs in tumor-bearing mice. While monotherapies were poorly effective, combination with α-PD1 enhanced the anti-tumor response, with the highest efficacy of 100% response rate achieved by the combination of R-123 and α-PD1. Efficacy was T cell-dependent, and the induced immunity was long lasting and able to reject a second contralateral tumor. Importantly, systemic delivery of R-123 combined with α-PD1 was effective in inhibiting the development of tumor metastasis. As such, this approach could have a significant therapeutic impact paving the way for further development of this platform in cancer immunotherapy.

Generation of a Novel Mesothelin-Targeted Oncolytic Herpes Virus and Implemented Strategies for Manufacturing

“…An emerging approach to maximize the efficacy of oncolytic viruses involves arming them with payloads to enhance antitumor immunity [ 1 ]. We and others recently demonstrated that interleukin 12 (IL12) significantly enhanced the antitumor efficacy of a retargeted oncolytic virus through T cell activation [ 23 , 66 ]. Based on these evidences, we devised an arming strategy to insert IL12 into the intergenic site between viral US1 and US2 genes of THV_SS1 ( Figure 2 c) as preparatory for preclinical translation.…”

“…The use of viral vectors for gene therapy, vaccine delivery, and oncolytic viruses is now a reality, with thousands of clinical trials completed, ongoing, or approved worldwide [ 1 , 3 , 82 , 83 ]. Oncovirotherapy with retargeted viruses is revealing a promising potential for the treatment of many cancer indicators, including breast cancer [ 7 , 23 , 47 , 66 , 84 ]. We recently characterized preclinical models of HER2-positive tumors in the framework of combination with checkpoint inhibitors [ 7 , 23 , 47 ].…”

“…Oncovirotherapy with retargeted viruses is revealing a promising potential for the treatment of many cancer indicators, including breast cancer [ 7 , 23 , 47 , 66 , 84 ]. We recently characterized preclinical models of HER2-positive tumors in the framework of combination with checkpoint inhibitors [ 7 , 23 , 47 ]. Among breast cancer, triple-negative tumors are characterized by lack of canonical breast receptors (i.e., HER2, ER, PR) amenable by targeted therapeutics.…”

“…Namely, triple-negative cell lines with higher levels of mesothelin were effectively killed by MSLN-THV, while the cell lines showing the lowest levels of MSLN expression were refractory to the retargeted virus; this may also take into account the natural variability of different cellular backgrounds, in terms of susceptibility to viral infection. The most effective mesothelin targeted herpes virus (THV_SS1) described in this study was further implemented by encoding murine IL12 immunostimulatory cytokine as the latter was recently demonstrated to synergize with HER2-retargeted herpes virus in mediating systemic anti-tumor immunity [ 23 , 66 ]. The availability of an unarmed, and of the corresponding IL12 armed viruses, will allow to initiate preclinical studies, evaluating the suitability of these oncolytic constructs to co-operate with immune checkpoint blockade in human mesothelin-tolerant, immunocompetent murine models.…”

“…Similarly to CAR-T cells, targeted Herpes viruses (THVs) can be potentially redirected to any tumor antigen of interest, by substitution of an essential moiety of viral glycoproteins (i.e., gD) with a TAA-targeting antibody fragment (scFv). The use of THVs allows to exploit the best of both targeted therapy and cancer immunotherapy, as recently demonstrated in preclinical combination settings with PD-1 inhibitor [ 7 , 23 ]. The self-origin of such tumor associated antigens (e.g., HER2) increases the potential risk of deleterious on-target, off-tumor toxicity; for these reasons, we recently published a proof-of-concept of dual restriction by combining the retargeting to HER2 to replicative conditioning to cancer cells by the SurE_oHSV hosting surviving promoter driving ICP4 expression [ 7 ].…”