Local Delivery of OncoVEX(mGM-CSF) Generates Systemic Antitumor Immune Responses Enhanced by Cytotoxic T-Lymphocyte-Associated Protein Blockade.

Purpose: Talimogene laherparepvec, a new oncolytic immunotherapy, has been recently approved for the treatment of melanoma. Using a murine version of the virus, we characterized local and systemic antitumor immune responses driving efficacy in murine syngeneic models.Experimental Design: The activity of talimogene laherparepvec was characterized against melanoma cell lines using an in vitro viability assay. Efficacy of OncoVEXmGM-CSF (talimogene laherparepvec with the mouse granulocyte-macrophage colony-stimulating factor transgene) alone or in combination with checkpoint blockade was characterized in A20 and CT-26 contralateral murine tumor models. CD8+ depletion, adoptive T-cell transfers, and Enzyme-Linked ImmunoSpot assays were used to study the mechanism of action (MOA) of systemic immune responses.Results: Treatment with OncoVEXmGM-CSF cured all injected A20 tumors and half of contralateral tumors. Viral presence was limited to injected tumors and was not responsible for systemic efficacy. A significant increase in T cells (CD3+/CD8+) was observed in injected and contralateral tumors at 168 hours. Ex vivo analyses showed these cytotoxic T lymphocytes were tumor-specific. Increased neutrophils, monocytes, and chemokines were observed in injected tumors only. Importantly, depletion of CD8+ T cells abolished all systemic efficacy and significantly decreased local efficacy. In addition, immune cell transfer from OncoVEXmGM-CSF-cured mice significantly protected from tumor challenge. Finally, combination of OncoVEXmGM-CSF and checkpoint blockade resulted in increased tumor-specific CD8+ anti-AH1 T cells and systemic efficacy.Conclusions: The data support a dual MOA for OncoVEXmGM-CSF that involves direct oncolysis of injected tumors and activation of a CD8+-dependent systemic response that clears injected and contralateral tumors when combined with checkpoint inhibition. Clin Cancer Res; 23(20); 6190-202. ©2017 AACR.

Moesta AK ，Cooke K ，Piasecki J ，Mitchell P ，Rottman JB ，Fitzgerald K ，Zhan J ，Yang B ，Le T ，Belmontes B ，Ikotun OF ，Merriam K ，Glaus C ，Ganley K ，Cordover DH ，Boden AM ，Ponce R ，Beers C ，Beltran PJ ... -  《-》

OncoVEX(mGM-CSF)expands tumor antigen-specific CD8+ T-cell response in preclinical models.

Checkpoint inhibitors targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) have demonstrated clinical efficacy in advanced melanoma, but only a subset of patients with inflamed tumors are responsive. Talimogene laherparepvec (T-VEC), a modified herpes simplex virus type 1 (HSV-1) expressing granulocyte-macrophage colony-stimulating factor (GM-CSF), is a first-in-class oncolytic immunotherapy approved for the treatment of melanoma and has been shown to inflame the tumor microenvironment. To evaluate the potential and mechanisms of T-VEC to elicit systemic antitumor immunity and overcome resistance to checkpoint inhibitors in murine tumor models, OncoVEXmGM-CSF was developed similarly to T-VEC, except the human GM-CSF transgene was replaced with murine GM-CSF. Previous work had demonstrated that OncoVEXmGM-CSF generated systemic antitumor immunity dependent on CD8+ T cells in an immune checkpoint-sensitive tumor cell model. A novel B16F10 syngeneic tumor model with both HSV-1-permissive subcutaneous tumors and HSV-1-refractory experimental lung metastasis was used to study the local and systemic effects of OncoVEXmGM-CSF treatment alone or in combination with checkpoint inhibitors. Intratumoral injection of OncoVEXmGM-CSF in combination with an anti-CTLA-4 or anti-PD-1 blocking antibody led to increased tumor growth inhibition, a reduction in the number of lung metastases, and prolonged animal survival. OncoVEXmGM-CSF induced both neoantigen-specific and tumor antigen-specific T-cell responses. Furthermore, cured mice from the combination treatment of OncoVEXmGM-CSF and anti-CTLA-4 antibody rejected tumor rechallenges. These data support the concept that T-VEC and checkpoint inhibition may be an effective combination to treat patients with advanced melanoma.

Estrada J ，Zhan J ，Mitchell P ，Werner J ，Beltran PJ ，DeVoss J ，Qing J ，Cooke KS ... -  《Journal for ImmunoTherapy of Cancer》

The Efficacy of Oncolytic Adenovirus Is Mediated by T-cell Responses against Virus and Tumor in Syrian Hamster Model.

Oncolytic adenoviruses (Ad) represent an innovative approach to cancer therapy. Its efficacy depends on multiple actions, including direct tumor lysis and stimulation of antiviral and antitumor immune responses. In this study, we investigated the roles of T-cell responses in oncolytic adenoviral therapy. An immunocompetent and viral replication-permissive Syrian hamster tumor model was used. The therapeutic mechanisms of oncolytic Ad were investigated by T-cell deletion, immunohistochemical staining, and CTL assay. Deletion of T cells with an anti-CD3 antibody completely demolished the antitumor efficacy of oncolytic Ad. Intratumoral injection of Ad induced strong virus- and tumor-specific T-cell responses, as well as antiviral antibody response. Both antiviral and antitumor T-cell responses contributed to the efficacy of oncolytic Ad. Deletion of T cells increased viral replication and extended the persistence of infectious virus within tumors but almost abrogated the antitumor efficacy. Preexisting antiviral immunity promoted the clearance of injected oncolytic Ad from tumors but had no effect on antitumor efficacy. Strikingly, the repeated treatment with oncolytic Ad has strong therapeutic effect on relapsed tumors or tumors insensitive to the primary viral therapy. These results demonstrate that T cell-mediated immune responses outweigh the direct oncolysis in mediating antitumor efficacy of oncolytic Ad. Our data have a high impact on redesigning the regimen of oncolytic Ad for cancer treatment. Clin Cancer Res; 23(1); 239-49. ©2016 AACR.

Li X ，Wang P ，Li H ，Du X ，Liu M ，Huang Q ，Wang Y ，Wang S ... -  《-》

Concurrent delivery of GM-CSF and endostatin genes by a single adenoviral vector provides a synergistic effect on the treatment of orthotopic liver tumors.

The immune resistance of large tumors represents a major problem for cancer immunotherapy, whereas the need for repeated injections of high doses of recombinant anti-angiogenic proteins represents a similar problem for anti-angiogenic therapy. To test whether antitumor activity could be increased by combining the above two mechanisms, this study examined the therapeutic effect of combination gene therapy using a murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) gene and a human endostatin (hED) gene on a rat orthotopic liver tumor model. An adenoviral vector was constructed that simultaneously carried two transcriptional cassettes, for the expression of mGM-CSF and hED, respectively, or that carried a single cassette of either gene. The adenoviruses were intratumorally administered to 3-day-old or 7-day-old tumors. Moreover, the antitumor effects of the combination therapy and monotherapy were assessed and compared. The double-gene-containing adenoviral vector expressed transgenes as efficiently as the single-gene-containing vector. Moreover, the adenovirally expressed endostatin was biologically active, as demonstrated in vitro and in vivo. Results from animal experiments demonstrated a synergistic antitumor effect induced by the combined mGM-CSF and hED therapy. The combination of hED with mGM-CSF enhanced tumor-specific CTL activity, but did not interfere with the infiltration of cellular effectors in the tumor regions. The blood vessel density of the liver tumors markedly reduced as a result of hED expression in both monotherapy and combination therapy. Furthermore, combination therapy significantly increased the number of apoptotic cells in the tumor regions. The experimental results suggest that the combined gene therapy against tumor cells and the tumor vascular system using antitumor immune mechanisms and anti-angiogenic mechanisms holds promise as a strategy for treating cancers.

Tai KF ，Chen PJ ，Chen DS ，Hwang LH ... -  《JOURNAL OF GENE MEDICINE》

An Oncolytic Adenovirus Encoding Decorin and Granulocyte Macrophage Colony Stimulating Factor Inhibits Tumor Growth in a Colorectal Tumor Model by Targeting Pro-Tumorigenic Signals and via Immune Activation.

Liu Z ，Yang Y ，Zhang X ，Wang H ，Xu W ，Wang H ，Xiao F ，Bai Z ，Yao H ，Ma X ，Jin L ，Wu C ，Seth P ，Zhang Z ，Wang L ... -  《-》