Preclinical safety assessment of an oncolytic herpes simplex virus type 2 expressed PD-L1/CD3 bispecific antibody.

Oncolytic virotherapy is an emerging and safe therapeutic approach based on the inherent cytotoxicity of oncolytic viruses and their ability to replicate and spread within tumors in a selective manner. We constructed a new type of oncolytic herpes simplex virus armed with Bispecific Antibody (BsAb) molecules targeting PD-L1/CD3 (oHSV2-PD-L1/CD3-BsAb) to treat human malignancies. We demonstrated the anti-tumor efficacy of oHSV2-PD-L1/CD3-BsAb. To move forward with clinical trials of oHSV2-PD-L1/CD3-BsAb, we conducted a comprehensive preclinical safety evaluation, including hemolysis test, anaphylaxis test, repeated dose toxicity test in cynomolgus monkeys, biodistribution in cynomolgus monkeys and tissue cross-reactivity of PD-L1/CD3-BsAb with human and cynomolgus monkey tissues in vitro. Our preclinical safety evaluation indicated that oHSV2-PD-L1/CD3-BsAb is safe and suitable for clinical trials. After undergoing a thorough evaluation by the United States Food and Drug Administration (FDA), oHSV2-PD-L1/CD3-BsAb has successfully obtained approval to initiate Phase I clinical trials in the United States (FDA IND: 28717).

Immune-check blocking combination multiple cytokines shown curative potential in mice tumor model.

OBJECTIVE: In order to ensure the stable transcription of target genes, we constructed a eukaryotic high expression vector carrying an immune-check inhibitor PD-1v and a variety of cytokines, and studied their effects on activating immune response to inhibit tumor growth. METHODS: A novel eukaryotic expression plasmid vector named pT7AMPCE containing T7RNA polymerase, T7 promoter, internal ribosome entry site (IRES), and poly A tailing signal was constructed by T4 DNA ligase, on which homologous recombination was used to clone and construct the vector carrying PD-1v, IL-2/15, IL-12, GM-CSF, and GFP. In vitro transfection of CT26 cells was performed, and the protein expression of PD-1v, IL-12 and GM-CSF was detected by Western blot and ELISA after 48 h. Mice were subcutaneously inoculated with CT26-IRFP tumor cells in the rib abdomen, and the tumor tissues were injected with PD-1v, IL-2/15, IL-12, and GM-CSF recombinant plasmids for treatment during the experimental period. The efficacy of the treatment was evaluated by assay tumor size and survival time of tumor-bearing mice during the experiment. Expression levels of IFN-γ, TNF, IL-4, IL-2, and IL-5 in mouse blood were measured using the CBA method. Tumor tissues were extracted and immune cell infiltration in tumor tissues was detected by HE staining and the IHC method. RESULTS: The recombinant plasmids carrying PD-1v, IL-2/15, IL-12, and GM-CSF were successfully constructed, and the Western blot and ELISA results showed that PD-1v, IL-12, and GM-CSF were expressed in the supernatant of CT26 cells 48 h after in vitro cell transfection. The combined application of PD-1v, IL-2/15, IL-12, and GM-CSF recombinant plasmids significantly inhibited tumor growth in mice, and the tumor growth rate was significantly lower than that in the blank control group and GFP plasmid control group (p < 0.05). Cytometric bead array data suggested that the combination of PD-1v and various cytokines can effectively activate immune cells. HE and IHC analysis revealed plenty of immune cell infiltrates in the tumor tissue, and a large proportion of tumor cells showed the necrotic phenotype in the combination treatment group. CONCLUSION: The combination of immune check blockade and multiple cytokine therapy can significantly activate the body's immune response and inhibit tumor growth.

Transarterial viroembolization improves the therapeutic efficacy of immune-excluded liver cancer: Three birds with one stone.

OBJECTIVE: To investigate the mechanism and efficacy of transarterial viroembolization (TAVE) with an oncolytic virus (OH2) for the treatment of liver cancer in rabbit VX2 tumor models. MATERIALS AND METHODS: Subcutaneous tumor and liver cancer models were established to determine the optimal viral titer and administration modality of OH2. Different liver cancer models were established to evaluate the locoregional tumor response, synergistic and standby effects, survival benefit, and specific antitumor immune memory after TAVE treatment. The immune cell densities in tumor tissues were measured. RESULTS: The optimal viral titer of OH2 was 1 × 107 CCID50. TAVE was the most effective modality with greater homogeneous OH2 distribution and therapeutic efficacy compared to other administration routes of transarterial virus infusion (TAVI), commonly adopted intratumor injection (TI), and intravenous injection (IV). Additionally, TAVE treatment significantly improved the locoregional tumor response, standby effect, and survival benefit compared to the TAVI, transarterial embolization (TAE), and control groups. TAVE modified the immune cell densities for immune-excluded liver cancer, partially destroyed vessel metastases, and established antitumor immune memory. The synergistic treatment efficacy of TAVE was superior to the simple addition of two independent monotherapies. CONCLUSION: TAVE was the optimal and a safe modality for treating immune-excluded liver cancer, and its synergistic effect achieved a remarkable tumor response, standby effect, survival benefit, and antitumor immune memory, which providing an innovative therapeutic modality for clinical practice. DATA AVAILABILITY: Data is available from the corresponding author upon requirement.

A novel cocktail therapy based on quintuplet combination of oncolytic herpes simplex virus-2 vectors armed with interleukin-12, interleukin-15, GM-CSF, PD1v, and IL-7 × CCL19 results in enhanced antitumor efficacy.

BACKGROUND: Selectively replicating herpes simplex virus-2 (HSV-2) vector is a promising treatment for cancer therapy. The insertion of multiple transgenes into the viral genome has been performed to improve its oncolytic activity. METHODS: Herein, we simultaneously constructed five "armed" oncolytic viruses (OVs), designated oHSV2-IL12, -IL15, GM-CSF, -PD1v, and IL7 × CCL19. These OVs delete the ICP34.5 and ICP47 genes with the insertion of transgenes into the deleted ICP34.5 locus. The anti-tumor efficacy in vivo was tested in the syngeneic 4T1 and CT26 tumor-bearing mice model. RESULTS: The OVs showed comparable oncolytic capability in vitro. The combination therapy of oHSV2-IL12, -IL15, GM-CSF, -PD1v, and IL7 × CCL19 exhibited the highest tumor inhibition efficacy compared with the treatment of single OV or two OVs combination. CONCLUSIONS: The OVs armed with different transgenes combination therapy also named 5-valent oHSV2 (also called cocktail therapy) might be an effective therapeutic strategy for solid tumors.

Bispecific Antibody Expressed by an Oncolytic Herpes Simplex Virus Type 2 Can Transform Heterologous T Cells Into Uniform Tumor Killer Cells.

BsAb (bispecific antibody)-armed oncolytic viruses (OVs) are effective in regulating tumor microenvironment. However, oHSV2 (oncolytic herpes simplex virus type 2) expressing immune checkpoints targeting BsAb molecules are not reported. Here, we generated oHSV2-armed PD-L1/CD3 BsAb and established pharmacodynamic evaluation models, which suggested that our oHSV2-BsAb molecules have an improved oncolytic potency in vitro and in vivo. The oHSV2 viruses armed with BsAb molecules targeting programmed cell death ligand 1 (PD-L1)/CD3 or CD19/CD3 (oHSV2-PD-L1/CD3-BsAb or oHSV2-CD19/mCD3-BsAb) were constructed; besides inducing oncolysis in virus-infected tumor cells, the modified oncolytic virus oHSV2-PD-L1/CD3-BsAb can also activate peripheral blood mononuclear cells (PBMCs) by releasing PD-L1/CD3 BsAb and thereby induce PBMC-mediated killing of PD-L1-positive tumor cells, regardless of PD-L1 expression level. The expressed PD-L1/CD3 BsAb can upregulate the activation markers of T cells in PBMCs and induce different cytokine secretion. The activation of T cells and the enrichment of related immune regulatory pathways are further confirmed by proteomics. It also demonstrated that the OVs or PBMCs could upregulate PD-L1 expression on the surface of tumor cells through transforming "cold tumors" with low PD-L1 expression into "hot tumors" with high PD-L1 expression, which can facilitate the targeting of BsAb molecules and enhance the effect of oncolysis. oHSV2-PD-L1/CD3-BsAb or oHSV2-CD19/mCD3-BsAb showed an enhanced oncolytic effect in vitro and in vivo compared to backbone virus oHSV2-GFP. Our results showed that the newly designed oHSV2-BsAb had enhanced therapeutic effects against solid tumors and provided a new option of immunotherapy.

BGC823 Cell Line with the Stable Expression of iRFP720 Retains Its Primary Properties with Promising Fluorescence Imaging Ability.

Reliable animal models are required for understanding the molecular events of gastric tumor growth and metastasis. Tracing techniques based on iRFP720 may optimize the noninvasive monitoring of tumors in vivo. The present study established a human gastric adenocarcinoma cell line BGC823-iRFP720-GFP (abbreviated as BGC823-iRFP) that stably expressed iRFP720 and green fluorescent protein (GFP) by piggyBac transposon system. The monoclonal cell line BGC823-iRFP was isolated under puromycin selection. The cell morphology and proliferation ability of BGC823-iRFP cells in vitro were similar to that of the BGC823 cells. The iRFP720 and GFP expressions were confirmed by laser confocal microscopy and Cytation™ 5. Hematoxylin and eosin staining, immunohistochemical analysis, and animal experiments also revealed that BGC823-iRFP exhibited no significant changes in morphology, growth kinetics, and tumorigenicity in vivo. IVIS Lumina III imaging indicated that the iRFP720 signals of the BGC823-iRFP cells could be used to evaluate the antitumor efficacy of oncolytic viruses and chemotherapy drugs. Therefore, the BGC823-iRFP cells would be a useful tool for gastric cancer research and antitumor drug evaluation.

The construction of a new oncolytic herpes simplex virus expressing murine interleukin-15 with gene-editing technology.

The treatment of tumors with oncolytic viruses is an important cancer immunotherapy strategy. Interleukin-15 (IL-15) can enhance the antitumor effect of natural killer cells and T cells. An oncolytic herpes simplex type II virus (oHSV2-mIL-15CherryFP) expressing mouse IL-15 was constructed using the CRISPR/Cas9 system, and its antitumor activity in vitro and in vivo was evaluated. In vitro, the mouse interleukin-15 (mIL-15) present in the culture supernatant expressed by oHSV2-mIL-15CherryFP was able to enhance the killing of CT26-GFP tumor cells by T cells. In addition, the intratumoral injection of oHSV2-mIL-15CherryFP inhibited tumor growth in the CT26-iRFP and BGC823-iRFP model. These results indicate that the use of oncolytic herpes simplex virus expressing IL-15 may be a potential therapeutic strategy in tumor immunotherapy.