Oncolytic Herpes Simplex Virus Type Research Articles

An open-label, multicenter study investigating RP2 oncolytic immunotherapy in combination with second-line systemic atezolizumab combined with bevacizumab in patients with locally advanced unresectable or metastatic hepatocellular carcinoma.

TPS4191 Background: Despite advances in treatment for unresectable hepatocellular carcinoma (HCC), long-term survival rates remain poor. The combination of atezolizumab (Atezo) plus bevacizumab (Bev) is approved as frontline therapy for advanced HCC, but only a minority of patients (pts) respond and secondary resistance usually occurs within months. HCC has an immune-suppressed tumor microenvironment (TME), mediated by activated immune checkpoint signaling and angiogenesis pathways, which may contribute to therapeutic resistance. RP2 is an enhanced potency oncolytic herpes simplex virus type 1 (HSV-1) that expresses the fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R–), GM-CSF, and an anti–CTLA-4 antibody-like molecule. The direct oncolytic effect coupled with immune stimulation by RP2 in the TME is intended to provide systemic antitumor activity and synergize with anti–PD-1/PD-L1 agents, such as Atezo. Preclinical data have demonstrated improved distribution of oncolytic HSV within tumors in combination with Bev, supporting the clinical combination of RP2 with Bev. This study will evaluate the safety and efficacy of RP2 combined with Atezo plus Bev as second-line systemic therapy for unresectable and advanced HCC (NCT05733598). Methods: This is an open-label, single arm, phase 2 trial. Up to 30 pts will be enrolled and receive RP2 in combination with Atezo plus Bev. Key inclusion criteria include advanced unresectable HCC with ≥1 measurable tumor of ≥1 cm in longest diameter, Child-Pugh class A, an Eastern Cooperative Oncology Group performance status of 0 to 1, and progression on 1 prior systemic treatment, which must have included a PD-1/PD-L1–directed agent. Key exclusion criteria include untreated/incompletely treated esophageal and/or gastric varices with bleeding or at high risk for bleeding and macroscopic invasion of the tumor into any major blood vessel(s) and/or main bile ducts. Pts will receive intratumoral RP2 Q2W for 4 doses, then Q3W for up to 4 doses. Bev will be given at 10 mg/kg Q2W starting with the first dose of RP2 then at 15 mg/kg Q3W starting with cycle 4; Atezo will be given at 840 mg Q2W for cycles 2 and 3, then at 1200 mg Q3W starting with cycle 4. Pts will receive treatment until confirmed progressive disease, loss of clinical benefit, or unacceptable toxicity. The primary endpoint is overall response rate (ORR), defined as the proportion of pts achieving a best overall response of complete response or partial response per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 as modified for this study. Secondary endpoints are safety, ORR using HCC-modified RECIST, duration of response, complete response rate, and progression-free survival. Clinical trial information: NCT05733598 .

VP5 protein of oncolytic herpes simplex virus type 2 induces apoptosis in A549 cells through TP53I3 protein

Oncolytic virotherapy stands out as a burgeoning and promising therapeutic paradigm, harnessing the intrinsic cytotoxicity of oncolytic viruses for selective replication and dissemination within tumors. The primary mode of action revolves around the direct eradication of tumor cells. In our previous investigations, we formulated an oncolytic herpes simplex virus type 2 (OH2) and substantiated its anti-tumor efficacy both in vivo and in vitro. Subsequently, we embarked on a phase I/II clinical trial in China (NMPA, 2018L02743) and the USA (FDA, IND 27137) to assess OH2's safety, biodistribution, and anti-tumor activity as a standalone agent in patients with advanced solid tumors. In this investigation, our primary focus was to comprehend the influence of the major capsid protein VP5 of OH2 on its efficacy as an antitumor agent. Our findings underscore that the VP5 protein significantly amplifies OH2's oncolytic impact on A549 cells. Additionally, we observed that VP5 actively promotes the induction of apoptosis in A549 cells, both in vivo and in vitro. Through comprehensive transcriptional sequencing, we further authenticated that the VP5 protein triggers apoptosis-related signaling pathways and Gene Ontology (GO) terms in A549 cells. Moreover, we scrutinized differentially expressed genes in the p53-dependent apoptosis pathway and conducted meticulous in vitro validation of these genes. Subsequently, we delved deeper into unraveling the functional significance of the TP53I3 gene and conclusively affirmed that the VP5 protein induces apoptosis in A549 cells through the TP53I3 gene. These revelations illuminate the underlying mechanisms of OH2's antitumor activity and underscore the pivotal role played by the VP5 protein. The outcomes of our study harbor promising implications for the formulation of effective oncolytic virotherapy strategies in cancer treatment.

Replication and expression of oncolytic herpes simplex virus type Ⅱ in tumors

This study aimed to measure the duration and replication level of oncolytic herpes simplex virus type 2 (oHSV2) at the tumor injection site in BALB/c mice. Additionally, the expression level of human granulocyte macrophage colony-stimulating factor (hGM-CSF) and HSV-2 antibody in the serum was also measured. High and low doses of oHSV2-Fluc (firefly luciferin, Fluc) were injected into the mice's tumors to track the change and duration of fluorescence expression. The copy number of oHSV2 gene in tumor tissues was determined using quantitative real-time polymerase chain reaction (qPCR). Enzyme linked immunosorbent assay (ELISA) was used to detect the expression of hGM-CSF and HSV-2 antibody in the serum. The tumor volume in the high-dose group was significantly lower than that in the control group (P < 0.01). Intratumor injection of oHSV2-Fluc showed that the carried Fluc could continue to express in the tumor, with fluorescence still detectable at day 11 and declining to undetectable level by day 18. The mRNA expression of oHSV2 was detected in tumor tissues of both high and low dose groups on day 9 using qPCR. ELISA results showed that the levels of HSV2 antibody and hGM-CSF in both high and low dose groups were significantly increased compared to the control group (P < 0.05) after collecting orbital blood. These findings suggest that oHSV2 can replicate in the tumor and sustainably express exogenous factors, thus effectively targeting and killing the tumor. Furthermore, intratumoral injection of oHSV2 resulted in higher levels of hGM-CSF and HSV-2 antibodies found in the mice's serum.

Development of a novel, high-efficacy oncolytic herpes simplex virus type 1 platform equipped with two distinct retargeting modalities

To retarget oncolytic herpes simplex virus (oHSV) to cancer-specific antigens, we designed a novel, double-retargeted oHSV platform that uses single-chain antibodies (scFv) incorporated into both glycoprotein H (gH) and a bispecific adapter expressed from the viral genome to mediate infection predominantly via tumor-associated antigens. Successful retargeting was achieved using a nectin-1-detargeted HSV that remains capable of interacting with HVEM, the second canonical HSV entry receptor, and is therefore recognized by the adapter consisting of the virus-binding N-terminal 82 residues of HVEM fused to the target-specific scFv. We tested both an EpCAM- and a HER2-specific scFv separately and together to target cells expressing one, the other, or both receptors. Our results show not only dose-dependent, target receptor-specific infection in vitro, but also enhanced virus spread compared to single-retargeted virus. In addition, we observed effective infection and spreading of the EpCAM double-retargeted virus in vivo. Remarkably, a single intravenous dose of the EpCAM-specific virus eliminated all detectable tumors in a subcutaneous xenograft model, and the same intravenous dose appeared harmless in immunocompetent FVB/N mice. Our findings suggest that our double-retargeted oHSV platform can provide a potent and versatile, systemically deliverable class of anti-cancer therapeutics that specifically target cancer cells while ensuring safety.

An open-label clinical trial of RP2 and RP3 oncolytic immunotherapy in combination with atezolizumab plus bevacizumab for the treatment of patients with advanced colorectal carcinoma.

TPS228 Background: Colorectal cancer (CRC) is the third most frequently diagnosed cancer and the second leading cause of cancer-related mortality worldwide. PD-1/PD-L1 inhibition, in combination with other modalities, has demonstrated significant benefit in patients (pts) with microsatellite instability-high or mismatch repair–deficient CRC. However, these agents have limited, if any, clinical benefit in pts with microsatellite stable (MSS) or mismatch repair–proficient (pMMR) CRC. RP2 is an enhanced potency oncolytic herpes simplex virus type 1 which expresses the fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R–), granulocyte-macrophage colony-stimulating factor (GM-CSF), and an anti–CTLA-4 antibody-like molecule; RP3 additionally expresses 4-1BB and CD40 activating ligands but does not express GM-CSF. Both agents have demonstrated preliminary safety and antitumor activity in pts with solid tumors. This study will evaluate the safety and activity of RP2 and RP3 in combination with atezolizumab (Atezo) plus bevacizumab (Bev) in pts with advanced MSS/pMMR CRC (NCT05733611). Methods: Pts with a histologic diagnosis of unresectable and/or metastatic CRC, with documented MSS or pMMR status, and previously treated with up to 3 standard-of-care systemic regimens will be enrolled in the RP2 + Atezo + Bev or RP3 + Atezo + Bev treatment groups (30 pts per group). Further key inclusion criteria include Eastern Cooperative Oncology Group performance status 0 to 1 and adequate hepatic, renal, and hematologic function. RP2/RP3 will be injected into tumors by direct or image-guided injection. Pts will receive 8 total doses of up to 10 mL of RP2 or RP3, with a first dose concentration of 1 × 106 plaque-forming units (PFU)/mL, followed by 3 doses of 1 × 107 PFU/mL every 2 weeks, and then 4 doses of 1 × 107 PFU/mL every 3 weeks. Pts may receive a second course of up to 8 injections of RP2/RP3 if study criteria are met. Bev will be administered starting on week 1; Atezo will be administered starting week 7. The primary endpoint is objective response rate; secondary endpoints are safety, overall survival, progression-free survival, duration of response, and complete response rate. Antitumor activity will be evaluated using Response Evaluation Criteria in Solid Tumors version 1.1 as modified for this study. Safety will be assessed by physical examination, clinical laboratory evaluations, vital signs, and monitoring for adverse events (AEs; including serious AEs). Clinical trial information: NCT05733611 .

Prophylactic Vaccination and Intratumoral Boost with HER2-Expressing Oncolytic Herpes Simplex Virus Induces Robust and Persistent Immune Response against HER2-Positive Tumor Cells.

The development of effective cancer vaccines remains a significant challenge due to immune tolerance and limited clinical benefits. Oncolytic herpes simplex virus type 1 (oHSV-1) has shown promise as a cancer therapy, but efficacy is often limited in advanced cancers. In this study, we constructed and characterized a novel oHSV-1 virus (VG22401) expressing the human epidermal growth factor receptor 2 (HER2), a transmembrane glycoprotein overexpressed in many carcinomas. VG22401 exhibited efficient replication and HER2 payload expression in both human and mouse colorectal cancer cells. Mice immunized with VG22401 showed significant binding of serum anti-HER2 antibodies to HER2-expressing tumor cells, inducing antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Furthermore, mice primed with VG22401 and intratumorally boosted with the same virus showed enhanced antitumor efficacy in a bilateral syngeneic HER2(+) tumor model, compared to HER2-null backbone virus. This effect was accompanied by the induction of anti-HER2 T cell responses. Our findings suggest that peripheral priming with HER2-expressing oHSV-1 followed by an intratumoral boost with the same virus can significantly enhance antitumor immunity and efficacy, presenting a promising strategy for cancer immunotherapy.

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).

Neoadjuvant use of oncolytic herpes virus G47Δ prevents local recurrence after insufficient resection in tongue cancer models

A complete resection of tongue cancer is often difficult. We investigate the usefulness of administering G47Δ (teserpaturev), a triple-mutated oncolytic herpes simplex virus type 1, prior to resection. G47Δ exhibits good cytopathic effects and replication capabilities in all head and neck cancer cell lines tested. In an orthotopic SCCVII tongue cancer model of C3H/He mice, an intratumoral inoculation with G47Δ significantly prolongs the survival. Further, mice with orthotopic tongue cancer received neoadjuvant G47Δ (or mock) therapy with or without "hemilateral" resection, the maximum extent avoiding surgical deaths. Neoadjuvant G47Δ and resection led to 10/10 survival (120days), whereas the survivals for G47Δ alone and resection alone were 6/10 and 5/10, respectively: all control animals died by day 11. Furthermore, 100% survival was achieved with neoadjuvant G47Δ therapy even when the resection area was narrowed to "partial," providing insufficient resection margins, whereas hemilateral resection alone caused death by local recurrence in half of the animals. G47Δ therapy caused increased number of tumor-infiltrating CD8+ and CD4+ cells, increased F4/80+ cells within the residual tongues, and increased expression of immune-related genes in and around the tumor. These results imply that neoadjuvant use of G47Δ is useful for preventing local recurrence after tongue cancer surgery.

The Oncolytic herpes simplex virus type-1 (HSV-1) vaccine strain VC2 causes intratumor infiltration of functionally active T cells and inhibition of tumor metastasis and pro-tumor genes VEGF and PDL1 expression in the 4T1/Balb/c mouse model of stage four breast cancer.

Introduction: Oncolytic viruses (OVs) provide new modalities for cancer therapy either alone or in combination with synergistic immunotherapies and/or chemotherapeutics. Engineered Herpes Simplex Virus Type-1 (HSV-1) has shown strong promise for the treatment of various cancers in experimental animal models as well as in human patients, with some virus strains licensed to treat human melanoma and gliomas. In the present study we evaluated the efficacy of mutant HSV-1 (VC2) in a late stage, highly metastatic 4T1 murine syngeneic. Method: VC2 was constructed VC2 using double red recombination technology. For in-vivo efficacy we utilized a late stage 4T1 syngeneic and immunocompetent BALB/cJ mouse model breast cancer model which exhibits efficient metastasis to the lung and other organs. Results: VC2 replicated efficiently in 4T1 cells and in cell culture, achieving titers similar to those in African monkey kidney (Vero) cells. Intra-tumor treatment with VC2 did not appreciably reduce average primary tumor sizes but a significant reduction of lung metastasis was noted in mice treated intratumorally with VC2, but not with ultraviolet-inactivated VC2. This reduction of metastasis was associated with increased T cell infiltration comprised of CD4+ and CD4+CD8+ double-positive T cells. Characterization of purified tumor infiltrating T cells revealed a significant improvement in their proliferation ability compared to controls. In addition, significant T cell infiltration was observed in the metastatic nodules associated with reduction of pro-tumor PD-L1 and VEGF gene transcription. Conclusion: These results show that VC2 therapy can improve anti-tumor response associated with a better control of tumor metastasis. improve T cell responses and reduce pro-tumor biomarker gene transcription. VC2 holds promise for further development as an oncolytic and immunotherapeutic approach to treat breast and other cancers.

Preliminary safety and efficacy results from an open-label, multicenter, phase 1 study of RP2 as a single agent and in combination with nivolumab in a cohort of patients with uveal melanoma.

9527 Background: Uveal melanoma, although rare, represents the most common primary intraocular tumor in adults and is associated with high risk of liver metastases. Effective treatments are limited as uveal melanoma is an immunologically cold tumor that does not respond well to immunotherapy. RP2 is an enhanced-potency oncolytic herpes simplex virus type 1 expressing human granulocyte-macrophage colony-stimulating factor, fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R−), and an anti–CTLA-4 antibody-like molecule. Here, we present updated safety and efficacy data of RP2 monotherapy and RP2 + nivolumab (nivo; anti–PD-1) in patients (pts) with uveal melanoma. Methods: Pts ≥18 years old with histologically or cytologically confirmed advanced or metastatic non-neurological solid tumors (including uveal melanoma) who progressed on or could not tolerate standard therapy were included; pts had ≥1 measurable and injectable tumor (≥1 cm). After determination of the recommended phase 2 dose of RP2 (concentration of 106 plaque-forming units [PFU]/mL intratumorally [IT] once followed by up to 7 additional IT doses at 107 PFU/mL; [≤10 mL total/treatment day with amount per lesion determined by tumor diameter]), pts received RP2 monotherapy every two weeks (Q2W) or RP2 Q2W + nivo (NCT04336241). Responses were assessed using modified Response Evaluation Criteria in Solid Tumors version 1.1. Results: As of December 30, 2022, 17 pts with uveal melanoma were enrolled (RP2 monotherapy, n = 3; RP2 + nivo, n = 14). The majority of pts received both anti–PD-1 and anti–CTLA-4 therapy (12/17, 70.6%) and 17.6% received ≥3 prior lines of therapy. The overall objective response rate for the 14 pts with sufficient follow up for analysis was 28.6% [4/14] (all partial responses [PRs]; RP2 monotherapy, 1/3; RP2 + nivo, 3/11). The disease control rate (complete response + PR + stable disease [SD]) was 57.1% (8/14; 4 pts with SD in RP2 + nivo cohort). The median (range) duration of response at the data cut-off was 5.8 (1.7–14.7) months. The most common overall Grade 1–2 treatment-related adverse events (TRAEs; ≥20%) were pyrexia, chills, fatigue, and hypotension. The only Grade 3 TRAE occurring in &gt; 1 pt was hypotension (2 pts receiving RP2 + nivo); no Grade 4–5 TRAEs were observed. Conclusions: Preliminary RP2 monotherapy and RP2 + nivo data demonstrated a favorable safety profile and meaningful antitumor activity in pts with metastatic uveal melanoma, an immunologically cold tumor with few effective treatment options. These data continue to support the hypothesis that IT oncolytic immunotherapy expressing anti–CTLA-4 in combination with anti–PD-1 may provide clinically meaningful benefit in pts with hard-to-treat/unresponsive tumors. Clinical trial information: NCT04336241 .

An open-label clinical trial of RP2 and RP3 oncolytic immunotherapy in combination with atezolizumab and bevacizumab for the treatment of patients with advanced colorectal carcinoma.

TPS3628 Background: Colorectal cancer (CRC) is the third most frequently diagnosed cancer and the second leading cause of cancer-related mortality worldwide. PD-1/PD-L1 inhibition, in combination with other modalities, has demonstrated significant benefit in patients (pts) with microsatellite instability-high or mismatch repair deficient CRC. However, these agents have limited, if any, clinical benefit in pts with microsatellite stable (MSS) or mismatch repair proficient (pMMR) CRC. RP2 is an enhanced potency oncolytic herpes simplex virus type 1 which expresses the fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R–), granulocyte-macrophage colony-stimulating factor (GM-CSF), and an anti–CTLA-4 antibody-like molecule; RP3 additionally expresses 4-1BB and CD40 activating ligands, but does not express GM-CSF. Both agents have demonstrated preliminary safety and efficacy in pts with solid tumors. This study will evaluate the safety and efficacy of RP2 and RP3 in combination with atezolizumab (Atezo) and bevacizumab (Bev) in pts with advanced MSS and pMMR CRC. Methods: Pts with a histologic diagnosis of unresectable and/or metastatic CRC, with documented MSS or pMMR status, and previously treated with up to 3 standard-of-care systemic regimens will be enrolled in the RP2 + Atezo + Bev or RP3 + Atezo + Bev treatment groups (30 pts per group). Further key inclusion criteria include Eastern Cooperative Oncology Group performance status 0–1 and adequate hepatic, renal, and hematologic function. RP2/RP3 will be injected into tumors by direct (including via colonoscope) or image-guided injection. Pts will receive 8 total doses of up to 10 mL of RP2 or RP3, with a first dose concentration of 1 × 106 plaque-forming units (PFU)/mL, followed by 3 doses of 1 × 107 PFU/mL every 2 weeks, and then 4 doses of 1 × 107 PFU/mL every 3 weeks. Pts may receive a second course of up to 8 injections of RP2/RP3 if study criteria are met. Bev will be administered starting on day 1 (with first dose of RP2/RP3); Atezo will be administered starting week 7 on the same days as RP2/RP3. The primary endpoint is objective response rate; secondary endpoints are safety, overall survival, progression-free survival, duration of response, and complete response rate. Antitumor activity will be evaluated using Response Evaluation Criteria in Solid Tumors version 1.1 as modified for this study. Safety will be assessed by physical examination, clinical laboratory evaluations, vital signs, and monitoring for adverse events (AEs; including serious AEs). Clinical trial information: NCT05733611 .

Human Monocytes Are Suitable Carriers for the Delivery of Oncolytic Herpes Simplex Virus Type 1 In Vitro and in a Chicken Embryo Chorioallantoic Membrane Model of Cancer.

Oncolytic viruses (OVs) are promising therapeutics for tumors with a poor prognosis. An OV based on herpes simplex virus type 1 (oHSV-1), talimogene laherparepvec (T-VEC), has been recently approved by the Food and Drug Administration (FDA) and by the European Medicines Agency (EMA) for the treatment of unresectable melanoma. T-VEC, like most OVs, is administered via intratumoral injection, underlining the unresolved problem of the systemic delivery of the oncolytic agent for the treatment of metastases and deep-seated tumors. To address this drawback, cells with a tropism for tumors can be loaded ex vivo with OVs and used as carriers for systemic oncolytic virotherapy. Here, we evaluated human monocytes as carrier cells for a prototype oHSV-1 with a similar genetic backbone as T-VEC. Many tumors specifically recruit monocytes from the bloodstream, and autologous monocytes can be obtained from peripheral blood. We demonstrate here that oHSV-1-loaded primary human monocytes migrated in vitro towards epithelial cancer cells of different origin. Moreover, human monocytic leukemia cells selectively delivered oHSV-1 to human head-and-neck xenograft tumors grown on the chorioallantoic membrane (CAM) of fertilized chicken eggs after intravascular injection. Thus, our work shows that monocytes are promising carriers for the delivery of oHSV-1s in vivo, deserving further investigation in animal models.

Combination of novel oncolytic herpesvirus with paclitaxel as an efficient strategy for breast cancer therapy.

New strategies are needed to improve the treatment of patients with breast cancer (BC). Oncolytic virotherapy is a promising new tool for cancer treatment but still has a limited overall durable antitumor response. A novel replicable recombinant oncolytic herpes simplex virus type 1 called VG161 has been developed and has demonstrated antitumor effects in several cancers. Here, we explored the efficacy and the antitumor immune response of VG161 cotreatment with paclitaxel (PTX) which as a novel oncolytic viral immunotherapy for BC. The antitumor effect of VG161 and PTX was confirmed in a BC xenograft mouse model. The immunostimulatory pathways were tested by RNA-seq and the remodeling of tumor microenvironment was detected by Flow cytometry analysis or Immunohistochemistry. Pulmonary lesions were analyzed by the EMT6-Luc BC model. In this report, we demonstrate that VG161 can significantly represses BC growth and elicit a robust antitumor immune response in a mouse model. The effect is amplified when combined with PTX treatment. The antitumor effect is associated with the infiltration of lymphoid cells, including CD4+ T cells, CD8+ T cells, and NK cells (expressing TNF and IFN-γ), and myeloid cells, including macrophages, myeloid-derived suppressor cells, and dendritic cell cells. Additionally, VG161 cotreatment with PTX showed a significant reduction in BC lung metastasis, which may result from the enhanced CD4+ and CD8+ T cell-mediated responses. The combination of PTX and VG161 is effective for repressing BC growth by inducing proinflammatory changes in the tumor microenvironment and reducing BC pulmonary metastasis. These data will provide a new strategy and valuable insight for oncolytic virus therapy applications in primary solid or metastatic BC tumors.

An oncolytic herpes simplex virus type 1 strain expressing a single-chain variable region antibody fragment against PD-1 and a PI3K inhibitor synergize to elicit antitumor immunity in ovarian cancer

Due to recurrence and resistance to chemotherapy, the current standard therapeutics are not fully effective against ovarian cancer. Therefore, we aimed to find an effective approach to improve the prognosis and therapy of ovarian cancer. NG34ScFvPD-1 is a modified oncolytic herpes simplex virus NG34 strain that expresses a single-chain antibody against programmed cell death protein 1 (PD-1) (ScFvPD-1). We assessed its efficacy and its regulatory mechanism in a mouse model of ovarian cancer. Enzyme-linked immunosorbent assay and western blot techniques were used to measure protein expression. Oncolysis caused by NG34ScFvPD-1 was examined using cytotoxicity and replication assays. The mechanism by which NG34ScFvPD-1 regulates apoptosis of ovarian cancer cells in vitro was also evaluated. We assessed the antitumor immunity and therapeutic potency of NG34ScFvPD-1 in combination with a phosphoinositide 3-kinase (PI3K) inhibitor. We found that NG34ScFvPD-1-infected ovarian cancer cells expressed and secreted ScFvPD-1, which bound mouse PD-1. The insertion of the ScFvPD-1 sequence did not inhibit the oncolytic activity of NG34ScFvPD-1, which induced apoptosis of ovarian cancer cells via the caspase-dependent pathway in vitro and activated the PI3K/AKT signaling pathway. Synergy was observed between NG34ScFvPD-1 and a PI3K inhibitor, and the combination was able to suppress tumor development, to prolong survival, and to elicit potent antitumor immunity. Thus, inhibition of PI3K enhanced the potent antitumor immunity induced by NG34ScFvPD-1 against ovarian cancer.

Fusion peptide is superior to co-expressing subunits for arming oncolytic herpes virus with interleukin 12

BackgroundG47∆ is a triple-mutated oncolytic herpes simplex virus type 1 (HSV-1) recently approved as a new drug for malignant glioma in Japan. As the next-generation, we develop armed oncolytic HSV-1 using G47∆ as the backbone. Because oncolytic HSV-1 elicits specific antitumor immunity, interleukin 12 (IL-12) can function as an effective payload to enhance the efficacy.MethodsWe evaluate the optimal methods for expressing IL-12 as a payload for G47∆-based oncolytic HSV-1. Two new armed viruses are generated for evaluation by employing different methods to express IL-12: T-mfIL12 expresses murine IL-12 as a fusion peptide, with the genes of two subunits (p35 and p40) linked by bovine elastin motifs, and T-mIL12-IRES co-expresses the subunits, with the two genes separated by an internal ribosome entry site (IRES) sequence.ResultsT-mfIL12 is significantly more efficient in producing IL-12 than T-mIL12-IRES in all cell lines tested, whereas the expression methods do not affect the replication capabilities and cytopathic effects. In two syngeneic mouse subcutaneous tumor models of Neuro2a and TRAMP-C2, T-mfIL12 exhibits a significantly higher efficacy than T-mIL12-IRES when inoculated intratumorally. Furthermore, T-mfIL12 shows a significantly higher intratumoral expression of functional IL-12, causing stronger stimulation of specific antitumor immune responses than T-mIL12-IRES.ConclusionsThe results implicate that a fusion-type expression of IL-12 is a method superior to co-expression of separate subunits, due to higher production of functional IL-12 molecules. This study led to the creation of triple-mutated oncolytic HSV-1 armed with human IL-12 currently used in phase 1/2 trial for malignant melanoma.

Targeting carcinoembryonic antigen-expressing tumors using a novel transcriptional and translational dual-regulated oncolytic herpes simplex virus type 1

VG2025 is a recombinant oncolytic herpes simplex virus type 1 (HSV-1) that uses transcriptional and translational dual regulation (TTDR) of critical viral genes to enhance virus safety and promote tumor-specific virus replication without reducing virulence. The TTDR platform is based on transcriptional control of the essential HSV-1 immediate-early protein ICP27 using a tumor-specific carcinoembryonic antigen (CEA) promoter, coupled with translational control of the neurovirulence factor ICP34.5 using multiple microRNA (miR)-binding sites. VG2025 further incorporates IL-12 and the IL-15/IL-15 receptor alpha subunit complex to enhance the antitumor and immune stimulatory properties of oncolytic HSVs. The TTDR strategy was verified invitro and shown to be highly selective. Strong invivo antitumor efficacy was observed following both intratumoral and intravenous administration. Clear abscopal and immune memory effects were also evident, indicating a robust antitumor immune response. Gene expression profiling of treated tumors revealed increased immune cell infiltration and activation of multiple immune-signaling pathways when compared with the backbone virus. Absence of neurotoxicity was verified in mice and in rhesus monkeys. Taken together, the enhanced tumor clearance, excellent safety profile, and positive correlation between CEA levels and viral replication efficiency may provide an opportunity for using biomarker-based precision medicine in oncolytic virotherapy.

Overcoming resistance of stroma-rich pancreatic cancer with focal adhesion kinase inhibitor combined with G47Δ and immune checkpoint inhibitors

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease known for its dense tumor stroma. Focal adhesion kinase inhibitor (FAKi), a non-receptor type tyrosine kinase inhibitor, reduces the tumor stroma. G47Δ, a third-generation oncolytic herpes simplex virus type 1, destroys tumor cells selectively and induces antitumor immune responses. This study evaluates the efficacy of FAKi and G47Δ in PDAC models in combination with or without immune checkpoint inhibitors. G47Δ was effective in human PDAC cell lines invitro and in subcutaneous as well as orthotopic tumor models. Transgenic mouse-derived #146 cells were used to generate subcutaneous PDAC tumors with rich stroma in immunocompetent mice. In this #146 tumor model, the efficacy of FAKi was synergistically augmented when combined with G47Δ, which reflected not only a decreased stromal content but also a significant shifting of the tumor microenvironment toward immune stimulation. In transgenic autochthonous PKF mice, a rare model that develops stroma-rich PDAC with a 100% penetrance and resembles human PDAC in various aspects, the prolongation of survival compared with FAKi alone was achieved only when FAKi was combined with G47Δ and immune checkpoint inhibitors. The FAKi combination therapy may be useful to overcome the treatment resistance of stroma-rich PDAC.

Specific targeting of glioblastoma with an oncolytic virus expressing a cetuximab-CCL5 fusion protein via innate and adaptive immunity.

Chemokines such as C-C motif ligand 5 (CCL5) regulate immune cell trafficking in the tumor microenvironment (TME) and govern tumor development, making them promising targets for cancer therapy. However, short half-lives and toxic off-target effects limit their application. Oncolytic viruses (OVs) have become attractive therapeutic agents. Here, we generate an oncolytic herpes simplex virus type 1 (oHSV) expressing a secretable single-chain variable fragment of the epidermal growth factor receptor (EGFR) antibody cetuximab linked to CCL5 by an Fc knob-into-hole strategy that produces heterodimers (OV-Cmab-CCL5). OV-Cmab-CCL5 permits continuous production of CCL5 in the TME, as it is redirected to EGFR+ glioblastoma (GBM) tumor cells. OV-Cmab-CCL5 infection of GBM significantly enhances the migration and activation of natural killer cells, macrophages and T cells; inhibits tumor EGFR signaling; reduces tumor size; and prolongs survival of GBM-bearing mice. Collectively, our data demonstrate that OV-Cmab-CCL5 offers a promising approach to improve OV therapy for solid tumors.

VG161 activates systemic antitumor immunity in pancreatic cancer models as a novel oncolytic herpesvirus expressing multiple immunomodulatory transgenes.

The VG161 represents the first recombinant oncolytic herpes simplex virus type 1 carrying multiple synergistic antitumor immuno-modulating factors. Here, we report its antitumor mechanisms and thus provide firm theoretical foundation for the upcoming clinical application in pancreatic cancer. Generally, the VG161-mediated antitumor outcomes were analyzed by a collaboration of techniques, namely the single-cell sequencing, airflow-assisted desorption electrospray ionization-mass spectrometry imaging (AFADSI-MSI) and nanostring techniques. In vitro, the efficacy of VG161 together with immune checkpoint inhibitors (ICIs) has been successfully shown to grant a long-term antitumor effect by altering tumor immunity and remodeling tumor microenvironment (TME) metabolisms. Cellular functional pathways and cell subtypes detected from patient samples before and after the treatment had undergone distinctive changes including upregulated CD8+ Tand natural killer cells. More importantly, significant antitumor signals have emerged since the administration of VG161 injection. In conclusion, VG161 can systematically activate acquired and innate immunity in pancreatic models, as well as improve the tumor immune microenvironment, indicative of strong antitumor potential. The more robusting antitumor outcome for VG161 monotherapy or in combination with other therapies on pancreatic cancer is worth of being explored in further clinical trials.

Teserpaturev/G47Δ: First Approval.

Teserpaturev/G47Δ (Delytact®) is a third-generation (triple-mutated) recombinant oncolytic herpes simplex virus type 1 being developed by Daiichi Sankyo Co., Ltd. for the treatment of certain solid cancers. Teserpaturev/G47Δ has been approved for the treatment of malignant glioma in Japan and is currently in clinical development for the treatment of prostate cancer (phase II), malignant pleural mesothelioma (phase I) and recurrent olfactory neuroblastoma (phase I). This article summarizes the milestones in the development of teserpaturev/G47Δ leading to this first approval for the treatment of malignant glioma.