In 2005, we initiated a clinical trial that examined the efficacy of the oncolytic virus HF10 to treat pancreatic cancer. Pancreatic cancer continues to have a high mortality rate, despite multimodal treatments for patients, and new therapeutic methods are greatly needed. The current mainstream methods for cancer treatment include biological therapeutics such as trastuzumab (Herceptin) for breast cancer or erlotinib (Tarceva) for non-small cell lung cancer. Oncolytic virus therapy is a new and promising treatment strategy for cancer. Oncolytic viruses are novel biological therapeutics for advanced cancer that appear to have a wide spectrum of anticancer activity with minimal human toxicity. To examine the efficacy of oncolytic virus therapy for pancreatic cancer, we initiated pilot studies by injecting six patients with non-resectable pancreatic cancer with three doses of HF10. All patients were monitored for 30 days for local and systemic adverse effects and were not administered any other therapeutics during this period. There were no adverse side-effects, and we observed some therapeutic potential based on tumor marker levels, survival, pathological findings and diagnostic radiography. The tumors were classified as stable disease in three patients, partial response in one patient and progressive disease in two patients.
Herpes simplex virus (HSV) was originally used as an oncolytic virus therapy between 1997 and 1999 when two different research groups used G2071, 2 and HSV17163, 4 to treat recurrent malignant glioma. These two groups performed phase I dose-escalation safety trials. In the clinical trial for brain tumors, the initial HSV-1 mutants were safe and feasible and showed some efficacy. NV1020 is also an important herpes oncolytic virus that can be specifically used for intravascular injections. A dose-escalation study in 2006 showed that NV1020 could be safely and feasibly injected into the hepatic artery to treat colon liver metastases,5 and a study in 2009 reported some efficacy with NV1020.6 However, these HSV mutants are artificially and genetically modified viruses, and some have a weak replication capacity and are easily cleared by the host immune system. In contrast to artificially modified HSV mutants, HF10 is a naturally mutated virus that was derived from the parent virus strain HF, which forms syncytia, that is, fused cells. The replication capacity of HF10 is comparable to or slightly higher than that of the wild-type HSV-1 in most types of transformed cells. The genetic character of HF10 can be confirmed by detecting deletions of 3832, 2295 and 6027 bp in the both ends of L region compared with the reference strain, HSV-1 17 sequence. In addition, UL43, 49.5, 55, 56 and latency-associated transcript are functionally inactivated as previously described.7 At the lethal dose, the toxicity of HF10 in mice is 104 times lower than that of the wild-type virus, but the virus still exhibits active therapeutic effects in cancer cell lines.8
Pancreatic cancer is difficult to cure and is the fifth largest cause of cancer deaths in Japan.9 Therefore, we greatly need new therapeutic methods to treat pancreatic cancer and put more emphasis on basic science and translational research. In our facility at the Nagoya University School of Medicine, clinical trials for HF10 were performed on three patients with recurrent head and neck cancer (Department of Oto-Rhino-Laryngology),10 six patients with recurrent breast cancer and six patients with non-resectable pancreatic cancer (Department of Surgery II).11, 12 Although we briefly described this trial in a review article,13 this is the first clinical report of six pancreatic cancer patients that were administered HF10 as an anticancer therapy. In 2003, a clinical trial for breast cancer was initiated in which patients received one injection of 1 × 104 p.f.u. followed by a gradual increase to three injections of 1 × 105 p.f.u.; two of the six tumors had good histological response, that is, grades II and III that means 60 and 100% cancer cell death. After 10 days of injection, the tumor diameters had decreased by over 30%, when examined by ultrasonography. Pathological analyses revealed virus inclusion bodies in the specimen that were resected after 2 weeks of virus injection.12 In addition, tests performed at the department of Oto-Rhino-Laryngology revealed highly concentrated CD4+ and CD8+ cell clusters in the tumor. Recently, it was determined that part of the tumor-killing effects of oncolytic virus therapy depends on the host immune response.10 Our clinical trial data showing that lymphocytes and CD4− and CD8+ cells infiltrate the tumor further support this hypothesis. Virus infection of the tumor stimulates host immune responses, and large numbers of antigen-presenting cells may traffic to the tumors in which they more efficiently process and present tumor antigens.
We started a dose-escalation study with an initial dose of 1 × 104 p.f.u. for breast cancer patients and 1 × 104 p.f.u. × 3 for head and neck cancer patients, and then gradually increased the doses and treatment times for the breast cancer patients until 5 × 105 p.f.u. On the basis of the data from the clinical trials for breast cancer and head and neck cancer, we designed a clinical trial to examine HF10 as a therapy to treat pancreatic cancer. At the beginning of the clinical trial for pancreatic cancer, the patients were injected with 1 × 105 p.f.u. for three consecutive days (once during the operation and twice after operation), after which the dose was gradually escalated to 1 × 106 p.f.u. We collected data on the HF10 safety and feasibility from six pancreatic cancer patients. We examined both the adverse and therapeutic effects 30 days after virus injection, whereas the patients were not administered any other therapeutics. We also examined lymphocyte infiltration induced by virus infection. Here, we present these data from this HF10 clinical trial for pancreatic cancer.
Materials and methods
All six patients were men, aged 52–76 years, who were positive for serum HSV antibodies, for safety reasons, and diagnosed with pancreatic cancer by preoperative radiography and intraoperative biopsy specimens. At the time of surgery, all of the patients were classified as having non-resectable pancreatic cancer caused by liver metastases, a local severe invasion of the main artery, or invasion of the lymph nodes around the aorta. We selected patients with resectable tumors that were preoperatively diagnosed by radiography, but were unfortunately classified as non-resectable at the time of the operation for the above-mentioned reasons. When we classified a tumor as non-resectable at the time of the operation, we performed a biopsy to make a final pathological diagnosis of pancreatic cancer. The profiles of the patients are summarized in Table 1. Autopsies were performed for all patients except patient 6 because of the request made by the family.
In this study, we performed a preliminary investigation of the toxicity and potential efficacy in six patients with pancreatic cancer to assess the feasibility of HF10 as a treatment for human cancers. In contrast to our former clinical trial on recurrent breast cancer,12 the present clinical trial on pancreatic cancer required that we inject the therapeutic virus into the organ during the laparotomy or with computed tomography (CT)-guided injection, although there is a possibility of venous injections with in vivo studies.14 Therefore, we chose to inject the virus during the laparotomy when the cancer was classified as non-resectable. HF10 virus was diluted to 1 × 106 p.f.u. 2.0 ml−1 and then directly injected at multiple locations into the pancreatic cancer in the operation room. Specifically, 0.5 ml of the HF10 suspension was injected into four tumor locations with a total dose of 1 × 106 p.f.u. 2.0 ml−1. We placed an epidural anesthesia catheter in the center of the tumor and fixed it by ligation so the catheter could be used for subsequent HF10 injections over the next 2 days (Figure 1). One end of the catheter was located in the center of the tumor, and the catheter passed through the abdominal wall and outside of the body. HF10 was injected into the tumor from the outside of the body using this catheter 2–3 days after the operation. In addition, 1.0 ml saline was slowly flushed into catheter after the virus injection to avoid any loss of the viral inoculum within the catheter. After three daily virus injections for three consecutive days, no other therapeutic method was used for the next 30 days. We estimated the safety and feasibility of HF10 at the end of this 30-day observation period.
All patients were monitored for local heat and redness. In addition, the following parameters were measured: complete blood count, HSV immunoglobulin (Ig) G, IgM, HSV DNA shedding, natural killer cells, interleukin-12, and interferon-α in the blood, HSV plaque forming units (p.f.u.) in the drain tube, and CT, magnetic resonance imaging and positron emission tomography scans (Table 1). After a 30-day period when the patients did not received any other therapeutics, the patients were administered standard chemotherapy (such as gemcitabine or/and TS1). All tumor and organ specimens were obtained at the autopsies after the patients died. All patients provided written informed consent. This study was approved by the Local Ethics Committee and the Institutional Review Board of our hospital.
Therapeutic response assessment
Evaluation of safety and efficacy
Tumor markers and survival time: the clinical trial was well tolerated by all six pancreatic cancer patients. There were no adverse effects, and we observed clinical efficacy in four of the six patients. The tumors were classified as stable disease or partial response in four patients and as progressive disease in two patients according to the CHOI criteria (modified RECIST criteria).15 The level of the serological tumor marker, CA19-9, correlated with survival time. During hospitalization, CA19-9 levels decreased in patients 1, 3 and 5, and patients 1, 3, 5 and 6 had longer survival than patients who receive an ordinary bypass operation (such as a cholangiojejunostomy or/and gastrojejunostomy) for non-resectable pancreatic cancer with chemotherapy (such as gemcitabine or/and TS1) (Table 1).
Blood tests: local and systemic adverse events, including the toxicity of the HF10 injections, were examined by blood tests (complete blood count, HSV IgG and HSV DNA shedding, natural killer cells, interleukin-12, interferon-α and so on), body temperature and blood pressure after the injections (Table 1); however, no toxicities or adverse effects were observed. Although HSV IgG, IgM, interleukin-12 and interferon-α levels did not change, natural killer cells tended to increase after the virus injections (data not shown). During the 30-day hospitalization period, the CA19-9 levels decreased in patients 1, 3 and 5 (Figure 2). HSV DNA shedding into blood was not detected by PCR on post-operative days 1, 3, 7, 14 and 28 (Table 1). The presence of HSV DNA in blood samples was examined using a fully-validated PCR assay for HSV-1 DNA. The PCR analysis was conducted at SRL Medisearch (Tokyo, Japan), whose main service is laboratory testing for clinical trials. The assay used SRL PCR kits with a primer set (forward: 5′-AGATGGCGAGCCACATCTC-3′, reverse: 5′-CTCCGGATACGGTATCGTC-3′) specific for the HSV-1 DNA polymerase domain (UL30) with 90 s each at 50, 65 and 94 °C for annealing. The detection limit of the kit was approximately 500–1000 copies per Ml.
HSV shedding in the drain from the abdominal cavity: we also monitored HSV shedding in the drain from the abdominal cavity. The number of virus plaques was determined in six-well plates with diluted samples. No HSV-1 was detected in any plates with samples obtained on post-operative days 1, 2, 3, 7, 14 and 28.
Histopathology: all specimens were acquired at the autopsies. A scar was found at the site of virus injection, in which fibroblasts had replaced tumor cells. This scar differed from that caused by ordinary chemotherapy or radiation because it was specific to the area of melting and adhesion and contained small-segmented nuclei and inclusion bodies caused by viral replication. These findings were similar to that observed after HF10 infection in breast cancer patients12 (Figure 3a).
Immunochemical staining for HSV antigen: in addition, immunochemical staining using an anti-HSV antibody (rabbit polyclonal antibody, Diagnostic Biosystems (Pleasanton, CA)) indicated that the virus was still present in several specimens, even after a significant amount of time had passed since the virus injections. In particular, patient 3 had cells that were positive for the viral antigen over 318 days after injection (Figure 3b).
Immunochemical staining for CD4+ and CD8+ cells and macrophages: we examined the infiltration of CD4+ and CD8+ cells into the tumor site by immunostaining (mouse monoclonal antibody, Nichirei, Tokyo, Japan). The HF10-injected tumors had a much greater infiltration of CD8+ cells than the tumor specimens that were resected by an ordinary operation and did not receive HF10 injections with statistically significant differences in 10 random high-power fields (P=0.002). There was a greater number of infiltrating CD4+ cells in the treated specimens than in the control specimens, but there were no statistically significant differences in 10 random high-power fields (P=0.08). (Figures 4a and b). Antigen-presenting cells and macrophages were also examined by immunostaining. Macrophages had infiltrated into the tumor site to a greater extent than in the control tissue (ordinary resected specimen) with statistically significant differences in 10 random high-power fields (P=0.0002) (Figure 4c).
Evaluation of radiography (CT, magnetic resonance imaging and positron emission tomography): the tumors in patients 1 and 4 were classified as progressive disease, those in patients 2, 3 and 6 as stable disease and that in patient 5 as partial response according to the CHOI criteria (modified RECIST criteria).15 The CA19-9 levels in patient 5 decreased dramatically. CT, magnetic resonance imaging and positron emission tomography revealed over a 30% reduction in tumor size, and positron emission tomography revealed that the cell activity area (red spot area) had decreased in size more significantly than CT or magnetic resonance imaging. Pancreatic cancer was diagnosed in patient 6 on the basis of the biopsy results, and this patient was CA19-9-negative and DUPAN-2-positive. In patient 6, the tumor size observed by radiography did not change for 80 days after the virus injections, and this patient did not receive any other treatments except for HF10 because of low food intake caused by tumor after the virus injections (Figure 5).
Compared with other oncolytic viruses, HSV-1 has special characteristics and advantages for treating cancer.16, 17, 18 HSV-1 can infect various tumor cell types, and total cell killing can be achieved with a relatively low multiplicity of infection. In addition, circulating anti-HSV antibodies do not affect the cell-to-cell spread of the virus. The genome of HSV-1 is large, 150 kbp, and contains many non-essential genes that can be mutated or replaced with large transgenes.19 Anti-herpes virus drugs such as acyclovir and ganciclovir are available and can be used to control adverse effects.
HF10 is a replication competent, naturally occurring HSV-1 mutant that can replicate and spread more efficiently than wild-type HSV-1 strains in most types of cancer cells.
We conducted a clinical trial in patients positive for serum HSV antibodies to assess the safety of HF10. Although circulating HSV antibodies in the blood stream restrict virus activity, they do not affect cell-to-cell infection in tumors. Our previous data indicated that HSV-1 is completely inactivated after incubating with positive human serum at 37 °C in a water bath for 1 h.14 Even if we detect HF10-associated adverse effects, we can use anti-HSV viral drugs to control these side-effects. Fortunately, however, there were no adverse effects in the 6 patients with non-resectable advanced pancreatic cancer who received three HF10 injections. Previous HF10 clinical trials were performed in six breast cancer patients12 and three head and neck cancer patients10 and to date these patients have shown no significant adverse effects, except for a low-grade fever in the head and neck cancer patients. In addition, there were no indications that the six pancreatic cancer patients were shedding HSV in their blood and body fluids. We examined HSV DNA shedding in the blood by PCR and quantified the number of HSV infectious particles that were discharged from the abdominal drain tube by determining the p.f.u. We believe that we have not yet reached the maximum dose of HF10 in this clinical trial and that the dose can possibly be increased to over 1 × 106 p.f.u.
An examination of the blood revealed that NK cells increased after virus injection. CD4+ and CD8+ cells and macrophages infiltrated the tumor. These findings suggest that HF10 infection stimulates the host immune system. Multiple studies have suggested that there is an immune response to viral antigens presented on the surface of tumor cells.20, 21, 22 Corticosteroid administration did not inhibit oncolytic virus replication, but suppressed cytotoxic T lymphocytes-mediated immune responses and tumor regression effects.23 Antitumor immune responses could be stimulated by HF10 infection as large amount of cytokines such as interferon α, β and interleukin-12 were induced on HF10 inoculation. In patient 3, viral antigen was detected over 318 days after injection. The virus appeared to persist for a prolonged period of time, and thus might continue to induce antitumor effects. It is possible that the immune response will inhibit systemic tumor metastases.
Our clinical data from six patients indicated that HF10 is a safe and feasible treatment with some therapeutic potential. Although patients with non-resectable pancreatic cancer who receive a bypass operation have an average survival time of 180 days, patients 1, 3, 5 and 6 survived beyond this time. With respect to tumor size, the tumors in patients 1 and 4 were classified as progressive disease, those in patients 2, 3 and 6 as stable disease and that in patient 5 as partial response according to the CHOI criteria (modified RECIST criteria).15 The tumor size in patient 6 did not change for over 80 days after the virus injections, when observed by radiography, and the patient had not received any other treatment except for HF10 because of a reduced appetite. These patients survived longer than those who underwent an ordinary bypass (cholangiojejunostomy or gastrojejunostomy) for non-resectable pancreatic cancer.
We believe that HF10 can be used at higher doses than the dose administered in the current study. This clinical trial is a dose-escalation study in a small number of patients. In the future, we plan to conduct a clinical trial to determine the maximum tolerated dose and optimal number of doses. In addition, we intend to perform phase II studies, followed by phase III studies whether the phase II data are promising, and initiate phase I studies of combination therapies during the phase II studies. Combination therapy with an oncolytic virus and conventional chemotherapy has been reported to be a promising treatment strategy for advanced cancers.24, 25, 26 We plan to administer six injections of HF10 for non-resectable pancreatic cancers using an endoscopic ultrasound. The current mainstream methods for cancer treatment are novel biological therapeutics, and oncolytic viruses are one type of biological therapeutic that appear to have a wide spectrum of anticancer activity with minimal human toxicity. Because the clinical effects of oncolytic virus therapy are strongly related to the host immune system, we have examined the effects of HF10 injections in conjunction with another immune stimulus, such as Granulocyte-macrophage colony stimulating factor, to improve the efficacy of oncolytic virus therapy,27 We believe that further development of oncolytic virus therapy and HF10 will be a promising therapeutic method that should be examined in a robust clinical study.
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The Takeda Science Foundation 2008 Grant-Aid for Scientific Research in Japan.
The authors declare no conflict of interest.
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Nakao, A., Kasuya, H., Sahin, T. et al. A phase I dose-escalation clinical trial of intraoperative direct intratumoral injection of HF10 oncolytic virus in non-resectable patients with advanced pancreatic cancer. Cancer Gene Ther 18, 167–175 (2011). https://doi.org/10.1038/cgt.2010.65
- clinical trial
- pancreatic cancer
- HF10, herpes oncolytic virus
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