Intraprostatic distribution and long-term follow-up after AdV-tk immunotherapy as neoadjuvant to surgery in patients with prostate cancer

Clinical Efficacy and Safety of AdV-tk Gene Therapy for Patients with Cervical Squamous Intraepithelial Lesion: A Prospective Study

Cervical cancer is the fourth most common type of cancer for women in 2020, and many more women have cervical precancerous lesion-squamous intraepithelial lesion (SIL). Early treatment of cervical SIL to reverse or delay its progression is an important approach to reduce the incidence of cervical cancer. The efficacy and safety of adenovirus-based vectors expressing the thymidine kinase gene (AdV-tk) in the treatment of multiple types of cancers shows promise for its use in gynecology. We aim to provide relevant clinical efficacy and safety data after introducing AdV-tk for the treatment of cervical SIL for the first time through this prospective study. We conducted a maximum of 6 sessions to administer AdV-tk gene therapy to 23 patients (mean age: 35 years old) with cervical low-/high-grade SIL (LSIL/HSIL) who were enrolled from August 2015 to April 2018 and analyzed the clinical characteristics and follow-up outcomes (mean follow-up period: 7.3 months). The present study consisted of 17 patients (73.9%) with cervical HSIL and 6 patients with LSIL confirmed by colposcopy-directed biopsy. We observed an overall histological remission and regression rate of 87.0% (20/23, 95% confidence interval [95% CI]: 73.2-100, p < 0.001) after AdV-tk gene therapy. Eight patients (34.8%) were detected with human papillomavirus (HPV) 16/18 subtypes and 13 patients were found to be positive with at least one of the other 13 high-risk HPV (HR-HPV) subtypes, while 2 patients did not have any of the 15 HR-HPV subtypes. The overall clearance rate of HR-HPV was 76.2% (16/21, 95% CI: 58.0-94.4, p = 0.016) after AdV-tk gene therapy. For safety evaluation, no severe complications were reported in any of the 23 patients. The most commonly reported symptom was fever in 52.2% (12/23) of patients and all symptoms were fully resolved after symptomatic treatment. Our data indicate that AdV-tk gene therapy has high efficacy and safety in the treatment of cervical SIL among gynecological patients. Our findings provide clinical evidence on the potential promotion and application of AdV-tk in the treatment of cervical SIL, and potentially for cervical cancer, among gynecological patients.

Anticancer Activity of Measles-Mumps-Rubella MMR Vaccine Viruses against Glioblastoma

BACKGROUND

Oncolytic viruses (OVs) have been utilized since 1990s for targeted cancer treatment. Our study examined the Measles-Mumps-Rubella (MMR) vaccine's cancer-killing potency against Glioblastoma (GBM), a therapy-resistant, aggressive cancer type.

METHODOLOGY

We used GBM cell lines, primary GBM cells, and normal mice microglial cells, to assess the MMR vaccine's efficacy through cell viability, cell cycle analysis, intracellular viral load via RT-PCR, and Transmission Electron Microscopy (TEM).

RESULTS

After 72 h of MMR treatment, GBM cell lines and primary GBM cells exhibited significant viability reduction compared to untreated cells. Conversely, normal microglial cells showed only minor changes in viability and morphology. Intracellular viral load tests indicated GBM cells' increased sensitivity to MMR viruses compared to normal cells. The cell cycle study also revealed measles and mumps viruses' crucial role in cytopathic effects, with the rubella virus causing cell cycle arrest.

CONCLUSION

Herein the reported results demonstrate the anti-cancer activity of the MMR vaccine against GBM cells. Accordingly, the MMR vaccine warrants further study as a potential new tool for GBM therapy and relapse prevention. Therapeutic potential of the MMR vaccine has been found to be promising in earlier studies as well.

Development and application of oncolytic viruses as the nemesis of tumor cells

Viruses and tumors are two pathologies that negatively impact human health, but what occurs when a virus encounters a tumor? A global consensus among cancer patients suggests that surgical resection, chemotherapy, radiotherapy, and other methods are the primary means to combat cancer. However, with the innovation and development of biomedical technology, tumor biotherapy (immunotherapy, molecular targeted therapy, gene therapy, oncolytic virus therapy, etc.) has emerged as an alternative treatment for malignant tumors. Oncolytic viruses possess numerous anti-tumor properties, such as directly lysing tumor cells, activating anti-tumor immune responses, and improving the tumor microenvironment. Compared to traditional immunotherapy, oncolytic virus therapy offers advantages including high killing efficiency, precise targeting, and minimal side effects. Although oncolytic virus (OV) therapy was introduced as a novel approach to tumor treatment in the 19th century, its efficacy was suboptimal, limiting its widespread application. However, since the U.S. Food and Drug Administration (FDA) approved the first OV therapy drug, T-VEC, in 2015, interest in OV has grown significantly. In recent years, oncolytic virus therapy has shown increasingly promising application prospects and has become a major research focus in the field of cancer treatment. This article reviews the development, classification, and research progress of oncolytic viruses, as well as their mechanisms of action, therapeutic methods, and routes of administration.

The Cellular and Molecular Immunotherapy in Prostate Cancer

In recent history, immunotherapy has become a viable cancer therapeutic option. However, over many years, its tenets have changed, and it now comprises a range of cancer-focused immunotherapies. Clinical trials are currently looking into monotherapies or combinations of medicines that include immune checkpoint inhibitors (ICI), CART cells, DNA vaccines targeting viruses, and adoptive cellular therapy. According to ongoing studies, the discipline should progress by incorporating patient-tailored immunotherapy, immune checkpoint blockers, other immunotherapeutic medications, hormone therapy, radiotherapy, and chemotherapy. Despite significantly increasing morbidity, immunotherapy can intensify the therapeutic effect and enhance immune responses. The findings for the immunotherapy treatment of advanced prostate cancer (PCa) are compiled in this study, showing that is possible to investigate the current state of immunotherapy, covering new findings, PCa treatment techniques, and research perspectives in the field’s unceasing evolution.

Prostate cancer immunotherapy

INTRODUCTION

Medical treatment for prostate cancer (PC) targets hormonal pathways used by malignant cells. Research advances aided in gaining knowledge about implicated molecular pathways and opened the way for establishment of new types of therapies by modifying immunological mechanisms. The aim of this review is to present completed and ongoing research projects regarding PC immunotherapy.

AREAS COVERED

A literature search was conducted in PubMed/MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, and https://www.clinicaltrials.gov/ from inception until 07/2021, to identify completed or ongoing Phase III trials regarding several immunotherapies against PC. Studies on vaccine therapies, CTLA-4 inhibitors, PD-1/PD-L1 inhibitors, PARP inhibitors, PSMA-targeted therapies, and tyrosine kinase inhibitors were considered eligible.

EXPERT OPINION

Although many molecules are being tested against PC cells, only sipuleucel-T has gain approval in the USA. The main reason for this delay in establishing immunotherapy as a standard option for managing PC is the heterogeneity and tumor immune microenvironment complexities. Ipilimumab and olaparib were proved to prolong overall survival significantly against placebo, but a lot of research is going on to identify which patients and at what stage of disease will benefit the most before incorporating them in clinical practice. More recent options such as PSMA-targeted treatments are currently evaluated.

ARTICLE HIGHLIGHTS

Intense research performed on immunotherapy for prostate cancer.Vaccine therapy with sipuleucel-T, the only approved immunotherapy for prostate cancer.Ipilimumab shows survival benefits.Olaparib shows survival benefits.Findings should be confirmed on further trials to identify target population characteristics and proper disease stage.Immunotherapy is not yet a standard due to tumor environment complex interaction between immune system and malignant cells.

Targeting stanniocalcin-1-expressing tumor cells elicits efficient antitumor effects in a mouse model of human lung cancer

Lung cancer is the most common cause of cancer‐related death in developed countries; therefore, the generation of effective targeted therapeutic regimens is essential. Recently, gene therapy approaches toward malignant cells have emerged as attractive molecular therapeutics. Previous studies have indicated that stanniocalcin‐1 (STC‐1), a hormone involved in calcium and phosphate homeostasis, positively regulates proliferation, apoptosis resistance, and glucose metabolism in lung cancer cell lines. In this study, we investigated if targeting STC‐1 in tumor cells could be a promising strategy for lung cancer gene therapy. We confirmed that STC‐1 levels in peripheral blood were higher in lung cancer patients than in healthy donors and that STC‐1 expression was observed in five out of eight lung cancer cell lines. A vector expressing a suicide gene, uracil phosphoribosyltransferase (UPRT), under the control of the STC‐1 promoter, was constructed (pP_STC‐1‐UPRT) and transfected into three STC‐1‐positive cell lines, PC‐9, A549, and H1299. When stably transfected, we observed significant cell growth inhibition using 5‐fluorouracil (5‐FU) treatment. Furthermore, growth of the STC‐1‐negative lung cancer cell line, LK‐2 was significantly arrested when combined with STC‐1‐positive cells transfected with pP_STC‐1‐UPRT.

We believe that conferring cytotoxicity in STC‐1‐positive lung cancer cells using a suicide gene may be a useful therapeutic strategy for lung cancer.

Neoadjuvant Gene-Mediated Cytotoxic Immunotherapy for Non-Small-Cell Lung Cancer: Safety and Immunologic Activity

Gene-mediated cytotoxic immunotherapy (GMCI) is an immuno-oncology approach involving local delivery of a replication-deficient adenovirus expressing herpes simplex thymidine kinase (AdV-tk) followed by anti-herpetic prodrug activation that promotes immunogenic tumor cell death, antigen-presenting cell activation, and T cell stimulation. This phase I dose-escalation pilot trial assessed bronchoscopic delivery of AdV-tk in patients with suspected lung cancer who were candidates for surgery. A single intra-tumoral AdV-tk injection in three dose cohorts (maximum 1012 viral particles) was performed during diagnostic staging, followed by a 14-day course of the prodrug valacyclovir, and subsequent surgery 1 week later. Twelve patients participated after appropriate informed consent. Vector-related adverse events were minimal. Immune biomarkers were evaluated in tumor and blood before and after GMCI. Significantly increased infiltration of CD8+ T cells was found in resected tumors. Expression of activation, inhibitory, and proliferation markers, such as human leukocyte antigen (HLA)-DR, CD38, Ki67, PD-1, CD39, and CTLA-4, were significantly increased in both the tumor and peripheral CD8+ T cells. Thus, intratumoral AdV-tk injection into non-small-cell lung cancer (NSCLC) proved safe and feasible, and it effectively induced CD8+ T cell activation. These data provide a foundation for additional clinical trials of GMCI for lung cancer patients with potential benefit if combined with other immune therapies.

Phase I Trial of Encapsulated Rapamycin in Patients with Prostate Cancer Under Active Surveillance to Prevent Progression

No approved medical therapies prevent progression of low-grade prostate cancer. Rapamycin inhibits cell proliferation and augments immune responses, producing an antitumor effect. Encapsulated rapamycin (eRapa) incorporates rapamycin into a pH-sensitive polymer, ensuring consistent dosing. Here, we present results from a phase I trial evaluating the safety and tolerability of eRapa in patients with prostate cancer. Patients with Gleason ≤7 (3+4) disease (low and intermediate risk) under active surveillance were enrolled in a 3+3 study with three eRapa dosing cohorts (cohort 1, 0.5 mg/week; cohort 2, 1 mg/week; and cohort 3, 0.5 mg/day). Patients were treated for 3 months and followed for an additional 3 months to assess safety, pharmacokinetics, quality of life (QoL), immune response, and disease progression. Fourteen patients (cohort 1, n = 3; cohort 2, n = 3; and cohort 3, n = 8) were enrolled. In cohort 3, one dose-limiting toxicity (DLT; neutropenia) and two non-DLT grade 1-2 adverse events (AE) occurred that resulted in patient withdrawal. All AEs in cohorts 1 and 2 were grade 1. Peak serum rapamycin concentration was 7.1 ng/mL after a 1 mg dose. Stable trough levels (∼2 ng/mL) developed after 48-72 hours. Daily dosing mildly worsened QoL, although QoL recovered after treatment cessation in all categories, except fatigue. Weekly dosing increased naïve T-cell populations. Daily dosing increased central memory cell populations and exhaustion markers. No disease progression was observed. In conclusion, treatment with eRapa was safe and well-tolerated. Daily dosing produced higher frequencies of lower grade toxicities and transient worsening of QoL, while weekly dosing impacted immune response. Future studies will verify clinical benefit and long-term tolerability.Prevention Relevance: There is an unmet medical need for a well-tolerated treatment capable of delaying progression of newly diagnosed low-grade prostate cancer. This treatment would potentially obviate the need for future surgical intervention and improve the perception of active surveillance as a more acceptable option among this patient population.

Clinical Application of Oncolytic Viruses: A Systematic Review

Leveraging the immune system to thwart cancer is not a novel strategy and has been explored via cancer vaccines and use of immunomodulators like interferons. However, it was not until the introduction of immune checkpoint inhibitors that we realized the true potential of immunotherapy in combating cancer. Oncolytic viruses are one such immunotherapeutic tool that is currently being explored in cancer therapeutics. We present the most comprehensive systematic review of all oncolytic viruses in Phase 1, 2, and 3 clinical trials published to date. We performed a systematic review of all published clinical trials indexed in PubMed that utilized oncolytic viruses. Trials were reviewed for type of oncolytic virus used, method of administration, study design, disease type, primary outcome, and relevant adverse effects. A total of 120 trials were found; 86 trials were available for our review. Included were 60 phase I trials, five phase I/II combination trials, 19 phase II trials, and two phase III clinical trials. Oncolytic viruses are feverously being evaluated in oncology with over 30 different types of oncolytic viruses being explored either as a single agent or in combination with other antitumor agents. To date, only one oncolytic virus therapy has received an FDA approval but advances in bioengineering techniques and our understanding of immunomodulation to heighten oncolytic virus replication and improve tumor kill raises optimism for its future drug development.

First-in-human study of anticancer immunotherapy drug candidate mobilan: safety, pharmacokinetics and pharmacodynamics in prostate cancer patients

Toll-like receptor 5 (TLR5) controls endogenous immune responses to pathogens and is a promising target for pharmacological stimulation of anti-tumor immunity. Mobilan is an innovative gene therapy agent consisting of a non-replicating bicistronic adenovirus directing constitutive expression of human Toll-like receptor 5 (TLR5) and the secreted flagellin-based TLR5 agonist, 502s. In mice, Mobilan injection into prostate tumors resulted in autocrine TLR5 signaling, immune system activation, and suppression of tumor growth and metastasis. Here we report a first-in-human placebo-controlled clinical study of Mobilan aimed at evaluating safety, tolerability, pharmacokinetics and pharmacodynamics of a single intra-prostate injection of Mobilan in early stage prostate cancer patients. Mobilan was safe and well-tolerated at all tested doses; thus, the maximum tolerated dose was not identified. Injection of Mobilan induced signs of self-resolving inflammation not present in placebo-injected patients, including transient elevation of PSA and cytokine (G-CSF, IL-6) levels, and increased lymphoid infiltration in prostate tissue. The highest dose of Mobilan (10¹¹ viral particles) produced the best combination of safety and pharmacodynamic effects. Therefore, Mobilan is well-tolerated and induces the expected pharmacodynamic response in humans. These results support further clinical development of Mobilan as a novel immunotherapy for prostate cancer.

Utilizing precision medicine to modulate the prostate tumor microenvironment and enhance immunotherapy

The last two decades of cancer research have seen two major advancements in our ability to treat cancer: precision medicine and immunotherapy. While these approaches have shown striking anticancer efficacy in numerous malignancies, they have not shown similar success and applicability in advanced prostate cancer patients. The fields of precision medicine and immunotherapy have come to realize that targeted therapies are capable of not only inhibiting tumor cell growth, but also promoting antitumor immunity by modulating the tumor microenvironment. Here we examine how personalized medicine can be used to target the tumor immune microenvironment in prostate cancer, with the goal of enhancing clinical responses to immunotherapy.

Origin of personalized medicine in pioneering, passionate, genomic research

Personalized medicine, one of the main promises of the Human Genome Project (HGP) that began three decades ago, is now a new therapeutic paradigm. With its arrival the era of developing drugs to suit all patients, yet often having to withdraw a promising new one because a minority of patients was at risk, even though it had proved valuable for the majority was consigned to history as were trial-and-error strategies being the predominant means of tailoring therapy. But how did it originate and the earliest examples emerge? Is it true that the first personalized diagnostic test was the companion test for Herceptin®? This account of a remarkable journey from genomic and translational research to therapeutic and diagnostic innovations, describes how sequencing the human growth hormone (hGH) locus provided proof of principle for HGP-inspired personalized medicine. Sequencing this locus and the resultant biomanufacture of HGH and the development of a test capable of detecting which patients would benefit from its administration helped silence the skeptics who questioned the validity of such an approach. The associated companion diagnostic was created four years before the invention of the HercepTest® (registered as the first companion diagnostics ever developed). By cultivating genomic research with passion and pursuing its applications, we and many others contributed to the emergence of a new diagnostics industry, the discovery of better actionable gene-targets and to a revitalized pharmaceutical industry capable of developing safer and more effective therapies. In combination, these developments are beginning to fulfill the promise of the HGP, offering each patient the opportunity to adopt the right treatment at the correct dosage in an opportune manner.

Immune reaction by cytoreductive prostatectomy

Prostate cancer (PCa) is the most common non-cutaneous cancer among men and the second leading cause of male cancer deaths in the United States. With no effective cure for advanced disease, the survival rates of castration-resistant disease and metastatic disease remains poor. Treatment via hormonal manipulation, immunotherapy, and chemotherapy remain marginally effective, indicating the need for novel treatment strategies. Cytoreductive prostatectomy (CRP) has grown as a treatment modality for metastatic castration resistant prostate cancer (mCRPC) and an emerging body of literature has demonstrated its survival benefits. In this review, we hope to further explore immunologic changes after CRP and the resultant effects on oncologic outcomes. Conclusively, the data and technical considerations of CRS evolve, CRS may continue to expand treat various type of metastatic cancer. Still, there are little reports about immunological changed after CRP. However, based on technical improvement, CRP and combinational immunotherapy are developing treatments of metastatic disease.

Improving adenoviral vectors and strategies for prostate cancer gene therapy

Gene therapy has been evaluated for the treatment of prostate cancer and includes the application of adenoviral vectors encoding a suicide gene or oncolytic adenoviruses that may be armed with a functional transgene. In parallel, versions of adenoviral vector expressing the p53 gene (Ad-p53) have been tested as treatments for head and neck squamous cell carcinoma and non-small cell lung cancer. Although Ad-p53 gene therapy has yielded some interesting results when applied to prostate cancer, it has not been widely explored, perhaps due to current limitations of the approach. To achieve better functionality, improvements in the gene transfer system and the therapeutic regimen may be required. We have developed adenoviral vectors whose transgene expression is controlled by a p53-responsive promoter, which creates a positive feedback mechanism when used to drive the expression of p53. Together with improvements that permit efficient transduction, this new approach was more effective than the use of traditional versions of Ad-p53 in killing prostate cancer cell lines and inhibiting tumor progression. Even so, gene therapy is not expected to replace traditional chemotherapy but should complement the standard of care. In fact, chemotherapy has been shown to assist in viral transduction and transgene expression. The cooperation between gene therapy and chemotherapy is expected to effectively kill tumor cells while permitting the use of reduced chemotherapy drug concentrations and, thus, lowering side effects. Therefore, the combination of gene therapy and chemotherapy may prove essential for the success of both approaches.

Immunotherapy for Prostate Cancer: Where We Are Headed

Prostate cancer is one of the most common malignant neoplasms in men worldwide, and is the fifth cause of cancer-related death. In recent years, a new generation of therapies have been approved for the management of metastatic disease. Moreover, the development of new immunotherapeutic drugs has become a novel frontier for the treatment of several tumor types; to date, numerous studies have investigated their potential activity, including in prostate cancer. In this article, we discuss the role of emerging immunotherapeutic drugs in prostate cancer patients.

Combining immunotherapies for the treatment of prostate cancer

Sipuleucel-T, a therapeutic dendritic-cell vaccine, was Food and Drug Administration-approved for prostate cancer in 2010. No new immunotherapies for prostate cancer have been approved since. However, novel agents and combination approaches offer great promise for improving outcomes for prostate cancer patients. Here we review the latest developments in immunotherapy for prostate cancer. Sipuleucel-T has demonstrated a survival advantage of 4.1 months in metastatic castration-resistant prostate cancer. PSA-TRICOM (PROSTVAC), a prostate-specific antigen-targeted vaccine platform, showed evidence of clinical and immunologic efficacy in early-phase clinical trials, and results from a phase III trial in advanced disease are pending. While immune checkpoint inhibitors appear to have modest activity as monotherapy, preclinical and clinical data suggest that they may synergize with vaccines, poly [ADP-ribose] polymerase inhibitors, and other agents. Several clinical studies that combine these therapies are underway. Combining prostate cancer vaccines with immune checkpoint inhibitors has great potential for improving clinical outcomes in prostate cancer. Such combination approaches may create and then recruit tumor-specific T cells to tumor while also increasing their effector function. Other emerging agents may also enhance immune-mediated tumor destruction.

Immunotherapy of Prostate Cancer: Facts and Hopes

In the last few years, immunotherapy has become an important cancer treatment modality, and although the principles of immunotherapy have evolved over many decades, the FDA approvals of sipuleucel-T and ipilimumab began a new wave in immuno-oncology. Despite the current enthusiasm, it is unlikely that any of the immunotherapeutics alone can dramatically change prostate cancer outcomes, but combination strategies are more promising and provide a reason for optimism. Several completed and ongoing studies have shown that the combination of cancer vaccines or checkpoint inhibitors with different immunotherapeutic agents, hormonal therapy (enzalutamide), radiotherapy (radium 223), DNA-damaging agents (olaparib), or chemotherapy (docetaxel) can enhance immune responses and induce more dramatic, long-lasting clinical responses without significant toxicity. The goal of prostate cancer immunotherapy does not have to be complete eradication of advanced disease but rather the return to an immunologic equilibrium with an indolent disease state. In addition to determining the optimal combination of treatment regimens, efforts are also ongoing to discover biomarkers of immune response. With such concerted efforts, the future of immunotherapy in prostate cancer looks brighter than ever. Clin Cancer Res; 23(22); 6764-70. ©2017 AACR.

Immunotherapy and gene therapy as novel treatments for cancer

The immune system interacts closely with tumors during the disease development and progression to metastasis. The complex communication between the immune system and the tumor cells can prevent or promote tumor growth. New therapeutic approaches harnessing protective immunological mechanisms have recently shown very promising results. This is performed by blocking inhibitory signals or by activating immunological effector cells directly. Immune checkpoint blockade with monoclonal antibodies directed against the inhibitory immune receptors CTLA-4 and PD-1 has emerged as a successful treatment approach for patients with advanced melanoma. Ipilimumab is an anti-CTLA-4 antibody which demonstrated good results when administered to patients with melanoma. Gene therapy has also shown promising results in clinical trials. Particularly, Herpes simplex virus (HSV)-mediated delivery of the HSV thymidine kinase (TK) gene to tumor cells in combination with ganciclovir (GCV) may provide an effective suicide gene therapy for destruction of glioblastomas, prostate tumors and other neoplasias by recruiting tumor-infiltrating lymphocytes into the tumor. The development of new treatment strategies or combination of available innovative therapies to improve cell cytotoxic T lymphocytes trafficking into the tumor mass and the production of inhibitory molecules blocking tumor tissue immune-tolerance are crucial to improve the efficacy of cancer therapy.

Hitting the nail on the head: combining oncolytic adenovirus-mediated virotherapy and immunomodulation for the treatment of glioma

Glioblastoma is a highly aggressive malignant brain tumor with a poor prognosis and the median survival 14.6 months. Immunomodulatory proteins and oncolytic viruses represent two treatment approaches that have recently been developed for patients with glioblastoma that could extend patient survival and result in better treatment outcomes for patients with this disease. Together, these approaches could potentially augment the treatment efficacy and strength of these anti-tumor therapies. In addition to oncolytic activities, this combinatory approach introduces immunomodulation locally only where cancerous cells are present. This thereby results in the change of the tumor microenvironment from immune-suppressive to immune-vulnerable via activation of cytotoxic T cells or through the removal of glioma cells immune-suppressive capability. This review discusses the strengths and weaknesses of adenoviral oncolytic therapy, and highlights the genetic modifications that result in more effective and targeted viral agents. Additionally, the mechanism of action of immune-activating agents is described and the results of previous clinical trials utilizing these treatments in other solid tumors are reviewed. The feasibility, synergy, and limitations for treatments that combine these two approaches are outlined and areas for which more work is needed are considered.

The evolving role of immunotherapy in prostate cancer

PURPOSE OF REVIEW

In recent clinical trials, immunotherapeutic agents have demonstrated promising results for the treatment of prostate cancer. This review discusses emerging immunotherapies for prostate cancer and their evolving role in sequencing and combination therapy.

RECENT FINDINGS

Therapeutic vaccines including PROSTVAC and DCVAC/PCa have completed promising phase 2 trials for the treatment of prostate cancer and phase 3 trials are underway. Recent evidence supports a synergistic relationship between immunotherapy agents themselves, antiandrogens and with cytotoxic chemotherapy. Prostate cancer patients with good prognostic factors, such as minimal disease burden, appear to achieve the optimal benefit from immunotherapy.

SUMMARY

Therapeutic cancer vaccines and immunomodulating agents have demonstrated activity in the treatment of prostate cancer. Immunotherapies may alter the prostate tumor microenvironment and ongoing studies aim to provide guidance on effective sequencing and combination strategies.

Adenovirus vector carrying REIC/DKK-3 gene: neoadjuvant intraprostatic injection for high-risk localized prostate cancer undergoing radical prostatectomy

As the First-In-Human study of in situ gene therapy using an adenovirus vector carrying the human REIC (reduced expression in immortalized cell)/Dkk-3 gene (Ad-REIC), we conducted neoadjuvant intraprostatic injections in patients with high-risk localized prostate cancer undergoing radical prostatectomy (RP). Patients with recurrence probability of 35% or more within 5 years following RP, as calculated by Kattan's nomogram, were enrolled. Patients received two ultrasound-guided intratumoral injections at 2-week intervals, followed by RP 6 weeks after the second injection. After confirming the safety of the therapeutic interventions with initially planned three escalating doses of 1.0 × 10¹⁰, 1.0 × 10¹¹ and 1.0 × 10¹² viral particles (vp) in 1.0-1.2 ml (n=3, 3 and 6), an additional higher dose of 3.0 × 10¹² vp in 3.6 ml (n=6) was further studied. All four DLs including the additional dose level-4 (DL-4) were feasible with no adverse events, except for grade 1 or 2 transient fever. Laboratory toxicities were grade 1 or 2 elevated aspartate transaminase/alanine transaminase (n=4). Regarding antitumor activities, cytopathic effects (tumor degeneration with cytolysis and pyknosis) and remarkable tumor-infiltrating lymphocytes in the targeted tumor areas were detected in a clear dose-dependent manner. Consequently, biochemical recurrence-free survival in DL-4 was significantly more favorable than in patient groups DL-1+2+3.

Integrating Immunotherapies in Prostate Cancer

In recent years, immunotherapy has emerged as a viable and promising treatment for prostate cancer. Beyond sipulecuel-T, phase III trials are evaluating multiple vaccine and immune-based therapies in men with this disease. Evidence suggests that many of these therapies are effective at augmenting immune responses and slowing tumor growth rates. Yet prospective data evaluating these responses as surrogates for survival are still needed. In the absence of validated intermediate markers of response, growing data suggests that patients with more indolent disease are more likely to benefit from immunotherapies. In order to further optimize immunotherapy use, ongoing trials are evaluating its combination with traditional as well as other immune-based treatments. Preliminary data from these trials are promising and are shedding new light on this area.

Therapeutic vaccines for prostate cancer: recent advances and future directions

In recent years, therapeutic cancer vaccines have emerged as a viable and promising treatment for prostate cancer. Beyond sipuleucel-T, phase III trials are evaluating multiple vaccine platforms in men with this disease. Growing data evaluating vaccine therapies suggests that these agents are more effective in patients with more indolent and possibly also earlier stages of disease. In addition, a wealth of preclinical data has shown that traditional prostate cancer treatments including anti androgens, cytotoxic and radiation therapies may provide immunologic synergy when given in combination with vaccine platforms. Building off this data, numerous clinical trials are evaluating therapeutic cancer vaccines in early stage prostate cancer and also in combination with traditional prostate cancer therapies. In addition, in order to optimize immune responses, ongoing trials are evaluating vaccines in combination with immune checkpoint inhibitors. Preliminary data from these trials have been promising and are offering an exciting glimpse at the future of immunotherapy for this disease.

Feasibility of Neoadjuvant Ad-REIC Gene Therapy in Patients with High-Risk Localized Prostate Cancer Undergoing Radical Prostatectomy

In a phase I/IIa study of in situ gene therapy using an adenovirus vector carrying the human REIC/Dkk‐3 gene (Ad‐REIC), we assessed the inhibitory effects of cancer recurrence after radical prostatectomy (RP), in patients with high risk localized prostate cancer (PCa). After completing the therapeutic interventions with initially planned three escalating doses of 1.0 × 10¹⁰, 1.0 × 10¹¹, and 1.0 × 10¹² viral particles (VP) in 1.0–1.2 mL (n = 3, 3, and 6), an additional higher dose of 3.0 × 10¹² VP in 3.6 mL (n = 6) was further studied. Patients with recurrence probability of 35% or more within 5 years after RP as calculated by Kattan's nomogram, were enrolled. They received two ultrasound‐guided intratumoral injections at 2‐week intervals, followed by RP 6 weeks after the second injection. Based on the findings of MRI and biopsy mapping, as a rule, one track injection to the most prominent cancer area was given to initial 12 patients and 3 track injections to multiple cancer areas in additional 6 patients. As compared to the former group, biochemical recurrence‐free survival of the latter showed a significantly favorable outcome. Neoadjuvant Ad‐REIC, mediating simultaneous induction of cancer selective apoptosis and augmentation of antitumor immunity, is a feasible approach in preventing cancer recurrence after RP. (199)

Gene-mediated cytotoxic immunotherapy as adjuvant to surgery or chemoradiation for pancreatic adenocarcinoma

BACKGROUND

While surgical resection of pancreatic adenocarcinoma provides the only chance of cure, long-term survival remains poor. Immunotherapy may improve outcomes, especially as adjuvant to local therapies. Gene-mediated cytotoxic immunotherapy (GMCI) generates a systemic anti-tumor response through local delivery of an adenoviral vector expressing the HSV-tk gene (aglatimagene besadenovec, AdV-tk) followed by anti-herpetic prodrug. GMCI has demonstrated synergy with standard of care (SOC) in other tumor types. This is the first application in pancreatic cancer.

METHODS

Four dose levels (3 × 10(10) to 1 × 10(12) vector particles) were evaluated as adjuvant to surgery for resectable disease (Arm A) or to 5-FU chemoradiation for locally advanced disease (Arm B). Each patient received two cycles of AdV-tk + prodrug.

RESULTS

Twenty-four patients completed therapy, 12 per arm, with no dose-limiting toxicities. All Arm A patients were explored, eight were resected, one was locally advanced and three had distant metastases. CD8(+) T cell infiltration increased an average of 22-fold (range sixfold to 75-fold) compared with baseline (p = 0.0021). PD-L1 expression increased in 5/7 samples analyzed. One node-positive resected patient is alive >66 months without recurrence. Arm B RECIST response rate was 25 % with a median OS of 12 months and 1-year survival of 50 %. Patient-reported quality of life showed no evidence of deterioration.

CONCLUSIONS

AdV-tk can be safely combined with pancreatic cancer SOC without added toxicity. Response and survival compare favorably to expected outcomes and immune activity increased. These results support further evaluation of GMCI with more modern chemoradiation and surgery as well as PD-1/PD-L1 inhibitors in pancreatic cancer.