Vaccinia-based oncolytic immunotherapy Pexastimogene Devacirepvec in patients with advanced hepatocellular carcinoma after sorafenib failure: a randomized multicenter Phase IIb trial (TRAVERSE)

Inhibition of MEK-ERK pathway enhances oncolytic vaccinia virus replication in doxorubicin-resistant ovarian cancer

Oncolytic vaccinia virus (OVV) has been reported to induce cell death in various types of cancer; however, the oncolytic activity of OVV in drug-resistant ovarian cancer remains limited. In the present study, we established doxorubicin-resistant ovarian cancer cells (A2780-R) from the A2780 human ovarian cancer cell line. Both A2780 and A2780-R cells were infected with OVV to explore its anticancer effects. Interestingly, OVV-infected A2780-R cells showed reduced viral replication and cell death compared with A2780 cells, suggesting their resistance against OVV-induced oncolysis; to understand the mechanism underlying this resistance, we explored the involvement of protein kinases. Among protein kinase inhibitors, PD0325901, an MEK inhibitor, significantly augmented OVV replication and cell death in A2780-R cells. PD0325901 treatment increased the phosphorylation of STAT3 in A2780-R cells. Moreover, cryptotanshinone, a STAT3 inhibitor, abrogated PD0325901-stimulated OVV replication. Furthermore, trametinib, a clinically approved MEK inhibitor, increased OVV replication in A2780-R cells. Transcriptomic analysis showed that the MEK inhibitor promoted OVV replication via increasing STAT3 activation and downregulating the cytosolic DNA-sensing pathway. Combined treatment with OVV and trametinib attenuated A2780-R xenograft tumor growth. These results suggest that pharmacological inhibition of MEK reinforces the oncolytic efficacy of OVV in drug-resistant ovarian cancer.

Immunotherapy as a Therapeutic Strategy for Gastrointestinal Cancer-Current Treatment Options and Future Perspectives

Gastrointestinal (GI) cancer constitutes a highly lethal entity among malignancies in the last decades and is still a major challenge for cancer therapeutic options. Despite the current combinational treatment strategies, including chemotherapy, surgery, radiotherapy, and targeted therapies, the survival rates remain notably low for patients with advanced disease. A better knowledge of the molecular mechanisms that influence tumor progression and the development of optimal therapeutic strategies for GI malignancies are urgently needed. Currently, the development and the assessment of the efficacy of immunotherapeutic agents in GI cancer are in the spotlight of several clinical trials. Thus, several new modalities and combinational treatments with other anti-neoplastic agents have been identified and evaluated for their efficiency in cancer management, including immune checkpoint inhibitors, adoptive cell transfer, chimeric antigen receptor (CAR)-T cell therapy, cancer vaccines, and/or combinations thereof. Understanding the interrelation among the tumor microenvironment, cancer progression, and immune resistance is pivotal for the optimal therapeutic management of all gastrointestinal solid tumors. This review will shed light on the recent advances and future directions of immunotherapy for malignant tumors of the GI system.

Emerging Therapies for Hepatocellular Carcinoma (HCC)

Hepatocellular carcinoma (HCC) arises from hepatocytes and accounts for 90% of primary liver cancer. According to Global Cancer Incidence, Mortality and Prevalence (GLOBOCAN) 2020, globally HCC is the sixth most common cancer and the third most common cause of cancer-related deaths. Reasons for HCC prognosis remaining dismal are that HCC is asymptomatic in its early stages, leading to late diagnosis, and it is markedly resistant to conventional chemo- and radiotherapy. Liver transplantation is the treatment of choice in early stages, while surgical resection, radiofrequency ablation (RFA) and trans arterial chemoembolization (TACE) are Food and Drug Administration (FDA)-approved treatments for advanced HCC. Additional first line therapy for advanced HCC includes broad-spectrum tyrosine kinase inhibitors (TKIs), such as sorafenib and lenvatinib, as well as a combination of immunotherapy and anti-angiogenesis therapy, namely atezolizumab and bevacizumab. However, these strategies provide nominal extension in the survival curve, cause broad spectrum toxic side effects, and patients eventually develop therapy resistance. Some common mutations in HCC, such as in telomerase reverse transcriptase (TERT), catenin beta 1 (CTNNB1) and tumor protein p53 (TP53) genes, are still considered to be undruggable. In this context, identification of appropriate gene targets and specific gene delivery approaches create the potential of gene- and immune-based therapies for the safe and effective treatment of HCC. This review elaborates on the current status of HCC treatment by focusing on potential gene targets and advanced techniques, such as oncolytic viral vectors, nanoparticles, chimeric antigen receptor (CAR)-T cells, immunotherapy, and clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9), and describes future prospects in HCC treatment.

Emerging immunotherapy for HCC: A guide for hepatologists

HCC is one of the most common cancers worldwide, and the third leading cause of cancer-related death globally. HCC comprises nearly 90% of all cases of primary liver cancer. Approximately half of all patients with HCC receive systemic therapy during their disease course, particularly in the advanced stages of disease. Immuno-oncology has been paradigm shifting for the treatment of human cancers, with strong and durable antitumor activity in a subset of patients across a variety of malignancies including HCC. Immune checkpoint inhibition with atezolizumab and bevacizumab, an antivascular endothelial growth factor neutralizing antibody, has become first-line therapy for patients with advanced HCC. Beyond immune checkpoint inhibition, immunotherapeutic strategies such as oncolytic viroimmunotherapy and adoptive T-cell transfer are currently under investigation. The tumor immune microenvironment of HCC has significant immunosuppressive elements that may affect response to immunotherapy. Major unmet challenges include defining the role of immunotherapy in earlier stages of HCC, evaluating combinatorial strategies that use targeting of the immune microenvironment plus immune checkpoint inhibition, and identifying treatment strategies for patients who do not respond to the currently available immunotherapies. Herein, we review the rationale, mechanistic basis and supporting preclinical evidence, and available clinical evidence for immunotherapies in HCC as well as ongoing clinical trials of immunotherapy.

Experimental drug treatments for hepatocellular carcinoma: Clinical trial failures 2015 to 2021

INTRODUCTION

Hepatocellular carcinoma (HCC) is a major health problem worldwide with limited systemic therapy options. Since the approval of sorafenib in 2008, no systemic therapy has provided a sustained/robust/survival benefit for patients with advanced HCC until recently. Many initially promising therapies have been trialed, but survival outcomes remained stagnant. As such, knowledge concerning previous treatment failures may help guide further areas of study, as well inform future therapeutic approaches.

AREA COVERED

This article reviews recent advances in the treatment of HCC. Despite some recent success, many systemic and locoregional therapies have failed to produce significant improvements in outcome. These treatment failures are examined and insight into pathways for future success are discussed.

EXPERT OPINION

Combination atezolizumab and bevacizumab has changed the landscape of systemic treatment for patients with HCC when it became the first therapy after demonstrating improve outcomes over sorafenib. Clinical trials in patients with advanced HCC have inherent difficulty with challenges to determine if a patient's declining liver function is secondary to disease progression, worsening cirrhosis, or drug toxicity, which may skew results. As we gain more knowledge of underlying genetic alterations behind the pathophysiology of the development of HCC, molecular markers may be identified to assist in predicting which patients would respond to a specific therapy.

Engaging Pattern Recognition Receptors in Solid Tumors to Generate Systemic Antitumor Immunity

Malignant tumors frequently exploit innate immunity to evade immune surveillance. The priming, function, and polarization of antitumor immunity fundamentally depends upon context provided by the innate immune system, particularly antigen presenting cells. Such context is determined in large part by sensing of pathogen specific and damage associated features by pathogen recognition receptors (PRRs). PRR activation induces the delivery of T cell priming cues (e.g. chemokines, co-stimulatory ligands, and cytokines) from antigen presenting cells, playing a decisive role in the cancer immunity cycle. Indeed, endogenous PRR activation within the tumor microenvironment (TME) has been shown to generate spontaneous antitumor T cell immunity, e.g., cGAS-STING mediated activation of antigen presenting cells after release of DNA from dying tumor cells. Thus, instigating intratumor PRR activation, particularly with the goal of generating Th1-promoting inflammation that stokes endogenous priming of antitumor CD8⁺ T cells, is a growing area of clinical investigation. This approach is analogous to in situ vaccination, ultimately providing a personalized antitumor response against relevant tumor associated antigens. Here I discuss clinical stage intratumor modalities that function via activation of PRRs. These approaches are being tested in various solid tumor contexts including melanoma, colorectal cancer, glioblastoma, head and neck squamous cell carcinoma, bladder cancer, and pancreatic cancer. Their mechanism (s) of action relative to other immunotherapy approaches (e.g., antigen-defined cancer vaccines, CAR T cells, dendritic cell vaccines, and immune checkpoint blockade), as well as their potential to complement these approaches are also discussed. Examples to be reviewed include TLR agonists, STING agonists, RIG-I agonists, and attenuated or engineered viruses and bacterium. I also review common key requirements for effective in situ immune activation, discuss differences between various strategies inclusive of mechanisms that may ultimately limit or preclude antitumor efficacy, and provide a summary of relevant clinical data.

Systemic Therapy for Hepatocellular Carcinoma: Current Updates and Outlook

Hepatocellular carcinoma (HCC) has emerged the culprit of cancer-related mortality worldwide with its dismal prognosis climbing. In recent years, ground-breaking progress has been made in systemic therapy for HCC. Targeted therapy based on specific signaling molecules, including sorafenib, lenvatinib, regorafenib, cabozantinib, and ramucirumab, has been widely used for advanced HCC (aHCC). Immunotherapies such as pembrolizumab and nivolumab greatly improve the survival of aHCC patients. More recently, synergistic combination therapy has boosted first-line (atezolizumab in combination with bevacizumab) and second-line (ipilimumab in combination with nivolumab) therapeutic modalities for aHCC. This review aims to summarize recent updates of systemic therapy relying on the biological mechanisms of HCC, particularly highlighting the approved agents for aHCC. Adjuvant and neoadjuvant therapy, as well as a combination with locoregional therapies (LRTs), are also discussed. Additionally, we describe the promising effect of traditional Chinese medicine (TCM) as systemic therapy on HCC. In this setting, the challenges and future directions of systemic therapy for HCC are also explored.

CD19-targeted BiTE expression by an oncolytic vaccinia virus significantly augments therapeutic efficacy against B-cell lymphoma

Immunotherapy with CD19-targeting bispecific T-cell engagers (CD19BiTEs) has demonstrated highly effective killing of cancer cells in patients with precursor acute lymphoblastic leukemia and non-Hodgkin's lymphomas. However, there are some drawbacks to this therapy, such as toxicity, short half-life in the serum, and immunosuppressive tumor microenvironment that could limit the use of CD19BiTEs in the clinic. Here, we generate an oncolytic vaccinia virus (OVV) encoding a CD19-specific BiTE (OVV-CD19BiTE). We demonstrate that OVV-CD19BiTE's ability to replicate and induce oncolysis was similar to that of its parental counterpart. Supernatants from OVV-CD19BiTE-infected cells could induce activation and proliferation of human T cells, and the bystander effect of the virus was also demonstrated. In vivo study showed that OVV-CD19BiTE selectively replicated within tumor tissue, and contributed to a more significantly increased percentage of CD3, CD8, and naïve CD8 T subpopulations within tumors in contrast to blinatumomab. More importantly, treatment with OVV-CD19BiTE both in vitro and in vivo resulted in potent antitumor activity in comparison with control OVV or blinatumomab, a first-in-class BiTE, thereby resulting in long-term tumor remissions without relapse. The study provides strong evidence for the therapeutic benefits of CD19-targeting BiTE expression by OVV, and suggests the feasibility of testing the approach in clinical trials.

The efficacy and safety of oncolytic viruses in the treatment of intermediate to advanced solid tumors: a systematic review and meta-analysis

Background

Cancer treatment remains one of the most formidable challenges worldwide. Some novel treatment strategies, including molecularly targeted therapy, gene therapy, and cellular immunotherapy, have also been investigated to improve therapeutic effects for cancer patients and have demonstrated unexpected positive effects. This systematic review and meta-analysis evaluated the efficacy and safety of oncolytic virus (OV) monotherapy or combination therapy for intermediate to advanced solid tumors.

Methods

We retrieved articles from PubMed, Embase, Web of Science, CNKI, Wanfang and VIP. The quality of the included studies was assessed by Review Manager Software version 5.3. STATA software was used to perform meta-analyses of efficacy, overall survival (OS) and adverse reactions.

Results

A total of 22 studies involving 3,996 patients were included in this analysis, including 13 H101 studies, 5 T-VEC studies, 2 Pexa-Vec studies, 1 HF10 study and 1 Reolysin study. Regarding oncolytic adenovirus H101, meta-analysis showed that patients treated with H101 monotherapy or H101 combined with chemotherapy had a significantly higher objective response rate (ORR) than those treated with chemotherapy. Patients in the H101 and T-VEC groups had significantly longer effect size (ES) than the control group patients. The odds ratio (OR) and ES of patients with hepatocellular carcinoma, lung cancer and melanoma treated with OV were analyzed. For the safety profile, the total incidence of adverse reactions was similar in both groups. In terms of the other OVs, according to a systematic review, we found that after Reolysin treatment, the ORR was 26.9% in patients with head and neck cancer. The phase I study of HF10 exhibited some therapeutic potential. The adverse events (AEs) associated with the other OVs mainly included fever, nausea and vomiting, leukopenia, and hypotension.

Discussion

OVs are effective and well tolerated for the treatment of intermediate to advanced solid cancer and represent a promising therapeutic approach for solid cancers.

Immunotherapies for hepatocellular carcinoma

Cases of hepatocellular carcinoma (HCC) are rapidly rising. This is particularly the case in the Western world, as a result of increasing rates of chronic liver disease, secondary to lifestyle-associated risk factors and the lack of an established screening programme for the general population. Traditionally, radical/curative treatment options for HCC, including liver transplantation and surgical resection are reserved for the minority of patients, presenting with an early stage cancer. For patients with advanced disease, Sorafenib and Lenvatinib were, until recently, the only licensed systemic treatments, and provided only limited survival benefits at the cost of a multitude of potential side effects. Recent scientific advances in the field of cancer immunotherapy have renewed significant interest in advanced HCC, in order to fulfil this apparent area of unmet clinical need. This has led to the success and recent regulatory approval of an Atezolizumab/Bevacizumab combination for the first-line treatment of advanced HCC following results from the IMbrave150 clinical trial in 2019, with further immune checkpoint inhibitors currently undergoing testing in advanced clinical trials. Furthermore, other cancer immunotherapies, including chimeric antigen receptor T-cells, dendritic cell vaccines and oncolytic viruses are also in early stage clinical trials, for the treatment of advanced HCC. This review will summarise the major approaches that have been and are currently in development for the systemic treatment of advanced HCC, their advantages, drawbacks, and predictions of where this revolutionary treatment field will continue to travel for the foreseeable future.

The Protective Role of Etoricoxib Against Diethylnitrosamine/2-acetylaminofluorene- Induced Hepatocarcinogenesis in Wistar Rats: The Impact of NF-κB/COX-2/PGE2 Signaling

BACKGROUND

Liver cancer ranks as the 7th and 5th leading cause of cancer morbidity worldwide in men and women, respectively. Hepatocellular Carcinoma (HCC) is the most common type of liver cancer and is associated with an increasing global burden of Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH).

OBJECTIVE

The present study aimed to investigate the possible chemopreventive effect of etoricoxib on diethylnitrosamine (DENA) and 2-acetylaminofluorene (2AAF)-induced HCC in male Wistar rats.

METHODS

HCC was induced by DENA (150 mg/kg/week; i.p) for 2 weeks, then 2AAF (20 mg/kg; p.o) every other day for three successive weeks. Etoricoxib (0.6 mg/kg, p.o.) was given to DENA/ 2AAF-administered rats for 20 weeks.

RESULTS

Etoricoxib significantly suppressed alpha-fetoprotein (AFP) and carbohydrate antigen 19-9 (CA19.9) as liver tumor biomarkers. It also decreased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin levels while increased serum albumin levels. Besides, it alleviated DENA/2AAF-induced histopathological abrasions and inflammatory cell infiltration. Furthermore, etoricoxib showed a potent antioxidant effect, supported by a significant lipid peroxide reduction and elevation in superoxide dismutase activity and GSH content. In addition, Etoricoxib significantly down-regulated the protein expression of interleukin 1 beta (IL-1β), tumor necrosis factor α (TNFα), nuclear Factor-kappa B (NF-κB), phosphorylated nuclear Factor-kappa B (p-NF-κB), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2).

CONCLUSION

In conclusion, the current results proved that etoricoxib possesses an anticarcinogenic effect via its antioxidant, anti-inflammatory, and modulation of NF-κB/COX-2/PGE2 signaling.

Efficacy and Safety of Second-line Treatments in Patients with Advanced Hepatocellular Carcinoma after Sorafenib Failure: A Meta-analysis

BACKGROUND AND AIMS

In the last decade, several second-line therapies followed by sorafenib in patients with advanced hepatocellular carcinoma (HCC) have been reported. But the outcomes were different from each other. This meta-analysis aimed to evaluate the efficacy and safety of the second-line therapies followed by sorafenib in patients with advanced HCC.

METHODS

Embase (1974 to October 2019) and Ovid MEDLINE (1946 to October 2019) were searched for randomized clinical trials on second-line therapies followed by sorafenib in patients with advanced HCC. The quality of each study was assessed by the modified Jadad scale. Statistical analysis was carried out by RevMan5.3 software. Efficacy and safety were analyzed. Efficacy included overall survival (OS), disease control rate, time to progression, and progression-free survival.

RESULTS

Eight studies involving 3,173 patients were eligible. No difference in OS was found between the second-line treatment group and the control group (HR=0.87, 95% CI: 0.74-1.01, p=0.06). Disease control rate (relative risk (RR)=1.36, 95% CI: 1.16-1.60, p=0.0002), time to progression (HR=0.64, 95% CI: 0.51-0.81, p=0.0002) and progression-free survival (HR=0.60, 95% CI: 0.46-0.77, p<0.0001) were significantly improved by the second-line therapies. There was a slight difference in adverse events of any grade (RR=1.07, 95% CI: 1.00-1.14, p=0.03) between the two groups.

CONCLUSIONS

These second-line therapies followed by sorafenib may potentially improve the prognosis in patients with advanced HCC. Compared with other second-line therapies, regorafenib seemed to be more effective.

Oncolytic virotherapy as immunotherapy

Recognizing immune responses to oncolytic virotherapy opens the way for new combinations.

Development of oncolytic viruses for cancer therapy

Oncolytic virotherapy is a therapeutic approach that uses replication-competent viruses to kill cancers. The ability of oncolytic viruses to selectively replicate in cancer cells leads to direct cell lysis and induction of anticancer immune response. Like other anticancer therapies, oncolytic virotherapy has several limitations such as viral delivery to the target, penetration into the tumor mass, and antiviral immune responses. This review provides an insight into the different characteristics of oncolytic viruses (natural and genetically modified) that contribute to effective applications of oncolytic virotherapy in preclinical and clinical trials, and strategies to overcome the limitations. The potential of oncolytic virotherapy combining with other conventional treatments or cancer immunotherapies involving immune checkpoint inhibitors and CAR-T therapy could form part of future multimodality treatment strategies.

Immunotherapy for Hepatocellular Carcinoma: Current Status and Future Prospects

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer with poor prognosis. Surgery, chemotherapy, and radiofrequency ablation are three conventional therapeutic options that will help only a limited percentage of HCC patients. Cancer immunotherapy has achieved dramatic advances in recent years and provides new opportunities to treat HCC. However, HCC has various etiologies and can evade the immune system through multiple mechanisms. With the rapid development of genetic engineering and synthetic biology, a variety of novel immunotherapies have been employed to treat advanced HCC, including immune checkpoint inhibitors, adoptive cell therapy, engineered cytokines, and therapeutic cancer vaccines. In this review, we summarize the current landscape and research progress of different immunotherapy strategies in the treatment of HCC. The challenges and opportunities of this research field are also discussed.

Thermal ablation and immunotherapy for hepatocellular carcinoma: Recent advances and future directions

Hepatocellular carcinoma (HCC) is one of most common cancers that cause death in the world. Thermal ablation (TA) is an important alternative treatment method for HCC patients who are not appropriate for surgery or liver transplantation. Particularly for small and early HCCs, TA can be considered as the first-line curative treatment. However, local and distant recurrence rates are still high even though the TA equipment and technology develop rapidly. Immunotherapy is a novel systemic treatment method to enhance the anti-tumor immune response of HCC patients, which has the potential to reduce the tumor recurrence and metastasis. The combination of local TA and systemic immunotherapy for HCCs may be an ideal treatment for enhancing the efficacy of TA and controlling the recurrence. Herein we summarize the latest progress in TA, immunotherapy, and their combination for the treatment of patients with HCC and discuss the limitations and future research directions of the combined therapy.

HCC and Molecular Targeting Therapies: Back to the Future

Hepatocellular carcinoma (HCC) is one of the leading causes of death from cancer in the world. Recently, the effectiveness of new antiviral therapies and the HBV vaccine have reduced HCC’s incidence, while non-alcoholic steato-hepatitis is an emerging risk factor. This review focuses on antiangiogenic molecules and immune checkpoint inhibitors approved for HCC treatment and possible future approaches. Sorafenib was the first drug approved for the treatment of advanced HCC (aHCC) and it has been shown to increase survival by a few months. Lenvatinib, a multikinase inhibitor, has shown non-inferiority in survival compared with sorafenib and an improvement in progression-free survival (PFS). The combination of atezolizumab (an anti-PDL1 antibody) and bevacizumab (an anti-VEGF antibody) was the first drug combination approved for HCC, demonstrating improved survival compared with sorafenib (19.2 vs. 13.4 months). As a second line of therapy, three regimens (regorafenib, cabozantinib, and ramucirumab) have been approved for the treatment of aHCC after progression on sorafenib according to guidelines. Furthermore, nivolumab, pembrolizumab, and nivolumab plus ipilimumab have been approved by the FDA (2017, 2018, and 2020, respectively). Finally, immune target therapy, cancer vaccines, and epigenetic drugs represent three new possible weapons for the treatment of HCC.

The role of NK cells in oncolytic viral therapy: a focus on hepatocellular carcinoma

Natural killer (NK) cells have a key role in host anti-tumour immune responses via direct killing of tumour cells and promotion of adaptive immune responses. They are therefore attractive targets to promote the anti-tumour efficacy of oncolytic viral therapies. However, NK cells are also potent components of the host anti-viral immune response, and therefore have the potential for detrimental anti-viral responses, limiting the spread and persistence of oncolytic viruses. Oncolytic viruses are currently being investigated for the treatment of hepatocellular carcinoma (HCC), a leading cause of cancer-related death with a high unmet clinical need. In this review, we highlight the role of NK cells in oncolytic virus therapy, their potential for improving treatment options for patients with HCC, and discuss current and potential strategies targeting NK cells in combination with oncolytic viral therapies.

Efficacy and safety of oncolytic viruses in advanced or metastatic cancer: a network meta-analysis

BACKGROUND

Oncolytic viruses (OVs) have shown prospects in advanced and metastatic cancer, and many clinical trials have been carried out. To compare OV therapies comprehensively and provide a categorized profile and ranking of efficacy and safety, a network meta-analysis was conducted.

METHODS

A total of 5948 studies were screened and 13 randomized controlled trials with 1939 patients, of whom 1106 patients received OV therapies, comparing four OVs (NTX-010, pexastimogene devacirepvec (Pexa-Vec), talimogene laherparepvec (T-VEC), and pelareorep) were included in a Bayesian network meta-analysis. Eligible studies reported at least one of the following clinical outcome measures: objective response rate (ORR) and grade ≥ 3 adverse events.

RESULTS

Compared to systemic treatments alone, talimogene laherparepvec (T-VEC) (OR 7.00, 95% CI 1.90-26.00) and T-VEC plus systemic treatment (2.90, 0.80-11.00) showed better objective response rates (ORRs), whereas Pexa-Vec 1 * 109 pfu plus systemic treatment (0.91, 0.26-3.00) and pelareorep plus systemic treatment (1.10, 0.61-2.00) were found to be comparable. The grade ≥ 3 adverse event ranking of the treatments from worst to best was as follows: T-VEC (ranking probability 24%), Pexa-Vec 1 * 109 pfu plus systemic treatment (21%), Pexa-Vec 1 * 109 pfu (17%), T-VEC plus systemic treatment (13%), pelareorep plus systemic treatment (13%), systemic treatments (18%), Pexa-Vec 1 * 108 pfu (12%), and NTX-010 (20%).

CONCLUSIONS

Compared with other oncolytic virus therapies for patients with advanced or metastatic cancer, T-VEC and T-VEC plus systemic treatment appear to provide the best ORR therapy in terms of monotherapy and combination respectively, but should be given with caution to grade ≥ 3 adverse events. Conversely, combining OVs with chemotherapy or target agents was demonstrated not to improve efficacy compared with chemotherapy or target agents alone. Combining OV therapies with immune-checkpoint inhibitors, instead of chemotherapy or target agents, tended to provide better ORRs without causing severe adverse events. This study will guide treatment choice and optimize future trial designs for investigations of advanced or metastatic cancer.

Virotherapy in Germany-Recent Activities in Virus Engineering, Preclinical Development, and Clinical Studies

Virotherapy research involves the development, exploration, and application of oncolytic viruses that combine direct killing of cancer cells by viral infection, replication, and spread (oncolysis) with indirect killing by induction of anti-tumor immune responses. Oncolytic viruses can also be engineered to genetically deliver therapeutic proteins for direct or indirect cancer cell killing. In this review—as part of the special edition on “State-of-the-Art Viral Vector Gene Therapy in Germany”—the German community of virotherapists provides an overview of their recent research activities that cover endeavors from screening and engineering viruses as oncolytic cancer therapeutics to their clinical translation in investigator-initiated and sponsored multi-center trials. Preclinical research explores multiple viral platforms, including new isolates, serotypes, or fitness mutants, and pursues unique approaches to engineer them towards increased safety, shielded or targeted delivery, selective or enhanced replication, improved immune activation, delivery of therapeutic proteins or RNA, and redirecting antiviral immunity for cancer cell killing. Moreover, several oncolytic virus-based combination therapies are under investigation. Clinical trials in Germany explore the safety and potency of virotherapeutics based on parvo-, vaccinia, herpes, measles, reo-, adeno-, vesicular stomatitis, and coxsackie viruses, including viruses encoding therapeutic proteins or combinations with immune checkpoint inhibitors. These research advances represent exciting vantage points for future endeavors of the German virotherapy community collectively aimed at the implementation of effective virotherapeutics in clinical oncology.

Prospects and Challenges for T Cell-Based Therapies of HCC

The scope of therapeutic options for the treatment of hepatocellular carcinoma (HCC) has recently been expanded by immunotherapeutic regimens. T cell-based therapies, especially in combination with other treatments have achieved far better outcomes compared to conventional treatments alone. However, there is an emerging body of evidence that eliciting T cell responses in immunotherapeutic approaches is insufficient for favorable outcomes. Immune responses in HCC are frequently attenuated in the tumor microenvironment (TME) or may even support tumor progress. Hence, therapies with immune checkpoint inhibitors or adoptive cell therapies appear to necessitate additional modification of the TME to unlock their full potential. In this review, we focus on immunotherapeutic strategies, underlying molecular mechanisms of CD8 T cell immunity, and causes of treatment failure in HCC of viral and non-viral origin. Furthermore, we provide an overview of TME features in underlying etiologies of HCC patients that mediate therapy resistance to checkpoint inhibition and discuss strategies from the literature concerning current approaches to these challenges.

Combinatorial Approaches for Cancer Treatment Using Oncolytic Viruses: Projecting the Perspectives through Clinical Trials Outcomes

Recent cancer immunotherapy breakthroughs have fundamentally changed oncology and revived the fading hope for a cancer cure. The immune checkpoint inhibitors (ICI) became an indispensable tool for the treatment of many malignant tumors. Alongside ICI, the application of oncolytic viruses in clinical trials is demonstrating encouraging outcomes. Dozens of combinations of oncolytic viruses with conventional radiotherapy and chemotherapy are widely used or studied, but it seems quite complicated to highlight the most effective combinations. Our review summarizes the results of clinical trials evaluating oncolytic viruses with or without genetic alterations in combination with immune checkpoint blockade, cytokines, antigens and other oncolytic viruses as well. This review is focused on the efficacy and safety of virotherapy and the most promising combinations based on the published clinical data, rather than presenting all oncolytic virus variations, which are discussed in comprehensive literature reviews. We briefly revise the research landscape of oncolytic viruses and discuss future perspectives in virus immunotherapy, in order to provide an insight for novel strategies of cancer treatment.

In Situ Vaccination as a Strategy to Modulate the Immune Microenvironment of Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is a highly prevalent malignancy that develops in patients with chronic liver diseases and dysregulated systemic and hepatic immunity. The tumor microenvironment (TME) contains tumor-associated macrophages (TAM), cancer-associated fibroblasts (CAF), regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC) and is central to mediating immune evasion and resistance to therapy. The interplay between these cells types often leads to insufficient antigen presentation, preventing effective anti-tumor immune responses. In situ vaccines harness the tumor as the source of antigens and implement sequential immunomodulation to generate systemic and lasting antitumor immunity. Thus, in situ vaccines hold the promise to induce a switch from an immunosuppressive environment where HCC cells evade antigen presentation and suppress T cell responses towards an immunostimulatory environment enriched for activated cytotoxic cells. Pivotal steps of in situ vaccination include the induction of immunogenic cell death of tumor cells, a recruitment of antigen-presenting cells with a focus on dendritic cells, their loading and maturation and a subsequent cross-priming of CD8+ T cells to ensure cytotoxic activity against tumor cells. Several in situ vaccine approaches have been suggested, with vaccine regimens including oncolytic viruses, Flt3L, GM-CSF and TLR agonists. Moreover, combinations with checkpoint inhibitors have been suggested in HCC and other tumor entities. This review will give an overview of various in situ vaccine strategies for HCC, highlighting the potentials and pitfalls of in situ vaccines to treat liver cancer.

The Current Landscape of Clinical Trials for Systemic Treatment of HCC

Simple Summary

Liver cancer is a life-threatening disease. Apart from surgery and catheter-guided therapies, drugs are a central pillar for its treatment. Clinical trials are research studies that are designed to evaluate the treatment effect of a given drug. Therefore, they are the driving force behind innovation and medical progress. One such innovation in the past years has been immunotherapy, which has become increasingly important for treating cancer. Recently, the first such therapy has been approved for the treatment of liver cancer. Current clinical trials are exploring the benefit of immunotherapy and other therapies for this disease. This article gives an overview of such trials paying attention to the different underlying treatment strategies and the varying clinical settings, depending on the stage of the disease.

Abstract

The clinical development of systemic treatments for hepatocellular carcinoma (HCC) has gained significant momentum in recent years. After the unexpected failure of the phase 3 trials testing the PD1-inhibitors nivolumab and pembrolizumab as monotherapy in advanced HCC, a multitude of trials employing different agents in various combinations and at different disease stages have been initiated. The first positive results reported for the combination of atezolizumab and bevacizumab, as the first line treatment of advanced HCC, will bring lasting change to the management of HCC and has increased the odds of success for alternative combination therapies. This review article seeks to provide clarity on the complex and evolving landscape of clinical trials on systemic treatments of HCC. It covers current trials which test various systemic treatments (i) in the first and second line in advanced HCC, (ii) in intermediate HCC, (iii) as adjuvant as well as (iv) neoadjuvant strategies, and (v) including immune interventions other than immune checkpoint inhibition.

Oncolytic Virotherapy for Cancer: Clinical Experience

Oncolytic viruses are a new class of therapeutics which are largely in the experimental stage, with just one virus approved by the FDA thus far. While the concept of oncolytic virotherapy is not new, advancements in the fields of molecular biology and virology have renewed the interest in using viruses as oncolytic agents. Backed by robust preclinical data, many oncolytic viruses have entered clinical trials. Oncolytic viruses that have completed some levels of clinical trials or are currently undergoing clinical trials are mostly genetically engineered viruses, with the exception of some RNA viruses. Reolysin, an unmodified RNA virus is clinically the most advanced oncolytic RNA virus that has completed different phases of clinical trials. Other oncolytic viruses that have been studied in clinical trials are mostly DNA viruses that belong to one of the three families: herpesviridae, poxviridae or adenoviridae. In this review work we discuss recent clinical studies with oncolytic viruses, especially herpesvirus, poxvirus, adenovirus and reovirus. In summary, the oncolytic viruses tested so far are well tolerated, even in immune-suppressed patients. For most oncolytic viruses, mild and acceptable toxicities are seen at the currently defined highest feasible doses. However, anti-tumor efficacies of oncolytic viruses have been modest, especially when used as monotherapy. Therefore, the potency of oncolytic viruses needs to be enhanced for more oncolytic viruses to hit the clinic. Aiming to achieve higher therapeutic benefits, oncolytic viruses are currently being studied in combination with other therapies. Here we discuss the currently available clinical data on oncolytic viruses, either as monotherapy or in combination with other treatments.

Hepatocellular Carcinoma Immune Landscape and the Potential of Immunotherapies

Hepatocellular carcinoma (HCC) is the most common liver tumor and among the deadliest cancers worldwide. Advanced HCC overall survival is meager and has not improved over the last decade despite approval of several tyrosine kinase inhibitors (TKi) for first and second-line treatments. The recent approval of immune checkpoint inhibitors (ICI) has revolutionized HCC palliative care. Unfortunately, the majority of HCC patients fail to respond to these therapies. Here, we elaborate on the immune landscapes of the normal and cirrhotic livers and of the unique HCC tumor microenvironment. We describe the molecular and immunological classifications of HCC, discuss the role of specific immune cell subsets in this cancer, with a focus on myeloid cells and pathways in anti-tumor immunity, tumor promotion and immune evasion. We also describe the challenges and opportunities of immunotherapies in HCC and discuss new avenues based on harnessing the anti-tumor activity of myeloid, NK and γδ T cells, vaccines, chimeric antigen receptors (CAR)-T or -NK cells, oncolytic viruses, and combination therapies.

Safety, biodistribution and viral shedding of oncolytic vaccinia virus TG6002 administered intravenously in healthy beagle dogs

Oncolytic virotherapy is an emerging strategy that uses replication-competent viruses to kill tumor cells. We have reported the oncolytic effects of TG6002, a recombinant oncolytic vaccinia virus, in preclinical human xenograft models and canine tumor explants. To assess the safety, biodistribution and shedding of TG6002 administered by the intravenous route, we conducted a study in immune-competent healthy dogs. Three dogs each received a single intravenous injection of TG6002 at 105 PFU/kg, 106 PFU/kg or 107 PFU/kg, and one dog received three intravenous injections at 107 PFU/kg. The injections were well tolerated without any clinical, hematological or biochemical adverse events. Viral genomes were only detected in blood at the earliest sampling time point of one-hour post-injection at 107 PFU/kg. Post mortem analyses at day 35 allowed detection of viral DNA in the spleen of the dog which received three injections at 107 PFU/kg. Viral genomes were not detected in the urine, saliva or feces of any dogs. Seven days after the injections, a dose-dependent antibody mediated immune response was identified. In conclusion, intravenous administration of TG6002 shows a good safety profile, supporting the initiation of clinical trials in canine cancer patients as well as further development as a human cancer therapy.

Therapy in Advanced Hepatocellular Carcinoma

Treatment of advanced hepatocellular carcinoma (HCC) is challenging. Several randomized clinical trials are investigating the efficacy of systemic therapy, immunotherapy, and locoregional therapy as monotherapy or combined with other modalities in the treatment of HCC. Systemic therapy is the preferred treatment in advanced disease. To date, multiple first-line and second-line agents received Food and Drug Administration approval. For over a decade, sorafenib was the only first-line agent. In May 2020, combination of atezolizumab and bevacizumab has been approved as a first-line systemic regimen. Lenvatinib is another first-line agent that has multikinase activity. Second-line agents include cabozantinib, regorafenib, ramucirumab, and nivolumab. Adoptive cell transfer therapy is a highly specific immunotherapy that has shown antitumor activity against HCC. Oncolytic viruses are genetically modified viruses that infect cancer cells and induce apoptosis. Locoregional therapies such as transarterial chemoembolization and radioembolization have shown a potential benefit in selected patients with advanced HCC. In this review, we aim to summarize the treatment options available for advanced HCC.

Introducing immunotherapy for advanced hepatocellular carcinoma patients: Too early or too fast?

Advanced hepatocellular carcinoma (HCC) is the most frequent liver cancer. Immunotherapy has been explored in this disease in order to improve survival outcomes. Nowadays, scientific research is focusing especially on immune checkpoint inhibitors, in particular anti-PD1, anti-PD-L1 and anti-CTLA4 monoclonal antibodies (mAbs), as single-agent or in combination with other immunotherapy agents, target therapies, anti-vascular endothelial growth factor (VEGF) and other agents targeting specific molecular pathways. Other immunotherapy strategies have been assessed or are under investigation in advanced HCC, namely cytokines, adoptive cell therapy, oncolytic virus, cancer vaccines. Each treatment presents specific efficacy and toxicity profiles, strictly related to their mechanism of action and to advanced HCC tumour microenvironment (TME). The aim of this review is to outline the state-of-the-art of immunotherapy in advanced HCC treatment, highlighting data on already investigated treatment strategies, safety and toxicity (including HBV/HCV-related HCC), and ongoing clinical trials focusing on new promising therapeutic weapons.

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

The modulation relationship of genomic pattern of intratumor heterogeneity and immunity microenvironment heterogeneity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world, with the second highest mortality rate among all cancer types. Growing evidence has demonstrated the notable effects of intratumor heterogeneity (ITH) and tumor immune microenvironment heterogeneity (TIMH) on the biological processes involved in HCC. However, the interactive mechanisms between ITH and TIMH is still unclear. The present study systematically screened the mRNA expression, simple nucleotide variation data and clinical data of samples from The Cancer Genome Atlas (TCGA). The mutant-allele tumor heterogeneity (MATH) score was used to represent ITH, and TCGA cohort was divided into two groups according to the MATH score. Next, different immune-related signaling pathways and enriched immune-related genes were identified using Gene Set Enrichment Analysis of these two groups, and the results revealed that interleukin-1α (IL1A) and serine/threonine-protein kinase PAK4 were associated with prognosis. Furthermore, CIBERSORT was utilized to calculate the fractions of 22 types of leukocytes to represent TIMH, and the fractions of M1 and M2 macrophages were confirmed to be associated with prognosis. Therefore, PAK4, interleukin-1α (IL1A), and M1/M2 ratio were selected as the key factors involved in the interaction between ITH and TIMH. Afterwards, microRNAs (miRNAs) that were linearly related to the M1/M2 ratio and the potential target genes of the miRNAs were screened. Finally, the regulatory network between PAK4, IL1A, and the M1/M2 ratio was established, bridged by the above miRNAs and the target genes. In addition, PAK4, heat shock protein 105 kDa and miRNA-1911 were demonstrated to be a key factor involved in immune response via Weighted Correlation Network Analysis in HCC.

Immunotherapy of hepatocellular carcinoma with infection of hepatitis B or C virus

Hepatocellular carcinoma (HCC) has one of highest mortalities globally amongst cancers, but has limited therapeutic options once in the advanced stage. Hepatitis B or C virus infection are the most common drivers for HCC carcinogenesis, triggering chronic liver inflammation and adding to the complexity of the immune microecosystem of HCC. The emergence of immunotherapy has afforded a new avenue of therapeutic options for patients with advanced HCC with a history of hepatitis B or C virus infection. This article reviews the change of immunity elicited by hepatitis B or C virus infection, the immune feature of HCC, and the clinical evidence for immunotherapy in advanced HCC and discusses future directions in this field.

Dendritic Cell and T Cell Crosstalk in Liver Fibrogenesis and Hepatocarcinogenesis: Implications for Prevention and Therapy of Liver Cancer

Liver fibrosis is a chronic, highly prevalent disease that may progress to cirrhosis and substantially increases the risk for development of hepatocellular carcinoma (HCC). Fibrotic livers are characterized by an inflammatory microenvironment that is composed of various immunologically active cells, including liver-resident populations (e.g., Kupffer cells, hepatic stellate cells and sinusoidal endothelium) and infiltrating leukocytes (e.g., monocytes, monocyte-derived macrophages, neutrophils and lymphocytes). While inflammatory injury drives both fibrogenesis and carcinogenesis, the tolerogenic microenvironment of the liver conveys immunosuppressive effects that encourage tumor growth. An insufficient crosstalk between dendritic cells (DCs), the professional antigen presenting cells, and T cells, the efficient anti-tumor effector cells, is one of the main mechanisms of HCC tumor tolerance. The meticulous analysis of patient samples and mouse models of fibrosis-HCC provided in-depth insights into molecular mechanisms of immune interactions in liver cancer. The therapeutic modulation of this multifaceted immunological response, e.g., by inhibiting immune checkpoint molecules, in situ vaccination, oncolytic viruses or combinations thereof, is a rapidly evolving field that holds the potential to improve the outcome of patients with HCC. This review aims to highlight the current understanding of DC–T cell interactions in fibrogenesis and hepatocarcinogenesis and to illustrate the potentials and pitfalls of therapeutic clinical translation.

Immunotherapy for Hepatocellular Carcinoma: A 2021 Update

Hepatocellular carcinoma (HCC) is one of one of the most frequent liver cancers and the fourth leading cause of cancer-related mortality worldwide. Current treatment options such as surgery, neoadjuvant chemoradiotherapy, liver transplantation, and radiofrequency ablation will benefit only a very small percentage of patients. Immunotherapy is a novel treatment approach representing an effective and promising option against several types of cancer. The aim of our study is to present the currently ongoing clinical trials and to evaluate the efficacy of immunotherapy in HCC. In this paper, we demonstrate that combination of different immunotherapies or immunotherapy with other modalities results in better overall survival (OS) and progression-free survival (PFS) compared to single immunotherapy agent. Another objective of this paper is to demonstrate and highlight the importance of tumor microenvironment as a predictive and prognostic marker and its clinical implications in immunotherapy response.

Combining oncolytic virus with FDA approved pharmacological agents for cancer therapy

INTRODUCTION

Oncolytic viruses (OVs) have been engineered to selectively replicate in cancer cells. While initially thought to exert its anti-cancer effects through direct cytolysis, it is increasingly appreciated that OVs interact with a multitude of cellular processes during its life cycle; FDA approved pharmacologic agents that modulate these cellular processes have been shown to augment the anti-neoplastic effects of OVs. Moreover, because of the release of tumor antigens as well as the innate immuno-stimulatory nature of viruses, OVs induce potent immune responses that augment the anti-tumor effects of FDA approved immunotherapies. There is mounting interest in OV as a platform for combinational anti-cancer therapy in this context.

AREAS COVERED

We will review pre-clinical and clinical data that demonstrate proof-of-principle and potential efficacy for OV-based combination therapies with FDA approved anti-cancer agents.

EXPERT OPINION

While the cytolytic activity of OV remains a key driver for its anti-neoplastic effects, understanding the virus-host interactions may afford opportunities for potential synergism with FDA approved therapeutics that target these interactions. Most intriguingly, the immune stimulatory effects of OVs renders combination with FDA approved immunotherapies more potent. While there are growing clinical trials employing such combination therapy, meaningful advances in this paradigm will require improved understanding of virus-host interactions.

Recombinant viruses delivering the necroptosis mediator MLKL induce a potent antitumor immunity in mice

Vaccinia viruses (VACV) are a novel class of immune-oncolytic therapeutics and their mechanism of action is based both on their capacity to replicate selectively in cancer cells and to elicit danger signals that can boost anti-tumor immunity. We recently reported that the intratumor expression of MLKL, a necroptosis inducing factor, generates a protective anti-tumor immunity. Here, we combined both approaches to test the use of VACV to deliver MLKL into the tumor. We generated VACV vectors expressing MLKL and evaluated the effects of MLKL on antitumor efficacy. In vitro infection of cancer cells with MLKL-expressing vectors led to cell death with necroptotic hallmarks. In syngeneic mouse tumor models, VACV expressing MLKL induced an outstanding antitumor activity, which was associated with a robust immunity directed against neo-epitopes. In conclusion, delivery of MLKL by VACV vectors boosts the intrinsic anti-tumor properties of these viral vectors by promoting in situ immunogenic cell death of infected cancer cells.

Multidirectional Strategies for Targeted Delivery of Oncolytic Viruses by Tumor Infiltrating Immune Cells

Oncolytic virus (OV) immunotherapy has demonstrated to be a promising approach in cancer treatment due to tumor-specific oncolysis. However, their clinical use so far has been largely limited due to the lack of suitable delivery strategies with high efficacy. Direct 'intratumoral' injection is the way to cross the hurdles of systemic toxicity, while providing local effects. Progress in this field has enabled the development of alternative way using 'systemic' oncolytic virotherapy for producing better results. One major potential roadblock to systemic OV delivery is the low virus persistence in the face of hostile immune system. The delivery challenge is even greater when attempting to target the oncolytic viruses into the entire tumor mass, where not all tumor cells are equally exposed to exactly the same microenvironment. The microenvironment of many tumors is known to be massively infiltrated with various types of leucocytes in both primary and metastatic sites. Interestingly, this intratumoral immune cell heterogeneity exhibits a degree of organized distribution inside the tumor bed as evidenced, for example, by the hypoxic tumor microenviroment where predominantly recruits tumor-associated macrophages. Although in vivo OV delivery seems complicated and challenging, recent results are encouraging for decreasing the limitations of systemically administered oncolytic viruses and an improved efficiency of oncolytic viral therapy in targeting cancerous tissues in vitro. Here, we review the latest developments of carrier cell-based oncolytic virus delivery using tumor-infiltrating immune cells with a focus on the main features of each cellular vehicle.

Efficacy and Safety of Oncolytic Viruses in Randomized Controlled Trials: A Systematic Review and Meta-Analysis

Oncolytic virotherapy is a promising antitumor therapeutic strategy. It is based on the ability of viruses to selectively kill cancer cells and induce host antitumor immune responses. However, the clinical outcomes of oncolytic viruses (OVs) vary widely. Therefore, we performed a meta-analysis to illustrate the efficacy and safety of oncolytic viruses. The Cochrane Library, PubMed, and EMBASE databases were searched for randomized controlled trials (RCTs) published up to 31 January 2020. The data for objective response rate (ORR), overall survival (OS), progression-free survival (PFS), and adverse events (AEs) were independently extracted by two investigators from 11 studies that met the inclusion criteria. In subgroup analyses, the objective response rate benefit was observed in patients treated with oncolytic DNA viruses (odds ratio (OR) = 4.05; 95% confidence interval (CI): 1.96–8.33; p = 0.0002), but not in those treated with oncolytic RNA viruses (OR = 1.00, 95% CI: 0.66–1.52, p = 0.99). Moreover, the intratumoral injection arm yielded a statistically significant improvement (OR = 4.05, 95% CI: 1.96–8.33, p = 0.0002), but no such improvement was observed for the intravenous injection arm (OR = 1.00, 95% CI: 0.66–1.52, p = 0.99). Among the five OVs investigated in RCTs, only talimogene laherparepvec (T-VEC) effectively prolonged the OS of patients (hazard ratio (HR), 0.79; 95% CI: 0.63–0.99; p = 0.04). None of the oncolytic virotherapies improved the PFS (HR = 1.00, 95% CI: 0.85–1.19, p = 0.96). Notably, the pooled rate of severe AEs (grade ≥3) was higher for the oncolytic virotherapy group (39%) compared with the control group (27%) (risk difference (RD), 12%; risk ratio (RR), 1.44; 95% CI: 1.17–1.78; p = 0.0006). This review offers a reference for fundamental research and clinical treatment of oncolytic viruses. Further randomized controlled trials are needed to verify these results.

Heterogeneous responses in hepatocellular carcinoma: the achilles heel of immune checkpoint inhibitors

Treatment of patients with hepatocellular carcinoma (HCC) remains a serious challenge due to high heterogeneity and limited treatment options. In the past few decades, immune therapy, especially immune checkpoint therapy, has become an alternative option for the treatment of malignancies including HCC. Immune checkpoint inhibitors (ICIs) have raised attention because of their significant antitumor effect and low toxicity. However, such immunotherapy fails to be responsive in a major proportion of patients with HCC. Recent studies suggest that failures in antigen presentation, an impaired immune microenvironment, alterations in immune checkpoint molecules and immune-suppressive cells are responsible for the heterogeneous responses and resistance. Based on the specific characteristics above, we proposed a model stratifying patients with HCC into two subtypes that could predict response or resistance to ICI. Furthermore, supplementing ICIs with agents targeting the microenvironment could achieve an increased response rate, which is a step forward in precision treatment for HCC. In addition, emerging studies have revealed that liver transplantation, epigenetic drugs and other novel strategies also provide synergistic effects with ICIs in the treatment of HCC.

mRECIST for HCC: Performance and novel refinements

In 2010, modified RECIST (mRECIST) criteria were proposed as a way of adapting the RECIST criteria to the particularities of hepatocellular carcinoma (HCC). We intended to overcome some limitations of RECIST in measuring tumour shrinkage with local and systemic therapies, and also to refine the assessment of progression that could be misinterpreted with conventional RECIST 1.1, due to clinical events related to the natural progression of chronic liver disease (development of ascites, enlargement of lymph nodes, etc.). mRECIST has served its purpose since being adopted or included in clinical practice guidelines (European, American and Asian) for the management of HCC; it has also been instrumental for assessing response and time-to-event endpoints in several phase II and III investigations. Nowadays, mRECIST has become the standard tool for measurement of radiological endpoints at early/intermediate stages of HCC. At advanced stages, guidelines recommend both methods. mRECIST has been proven to capture higher objective response rates in tumours treated with molecular therapies and those responses have shown to be independently associated with better survival. With the advent of novel treatment approaches (i.e. immunotherapy) and combination therapies there is a need to further refine and clarify some concepts around the performance of mRECIST. Similarly, changes in the landscape of standard of care at advanced stages of the disease are pointing towards progression-free survival as a potential primary endpoint in some phase III investigations, as effective therapies applied beyond progression might mask overall survival results. Strict recommendations for adopting this endpoint have been reported. Overall, we review the performance of mRECIST during the last decade, incorporating novel clarifications and refinements in light of emerging challenges in the study and management of HCC.

Systemic Therapy for Hepatocellular Carcinoma: Advances and Hopes

The majority of patients with hepatocellular carcinoma (HCC) are diagnosed at an advanced stage that can only benefit from systemic treatments. Although HCC is highly treatmentresistant, significant achievements have been made in the molecular targeted therapy and immunotherapy of HCC. In addition to regorafenib, cabozantinib and ramucirumab were approved for the second- line targeted treatment by the FDA after disease progression on sorafenib. Nivolumab failed to demonstrate remarkable benefit in overall survival (OS) as first-line therapy, while pembrolizumab did not achieve pre-specified statistical significance in both OS and progression-free survival (PFS) as second-line treatment. Combinations of targeted agents, immune checkpoint inhibitors and other interventions showed favorable results. In this review, we summarized the progress of systemic therapy in HCC and discussed the future directions of the treatment of HCC.

Design and application of oncolytic viruses for cancer immunotherapy

The approval of the first oncolytic virus (OV) for the treatment of metastatic melanoma and the recent discovery that the use of oncolytic viruses may enhance cancer immunotherapies targeted against various immune checkpoint proteins have attracted great interest in the field of cancer virotherapy. OVs are designed to target and kill cancer cells leaving normal cell unharmed. OV infection and concomitant cancer cell killing stimulate anti-tumour immunity and modulates tumour microenvironment towards less immunosuppressive phenotype. The intrinsic capacity of OVs to turn immunologically cold tumours into immunologically hot tumours, and to increase immune cell and cytokine infiltration, can be further enhanced by arming OVs with transgenes that increase their immunostimulatory activities and direct immune responses specifically towards cancer cells. These OVs, specifically engineered to be used as cancer immunotherapeutics, can be synergized with other immune modulators or cytotoxic agents to achieve the most potent immunotherapy for cancer.

Tackling hepatocellular carcinoma with individual or combinatorial immunotherapy approaches

Hepatocellular carcinoma (HCC) is the third leading cause of death from cancer globally. Indeed, there is a single drug approved as first-line systemic therapy in advanced unresectable HCC, providing a very limited survival benefit. In earlier stages, 5-year survival rates after surgical and loco-regional therapies are extremely variable depending on the stage of disease. Nevertheless, HCC is considered an immunogenic tumor arising in chronically inflamed livers. In such a scenario, immunotherapy strategies for HCC, in particular combinations including cancer vaccines, may represent a key therapeutic tool to improve clinical outcome in HCC patients. However, a lot of improvement is needed given the disappointing results obtained so far.

Recent advances in oncolytic virus-based cancer therapy

Administration of oncolytic viruses (OVs) is an emerging anticancer strategy that exploits the lytic nature of viral replication to enhance the killing of malignant cells. OVs can be used as tools to directly induce cancer cell death and to trigger local and/or systemic immune responses to metastatic cancer in vivo. The effectiveness of OV therapy was initially highlighted by the clinical use of the genetically modified herpes virus, talimogene laherparepvec, for melanoma therapy. A number of OVs are now being evaluated as potential treatments for cancer in clinical trials. In spite of being engineered to specifically target tumor cells, the safety and off-target effects of OV therapy are a concern. The potential safety concerns of OVs are highlighted by current clinical trial criteria, which exclude individuals harbouring other viral infections and people who are immunocompromised. Despite the potential for adverse effects, clinical trials to date revealed relatively minimal adverse immune-related effects, such as fever. With advances in our understanding of virus replication cycles, several novel OVs have emerged. Reverse genetic systems have facilitated the insertion of anticancer genes into a range of OVs to further enhance their tumor-killing capacity. In this review, we highlight the recent advances in OV therapy for a range of human cancers in in vitro and in in vivo animal studies. We further discuss the future of OVs as a therapeutic strategy for a range of life-threatening cancers.