Molecular Pathways: Mechanism of Action for Talimogene Laherparepvec, a New Oncolytic Virus Immunotherapy

The safety of talimogene laherparepvec for the treatment of advanced melanoma

INTRODUCTION

Talimogene laherparepvec (T-VEC, IMLYGIC) is an oncolytic herpes virus type I used as intralesional therapy for the treatment of unresectable metastatic melanoma in a cutaneous, subcutaneous, or nodal location. Talimogene laherparepvec selectively replicates within and lyses tumor cells while producing granulocyte macrophage colony-stimulating factor (GM-CSF), which may promote an immune mediated antitumor response. Areas covered: The US Food and Drug Administration approved Talimogene laherparepvec in late 2015 following the completion of phase I, II and III trials that demonstrated safety and efficacy. Current NCCN practice guidelines have added Talimogene laherparepvec as a primary treatment for stage IIIB/C and stage IVM1a melanoma patients with evidence of good durable response rates, and this article sets out to review the use and safety and efficacy of T-VEC Expert opinion: Treatment options for locally advanced and metastatic melanoma are expanding with new developments in immunotherapy and immune checkpoint inhibitors. The ideal treatment of metastatic melanoma continues to be multimodal, combining systemic treatments, intralesional and regional therapies, surgery and radiotherapy to achieve optimal outcomes. Use of talimogene laherparepvec as intrelsional therapy has demonstrated promising effects in select patients with advanced melanoma. Future directions for Talimogene laherparepvec include combination therapies with other systemic immunotherapies such as anti-CTLA-4 antibody and anti-PD-1 drugs.

Adaptive T cell responses induced by oncolytic Herpes Simplex Virus-granulocyte macrophage-colony-stimulating factor therapy expanded by dendritic cell and cytokine-induced killer cell adoptive therapy

Purpose: Although local oncolytic viral therapy (OVT) may enhance tumor lysis, antigen release, and adaptive immune responses, systemic antitumor responses post-therapy are limited. Adoptive immunotherapy with autologous dendritic cells (DC) and cytokine-induced killer cells (DC-CIK) synergizes with systemic therapies. We hypothesized that OVT with Herpes Simplex Virus-granulocyte macrophage-colony-stimulating factor (HSV-GM-CSF) would induce adaptive T cell responses that could be expanded systemically with sequential DC-CIK therapy. Patients and Methods: We performed a pilot study of intratumoral HSV-GM-CSF OVT followed by autologous DC-CIK cell therapy. In addition to safety and clinical endpoints, we monitored adaptive T cell responses by quantifying T cell receptor (TCR) populations in pre-oncolytic therapy, post-oncolytic therapy, and after DC-CIK therapy. Results: Nine patients with advanced malignancy were treated with OVT (OrienX010), of whom seven experienced stable disease (SD). Five of the OVT treated patients underwent leukapheresis, generation, and delivery of DC-CIKs, and two had SD, whereas three progressed. T cell receptor sequencing of TCR β sequences one month after OVT therapy demonstrates a dynamic TCR repertoire in response to OVT therapy in the majority of patients with the systematic expansion of multiple T cell clone populations following DC-CIK therapy. This treatment was well tolerated and long-term event free and overall survival was observed in six of the nine patients. Conclusions: Strategies inducing the local activation of tumor-specific immune responses can be combined with adoptive cellular therapies to expand the adaptive T cell responses systemically and further studies are warranted.

Spotlight on talimogene laherparepvec for the treatment of melanoma lesions in the skin and lymph nodes

On October 27, 2015, talimogene laherparepvec (T-VEC), a first in class intralesional oncolytic virotherapy, was granted the US Food and Drug Administration approval for the treatment of melanoma in the skin and lymph nodes. Its approval has added yet another therapeutic option to the growing list of effective therapies for melanoma. Though the Phase III OPTiM trial has demonstrated its efficacy as a single agent, the target patient population remains narrow. With numerous effective and tolerable treatments available for unresectable and metastatic melanoma, intralesional therapies such as T-VEC are still finding their niche. T-VEC is now widely accepted as option for treatment; however, its combination with various other agents in an effort to expand its use and synergize with other interventions is still being explored. This article will review the pre-clinical and clinical work that eventually led to the Food and Drug Administration approval of this first-in-class agent, as well as address concerns about clinical application and ongoing research.

Oncolytic viruses against cancer stem cells: A promising approach for gastrointestinal cancer

Gastrointestinal cancer has been one of the five most commonly diagnosed and leading causes of cancer mortality over the past few decades. Great progress in traditional therapies has been made, which prolonged survival in patients with early cancer, yet tumor relapse and drug resistance still occurred, which is explained by the cancer stem cell (CSC) theory. Oncolytic virotherapy has attracted increasing interest in cancer because of its ability to infect and lyse CSCs. This paper reviews the basic knowledge, CSC markers and therapeutics of gastrointestinal cancer (liver, gastric, colon and pancreatic cancer), as well as research advances and possible molecular mechanisms of various oncolytic viruses against gastrointestinal CSCs. This paper also summarizes the existing obstacles to oncolytic virotherapy and proposes several alternative suggestions to overcome the therapeutic limitations.

Immunotherapy in melanoma: Recent advances and future directions

Malignant melanoma contributes the majority of skin cancer related deaths and shows an increasing incidence in the past years. Despite all efforts of early diagnosis, metastatic melanoma still has a poor prognosis and remains a challenge for treating physicians. In recent years, improved knowledge of the pathophysiology and a better understanding of the role of the immune system in tumour control have led to the development and approval of several immunotherapies. Monoclonal antibodies against different immune checkpoints have been revolutionizing the treatment of metastatic and unresectable melanoma. Ipilimumab, a monoclonal antibody against the cytotoxic T-lymphocyte antigen 4 (CTLA-4) as well as nivolumab and pembrolizumab which target the programmed cell death protein 1 (PD-1) have been shown to prolong overall survival in patients with advanced melanoma. The latter substances seem to have an increased response rate and more tolerable safety profile compared to ipilimumab. The combination of a CTLA-4 and a PD-1 inhibitor seems to be superior to the monotherapies, especially in patients with PD-L1 negative tumours. Checkpoint inhibitors are currently being tested in the adjuvant setting with initial data for ipilimumab suggesting efficacy in this context. Talimogene laherparepvec (TVEC) is the first oncolytic virus approved in the therapy of metastatic melanoma offering a treatment option especially for patients with limited disease. In this review, data on these recently developed and approved immunotherapies are presented. However, further studies are necessary to determine the optimal duration, sequencing and combinations of immunotherapies to further improve the outcome of patients with advanced melanoma.

Oncolytic viruses-immunotherapeutics on the rise

The oncolytic virus (OV) field has entered an exciting period in its evolution in which our basic understanding of viral biology and anti-cancer potential are being actively translated into viable therapeutic options for aggressive malignancies. OVs are naturally occurring or engineered viruses that are able to exploit cancer-specific changes in cellular signaling to specifically target cancers and their microenvironment. The direct cytolytic effect of OVs on cancer cells is known to release antigens, which can begin a cascade of events that results in the induction of anti-cancer adaptive immunity. This response is now regarded as the most critical mechanism of OV action and harnessing it can lead to the elimination of distant micrometastases as well as provide long-term anti-cancer immune surveillance. In this review, we highlight the development of the OV field, why OVs are gaining an increasingly elevated standing as members of the cancer immunotherapy armamentarium, and finally, ongoing clinical studies that are aimed at translating unique OV therapies into approved therapies for aggressive cancers.

Immunotherapy for head and neck squamous cell carcinoma

Over the past years immuno-oncology has evolved and become a novel promising strategy for cancer therapy. Immune checkpoint inhibitors such as pembrolizumab or nivolumab, which target the interaction between programmed death receptor 1/programmed death ligand 1 (PD-1/PDL-1) and PDL-2, have been recently approved for the treatment of various malignancies and are currently being investigated in clinical phase III trials for head and neck squamous cell carcinoma (HNSCC). Data available from these trials indicate substantial activity accompanied by a favorable safety and toxicity profile in this patient population. This review article focuses on the molecular background, gives an overview of current clinical data of checkpoint inhibitors in HNSCC, and points out future challenges such as the need for appropriate biomarkers for these novel compounds.