Bio-distribution study of Reolysin® (pelareorep) through a single intravenous infusion in Sprague-Dawley rats

Small extracellular vesicles carrying reovirus, tumor antigens, interferon-β, and damage-associated molecular patterns for efficient tumor treatment

Small extracellular vesicles (SEV) have attracted much attention both as mediators of intercellular communication and as drug delivery systems. In addition, recent studies have shown that SEV containing virus components and virus particles are released from virus-infected cells. Oncolytic viruses, which efficiently kill tumor cells by tumor cell-specific replication, have been actively studied as novel anticancer agents in clinical and preclinical studies. However, it remains to be fully elucidated whether SEV released from oncolytic virus-infected cells are involved in the antitumor effects of oncolytic viruses. In this study, we examined the tumor cell killing efficiencies and innate immune responses following treatment with SEV released from oncolytic reovirus-infected tumor cells in vitro and in vivo. Reovirus-infected B16 cells secreted SEV associated with or containing reovirus particles (Reo-SEV) with a diameter of approximately 130 nm and a zeta potential of -17 mV, although death of reovirus-infected B16 cells was not observed. The secreted Reo-SEV also contained interferon (IFN)-β, tumor antigens, and damage-associated molecular patterns (DAMPs), including heat shock proteins (HSPs). Reo-SEV were secreted from the tumor tissues of reovirus-injected mice. Inhibition of the SEV secretion pathway using GW4869, which is a neutral sphingomyelinase inhibitor, resulted in significant reduction in the infectious titers of reovirus in the culture supernatants, suggesting that the cells released progeny virus via the SEV secretion pathway. Reo-SEV more efficiently killed mouse tumor cells and induced innate immune responses in mouse bone marrow-derived dendritic cells than reovirus. Reovirus and Reo-SEV mediated efficient and comparable levels of growth suppression of B16 subcutaneous tumors and induction of tumor infiltration of CD8+ T cells following intravenous administration. These results indicate that Reo-SEV are a promising oncolytic agent and that SEV are an effective delivery vehicle for oncolytic virus.

Bifidobacterium infantis-Mediated Herpes Simplex Virus-TK/Ganciclovir Treatment Inhibits Cancer Metastasis in Mouse Model

Previous studies have found that Bifidobacterium infantis-mediated herpes simplex virus-TK/ganciclovir (BF-TK/GCV) reduces the expression of VEGF and CD146, implying tumor metastasis inhibition. However, the mechanism by which BF-TK/GCV inhibits tumor metastasis is not fully studied. Here, we comprehensively identified and quantified protein expression profiling for the first time in gastric cancer (GC) cells MKN-45 upon BF-TK/GCV treatment using quantitative proteomics. A total of 159 and 72 differential expression proteins (DEPs) were significantly changed in the BF-TK/GCV/BF-TK and BF-TK/GCV/BF/GCV comparative analysis. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis enriched some metastasis-related pathways such as gap junction and cell adhesion molecules pathways. Moreover, the transwell assay proved that BF-TK/GCV inhibited the invasion and migration of tumor cells. Furthermore, immunohistochemistry (IHC) demonstrated that BF-TK/GCV reduced the expression of HIF-1α, mTOR, NF-κB1-p105, VCAM1, MMP13, CXCL12, ATG16, and CEBPB, which were associated with tumor metastasis. In summary, BF-TK/GCV inhibited tumor metastasis, which deepened and expanded the understanding of the antitumor mechanism of BF-TK/GCV.

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.

Infection of non-cancer cells: A barrier or support for oncolytic virotherapy?

Oncolytic viruses are designed to specifically target cancer cells, sparing normal cells. Although numerous studies demonstrate the ability of oncolytic viruses to infect a wide range of non-tumor cells, the significance of this phenomenon for cancer virotherapy is poorly understood. To fill the gap, we summarize the data on infection of non-cancer targets by oncolytic viruses with a special focus on tumor microenvironment and secondary lymphoid tissues. The review aims to address two major questions: how do attenuated viruses manage to infect normal cells, and whether it is of importance for oncolytic virotherapy.

Current understanding of reovirus oncolysis mechanisms

Mammalian orthoreovirus (reovirus) is under development as a cancer virotherapy. Clinical trials demonstrate that reovirus-based therapies are safe and tolerated in patients with a wide variety of cancers. Although reovirus monotherapy has proven largely ineffective, reovirus sensitizes cancer cells to existing chemotherapeutic agents and radiation. Clinical trials are underway to test the efficacy of reovirus in combination with chemotherapeutic and radiation regimens and to evaluate the effectiveness of reovirus in conjunction with immunotherapies. Central to the use of reovirus to treat cancer is its capacity to directly kill cancer cells and alter the cellular environment to augment other therapies. Apoptotic cell death is a prominent mechanism of reovirus cancer cell killing. However, reoviruses can also kill cancer cells through nonapoptotic mechanisms. Here, we describe mechanisms of reovirus cancer cell killing, highlight how reovirus is used in combination with existing cancer treatments, and discuss what is known as to how reovirus modulates cancer immunotherapy.

The oncolytic virus, pelareorep, as a novel anticancer agent: a review

Pelareorep (REOLYSIN®) is an investigational new drug, a proprietary formulation consisting of a live, replication-competent, naturally occurring Reovirus Type 3 Dearing strain. Through several preclinical studies it was determined that reovirus can exhibit profound cytotoxic effects on cancer cells predominantly with an activated RAS-signalling pathway. Moreover, it was discovered that reoviruses can "hitchhike" on peripheral blood mononuclear cells and dendritic cells, thereby evading neutralizing antibodies of the host immune system. Cell carriage, targeted delivery, triggering host immune response and other inherent characteristics of the reovirus led to its further advancement into cancer therapy. When injected into Sprague-Dawley rats, the viral routes of clearance, predominantly through the spleen and liver, remained consistent with earlier studies. Toxicology findings were considered incidental and not associated with pelareorep when tested in animal models. Pelareorep demonstrated a high level of homogeneity at the amino acid level and genetic stability when compared to the master and working virus banks. The drug is manufactured in a 100 L bioreactor after which it is purified and formulated for use in pre-clinical, clinical and research studies. Over the past few decades, we have witnessed a paradigm shift from conventional therapy to the conceivable use of oncolytic viruses for the treatment of cancer. This review will detail pre-clinical evidence of anticancer activity of pelareorep that has led to extensive clinical development. Several Phase I-II clinical trials have been completed or are ongoing in cancer patients on a broad spectrum of solid tumors and hematologic malignancies.