Thrombotic microangiopathy following systemic AAV administration is dependent on anti-capsid antibodies.

BACKGROUNDSystemic administration of adeno-associated virus (AAV) can trigger life-threatening inflammatory responses, including thrombotic microangiopathy (TMA), acute kidney injury due to atypical hemolytic uremic syndrome-like complement activation, immune-mediated myocardial inflammation, and hepatic toxicity.METHODSWe describe the kinetics of immune activation following systemic AAV serotype 9 (AAV9) administration in 38 individuals following 2 distinct prophylactic immunomodulation regimens. Group 1 received corticosteroids and Group 2 received rituximab plus sirolimus in addition to steroids to prevent anti-AAV antibody formation.RESULTSGroup 1 participants had a rapid increase in immunoglobulin M (IgM) and IgG. Increase in D-dimer, decline in platelet count, and complement activation are indicative of TMA. All Group 1 participants demonstrated activation of both classical and alternative complement pathways, as indicated by depleted C4 and elevated soluble C5b-9, Ba, and Bb antigens. Group 2 patients did not have a significant change in IgM or IgG and had minimal complement activation.CONCLUSIONSThis study demonstrates that TMA in the setting of AAV gene therapy is antibody dependent (classical pathway) and amplified by the alternative complement pathway. Critical time points and interventions are identified to allow for management of immune-mediated events that impact the safety and efficacy of systemic gene therapy.

Safety and Efficacy of Outpatient Drainless Abdominoplasty: A Single-Surgeon Experience of 454 Consecutive Patients.

BACKGROUND: The incidence of seroma after abdominoplasty is accepted as approximately 10% (with a range) in the literature. Progressive tension sutures (PTS) have arisen as a means of reducing seroma, however there are conflicting data regarding their efficacy. OBJECTIVES: The primary aim of this study was to describe the incidence of postabdominoplasty seroma in the setting of drainless abdominoplasty with PTS. METHODS: A retrospective chart review was performed of all abdominoplasties (n = 454) during a 20-year period. At approximately the halfway point of this time frame, the abdominoplasty technique was changed from the use of 2 drains to the use of PTS without drains. Additionally, pulsed electromagnetic field therapy (PEMF) and liposomal bupivacaine (Exparel, Pacira Pharmaceuticals, Inc., Parsippany, NJ) were added as pain control adjuncts. RESULTS: There were 194 patients in the drain group and 260 patients in the PTS/no drains group. The group without drains contained a significantly higher proportion of massive weight loss patients (4.1% vs 9.2%, P = .041). The majority of the group without drains underwent outpatient surgery (89.7% vs 98.8%, P < .001). The overall complication rate was significantly lower in the no drains group (31.4% vs 13.8%, P < .001). The incidence of seroma was dramatically reduced in the group without drains (24.7% vs 0.0%, P < .001). CONCLUSIONS: PTS are highly effective in preventing seroma and can be safely employed as an alternative to drains in abdominoplasty. PEMF may play a role in seroma prevention and is also helpful for pain control. With these techniques to mitigate complications and minimize postoperative pain, abdominoplasty can be performed safely and effectively in a purely outpatient setting.

Oncolytic Vaccinia Virus Gene Modification and Cytokine Expression Effects on Tumor Infection, Immune Response, and Killing.

Oncolytic vaccinia viruses have promising efficacy and safety profiles in cancer therapy. Although antitumor activity can be increased by manipulating viral genes, the relative efficacy of individual modifications has been difficult to assess without side-by-side comparisons. This study sought to compare the initial antitumor activity after intravenous administration of five vaccinia virus variants of the same Western Reserve backbone and thymidine kinase gene deletion in RIP-Tag2 transgenic mice with spontaneous pancreatic neuroendocrine tumors. Tumors had focal regions of infection at 5 days after all viruses. Natural killer (NK) cells were restricted to these sites of infection, but CD8+ T cells and tumor cell apoptosis were widespread and varied among the viruses. Antitumor activity of virus VV-A34, bearing amino acid substitution A34K151E to increase viral spreading, and virus VV-IL2v, expressing a mouse IL2 variant (mIL2v) with attenuated IL2 receptor alpha subunit binding, was similar to control virus VV-GFP. However, antitumor activity was significantly greater after virus VV-A34/IL2v, which expressed mIL2v together with A34K151E mutation and viral B18R gene deletion, and virus VV-GMCSF that expressed mouse GM-CSF. Both viruses greatly increased expression of CD8 antigens Cd8a/Cd8b1 and cytotoxicity genes granzyme A, granzyme B, Fas ligand, and perforin-1 in tumors. VV-A34/IL2v led to higher serum IL2 and greater tumor expression of death receptor ligand TRAIL, but VV-GMCSF led to higher serum GM-CSF, greater expression of leukocyte chemokines and adhesion molecules, and more neutrophil recruitment. Together, the results show that antitumor activity is similarly increased by viral expression of GM-CSF or IL2v combined with additional genetic modifications.

Quantification of RPE Changes in Choroideremia Using a Photoshop-Based Method.

Purpose: To develop a reliable and efficient method for quantifying the area of preserved retinal pigment epithelium (RPE), facilitating the evaluation of disease progression or response to therapy in choroideremia (CHM). Methods: The fundus autofluorescence images of CHM patients were captured at baseline and 1 year. A Photoshop-based method was developed to allow the reliable measurement of the RPE area. The results were compared with measurements generated by the Heidelberg Eye Explorer 2 (HEYEX2). The areas measured by two independent graders were compared to assess the test-retest reliability. Results: By using the Photoshop-based method, the area of the RPE measured from 64 eyes was seen to decrease significantly (P < 0.001) at a rate of 2.57 ± 3.22 mm2 annually, and a percentage of 8.39% ± 5.24%. The average standard deviations for Photoshop were less than that for HEYEX2 (0.5-1.1 in grader 1; 0.4-1.6 in grader 2), indicating less intragrader variability. The RPE decrease as determined by the Photoshop-based method showed excellent reliability with an intraclass correlation coefficient of 0.944 (95% confidence interval, 0.907-0.966). In Bland-Altman plots, the Photoshop method also exhibited better intergrader agreement. Conclusions: Photoshop-based quantification of preserved RPE area in patients with CHM is feasible and has better test-retest reliability compared with the HEYEX2 method. Translational Relevance: An accurate quantification method for longitudinal RPE change in CHM patients is an important tool for the evaluation of efficacy in any therapeutic trials.

Amplification of Oncolytic Vaccinia Virus Widespread Tumor Cell Killing by Sunitinib through Multiple Mechanisms.

Oncolytic viruses pose many questions in their use in cancer therapy. In this study, we assessed the potential of mpJX-594 (mouse-prototype JX-594), a replication-competent vaccinia virus administered by intravenous injection, to target the tumor vasculature, produce immune activation and tumor cell killing more widespread than the infection, and suppress invasion and metastasis. These actions were examined in RIP-Tag2 transgenic mice with pancreatic neuroendocrine tumors that developed spontaneously and progressed as in humans. mpJX-594 initially infected tumor vascular endothelial cells, leading to vascular pruning and prolonged leakage in tumors but not in normal organs; parallel effects were observed in U87 gliomas. Viral infection spread to tumor cells, where tumor cell killing was much more widespread than the infection. Widespread tumor cell killing at 5 days was prevented by depletion of CD8+ T lymphocytes and did not require GM-CSF, as mpJX-594 variants that expressed human, mouse, or no GM-CSF produced equivalent amounts of killing. The antivascular, antitumor, and antimetastatic effects of mpJX-594 were amplified by concurrent or sequential administration of sunitinib, a multitargeted receptor tyrosine kinase inhibitor. These effects were not mimicked by selective inhibition of VEGFR2 despite equivalent vascular pruning, but were accompanied by suppression of regulatory T cells and greater influx of activated CD8+ T cells. Together, our results showed that mpJX-594 targets tumor blood vessels, spreads secondarily to tumor cells, and produces widespread CD8+ T-cell-dependent tumor cell killing in primary tumors and metastases, and that these effects can be amplified by coadministration of sunitinib.Significance: These findings reveal multiple unrecognized features of the antitumor properties of oncolytic vaccinia viruses, all of which can be amplified by the multitargeted kinase inhibitor sunitinib. Cancer Res; 78(4); 922-37. ©2017 AACR.

VEGF-Mediated Induction of PRD1-BF1/Blimp1 Expression Sensitizes Tumor Vasculature to Oncolytic Virus Infection.

Oncolytic viruses designed to attack malignant cells can in addition infect and destroy tumor vascular endothelial cells. We show here that this expanded tropism of oncolytic vaccinia virus to the endothelial compartment is a consequence of VEGF-mediated suppression of the intrinsic antiviral response. VEGF/VEGFR2 signaling through Erk1/2 and Stat3 leads to upregulation, nuclear localization, and activation of the transcription repressor PRD1-BF1/Blimp1. PRD1-BF1 does not contribute to the mitogenic effects of VEGF, but directly represses genes involved in type I interferon (IFN)-mediated antiviral signaling. In vivo suppression of VEGF signaling diminishes PRD1-BF1/Blimp1 expression in tumor vasculature and inhibits intravenously administered oncolytic vaccinia delivery to and consequent spread within the tumor.

A Phase 2, Open-Label, Randomized Study of Pexa-Vec (JX-594) Administered by Intratumoral Injection in Patients with Unresectable Primary Hepatocellular Carcinoma.

Primary liver cancer (hepatocellular carcinoma; HCC) in patients not eligible for surgery or transplant is currently treated by locoregional therapeutic approaches, including trans-arterial chemoembolization and radiofrequency ablation. Sorafenib (Nexavar; Bayer/Onyx) is currently the only approved systemic therapy for patients having failed locoregional interventions. Oncolytic viruses are designed to selectively replicate within, and subsequently lyse, cancer cells by a unique mechanisms-of-action that is not cross-resistant with approved therapies (Kirn et al., Nat Med 7:781-787, 2001; Parato et al., Nat Rev Cancer 5:965-976, 2005; Chiocca, Nat Rev Cancer 2:938-950, 2002; Heise and Kern, J Clin Invest 105:847-851, 2000). Given that these therapeutics are self-amplifying in tumors, the impact of dose on patient outcome is unclear. Pexa-Vec (JX-594) is an oncolytic and immunotherapeutic vaccinia virus which was shown to be well tolerated by intratumoral injection and intravenous infusions in Phase 1 trials (Park et al., Lancet Oncol 9:533-542, 2008; Breitbach et al., Nature 477:99-102, 2011). We present the design of a randomized dose-finding trial of Pexa-Vec in patients with advanced HCC in which Pexa-Vec was delivered by intratumoral injection three times every 2 weeks at one of two dose levels (1 × 10(8) plaque forming units (pfu) versus 1 × 10(9) pfu).

Phase 1b Trial of Biweekly Intravenous Pexa-Vec (JX-594), an Oncolytic and Immunotherapeutic Vaccinia Virus in Colorectal Cancer.

Fifteen patients with treatment-refractory colorectal cancer were enrolled on a phase 1b study of Pexa-Vec (pexastimogene devacirepvec; JX-594), an oncolytic and immunotherapeutic vaccinia designed to selectively replicate in cancer cells. Pexa-Vec was administered intravenously every 14 days, at dose levels of 1 × 10(6), 1 × 10(7), or 3 × 10(7) plaque-forming units (pfu)/kg. The primary endpoint was to determine the maximum tolerated dose. Secondary endpoints were pharmacokinetics and pharmacodynamics as well as antitumor activity. Patients were heavily pretreated (mean 4.5 lines of therapy). All patients received at least two Pexa-Vec doses (median = 4; range = 2-4). No dose-limiting toxicities were reported, and the maximum tolerated dose was not reached. The most common adverse events were grade 1/2 flu-like symptoms, generally lasting <24 hours. During the first and last cycles, genome pharmacokinetics were unchanged. Infectious pfu could be detected in plasma up to 2 hours after cycle 1 and up to 30 minutes after cycle 4 (when antivaccinia antibody titers are known to have peaked). Ten patients (67%) had radiographically stable disease. Given the acceptable safety profile of multiple intravenous Pexa-Vec infusions in patients with treatment-refractory colorectal cancer, further trials evaluating efficacy of intravenous Pexa-Vec, as monotherapy or in combination with chemotherapeutic agents, is warranted in this patient population.

Pexa-Vec double agent engineered vaccinia: oncolytic and active immunotherapeutic.

Oncolytic immunotherapies (OI) selectively infect, amplify within and destroy cancer cells, thereby representing a novel class of anti-cancer therapy. In addition to this primary mechanism-of-action (MOA), OI based on vaccinia have been shown to selectively target tumor-associated vasculature, triggering an acute reduction in tumor perfusion. This review focuses on a third complementary MOA for this product class: the induction of active immunotherapy. While the active immunotherapy approach has been validated by recent product approvals, the field is still faced with significant challenges. Tumors have evolved diverse mechanisms to hide from immune-mediated destruction. Here we hypothesize that oncolytic immunotherapy replication within tumors may tip the immune balance to allow for the effective induction and execution of adaptive anti-tumor immunity, resulting in long-term tumor control following OI clearance. This immune activation against the cancer can be augmented through OI 'arming' for the expression of immunostimulatory transgene products from the virus genome. With the first vaccinia OI (Pexa-Vec, thymidine kinase-inactivated vaccinia expressing Granulocyte-colony stimulating factor [GM-CSF]) now in advanced-stage clinical trials, it has become more important than ever to understand the complimentary MOA that contributes to tumor destruction and control in patients.

Complement inhibition prevents oncolytic vaccinia virus neutralization in immune humans and cynomolgus macaques.

Oncolytic viruses (OVs) have shown promising clinical activity when administered by direct intratumoral injection. However, natural barriers in the blood, including antibodies and complement, are likely to limit the ability to repeatedly administer OVs by the intravenous route. We demonstrate here that for a prototype of the clinical vaccinia virus based product Pexa-Vec, the neutralizing activity of antibodies elicited by smallpox vaccination, as well as the anamnestic response in hyperimmune virus treated cancer patients, is strictly dependent on the activation of complement. In immunized rats, complement depletion stabilized vaccinia virus in the blood and led to improved delivery to tumors. Complement depletion also enhanced tumor infection when virus was directly injected into tumors in immunized animals. The feasibility and safety of using a complement inhibitor, CP40, in combination with vaccinia virus was tested in cynomolgus macaques. CP40 pretreatment elicited an average 10-fold increase in infectious titer in the blood early after the infusion and prolonged the time during which infectious virus was detectable in the blood of animals with preexisting immunity. Capitalizing on the complement dependence of antivaccinia antibody with adjunct complement inhibitors may increase the infectious dose of oncolytic vaccinia virus delivered to tumors in virus in immune hosts.

First-in-man study of western reserve strain oncolytic vaccinia virus: safety, systemic spread, and antitumor activity.

Oncolytic viral therapy utilizes a tumor-selective replicating virus which preferentially infects and destroys cancer cells and triggers antitumor immunity. The Western Reserve strain of vaccinia virus (VV) is the most virulent strain of VV in animal models and has been engineered for tumor selectivity through two targeted gene deletions (vvDD). We performed the first-in-human phase 1, intratumoral dose escalation clinical trial of vvDD in 16 patients with advanced solid tumors. In addition to safety, we evaluated signs of vvDD replication and spread to distant tumors, pharmacokinetics and pharmacodynamics, clinical and immune responses to vvDD. Dose escalation proceeded without dose-limiting toxicities to a maximum feasible dose of 3 × 10(9) pfu. vvDD replication in tumors was reproducible. vvDD genomes and/or infectious particles were recovered from injected (n = 5 patients) and noninjected (n = 2 patients) tumors. At the two highest doses, vvDD genomes were detected acutely in blood in all patients while delayed re-emergence of vvDD genomes in blood was detected in two patients. Fifteen of 16 patients exhibited late symptoms, consistent with ongoing vvDD replication. In summary, intratumoral injection of the oncolytic vaccinia vvDD was well-tolerated in patients and resulted in selective infection of injected and noninjected tumors and antitumor activity.

Phase 1 study of intratumoral Pexa-Vec (JX-594), an oncolytic and immunotherapeutic vaccinia virus, in pediatric cancer patients.

Pexa-Vec (pexastimogene devacirepvec, JX-594) is an oncolytic and immunotherapeutic vaccinia virus designed to destroy cancer cells through viral lysis and induction of granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven tumor-specific immunity. Pexa-Vec has undergone phase 1 and 2 testing alone and in combination with other therapies in adult patients, via both intratumoral and intravenous administration routes. We sought to determine the safety of intratumoral administration in pediatric patients. In a dose-escalation study using either 10(6) or 10(7) plaque-forming units per kilogram, we performed one-time injections in up to three tumor sites in five pediatric patients and two injections in one patient. Ages at study entry ranged from 4 to 21 years, and their cancer diagnoses included neuroblastoma, hepatocellular carcinoma, and Ewing sarcoma. All toxicities were ≤ grade 3. The most common side effects were sinus fever and sinus tachycardia. All three patients at the higher dose developed asymptomatic grade 1 treatment-related skin pustules that resolved within 3-4 weeks. One patient showed imaging evidence suggestive of antitumor biological activity. The two patients tested for cellular immunoreactivity to vaccinia antigens showed strong responses. Overall, our study suggests Pexa-Vec is safe to administer to pediatric patients by intratumoral administration and could be studied further in this patient population.

The emerging therapeutic potential of the oncolytic immunotherapeutic Pexa-Vec (JX-594).

Oncolytic immunotherapeutics (OIs) are viruses designed to preferentially replicate in and lyse cancer cells, thereby triggering antitumor immunity. Numerous oncolytic platforms are currently in clinical development. Here we review preclinical and clinical experience with Pexa-Vec (pexastimogene devacirepvec, JX-594). Pexa-Vec is derived from a vaccinia vaccine strain that has been engineered to target cancer cells and express the therapeutic transgene granulocyte macrophage colony-stimulating factor (GM-CSF) in order to stimulate antitumor immunity. Key to its ability to target metastatic disease is the evolution of unique vaccinia virus characteristics that allow for effective systemic dissemination. Multiple mechanisms of action (MOA) for Pexa-Vec have been demonstrated in preclinical models and patients: 1) tumor cell infection and lysis, 2) antitumor immune response induction, and 3) tumor vascular disruption. This review will summarize data on the Pexa-Vec MOA as well as provide an overview of the Pexa-Vec clinical development program from multiple Phase I studies, Phase II studies in renal cell cancer and colorectal cancer, through Phase IIb clinical testing in patients with advanced hepatocellular carcinoma (primary liver cancer).

Oncolytic and immunotherapeutic vaccinia induces antibody-mediated complement-dependent cancer cell lysis in humans.

Oncolytic viruses cause direct cytolysis and cancer-specific immunity in preclinical models. The goal of this study was to demonstrate induction of functional anticancer immunity that can lyse target cancer cells in humans. Pexa-Vec (pexastimogene devacirepvec; JX-594) is a targeted oncolytic and immunotherapeutic vaccinia virus engineered to express human granulocyte-macrophage colony-stimulating factor (GM-CSF). Pexa-Vec demonstrated replication, GM-CSF expression, and tumor responses in previous phase 1 trials. We now evaluated whether Pexa-Vec induced functional anticancer immunity both in the rabbit VX2 tumor model and in patients with diverse solid tumor types in phase 1. Antibody-mediated complement-dependent cancer cell cytotoxicity (CDC) was induced by intravenous Pexa-Vec in rabbits; transfer of serum from Pexa-Vec-treated animals to tumor-bearing animals resulted in tumor necrosis and improved survival. In patients with diverse tumor types treated on a phase 1 trial, CDC developed within 4 to 8 weeks in most patients; normal cells were resistant to the cytotoxic effects. T lymphocyte activation in patients was evidenced by antibody class switching. We determined that patients with the longest survival duration had the highest CDC activity, and identified candidate target tumor cell antigens. Thus, we demonstrated that Pexa-Vec induced polyclonal antibody-mediated CDC against multiple tumor antigens both in rabbits and in patients with diverse solid tumor types.

Randomized dose-finding clinical trial of oncolytic immunotherapeutic vaccinia JX-594 in liver cancer.

Oncolytic viruses and active immunotherapeutics have complementary mechanisms of action (MOA) that are both self amplifying in tumors, yet the impact of dose on subject outcome is unclear. JX-594 (Pexa-Vec) is an oncolytic and immunotherapeutic vaccinia virus. To determine the optimal JX-594 dose in subjects with advanced hepatocellular carcinoma (HCC), we conducted a randomized phase 2 dose-finding trial (n=30). Radiologists infused low- or high-dose JX-594 into liver tumors (days 1, 15 and 29); infusions resulted in acute detectable intravascular JX-594 genomes. Objective intrahepatic Modified Response Evaluation Criteria in Solid Tumors (mRECIST) (15%) and Choi (62%) response rates and intrahepatic disease control (50%) were equivalent in injected and distant noninjected tumors at both doses. JX-594 replication and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression preceded the induction of anticancer immunity. In contrast to tumor response rate and immune endpoints, subject survival duration was significantly related to dose (median survival of 14.1 months compared to 6.7 months on the high and low dose, respectively; hazard ratio 0.39; P=0.020). JX-594 demonstrated oncolytic and immunotherapy MOA, tumor responses and dose-related survival in individuals with HCC.

Oncolytic vaccinia virus disrupts tumor-associated vasculature in humans.

Efforts to selectively target and disrupt established tumor vasculature have largely failed to date. We hypothesized that a vaccinia virus engineered to target cells with activation of the ras/MAPK signaling pathway (JX-594) could specifically infect and express transgenes (hGM-CSF, ß-galactosidase) in tumor-associated vascular endothelial cells in humans. Efficient replication and transgene expression in normal human endothelial cells in vitro required either VEGF or FGF-2 stimulation. Intravenous infusion in mice resulted in virus replication in tumor-associated endothelial cells, disruption of tumor blood flow, and hypoxia within 48 hours; massive tumor necrosis ensued within 5 days. Normal vessels were not affected. In patients treated with intravenous JX-594 in a phase I clinical trial, we showed dose-dependent endothelial cell infection and transgene expression in tumor biopsies of diverse histologies. Finally, patients with advanced hepatocellular carcinoma, a hypervascular and VEGF-rich tumor type, were treated with JX-594 on phase II clinical trials. JX-594 treatment caused disruption of tumor perfusion as early as 5 days in both VEGF receptor inhibitor-naïve and -refractory patients. Toxicities to normal blood vessels or to wound healing were not evident clinically or on MRI scans. This platform technology opens up the possibility of multifunctional engineered vaccinia products that selectively target and infect tumor-associated endothelial cells, as well as cancer cells, resulting in transgene expression, vasculature disruption, and tumor destruction in humans systemically.

Preventing postoperative metastatic disease by inhibiting surgery-induced dysfunction in natural killer cells.

Natural killer (NK) cell clearance of tumor cell emboli following surgery is thought to be vital in preventing postoperative metastases. Using a mouse model of surgical stress, we transferred surgically stressed NK cells into NK-deficient mice and observed enhanced lung metastases in tumor-bearing mice as compared with mice that received untreated NK cells. These results establish that NK cells play a crucial role in mediating tumor clearance following surgery. Surgery markedly reduced NK cell total numbers in the spleen and affected NK cell migration. Ex vivo and in vivo tumor cell killing by NK cells were significantly reduced in surgically stressed mice. Furthermore, secreted tissue signals and myeloid-derived suppressor cell populations were altered in surgically stressed mice. Significantly, perioperative administration of oncolytic parapoxvirus ovis (ORFV) and vaccinia virus can reverse NK cell suppression, which correlates with a reduction in the postoperative formation of metastases. In human studies, postoperative cancer surgery patients had reduced NK cell cytotoxicity, and we show for the first time that oncolytic vaccinia virus markedly increases NK cell activity in patients with cancer. These data provide direct in vivo evidence that surgical stress impairs global NK cell function. Perioperative therapies aimed at enhancing NK cell function will reduce metastatic recurrence and improve survival in surgical cancer patients.

The oncolytic poxvirus JX-594 selectively replicates in and destroys cancer cells driven by genetic pathways commonly activated in cancers.

Oncolytic viruses are generally designed to be cancer selective on the basis of a single genetic mutation. JX-594 is a thymidine kinase (TK) gene-inactivated oncolytic vaccinia virus expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) and lac-Z transgenes that is designed to destroy cancer cells through replication-dependent cell lysis and stimulation of antitumoral immunity. JX-594 has demonstrated a favorable safety profile and reproducible tumor necrosis in a variety of solid cancer types in clinical trials. However, the mechanism(s) responsible for its cancer-selectivity have not yet been well described. We analyzed the replication of JX-594 in three model systems: primary normal and cancer cells, surgical explants, and murine tumor models. JX-594 replication, transgene expression, and cytopathic effects were highly cancer-selective, and broad spectrum activity was demonstrated. JX-594 cancer-selectivity was multi-mechanistic; replication was activated by epidermal growth factor receptor (EGFR)/Ras pathway signaling, cellular TK levels, and cancer cell resistance to type-I interferons (IFNs). These findings confirm a large therapeutic index for JX-594 that is driven by common genetic abnormalities in human solid tumors. This appears to be the first description of multiple selectivity mechanisms, both inherent and engineered, for an oncolytic virus. These findings have implications for oncolytic viruses in general, and suggest that their cancer targeting is a complex and multifactorial process.

Targeted and armed oncolytic poxviruses for cancer: the lead example of JX-594.

Oncolytic viruses (OVs) are designed to replicate in, and subsequently lyse cancer cells. Numerous oncolytic virus platforms are currently in development. Here we review preclinical and clinical experience with JX-594, the lead candidate from the targeted and armed oncolytic poxvirus class. JX-594 is derived from a vaccinia vaccine strain that has been engineered for 1) enhanced cancer targeting and 2) has been "armed" with the therapeutic transgene granulocytemacrophage colony stimulating factor (GM-CSF) to stimulate anti-tumoral immunity. Poxviruses have many ideal features for use as oncolytic agents. The development of oncolytic vaccinia viruses is supported by a large safety database accumulated in the smallpox eradication program. In addition, poxviruses have evolved unique capabilities for systemic spread through the blood that can be harnessed for the treatment of metastatic disease. JX-594 demonstrates a high degree of cancer selectivity and systemic efficacy by multiple mechanisms-of-action (MOAs) in preclinical testing. Data from Phase 1 and 2 clinical trials has confirmed that these features result in potent and systemic efficacy in patients with treatment refractory metastatic cancers.