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.

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 A34^K151E 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 A34^K151E 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.

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

Pexastimogene devacirepvec (Pexa-Vec) is a vaccinia virus-based oncolytic immunotherapy designed to preferentially replicate in and destroy tumor cells while stimulating anti-tumor immunity by expressing GM-CSF. An earlier randomized Phase IIa trial in predominantly sorafenib-naïve hepatocellular carcinoma (HCC) demonstrated an overall survival (OS) benefit. This randomized, open-label Phase IIb trial investigated whether Pexa-Vec plus Best Supportive Care (BSC) improved OS over BSC alone in HCC patients who failed sorafenib therapy (TRAVERSE).

129 patients were randomly assigned 2:1 to Pexa-Vec plus BSC vs. BSC alone. Pexa-Vec was given as a single intravenous (IV) infusion followed by up to 5 IT injections. The primary endpoint was OS. Secondary endpoints included overall response rate (RR), time to progression (TTP) and safety.

A high drop-out rate in the control arm (63%) confounded assessment of response-based endpoints. Median OS (ITT) for Pexa-Vec plus BSC vs. BSC alone was 4.2 and 4.4 months, respectively (HR, 1.19, 95% CI: 0.78–1.80; p = .428). There was no difference between the two treatment arms in RR or TTP. Pexa-Vec was generally well-tolerated. The most frequent Grade 3 included pyrexia (8%) and hypotension (8%). Induction of immune responses to vaccinia antigens and HCC associated antigens were observed.

Despite a tolerable safety profile and induction of T cell responses, Pexa-Vec did not improve OS as second-line therapy after sorafenib failure. The true potential of oncolytic viruses may lie in the treatment of patients with earlier disease stages which should be addressed in future studies.

ClinicalTrials.gov: NCT01387555

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.

Abstract 296: Synergistic actions of oncolytic vaccinia virus and sunitinib on pancreatic neuroendocrine tumors in RIP-Tag2 mice

Pexa-Vec (JX-594) is an engineered oncolytic vaccinia virus that lacks thymidine kinase and expresses human granulocyte-macrophage colony stimulating factor. In addition to having oncolytic effects on tumor cells and promoting an immune response, Pexa-Vec has been found to cause rapid reduction of tumor blood flow in preclinical models and in clinical trials. The angiogenesis inhibitor sunitinib reduces tumor vascularity and can augment the activity of vesicular stomatitis virus by suppressing two interferon-induced anti-viral host proteins, RNA-dependent protein kinase and ribonuclease L.

We explored the interaction of mpJX-594, a mouse-adapted version of Pexa-Vec, and sunitinib. The mouse-adapted version, mpJX-594, was engineered from Western Reserve strain vaccinia virus by deletion of thymidine kinase and addition of human GM-CSF, yellow fluorescent protein, and luciferase genes. The effects of mpJX-594 or sunitinib given individually on pancreatic neuroendocrine tumors in RIP-Tag2 mice were compared to those of the two agents given together. Treatment with mpJX-594 alone reduced tumor vascularity and induced widespread apoptosis in the tumors. After treatment with sunitinib alone, tumor vascularity was decreased, but apoptosis was much less than after mpJX-594 alone. When mpJX-594 was given together with sunitinib, the amount of viral infection in tumors, assessed by vaccinia immunoreactivity, was much more than after mpJX-594 alone. Vaccinia staining was detected in most of the tumor blood vessels and in large patches of tumor cells. The reduction of tumor vascularity and amount of apoptosis were greater after both agents than after either of them given alone.

To determine whether mpJX-594 increased the efficacy of sunitinib in tumors or vice versa, we examined the effects of sequential administration, where mpJX-594 or sunitinib was given first and then followed 5 days later by the other. In both cases, the reduction in tumor vascularity after sequential treatment was greater than after either agent given alone. When sunitinib was given first, tumor vascularity was less throughout tumors, and the surviving vessels appeared more normal. By comparison, when mpJX-594 was given before sunitinib, the tumor vasculature was greatly reduced in some regions and less so in others, and the remaining blood vessels were abnormal. Apoptotic cells were much more numerous and widespread when mpJX-594 preceded sunitinib than after either agent given alone. In contrast, when sunitinib was given first, tumor apoptosis was greater than after sunitinib alone but not after mpJX-594 alone.

Together these findings indicate that mpJX-594 amplifies the anti-vascular and anti-tumor effects of sunitinib and vice versa in RIP-Tag2 pancreatic neuroendocrine tumors, regardless of the sequence of administration, but the magnitude of the changes differs according to the sequence of administration.

Citation Format: Corry E. McDonald, Barbara Sennino, Brian J. Schriver, John C. Bell, David H. Kirn, Caroline J. Breitbach, Donald M. McDonald. Synergistic actions of oncolytic vaccinia virus and sunitinib on pancreatic neuroendocrine tumors in RIP-Tag2 mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 296. doi:10.1158/1538-7445.AM2015-296

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.

Phase II trial of Pexa-Vec (pexastimogene devacirepvec; JX-594), an oncolytic and immunotherapeutic vaccinia virus, followed by sorafenib in patients with advanced hepatocellular carcinoma (HCC)

4122^

Background: Pexa-Vec is a vaccinia virus engineered to express granulocyte-macrophage colony stimulating factor (GM-CSF), thereby stimulating direct oncolysis, tumor vascular disruption and anti-tumor immunity (Nat Rev Cancer 2009). Pexa-Vec was shown to replicate in metastatic tumors following intratumoral (IT) or intravenous (IV) administration (Lancet Oncol 2008; Nature 2011). Preclinical and clinical data suggest that Pexa-Vec-induced acute vascular disruption sensitizes tumors to anti-angiogenic effects of sorafenib (Mol Ther 2011). Methods: Treatment-refractory HCC patients received Pexa-Vec for 3 weeks (Day 1 IV, Day 8 IT and Day 22 IT) followed by sorafenib at Day 25. The primary objective of the study was to determine the safety of Pexa-Vec followed by sorafenib. Secondary objectives include disease control rate based on mRECIST and Choi (hypodensity) response criteria after Pexa-Vec only (Day 25) and after sorafenib initiation (Week 6 and 12). Optional assessments included response by positron-emission tomography (PET). Data summarized prior to database lock. Results: Enrollment is completed: 25 patients of which 20 were refractory to sorafenib. The treatment regimen was well-tolerated. Transient flu-like symptoms, including fever (n=23; 92%), chills (n=19; 76%), headache and nausea (n=10; 40%), abdominal pain and lymphopenia (n=10; 40%) were the most common adverse events following Pexa-Vec. Sorafenib toxicities were consistent with the expected profile. After Pexa-Vec alone the Choi tumor response rate was 47%. Following subsequent sorafenib therapy, 75% had Choi responses, including 81% of sorafenib-failure patients. The mRECIST disease control rate was 62% with Pexa-Vec alone and 59% following initiation of sorafenib. Two of 4 patients evaluable for PET response exhibited decreased PET signal after Pexa-Vec. Conclusions: Pexa-Vec was well-tolerated and associated with Choi tumor responses and disease control in patients with advanced HCC. Subsequent sorafenib was well-tolerated and associated with Choi responses. Further trials of Pexa-Vec in HCC patients are warranted. Clinical trial information: NCT01171651.

Phase Ib dose-escalation study of Pexa-Vec (pexastimogene devacirepvec; JX-594), an oncolytic and immunotherapeutic vaccinia virus, administered by intravenous (IV) infusions in patients with metastatic colorectal carcinoma (mCRC)

3608^

Background: Pexa-Vec is an EGFR-targeted vaccinia virus engineered to express granulocyte-macrophage colony stimulating factor (GM-CSF), thereby stimulating direct oncolysis, tumor vascular disruption and anti-tumor immunity (Nat Rev Cancer 2009). Dose-dependent IV Pexa-Vec delivery was defined previously (Nature2011). This study was designed to assess the safety, maximal tolerated dose and anti-tumor activity of Pexa-Vec administered IV in patients with mCRC after failure of standard therapies. Methods: Nine patients were treated at 1 of 3 dose levels (106, 107 or 3x107pfu/kg IV every 2 weeks x 4) in a standard 3+3 dose-escalation design; 6 additional patients were enrolled at the MFD. Anti-tumor activity according to RECIST was determined using serial CT scans. Pharmacokinetic studies were also performed. Data summarized prior to database lock. Results: 15 patients with mCRC refractory to irinotecan, oxaliplatin, and 5-FU were treated (median lines of therapy 5; range 2-7); 13 of 15 received prior anti-angiogenic agents, and 11 of 12 KRAS WT tumors failed cetuximab. Adverse events were generally grade 1/2 and included: fever (93%), chills (93%), headache (60%), nausea (60%), and hypotension (40%). No dose-limiting toxicities or grade 3/4 events were reported. Only patients treated at high-dose (Cohort 3 & Expansion) exhibited a pustular rash (n=9; 78%). Pexa-Vec genomes detected in blood acutely were above the dose threshold for systemic delivery. Notably, clearance was not more rapid with repeated IV treatments despite the induction of humoral immunity. Furthermore, patients at the top dose level exhibited increased disease stabilization at Week 4 (89% high-dose (n= 9) versus 33% low-dose (n=6)). A trend (p=0.16) towards increased overall survival at high vs low-dose Pexa-Vec was observed with 78% high-dose patients still alive between 5 and 13 mos. Conclusions: Repeat IV Pexa-Vec was well-tolerated with transient flu-like symptoms. Dose-dependent safety, pharmacokinetics and anti-tumor activity were described in treatment-refractory mCRC patients. Clinical trial information: NCT01380600.

Phase IIb randomized trial of Pexa-Vec (pexastimogene devacirepvec; JX-594), a targeted oncolytic vaccinia virus, plus best supportive care (BSC) versus BSC alone in patients with advanced hepatocellular carcinoma who have failed sorafenib treatment (TRAVERSE)

TPS4161^

Background: Pexa-Vec is a targeted oncolytic and immunotherapeutic vaccinia virus engineered to express human granulocyte-macrophage colony stimulating factor (GM-CSF). Direct oncolysis plus GM-CSF expression stimulates tumor vascular disruption and anti-tumor immunity (Nature Rev Cancer, 2009). Pexa-Vec was well-tolerated in Phase 1 trials and was shown to replicate in metastatic tumors following intratumoral (IT) or intravenous (IV) administration (Lancet Oncol, 2008 and Nature, 2011). A randomized high vs low dose Phase 2 trial in 30 patients with advanced HCC, demonstrated prolonged survival in the high-dose Pexa-Vec arm (median survival 14.1 mo vs. 6.7 mo; Hazard Ratio 0.39, p=0.02) (AASLD Annual Meeting, 2011, LB1). Methods: TRAVERSE is a Phase 2b randomized, open-label, multi-center trial in patients with advanced HCC who have failed sorafenib treatment. Approximately 120 patients will be randomized 2:1 to Pexa-Vec plus BSC versus BSC, respectively. Randomization will be stratified by region (Asian vs. non-Asian); sorafenib intolerant vs refractory; and presence vs absence of extra-hepatic disease. The primary objective is to determine overall survival. Main inclusion criteria are advanced HCC having failed sorafenib (intolerance or radiographic progression during or < 3 months following last sorafenib), Child-Pugh A-B7 (no ascites), acceptable hematologic function. Assuming a median overall survival of 4.0 months with BSC and a target hazard ratio of 0.57 (corresponding to an experimental arm median survival of 7.0 months), 73 events (deaths) will provide 70% power at 1-sided alpha = 0.05 to detect a difference in overall survival between the treatment groups using a stratified logrank test. Patients randomized to Pexa-Vec will receive a dose of 109 plaque forming units (pfu) IV on Day 1 followed by five IT treatments between Day 8 and Week 18. Enrollment has begun on this study with clinical trial registry number of NCT01387555. Clinical trial information: NCT01387555.

Abstract 2841: Widespread endothelial cell infection and tumor cell apoptosis after intravenous injection of oncolytic vaccinia virus JX-594 into RIP-Tag2 mice

Replication-competent oncolytic viruses are being developed as a promising strategy for treating certain types of cancer. JX-594 is an oncolytic vaccinia virus that lacks thymidine kinase and expresses human granulocyte-macrophage colony stimulating factor (hGM-CSF). Replication of JX-594 is promoted by EGFR/Ras pathway signaling in cancer cells. In addition to having direct oncolytic effects on tumor cells and recruiting an immune response, JX-594 has been found to cause rapid reduction of tumor blood flow in preclinical models and in clinical trials. To understand the mechanism of this vascular effect, we injected mouse-adapted JX-594 vaccinia virus (mJX-594, on Western Reserve backbone and expressing hGM-CSF) intravenously into RIP-Tag2 transgenic mice and examined the pancreatic neuroendocrine tumors at 6 hours or 1, 2, or 5 days after injection. Dot-like vaccinia immunoreactivity was widespread in endothelial cells of tumor vessels at 6 hours. Scattered endothelial cells had intense staining. Vaccinia immunoreactivity in tumor blood vessels was still widespread at 1 day, but at 5 days, most tumor vessels were narrowed, some appeared fragmented, and tumor vascularity was reduced by 40%. Normalization of tumor vessels, as observed after inhibition of VEGF signaling, was not found at any time examined. Intratumoral hypoxia was evident as diffuse regions of pimonidazole staining at 6 hours. Pimonidazole staining increased from 1 to 5 days, and was especially strong in regions of vascular pruning. Extravascular vaccinia immunoreactivity was located in scattered cells at 1 day and increased with time. At 5 days, most tumors had large patches of vaccinia-positive cells. This staining was not present in the surrounding normal acinar pancreas. Apoptotic cells stained for activated caspase-3 were scattered throughout tumors at 6 hours. Most of these apoptotic cells were endothelial cells. Apoptotic tumor cells were sparse at 6 hours, but at 5 days apoptotic cells were 23-fold more numerous than at baseline and even more widespread than vaccinia immunoreactivity, and tumors tended to be smaller than corresponding controls. These findings are consistent with oncolytic virus mJX-594 causing rapid infection of tumor vascular endothelial cells in RIP-Tag2 mice. Endothelial cell infection is followed by regression of tumor blood vessels, exaggeration of intratumoral hypoxia, and oncolytic actions on tumor cells that lead to widespread tumor cell apoptosis.

Citation Format: Barbara Sennino, Brian J. Schriver, Caroline J. Breitbach, Naomi De Silva, John C. Bell, David H. Kirn, Donald M. McDonald. Widespread endothelial cell infection and tumor cell apoptosis after intravenous injection of oncolytic vaccinia virus JX-594 into RIP-Tag2 mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2841. doi:10.1158/1538-7445.AM2013-2841

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.

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.

Imaging approaches to assess mechanism-of-action and response in patients with advanced hepatocellular carcinoma treated with the novel oncolytic poxvirus JX-594

210

Background: The novel oncolytic virus JX-595 has demonstrated anti-cancer mechanisms of action, as defined in preclinical models, which includes cytolysis, intra-tumoral vascular disruption, and immune-mediated tumor targeting. Methods: To determine whether mechanism(s) of action (MOA) of the novel anti-cancer oncolytic virus JX-594 could be demonstrated by MRI imaging in patients with advanced hepatocellular carcinoma (HCC), dynamic contrast-enhanced MRI of the liver was performed at baseline, day 5, and week 8 following intra-tumoral injection. Images were evaluated by a central reviewer blinded to treatment and dose using both modified RECIST and Choi response criteria. 17/30 subjects underwent day 5 (D5) post-treatment imaging; 28/30 had week 8 (W8) imaging. Results: Choi responses correlated more reliably than RECIST with JX-594 MOA. Evidence of intra-tumoral vascular shutdown, manifest by areas of reduced or non-enhancement (Choi response), was observed in 6 of 17 subjects on D5 5 MRI scans. Day 5 Choi responses were a predictor of week 8 Choi responses in all but 1 subject. Of the 11/17 D5 Choi non-responders, 3 were Choi responders at 8 weeks. Increase in size at D5 of small lesions present at baseline (“unmasking”) is compatible with oncolytic flare due to intra-tumoral edema contributed to by cell lysis and immune infiltration. RECIST criteria tumor measurements did not identify MOA of JX-594, and resulted in the appearance of pseudoprogression at D5 in some subjects. Conclusions: Hyperacute MRI post-therapy can be used to detect activity of the JX-594, a novel oncolytic anti-cancer therapy. Day 5 Choi responses were a predictor of subsequent response at week 8. Clinical trial information: NCT00554372.

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.

A phase Ib dose escalation study of JX-594 (TK-vaccinia virus expressing GM-CSF) administered by biweekly intravenous infusion in patients with metastatic, refractory colorectal carcinoma

e13044

Background: JX-594 is a recombinant vaccinia virus engineered to selectively replicate in and destroy cancer cells while stimulating a systemic anti-tumor immune response and inducing a reduction in tumor blood perfusion. Preclinical data has demonstrated JX-594 activity is enhanced in cells with up regulation of the EGFR pathway. JX-594 anti-tumor activity in multiple advanced solid tumors has been observed in early stage clinical studies. This study was designed to assess the safety, MTD/MFD, and initial anti-tumor activity of JX-594 administered IV every other week x 4 total treatments in patients with metastatic CRC after failure of standard chemotherapy. Methods: A standard 3+3 dose escalation design was used to enroll patients into three dose levels (106, 107 or 3x107pfu/kg) of JX-594 administered IV every 2 weeks x4. Safety was assessed using CTCAEv3.0. Anti-tumor activity was determined based on serial CT scans and CEA measurements. Patient samples were collected for pharmacokinetics and pharmacodynamics. Results: Enrollment is ongoing with 8 patients treated at total doses ranging from 5x107 to 2x109 pfu. Adverse events have generally been limited to grade 1/2, transient flu-like symptoms (fever, chills, headache). No DLT was reported. Three patients in the top two dose levels demonstrated SD on week 4 CT scan with one maintained at week 8. In these same 3 patients, CEA declined by 50% in a single patient while the other 2 had no significant change in CEA. Conclusions: Preliminary data for this dose escalation trial demonstrates JX-594 is well tolerated after 4 IV treatments administered every other week. CEA and CT scan assessment suggest possible efficacy. Enrollment continues and an expansion cohort at the MTD is planned. Updated data is expected at the time of presentation.

A phase II trial of JX-594, a targeted multimechanistic oncolytic vaccinia virus, followed by sorafenib in patients with advanced hepatocellular carcinoma (HCC)

e14566

Background: JX-594 is a targeted oncolytic vaccinia virus designed to selectively replicate in and destroy cancer cells with epidermal growth factor receptor (EGFR)/ ras pathway activation. Direct oncolysis plus GM-CSF expression is accompanied by tumor vascular disruption and anti-tumoral immunity (Reviewed in Nat Rev Cancer 2009). JX-594 was well-tolerated intravenously (IV) (Nature 2011) and intratumorally (IT) (Lancet Oncol 2008). Complementary anti-tumor effects are predicted with JX-594 followed by sorafenib due to acute vascular disruption effects with JX-594 and anti-angiogenic effects with sorafenib. Methods: Treatment-refractory HCC patients received JX-594 for three weeks (Day 1 IV, Day 8 IT and Day 22 IT) followed by sorafenib. An IT boost dose of JX-594 at Week 12 was optional. The primary objective of the study was to determine the safety of JX-594 followed by sorafenib in patients with advanced HCC. Secondary objectives include disease control rate (DCR) based on mRECIST and/or Choi response criteria at Day 6 (optional), Day 25 (after JX-594 only), 6 and 12 weeks. Results: Twenty (20) patients were treated in this study; fifteen (15) were refractory to sorafenib. The sequential treatment regimen was well-tolerated. Transient flu-like symptoms (Grade 1-2) and transient leukopenia (lymphopenia, neutropenia) were the most common adverse events following JX-594 therapy. Sorafenib toxicities were consistent with the expected toxicity profile. At the time of this interim analysis, thirteen patients were evaluable for radiographic response by Choi criteria (mRECIST pending). After JX-594 alone at Day 25, 10 of 13 evaluable patients (77%) had Choi tumor responses (range 19-48% reduced enhancement). Following subsequent sorafenib therapy, 11 of 13 patients (85%) had Choi responses at Week 6-12, including 9 of 10 (90%) sorafenib-failure patients. Conclusions: JX-594 was well-tolerated and associated with Choi tumor responses following IV and IT injections in patients with advanced HCC. Subsequent sorafenib was associated with the expected toxicity profile. Further trials of JX-594 in HCC patients are warranted.

Phase IIb randomized trial of JX-594, a targeted multimechanistic oncolytic vaccinia virus, plus best supportive care (BSC) versus BSC alone in patients with advanced hepatocellular carcinoma who have failed sorafenib treatment (TRAVERSE)

TPS4152

Background: JX-594 is a first-in-class targeted oncolytic poxvirus designed to selectively replicate in and destroy cancer cells with epidermal growth factor receptor (EGFR)/ ras pathway activation. Direct oncolysis plus GM-CSF expression stimulates tumor vascular disruption and anti-tumor immunity (Nature Rev Cancer 2009). JX-594 was well-tolerated in Phase 1 trials and was shown to replicate in metastatic tumors following intratumoral (IT) or intravenous (IV) administration (Lancet Oncol 2008 and Nature 2011). A randomized dose-finding Phase 2 trial has been completed with JX-594 in 30 patients with advanced HCC. Treatment with high-dose JX-594 was associated with prolonged survival vs low-dose JX-594 (median survival 14.1 mo vs 6.7 mo; Hazard Ratio 0.39, p=0.02) (AASLD Annual Meeting, 2011, LB1). Methods: TRAVERSE is a Phase 2b randomized, open-label, multi-center trial of JX-594 plus BSC versus BSC in patients with advanced HCC who have failed sorafenib treatment. Approximately 120 patients will be randomized 2:1 to experimental and control arm respectively. Randomization will be stratified by region (Asian vs non-Asian); sorafenib intolerant vs refractory; and presence vs absence of extra-hepatic disease. The primary objective is to determine overall survival in the 2 arms. Assuming a control median overall survival of 4.0 months and a target hazard ratio of 0.57 (corresponding to an experimental arm median survival of 7.0 months), 73 events (deaths) will provide 70% power at 1-sided alpha = 0.05 to detect a difference in overall survival between the treatment groups using a stratified logrank test. Patients randomized to JX-594 will receive a dose of 109 plaque forming units (pfu) IV on Day 1 followed by five IT treatments between Day 8 and Week 18. Main inclusion criteria are advanced HCC having failed sorafenib (intolerance or radiographic progression during or < 3 months following last sorafenib), Child-Pugh A-B7 (no ascites), acceptable hematologic function. Enrollment has begun on this study with clinical trial registry number of NCT01387555.

Abstract LB-283: JX-594, a targeted multi-mechanistic oncolytic poxvirus, selectively infects tumor vasculature and causes acute tumor vascular disruption and necrosis in advanced cancer patients

JX-594 is a first-in-class targeted oncolytic poxvirus designed to selectively replicate in and destroy cancer cells with cell cycle abnormalities and epidermal growth factor receptor (EGFR)/ras pathway activation. Direct oncolysis plus granulocyte macrophage -colony stimulating factor (GM-CSF) expression also stimulates anti-tumoral immunity. JX-594 infection was evaluated in vitro on human umbilical vein endothelial cells (HUVECs) and by immunohistochemical analysis in tumor biopsies from JX-594 treated (intravenous administration) patients with advanced, treatment-refractory solid tumors. JX-594 associated changes in tumor perfusion were also assessed in patients by dynamic contrast-enhanced magnetic resonance imaging (dce-MRI; at baseline and Day 5 after intratumoral JX-594 administration). In vitro susceptibility of HUVECs to JX-594 infection was shown to be dependent on vascular endothelial growth factor (VEGF) stimulation. Furthermore, JX-594 was capable of infecting tumor-associated endothelial cells after intravenous infusion in patients with advanced solid tumors. No clinical evidence of normal vasculature infection or toxicity was noted. Tumor perfusion was significantly decreased within 5 days post JX-594 treatment, including in hepatocellular carcinoma and colorectal cancer metastases. Perfusion was markedly reduced in both directly injected and distant non-injected tumors. Choi (necrotic) responses at later timepoints were demonstrated. In addition to targeting cancers by direct infection and lysis of tumor cells, JX-594 is capable of directly infecting VEGF-stimulated/tumor-associated endothelial cells. By targeting tumor-associated vasculature, JX-594 acutely disrupts the tumor's blood supply leading to tumor destruction. Targeted oncolytic poxviruses such as JX-594 represent a novel and highly selective class of vascular disrupting agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-283. doi:10.1158/1538-7445.AM2011-LB-283

Sequential therapy with JX-594, a targeted oncolytic poxvirus, followed by sorafenib in hepatocellular carcinoma: preclinical and clinical demonstration of combination efficacy

JX-594 is a targeted and granulocyte-macrophage colony stimulating factor (GM-CSF) expressing oncolytic poxvirus designed to selectively replicate in and destroy cancer cells through viral oncolysis and tumor-specific immunity. In a phase 1 trial, JX-594 injection into hepatocellular carcinoma (HCC) was well-tolerated and associated with viral replication, decreased tumor perfusion, and tumor necrosis. We hypothesized that JX-594 and sorafenib, a small molecule inhibitor of B-raf and vascular endothelial growth factor receptor (VEGFR) approved for HCC, would have clinical benefit in combination given their demonstrated efficacy in HCC patients and their complementary mechanisms-of-action. HCC cell lines were uniformly sensitive to JX-594. Anti-raf kinase effects of concurrent sorafenib inhibited JX-594 replication in vitro, whereas sequential therapy was superior to either agent alone in murine tumor models. We therefore explored pilot safety and efficacy of JX-594 followed by sorafenib in three HCC patients. In all three patients, sequential treatment was (i) well-tolerated, (ii) associated with significantly decreased tumor perfusion, and (iii) associated with objective tumor responses (Choi criteria; up to 100% necrosis). HCC historical control patients on sorafenib alone at the same institutions had no objective tumor responses (0 of 15). Treatment of HCC with JX-594 followed by sorafenib has antitumoral activity, and JX-594 may sensitize tumors to subsequent therapy with VEGF/VEGFR inhibitors.

A high-throughput pharmacoviral approach identifies novel oncolytic virus sensitizers

Oncolytic viruses (OVs) are promising anticancer agents but like other cancer monotherapies, the genetic heterogeneity of human malignancies can lead to treatment resistance. We used a virus/cell-based assay to screen diverse chemical libraries to identify small molecules that could act in synergy with OVs to destroy tumor cells that resist viral infection. Several molecules were identified that aid in viral oncolysis, enhancing virus replication and spread as much as 1,000-fold in tumor cells. One of these molecules we named virus-sensitizers 1 (VSe1), was found to target tumor innate immune response and could enhance OV efficacy in animal tumor models and within primary human tumor explants while remaining benign to normal tissues. We believe this is the first example of a virus/cell-based "pharmacoviral" screen aimed to identify small molecules that modulate cellular response to virus infection and enhance oncolytic virotherapy.

Navigating the clinical development landscape for oncolytic viruses and other cancer therapeutics: no shortcuts on the road to approval

Chemotherapy remains a common mode of anticancer treatment even though in most cancer indications the therapeutic approach is not effective and ultimately associated with the onset of chemoresistance. A better understanding of genetic differences in tumors ushered in the era of targeted therapy which has revolutionized the treatment of certain cancer types. However, generally targeted therapies are only cytostatic and a proportion of the patient population may be non-responsive to targeted therapy due to mutations of other genes in the same pathway (e.g. ras mutations in patients with colorectal cancer treated with EGFR targeted therapy). Therefore, there exists a need for a radically new approach to cancer therapy. Oncolytic viruses (OVs) possess many properties of an ideal cancer therapeutic. OVs are cytotoxic and target cancers via multiple mechanisms of action while at the same time exploiting validated genetic pathways known to be dysregulated in many cancers. Indeed, promising safety and efficacy data has emerged from Phase 1 and Phase 2 trials with diverse OVs (e.g. JX-594, a targeted oncolytic poxvirus). Though the field has lagged behind with pivotal, randomized Phase 3 trials, these are currently being initiated for a number of OVs. In addition, the field must ensure a continued clinical development of newly developed OVs; a strategy for the clinical development of novel cancer therapeutics is outlined.

Double trouble for tumours: exploiting the tumour microenvironment to enhance anticancer effect of oncolytic viruses

Oncolytic viruses (OVs) are selected based on their ability to eliminate malignancies by direct infection and lysis of cancer cells. Originally, OVs were designed to target malignancies by taking advantage of the defects of cancer cells observed in vitro. Subsequent analysis of virus delivery and spread in vivo has demonstrated that the tumour microenvironment can impede the ability of OVs to effectively infect and spread. Despite this limitation, it is becoming increasingly evident that OVs are also able to take advantage of certain features of the tumour microenvironment. Currently, a growing body of the literature is delineating the complex interaction between OVs and the tumour microenvironment that results in an additional therapeutic activity; these viruses are able to target malignancies by rapidly altering the tumour microenvironment into a milieu that potentiates anticancer activity. Herein, we discuss strategies that capitalize on the multifaceted relationship between OVs and host-tumour interactions that enhance the toxicity of OVs to the tumour microenvironment.

Oncolytic and immunostimulatory efficacy of a targeted oncolytic poxvirus expressing human GM-CSF following intravenous administration in a rabbit tumor model

Targeted oncolytic poxviruses hold promise for the treatment of cancer. Arming these agents with immunostimulatory cytokines (for example, granulocyte-monocyte colony-stimulating factor; GM-CSF) can potentially increase their efficacy and/or alter their safety. However, due to species-specific differences in both human GM-CSF (hGM-CSF) activity and poxviruses immune avoidance proteins, the impact of hGM-CSF expression from an oncolytic poxvirus cannot be adequately assessed in murine or rat tumor models. We developed a rabbit tumor model to assess toxicology, pharmacodynamics, oncolytic efficacy and tumor-specific immunity of hGM-CSF expressed from a targeted oncolytic poxvirus JX-963. Recombinant purified hGM-CSF protein stimulated a leukocyte response in this model that paralleled effects of the protein in humans. JX-963 replication and targeting was highly tumor-selective after i.v. administration, and intratumoral replication led to recurrent, delayed systemic viremia. Likewise, hGM-CSF was expressed and released into the blood during JX-963 replication in tumors, but not in tumor-free animals. hGM-CSF expression from JX-963 was associated with significant increases in neutrophil, monocyte and basophil concentrations in the peripheral blood. Finally, tumor-specific cytotoxic T lymphocytes (CTL) were induced by the oncolytic poxvirus, and expression of hGM-CSF from the virus enhanced both tumor-specific CTL and antitumoral efficacy. JX-963 had significant efficacy against both the primary liver tumor as well as metastases; no significant organ toxicity was noted. This model holds promise for the evaluation of immunostimulatory transgene-armed oncolytic poxviruses, and potentially other viral species.

Targeted genetic and viral therapy for advanced head and neck cancers

Head and neck cancers usually present with advanced disease and novel therapies are urgently needed. Genetic therapy aims at restoring malfunctioned tumor suppressor gene(s) or introducing proapoptotic genes. Oncolytic virotherapeutics induce multiple cycles of cancer-specific virus replication, followed by oncolysis, virus spreading and infection of adjacent cancer cells. Oncolytic viruses can also be armed to express therapeutic transgene(s). Recent advances in preclinical and clinical studies are revealing the potential of both therapeutic classes for advanced head and neck cancers, including the approval of two products (Gendicine and H101) by a governmental agency. This review summarizes the available clinical data to date and discusses the challenges and future directions.

Targeted and armed oncolytic poxviruses: a novel multi-mechanistic therapeutic class for cancer

Viruses have been engineered for cancer therapy in a variety of ways. Approaches include non-replicating gene therapy vectors, cancer vaccines and oncolytic viruses, but the clinical efficacy of these approaches has been limited by multiple factors. However, a new therapeutic class of oncolytic poxviruses has recently been developed that combines targeted and armed approaches for treating cancer. Initial preclinical and clinical results show that products from this therapeutic class can systemically target cancers in a highly selective and potent fashion using a multi-pronged mechanism of action.

Development of targeted oncolytic virotherapeutics through translational research

BACKGROUND

Oncolytic virotherapeutics is a promising platform for cancer treatment but the product class has yet been successful. The key to success is integration of bidirectional translational research to rapidly address issues encountered in the laboratory and the clinics.

OBJECTIVE

We highlight the hurdles identified for the targeted oncolytic virotherapy approach, specifically those identified in clinical trials with wild-type viruses and first-generation targeted agents. We also analyze the translational research and development that has been applied to overcome these hurdles, including virus engineering and design improvements for next-generation virotherapeutics.

RESULTS/CONCLUSION

The iterative loop between the clinic and the lab can function as a major driving force to optimize products from this platform.

Oncolytic virotherapy for advanced liver tumours

Primary and metastatic neoplasms of the liver account for more than a million deaths per year worldwide. Despite decades of research, effective novel therapies for these cancers are urgently needed. Oncolytic virotherapeutics represent a novel class of pharmacophore that holds promise for the treatment of hepatic neoplasms. Cancer-specific replication is followed by oncolysis, virus spreading and infection of adjacent cancer cells. This process is then repeated. Virotherapeutics target multiple genetic pathways involved in carcino-genesis, and demonstrate activity against apoptosis-resistant tumour cells. This platform can also exploit the advantage of multiple intrinsic anti-cancer therapeutic mechanisms, combining direct viral oncolysis with therapeutic transgene expression. Recent advances in pre-clinical and clinical studies are revealing the potential of this unique therapeutic class, in particular for liver cancers. This review summarizes the available data on applying oncolytic virotherapeutics to hepatic neoplasms to date, and discusses the challenges and future directions for virotherapy.

Enhancing poxvirus oncolytic effects through increased spread and immune evasion

The antitumoral effects of oncolytic viruses have generally been limited by inefficient spread of the viruses within infected tumors and by inefficient systemic delivery, particularly in preimmunized hosts. Tumor-selective poxviruses have biological characteristics that may overcome these limitations. Nevertheless, physical barriers within the tumor microenvironment, including the extracellular matrix, can still limit intratumoral spread, and neutralizing antibodies can impede systemic delivery. To counter these limitations, we sought to take advantage of a naturally occurring poxvirus form known as extracellular enveloped virus (EEV). The EEV is shrouded by a host cell-derived lipid bilayer containing anticomplement proteins and is typically released from infected cells early during the infection cycle. Therefore, the EEV form evolved for rapid systemic spread within the host and for evasion of immune-mediated clearance. We compared the oncolytic potential of low versus high EEV-producing strains of vaccinia. EEV-enhanced vaccinia strains displayed improved spread within tumors after systemic delivery, resulting in significantly improved antitumor effects. The EEV-enhanced strains also displayed a greater ability to spread between injected and noninjected distant tumors through the blood and, importantly, displayed reduced clearance by neutralizing antibody. Safety was unaffected. The incorporation of EEV-enhancing mutations into next generation oncolytic vaccinia strains may improve the potency of these viruses without sacrificing safety.

Rational strain selection and engineering creates a broad-spectrum, systemically effective oncolytic poxvirus, JX-963

Replication-selective oncolytic viruses (virotherapeutics) are being developed as novel cancer therapies with unique mechanisms of action, but limitations in i.v. delivery to tumors and systemic efficacy have highlighted the need for improved agents for this therapeutic class to realize its potential. Here we describe the rational, stepwise design and evaluation of a systemically effective virotherapeutic (JX-963). We first identified a highly potent poxvirus strain that also trafficked efficiently to human tumors after i.v. administration. This strain was then engineered to target cancer cells with activation of the transcription factor E2F and the EGFR pathway by deletion of the thymidine kinase and vaccinia growth factor genes. For induction of tumor-specific cytotoxic T lymphocytes, we further engineered the virus to express human GM-CSF. JX-963 was more potent than the previously used virotherapeutic Onyx-015 adenovirus and as potent as wild-type vaccinia in all cancer cell lines tested. Significant cancer selectivity of JX-963 was demonstrated in vitro in human tumor cell lines, in vivo in tumor-bearing rabbits, and in primary human surgical samples ex vivo. Intravenous administration led to systemic efficacy against both primary carcinomas and widespread organ-based metastases in immunocompetent mice and rabbits. JX-963 therefore holds promise as a rationally designed, targeted virotherapeutic for the systemic treatment of cancer in humans and warrants clinical testing.

Randomized phase 3 trial of interferon gamma-1b plus standard carboplatin/paclitaxel versus carboplatin/paclitaxel alone for first-line treatment of advanced ovarian and primary peritoneal carcinomas: results from a prospectively designed analysis of progression-free survival

OBJECTIVES

Interferon gamma (IFN-gamma) is a pleiotropic cytokine with antiproliferative, immunostimulatory, and chemosensitization properties. This trial was designed to evaluate IFN-gamma 1b plus carboplatin and paclitaxel in treatment-naive ovarian cancer (OC) and primary peritoneal carcinoma (PPC) patients.

METHODS

Eligible patients were randomized to 6 cycles of carboplatin/paclitaxel every 3 weeks or the same in combination with IFN-gamma 1b (100 microg 3x/wk subcutaneously). The primary endpoint was overall survival (OS) time (target hazard ratio (HR)=0.77). Secondary endpoints included progression-free survival (target HR=0.7), based on blinded review of serial imaging scans, physical exams, and CA-125 levels.

RESULTS

847 patients were enrolled (OC 774, PPC 73) in Europe (n=539) and North/South America (n=308) from January 29, 2002 to March 31, 2004 and stratified according to: optimal debulking (n=271) versus suboptimal debulking with plans for interval debulking (PID) (n=238) or no PID (n=338). The study stopped early following a protocol-defined second interim analysis which revealed significantly shorter OS time in patients receiving IFN-gamma 1b plus chemotherapy compared to chemotherapy alone (1138 days vs. not estimable, HR=1.45, 95% CI=1.15-1.83). At the time of the analysis, 169 of 426 (39.7%) patients in the IFN-gamma 1b plus chemotherapy group had died compared to 128 of 421 (30.4%) in the chemotherapy alone group. Serious adverse events were more common in the IFN-gamma 1b plus chemotherapy group (48.5% vs. 35.4%), primarily due to a higher incidence of serious hematological toxicities (34.5% vs. 22.7%).

CONCLUSIONS

Treatment with IFN-gamma 1b in combination with carboplatin/paclitaxel does not have a role in the first-line treatment of advanced ovarian cancer.

Oncolytic adenoviruses for cancer gene therapy

The use of replication-competent oncolytic viruses has largely advanced cancer gene therapy. Oncolytic virus not only possesses unique mechanisms of action that are distinct from other treatment modalities, its self-perpetuating nature provides an ideal platform for therapeutic transgene insertion. Tumor selectivity can be achieved by deleting viral genes that are critical for growth in normal cells but dispensable in tumor cells, transcriptional control under tumor-specific promoters, fiber modification targeting tumor-specific cellular receptors, or the use of inherent tumor-specific viruses. Transgene products can be amplified along with viral replication, thus maximizing therapeutic effect. Using adenovirus as a template, this chapter describes common assays used for the study of oncolytic viruses, with special emphasis on in vitro and in vivo viral replication determination.

Targeting of interferon-beta to produce a specific, multi-mechanistic oncolytic vaccinia virus

BACKGROUND

Oncolytic viruses hold much promise for clinical treatment of many cancers, but a lack of systemic delivery and insufficient tumor cell killing have limited their usefulness. We have previously demonstrated that vaccinia virus strains are capable of systemic delivery to tumors in mouse models, but infection of normal tissues remains an issue. We hypothesized that interferon-beta (IFN-beta) expression from an oncolytic vaccinia strain incapable of responding to this cytokine would have dual benefits as a cancer therapeutic: increased anticancer effects and enhanced virus inactivation in normal tissues. We report the construction and preclinical testing of this virus.

METHODS AND FINDINGS

In vitro screening of viral strains by cytotoxicity and replication assay was coupled to cellular characterization by phospho-flow cytometry in order to select a novel oncolytic vaccinia virus. This virus was then examined in vivo in mouse models by non-invasive imaging techniques. A vaccinia B18R deletion mutant was selected as the backbone for IFN-beta expression, because the B18R gene product neutralizes secreted type-I IFNs. The oncolytic B18R deletion mutant demonstrated IFN-dependent cancer selectivity and efficacy in vitro, and tumor targeting and efficacy in mouse models in vivo. Both tumor cells and tumor-associated vascular endothelial cells were targeted. Complete tumor responses in preclinical models were accompanied by immune-mediated protection against tumor rechallenge. Cancer selectivity was also demonstrated in primary human tumor explant tissues and adjacent normal tissues. The IFN-beta gene was then cloned into the thymidine kinase (TK) region of this virus to create JX-795 (TK-/B18R-/IFN-beta+). JX-795 had superior tumor selectivity and systemic intravenous efficacy when compared with the TK-/B18R- control or wild-type vaccinia in preclinical models.

CONCLUSIONS

By combining IFN-dependent cancer selectivity with IFN-beta expression to optimize both anticancer effects and normal tissue antiviral effects, we were able to achieve, to our knowledge for the first time, tumor-specific replication, IFN-beta gene expression, and efficacy following systemic delivery in preclinical models.

From ONYX-015 to armed vaccinia viruses: the education and evolution of oncolytic virus development

The current field of oncolytic virus development has evolved from, and been educated by, the route adenoviruses have taken to Phase III development in the United States (Onyx-015) and commercial approval in China (H101). Clinical development of these E1B-deleted viruses showed that a staged approach, from single-agent intratumoral injections to trials testing intravenous delivery and trials in combination with approved therapies is judicious and can be successful. Additional oncolytic products are in development, including andenovirus plus other promising platforms such as herpes simplex virus, Newcastle disease virus, reovirus and vaccinia virus. These second-generation products seek to expand clinical utility beyond the modest local efficacy of Onyx-015/H101 to potent systemic delivery and efficacy. Improvement of efficacy in metastatic cancer will depend not only on enhanced killing of tumor cells, but also on achieving intravenous delivery and better intratumoral dissemination. Many viruses inherently replicate preferentially in tumors, and engineering can increase this therapeutic index by targeting genetic features of cancers. However, both viruses and cancer cells have complex biologies. Therefore, research may reveal that there is not a single predictive factor for tumor specificity. For example, the Onyx-015 mechanism-of-selectivity has proved to be complex. Further research regarding pathway dependence for other oncolytic viruses may also reveal multiple influences on their tumor tropism.

Selective intratumoral amplification of an antiangiogenic vector by an oncolytic virus produces enhanced antivascular and anti-tumor efficacy

The development of effective cancer therapy will require the simultaneous targeting of multiple steps in tumor development. We have previously described an antiangiogenic gene therapy vector, Ad Flk1-Fc, which expresses a soluble VEGF receptor capable of inhibiting tumor angiogenesis and growth. We have also described an oncolytic virus, dl922/947, whose replication and subsequent cytotoxicity are restricted to cancer cells with a loss of the G1-S cell cycle checkpoint. Here we have optimized methods for combining these therapies, yielding significantly greater anti-tumor effects than the respective monotherapies. In cultured tumor lines, co-infection with both Ad Flk1-Fc and dl922/947 allowed replication and repackaging of the replication-deficient Ad Flk1-Fc and enhanced soluble VEGF receptor expression. Similar repackaging and increased gene expression were demonstrated in vivo using bioluminescence imaging studies. Finally, coadministration of these therapeutic viral therapies in vivo produced significantly enhanced anti-tumor effects in colon HCT 116 and prostate PC-3 xenografts in mice. This increased therapeutic benefit correlated with replication of Ad Flk1-Fc viral genomes, increased intratumoral levels of Flk1-Fc protein, and decreased microvessel density, consistent with enhanced antiangiogenic activity.

Genetically based therapeutics for cancer: similarities and contrasts with traditional drug discovery and development

The field of molecular therapeutics is in its infancy and represents a promising and novel avenue for targeted cancer treatments. Like the small-molecule and antibody therapeutics before them, however, the genetic-based therapies will face significant research and development challenges in their maturation toward an approved cancer therapy. To facilitate this process, we outline and examine in this review the drug development process, briefly summarizing the research and development paradigms that have accompanied the recent successes of the small-molecule and antibody-based cancer therapeutics. Using this background, we compare and contrast the research and development experiences of small-molecule and antibody therapeutics with genetic-based cancer therapeutics, using oncolytic viruses as a defined example of an experimental molecular therapeutic for cancer.

Vaccinia virus and oncolytic virotherapy of cancer

Vaccinia viruses possess many of the key attributes necessary for an ideal viral backbone for use in oncolytic virotherapy. These include a short lifecycle, with rapid cell-to-cell spread. strong lytic ability, a large cloning capacity and well-defined molecular biology. In addition, although capable of replicating in human cells, they are not considered a natural health problem and are especially well characterized. having been delivered to millions of individuals during the campaign to eradicate smallpox. A variety of tumor-targeting mutations have been described in several different vaccinia strains and the expression of a variety of different transgenes has been studied. Early clinical results using either vaccine strains or genetically modified vaccinia strains have demonstrated antitumor effects. Future prospects for the development of these viruses will be discussed.

The Use of Oncolytic Vaccinia Viruses in the Treatment of Cancer: A New Role for an Old Ally?

The use of genetically engineered, tumor-targeting viruses as oncolytic agents has recently emerged as a promising new area for the development of novel cancer therapies. The first viruses to enter the clinic, such as ONYX-015 (an oncolytic adenovirus), provided evidence both for the safety and for the anti-tumor potential of this approach. The results of these early trials have also allowed investigators to examine the limitations of these viruses and to develop potentially far more effective approaches. In this review the development of such next generation viruses, in particular the potential use of strains of vaccinia virus, will be discussed. Vaccinia has an enormous history of use in humans and possesses many of the features felt to be beneficial for the creation of a successful virotherapy agent. It causes no known disease in humans, yet is capable of infecting almost all cell types with a subsequent rapid and lytic infection, which subsequently induces a vigorous local CTL immune response at the site of infection. Vaccinia also displays natural tumor tropism, and several approaches have been used to further limit viral replication to tumor cells and to optimize the immune response induced at the site of the tumor. Finally, the large cloning capacity of vaccinia allows for the addition of multiple foreign genes into the viral genome. This has been exploited to increase the bystander effect of the virus by immune modulation or by expression of pro-drug converting enzymes as well as to incorporate safety controls and reporters for in vivo molecular imaging. Initial clinical trials with these viruses further highlights their potential as the next generation of oncolytic agents and as highly effective future cancer therapies.

Future directions for the field of oncolytic virotherapy: a perspective on the use of vaccinia virus

Oncolytic virotherapy is an emerging biotherapeutic platform based on genetic engineering of viruses capable of selectively infecting and replicating within cancer cells. Such viruses have been found to be both safe and to produce antitumour effects in a number of Phase I and II clinical trials. Early work in this field has been pioneered with strains of adenovirus which, although well suited to gene therapy approaches, have displayed certain limitations in their ability to directly destroy and spread through tumour tissues, particularly after systemic administration. Investigators have subsequently been examining the feasibility of using a variety of different viruses as oncolytic agents. Vaccinia virus is perhaps the most widely administered and successful medical product in history; it displays many of the qualities thought necessary for an effective antitumour agent and is particularly well characterised in people due to its role in the eradication of smallpox. Vaccinia has a short life cycle and rapid spread, strong lytic ability, inherent systemic tumour targeting, a large cloning capacity and well-defined molecular biology. In addition, the virus produces no known disease in humans, has been delivered safely to millions of people and has already demonstrated antitumoural efficacy in trials with vaccine strains. These qualities, along with strategies for further improving the safety and antitumour effectiveness of vaccinia, will be discussed in relation to the broad spectrum of clinical experience already achieved with this virus in cancer therapy.

Interleukin-1beta and tumour necrosis factor-alpha promote the transformation of human immortalised mesothelial cells by erionite

Asbestos fails to induce the transformation of human mesothelial cells in vitro although it has been known as a potential carcinogen to human mesothelial cells. Interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) are major cytokines released by macrophages after inhalation of asbestos. These cytokines can regulate mesothelial cell proliferation both in vitro and in vivo. In the present study, we used the growth in soft agar as an index of transformation and investigated the role of IL-1beta and TNF-alpha during the process of human mesothelial cell carcinogenesis. Both IL-1beta and TNF-alpha were demonstrated to enhance erionite-induced transformation of the immortalised, non-tumorigenic human mesothelial cell line (MeT-5A) in vitro. The MeT-5A cells could only be transformed when the cells were exposed to a combination of cytokines and erionite, or at least two cytokines together without erionite, for at least 4 months in vitro. The findings presented here suggest that IL-1beta and TNF-alpha play a significant role in the pathogenesis of mesothelioma, and that it might be desirable to block or inhibit cytokine secretion in high risk populations to prevent mesothelioma.

Analysis of a three-way race between tumor growth, a replication-competent virus and an immune response

Replication-competent viruses have the potential to overcome the delivery barrier in tumors that has plagued traditional gene-therapy approaches to cancer treatment. However, recent clinical data suggests that a cytokine-based immune response against the virus-infected tumor cells may severely limit the efficacy of the replication-competent approach. This paper generalizes our earlier spatial model to incorporate an immune response against the infected tumor cells. An approximate but accurate condition is derived for the virus-if uniformly injected throughout the tumor-to eradicate the tumor in the presence of the immune response. To validate the model using clinical data describing the temporal interaction of tumor necrosis factor and free virus in the plasma, we needed the immune response to be time-delayed and experience either saturated stimulation or second-order clearance. The resulting estimates of some unknown parameters provide some implications for the delivery of treatment.