Sergio A. Acuna

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.

Mounting a strategic offense: fighting tumor vasculature with oncolytic viruses

Blood supply within a tumor drives progression and ultimately allows for metastasis. Many anticancer therapies target tumor vasculature, but their individual effectiveness is limited because they induce indirect cell death. Agents that disrupt nascent and/or established tumor vasculature while simultaneously killing cancer cells would certainly have a greater impact. Oncolytic virotherapy utilizes attenuated viruses that replicate specifically within a tumor. They induce cytotoxicity through a combination of direct cell lysis, antitumor immune stimulation, and recently identified antitumor vascular effects. This review summarizes the novel preclinical and clinical evidence regarding the antitumor vascular effects of oncolytic viruses, which include infection and lysis of tumor endothelial cells, natural or genetically engineered antiangiogenic properties, and combination therapy with clinically approved antivascular agents.

Oncolytic vaccinia virus synergizes with irinotecan in colorectal cancer.

Metastatic colorectal cancer (CRC) is complex clinical challenge for which there are limited treatment options. Chemotherapy with or without surgery provides moderate improvements in overall survival and quality of life; nevertheless the 5‐year survival remains below 30%. Oncolytic vaccinia virus (VV) shows strong anti‐tumour activity in models of CRC, however transient delays in disease progression are insufficient to lead to long‐term survival. Here we examined the efficacy of VV with oxaliplatin or SN‐38 (active metabolite of irinotecan) in CRC cell lines in vitro and VV with irinotecan in an orthotopic model of metastatic CRC. Synergistic improvements in in vitro cell killing were observed in multiple cell lines. Combination therapy was well tolerated in tumour‐bearing mice and the median survival was significantly increased relative to monotherapy despite a drug‐dependent decrease in the mean tumour titer. Increased apoptosis following in vitro and in vivo combination therapy was observed. In vitro cell cycle analysis showed increases in S‐phase cells following infection occurred in both infected and uninfected cell populations. This corresponded to a 4‐fold greater increase in apoptosis in the uninfected compared to infected cells following combination therapy. Combination treatment strategies are among the best options for patients with advanced cancers. VV is currently under clinical investigation in patients with CRC and the data presented here suggest that its combination with irinotecan may provide benefit to a subset of CRC patients. Further, investigation of this combination is necessary to determine the tumour characteristics responsible for mediating synergy.

Tumor vascularization is critical for oncolytic vaccinia virus treatment of peritoneal carcinomatosis

Peritoneal carcinomatosis (PC) represents a significant clinical challenge for which there are few treatment options. Oncolytic viruses are ideal candidates for PC treatment because of their high tumor specificity, excellent safety profile and suitability for peritoneal delivery. Here, we described the use of vvDD‐SR‐RFP, a recombinant vaccinia virus, in xenograft and syngeneic models of colorectal PC. Colorectal cancer cell lines were highly susceptible to vvDD‐SR‐RFP replication and cytotoxicity. Intraperitoneal delivery of vvDD‐SR‐RFP on Day 12 to mice with colorectal carcinomatosis significantly improved survival whereas survival was not improved following virus treatment on Day 8, when tumors were smaller. Immunohistochemistry revealed early tumors had a poorly distributed network of blood vessels and lower proliferation index compared to later tumors. Virus infection was also restricted to tumor rims following Day 8 treatment, whereas it was disseminated in tumors treated on Day 12. Additionally, direct infection of tumor endothelium was observed and virus infection correlated with a loss of endothelial staining and induction of cell death. Our results demonstrate that tumor vasculature has a critical role in virus delivery and tumor response. This will have significant implications in the clinical setting, both in understanding timing of therapies and in designing combination treatment strategies.

Oncolytic vaccinia virus as an adjuvant treatment to cytoreductive surgery for malignant peritoneal mesothelioma.

BackgroundMalignant peritoneal mesothelioma (MPM) is an aggressive cancer with a dismal prognosis. Oncolytic viruses are a promising new therapy for cancer because of their ability to kill tumor cells with minimal toxicity to normal tissues. This experimental study aimed to examine the potential of modified vaccinia virus (VV) to treat MPM when administered alone or as an adjuvant treatment to surgery.MethodsTwo aggressive murine mesothelioma cell lines (AC29, AB12), were used. Cell viability and viral cytopathic effects were assessed using MTS and crystal violet assays. Immunocompetent mice were injected intraperitoneally with MPM cells and treated with intraperitoneal VV. Tumor-bearing mice also underwent cytoreductive surgery (CRS) followed by VV (or control) therapy.ResultsThe cytotoxic effects of VV on MPM cell lines was significantly increased compared with the control non-cancer cell line. In both orthotopic models, VV induced tumor regression, prolonging median and long-term survival. VV treatment after incomplete CRS was not superior to VV alone; however, when mice with microscopic disease were treated with VV, further prolongation of median and long-term survivals was observed.ConclusionsVV selectively kills MPM cells in vitro and leads to improved survival and cures in immunocompetent murine models. Higher efficacy of the virus in the microscopic disease context suggests the use of the virus as an adjuvant treatment to complete surgical resection. These promising results justify further studies of VV in humans as a novel treatment for MPM.

Quality indicators for sentinel lymph node biopsy: Is there room for improvement?

BACKGROUND Eleven quality indicators (QI) for sentinel lymph node biopsy (SLNB) were previously developed through a consensus-based approach, yet still need to be incorporated into clinical practice. We sought to evaluate the applicability and clinical relevance for surgeons. METHODS Breast cancer patients undergoing SLNB between 2004 and 2008 at Mount Sinai Hospital, Toronto, were evaluated. Clinical and pathological data were obtained from an institutional database. Information on axillary recurrences was obtained through a retrospective chart review. Adherence to standardized protocols was evaluated in each case. RESULTS All 11 QIs were measurable in 300 patients. The identification rate was 100%. More than 1 SLN was identified in 78.6% of patients. The SLNB was performed simultaneously with primary surgery in 96.7% of patients; 61 SLNs harboured metastasis. Of these patients, 80.3% underwent completion lymphadenectomy. Cases complied with protocols for radiocolloid injection and pathologic SLN evaluation/reporting. No ineligible patients underwent SLNB. Of patients with a complete 5-year follow-up (n = 42), only 1 had axillary recurrence. CONCLUSION Applying QIs for SLNB was feasible, but modifications were necessary to develop a more practical approach to quality assessment. Of the 11 suggested QIs, those that encompass protocols (nuclear medicine and pathology) should be reclassified as prerequisites, as they are independent of the technical aspect of SLNB performance. The remaining 8 QIs encompass surgery per se and should be measured routinely by surgeons. Furthermore, concise and clinically relevant target rates are necessary for these QIs to be established as widely recognized control standards.

Preclinical evaluation of a MAGE-A3 vaccination utilizing the oncolytic Maraba virus currently in first-in-human trials

ABSTRACT Multiple immunotherapeutics have been approved for cancer patients, however advanced solid tumors are frequently refractory to treatment. We evaluated the safety and immunogenicity of a vaccination approach with multimodal oncolytic potential in non-human primates (NHP) (Macaca fascicularis). Primates received a replication-deficient adenoviral prime, boosted by the oncolytic Maraba MG1 rhabdovirus. Both vectors expressed the human MAGE-A3. No severe adverse events were observed. Boosting with MG1-MAGEA3 induced an expansion of hMAGE-A3-specific CD4+ and CD8+ T-cells with the latter peaking at remarkable levels and persisting for several months. T-cells reacting against epitopes fully conserved between simian and human MAGE-A3 were identified. Humoral immunity was demonstrated by the detection of circulating MAGE-A3 antibodies. These preclinical data establish the capacity for the Ad:MG1 vaccination to engage multiple effector immune cell populations without causing significant toxicity in outbred NHPs. Clinical investigations utilizing this program for the treatment of MAGE-A3-positive solid malignancies are underway (NCT02285816, NCT02879760).

Defining Non-inferiority Margins for Quality of Surgical Resection for Rectal Cancer: A Delphi Consensus Study

Quality of surgical resection metrics (QSRMs) have been used as surrogates for long-term oncologic outcomes in non-inferiority randomized clinical trials (RCTs) comparing laparoscopic and open surgery for rectal cancer. However, non-inferiority margins (ΔNI) for QSRMs have not been previously defined. A two-round, web-based Delphi was used to define ΔNI for four QSRMs: positive circumferential resection margin (CRM), incomplete plane of mesorectal excision (PME), positive distal resection margin (DRM), and a composite of these outcomes. Overall, 130 international experts in rectal cancer (68 surgeons, 20 medical oncologists, 16 radiation oncologists, and 26 pathologists) were invited to participate. Experts were presented with evidence syntheses summarizing the association between QSRMs and long-term outcomes, and pooled quality of surgical resection outcomes for open surgery, and were asked to provide ΔNI for all outcomes balancing the risks and benefits of minimally invasive surgery. Seventy-two experts participated: 57 completed the initial questionnaire and 58 completed the revised questionnaire, with 43 participating in both rounds. Consensus was reached for all individual QSRM ΔNI but not for the composite. The mean (standard deviation) ΔNI was an absolute difference of 2.33% (1.59%) for the proportion of positive CRMs when comparing surgical interventions for the treatment of rectal cancer: 2.85% (1.83%) for incomplete PME; 1.28% (1.13%) for positive DRMs; and 2.71% (2.28%) for the composite. However, opinions varied widely for the composite outcome. Web-based Delphi processes are a feasible approach to generate ΔNI to evaluate novel surgical interventions. The generated ΔNI for QSRMs for rectal cancer can be used for future RCTs and non-inferiority meta-analyses.IntroductionQuality of surgical resection metrics (QSRMs) have been used as surrogates for long-term oncologic outcomes in non-inferiority randomized clinical trials (RCTs) comparing laparoscopic and open surgery for rectal cancer. However, non-inferiority margins (ΔNI) for QSRMs have not been previously defined.MethodsA two-round, web-based Delphi was used to define ΔNI for four QSRMs: positive circumferential resection margin (CRM), incomplete plane of mesorectal excision (PME), positive distal resection margin (DRM), and a composite of these outcomes. Overall, 130 international experts in rectal cancer (68 surgeons, 20 medical oncologists, 16 radiation oncologists, and 26 pathologists) were invited to participate. Experts were presented with evidence syntheses summarizing the association between QSRMs and long-term outcomes, and pooled quality of surgical resection outcomes for open surgery, and were asked to provide ΔNI for all outcomes balancing the risks and benefits of minimally invasive surgery.ResultsSeventy-two experts participated: 57 completed the initial questionnaire and 58 completed the revised questionnaire, with 43 participating in both rounds. Consensus was reached for all individual QSRM ΔNI but not for the composite. The mean (standard deviation) ΔNI was an absolute difference of 2.33% (1.59%) for the proportion of positive CRMs when comparing surgical interventions for the treatment of rectal cancer: 2.85% (1.83%) for incomplete PME; 1.28% (1.13%) for positive DRMs; and 2.71% (2.28%) for the composite. However, opinions varied widely for the composite outcome.ConclusionsWeb-based Delphi processes are a feasible approach to generate ΔNI to evaluate novel surgical interventions. The generated ΔNI for QSRMs for rectal cancer can be used for future RCTs and non-inferiority meta-analyses.