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.

Pharmacokinetic and safety study of subcutaneously administered weekly ING-1, a human engineere monoclonal antibody targeting human EpCAM, in patients with advanced solid tumors.

BACKGROUND: ING-1 is a high-affinity, human engineeredtrade mark monoclonal antibody that recognizes a 40 kilodalton epithelial cell adhesion molecule (EpCAM) glycoprotein that is expressed in high levels on most adenocarcinomas and is an attractive target for immunotherapy. METHODS: ING-1 was administered subcutaneously weekly at doses between 0.1 and 2 mg/kg/week. Pharmacokinetic samples were drawn during weeks 1 and 6. RESULTS: Fourteen patients with advanced refractory cancer received a median of 6 (range 1-9) doses of ING-1. At 1 mg/kg, a 62-year-old man with colon cancer developed reversible grade 3 pancreatitis after the third dose. His plasma ING-1 levels were similar to the other two patients dosed at 1 mg/kg. Two patients dosed at 0.6 mg/kg experienced stable disease at 6 weeks. Peak drug levels increased with dose and time, suggesting drug accumulation with repeated dosing. Low human anti-human antibody response was noted in three of the 13 patients assessed and was directed towards the variable region of ING-1. CONCLUSIONS: Weekly ING-1 administered subcutaneously was well tolerated at 0.6 mg/kg/week and further experience at this dose is warranted to demonstrate safety. The risk of pancreatitis and the marginal anti-tumor effect may preclude further monotherapy studies; however, combination studies with chemotherapy are warranted.

Cyclin-dependent kinase and protein kinase C inhibitors: a novel class of antineoplastic agents in clinical development.

Malignant cells have acquired adaptations, which give them a growth and survival advantage over normal cells. One effect of many of these adaptations is that many cancerous cells are less likely to undergo programmed cell death (apoptosis) and, moreover, are resistant to chemotherapy-induced apoptosis. Other features of neoplastic cells are the loss of regulated or orderly progression through the cell cycle. In normal and cancerous cells, a balance between proapoptotic and antiapoptotic signals exists. Protein kinase C (PKC) is a cellular serine/threonine kinase with a central role in the mediation of mitogenic signals as well as the regulation of antiapoptotic signals. Inhibition of PKC by a novel group of chemical agents (PKC inhibitors) can induce apoptosis in some malignant cell lines, act as differentiating agents, and enhance the effect of cytotoxic chemotherapy. Other kinase inhibitors are potent inhibitors of kinases involved in the control of cell cycle progression (cyclin-dependent kinases [cdks]). Cdk inhibitors are able to induce cell cycle arrest in neoplastic cells and also act as enhancers of chemotherapy-induced apoptosis. The catalytic domain of different classes of kinases (PKC and cdk) share considerable homology. As a result, many kinase inhibitors that act by blocking the catalytic site are not highly specific and may act as inhibitors of both PKC and cdks. Preclinical studies point to potential applications for some of these PKC/cdk inhibitors, and current clinical trials are exploring the role these agents might have in cancer therapy. In this article, we discuss the rationale for the development of this novel class of agents and highlight those drugs, which have shown promise in clinical testing.

Up-regulation of amphotrophic retroviral receptor expression in human peripheral blood CD34+ cells.

Retroviral-mediated gene transfer into hematopoietic stem cells provides the only means of stable transduction of these cells and their progeny for use with a variety of potentially therapeutic genes. Expression of the Moloney amphotropic retroviral receptor-pit-2 or GLVR-2-is critical to the recognition and entry of Moloney leukemia virus-derived viruses into human target cells such as CD34+ hematopoietic cells. GLVR-2 functions as a sodium-dependent phosphate transporter as well as a receptor. We have previously shown that the expression of the murine homologue of the amphotropic receptor Ram 1, also a phosphate transporter, is developmentally regulated in murine hematopoietic fetal liver cells. We also demonstrated that culture of murine fetal liver cells in phosphate-free (PO(4)-free) medium increases levels of receptor mRNA and makes murine fetal liver cells susceptible to Moloney amphotropic viral gene transfer. We now examine the effect of culture conditions on the expression of GLVR-2 in human CD34+ cells. In this report, we demonstrate that there is a 2-3 fold increase in GLVR-2 mRNA levels in CD34+ cells after 3 days in culture with interleukin 3, interleukin 6, and stem-cell factor. In addition, the use of PO(4)-free medium increases expression of GLVR-2 an additional 2-fold in these cells during this time. These results indicate that GLVR-2 expression can be up-regulated on these cells, and may permit improved retroviral gene transfer efficiencies.

Phase I trial of retroviral-mediated transfer of the human MDR1 gene as marrow chemoprotection in patients undergoing high-dose chemotherapy and autologous stem-cell transplantation.

PURPOSE: Normal bone marrow cells have little or no expression of the MDR p-glycoprotein product and, therefore, are particularly susceptible to killing by MDR-sensitive drugs, such as vinca alkaloids, anthracyclines, podophyllins, and paclitaxel and its congeners. Here we report the results of a phase I clinical trial that tested the safety and efficacy of transfer of the human multiple drug resistance (MDR1, MDR) gene into hematopoietic stem cells and progenitors in bone marrow as a means of providing resistance of these cells to the toxic effects of cancer chemotherapy. PATIENTS AND METHODS: Up to one third of the harvested cells of patients who were undergoing autologous bone marrow transplantation as part of a high-dose chemotherapy treatment for advanced cancer were transduced with an MDR cDNA-containing retrovirus; these transduced cells were reinfused together with unmanipulated cells after chemotherapy. RESULTS: High-level MDR transduction of erythroid burst-forming unit (BFU-E) and colony-forming unit-granulocyte macrophage (CFU-GM) derived from transduced CD34+ cells was shown posttransduction and prereinfusion. However, only two of the five patients showed evidence of MDR transduction of their marrow at a low level at 10 weeks and 3 weeks, respectively, posttransplantation. The cytokine-stimulated transduced cells may be out-competed in repopulation by unmanipulated normal cells that are reinfused concomitantly. The MDR retroviral supernatant that was used was shown to be free of replication-competent retrovirus (RCR) before use, and all tests of patients' samples posttransplantation were negative for RCR. In addition, no adverse events with respect to marrow engraftment or other problems related to marrow transplantation were encountered. CONCLUSION: These results indicate the feasibility and safety of bone marrow gene therapy with a potentially therapeutic gene, the MDR gene.

Enhanced antigen immunogenicity induced by bispecific antibodies.

The binding of protein antigens to APC with heterocrosslinked bispecific antibodies (HBAs) enhances their processing and presentation to Th cells in vitro. Here we have asked whether HBAs could also increase immune responses in vivo. We immunized mice with hen egg lysozyme (HEL) in the presence or absence of HBA, and followed antibody production after the primary challenge and after a secondary boost. We found that HBAs that bind antigen to MHC class I or II molecules, to Fc gamma R, but not to surface IgD, enhance the immunogenicity of HEL. HBAs that bound HEL to MHC class II molecules, for examples, decreased the amount of antigen required to elicit a primary anti-HEL antibody response in mice by 300-fold, and the amount required to prime for a secondary response by 10(3)- to 10(4)-fold. In fact, HBAs were as effective as IFA in generating antibody responses. Since adjuvants cannot be used in humans, HBAs could prove useful for immunizing people, especially in cases where, due to scarcity or toxicity, minute doses of antigen must be used.

Human K/natural killer cells targeted with hetero-cross-linked antibodies specifically lyse tumor cells in vitro and prevent tumor growth in vivo.

We have induced fresh peripheral blood K/natural killer cells to lyse a variety of target cells by coating them with anti-Fc gamma receptor (anti-Fc gamma R) (CD16) antibody hetero-cross-linked with anti-target cell antibody. The cytotoxic cell mediating this activity is different, as judged by depletion studies, from the CD3+, CD8+ T cell which is targeted by anti-CD3 cross-linked to anti-target cell antibody. Targeted K cell activity from some donors is enhanced by exposure to interleukin 2 but not interferon-gamma; other donors exhibit high amounts of this activity without stimulation. Specificity of lysis mediated by targeted K cells is dictated by the specificity of the anti-target cell antibody within the heteroconjugate, and bystander cells are not lysed by targeted K cells. Hetero-cross-linked antibodies containing anti-histocompatibility leukocyte antigen class I instead of anti-Fc gamma R (CD16) do not promote lysis, suggesting that the bridging of the target cell to Fc gamma R on the K cell is required to activate the lytic process. Lysis mediated by targeted K cells is much less inhibitable by polymerized IgG than is classical antibody-dependent cellular cytotoxicity. Fresh human melanoma cells are lysed specifically by K cells coated with anti-Fc gamma R (CD16) cross-linked to the 96.5 anti-melanoma antibody. In vivo, targeted K cells prevent tumor growth at low effector to target ratios in Winn-type tumor neutralization assays. Targeted K cells may therefore provide a new immunotherapeutic approach for the destruction of detrimental cells, such as tumor and virally infected cells.