JX-594, a targeted oncolytic poxvirus for the treatment of cancer.

JX-594 is a replication-competent Wyeth strain vaccinia virus that was genetically modified to inactive the endogenous thymidine kinase gene and to express human GM-CSF and LacZ genes. In development by Jennerex Inc and licensee Green Cross Corp, the modified virus is a novel therapy for treatment-refractive metastatic malignancies from various sites of origin. Targeted oncolytic virotherapy has demonstrated promise in preclinical studies, and more than ten viral species have subsequently entered clinical trials. JX-594 has been modified to augment the intrinsic targeting and oncolytic potential of the vaccinia virus and to enhance antitumor immunity by the expression of the GM-CSF transgene in situ. In vitro and in vivo animal studies have demonstrated the replication specificity of JX-594 for cancer cell lines and tumors, and the restriction of serum human GM-CSF expression to tumor-bearing animals, resulting in significantly reduced tumor burden and an increase in median survival. In phase I trials, JX-594 was well tolerated, with mild systemic toxicity reported. In a phase I trial in seven patients with melanoma, one partial response and one complete response after surgery were observed. In another phase I trial in patients with hepatic carcinoma, three out of ten evaluable patients had a partial response and six had stable disease; the MTD was also established. A phase II trial in patients (expected n = 30) with unresectable primary hepatocellular carcinoma was recruiting at the time of publication, with completion expected in March 2010, and a phase III trial in patients with hepatocellular carcinoma was planned for the second half of 2010. Further clinical investigations are needed to explore the potential of this agent as a single therapy and as part of multimodal treatment regimens.

The feasibility of establishing a programme of adjuvant autologous vaccination for renal cell carcinoma.

OBJECTIVE: To report the results of a programme aimed at determining the feasibility of autologous renal cell carcinoma (RCC) tissue collection and vaccine preparation within the setting of a UK National Health Service Cancer Centre. PATIENTS AND METHODS: Patients undergoing nephrectomy for suspected renal tumours were identified from theatre lists between April 2005 and July 2007. Samples of tumour were freshly cut from nephrectomy specimens. If tissue collection failed the reason was recorded prospectively. Cell viability was assessed after sample sieving. Freeze-thaw lysates were prepared from viable tumour cells, and the immunogenicity tested by pulsing onto dendritic cells (DC). RESULTS: Of 84 patients, 83 had a histological diagnosis of RCC; samples were obtained from 29 of these 83 (35%). Reasons for failure in tissue collection included that the tumour was too small or haemorrhagic/necrotic, pre-surgical embolization, and difficulties with fresh tumour collection out of normal working hours. Viable tumour cells were obtained in 12 of the 29 samples (41%); no factor was able to predict the production of viable cells. Unmodified lysates did not activate DC. CONCLUSION: An autologous RCC vaccination programme might fail to generate vaccines for a substantial proportion of eligible patients in the setting of a clinical cancer centre.

Optimization of dendritic cell loading with tumor cell lysates for cancer immunotherapy.

The immune response to cancer is critically determined by the way in which tumor cells die. As necrotic, stress-associated death can be associated with activation of antitumor immunity, whole tumor cell antigen loading strategies for dendritic cell (DC)-based vaccination have commonly used freeze-thaw "necrotic" lysates as an immunogenic source of tumor-associated antigens. In this study, the effect of such lysates on the ability of DCs to mature in response to well-established maturation stimuli was examined, and methods to enhance lysate-induced DC activation explored. Freeze-thaw lysates were prepared from murine tumor cell lines and their effects on bone marrow-derived DC maturation and function examined. Unmodified freeze-thaw tumor cell lysates inhibited the toll-like receptor-induced maturation and function of bone marrow-derived DCs, preventing up-regulation of CD40, CD86, and major histocompatibility complex class II, and reducing secretion of inflammatory cytokines [interleukin (IL)-12 p70, tumor necrosis factor-alpha, and IL-6]. Although IL-10 secretion was increased by lysate-pulsed DCs, this was not responsible for the observed suppression of IL-12. Although activation of the nuclear factor-kappaB pathway remained intact, the kinase activity of phosphorylated p38 mitogen-activated protein kinase was inhibited in lysate-pulsed DCs. Lysate-induced DC suppression was partially reversed in vitro by induction of tumor cell stress before lysis, and only DCs loaded with stressed lysates afforded protection against tumor challenge in vivo. These data suggest that ex vivo freeze-thaw of tumor cells does not effectively mimic in vivo immunogenic necrosis, and advocates careful characterization and optimization of tumor cell-derived vaccine sources for cancer immunotherapy.