Antitumor efficacy and tumor-selective replication with a single intravenous injection of OAS403, an oncolytic adenovirus dependent on two prevalent alterations in human cancer.

A potentially promising treatment of metastatic cancer is the systemic delivery of oncolytic adenoviruses. This requires engineering viruses which selectively replicate in tumors. We have constructed such an oncolytic adenovirus, OAS403, in which two early region genes are under the control of tumor-selective promoters that play a role in two key pathways involved in tumorigenesis. The early region E1A is controlled by the promoter for the E2F-1 gene, a transcription factor that primarily upregulates genes for cell growth. The E4 region is under control of the promoter for human telomerase reverse transcriptase, a gene upregulated in most cancer cells. OAS403 was evaluated in vitro on a panel of human cells and found to elicit tumor-selective cell killing. Also, OAS403 was less toxic in human hepatocyte cultures, as well as in vivo when compared to an oncolytic virus that lacked selective E4 control. A single intravenous injection of 3 x 10(12) vp/kg in a Hep3B xenograft mouse tumor model led to significant antitumor efficacy. Additionally, systemic administration in a pre-established LNCaP prostate tumor model resulted in over 80% complete tumor regressions at a tolerable dose. Vector genome copy number was measured in tumors and livers at various times following tail vein injection and showed a selective time-dependent increase in tumors but not livers over 29 days. Furthermore, efficacy was significantly improved when OAS403 treatment was combined with doxorubicin. This virus holds promise for the treatment of a broad range of human cancers including metastatic disease.

Evaluation of the duration of human factor VIII expression in nonhuman primates after systemic delivery of an adenoviral vector.

An E1/E2a/E3-deficient adenoviral vector encoding an epitope-tagged (flagged) human factor VIII (FVIII) cDNA was delivered systemically to four cynomolgus monkeys. Analysis of liver biopsy samples revealed the presence of vector DNA at all points in the study (day 7, 28, and 56), with vector copy number declining approximately 10-fold between day 7 and day 56. Immunoprecipitation/Western analyses detected human flagged FVIII in the plasma of all monkeys and expression persisted for 14-28 days. Peak plasma FVIII levels ranged from 50 to 100 ng/ml. Bethesda assays revealed no inhibitor in two animals, the development of a low-level transient inhibitor in one animal, and an inhibitor titer that continued to increase for the duration of the study in one animal. Other treatment-related changes included modest increases in liver enzymes, an increase in interleukin-6 (IL-6) levels, and a transient decrease in platelets in all four animals. These data indicate that early generation adenoviral vectors do not support the long-term expression of FVIII in nonhuman primates.