1. ¹VirRx Inc., St. Louis, Missouri, USA
2. ²Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
3. ³Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota, USA

Correspondence: Konstantin Doronin, Mayo Clinic, Guggenheim 5-16, 200 First Street SW, Rochester, Minnesota 55902, USA. E-mail: doronin.konstantin@mayo.edu

Received 30 August 2006; Accepted 30 October 2006; Published online 26 December 2006.

Abstract

Novel approaches are needed to improve the antitumor potency and to increase the cancer specificity of oncolytic adenoviruses (Ad). We hypothesized that the combination of interferon-alpha (IFN-) expression with a specific mutation in the e1a gene of Ad could target vector replication to genetic defects in the IFN- pathway resulting in both improved antitumor efficacy and reduced toxicity. The conditionally replicative Ad vector KD3-IFN carries the dl1101/1107 mutation in the e1a gene that eliminates binding of E1A proteins to p300/CBP and pRb. KD3-IFN expresses human IFN- in concurrence with vector replication and overexpresses the adenovirus death protein (ADP; E3-11.6K). The antitumor activity of KD3-IFN was significantly higher than that of a control vector in established human hepatocellular carcinoma tumors in immunodeficient mice and in hamster kidney cancer tumors in immunocompetent Syrian hamsters. The dl1101/1107 mutation rendered Ad replication sensitive to the antiviral effect of IFN- in normal as opposed to cancer cells. These results translated to reduced vector toxicity upon systemic administration to C57BL/6 mice. The combination of Ad oncolysis, ADP overexpression, and IFN--mediated immunotherapy represents a three-pronged approach for increasing the anticancer efficacy of replicative Ads. Exploiting the dl1101/1107 mutation provides a mechanism for additional selectivity of IFN--expressing replication-competent Ads.