Oncolytic Adenovirus Therapy for Solid Tumors Through Induction of Xenogeneic Rejection : Preclinical Proof of Concept and Safety for Adf35(OGN)

Cancer immunotherapy has improved the survival for a substantial proportion of cancer patients but for many cancers treatment is still lacking and, hence, there is a great need to further develop cancer immunotherapies for the future benefit of more patients. Oncolytic adenoviruses with various immunostimulatory transgenes have previously been well tolerated in clinical trials of cancer treatment. They are used both for their oncolytic and immunostimulatory effect but also as delivery platform of transgenes in cancer gene therapy. We have constructed an oncolytic adenovirus, Adf35(OGN), with transgenic expression of alpha-1,3-galactosyltransferase (GGTA1) from Sus scrofa, synthesizing the immune stimulatory glycosylation Galactose-α-1,3-galactose (α-gal) and neutrophil activating protein (NAP) from Helicobacter pylori, an immunomodulatory protein. a-gal and NAP are potent activators and modulators of the human immune system and have not previously been combined in cancer immunotherapy. In paper I, Adf35(OGN) was shown to effectively infect human pancreatic tumor cells which further led to expression of α-gal and NAP, antibody opsonization and complement deposition on infected cells, complement and antibody dependent cellular cytotoxicity and activation of various immune cells. Furthermore, when Adf35(OGN) was injected intratumorally in pancreatic tumors in mouse, tumor growth was inhibited and mouse survival improved. In paper II, a simple qPCR-based assay is presented that can be used to quantify replication competent adenoviruses, accidently formed during production, in batches of oncolytic adenoviruses intended for use in clinical trials to ensure levels below acceptable limits. In paper III, to evaluate the safety of Adf35(OGN), biodistribution and toxicity was studied in Syrian hamster and mouse. The viral treatment was well tolerated without treatment-related toxicity or viral replication in tissues and the shedding of virus to the environment was sparse. In paper IV, various enzymes and polycations were evaluated as vehicles for intratumoral injections of oncolytic adenoviruses. Hyaluronidase tripled viral transduction and may be considered to improve the treatment efficacy of oncolytic viruses. In conclusion, the preclinical efficacy and safety results presented in the thesis encourage future clinical trials with Adf35(OGN).