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Manipulating different arms of the immune system to orchestrate tumor-specific immunity and enhance tumor clearance

Final Report Summary - IMMUNOTHERAPY (Manipulating different arms of the immune system to orchestrate tumor-specific immunity and enhance tumor clearance)

Oncolytic adenoviruses are viruses that have been engineered to selectively replicate in and kill cancer cells. For long time it has been believed that the mode of action of these agents was the simple oncolysis of tumor cells. The present application was the first tentative to challenge this paradigm hypothesizing that in addition to the direct oncolysis these viruses had also the ability to interact with the host immune system providing a sort of vaccine in situ and consequently eliciting a long-lasting anti-tumor immunity. We proposed to exploit this feature with different strategies to direct or enhance the anti-tumor immunity even further. To this end we proposed: (I) to generate an oncolytic adenovirus expressing the human Granulocyte macrophage colony-stimulating factor (GMCSF) to recruit antigen-presenting cells (II) to incorporate CpG islands into the adenoviral genome to stimulate the innate sensors of double-stranded DNA (TLR9) during viral replication (III) finally we proposed a combination of these two approaches.

Firstly we created an oncolytic adenovirus expressing GMCSF. This virus was tested in a variety of human xenograph tumor model in mice. This virus was also shown to provide a long-term vaccine effect in a fully immunocompetent animal model (Syrian Hamsters bearing syngeneic tumors). Importantly the efficacy of the toxicity analysis of this agents were so promising that it was decided to use it in a clinical setting in human patients refractory to conventional therapy. An extensive analysis of toxicity and efficacy of this agent has been published (Oncolytic adenovirus coding for granulocyte macrophage colony-stimulating factor induces antitumoral immunity in cancer patients. Cerullo V, et al., Cancer Res. 2010 Jun 1;70(11):4297-309. Epub 2010 May 18). Moreover the efficacy of this virus has been enhanced even further in combination with low dose cyclophosphamide to reduce number and activity of regulatory T cell at tumor site Immunological Effects of Low-dose Cyclophosphamide in Cancer Patients Treated With Oncolytic Adenovirus. Cerullo V, et al., Mol Ther. 2011 Sep;19(9):1737-46. doi: 10.1038/mt.2011.113. Epub 2011 Jun 14).

Subsequently we proposed another strategy to enhance the adjuvancy of the adenoviral DNA, more specifically we generated a novel oncolytic adenovirus whose genome was enriched of CpG island to iper-stimulate Toll-Like Receptor 9 (TLR9) during capsid disassembly in the endosome (where TLR9 is located) and consequently enhance the vaccine effect. With this work we demonstrated that our new concept of oncolytic adenovirus was able to trigger a tumor-specific immune response significantly better and for longer compared to any other virus present at the moment without altering the toxicity of the agent. This work has been discussed orally at the American Society of Gene and Cell therapy several times and the it has been published in a prestigious journal in the field of gene therapy (An oncolytic adenovirus enhanced for toll-like receptor 9 stimulation increases antitumor immune responses and tumor clearance. Cerullo V. et al., Mol Ther. 2012 Nov;20(11):2076-86. doi: 10.1038/mt.2012.137. Epub 2012 Jul 24).

Finally we have generated “super-vector” that has a CpG enriched genome, expresses GMCSF, has a chimeric fiber to better enter cancer cells and finally has double-check control to limit its replication in normal cells even more. The results with this virus are very promising and we are at the moment considering it for a future clinical trials in human cancer patients.

Overall, this grant application (FP7-IRG-MC-PEOPLE) has been for the scientific community and for my career extremely useful. It has contributed to the publication of several very important papers, it has significantly contributed to the advance of my career from postdoc to a tenure-track assistant professor but, most importantly it has contributed to set the science behind several clinical trials and treatments with more than 200 patients treated to date.