LOAd703 and beyond : Advancing immunostimulatory gene therapy for cancer
Abstract: In the last decade, immunotherapy has come into the limelight of cancer treatments. Immunotherapy aims to stimulate the body’s own immune system to create or reinvigorate anti-tumor immune responses. Impressive results with long-term remissions have been achieved in patients with B-cell malignancies and malignant melanoma treated with chimeric-antigen receptor (CAR) T cells and immune checkpoint inhibitors, respectively. However, many patients still do not respond to these therapies or relapse. Oncolytic virotherapy represents an immunotherapy approach, in which viruses are programed to selectively replicate in tumor cells, thereby leading to direct tumor cell killing. Moreover, these viruses can be modified to introduce therapeutic transgenes into the tumor microenvironment.In this thesis, I evaluated oncolytic viruses from the Lokon Oncolytic Adenovirus (LOAd) platform. These viruses are engineered to express immunostimulatory transgenes that specifically activate cells central in the induction of anti-tumor immunity, such as dendritic cells (DCs), T cells and natural killer (NK) cells. The herein investigated viruses are LOAd703 and LOAd732, which both express CD40L and 4-1BBL, while LOAd732 additionally expresses IL-2. In paper I, we assessed the immunological status of advanced cancer patients treated with LOAd703 in combination with chemotherapy in the LOKON002 trial. We showed that intratumoral LOAd703 treatment could mediate inflammation in patients’ tumors as seen by an induction of multiple inflammatory genes, including gene profiles associated with response to checkpoint inhibition. In addition, there was a distinct profile for responding patients. In paper II, we demonstrated that LOAd703 therapy is feasible in B-cell lymphoma and that it can be combined with CAR T-cell therapy as priming lymphoma cells with LOAd703 enhanced the secretion of chemokines promoting T-cell migration and boosted the cytotoxic T-cell function leading to better lymphoma cell killing. In paper III, we showed in vivo in a melanoma model that a murine version of LOAd703 could induce anti-tumor immune responses, sensitize tumors to checkpoint inhibitors and facilitate systemic immune responses in a twin-tumor model, in particular when combined with anti-PD-L1. In paper IV, we present a novel virus, LOAd732, and its functionality was confirmed in regards to the oncolytic capability, transgene expression and immunostimulatory effect. LOAd732 activated DCs that were capable of stimulating antigen-specific T cells, as well as NK cells. Moreover, LOAd732-stimulated cells could withstand immunosuppression mediated by cytokines (TGF-β1, IL-10) commonly present in the microenvironment of many tumors.
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