Combining Radiation, Allogeneic Natural Killer Immunotherapy, and PD-L1 blockade in Dogs with Naturally-Occurring Melanoma

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PROJECT SUMMARY/ABSTRACT Although immunotherapy, especially immune checkpoint inhibition (ICI) with PD-1/PD-L1 inhibitors, has rapidly become the fourth pillar in cancer therapy with increasing breakthrough advances, barriers still exist to its success. Given their ability to rapidly exert their cytotoxic effects on heterogeneous tumor cells with minimal adverse events, natural killer (NK) cells have emerged as promising tools to expand the benefits of cancer immunotherapy, including for patients who never start or stop responding to ICI. However, lack of consistent responses in human NK cell trials, especially for solid tumors, calls for innovative methods to successfully translate novel NK immunotherapy approaches to the clinic. Dogs with cancer are an excellent way to assess novel immunotherapies because they recapitulate fundamental clinical and genetic features of human cancers, including the development of spontaneous tumors in the setting of an intact immune system. To speed translation of NK immunotherapy approaches, the proposed project will test an innovative treatment of allogeneic NK adoptive transfer in combination with a novel caninized anti-PD-L1 antibody developed by our comparative oncology group. Using a co-clinical Phase II trial format, dogs with locally advanced melanoma will be treated with radiation therapy (RT), adoptive transfer of expanded/activated allogeneic NK cells from healthy beagle donors, and immune checkpoint blockade using our dog anti-PD-L1 antibody. As the first trial to use NK cell transfer in combination with ICI on spontaneous tumors in a clinical setting, the results of this study will provide potentially transformative insights into mechanisms of both therapies and will evaluate barriers for future first-in- human trials on solid tumors. Since NK cell activity is known to be mediated by the PD-1/PD-L1 axis with PD-L1 being a critical inhibitory NK marker, the proposed study will offer critical insight into potential mechanisms of overcoming NK dysfunction responsible for unimpressive responses with NK cell immunotherapies alone. Furthermore, RT is part of the standard of care for unresectable malignancies and has been shown to have important immunomodulatory effects, including sensitization of tumor cells to NK cytotoxicity. The Canter Lab is a leader in canine clinical trials as well as their use as tools to perform multidimensional analyses of NK cells. Similarly, the potentially high impact of this novel immuno-oncology (IO) therapy will be studied through extensive correlative studies including flow cytometry to follow the regional differences of donor and endogenous NK cells, killing assays to assess changes in cytotoxicity, and RNA sequencing to characterize differential gene expression of relevant immune populations. Although we hypothesize meaningful clinical and immunologic effects from this novel therapy, we will nevertheless gain key insights into the dog as a comparative model for future dog and human IO studies. Thus, beyond the potential for significant scientific and clinical impact, the completion of this study will provide me with cutting edge training in comparative cancer immunotherapy to prepare me for a successful career as a veterinary scientist in cancer immunology and NK immunotherapy.