Comparative oncology in action: vignettes on immunotherapy development.

Immunotherapeutic approaches to cancer treatment have gained significant traction in recent years, due in large part to the success of immune checkpoint inhibitors and T cell-based therapies. Comparative oncology is the study of naturally-occurring cancer in companion (pet) animals, mainly dogs, and is a powerful tool in cancer research and drug development. Given their intact, educated immune systems and natural co-evolution of tumor, microenvironment and stromal components, tumor-bearing pet dogs are an attractive species in which to explore these cellular interactions and test novel therapeutic approaches. Moreover, similarities between the canine and human immune systems support assessment of a wide variety of approaches, including antagonistic or agonistic antibodies directed at specific cellular targets, tumor vaccines, cell-based therapies, and combinations of these with conventional cancer treatments such as chemotherapy and radiotherapy. This manuscript provides specific examples of how canine immunotherapeutic studies informed an approach destined for human use, with an emphasis on study design, correlative immune assay development and application, and definition of biologic effect.