Canine models of inherited bleeding disorders in the development of coagulation assays, novel protein replacement and gene therapies

Animal models of inherited bleeding disorders are important for understanding disease pathophysiology and are required for preclinical assessment of safety prior to testing of novel therapeutics in human and veterinary medicine. Experiments in these animals represent important translational research aimed at developing safer and better treatments, such as plasma-derived and recombinant protein replacement therapies, gene therapies and immune tolerance protocols for antidrug inhibitory antibodies. Ideally, testing is done in animals with the analogous human disease to provide essential safety information, estimates of the correct starting dose and dose response (pharmacokinetics) and measures of efficacy (pharmacodynamics) that guide the design of human trials. For nearly seven decades, canine models of hemophilia, von Willebrand disease and other inherited bleeding disorders have not only informed our understanding of the natural history and pathophysiology of these disorders but also guided the development of novel therapeutics for use in humans and dogs. This has been especially important for the development of gene therapy, in which unique toxicities such as insertional mutagenesis, germ line gene transfer and viral toxicities must be assessed. There are several issues regarding comparative medicine in these species that have a bearing on these studies, including immune reactions to xenoproteins, varied metabolism or clearance of wild-type and modified proteins, and unique tissue tropism of viral vectors. This review focuses on the results of studies that have been performed in dogs with inherited bleeding disorders that closely mirror the human condition to develop safe and effective protein and gene-based therapies that benefit both species.