Second era of molecular-targeted cancer therapies in dogs

The development of molecular biology and bioinformatics using next-generation sequencing has dramatically advanced the identification of molecules involved in various diseases and the elucidation of their pathogenesis. Consequently, many molecular-targeted therapies have been developed in the medical field. In veterinary medicine, the world's first molecular-targeted drug for animals, masitinib, was approved in 2008, followed by the multikinase inhibitor toceranib in 2009. Toceranib was originally approved for mast cell tumors in dogs but has also been shown to be effective in other tumors because of its ability to inhibit molecules involved in angiogenesis. Thus, toceranib has achieved great success as a molecular-targeted cancer therapy for dogs. Although there has been no progress in the development and commercialization of new molecular-targeted drugs for the treatment of cancer since the success of toceranib, several clinical trials have recently reported the administration of novel agents in the research stage to dogs with tumors. This review provides an overview of molecular-targeted drugs for canine tumors, particularly transitional cell carcinomas, and presents some of our recent data.