Drug development can be time-consuming and expensive. Recent estimates suggest that, on average, it takes 10 years and at least $1 billion to bring a drug to market. Given the time and expense of developing drugs de novo, pharmaceutical companies have become increasingly interested in finding new uses for existing drugs - a process referred to as drug repurposing or repositioning. Historically, drug repurposing has been largely an unintentional, serendipitous...