This work discusses the history of a genetic mutation, discovered in 1959, that causes chronic myeloid leukemia, and traces the research and breakthroughs that led to the creation of a drug that makes this once-fatal illness now treatable. It focuses on what is widely viewed as the 'poster child' of rational drug development in the cancer research world. The history of the founding of a genetic mutant chromosome in the indication of Chronic myeloid leukemia disease, and the subsequent development of "Gleevec," is the keynote of this publication.