Sources and Targets for Drug Repurposing: Landscaping Transitions in Therapeutic Space.

Patent applications provide unique opportunities for landscaping ongoing medical innovation. In this analysis of drug repurposing patent applications published under the international Patent Convention Treaty during the years 2011-2014, we discuss what categories in the World Health Organization's International Classification of Diseases provide drugs and drug candidates for potential second medical uses, and how these proposed repurposed uses relate to each other and the original ones. Also discussed are the geographic origin of the patent assignees and their type and size. Beyond the expected interactions within the field of neuropsychiatry, frequent secondary use claims for oncology compounds to treat noninfectious respiratory diseases, and for cardiovascular compounds to treat neurological conditions, were unexpected findings derived from the repurposing heatmap. The relative absence of repurposing claims to treat parasitic or tropical diseases contrasts sharply with the broad attention this segment receives in the peer-reviewed literature. Equally notable are the dominance of universities and small pharmaceutical companies; a focus of large multinational companies to repurpose their own compounds; and the leading role of European-centered entities among the assignees. We believe that this investigation represents the first comprehensive cross-sectional attempt at mapping drug repurposing patterns across therapeutic fields, and could provide important clues that complement those obtained from the peer-reviewed literature.