What patents tell us about drug repurposing for cancer: A landscape analysis

Intellectual property documents (patents and their published applications) are not only collections of legal exclusivity claims but also repositories of scientific and technical information, even though they are not peer reviewed. We have identified and analyzed international disclosures concerning drug repurposing for cancer that were published under the Patent Convention Treaty during the past five years, and show this burgeoning field from an angle that is not routinely captured in review papers of the field. We find that patenting activity for cancer-related new uses for known compounds has been quite constant recently and has targeted mainly small molecule active ingredients that are currently marketed as drugs. Universities contributed most applications, closely followed by corporations. The strong representation of non-academic research institutes from the public and private sector and foundations was surprising and indicates that drug repurposing for cancer has transcended the classical corporate-academia dichotomy. Many of the identified patent documents report findings that are not reflected in the peer review literature (e.g., sumatriptan for mycosis fungoides) or appear there only later (e.g., ibudilast for glioblastoma). Synergistic combinations of several repurposed compounds were also identified, as were two documents related to the repurposing of vaccines. Our findings underscore the necessity for drug repurposers as well as for oncologists to investigate patent documents in addition to the usual peer review literature search to obtain a comprehensive perspective of the state of the art.