Drug Repositioning: Concept, Classification, Methodology, and Importance in Rare/Orphans and Neglected Diseases

The development of new drugs is a long and complex process, with extremely high investment and small expectation of success. In recent years, there was a significant decline in the number of new drugs approved for clinical use, notwithstanding powerful tools were developed to support the research and development (R&D) process. Drug Discovery programs are pursuing strategies that optimize the R&D process. Among them, we highlight the drug repositioning as an approach that seeks new therapeutic applications for already approved drugs, different from its initial indication. This strategy is aimed to reduce costs and research time considerably. There is a limited commercial interest in the development of drugs for the treatment of rare/orphans and neglected diseases, due to the onerous nature, the associated risk and low return on investments in R&D. Thus, repositioning is important, due to the advantages over traditional approaches, to an area that has historically suffered from limited resources and an enormous need for effective therapies. Herein, this review discussed recent data about drug repositioning as an important strategy for the development of new therapies for the treatment of rare/orphans and neglected diseases.