Drug repositioning: identifying and developing new uses for existing drugs

The process of finding new uses outside the scope of the original medical indication for existing drugs is known as drug repositioning. Repositioning existing drugs for new indications can offer a better risk-versus-reward trade-off as compared with other drug development strategies, and can help to deliver the productivity increases the industry needs while shifting the locus of production to biotechnology companies. Representative repositioning success stories include: duloxetine, which was originally developed for depression and is now at the US FDA as a first-in-class therapy for stress urinary incontinence; dapoxetine, which was passed over as a follow-on to fluoxetine (Prozac) and is now undergoing Phase III clinical trials as a first-in-class therapy for premature ejaculation; and thalidomide, which had a tragic beginning as an over-the-counter sedative for morning sickness in Germany and England and is now being used to treat leprosy and multiple myeloma. Challenges unique to the repositioning field include: discovering and validating the repositioning idea in the face of incomplete or antiquated data and identifying the repositioning candidate; developing novel clinical trial designs for indications that have never been pursued before; identifying and overcoming patents that could impede commercialization and developing new barriers to entry strategies. Pharmaceutical companies might own most of the raw material for repositioned drugs, but the initiative and insight to screen them for novel uses usually comes from biotech companies, who possess the ideal combination of incentives to pursue new indications for existing drugs given their level of entrepreneurship, motivation (succeed or die) and institutional flexibility.