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Drug repositioning: identifying and developing new uses for existing drugs

Key Points

  • 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.


Biopharmaceutical companies attempting to increase productivity through novel discovery technologies have fallen short of achieving the desired results. Repositioning existing drugs for new indications could deliver the productivity increases that the industry needs while shifting the locus of production to biotechnology companies. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing.

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Figure 1: The growing productivity gap in the biopharmaceutical industry.
Figure 2: A comparison of traditional de novo drug discovery and development versus drug repositioning.
Figure 3: The risk-versus-reward trade off between different drug development strategies.

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We would like to thank L. A. Asinas, M. Boshar, L. R. Brettman, S. Dickman, G. Kaplan, S. A. Holmes, S. B. Landau, J. D. Leander, R. C. Lorette and H. E. Wendler for helpful discussions in the preparation of this manuscript.

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Correspondence to Ted T. Ashburn.

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T.T.A. and K.B.T. are employed by and own stock in Dynogen Pharmaceuticals, Inc.

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Entrez Gene




Pharmaceutical Industry Profile 2004

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US Food and Drug Administration



Also known as a 5-hydroxytryptamine (5-HT), a chemical neurotransmitter contained in a specific subpopulation of neurons in the central nervous system and in the enteric nervous system. Because changes in serotonin levels in the brain can alter mood, medications that affect the action of serotonin are commonly used to treat depression.


A catecholamine neurotransmitter contained in a specific subpopulation of neurons in the central nervous system and in sympathetic post-ganglionic neurons of the peripheral autonomic nervous system.


(MOU). A patent containing one or more claims directed to a method of use (for example, a method of treating disease X, comprising administering a therapeutically effective amount of product Y to a subject in need thereof). The exclusionary right is limited to the particular use claimed.


(COGS). The expense a company incurs to manufacture a drug product for sale. Often includes labour, materials, overhead and depreciation associated with the manufacturing process.


The study of therapeutic and/or toxic effects that pharmacologically active substances have on biological systems. In other words, 'the study of what the drug does to the body'.


The study of the rates of the movements of drugs within biological systems as affected by absorption, distribution, metabolism and elimination (ADME). In other words, 'the study of what the body does to the drug.'


(NDA). An application to the US FDA to market a new drug in the United States that contains data gathered during the animal studies, human clinical trials of an Investigational New Drug (IND) and also data on chemistry, manufacturing and controls (CMC). Every new drug since 1938 has been the subject of an approved NDA before US commercialization.


(COM). A patent containing one or more claims directed to a composition of matter or product per se, such as a small molecule, protein, nucleic acid or particular formulation of an agent.

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Ashburn, T., Thor, K. Drug repositioning: identifying and developing new uses for existing drugs. Nat Rev Drug Discov 3, 673–683 (2004).

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