Repurposing Existing Medicines for New Indications

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Researchers have developed an innovative way to predict new uses for existing medicines. Using computers and genomic information, scientists at Stanford University in Palo Alto, California, have established a method to identify FDA-approved drugs that may work against diseases they weren’t originally designed to combat. New research published in two articles in the August 17th online issue of Science Translational Medicine highlights two such repurposed drugs that may be used to treat inflammatory bowel disease and lung cancer [1-2].

A team led by Atul J. Butte, M.D., Ph.D. at Stanford University used data from the National Institutes of Health National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO), a publicly available database that contains the results of thousands of genomic studies submitted by researchers around the world on a wide range of topics. The GEO database catalogs changes in gene expression under various conditions, such as in diseased tissues or in response to medications.

Butte’s group focused on 100 diseases and 164 drugs. They created a computer algorithm that searched for and matched studies where a drug created a change in gene expression that was opposite to the gene expression caused by a disease. Many of the drug-disease matches were known and are already in clinical use, supporting the validity of the approach. For example, the algorithm correctly predicted that prednisolone could treat Crohn’s disease, a condition for which it is a standard therapy.

Other matches were surprising. In particular, the algorithm matched an anti-ulcer drug (cimetidine) with lung cancer, and an anticonvulsant drug used in epilepsy (topiramate) with inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis.

The researchers then tested the two drugs — both generics — in animal models. Cimetidine slowed the growth of cancer cells in a mouse model of lung cancer compared to mice that did not receive the drug. Topiramate decreased the symptoms of bowel disease — diarrhea, inflammation, ulcers and microscopic damage in the colon — in rats, sometimes even better than prednisolone.

Further studies are needed to validate the clinical potential of cimetidine as a therapy for lung cancer and topiramate as a therapy for inflammatory bowel disease. Nevertheless, the studies provide proof-of-principle that the matching of drug-disease gene expression profiles are useful to repurpose drugs.

Yves A. Lussier, M.D., an Associate Professor of medicine and engineering at the University of Illinois at Chicago who co-authored a commentary on the research in Science Translational Medicine, wrote [3]:

This emergent genome-wide property of directionality [between genome-wide mRNA expression and a clinical phenotype] may ultimately translate into medical practice as a clinical finding analogous to an arrhythmia seen on electrocardiogram. Arguably, physicians could incorporate these clinicogenomic findings in their practice to improve the process of treatment decision-making.

Pharmaceutical companies have increasingly turned to drug repurposing as a means of drug discovery. A significant advantage of drug repurposing is that the repurposed drug has already passed a significant number of toxicity tests and has an established safety profile, so it can move through development at an accelerated pace.

Butte is also co-founder of NuMedii, an early stage therapeutics company focused on finding new clinical applications for existing drugs; he is also chairman of the company’s scientific advisory board. The two published studies should serve to validate the company’s computational method and will likely attract pharmaceutical companies that are eager to find new uses for drugs in their pipeline.

References

1. Sirota et al. Discovery and Preclinical Validation of Drug Indications Using Compendia of Public Gene Expression Data. Sci Transl Med. 2011 Aug 17.
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2. Dudley et al. Computational Repositioning of the Anticonvulsant Topiramate for Inflammatory Bowel Disease. Sci Transl Med. 2011 Aug 17.
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3. Lussier and Chen. The Emergence of Genome-Based Drug Repositioning. Sci Transl Med. 2011 Aug 17.
   View abstract