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Innovative Repurposing: New Drugs From Old

Posted on May 26th, 2016 by in Chemistry

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Re-purposing of drugs is fraught with challenges, but can they be overcome so that patients benefit? The term re-purposing is often associated with the idea of saving a few bucks by taking something old and turning it into something useful (like transforming an empty wine bottle into a bird feeder). In the pharmaceutical world, though, re-purposing is a serious business that can create significant value by taking a drug already on the market and developing it for an entirely unrelated indication.  Sometimes, the definition of re-purposing expands further to include drugs that were extensively researched for a particular indication, dropped from development for that indication, and then subsequently resurrected for a different use in the wake of new findings.

The classic example of a wildly successful re-purposing is the development of Sildenafil (Viagra®), which was initially researched for cardiovascular indications, but, when heathy volunteers started reporting penile erections during early trials, it was dropped for cardiovascular use and redirected to help millions of men with erectile dysfunction (1). This type of development is usually referred to as re-positioning.

Re-purposing can address pressing patient needs, often in some of the most difficult to treat areas of medicine. Thalidomide is a good example of a drug that was unsuccessful in its first incarnation as a sedative but was subsequently successful as a treatment for multiple myeloma (1). Successes in re-purposing rely heavily on a strong understanding and knowledge of the pre-clinical drug attributes where innovative thinking is key. Many seemingly unrelated medical problems have common disease pathways, and successes may come from a clear understanding of those pathways combined with in-depth knowledge of a drug’s mode of action.

Re-purposing is frequently less risky when compared to the development of a new molecular entity for the first time. The pharmacology and mode of action of these drugs is generally already clearly understood and well documented, so those costs don’t have to be repeated. Likewise, the majority of the necessary pre-clinical studies have most likely been completed, so that is yet another step saved by re-purposing.

Despite those advantages, there are some significant challenges to the process, and they fall broadly into three categories (2):

  1. Clinical trials that are high cost and high risk. The difficulties of trials in the area of neurodegeneration illustrate the issues encountered in the conduct of trials for many re-purposed drugs. The indications for these medicines are often in diseases where treatment periods are very long due to the chronic nature of the illnesses, and patients may be scarce. This problem can be found in areas such as rare diseases and oncology, as well as neurodegeneration, all of which are potentially fruitful areas for re-purposing. The additional work needed to establish the safety of the product in the elderly, or other special patient populations with comorbidities, also cannot be under-estimated. Oncology has often been a focus for re-purposing, as there may be a higher tolerance for toxicities.
  2. Issues with patent protection. Development of an initial indication may take an average of 14 years, so there may not be much of the 20-year patent protected period left once the re-purposed development period has begun. “Use” patents for the new indications might help, but they are often difficult to defend and have to meet non-obvious criteria. This means that there may only be a very small window of opportunity for the developer to re-coup development costs, let alone make a return on the investment, before generic drugs come onto the market.
  3. Price and commercialization issues. In many markets, the initial indication sets the price for the drug and it is difficult, if not impossible, to increase that price at a later date for different indications. Reimbursement will probably require additional economic data to support the new indication, the same as for a new molecular entity. In short, there may be costs associated with commercialization which cannot be recouped in the price of the product.

Bolstered by successes like those mentioned above, and by the financial implications of not having to reinvent the wheel, interest in re-purposing continues to grow, leading to more discussion and, hopefully, greater investment. This is already exemplified by organizations such as that of the National Institute for Advancing Translational Sciences (https://ncats.nih.gov). Furthermore, conferences that did not even exist a few years ago, such as The 5th Annual Drug Repositioning and Discovery Conference (www.drugrepositioningconference.com), now focus purely on the topic.

Ideally, re-purposing should form an important part of a company’s R&D strategy, as it may be a good way of addressing significant unmet medical need while lowering the risk of drug development. However, this approach clearly must be balanced against patent and commercial considerations. Until legal protection and reimbursement issues, in the face of generics, can be addressed, there may still be reluctance to invest heavily in this area of drug development.

References

  1. Shim JS, Liu JO. Recent Advances in Drug Repositioning for the Discovery of New Anticancer Drugs. Int J Biol Sci 2014; 10(7):654-663. Doi:10.715-/ijbs.9224. Available from http://www.ijbs.com/v10p0654.htm
  2. Shineman DW, Alam J, Anderson M, et al. Overcoming obstacles to repurposing for neurodegenerative disease. Annals of Clinical and Translational Neurology. 2014; 1(7):512-518.

 

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