There are two routes from discovery to licensing, depending on whether the drug is a completely new one (de novo pathway) or whether it is an existing drug discovered to be an effective treatment of a different symptom or condition (repositioning pathway).
For de novo drug discoveries, it can take 10-17 years for the drug to be licensed for use for a specific indication by the Medicines & Healthcare products Regulatory Agency (MHRA) and reach patients.
Repositioning or the discovery of a new indication for an existing drug is quicker, only taking 3-12 years, as it skips the need for formulation design and several safety steps in the de novo pathway above because the pharmaceutical product already exists. As an example, if rituximab were to become licensed for the new indication of M.E., it would go through the repositioning pathway because it has already undergone development as a de novo drug and is indicated for rheumatoid arthritis and some forms of cancer.
For a diagram of the stages involved in both de novo and repositioning, see this diagram in a Nature article. I’ll write a blog post on what all these stages mean shortly.
Patents on new branded drugs last 10 years, during which the company recoups their research and development costs. Repositioning can be a way of a drug company recouping more of its costs if the drug still has patent protection. Patent expiry can be a factor preventing the licensing of a drug for a new indication because the drug becomes generic, meaning it can be manufactured by any company with a license to so it becomes cheaper and therefore less profitable for the original company.
This can mean that there is little financial incentive for drug companies to find new indications for existing drugs as they won’t recoup the costs involved in the repositioning pathway. This is one of the issues which will hopefully be addressed in the Accelerated Access Review, which I’ve written about in another post. One way drug companies extend the patent is to develop new formulations for the same drug, such as a modified release or oro-dispersible forms, or intravenous drug reformulated for sub-cutaneous administration, which has been the case for Rituximab.
1 Ashburn T, Thor K. Drug repositioning: identifying and developing new uses for existing drugs. Nat Rev Drug Discov 2004;3:673-683. doi:10.1038/nrd1468 http://www.nature.com/nrd/journal/v3/n8/fig_tab/nrd1468_F2.html (accessed 15 July 2015)
2 Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press https://www.medicinescomplete.com/mc/bnf/current/PHP6651-rituximab.htm (accessed 15 July 2015)
3 Guha M. Pharmaceutical Journal. Repositioning existing drugs for cancer treatment. 2015. http://www.pharmaceutical-journal.com/news-and-analysis/features/repositioning-existing-drugs-for-cancer-treatment/20068778.article (accessed 15 Jul 2015)
4 Roche. Roche’s new time-saving subcutaneous formulation of MabThera approved in Europe for the treatment of common forms of non-Hodgkin Lymphoma. 2015. http://www.roche.com/media/store/releases/med-cor-2014-03-28.htm (accessed 15 Jul 2015).