Drug repurposing, also called drug repositioning, is the process of screening existing libraries of drugs already approved by the FDA in an effort to identify compounds that are effective in other diseases.
According to F. Bertolini et al., in a report on oncology drug sales and expenditure, the year 2013 saw $43 billion in sales from the 10-big oncology drug makers and $91 billion spent on drug development.
A concerted effort by pharmaceutical companies and academic core facilities has led to quite a few successfully repurposed drugs (Table 1).
Advantages of repurposing existing drugs include the:
- Considerably reduced time for research and development and for FDA approval
- Availability of safety and toxicity profiles that have been tested for decades
- Unmatched fiscal considerations in off-patent drugs
A summary is provided in Table 2.
A twist on drug repurposing and outcomes is the story of rare disorders and associated orphan drugs. Rare disorders are illnesses of low prevalence with very small populations of patients. Drugs for rare disease treatment are termed as "orphan drugs." To provide incentives to the pharmaceutical industry to produce orphan drugs, the United States Congress passed Orphan Drug Act in the U.S. in 1983. Despite low demand, orphan drugs can yield high profits with hefty prices. These, along with the subsidies, tax credits, and waivers, have turned certain orphan drugs into blockbuster drugs. For example, Pulmozyme is an orphan drug used for cystic fibrosis treatment that has increased life expectancy for individuals with cystic fibrosis from their teens to their forties, even fifties.