Repurposed drugs: second time lucky

The drug discovery and development path for a new chemical entity (NCE) can take ten to 15 years and cost between $1 billion and $2 billion. ‘Repurposing’ is the practice of finding novel therapeutic indications for existing drugs. Typically the selected drug will have already been shown to be safe in patients, thereby significantly reducing the time it takes to bring the drug to market.

Indeed, it has been reported that repurposed agents are more than twice as likely across all disease indications to make it to market compared to NCEs. Furthermore, price support for a repurposed drug is in principle no different from that for an NCE, being likewise dependent on its substitutability and its clinical and economic advantages.

Policy makers, being aware of these benefits, have made efforts to encourage repurposing—for example the US National Institutes of Health has programmes aimed at utilising existing, partially developed therapeutic candidates in new disease indications. In the UK an ‘off-patent’ drugs bill was recently proposed, with one of its aims being to give generic drug makers new marketable indications for their products.

However, even if the repurposed drug in question is off-patent, bringing it to market is still a considerable challenge, and such an investment requires a clear exclusivity strategy. Unfortunately, clarity is something that is lacking when considering obtaining and enforcing patents in this field.

Patents—history and formats

In order to protect repurposed innovations, ‘second medical use’ patents are available in most territories, although notable exceptions exist including in India. The precise wording of such claims is a matter of national laws, but a bewildering array of formats is used. For example, in Europe two claim formats have been permissible: