You are right to urge the US government and others to encourage the re-use of old medicines by granting exclusivity rights (Editorial, Nature 465, 267; 2010). But it is not correct to say that the European Union (EU) already rewards innovators in this area with a further year of patent protection.

The EU awards an extra year's exclusivity for the technical data that are used to obtain the marketing authorization for the product, as long as the indications constitute a “significant clinical benefit”. Because data exclusivity usually expires before patent protection, this provision is of limited value.

One solution would be for regulators to extend patent life when existing medicines have been repurposed for new uses — but this would only assist projects undertaken by the original patentee.

Another would be to exclude generic products from the market for a limited period should a third party, or the patentee, repurpose a medicine. The repurposed use could be assessed according to similar criteria and judged against new indications of significant clinical benefit (where these do not amount to repurposing). However, this would still not protect companies in situations in which generic products are already on the market.

Also, holders of repurpose patents could be allowed to enforce the patent when generic off-label use is damaging their monopoly.