Retrospective clinical analysis for drug rescue: for new indications or stratified patient groups.

The increasing realization that many existing drugs do indeed provide opportunities for additional therapeutic indications suggests we should not only be alert for this potential among marketed drugs but also within the pool of developmental drugs, of which (owing to attrition) there are many more examples in existence. We present examples of drug repurposing by retrospective clinical trial analysis and suggest that this strategy presents a promising way of rescuing failed developmental candidates. We contend that the commercial barriers to successful drug rescue are less problematic than for drug repurposing. We indicate practical means for mining data from past clinical trials, either for new indications or for specific patient groups.