Innovative early development regulatory approaches: expIND, expCTA, microdosing.

The Food and Drug Administration (FDA) Critical Path Initiative as well as the European Medicines Agency Road Map to 2010 (ref. 2) call for opportunities for more efficient drug development. One of the initiatives that has emerged in this context is the elaboration through guidance of exploratory investigational new drugs (INDs)/clinical trial applications (CTAs). This article reviews the history of these emerging guidances as well as the experience to date in their use by the industry.