Exploratory IND: a new regulatory strategy for early clinical drug development in the United States.

Optimizing exploratory drug development by means of doing first-in-human studies earlier is an attractive option for pharmaceutical sponsors to select more successful drug candidates. Traditional registration-driven clinical phase 1 programs could be preceded by early human screening studies with subpharmacological single doses (microdoses) or with low pharmacologically active doses of one or several lead candidates, whereby human pharmacokinetic and pharmacodynamic data are generated very early. Such low doses are not expected to have clinically significant toxic potential, so early human screening studies may be supported by abbreviated nonclinical safety packages. Recent U.S. FDA draft guidance (April 2005) regulated early human screening studies conducted under the exploratory IND. The author outlines the features of the study design, dose selection, and nonclinical safety packages required in support of exploratory IND studies in humans. In appropriately chosen cases, exploratory IND could allow for patients' quicker access to safer and more efficacious doses of novel drugs, reduce attrition in clinical trials, and facilitate more economical drug development.