The FDA has issued a guidance on exploratory investigational new drug (IND) applications.  Such studies are defined as no more than a week long, “The Agency believes that sponsors have not taken full advantage of that flexibility and often provide more supporting information in INDs than is required by regulations.” One key idea in the document is a formal ratification of “microdose” studies in which subtherapeutic levels of the drug are given to a small number of patients. As it has for about a year, the FDA said more limited animal testing than the industry presently conducts may be sufficient to start “exploratory IND” trials.  The document can be found at:
http://www.fda.gov/cder/guidance/7086fnl.htm