Safety Review

Following review of an initial IND submission, CDER has 30 calendar days in which to decide if a clinical hold is necessary (i.e., if patients would be at an unacceptable risk or if CDER doesn't have the data to make such a determination). Generally, drug review divisions do not contact the sponsor if no concerns arise with drug safety and the proposed clinical trials. If the sponsor hears nothing from CDER, then on day 31 after submission of the IND, the study may proceed as submitted.

Source: U.S. Food and Drug Administration Center for Drug Evaluation and Research Handbook.