Before testing a new drug on human subjects, the company must file an IND. Prior to filing an IND, the sponsor develops information on the chemistry of the drug so that it can be produced in batches of known strength and purity. In addition, the sponsor must conduct a number of animal studies to produce information on the pharmacology and toxicology of the drug. Information, for example, must be produced on the absorption, distribution, metabolism, and excretion properties of the drug. Finally, detailed protocols for testing on human subjects must be submitted. In addition, since 1971, the FDA has required that all proposed clinical studies be reviewed by an institutional review board. Technically, unless otherwise notified, the sponsor can begin clinical studies within thirty days (if the IRB approves). The FDA can, however, terminate an IND at any time; thus in practice the FDA must approve the IND proposal. The IND stage of drug approval is broken into three phases. The FDA exerts considerable control over all phases of the clinical trial process, and at any stage the FDA can and often does request additional clinical trials and changes in trial protocols.