The term co-investigator is not defined in FDA regulations. As commonly used, the term is meant to indicate that each co-investigator is fully responsible for fulfilling all of the obligations of an investigator as identified in 21 CFR 312.60. Thus under 21 CFR 312.3(b), each co-investigator is an investigator, and as such must sign a separate 1572. In some situations, it is preferable to have more than one investigator responsible for a clinical investigation. For example, when a study is conducted at multiple research facilities that are not in close proximity, FDA expects an investigator who has signed a 1572 to be available at each location to either personally conduct or supervise the study. This responsibility cannot be delegated to a subinvestigator. Although not necessary, it is acceptable to have more than one investigator at a single site. For example, the conduct and supervision of a large investigation with many subjects or complicated procedures might be shared among several investigators, each of whom has signed a 1572 when the investigation is conducted under an IND. This is distinct from a subinvestigator (see #31) whose role in the clinical investigation is more limited.
