Who has ultimate responsibility for an investigational product at the study site?

Explanation:

The person responsible for making the initial risk determination for a device being used in a study is the sponsor-investigator. The sponsor-investigator is an individual that initiate and conduct investigation. The sponsor investigator also takes up the responsibility as the study's sponsor

An investigational product may be an unlicensed product or a licensed product when used or assembled (formulated or packaged) differently from the approved form, when used for an unapproved indication, or when used to gain further information about an approved use.