Who is primarily responsible for initiating and conducting a clinical trial?

The correct answer is the sponsor-investigator because this individual holds dual responsibilities, combining both the role of the sponsor and the principal investigator in a clinical trial. The sponsor-investigator designs the trial, oversees its implementation, ensures compliance with regulatory requirements, and takes on the responsibility of coordinating the necessary resources for the study. This role is crucial because it integrates both scientific oversight and logistical management, providing a single point of accountability for the trial's integrity and conduct.

In contrast, while the principal investigator plays a vital role in conducting the trial at a specific site, they may not have the same level of responsibility for initiation, particularly in multicenter trials. The clinical trial coordinator assists with the trial’s logistics and may facilitate activities related to the conduct of the trial, but they do not hold the primary responsibility for initiating a trial. The institutional review board (IRB) is responsible for reviewing the ethics of a study and ensuring the protection of participants, but they do not initiate or conduct clinical trials themselves. Thus, the sponsor-investigator is uniquely positioned to take on the primary responsibilities for both the initiation and conduct of the clinical trial.