This promise matters because the entire architecture of clinical research depends upon it. Participants enroll based on what the protocol says will happen to them. Regulators approve trials based on what the protocol specifies. Sponsors plan their development programs based on the data the protocol is designed to generate. When investigators deviate from the protocol without justification, they undermine the foundation upon which everyone else has relied.

And yet, rigid adherence is not always possible. Medicine is practiced in the real world, where unexpected situations arise. A participant experiences an unanticipated reaction that requires immediate intervention not specified in the protocol. Equipment fails. Supplies run out. Sometimes, circumstances demand action that the protocol did not anticipate.

ICH E6(R3) addresses both dimensions of this reality. Section 2.5 establishes the investigator's compliance obligations while recognizing the narrow exception for immediate hazards. Section 2.6 addresses what happens when a trial ends prematurely, whether terminated by the sponsor, suspended by the investigator, or concluded for other reasons. Together, these sections define what it means to keep the promise embedded in that signature, and how to proceed when keeping that promise becomes impossible.

This promise matters because the entire architecture of clinical research depends upon it. Participants enroll based on what the protocol says will happen to them. Regulators approve trials based on what the protocol specifies. Sponsors plan their development programs based on the data the protocol is designed to generate. When investigators deviate from the protocol without justification, they undermine the foundation upon which everyone else has relied.

And yet, rigid adherence is not always possible. Medicine is practiced in the real world, where unexpected situations arise. A participant experiences an unanticipated reaction that requires immediate intervention not specified in the protocol. Equipment fails. Supplies run out. Sometimes, circumstances demand action that the protocol did not anticipate.

ICH E6(R3) addresses both dimensions of this reality. Section 2.5 establishes the investigator's compliance obligations while recognizing the narrow exception for immediate hazards. Section 2.6 addresses what happens when a trial ends prematurely, whether terminated by the sponsor, suspended by the investigator, or concluded for other reasons. Together, these sections define what it means to keep the promise embedded in that signature, and how to proceed when keeping that promise becomes impossible.