4.5.1 summarizes which concept?

• A. The protocol may be signed by sponsor only.
• B. Only sponsor signs; investigator has no obligation.
• C. The investigator must conduct the trial in compliance with the protocol, and both the investigator and sponsor should sign the protocol or an alternative contract.
• D. IRB approval overrides the protocol.

Answer: (C)

The key idea here is that a clinical trial is governed by a written protocol, and both parties—the investigator and the sponsor—must commit to that plan in a binding way. The investigator is responsible for conducting the study in strict accordance with the protocol to protect participant safety and ensure reliable data. At the same time, the sponsor shares responsibility for supporting and monitoring the trial and for ensuring that obligations are clear and enforceable. Signing the protocol (or an equivalent contract) formalizes this mutual commitment and creates a binding agreement about roles, responsibilities, and expectations.

IRB approval plays a critical ethics role, but it does not override what’s written in the protocol or substitute for the formal agreement between sponsor and investigator. Any changes to the protocol typically require a formal amendment and proper signatures, reinforcing that both parties remain aligned throughout the study.