Good Clinical Practice (GCP)

Key facts

Main international guideline

ICH E6, from the International Council for Harmonisation

Current revision

E6(R3), adopted by ICH in January 2025

U.S. status of ICH E6

Published by FDA as guidance, not binding regulation

Binding U.S. rules

21 CFR Parts 50, 54, 56, 312 and 812, among others

U.S. enforcement

FDA Bioresearch Monitoring (BIMO) inspections

What is Good Clinical Practice?

GCP is the shared rulebook for how trials should be run. Its core idea is that the rights, safety and well-being of participants come first, and that the data a trial produces must be credible enough for regulators to rely on.

The best known GCP standard is ICH E6, developed by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH). The original guideline was finalized in 1996, an addendum known as E6(R2) followed in 2016, and ICH adopted a substantially revised E6(R3) in January 2025 that emphasizes risk-based quality management and fit-for-purpose approaches.

How GCP applies in the United States

In the United States, GCP combines guidance and regulation. FDA publishes ICH E6 as guidance, which reflects its current thinking but is not binding on its own. The legally enforceable requirements sit in FDA regulations, including:

• 21 CFR Part 50: protection of human subjects and informed consent.
• 21 CFR Part 54: financial disclosure by clinical investigators.
• 21 CFR Part 56: Institutional Review Boards (IRBs).
• 21 CFR Part 312: investigational new drug applications, including sponsor and investigator duties.
• 21 CFR Part 812: investigational device exemptions.

Core GCP principles

Across its versions, GCP rests on principles such as:

• Trials are ethically justified and reviewed by an IRB or independent ethics committee.
• Freely given informed consent is obtained from every participant.
• Protocols are scientifically sound, and trials are run by qualified people.
• Quality is built into trial design, with oversight focused on the risks that matter most.
• Records are accurate and retained so that results can be verified.

Why GCP matters

Data from a trial that did not follow GCP can be rejected by regulators even when the results look positive. FDA inspects clinical investigators, sponsors, contract research organizations and IRBs through its Bioresearch Monitoring (BIMO) program, and serious findings can lead to warning letters, investigator disqualification or exclusion of data from an application.

For sponsors choosing sites and vendors, GCP training records and inspection histories are standard diligence items, and GCP compliance is the baseline for any trial meant to support approval in ICH member regions.