Good Clinical Practice (GCP)

Good Clinical Practice (GCP) is an international ethical and scientific quality standard for the design, conduct, recording, and reporting of clinical trials that involve human participants. Developed through the International Council for Harmonisation (ICH) as the ICH E6 guideline, GCP is designed to protect the rights, safety, and well being of trial participants and to make clinical trial data credible and accurate. The current version, ICH E6(R3), was adopted by ICH on 6 January 2025 and replaces E6(R2) of 2016; it speaks of trial "participants" where earlier versions said "subjects", and it asks for a proportionate, risk based approach to trial quality.

GCP provides the foundation for the ethical conduct of clinical trials worldwide. Regulatory agencies including the FDA, the EMA and Japan's PMDA expect the trials that support drug approval applications to follow GCP, and they inspect investigators and sponsors for compliance; for clinical investigations of medical devices, the corresponding GCP standard is ISO 14155 rather than ICH E6. Without GCP, there would be no consistent standard for protecting participants, ensuring data integrity, or verifying that trial results are reliable. GCP compliance is also essential for the international acceptance of trial results; a trial conducted under GCP in one country can support regulatory submissions in others, facilitating global drug development. For individual researchers, GCP training is typically mandatory before participating in clinical trials, and non compliance can result in regulatory action, retraction of publications, and disqualification from future research.

ICH E6(R3) is organized as 11 overarching principles, supported by Annex 1, which sets out the responsibilities of the IRB or ethics committee, the investigator and the sponsor and the rules for data governance, and Annex 2 (adopted by ICH in June 2026), which adds considerations for trials with decentralized elements, pragmatic elements or real world data. The rights, safety, and well being of trial participants are the most important considerations and should prevail over the interests of science and society. Trials should be scientifically sound and described in a clear, concise and operationally feasible protocol. The trial should be conducted in compliance with the protocol that has received prior institutional review board (IRB) or ethics committee approval. Freely given informed consent should be obtained and documented from every participant (or, for a person unable to consent, from a legally acceptable representative) before trial participation; in emergency situations where that is not possible, consent is sought as soon as possible under applicable regulatory requirements and processes approved by the IRB or ethics committee. Quality should be built into the design of the trial, and trial processes should be proportionate to the risks to participants and to the importance of the data collected.

The GCP framework assigns responsibilities to multiple parties. The sponsor (the individual, company, institution or organization that takes responsibility for initiating and managing the trial and arranging its financing) is responsible for the design, management, and financing of the trial and for ensuring GCP compliance through quality management, monitoring and auditing. The investigator (the person responsible for the conduct of the trial at a trial site, usually a physician) is responsible for the conduct of the trial at that site, including obtaining informed consent, following the protocol, and ensuring accurate data recording. The IRB or ethics committee reviews and approves the protocol before the trial starts and conducts continuing review of the ongoing trial to protect participants. The sponsor may transfer tasks, and the investigator may delegate them, for example to a contract research organization or to site staff, but each keeps overall responsibility for them.

GCP requires detailed documentation of all aspects of the trial. Source records (original documents or data, in any format, such as medical records, participant entered data and data from wearables) must be maintained. Case report forms must accurately reflect the source data. An audit trail must allow reconstruction of the trial's conduct. Essential records (called essential documents in E6(R2)) are the documents and data that allow the conduct of the trial and the reliability of its results to be evaluated; the sponsor keeps them in the trial master file and the investigator in the investigator site file.

Quality assurance and quality control are embedded throughout. Under E6(R3), the sponsor takes a proportionate, risk based approach to quality management: it identifies the factors critical to quality (the data and processes that matter most for protecting participants and for reliable results), assesses the risks to them before and during the trial, and sets the extent and nature of monitoring, which can combine on site, remote and centralized monitoring, according to those risks. Independent audits may also be conducted. Data management procedures must ensure the integrity, accuracy, and completeness of the data.

GCP compliance is expected for clinical trials of investigational products whose data will support regulatory submissions to health authorities. In the EU, the Clinical Trials Regulation (EU) No 536/2014 requires the sponsor and the investigator to conduct each clinical trial of a medicinal product in accordance with the protocol and the principles of GCP, whatever its purpose, and the EMA applied E6(R3) from 23 July 2025. In the US, trials under an investigational new drug application (IND) must meet FDA's regulations on informed consent, IRBs and investigational drugs (21 CFR parts 50, 56 and 312); FDA published E6(R3) as final, nonbinding guidance in September 2025, and it accepts a foreign study not conducted under an IND as support for an application if the study followed GCP, including review by an independent ethics committee and informed consent (21 CFR 312.120). E6(R3) itself applies to interventional trials of investigational products intended for submission to regulators, and notes that its principles may also apply to other interventional trials, such as investigator initiated trials, in accordance with local requirements. E6(R3) expects everyone involved in a trial to be qualified by education, training and experience for their tasks, and many sponsors, institutions and funders require documented GCP training; for example, the US National Institutes of Health (NIH) expects investigators and staff on the clinical trials it funds to complete GCP training and refresh it at least every three years. GCP principles should be followed from the earliest stages of trial design through publication and archiving.

A common error is treating GCP as a bureaucratic checklist rather than a quality framework. GCP requirements exist to protect participants and ensure data integrity, and compliance should be approached with this purpose in mind. Another mistake is inadequate training: trial staff who have not received GCP training or whose training is outdated may inadvertently violate requirements. Protocol deviations (departures from the approved protocol) that are not properly documented and reported are a frequent finding in regulatory inspections. Consent process deficiencies, including failing to provide adequate information, not telling participants in a timely way about new information that may affect their willingness to continue (such as an emerging safety concern), not re-consenting them when that is needed, or coercing participation, are among the most serious GCP violations. The opposite error is applying the same intense checks to every data point and process, such as verifying all data against source records at every site, instead of focusing monitoring on the factors critical to quality, as the risk based approach of E6(R3) asks. Finally, poor documentation (incomplete source records, unsigned case report forms, missing essential records) undermines the ability to verify trial conduct and data integrity.

A pharmaceutical company sponsors a multinational Phase III trial of a new anticoagulant across 80 sites in 15 countries. GCP compliance measures include: GCP training certificates for all 400 trial staff, IRB or ethics committee approval covering each site before enrollment begins, an independent Data Safety Monitoring Board, a risk assessment that names the factors critical to quality (such as the primary endpoint and the recording of major bleeding events), on site and remote monitoring visits scheduled according to each site's risks, a centralized statistical monitoring program to detect data anomalies, and a secure electronic data capture system with a complete audit trail. During a regulatory inspection of 4 sites, the health authority identifies 3 minor protocol deviations (relating to visit window timing) and no critical findings, and the trial data are accepted for the regulatory submission.