The Investigator’s Brochure (IB) is a comprehensive compilation of clinical and nonclinical data on the investigational product (drug, supplement, device or other product) maintained by a drug developer or investigator that contains the body of information about the investigational product obtained before and during a drug trial. The IB is a document of critical importance throughout the drug development process and is updated with new information as it becomes available.

The purpose of the IB is to compile data relevant to studies of the investigational product in human subjects gathered during preclinical and other clinical trials to provide the investigator with information necessary for the management of study conduct and study subjects throughout a clinical trial.

An IB facilitates understanding of the rationale for, and their compliance with, many key features of the protocol, such as:

• Dose (of the study drug)
• Dose frequency and dosing interval
• Methods of administration
• Safety monitoring procedures

Information in the IB should be presented in a concise, simple, objective, balanced, and non-promotional form that enables a clinician, or potential investigator, to understand it and make his/her own unbiased risk-benefit assessment of the appropriateness of the proposed trial. When the investigational product is marketed and its pharmacology is widely understood by medical practitioners, an extensive IB may not be necessary. In these cases, a basic product information brochure, package leaflet or an expanded background information section in the trial protocol may be permitted by regulatory authorities as an alternative, provided that it includes current, comprehensive, and detailed information on all aspects of the investigational product that might be of importance to the investigator. The IB should be reviewed at least annually and revised as necessary in compliance with a sponsor’s written procedures. When new information relevant to the clinical trial becomes available, it should be communicated to the investigators, and possibly to the Institutional Review Boards (IRBs) prior to a scheduled revision of the IB. Generally, the sponsor is responsible for ensuring that an up-to-date IB is made available to the investigator(s) and the investigators are responsible for providing the up-to-date IB to the responsible IRBs/IECs.

An IB contains a “Summary of Data and Guidance for the Investigator” section, of which the overall aim is to “provide the investigator with a clear understanding of the possible risks and adverse reactions, and of the specific tests, observations, and precautions that may be needed for a clinical trial. This understanding should be based on the available physical, chemical, pharmaceutical, pharmacological, toxicological, and clinical information on the investigational product(s). Guidance should also be provided to the clinical investigator on the recognition and treatment of possible overdose and adverse drug reactions that is based on previous human experience and on the pharmacology of the investigational product”.[1] 
The sponsor is responsible for keeping the information in the IB up-to-date. The IB should be reviewed annually and must be updated when any new and important information becomes available, such as when a drug has received marketing approval and can be prescribed for use commercially.

Owing to the importance of the IB in maintaining the safety of human subjects in clinical trials, and as part of their guidance on Good Clinical Practice (GCP), the U.S. Food and Drug Administration (FDA) has written regulatory codes and guidances for authoring the IB, and the International Conference on Harmonisation (ICH) has prepared a detailed guidance for the authoring of the IB in the European Union (EU), Japan, and the United States (US).[2]