The Investigator’s Brochure: Multifaceted and Multidisciplinary

Many documents are essential to biotechs and start‑ups, but two decades of experience at Niche suggests that none are more critical than the Investigator’s Brochure (IB), which summarises all research completed on an investigational medicinal product (IMP) [1]. It fulfils multiple purposes across clinical development and is typically created by a multidisciplinary team [2].

The content of an IB is well defined. The ICH E6 guideline describes in detail how it should include non‑clinical and clinical data on the IMP, along with specific guidance to investigators on its use [1]. Beyond serving as the primary reference when investigators determine whether an adverse event is ‘unexpected,’ the IB also plays several regulatory roles, including:

• A prerequisite for clinical studies under ICH E6 Good Clinical Practice [1].
• A key data source for independent ethics committees [3].
• A required component of Investigational New Drug Applications in the United States [4].
• A partner document to the Investigational Medicinal Product Dossier (IMPD) and Paediatric Investigation Plan in Europe [5].

At Niche, we have encountered a wide range of IB‑related challenges over the years. Experience shows that sharing practical ‘how‑to’ guidance and highlighting common pitfalls is often more valuable than simply providing templates. This is why our IB template and Insider’s Insight guide remain among the most downloaded resources from our Niche Science & Technology Resource Centre.

Below are six case‑oriented learnings drawn from our experience.

1. The Biotech’s Investigator’s Brochure

Developing the first version of an IB should be straightforward if all relevant data sources are available. The document should be concise, typically 80–100 pages, clear, focused, balanced, and sufficiently comprehensive to inform investigators about the IMP [6].

The writing style should be simple, objective, and non‑promotional, enabling clinicians to easily access information, especially safety data, and make an unbiased risk–benefit assessment [7]. Investigators may be reviewing the IB under stressful conditions, making clarity essential.

Biotechs and start‑ups often treat the IB as a surrogate marketing document for their new IMP. Even experienced pharmaceutical executives succumbs to the temptation (from time to time) to make their Investigator’s Brochure the repository of all human knowledge about their drug. Authors frequently need to push back against contributors who struggle to reduce or remove redundant information. It is almost always possible to shorten content while retaining key messages [8].

2. The Investigational Medicinal Product Dossier Conundrum

Like the IB, the Investigational Medicinal Product Dossier (IMPD) is a central component of the documentation required for competent authority approval to conduct clinical trials in the EU [5]. The IB and IMPD often contain overlapping data. EMA guidance allows sponsors to minimise non‑clinical pharmacology and toxicology content in the IMPD by cross‑referencing the IB [5,9].

This approach can save time and resources. However, teams must proceed carefully. To keep the IB concise, authors often omit details such as OECD Good Laboratory Practice (GLP) compliance statements or justifications for non‑compliance, as well as analytical method descriptions, information typically included in IMPDs [10]. Failure to provide such supporting information anywhere in the Clinical Trial Application (CTA) is a common reason for regulatory rejection, according to the UK MHRA [11].

3. The Project Management Investigator’s Brochure

Depending on sponsor needs and resources, IB development may require the author to coordinate diverse contributors, define the scope of their input, manage quality, and ensure consistent use of templates and style. This role often extends beyond writing to include project management, editing, and diplomacy [12].

Non‑clinical and CMC contributors may require additional guidance, as they are often less familiar with clinical documentation standards and timelines. Although specialist team members may draft specific sections, the Introduction typically falls to the lead writer. Because the scientific rationale for the IMP may be abstract or evolving, authors often find this section challenging. Useful source materials include the clinical development plan, internal presentations, and briefing packages prepared for funding discussions.

4. The Evolving Investigator’s Brochure

ICH E6 requires that the IB be reviewed at least annually and revised as necessary, with more frequent updates when new information emerges that may influence the IMP’s risk–benefit profile [1]. ‘Relevant new information’ refers to data that materially changes understanding of the IMP, particularly regarding safety.

Each update should involve reviewing the entire IB, not only to add new information but also to remove or condense outdated content. Each version should include a documented summary of changes [1].

The previous edition usually serves as the template for the next. Over time, the proportion of clinical information increases, starting with pharmacokinetics and pharmacodynamics, then progressing to safety and efficacy data from healthy volunteers and patient populations [13]. As clinical data accumulate, non‑clinical detail can often be reduced. Teams may resist removing earlier content, and refresher training is often helpful.

5. One Document, Multiple Indications

When an IMP is being developed for multiple indications, sponsors must decide whether to prepare separate IBs or a single document covering all indications. ICH E6 provides no specific guidance, so decisions are often subjective [1].

Factors influencing this choice include:

• The relatedness of the indications
• Differences in formulation or route of administration
• Development timelines
• Whether different sponsors are involved
• Available resources

If multiple IBs are produced, teams must determine how much safety information from other indications should be included, based on clinical relevance. In many cases, more comprehensive cross‑indication safety data are beneficial – more is more [14].

Combination products introduce additional complexity and may require tailored approaches.

6. The Mature Investigator’s Brochure

As clinical programmes progress, the volume of data increases, and the IB must be restructured to remain approximately 100 pages. ICH E6 specifies that summaries of completed clinical trials should be included ‘where possible’ [1]. However, adding new summaries with each update can exceed page limits, making data synthesis necessary.

Pharmacokinetic data can often be summarised across studies, including absorption, protein binding, metabolism, distribution, and elimination. Subgroup analyses (e.g., sex, age, hepatic or renal impairment) should be included when available [15].

Where study designs permit, pooled efficacy and safety analyses help readers understand the IMP’s overall profile. Pooled safety analyses are particularly useful for identifying safety signals. For efficacy, pooling may not always be feasible due to heterogeneity in study design, especially between early‑ and late‑phase trials. In such cases, a narrative synthesis integrating findings across studies is appropriate.

Conclusion

The ubiquity of the Investigator’s Brochure in drug development requires teams to apply it flexibly across diverse situations. As these examples illustrate, multiple approaches are possible, and some serve the document’s purpose more effectively than others.

References

1. International Council for Harmonisation. ICH E6(R1): Guideline for Good Clinical Practice. 1996.
2. Brosteanu O, et al. Risk analysis and risk adapted on‑site monitoring in non‑commercial clinical trials. Clin Trials. 2009;6(6):585–96.
3. World Health Organization. Operational Guidelines for Ethics Committees That Review Biomedical Research. 2000.
4. U.S. Food and Drug Administration. Investigational New Drug Application (IND). 2018.
5. European Medicines Agency. Detailed guidance for the request for authorisation of a clinical trial. 2005.
6. Fletcher AP. Drug safety tests and subsequent clinical experience. J R Soc Med. 1978 Sep;71(9):693-6.
7. Niche Science & Technology Ltd. (2014) The Investigator’s Brochure: An Insider’s Insight.
8. Day RA. How to Write and Publish a Scientific Paper. 5th ed. Phoenix (AZ): Oryx Press; 1998.
9. European Medicines Agency. Draft Revision 3: Detailed guidance for clinical trial authorisation. 2009.
10. OECD. Principles of Good Laboratory Practice. OECD Series on Principles of GLP and Compliance Monitoring. 1998.
11. Medicines and Healthcare products Regulatory Agency. Common issues identified during clinical trial applications: Non‑clinical. 2014.
12. Pietrobon R, Nielsen KC, Steele SM, et al. Manuscript Architect: a Web application for scientific writing in virtual interdisciplinary groups. BMC Med Inform Decis Mak. 2005;5:15.
13. Rowland M, Tozer TN. Clinical Pharmacokinetics and Pharmacodynamics. 4th ed. Lippincott Williams & Wilkins; 2010.
14. Schwartz DN, et al. Understanding the Differences and Effectively Transitioning between the US Integrated Summaries of Effectiveness and Safety (ISE/ISS) and the CTD Summaries of Clinical Efficacy and Safety (SCE/SCS). Drug Information Journal. 2010;44(5).
15. FDA. Guidance for Industry: Pharmacokinetics in Patients with Impaired Renal Function. 1998.