'Femi Fajimi

Understanding the CTD: Where Clinical Data Meets Regulatory Writing 

By ‘Femi Fajimi | 29 May 2025 

The Common Technical Document (CTD) is the backbone of global regulatory submissions. A standardised format that allows pharmaceutical companies to present evidence to regulatory authorities across regions. 

For medical writers, especially those working in clinical and regulatory settings, understanding the CTD isn’t just about structure. It’s about knowing where data becomes narrative, where trial outcomes are evaluated, and where writing must be both scientific and strategic. 

In this article, I explore the CTD’s core modules, where writers typically contribute, and how clinical data is transformed into clear, compliant summaries. 

What Is the CTD? 

The CTD was developed by the International Council for Harmonisation (ICH) to establish a standardised format for submitting information to regulatory authorities in the US, EU, and Japan, and its structure is now used worldwide. 

It consists of five modules, each with a distinct function: 

Module	Content
1	Administrative and regional information (varies by country)
2	Summaries and overviews of Modules 3–5 (includes writer-heavy content)
3	Quality (Chemistry, Manufacturing and Controls – CMC)
4	Non-clinical study reports (e.g. pharmacology, toxicology)
5	Clinical study reports and related data (e.g. CSRs, ICFs, protocols)

✍️ Where Medical Writers Contribute 

Most medical writers are involved in Modules 2 and 5. Here’s how: 

Module 2 – Summaries and Overviews 

This module provides a bridge between the raw d 

This module provides a bridge between the raw data (Modules 3–5) and regulatory decision-making. Writers help create structured summaries that explain clinical and scientific data to reviewers. 

Key sections for writers include: 

• 2.5 – Clinical Overview 

• A concise narrative discussing the clinical development, safety and efficacy, benefit-risk, and the disease context. 

• 2.7 – Clinical Summary 

• A detailed, structured summary of the clinical data, including: 

• 2.7.1: Biopharmaceutics 

• 2.7.2: Clinical Pharmacology 

• 2.7.3: Clinical Efficacy 

• 2.7.4: Clinical Safety 

• 2.7.5 & 2.7.6: Tabulated summaries (study-level listings) 

These sections demand not only summarisation but also interpretation, alignment with study objectives, and strict consistency with Module 5. 

Module 5 – Clinical Study Reports 

This module houses full clinical study reports (CSRs), protocols, amendments, and other documents submitted for regulatory evaluation. 

Writers contribute to: 

• Drafting CSRs in alignment with ICH E3 guidance 

• Ensuring results and safety data are clearly presented 

• Preparing appendices (e.g. narratives, protocols, statistical methods) 

• Supporting data accuracy and source alignment with summaries in Module 2 

A Practical Example 

Let’s say a Phase III trial investigated a fictional Alzheimer’s drug, Neuromexa. 

Module 5 (CSR excerpt): 

“At Week 24, the Neuromexa group had a mean improvement of 4.5 points on the ADAS-Cog scale versus 1.2 points in the placebo group (p=0.008). One SAE (urinary tract infection) was reported in the Neuromexa group and resolved with treatment.” 

How this appears in Module 2: 

• 2.7.3 Clinical Efficacy: 

• “Neuromexa demonstrated statistically significant improvement in cognitive function at Week 24 (mean change: 4.5 vs 1.2; p=0.008), meeting the study’s primary endpoint.” 

• 2.7.4 Clinical Safety: 

• “Adverse events were generally mild. One serious event (UTI) occurred in the Neuromexa group and resolved without complications.” 

Here, the writer’s role is to interpret, summarise, and present the data clearly, not to analyse it but to communicate its meaning and relevance within the submission. 

Why the CTD Matters for Writers 

Key Skill	Why It’s Important
Data Interpretation	To ensure summaries reflect the source data accurately
Structured Scientific Writing	To meet ICH expectations and align with reviewer logic
Consistency Across Documents	To avoid discrepancies between summaries and source reports
Regulatory Awareness (e.g., ICH E3)	To write in compliance with global standards

Final Thoughts 

Understanding the CTD gives medical writers the context to communicate more effectively. It shows us where our words meet data and where good writing makes the difference between clarity and confusion. 

As I continue developing my skills, I’ve found that the CTD is not just a regulatory requirement; it’s a tool that brings discipline, structure, and purpose to scientific communication. 

References: 

ICH. M4: Organisation of the Common Technical Document. https://ich.org 

ICH. E3: Structure and Content of Clinical Study Reports. 

EMA. Clinical Data Requirements. 

FDA. Guidance for Industry: Clinical Study Reports (2018).