ICH M4 (Common Technical Document / CTD)

ICH M4 is the multidisciplinary (M-series) guideline issued by the International Council for Harmonisation (ICH) that establishes the Common Technical Document (CTD): a single, harmonized format for organizing the quality, nonclinical (safety), and clinical (efficacy) data submitted when registering a pharmaceutical for human use. Before the CTD existed, a sponsor seeking approval in multiple countries had to reformat the same underlying data into different dossier structures for each regulatory authority. ICH M4, first reaching ICH Step 4 adoption in July 2000, replaced that with one structure that the United States (FDA), European Union (EMA), Japan (PMDA), and other ICH regulatory members all accept for the technical content of Modules 2 through 5.

The five CTD modules

Every CTD-structured submission — whether a US New Drug Application (NDA), Biologics License Application (BLA), EU Marketing Authorisation Application (MAA), or the equivalent in another ICH region — follows the same top-level module structure:

• Module 1 — Administrative and regional information. Not harmonized by ICH; each regulatory authority defines its own Module 1 content (application forms, labeling, prescribing information, and correspondence specific to that jurisdiction).
• Module 2 — CTD summaries. The Quality Overall Summary, Nonclinical Overview and Summary, and Clinical Overview and Summary — reviewer-facing documents that synthesize the detailed data presented in Modules 3-5.
• Module 3 — Quality. Chemistry, manufacturing, and controls (CMC) data for the drug substance and drug product, organized per the ICH M4Q guideline.
• Module 4 — Nonclinical study reports. Pharmacology, pharmacokinetics, and toxicology study reports, organized per the ICH M4S guideline.
• Module 5 — Clinical study reports. Clinical study protocols and reports — including full Clinical Study Reports (CSRs) prepared under the ICH E3 structure — plus other clinical data, organized per the ICH M4E guideline.

Modules 2 through 5 are harmonized: the same module numbering, section headers, and internal ordering apply regardless of which ICH regulatory authority receives the submission. Module 1 is the deliberate exception — ICH left it region-specific because administrative and labeling requirements are inherently jurisdiction-bound and were not considered practical to harmonize.

M4, M4Q, M4S, and M4E: a guideline family, not one document

"ICH M4" is often used as shorthand for the entire CTD framework, but it is actually the overarching organizational guideline in a family of related M4 documents. The umbrella M4 guideline sets out the five-module structure itself; three companion guidelines then specify, in detail, what belongs in each scientific module and in what order:

• M4Q — the Quality module (Module 3) content and structure, governing CMC data for the drug substance and drug product.
• M4S — the Safety module (Module 4) content and structure, governing nonclinical study report organization.
• M4E — the Efficacy module (Module 5) content and structure, governing clinical study report and protocol organization.

Each of these has been revised since the original 2000 adoption (for example, the current EMA-published version is M4(R4), with M4Q and M4E carrying their own revision histories), so a regulatory affairs team assembling a submission checks the current version of each relevant sub-guideline rather than assuming the original 2000 text still applies unchanged.

CTD versus eCTD

ICH M4 defines the CTD as a document structure — it does not, by itself, specify a file format or electronic submission mechanism. That is the role of a separate specification, the electronic Common Technical Document (eCTD), which layers an XML backbone on top of the same Module 1-5 hierarchy to create a navigable, lifecycle-managed electronic submission. In practice, essentially all current NDA, BLA, and MAA submissions to major ICH regulatory authorities are filed as eCTD rather than as a paper or loose-electronic CTD, since FDA and EMA have both moved to mandatory electronic-only submission in the eCTD format. ICH M4 remains the reference for what the five modules must contain; eCTD is the reference for how that content is packaged, indexed, and transmitted.

Why the CTD structure matters for research administration

For research administrators and clinical operations staff who are not themselves regulatory affairs specialists, the CTD’s practical relevance is usually indirect but real: it determines the final destination format for study outputs your team helps produce. A Clinical Study Report written under ICH E3 is written that way specifically so it can be placed into Module 5 without restructuring. Knowing that a trial’s outputs will eventually need to sit inside a CTD-structured submission is one reason sponsors and CROs standardize CSR templates, data structures, and nonclinical report formats well before a marketing application is assembled, rather than retrofitting them at submission time.