ICH M4 gave the industry the Common Technical Document — five modules, one structure, filed with FDA, EMA, PMDA, and other ICH-aligned regulators without rebuilding the dossier from scratch each time. That reputation is earned for four of the five modules. Module 1 was deliberately left out of the harmonized guideline: it is administrative and regional by design, and each authority still defines its own content and format for it. Teams that plan a global submission as one build quietly discover, late, that Module 1 was never the harmonized part.

What M4 actually harmonized

M4 organizes a marketing application into five modules: Module 1 (administrative information and prescribing information), Module 2 (CTD summaries — the overviews and quality/nonclinical/clinical summaries), Module 3 (quality, reconciled to the CMC data package), Module 4 (nonclinical study reports), and Module 5 (clinical study reports). The parent guideline and its annexes — M4Q, M4S, and M4E — set the common organization and content expectations for Modules 2 through 5 across the ICH regions. That is the real achievement: a sponsor builds the quality, nonclinical, and clinical core once, to one structure, instead of maintaining a separate dossier shape for every authority.

2–5
The CTD modules ICH M4 actually harmonizes across regions.
Module 1
Administrative and regional information — defined independently by each authority, not by M4.
M8
The separate ICH guideline covering the eCTD electronic specification, distinct from M4's content structure.

Why Module 1 still catches teams

Module 1 holds the cover letter, application form, prescribing information or labeling, and the administrative correspondence a given authority wants to see. None of that is harmonized by M4, and the differences are not cosmetic. FDA's Module 1 runs on its own forms and administrative conventions. EMA's Module 1 carries an EU-specific application form and labeling that, for a centralized procedure, has to exist in every required EU language. PMDA's Module 1 follows its own Japan-specific administrative structure. A global regulatory strategy that treats the dossier as one build and three light reformats will find Module 2 through 5 travel reasonably well — and Module 1 does not.

  • FDA's Module 1. Its own administrative forms, cover letter conventions, and US prescribing information — built to FDA's own regional specification, not M4's.
  • EMA's Module 1. The EU application form plus labeling (SmPC, package leaflet, labeling text) that a centralized filing needs translated into every required EU language — a workstream with its own timeline, independent of the quality dossier underneath it.
  • PMDA's Module 1. Japan-specific administrative documentation that follows PMDA's own regional conventions rather than any ICH-harmonized template.
  • The planning mistake. Scoping a multi-region filing as 'build the CTD once' instead of 'build Modules 2 through 5 once and Module 1 three times' is what turns a predictable administrative workstream into the thing that's still open when the clinical and quality sections are long since locked.
The CTD was never sold as fully harmonized. It was sold as a harmonized core with a regional front door — and the front door is usually the last thing built. Why Module 1 deserves its own timeline

M4 sets the structure; M8 sets the transport

A second, related confusion sits next to the Module 1 gap: M4 and the eCTD are not the same guideline. M4 defines what belongs in each module and how the content is organized. ICH M8 defines how that content is packaged and transmitted electronically — the backbone, the folder and file conventions, and the lifecycle operations a sequence uses to add, replace, or withdraw documents over the life of an application. eCTD is the electronic implementation of M4's structure, built to M8's specification; it does not change what M4 says belongs in Module 1 versus Modules 2 through 5. A team that has solved its eCTD publishing and gateway transmission workflow has solved a real problem, but it is a different problem from the regional content gap Module 1 represents.

A multi-region CTD sequence worth running early
  1. Map each region's Module 1 requirements first. Confirm what FDA, EMA, PMDA, or any other target authority actually wants before assuming one version ports across regions.
  2. Build the Module 2-5 core once. Author the harmonized summaries, quality, nonclinical, and clinical sections to the ICH M4 structure a single time.
  3. Treat eCTD (M8) as its own compliance layer. Plan electronic packaging, validation, and gateway transmission separately from the M4 content work.
  4. Give Module 1 its own regional timeline. Staff and schedule it as a distinct workstream per region, not a late add-on to the harmonized core.

None of this is exotic once a team draws the line in the right place. It is a planning distinction: the harmonized core in Modules 2 through 5 gets built once; Module 1 gets scoped, staffed, and scheduled separately for every region on the filing plan; and the electronic packaging under M8 is tracked as its own workstream rather than folded silently into either. Sponsors who build their regulatory submissions plan around that distinction are the ones who reach filing week without discovering that the 'harmonized' dossier still needs a regional front door nobody scheduled time for.

Frequently asked questions

Is the entire CTD harmonized across FDA, EMA, and PMDA?

No. ICH M4 harmonizes Modules 2 through 5 — the overview and summary documents, the quality (CMC) data, the nonclinical study reports, and the clinical study reports. Module 1, the administrative and regional information, is explicitly excluded from the harmonized guideline and is defined separately by each region.

What is the difference between the CTD (M4) and the eCTD (M8)?

M4 defines what goes in the dossier and how it is organized into five modules. M8 defines how that content is packaged and transmitted electronically — the file structure, the XML backbone, and the lifecycle operations (new, replace, delete) a sequence uses. eCTD is the electronic implementation of the structure M4 defines, not a separate content standard.

Can Module 1 documents be reused across FDA, EMA, and PMDA submissions?

Not directly. Each region sets its own Module 1 content and format — application forms, labeling, administrative correspondence — so Module 1 is typically rebuilt per region even when Modules 2 through 5 carry over with comparatively light reformatting.

Sources & further reading

  1. ICH. Multidisciplinary Guidelines — M4 Common Technical Document and the M4Q/M4S/M4E annexes. ich.org
  2. FDA. Common Technical Document (CTD) — overview of the CTD format for marketing applications. fda.gov

This article is provided for general informational purposes and reflects the regulatory landscape as of October 2026. It is not legal or regulatory advice. Confirm current ICH M4/M8 implementation and each region's Module 1 requirements with FDA, EMA, PMDA, or qualified counsel before acting.