CTD Format & eCTD Publishing for FDA Submission: A Complete 2026 Guide

Submitting a drug application to the US FDA requires data organized and formatted to a precise technical standard. The Common Technical Document (CTD) format and its electronic implementation, the eCTD, are mandatory for all NDAs, ANDAs, INDs, and BLAs submitted to the FDA. Understanding CTD structure and eCTD technical requirements is essential for any pharmaceutical company targeting the US market.

What Is the CTD Format?

The Common Technical Document is an internationally harmonized format for pharmaceutical registration dossiers, developed by ICH. The CTD allows a single dossier to be submitted to regulatory agencies in the US, Europe, Japan, and other ICH markets with minimal reformatting.

CTD Module Structure

• Module 1 — Administrative information: application forms, product labels, proposed labeling, and FDA-specific documents

• Module 2 — CTD summaries: quality overall summary, non-clinical and clinical overviews

• Module 3 — Quality: pharmaceutical development, manufacturing process, control of drug substance and product, and stability data

• Module 4 — Non-clinical study reports: pharmacology, pharmacokinetics, and toxicology

• Module 5 — Clinical study reports: bioavailability, clinical pharmacology, efficacy, and safety studies

What Is eCTD?

The electronic Common Technical Document (eCTD) is the technical specification for submitting CTD-formatted dossiers electronically. The FDA has required eCTD format since 2017 for most NDAs, ANDAs, BLAs, and INDs. See our Dossier Development & eCTD Publishing service for full submission support.

eCTD Technical Requirements

Document Format Requirements

All documents must be submitted as PDFs: letter size (8.5 x 11 inches), minimum 1-inch margins, minimum 12-point body text, text-searchable (not scanned), with bookmarks and hyperlinks for navigation.

eCTD Backbone and XML Structure

The eCTD backbone is an XML file (index.xml) describing the organizational structure of the submission. It must conform to the ICH eCTD specification and validate against FDA criteria. Submissions with backbone errors are rejected by the Electronic Submissions Gateway before reaching a reviewer.

Sequence Numbers and Lifecycle Management

eCTD submissions are organized into sequences starting from 0000. The lifecycle management system allows subsequent sequences to reference and replace earlier documents, maintaining a complete navigable regulatory history.

FDA eCTD Validation

Every eCTD submission must pass automated validation. Submissions with errors receive a Refuse to File notification and must be corrected — losing the original application date. Common failures include incorrect file naming, broken hyperlinks, non-searchable PDFs, and XML backbone errors.

Module 3: Quality Dossier for ANDA Applications

For ANDA applications, the Module 3 quality dossier is the submission's core. Key components include the Drug Substance section (characterization, control, stability for the API) and the Drug Product section (pharmaceutical development, manufacturing process, and stability data). Our team at Axentra provides full eCTD dossier development services.

Type II Drug Master Files

Foreign API manufacturers typically must submit a Type II Drug Master File (DMF) to the FDA. The DMF contains confidential API manufacturing and quality information reviewed as part of the drug product application. Type II DMFs follow CTD Module 3 structure and must be maintained in eCTD format.

Common eCTD Mistakes by Foreign Manufacturers

• Submitting European CTD dossiers without adapting to FDA-specific Module 1 requirements

• Using scanned PDFs — the FDA will reject non-searchable documents

• Incorrect sequence numbering — every submission must have a unique sequential number

• Broken or missing hyperlinks — all cross-references must be navigable

• Outdated eCTD specification version

eCTD and CTD Services at Axentra

Axentra provides CTD authoring, eCTD publishing, and regulatory submission services for NDA, ANDA, IND, BLA, and Type II DMF applications. Services include Module 3 quality dossier preparation, eCTD publishing and validation, and ongoing lifecycle management. Contact us for a free assessment.