What is the eCTD backbone?
The eCTD backbone is essentially a hyperlinked table of contents. The hyperlinks within this table of contents links the various files throughout the submission. Use of this table of contents eases access to different parts of the submission using a central focal point. The contents of the eCTD backbone are standardized by ICH and/or the FDA (for US submissions). There are generally 2 backbones: one for Module 1 (us-regional.xml) and one for Modules 2-5 (index.xml). The Module 1 backbone is region-specific and varies between other Regulatory Agencies accepting eCTD submissions. Please see the FDAs Module 1 and Modules 2-5 backbone specifications.
