Definition

A Drug Master File is a voluntary, confidential submission to a regulatory agency—most commonly the US FDA—that contains detailed information about how a drug substance, excipient, or packaging component is manufactured, tested, and controlled. Its practical purpose is to let an API manufacturer or CDMO protect proprietary process information while still making it available for regulatory review as part of a sponsor's drug application.

 

How a DMF Works—Structure, Referencing, and Maintenance

The FDA recognises five types of Drug Master Files. Type II DMFs are by far the most common in API manufacturing—they cover drug substances, intermediates, and the materials and processes used in their preparation. In Europe, the equivalent mechanism is the Active Substance Master File (ASMF). Japan and other regulatory regions have their own analogous systems, each with slightly different content requirements.

A Type II DMF has two parts. The Open Part contains non-confidential information—essentially the drug substance characterisation and summary data that the sponsor needs to include in their own NDA or ANDA. The Restricted Part holds the confidential manufacturing and process details that are reviewed by the agency but not shared with the applicant. When a sponsor wants to use a particular CDMO's drug substance, the CDMO issues a Letter of Authorization allowing the FDA to cross-reference the Restricted Part during review.

A DMF is never reviewed on its own initiative—it sits dormant until a drug application referencing it is submitted for review. This means timing matters: if a DMF contains deficiencies and an NDA referencing it goes in for review, those deficiencies can hold up the approval. DMF holders have a responsibility to keep the file current—updating it whenever manufacturing changes are made and filing annual reports to confirm the file remains accurate.

 

Related Topics

Related Terms

  • CMC (Chemistry, Manufacturing and Controls)
  • New Drug Application (NDA)
  • API CDMO
  • cGMP (Current Good Manufacturing Practice)
  • Impurity Profile of an API
  • Key Starting Material in API Synthesis

FAQs

  1. Is a Drug Master File mandatory?

    In the US, DMF submission is voluntary—but it is practically necessary when a third party manufactures the drug substance for an NDA or ANDA. It is the mechanism by which the manufacturer keeps process information confidential from the applicant while making it available to the FDA.

  1. When does the FDA review a DMF?

    A DMF is not reviewed at submission. It is reviewed when the FDA receives a Letter of Authorization from the DMF holder referencing a specific drug application under review.

  1. How frequently should a DMF be updated?

    Whenever a change occurs that needs to be reflected—process modifications, site changes, method updates, or new stability data. Annual reports are also required to confirm the file's accuracy.

  1. What is the difference between a US DMF and an EU ASMF?

    Both protect confidential drug substance manufacturing information while enabling regulatory review, but they differ in structure, terminology, and content requirements. Companies supplying global markets typically need both, maintained in parallel.

  1. What happens if the DMF and the NDA CMC section are inconsistent?

    Inconsistencies are a common source of deficiency letters and can delay approval. The DMF holder and sponsor's regulatory teams need to maintain alignment throughout development and verify consistency before submission.

 

Explore how Neuland manages DMF preparation and maintenance as part of its API CDMO services. Explore CDMO Services