What Is a Drug Master File (DMF)?

A Drug Master File (DMF) is a confidential submission to the U.S. Food and Drug Administration that provides detailed information about the facilities, processes, or materials used in manufacturing, processing, packaging, or storing a drug. A DMF is not itself an application for approval, and FDA does not approve or reject a DMF on its own. Instead, a DMF exists so that one party — typically a manufacturer or supplier — can give FDA access to proprietary technical detail in support of someone else’s drug application, without having to hand that proprietary detail directly to the applicant.

That structure solves a real, practical problem. An active pharmaceutical ingredient (API) manufacturer, an excipient supplier, or a contract packager often has manufacturing know-how it considers a trade secret — process parameters, impurity profiles, facility layout, container-closure specifications. A drug sponsor building a New Drug Application (NDA), Abbreviated New Drug Application (ANDA), or Biologics License Application (BLA) needs FDA to be able to evaluate that supplier’s contribution, but the sponsor itself doesn’t need to see it. The DMF lets the supplier file the confidential material once, directly with FDA, and then authorize FDA to cross-reference it into as many sponsor applications as the supplier chooses — without re-disclosing anything to any of those sponsors.

Who files a DMF, and who references one

The DMF holder is usually the party furthest from the finished drug product: an API manufacturer, a raw-material or excipient supplier, a packaging-component maker, or a contract manufacturing organization. The DMF holder files the technical dossier and controls it going forward — including deciding who is allowed to reference it.

A sponsor or applicant — the company submitting an IND, NDA, ANDA, or BLA — does not file the DMF itself. Instead, the sponsor asks the DMF holder for a Letter of Authorization (LOA), a document the holder sends to FDA that permits the agency to review specific sections of the DMF as part of that sponsor’s application. FDA reviewers can then read the confidential content directly, without it ever passing through the sponsor’s hands. This is the core mechanic research administrators and regulatory affairs staff need to understand: a DMF is reviewed only in the context of an application that references it, and only the sections the LOA authorizes are opened.

DMF types

FDA organizes DMFs into numbered types based on what kind of information they cover:

• Type II — drug substance (API), drug substance intermediate, or the material used in preparing either, or a finished drug product. This is the most common DMF type.
• Type III — packaging material, such as a container-closure system or component.
• Type IV — an excipient, colorant, flavor, or other material used in preparing a drug product.
• Type V — FDA-accepted reference information that doesn’t fit the other categories, such as certain data submitted to support multiple filings.

Type I DMFs, which originally covered manufacturing sites, facilities, operating procedures, and personnel, are no longer accepted by FDA — that category was phased out because the information it covered is better captured through other parts of the current submission framework (including facility information tied directly to the application it supports). A page discussing DMF types today is describing Types II through V.

Drug Master File vs. Active Substance Master File (ASMF)

Researchers and regulatory staff working across U.S. and European filings often encounter both a DMF and an Active Substance Master File (ASMF) for the same active ingredient, and it’s easy to conflate them. They serve the same underlying purpose — letting a manufacturer share confidential manufacturing detail with a regulator without disclosing it to the applicant — but they sit under different regulatory systems. A DMF is filed with FDA and referenced into a U.S. application (NDA, ANDA, BLA, or IND). An ASMF is the equivalent mechanism used with European regulatory authorities (including under the EMA’s centralized procedure and national competent authorities) for marketing authorization applications in the EU. The two are not interchangeable submissions — a DMF on file with FDA does not substitute for an ASMF in a European filing, and vice versa — though a manufacturer supplying both markets will typically maintain parallel dossiers built from much of the same underlying technical data. See the ASMF dictionary entry for how the European mechanism is structured.

What a DMF is not

A DMF is not a stand-alone approval, and it does not expire or need renewal on its own review clock the way an application does. It is also not the same document as a Trial Master File (TMF), despite the similar name — a TMF documents how a specific clinical trial was conducted (protocols, consents, monitoring records) for inspection readiness, while a DMF documents how a drug substance, excipient, or packaging component is manufactured. The two are unrelated except for sharing the word “file” and both belonging to the drug development and regulatory-submission world.

Why this matters for a research organization

Most people working inside a research administration office won’t file a DMF themselves — that’s a manufacturer or supplier function. Where it becomes practically relevant is earlier in the process, when an Investigational New Drug (IND) application is being assembled for an investigator-initiated or sponsor-initiated trial. If the drug substance, a key excipient, or the packaging comes from an outside manufacturer, the sponsor needs a current Letter of Authorization from that DMF holder before submission — without it, FDA has nothing to cross-reference and the application is incomplete on that point. Regulatory affairs staff, clinical research coordinators, and grants/contracts administrators supporting an IND-holding investigator should confirm early which components of the investigational product rely on a third-party DMF, and get the LOA request into the supplier’s queue well before the submission deadline, since a DMF holder can take time to process an authorization request. This same due-diligence step applies to organizations supporting off-label use protocols or device-adjacent drug combination products, where the underlying material may also be covered by a DMF.

Key points

• A DMF is a confidential technical submission to FDA, not an application for drug approval.
• It is filed by a manufacturer or supplier and referenced — via a Letter of Authorization — into a sponsor’s IND, NDA, ANDA, or BLA.
• Current DMF types are II (drug substance/product), III (packaging), IV (excipients), and V (other FDA-accepted reference material); Type I is no longer accepted.
• The EU equivalent is the Active Substance Master File (ASMF); the two systems are not interchangeable.
• For a research organization, the practical task is confirming a current LOA is in place from every third-party DMF holder whose material feeds into an IND before that IND is submitted.