Converting an existing protocol into a master protocol under an active IND: what FDA expects

Sponsors running a conventional single-drug trial often reach a point where they want to widen it: add a second investigational agent, open a new disease cohort, or move to a shared-control platform design. The natural question is whether the existing protocol can simply be amended into a master protocol under the IND that is already open, or whether FDA expects a different regulatory structure. The short answer from FDA's guidance is that a master protocol is treated as a distinct regulatory object with its own IND, and that FDA's recommended path is generally to stand up a master protocol IND rather than to retrofit a stand-alone protocol in place. Additions after that are handled as protocol amendments. This article walks through what FDA has actually said.

What FDA means by "master protocol"

FDA defines a master protocol as a single overarching protocol with multiple substudies, designed to evaluate more than one hypothesis under a shared structure ⁶. The guidance groups the designs into three familiar categories:

• Umbrella trials evaluate multiple drugs for one disease, condition, or disease subtype ⁶.
• Basket trials evaluate a single drug across multiple diseases, conditions, or disease subtypes ⁵.
• Platform trials evaluate multiple drugs for one or more diseases in an ongoing manner, with drugs entering and leaving the platform over time; some platform trials incorporate both umbrella and basket components ⁵.

The appeal is efficiency. FDA describes master protocols as a way to accelerate development by maximizing information from a single research effort, sharing protocol elements, infrastructure, and oversight, and using a shared control arm across multiple drugs ⁴. They are particularly useful where recruitment is difficult, because comparing several drugs against one shared placebo arm reduces the number of participants assigned to placebo ⁴. For basket and platform designs, the guidance also discusses borrowing information across substudies, including Bayesian approaches ¹⁰.

The relevant primary sources are FDA's draft guidance Master Protocols for Drug and Biological Product Development (draft, most recently revised June 2026) ⁷¹ and the earlier final guidance COVID-19: Master Protocols Evaluating Drugs and Biological Products for Treatment or Prevention (final, May 2021) ⁷². RAPS has reported that FDA revised the 2023 draft to add a dedicated basket-trial section, clarify design and analysis issues, and expand the discussion of communication among the master protocol sponsor, individual drug sponsors, and regulators while the protocol is running ²⁸.

The core answer: a master protocol generally belongs in its own IND

This is the pivot point for anyone thinking about "converting" an existing protocol. FDA's guidance states that each master protocol should generally be submitted in a new IND, not folded into an IND that was opened for a single earlier program ¹⁸¹⁹. The guidance goes further: the master protocol IND should contain only the master protocol, and the master protocol should be conducted under that IND only ¹⁵. FDA also provides an example eCTD structure showing the master protocol and each substudy organized in separate folders within that single IND ²¹.

Practically, this means FDA does not describe a mechanism for "converting" a stand-alone, non-master protocol into a master protocol in place within the original IND. We did not find any language in the guidance framing conversion as a formal concept [convert: 1][convert: 17]. What FDA describes instead is building the master protocol as its own regulatory structure and then expanding it through amendments. A sponsor who wants to grow an ongoing trial into a platform should expect to establish a master protocol IND rather than simply repurpose the existing protocol ¹¹⁸.

There is a narrower situation where separate INDs come into play. FDA acknowledges that in some basket or platform settings, individual substudies may sit under their own substudy INDs. When that structure is used, the master protocol sponsor is expected to coordinate cross-references between the master protocol IND and each substudy IND, and to keep all of them current with the relevant amendments and notifications ¹¹⁶¹⁷. RAPS has reported the same pattern in FDA's cell and gene therapy umbrella-trial guidance: each product version is generally submitted in a separate IND, but the sponsor can designate one "primary" IND holding most clinical information, with "secondary" INDs cross-referencing it ³⁵⁴⁰.

How additions and changes are handled: protocol amendments

Once the master protocol IND exists, FDA's model for growth is the protocol amendment, governed by the ordinary IND framework in 21 CFR part 312 ¹. The guidance is specific about which submission goes where:

• If all substudies live under the master protocol IND, a new substudy (for example, a new drug or a new population) is submitted to the master protocol IND as a protocol amendment ¹⁷.
• Any proposed change to the master protocol itself, or to one of its substudies, is likewise submitted as a protocol amendment ¹⁷.
• If the design uses separate substudy INDs, a new substudy goes into a new, separate substudy IND, with corresponding submissions to the master protocol IND and to the other substudy INDs to notify them and cross-reference the new substudy IND ¹⁷.
• When a substudy protocol is amended, the amendment goes to that substudy IND; when the master protocol is amended, it goes to the master protocol IND ¹⁷.

For adding a new investigational agent, FDA's recommendation is to submit the new drug as a protocol amendment to the master protocol IND, and, for changes that substantively affect safety, quality, or scope, to submit the amendment at least 30 days before initiating the change, for example before opening the new arm ⁷¹⁵²⁰. This mirrors the standard 30-day protocol-amendment expectation under part 312. For an amended master protocol, FDA asks for a clean version and a tracked-changes version, plus a separate document describing the changes ²⁰. For major changes, the cover letter should report the status of each substudy, including whether it is open or complete, its enrollment status, and its substudy IND number if different [convert: 17].

Industry practice reinforces why this structure is attractive. DIA Global Forum authors describe I-SPY2 as a master protocol under a single IND to which agents were added by protocol amendment rather than by writing a new protocol for each agent, so that agents can enter and leave the platform without restarting the study [dia: 84]. The same commentary recommends keeping the master protocol treatment-agnostic and confining amendments to appendices or arm-specific sections, an approach EU-PEARL formalized through Intervention-Specific Appendices added as interventions become available, precisely to avoid major amendments to the master protocol itself [dia: 81]. RAPS has also reported that FDA revised its oncology master protocol guidance to clarify what sponsors should provide when submitting amendments that request protocol expansions, and to address basket-trial dose-finding, safety lead-ins, and comparisons between experimental arms in umbrella trials ⁴¹.

Engage FDA before you restructure

Because master protocols are complex, FDA wants the design and submission approach discussed before the IND is submitted. The guidance recommends requesting a pre-IND meeting to discuss the protocol and submission details, and labeling the cover letter "REQUEST FOR MEETING-MASTER PROTOCOL (Meeting Type B)" ¹. FDA cautions that more than one meeting may be needed before submission, and that the approach should be discussed with the relevant review division or divisions in light of the planned populations, study design, and analytical strategy ¹. Master protocols generally require a high degree of upfront planning and coordination ². This is the practical moment to raise a planned conversion: rather than filing an amendment that reframes an existing single-drug protocol, a sponsor should use the pre-IND interaction to align with FDA on standing up the master protocol IND and on how the current program's data and structure will carry over.

DIA and RAPS commentary points in the same direction: pre-submission meetings, detailed protocols, and prospectively planned modifications are treated as critical for innovative designs, and regulators' scientific advice is especially important where the trial is intended to be confirmatory [dia: 82][dia: 83].

Design and integrity issues that surface on expansion

Expanding a trial into a master protocol is not only a filing exercise; several design elements typically need to be rebuilt:

• Submission logistics. FDA expects electronic submissions to use Study Tagging Files to identify the master protocol and each substudy, with appropriate file-tagging to keep the eCTD organized and reviewable ¹. INDs containing master protocols remain subject to all applicable requirements of 21 CFR part 312 ¹.
• Randomization and controls. FDA recommends randomization, and where the number of drugs changes over time the randomization ratio and analyses must account for periods with different ratios; when participants are eligible for only some arms, analyses should use only the concurrently eligible control participants [convert: 44][convert: 55].
• Safety, eligibility, and oversight. Master protocols may need drug-specific eligibility criteria, independent data monitoring committee oversight, and, in some cases, selective safety data collection [convert: 51][convert: 56].
• Information integrity. FDA notes that expansion raises the risk of inadvertent dissemination of information across arms, which can affect trial conduct and integrity, so data-access and communication controls should be planned and discussed with FDA at the design stage ¹⁸[convert: 56].
• Coordination across divisions. When subject-matter expertise is distributed across review divisions, the master protocol sponsor must manage that coordination, which is one of the recurring burdens FDA and RAPS both flag for master protocols ¹²⁹³¹.

Bottom line

An existing single-drug protocol is not, in FDA's framework, simply amended in place into a master protocol under the original IND. FDA's guidance treats a master protocol as its own regulatory structure that should generally be submitted in a new, dedicated IND containing only that master protocol ¹⁵¹⁸¹⁹. Once that IND is open, growth is exactly what FDA anticipates through protocol amendments: new drugs, new populations, and new substudies are added as amendments to the master protocol IND, subject to the ordinary part 312 requirements including the 30-day expectation for changes that affect safety, quality, or scope ⁷¹⁷²⁰. The recommended sequence is to raise the plan at a pre-IND (Type B) meeting, agree the IND architecture and any cross-referencing to substudy INDs, and then operate the platform by amending appendices and arm-specific sections rather than continually rewriting the master protocol ¹¹⁷[dia: 81]. Where the design instead relies on separate substudy INDs, the sponsor takes on the added obligation of keeping the master protocol IND and each substudy IND cross-referenced and current ¹⁶¹⁷⁴⁰.