Master protocols in rare disease research: why one study can serve many patients

A rare disease is one that affects fewer than 200,000 people in the United States. The National Institutes of Health estimates roughly 7,000 to 10,000 such conditions exist, together affecting about 30 million Americans, and that fewer than five percent have an approved therapy. For each individual disease, the pool of eligible research participants is small, geographically dispersed, and often split into subtypes that behave differently. Traditional clinical trial design, which studies one intervention against one disease in one bounded population, was not built for that reality.

Master protocols were.

A master protocol is a single overarching study that answers several research questions at once. It can evaluate multiple candidate therapies, multiple diseases, or both, using shared infrastructure, shared oversight, and, where appropriate, a shared control group. For advocacy communities working on rare disease research, understanding how master protocols work is central to explaining research options to the families your organization serves.

What a master protocol is, in plain language

A traditional clinical trial focuses on one investigational product tested against one disease, usually with a comparison group receiving placebo or standard care. Every new candidate therapy requires a new study, a new set of sites, and a new regulatory package. In diseases where thousands of eligible participants exist, this design works reasonably well.

In rare disease research, it often does not. A study that needs three hundred participants may sit open for years because the eligible population is spread thinly across the country, or because subtypes of the same condition cannot be grouped together statistically.

A master protocol solves this by building the trial machinery once and reusing it. The U.S. Food and Drug Administration defines a master protocol as a protocol with multiple substudies, coordinated to evaluate one or more medical products in one or more diseases or conditions within the overall study structure. In practical terms, a single centralized screening system identifies every substudy a participant might qualify for, one steering committee and one independent data monitoring committee oversee the whole study, and one shared data system connects everything together.

The result is a trial framework designed to answer many questions in parallel, rather than one after another.

For a plain-language primer on how any clinical trial is structured, see Clinical Research Basics: What Every Trial Participant Should Understand Before Enrolling.

The three types: basket, umbrella, and platform trials

Master protocols come in three main forms. Each keeps something constant and varies something else.

A basket trial tests one investigational product across multiple diseases or disease subtypes that share a common biological feature, usually a specific gene mutation or biomarker (a measurable biological trait, such as a protein or genetic change). A single targeted therapy might be studied in several rare cancers that all carry the same mutation, regardless of where in the body the tumor originates.

An umbrella trial does the opposite. It studies one disease under a single overarching framework, then sorts participants into different arms based on their biomarker profile, with each arm evaluating a different candidate therapy.

A platform trial is the most flexible of the three. It studies multiple therapies in one disease over time, with new arms added as new candidates emerge and underperforming arms dropped when interim data suggests they will not work. Platform trials are often described as perpetual because the study framework continues long after any single arm ends.

Is a basket trial the same as a platform trial?

No. A basket trial evaluates one investigational product across several diseases or subtypes at once. A platform trial evaluates several investigational products in one disease, with arms coming and going over time. Basket, umbrella, and platform designs can overlap, and some master protocols combine features of more than one, but the underlying question each is built to answer is different.

For a broader introduction to how clinical trials are structured, see Clinical Trials Explained: Simple Guide for Beginners.

Why rare disease research needs a different trial model

The obstacles rare disease research faces are structural, not motivational. Investigators want to run studies. Families want candidates evaluated. The system was simply built around common conditions.

Four features of the rare disease landscape make traditional trial design particularly hard to apply. First, patient populations are small, sometimes only a few hundred people worldwide. Second, those populations are geographically dispersed, meaning any single site may see only a handful of eligible participants a year. Third, many rare diseases include multiple subtypes with distinct genetic drivers, which limits statistical borrowing across subgroups. Fourth, natural history data, the record of how a disease progresses without intervention, is often incomplete, which makes it harder to design the right endpoints and comparison groups.

Master protocols address each of these directly. Shared screening reaches more potential participants faster. Shared control arms reduce the total number of people required to run several comparisons. Adaptive design allows a study to shift resources toward arms that appear to be working. And every participant who enrolls contributes to a shared data foundation that improves the next arm and the next question.

For more on how research is advancing in this space, see Hope in Research: How Clinical Trials Are Transforming Rare Disease Treatment.

How master protocols expand access for rare disease communities

For a family whose specific rare condition has never been studied on its own, a master protocol is often the only realistic route to a candidate therapy. Several access-related advantages follow from the design.

Pooling across subtypes means a basket trial can enroll participants with different diseases that share a common driver, reaching a workable sample size where no single subtype could. Shared control groups mean fewer participants overall are assigned to placebo or standard care, because one control arm can serve several comparisons at once. Faster time to answer means promising signals are identified sooner, and disappointing arms are stopped sooner. The ability to add new arms without starting a new trial from scratch shortens the years typically lost to regulatory start-up between studies.

Will a participant receive the study drug or a placebo?

Not necessarily a placebo. Many master protocols deliberately weight assignment toward active investigational products, with some platform trials using ratios of three participants on an active arm for every one on the shared control. Some basket trials have no control arm at all. The informed consent process for any specific study will describe exactly how assignment works.

For more on how modernized trial designs support broader participation, see How Decentralized Trials May Improve Research Access.

What adaptive design means for participants

Master protocols rely heavily on adaptive design, a set of pre-specified rules that allow a study to be adjusted based on data as it accumulates. Adjustments are not made informally. They follow statistical thresholds that are written into the protocol before the study opens.

The most common adaptations are futility stopping, where an arm is closed early because interim data shows a low probability that the investigational product will benefit participants, and success stopping, where an arm continues into the next phase because interim data is strongly favorable. New arms can also be added as new candidates become ready.

An independent data monitoring committee, made up of clinicians and statisticians with no financial stake in the outcome, reviews accumulating data at pre-set intervals and makes recommendations about whether each arm should continue, stop, or be modified. Participants and investigators do not see unblinded interim data, which protects the scientific integrity of the study.

What happens if a subtype's arm is dropped?

Dropping an arm is a planned, ethical feature of the design. It happens when independent data monitors conclude that continuing an investigational product is unlikely to help participants. When an arm closes, participants already enrolled are informed, transitioned to appropriate follow-up care, and often given information about other eligible studies. The shared control data continues to serve the remaining arms.

For a deeper explanation of control groups and randomization, see Placebos and Controls: What It Means in Your Study.

Regulatory oversight and participant protections

Master protocols are held to the same regulatory and ethical standards as traditional clinical trials. In the United States, they operate under the FDA investigational new drug framework, follow International Council for Harmonisation good clinical practice guidelines, and require informed consent from every participant.

The complexity of a master protocol actually adds oversight rather than reducing it. A central institutional review board reviews the overall protocol and each substudy amendment. An independent data monitoring committee reviews accumulating safety and efficacy data across all arms. Communication plans and data firewalls prevent inappropriate sharing between competing investigational products.

Recent policy activity reflects the growing importance of these designs. The FDA issued draft guidance on master protocols for oncology in 2022, expanded that guidance to cover drug and biological product development more broadly in late 2023, and revised the draft in 2026 with specific recommendations on basket trials. The International Council for Harmonisation released its first globally harmonized draft framework for adaptive designs, known as E20, in 2025. Policy is trending toward more master protocols, with clearer expectations for how they should be designed and reviewed.

Are master protocols regulated the same way as traditional trials?

Yes, and often with additional layers. The same informed consent standards, ethics review requirements, and safety monitoring rules apply. Central institutional review boards and independent data monitoring committees add oversight specifically suited to the complexity of running multiple arms and substudies at once.

For context on why open trial information matters for participant trust, see Transparency in Clinical Research: Why Trial Information Access Matters.

Where advocacy groups fit in

Advocacy organizations play a substantive role in every stage of a master protocol, not only in the recruitment window at the end.

At the design stage, advocacy input shapes endpoints, visit schedules, travel and lodging support, and the language of the informed consent document. Bringing the community voice into design conversations early, before resources are committed, means later changes are less costly and more likely to happen.

At the education stage, advocacy groups translate a complex trial framework into materials families can actually use. Master protocols are harder to explain than single-drug studies, because arms may change over time and assignment logic is more intricate. Plain-language explainers, short videos, and layered consent documents developed with researchers substantially close that gap.

At the data stage, advocacy-run registries and natural history studies produce the baseline evidence that makes master protocols possible in the first place. A well-maintained registry can shorten the time to a first substudy by years.

For more on the strategic value of advocacy involvement, see Why Patient Advocacy Groups Matter in Decentralized Clinical Research.

How DecenTrialz supports rare disease trial matching

Master protocols work best when the right participants can be identified quickly across a wide geography. That is where DecenTrialz fits.

DecenTrialz uses AI-assisted participant matching to align individuals with biomarker-defined subgroups and eligibility criteria across active clinical studies. A registered nurse then completes an initial pre-screening review, adding a layer of clinical judgment before any information reaches a research site. The research site team owns final eligibility determination, informed consent, the study walk-through, and enrollment decisions.

For advocacy organizations, this pathway shortens the distance between the community member exploring a study and the research site that runs it, without displacing any of the medical decision-making that belongs at the site. Learn more at decentrialz.com.

Learn more about rare disease clinical trial access

If your organization supports a rare disease community, master protocols are worth watching closely. The designs open participation to smaller subtypes, reduce placebo exposure, and shorten the time between a candidate therapy and a scientific answer about whether it works.

To explore how AI-assisted matching and registered nurse-led pre-screening can connect community members with active studies, visit decentrialz.com.