Platform trial
Can a continuing trial evaluate multiple interventions under a shared master protocol?
When to use this project
Evaluate multiple interventions with shared infrastructure and prespecified rules for adding, retaining or closing arms. Define each comparison and its eligible population separately.
How it differs
A platform continues across changing arms and calendar epochs. A fixed multi-arm trial need not be a platform, and a platform need not use response-adaptive randomization.
Decisions before you start
- Define master, cohort and arm eligibility, active periods and comparison-specific controls.
- Prespecify governance, multiplicity and shared-control dependence. Nonconcurrent controls require explicit additional assumptions.
- Retain outcome follow-up after arm closure and version the protocol, eligibility and comparison data. The linked general FDA master-protocol guidance is a June 2026 draft, not final guidance.
How the flows work together
Each flow below links to its diagram, steps and tables. Flow order organizes the project; it does not imply that all work is strictly sequential. Data assessment, analysis planning and protocol refinement may inform one another.
1. Platform trial overview
Overview · Master question through evolving comparisons
Use this overview to state the purpose and link to detailed decisions. Keep a versioned protocol and decision register, and add evidence references for the rationale.
2. Cohort and arm eligibility
Selection · Match participants to eligible comparisons
Master eligibility does not guarantee eligibility for every arm. Preserve arm-specific eligibility and available options at each entry date before defining comparison populations.
3. Arm lifecycle and allocation
Conduct · Track entry closure and assignment
Arm entry and closure change the available comparisons over time. Retain protocol versions and continue the required follow-up after recruitment closes.
4. Endpoints estimands and comparisons
Design · Define arm-specific questions and populations
Each comparison needs its own estimand, eligible population and claim family. A shared platform does not imply that every arm is comparable with every participant in the control pool.
5. Interim decisions and governance
Statistics · Prespecify adaptations and review responsibilities
Separate arm-entry decisions, safety monitoring and efficacy review with documented authority. Protect interim information across participating teams and retain a master and arm-specific audit trail.
6. Simulations and sample-size scenarios
Statistics · Evaluate changing platform operating characteristics
Assess changing arms, eligibility, accrual and calendar trends jointly. Shared controls and any borrowing affect the operating characteristics of individual comparisons and claim families.
7. Data populations and control pools
Data · Track epochs and comparator eligibility
Concurrent controls must be eligible for the relevant comparison during its active epoch. Nonconcurrent borrowing requires separate assumptions and sensitivity analyses; it is not equivalent to randomized concurrent evidence.
8. Comparison analysis plan
Statistics · Specify comparisons across calendar epochs
Account for shared-control dependence, time effects, adaptations and multiplicity appropriate to each claim. Report the control pool and active epochs so readers can reconstruct the comparison.
Equations and statistical interpretation
These explanations describe notation and assumptions. Flow does not calculate these values.
Eligible concurrent control set
For comparison k, Aᵢ=0 denotes control assignment, Eᵢₖ=1 arm-specific eligibility, tᵢ entry time and oₖ through cₖ the arm’s active recruitment window.
This illustrates a single continuous recruitment window; pauses and changing eligibility require epoch-specific sets. Sharing eligible controls creates dependence between comparisons. Nonconcurrent borrowing is a separate design choice.
Published example
RECOVERY Collaborative Group (2021), Dexamethasone in Hospitalized Patients with Covid-19
Read this comparison within the larger RECOVERY platform. Identify participants eligible for the dexamethasone comparison and its usual-care control group rather than treating every platform participant as a control.
This publication illustrates a study design, not an endorsement of every method or a reproduction of its results. Follow its protocol, supplement and update history when studying the example.
Hypothetical scenario
A research network wants a continuing trial in which new treatments can enter as evidence and readiness evolve.
- Platform trial overview: Define the master question, governance and prospective registration with arm-specific amendments.
- Cohort and arm eligibility: Identify which participants are eligible for each active arm at entry.
- Arm lifecycle and allocation: Specify arm entry, allocation, monitoring and closure rules while retaining follow-up.
- Endpoints estimands and comparisons: Define each comparison estimand, outcome and claim family.
- Interim decisions and governance: Set independent review responsibilities and protect interim information.
- Simulations and sample-size scenarios: Simulate arm lifecycles, eligibility changes, calendar trends and control-pool choices.
- Data populations and control pools: Construct eligible concurrent control sets and document any nonconcurrent borrowing separately.
- Comparison analysis plan: Analyze each planned comparison with compatible inference and report arm availability and calendar epochs.
Deliver a populated protocol, decision log, data specification, and planned outputs. Enter numerical findings only after analysis and verification. Keep decisions made before seeing results distinguishable from later amendments.
Sources
- CONSORT 2025: reporting randomized trials
- SPIRIT 2025: randomized trial protocols
- ICH E9(R1): estimands and sensitivity analysis (2019)
- FDA: Master Protocols for Drug and Biological Product Development (June 2026 draft; not for implementation)
- FDA: Adaptive Designs for Clinical Trials of Drugs and Biologics (2019)
- WHO: clinical trials and prospective registration
- ISRCTN: what the clinical study registry records
- ClinicalTrials.gov: about the registry
Source check: 2026-09-17. Record the version of each reporting or appraisal tool used in your actual protocol.
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