Why Meeting Type Matters for a Model-Based Question
A model-informed question can arise at several points in development. A sponsor may need advice about a proposed analysis before a major milestone, clarification of a specific scientific issue, or help resolving a problem that has stalled a program. The modeling method—such as population pharmacokinetics, exposure-response analysis, or physiologically based pharmacokinetic modeling—does not by itself determine the meeting type. The deciding factors are the purpose, development context, urgency, and scope of the discussion.
FDA’s formal meeting categories provide a structure for sponsor or applicant interactions concerning products regulated by the relevant FDA review centers. The categories are not interchangeable routes for asking the same question at different speeds. In particular, a meeting request should fit the applicable category’s purpose; urgency alone does not make a request Type A.
The timelines below are FDA meeting-management goals under the applicable formal-meetings guidance, not statutory guarantees that a particular date will be offered or that a proposed meeting will be granted. Sponsors should check the current guidance and center-specific instructions when preparing a request, since procedures can be updated.
Purpose and Timing of the Main Meeting Types
| Type | When it is generally appropriate | FDA meeting-timing goal | Potential model-related use |
|---|---|---|---|
| Type A | A meeting needed to help resolve a stalled development program or a qualifying urgent issue, such as a clinical hold or a dispute-resolution matter. | Within 30 calendar days of receipt of the request. | Address a critical model-related issue that is preventing progress, when it meets Type A criteria. |
| Type B | A defined development milestone meeting, such as pre-IND, end-of-phase 2/pre-phase 3, or pre-NDA/BLA; other specified Type B meetings are set out in FDA guidance. | Within 60 calendar days of receipt of the request. | Discuss a model-supported development plan at an appropriate milestone. |
| Type C | A formal meeting on a topic that does not fit Type A, Type B, or Type D criteria. | Within 75 calendar days of receipt of the request. | Seek advice on a substantive model question outside a defined Type B milestone. |
| Type D | A focused interaction on a narrow set of issues that does not qualify as Type A or Type B; the scope is limited under FDA’s guidance. | Within 50 calendar days of receipt of the request. | Ask a small number of tightly bounded questions about a specific modeling issue. |
These categories are defined by more than their timing goals. Type A is for a qualifying urgent or stalled-program need, not simply a sponsor’s preference for a faster discussion. Type B is tied to a specified development context. Type C serves as the general category when a formal meeting is appropriate but another category does not fit. Type D is intended to keep a narrow discussion focused; a broad request with several unrelated questions is unlikely to fit that purpose.
The meeting date is not the only timing consideration. A sponsor must prepare a request and, if FDA grants the meeting, provide a meeting package according to the applicable procedures. The package should give reviewers enough context to understand the issue and discuss the questions. The exact submission deadlines and requirements depend on meeting type and current guidance, so sponsors should verify them rather than assume that the meeting-timing goal is also the package deadline.
Matching the Question to the Category
A useful way to classify a proposed interaction is to work from its regulatory purpose toward its model content. First identify the decision or obstacle the sponsor needs to address. Then determine whether the request is for a defined milestone, a qualifying urgent or stalled-program issue, or a focused discussion outside those categories. Only after that should the sponsor decide how to present the model question.
Identify the product’s stage and the decision or milestone that makes agency input useful now.
Ask whether the request meets Type A criteria, concerns a specified Type B milestone, or is sufficiently narrow for Type D. Do not choose a category solely because its timing goal is shorter.
A formal scientific discussion outside the defined Type A, B, and D purposes will generally be considered under Type C.
Explain the intended use, key evidence and assumptions, the decision the analysis is intended to inform, and the specific advice sought.
This sequence keeps the request aligned with the regulatory context. Earlier material on fit-for-purpose modeling emphasizes that model credibility depends on the intended use and consequences of the decision. For a meeting request, those same points help reviewers understand why the model matters; they do not replace the meeting-type criteria.
Worked Example: A Model Question at a Development Milestone
A sponsor plans to request FDA advice at the end of phase 2 about whether its exposure-response analysis, together with the clinical evidence, is adequate to support the proposed phase 3 dose range. The sponsor wants feedback before finalizing the phase 3 plan.
Classification. The principal purpose is an end-of-phase 2/pre-phase 3 discussion, a defined Type B meeting context. The fact that the question concerns an exposure-response model does not make it a Type C meeting.
Timing illustration. If FDA receives a complete Type B meeting request on June 10, the 60-calendar-day meeting goal points to August 9: June 10 plus 60 calendar days is August 9. This is a planning illustration, not a guarantee that FDA will offer that date.
Useful framing. The sponsor should identify the dose decision, summarize the model’s evidence and important assumptions, and ask a focused question—for example, whether the proposed analysis and accompanying evidence are adequate to support the planned dose range. FDA’s feedback may address the evidence needed or concerns about the proposed approach; it should not be described in advance as approval of the model or dose strategy.
Worked Example: A Narrow Question Outside a Milestone
A sponsor is not approaching a formal development milestone. It has one focused question about whether a planned sensitivity analysis adequately addresses a specified uncertainty in a model used to inform a dosing proposal. The issue is not blocking a stalled program, and the sponsor can state it as a narrow discussion.
Classification. If the request does not meet Type A or Type B criteria and fits FDA’s limited scope for Type D, Type D may be appropriate. If the question requires a broader discussion or does not meet Type D scope, Type C is the more suitable category. The sponsor should justify the requested category rather than assume that any one-question request automatically qualifies as Type D.
Timing illustration. For a Type D request received on January 8 in a non-leap year, the 50-calendar-day goal is February 27. January 8 plus 23 days reaches January 31; 27 more days reaches February 27. The goal concerns the meeting timing, not a promised scientific conclusion.
Expected discussion. The sponsor can seek feedback on whether the proposed sensitivity analysis addresses the stated uncertainty and what additional evidence FDA considers important. The request should make clear what the analysis can and cannot establish.
Request Preparation and Expected Feedback
A useful meeting request is concise enough to reveal the decision needed, but complete enough for FDA to classify and assess it. It should identify the product and development context, state the meeting purpose and requested type, and explain why the discussion is needed at that point. It should include a proposed agenda and clear questions, with enough background to show why each question matters. A request should not make reviewers infer the central model issue from a long technical narrative.
For model-informed questions, the supporting material should connect the model to the decision at issue. Depending on the question, that may mean describing the model’s intended use, the evidence supporting it, important assumptions or uncertainties, and the consequences of alternative answers. The objective is not to reproduce an entire analysis in the request. It is to make the scientific question specific enough that reviewers can prepare a useful response.
FDA may grant the request, decline it, or determine that a different format or scope is more appropriate. If the meeting is granted, the agency may provide advice during the discussion or in written responses, and the exchange may identify concerns, evidence gaps, or areas needing clarification. A meeting is an opportunity for scientific and regulatory communication—not a substitute for a complete submission or a guarantee that a proposed analysis, development plan, or regulatory position will be accepted.
Worked Example: When Urgency Does Not Establish Type A
A sponsor hopes to obtain a decision quickly on whether its model can support a dose adjustment in a special population. The program is proceeding on schedule, the issue is not tied to a qualifying dispute or hold, and the request is not for a defined Type B milestone.
Classification. The sponsor’s preferred speed is not enough to make the meeting Type A. It should assess whether the question is narrow enough for Type D; otherwise, a Type C request may be more appropriate. If the same model issue were part of a qualifying situation that had stalled development, the sponsor could explain that circumstance and request Type A consideration, subject to FDA’s criteria.
Reasoning. Meeting type follows purpose and eligibility, not the sponsor’s desired response time. Misclassifying an ordinary scientific question as Type A can weaken the request because it does not explain the qualifying urgent or stalled-program need.
Common Pitfalls, Diagnostics, and Limitations
- Choosing by speed alone. “We need an answer quickly, so this is Type A” confuses a scheduling goal with eligibility. Explain the qualifying urgent or stalled-program circumstance, or select a category that fits the actual purpose.
- Treating all model questions as Type C. A model question at a defined Type B milestone remains a milestone question; the scientific method does not override the meeting context.
- Calling a broad agenda Type D. A request covering multiple unrelated modeling and development decisions may exceed the narrow scope intended for Type D. Reduce the scope or consider whether another category fits.
- Equating a meeting goal with a guaranteed date. The calendar goals help with planning, but they do not guarantee a particular meeting date, approval of every requested question, or the outcome sought.
- Expecting endorsement from discussion. Feedback about a model’s potential usefulness is not, by itself, a binding regulatory decision or assurance of acceptance in a future application.
The classification system also has limits. A category cannot fix a poorly framed scientific question, and a meeting cannot remove uncertainty that the evidence does not resolve. If a model has a restricted applicability domain or depends on consequential assumptions, the sponsor should make those limits explicit. Agency feedback can help clarify concerns and evidence expectations, but the sponsor remains responsible for the analysis and for supporting the eventual regulatory submission.
Check Your Understanding
Answer each question, then compare your reasoning with the solutions.
- A sponsor seeks advice on its dose-selection model at an end-of-phase 2 meeting. What category is the natural starting point, and why?
- A sponsor requests Type A solely because it prefers a meeting within 30 days. What is the error in that reasoning?
- A focused model question outside a milestone may be considered for which categories? What determines the choice?
- If a Type C request is received on March 3, what date corresponds to the 75-calendar-day timing goal in a non-leap year?
Solutions. (1) Type B is the natural starting point because the request concerns the defined end-of-phase 2/pre-phase 3 context; the model method does not change that. (2) The sponsor has treated the timing goal as an eligibility criterion. Type A requires a qualifying urgent or stalled-program purpose, not merely a preference for speed. (3) Type D may fit if the discussion meets its narrow-scope criteria and does not qualify as Type A or B; otherwise Type C is the general category. (4) March 3 plus 75 calendar days is May 17: 28 days remain after March 3 in March, 30 days are in April, and 17 more days reach May 17, for \(28+30+17=75\).