FDA Milestone Meetings

Over a development program, the conversations you have with FDA are some of the highest-value and scarcest resources you have. They are not casual check-ins — the formal meetings between a sponsor and FDA are well-defined and run on fixed procedural clocks.

The same six meeting types apply across the Center for Drug Evaluation and Research (CDER) and the Center for Biologics Evaluation and Research (CBER), covering small molecules, therapeutic proteins, vaccines, and cell and gene therapies alike. For a cell or gene therapy program, every one of these meetings runs through CBER’s Office of Therapeutic Products (OTP) — the office you’ll work with from your first early conversation through licensure.

This explainer walks the full set of meeting milestones: the six meeting types and what each is for, where each falls in development, how to choose the right one, the timelines that govern each, and the specific considerations for a cell or gene therapy program.

01 · THE LANDSCAPE

Meetings are not a box-checking exercise

FDA offers a structured set of formal meetings for drugs and biologics, each matched to a stage of development and each carrying its own request procedure, page and question limits, and goal dates. They are defined in FDA’s guidance Formal Meetings Between the FDA and Sponsors or Applicants of PDUFA Products. The meeting types and their timelines are consistent regardless of which center reviews your product, but there can still be considerable nuance in your experience with the review team.

What differs is who sits across the table. CDER reviews most drugs and some biologics; CBER reviews vaccines, blood products, and cell, gene, and tissue therapies. If you are developing a cell or gene therapy, your counterparty is OTP, and the team you meet at your earliest interaction is broadly the same team that will handle your pre-IND, your IND, and ultimately your BLA. Regardless of center, you’ll usually work with the same review team from INTERACT to BLA or NDA, and each meeting is an opportunity to build alignment ahead of a successful marketing submission.

CDER and CBER may look similar on the surface, but your interactions with each can feel very different. CDER oversees a large, diverse portfolio, much of it with well-established development pathways that let the center apply consistent, rigorous standards and give sponsors a predictable road to approval. CBER, by contrast, often works at the frontier of cell and gene therapies that are highly nuanced, that rarely replicate cleanly from one program to the next, and that are sometimes tailored to a single patient (n=1). Such programs call for a more collaborative, interactive approach that meets each program where it is. Both reflect the same commitment to patient safety, simply calibrated to the maturity and individuality of the products they regulate.

For products that need a companion diagnostic or a delivery device, one other party can join the table. The Center for Devices and Radiological Health (CDRH) reviews in vitro diagnostics (IVDs), so a program that includes a companion diagnostic brings CDRH into the review alongside CDER or CBER. Meetings only for the diagnostic follow CDRH’s own guidelines for meeting with device sponsors — a separate process with its own timelines and meeting types.

ONE REVIEW TEAM, MANY CONVERSATIONS

For a cell or gene therapy, INTERACT, pre-IND, end-of-phase, and pre-BLA meetings all run through OTP. The framework is shared with every drug and biologic across CDER and CBER, but the reviewers, expectations, and institutional memory are specific to your review team, so consistency across your meetings matters as much as the content of any single one.

02 · THE SIX MEETING TYPES

The PDUFA meeting types, end to end

There are six formal meeting types for drug and biological products. Five are tied to where you are in development or to a specific decision point; one — Type C — is the catch-all for everything else. Knowing the boundaries between them is what keeps a request from being denied or quietly converted to a different type.

Meeting	What it’s for	Typical trigger
Type A	Getting a stalled program moving again, or addressing an important safety issue	Clinical hold, dispute resolution, post-action meeting within 3 months of a complete response letter, or after a refuse-to-file letter
Type B	The recognized milestone meetings of a program	Pre-IND, pre-BLA/pre-NDA, pre-EUA, and the comprehensive program meeting for a breakthrough- or RMAT-designated product
Type B (EOP)	Confirming readiness to advance between phases	Certain end-of-phase 1 meetings and end-of-phase 2 (pre-phase 3) meetings
Type C	Any other development or review question	A targeted scientific or CMC question; early consultation on a novel surrogate-endpoint biomarker
Type D	A narrow, focused issue needing quick input	One or two focused topics, a few questions, no more than three disciplines involved
INTERACT	Early advice on a novel challenge before the pre-IND	A genuinely novel product or platform with an IND-enabling question that existing guidance doesn’t answer, most common for cell and gene therapies

Each meeting can run in different formats: in-person face-to-face (now hybrid, with a virtual component), virtual face-to-face, teleconference, or Written Response Only (WRO), in which FDA simply sends written answers in lieu of a live discussion.

There is almost always value in meeting with the review team, but a WRO still delivers the real payoff of a milestone meeting: detailed FDA feedback. You may request a format for any meeting type, but FDA defaults to WRO when there’s no strong reason to meet, so including your reasoning helps support the request.

ONE CHANCE AT EACH MILESTONE

Although individual offices can be more flexible, FDA’s guidance outlines that typically only one Type B meeting is granted per milestone application (e.g., IND, BLA/NDA). With FDA as the gatekeeper for your product’s approval, teams must maximize each interaction to ensure alignment. The strategic question is rarely “should we meet,” but rather “is it the right time to get FDA feedback.” The opportunity for more interactions via Fast Track, Breakthrough Therapy, and Regenerative Medicine Advanced Therapy (RMAT) is one reason those programs can be valuable.

03 · THE TIMELINE

Where each meeting falls in development

The meeting types map onto the arc of a program. The sequence below is the common shape rather than a fixed schedule — programs iterate, phases overlap, and for cell and gene therapies the same question can resurface as the process changes. Even so, it shows where each rung naturally sits.

Stage	Meeting	Focus for a CGT program
Early / IND-enabling	INTERACT	A novel platform or manufacturing challenge with no clear guidance, before the pre-IND; common especially for cell and gene therapies
Pre-IND	Type B (pre-IND)	IND-enabling toxicology, CMC, and first-in-human trial design: the package that precedes your IND
Substantive milestone: IND	Submission for FDA action, not a meeting	The IND allows you to initiate clinical studies in the US
End of Phase 1/2	Type B (EOP)	Readiness to advance: dose, preliminary activity, and the plan for the next phase
Pre-BLA/NDA	Type B (pre-BLA/NDA)	Alignment ahead of the marketing application, before submission
Substantive milestone: NDA/BLA	Submission for FDA action, not a meeting	The marketing application allows you to market your product in the US
Across development	Type C / Type D	Targeted CMC, comparability, potency-assay, or design questions as they arise
After an adverse action	Type A or Type B	Resolving a clinical hold or a complete response letter, depending on timing

INTERACT and the pre-IND are the two early milestones most cell and gene therapy programs use, and they’re easy to confuse. FDA routinely accepts pre-IND requests, but INTERACT is only for programs at a very specific stage and rejects a high proportion of requests. Use INTERACT to de-risk the question that would otherwise stall you — definitive pharmacology studies, say — then bring a cleaner, more complete program to the pre-IND.

04 · CHOOSING THE RIGHT MEETING

How to pick the right meeting type

Most of the time the right meeting is obvious from where you are. The decision only gets hard at the margins: between a Type C and a Type D, or between an INTERACT and a pre-IND. A simple set of questions resolves almost every case:

• Is the program stalled, or is there an important safety issue — a clinical hold, a dispute, or a post-action meeting soon after a complete response letter? That’s a Type A.
• Are you at a recognized milestone (pre-IND, end of a phase, pre-BLA), or do you hold breakthrough or RMAT designation? That’s a Type B (or a Type B (EOP) at a phase boundary).
• Do you have a genuinely novel, IND-enabling question that no guidance answers, with your definitive nonclinical safety studies not yet locked? That’s an INTERACT.
• Is your question narrow — one or two focused topics, a handful of questions, no more than three disciplines? That’s a Type D.
• None of the above — a substantive scientific or CMC question, or more than a Type D can hold? That’s a Type C.

The Type C / Type D line is the one sponsors misjudge most. Type D exists for speed on a tight question and reaches you faster, but it’s capped: no more than two focused topics, and no more than three disciplines or divisions. Pack in more than that — or a single highly complex issue with many sub-parts — and you have a Type C, whether you labeled it that way or not.

WHEN FDA CONVERTS YOUR MEETING

If you request a Type D that is too broad, FDA will tell you it is converting the request to the appropriate type (typically Type C) rather than denying it; you can accept the conversion or withdraw. The same logic runs the other way: stacking several Type D requests in quick succession instead of a single Type C is discouraged. Choosing the right type up front avoids a reset of the clock.

05 · THE CLOCKS

What to expect after you ask

Every meeting type runs on a published set of goal dates: how fast FDA tells you yes or no, when your meeting package is due, and how soon the meeting happens. The headline numbers:

Meeting	FDA responds	Package due	Meeting held within	Minutes
Type A	14 days	With the request	30 days	30 days after
Type B	21 days	30 days before	60 days	30 days after
Type B (EOP)	14 days	50 days before	70 days	30 days after
Type C	21 days	47 days before	75 days	30 days after
Type D	14 days	With the request	50 days	30 days after
INTERACT	21 days	With the request	75 days	Annotated responses, 30 days after

All days are calendar days from FDA’s receipt of the request. For Type B (EOP), Type C, Type D, and INTERACT, FDA sends preliminary written responses no later than five days before the meeting, and you respond within three days saying which questions are resolved and which you still want to discuss. A WRO follows the same scheduling clock as a live meeting of its type, and the written response serves as the minutes.

FOR THREE MEETING TYPES, THE PACKAGE IS THE REQUEST

Type A, Type D, and INTERACT packages must travel with the meeting request: there is no second chance to fill gaps before FDA evaluates it. Across all types, keep to no more than ten questions total, and don’t use sub-questions — FDA counts 1a, 1b, 1c as three of your ten. A thin or sprawling package is one of the most common, and most avoidable, reasons a meeting underdelivers.

06 · WHAT’S DIFFERENT FOR CELL & GENE THERAPY

How the ladder plays out at OTP

The meeting types are identical for a cell and gene therapy program, but how you use them is shaped by the nature of the products.

First, INTERACT is an especially high-value interaction for cell and gene therapies. These products are frequently first-in-class, frequently built on platforms with no clear precedent, and the questions that block them — species selection for proof of concept, a manufacturing or comparability strategy, a biodistribution design — are exactly the novel, IND-enabling issues INTERACT was built for. Most CGT programs have at least one such question, which makes them strong INTERACT candidates.

Second, the manufacturing process is highly representative of the product for these biologics, and manufacturing drives more interactions than it would for a small molecule. Because process and product are so interconnected, CMC, comparability, and potency questions recur across development rather than settling early, and those often become Type C or Type D meetings between the milestones. Potency assays in particular take a long time to develop, so early feedback pays off even though the assay isn’t formally required until later.

Third, designation can expand your access to the review team. A product granted Regenerative Medicine Advanced Therapy (RMAT) or breakthrough therapy designation gets a comprehensive, multidisciplinary Type B meeting to discuss the overall program, and isn’t held to the usual “one of each Type B” limit. That’s a meaningful expansion of FDA access for a qualifying CGT program — and a reason to pursue designation on its strategic merits, not just its review-speed benefits.

RMAT AND BREAKTHROUGH CHANGE YOUR MEETING ACCESS

Outside of designated products, FDA generally grants only one of each Type B meeting per application. A breakthrough- or RMAT-designated product earns the comprehensive program meeting plus additional Type B (or Type A) interactions, turning a scarce resource into a more open line to the review team.

07 · BEYOND PDUFA

Adjacent tracks worth knowing

The six meeting types cover investigational and marketing interactions for a specific product, but not every FDA conversation follows this set of milestones. Several adjacent tracks run alongside it, and they matter more as your program matures and your pipeline broadens.

Biosimilars and generics have their own meeting frameworks. CBER and CDER offer a Biosimilar Initial Advisory meeting and Biosimilar Product Development (BPD) Type 1, 2a, 2b, 3, and 4 meetings, plus pre-submission and product-development meetings that follow the same good-meeting-management principles as the product types, with their own goal dates.

A different kind of track exists for qualifying the tools you use in development rather than advancing a specific product. FDA runs three drug development tool (DDT) qualification programs jointly across CDER and CBER: the Biomarker Qualification Program (BQP), the Clinical Outcome Assessment Qualification Program (COAQP), and the Animal Model Qualification Program (AMQP).

For biomarkers specifically, the BQP runs two meeting types of its own: pre-submission meetings (ahead of a Letter of Intent, Qualification Plan, or Full Qualification Package) and debrief meetings after a decision letter. Each is a short, non-binding video or teleconference; requests propose dates within about 60 days, and where a live meeting isn’t feasible FDA may answer in writing. For a cell or gene therapy program, this is the venue to qualify a pharmacodynamic or surrogate-endpoint biomarker for broad reuse — distinct from the product-specific surrogate-endpoint consultation you’d raise as a Type C meeting.

FDA sources & references

• Formal Meetings (PDUFA) Guidance — Formal Meetings Between the FDA and Sponsors or Applicants of PDUFA Products (CDER/CBER), defining the six meeting types, formats, requests, and procedural goals. fda.gov ↗
• SOPP 8101.1 — Regulatory Meetings with Sponsors and Applicants for Drugs and Biological Products (CBER), including BsUFA and GDUFA meeting types. fda.gov ↗
• PDUFA Reauthorization Goals (FY2023–2027) — The negotiated meeting-management goal dates that set the response, scheduling, and package timelines. fda.gov ↗
• SOPP 8101.2 — Scheduling and Documentation of Liaison Meetings with Industry Trade Organizations (CBER). fda.gov ↗
• Qualification Process for Drug Development Tools — CDER/CBER guidance implementing FD&C Act Section 507: the LOI, QP, and FQP stages, contexts of use, and review time frames. fda.gov ↗
• Biomarker Qualification Program — CDER’s BQP: qualification stages, context of use, and how to request pre-submission and debrief meetings. fda.gov ↗
• Regulation & related guidance — 21 CFR 312.47 (EOP and pre-NDA/BLA meetings); Best Practices for Communication Between IND Sponsors and FDA; FD&C Act §507 and the 21st Century Cures Act (drug development tool qualification).

Not sure which FDA meeting you need?

Deffai maps your program onto the meeting milestones, so you ask for the right meeting, at the right time, with a package that earns the feedback you came for.

Johnny Lam, PhD — Head of Regulatory Strategy · Laura Rose, PhD — Cofounder & Chief Regulatory Officer

This document is general educational information about FDA’s formal meeting program for drug and biological products. It is not legal or regulatory advice and does not create an attorney–client or consulting relationship, nor does it substitute for FDA’s guidance documents, regulations, or the PDUFA reauthorization goals. Meeting types, eligibility, and timelines are program-specific and subject to change (the governing formal-meetings guidance is a draft revision), and FDA advice is informal and non-binding. Confirm current FDA procedures before requesting a meeting.