Fast Track, Breakthrough Therapy, RMAT, and Priority Review: What Each Designation Actually Changes About FDA Review

Selecting the right FDA expedited designation — or combination of designations — is one of the earliest and most consequential strategic decisions a regulatory team makes. Each program carries distinct eligibility criteria, timing requirements, and procedural benefits, and misunderstanding the differences can mean missed opportunities for earlier agency engagement, suboptimal meeting frequency, or a review timeline that does not reflect the product's actual development profile.

The analysis below examines all four major expedited programs — Fast Track, Breakthrough Therapy, RMAT, and Priority Review — covering where each designation attaches in the development lifecycle, what evidentiary threshold it requires, and precisely which FDA review mechanics it triggers in practice.

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Fast Track, Breakthrough Therapy, RMAT, and Priority Review: what each designation actually changes about FDA review

All four programs sit under one FDA policy framework: the guidance Expedited Programs for Serious Conditions — Drugs and Biologics. They exist to bring therapies for a serious or life-threatening condition to patients sooner, on the principle that a product should be available "as soon as it can be concluded that the therapies' benefits justify their risks," weighed against the seriousness of the disease and the availability of alternatives 32. That shared purpose is where the similarity ends. Each designation attaches at a different point in the lifecycle, rests on a different evidentiary threshold, and buys a different set of concrete review mechanics. The distinctions matter, because the label a sponsor secures determines how early FDA engages, how the application is assembled, and how fast the review clock runs.

A useful mental model: Fast Track, Breakthrough Therapy, and RMAT are development-phase designations that change how FDA interacts with a program before the marketing application arrives. Priority Review is a review-phase designation that changes the clock once the NDA/BLA is filed. They are not mutually exclusive, and a single product commonly carries more than one.

The common threshold: a serious condition and an unmet need

FDA reads "serious condition" as a serious or life-threatening condition, and frames all of these programs as tools for addressing unmet medical need in that setting 321. What separates the programs is the strength and type of evidence each one demands, and what the agency gives back in return.

Fast Track

What it is. Fast Track is for a drug or biologic intended to treat a serious or life-threatening condition that demonstrates the potential to address an unmet medical need 13. The evidentiary bar is the lowest of the group: "potential," which can be supported by nonclinical or early data, rather than demonstrated clinical superiority.

What it changes in practice 13:

  • More frequent meetings and closer early communication with FDA about the development plan.
  • Written communication from FDA, alongside interactive communication, aimed at keeping development efficient.
  • Eligibility for Accelerated Approval and Priority Review, if those programs' separate criteria are also met.
  • Rolling review of the marketing application, meaning FDA can review completed portions of the NDA/BLA as they are submitted rather than waiting for the full package.

Timing and mechanics. A sponsor requests Fast Track by submitting a request with supporting documentation for the product and its proposed use; FDA then has 60 days to decide whether the designation criteria are met 1. Because it can be granted early and on modest evidence, Fast Track is often the first designation a program obtains.

Breakthrough Therapy

What it is. Breakthrough Therapy is for a drug intended to treat a serious or life-threatening condition where preliminary clinical evidence indicates the drug may demonstrate substantial improvement over available therapy on one or more clinically significant endpoints 24. The key words are "clinical" and "substantial": unlike Fast Track, the threshold requires actual patient data suggesting a meaningful advantage, not just theoretical potential.

What it changes in practice. Breakthrough conveys all Fast Track features, then layers on a substantially more intensive and senior FDA engagement model 2:

  • Intensive FDA guidance on an efficient drug development program, beginning as early as Phase 1 / throughout the IND phase 24.
  • An organizational commitment involving senior managers and experienced review staff, in a collaborative, cross-disciplinary review 24.
  • Assignment of a cross-disciplinary project lead to coordinate the review team and act as scientific liaison to the sponsor 24.
  • Active steps to make trial design and overall development as efficient as practicable 24, with frequent meetings across development 4.

Timing and mechanics. A sponsor can request Breakthrough designation with an original IND or in an IND amendment, and FDA also entertains requests for preliminary advice on whether a formal request is appropriate 4. The practical value is not a faster clock but earlier, higher-level, more hands-on FDA involvement that can compress the development timeline itself.

Regenerative Medicine Advanced Therapy (RMAT)

What it is. RMAT is the cell-and-gene-therapy analogue of Breakthrough, created by the 21st Century Cures Act. "Regenerative medicine therapies" include cell therapies, therapeutic tissue-engineering products, human cell and tissue products, and combination products using such therapies, other than those regulated solely under section 361 of the PHS Act and 21 CFR part 1271 25. FDA also reads the category to cover human gene therapy products, genetically modified cells with a sustained effect on cells or tissues, xenogeneic cell products, and both allogeneic and autologous cell therapies; unmodified microorganisms do not qualify 25.

The critical eligibility difference. To qualify, the therapy must be intended to treat, modify, reverse, or cure a serious condition 14, and there must be preliminary clinical evidence that it has the potential to address an unmet medical need 22. Note what is absent: unlike Breakthrough Therapy, RMAT does not require evidence of substantial improvement over existing therapies 4. That lower clinical bar makes RMAT easier to obtain than Breakthrough while still delivering Breakthrough-level engagement.

What it changes in practice. RMAT carries the Breakthrough-type benefits and adds regenerative-medicine-specific features:

  • Frequent meetings throughout development, including critical IND milestone meetings, timely advice and interactive communication, senior-manager involvement, and a cross-disciplinary project lead 4.
  • Early interaction with CBER's Office of Therapeutic Products (OTP), and encouragement to request an "Initial Comprehensive Meeting" that walks through the development program, planned clinical trials, and manufacturing strategy 2214.
  • A product holding both RMAT and Breakthrough is treated as a single designation for meeting-count purposes 14.

The accelerated-approval hook. RMAT's most distinctive feature is its statutory tie to Accelerated Approval. The Cures Act provisions let an RMAT be considered for accelerated approval based on surrogate or intermediate clinical endpoints reasonably likely to predict clinical benefit 22272829. As with any accelerated approval, the sponsor must complete post-approval confirmatory work to verify clinical benefit, and the indication may be withdrawn if that benefit is not verified or the trials are not pursued with due diligence 27.

Priority Review

What it is. Priority Review applies to an application for a product that would provide a significant improvement in the safety or effectiveness of the treatment, diagnosis, or prevention of a serious condition 3. It is the only one of the four that is not a development-phase tool.

When it attaches. The designation is tied to the NDA/BLA submission and filing process, not granted during earlier development 3721. FDA assigns a priority or standard classification to the application itself.

What it changes in practice: the clock. This is the concrete difference. Under PDUFA goals, an original NDA/BLA in priority review carries a 6-month goal, versus a 10-month goal for standard review 15171819. The clock-start convention matters for interpreting those numbers: for most submissions the clock runs from FDA's receipt of the application, but for new molecular entity (NME) NDAs and original BLAs the PDUFA clock begins after the 60-day filing period 15171819. In practice that means a priority NME review targets roughly two months after filing what a standard review would take four months longer to reach, so Priority Review compresses the back end of the timeline by about four months. It does not change the evidentiary standard for approval, only the pace of the review.

How they fit together

The programs are designed to stack. A serious-disease program will often obtain Fast Track early on the strength of potential, upgrade to Breakthrough (or RMAT, for regenerative-medicine products) once preliminary clinical data show a substantial improvement or an unmet-need signal, and then receive Priority Review when the marketing application is filed, so the intensive development-phase engagement is followed by an accelerated review clock. Fast Track and Breakthrough/RMAT govern how FDA works with you before submission; Priority Review governs how fast FDA acts after submission. Accelerated Approval, referenced throughout, is a separate mechanism that changes the evidentiary basis for approval (allowing reliance on a surrogate endpoint reasonably likely to predict clinical benefit) rather than the interaction model or the clock 30.

One practical caveat for planning: designation is not permanent or unconditional. FDA can rescind a Breakthrough or RMAT designation if a product no longer meets the criteria as data mature, and none of these programs lowers the substantial-evidence standard for approval. They change the tempo and intensity of engagement and review, not the ultimate benefit-risk bar.