A Complete Response Letter (CRL) is a formal written communication FDA sends to a sponsor when it completes its review of a marketing application — a New Drug Application (NDA), Biologics License Application (BLA), or Abbreviated New Drug Application (ANDA) — and determines the application cannot be approved in its current form.
It is not a rejection in the sense of a closed door, and it is not the same thing as FDA declining to review the application at all. Understanding exactly what a CRL is, when it can be issued, and what it is not, matters for anyone in a research administration or regulatory affairs role tracking a product through FDA review.
What a Complete Response Letter Actually Is
Per FDA’s own description, a CRL is issued directly to an applicant once FDA finishes a full review cycle and concludes it cannot grant approval as submitted. The letter describes the deficiencies FDA identified — in the application itself, in the underlying clinical or nonclinical data, in manufacturing information, or in proposed labeling — that must be satisfactorily resolved before the agency can approve the product. A CRL is issued in lieu of an approval letter at the conclusion of the same review cycle that would otherwise have produced one.
This is the key operational fact: a CRL only happens after FDA has done substantive review. It reflects a scientific or regulatory judgment that the application, as it currently stands, does not support approval — not that FDA refused to look at it.
Where a CRL Fits in the FDA Review Timeline
Under the Prescription Drug User Fee Act (PDUFA) framework that governs most NDA and BLA reviews, FDA first makes a filing determination — typically communicated within 60 days of submission via what industry commonly calls the “Day 74 letter” — confirming the application is complete enough to review substantively. From that filing decision, FDA has a PDUFA goal date (commonly 10 months for a standard review, 6 months for priority review, measured from the filing date) by which it commits to complete its review and take action. A CRL is one of the two possible actions FDA can take at that goal date; the other is approval. There is no third “in-between” outcome at that point in the process — the application is either approved or it receives a CRL.
CRL vs. Refuse-to-File vs. Approval: Three Different FDA Actions
These three terms are frequently confused, but they occur at different points in review and mean materially different things:
| Action | When it occurs | What it means |
|---|---|---|
| Refuse-to-File (RTF) | Early, at the filing-review stage (within roughly 60 days of submission), before substantive review begins | The application is incomplete on its face or has omissions serious enough to prevent a meaningful review — FDA has not evaluated the scientific merits at all |
| Complete Response Letter (CRL) | At the end of a full review cycle, on or near the PDUFA goal date | FDA completed substantive review and determined the application cannot be approved as submitted, due to identified deficiencies |
| Approval | At the end of a full review cycle, on or near the PDUFA goal date | FDA completed substantive review and determined the application meets the standards for approval |
The distinction matters because an RTF says nothing about a product’s scientific viability — it is a completeness gate. A CRL, by contrast, follows a genuine scientific review and typically comes with FDA’s specific reasoning, which is why sponsors and investors treat the two very differently.
What a CRL Typically Contains
FDA states that a CRL usually describes all the deficiencies the agency identified that must be satisfactorily addressed before the application can be approved. Deficiencies generally fall into a few recurring categories:
- Safety or efficacy concerns — the clinical data submitted don’t adequately establish the product is safe and effective for its proposed use, or raise a specific safety signal FDA needs addressed.
- Manufacturing and Chemistry, Manufacturing, and Controls (CMC) deficiencies — issues with the manufacturing process, facility, or product quality controls, sometimes tied to findings from a pre-approval inspection.
- Bioequivalence issues — specific to ANDAs, where the generic product hasn’t been shown to be bioequivalent to the reference listed drug.
- Labeling deficiencies — proposed labeling that FDA considers inaccurate, unsupported by the data, or otherwise unacceptable.
- Risk Evaluation and Mitigation Strategy (REMS) issues — where FDA determines a REMS is needed but the sponsor’s proposal doesn’t adequately mitigate the identified risk.
A single CRL can, and often does, cite deficiencies across more than one of these categories.
What Happens After a Sponsor Receives a CRL
A CRL is not a final rejection — it is the start of a defined regulatory pathway with several possible next steps for the sponsor:
- Resubmit the application. Sponsors can address the cited deficiencies and resubmit. FDA classifies resubmissions by scope: a Class 1 resubmission (minor deficiencies addressable without new studies) carries a 2-month FDA review goal; a Class 2 resubmission (more substantial changes, potentially including new clinical data) carries a 6-month review goal. If FDA determines a sponsor-classified Class 1 resubmission actually contains Class 2-scope content, it can reclassify the resubmission and extend the clock.
- Request a meeting with FDA. Sponsors are generally entitled to request a Type A meeting to discuss the deficiencies and align on a path forward before resubmitting.
- Pursue formal dispute resolution if the sponsor disagrees with FDA’s scientific or regulatory conclusions, following the agency’s formal dispute resolution process.
- Withdraw the application entirely, if the sponsor concludes the deficiencies aren’t practically addressable.
Because CRLs are issued at what would otherwise have been an approval decision, they carry significant weight for a sponsor’s development timeline, and — for publicly traded companies — are typically disclosed as material events.
Public Disclosure of Complete Response Letters
Historically, CRLs were confidential correspondence between FDA and the sponsor, with sponsors themselves choosing whether and how much to disclose. FDA has since moved toward publishing CRLs directly: its openFDA program maintains a public Complete Response Letters database, and FDA has described this shift as part of a broader transparency push, including a real-time release policy for newly issued CRLs. This changes how research administrators, regulatory affairs staff, and analysts can independently verify what deficiencies FDA actually cited, rather than relying solely on a sponsor’s own press release characterization of a CRL’s contents.
Frequently Asked Questions
Does a Complete Response Letter mean a drug will never be approved?
No. A CRL means the application cannot be approved as submitted. Many products that received a CRL are later approved after the sponsor addresses the cited deficiencies and resubmits — though some CRLs do lead to a sponsor withdrawing the application if the deficiencies prove too significant to resolve.
How is a CRL different from a Refuse-to-File letter?
A Refuse-to-File (RTF) letter is issued early, before FDA has substantively reviewed the application’s scientific merits, because the submission itself is incomplete or has serious omissions. A CRL is issued only after a full review cycle, and reflects FDA’s actual scientific and regulatory assessment of the data submitted.
How long does FDA take to respond to a resubmission after a CRL?
It depends on the resubmission’s classification: FDA’s review goal is 2 months for a Class 1 resubmission (minor deficiencies) and 6 months for a Class 2 resubmission (more substantial changes, such as new clinical data), per PDUFA performance goals.
Are Complete Response Letters made public?
Increasingly, yes. FDA’s openFDA program now publishes CRLs associated with NDAs and BLAs, moving away from the historical model in which the letter’s contents were known only to FDA and the sponsor.
What are the most common reasons FDA issues a CRL?
Recurring categories include unresolved safety or efficacy questions in the clinical data, manufacturing or Chemistry-Manufacturing-Controls (CMC) deficiencies (sometimes tied to inspection findings), bioequivalence issues for generic applications, labeling FDA considers unsupported or inaccurate, and inadequate risk mitigation strategies (REMS).
Related CASRAI Resources
For the regulatory filings that precede a CRL decision, see CASRAI’s guide to clinical trial phases and FDA milestones and the dictionary entries for the Investigational Medicinal Product (IMP) and Investigational Medicinal Product Dossier (IMPD). For the inspection findings that sometimes underlie a CRL’s manufacturing deficiencies, see FDA Form 483. For the Good Clinical Practice standard governing the trials that generate the underlying data, see ICH E6(R3). This guide is part of CASRAI’s clinical research administration coverage.
