FDA Refuse-to-File Letters for NDAs and BLAs: Common Deficiencies and Resubmission Strategies

FDA refuse-to-file letters for NDAs and BLAs: common deficiencies and how sponsors resolved them

A refuse-to-file (RTF) letter is FDA's threshold decision that an NDA or BLA is too incomplete for a meaningful substantive review. It is not a judgment that the product cannot be approved. CBER describes it as a judgment that omissions or inadequacies make an application too incomplete for prompt, meaningful review, not a final judgment on scientific or medical merit ²³⁸. CDER's guidance Refuse to File: NDA and BLA Submissions to CDER frames the test as whether the application is complete on its face and sufficiently complete for substantive review, with the filing decision generally made within 60 days of receipt ³¹³²⁸⁰.

RTFs are not rare events. In October 2025, FDA reported that more than 200 applications had received RTF notifications over the preceding ten years, and that new molecular entity applications receiving an RTF waited an average of 426 days before resubmission ¹⁰⁷. FDA also published the internal filing-review checklists its staff use to decide whether an application is complete or subject to RTF, with the stated aim of reducing incomplete submissions ³⁴¹.

Key takeaways

• The deficiencies that recur in FDA filing reviews and company disclosures fall into five groups: an inadequate evidentiary package for effectiveness, gaps in clinical pharmacology or nonclinical characterization, CMC and facility readiness problems, unreviewable organization or data format, and administrative or regulatory defects.
• CMC is the best-documented single category in Drugs@FDA filing reviews. The usual problems are facilities not ready for inspection, missing master production records, and stability data too short for the proposed shelf life ^450452455530.
• Successful resubmissions usually close the specific gap FDA named: new stability data, inspection-ready facilities, bridging toxicokinetic studies, or a restructured indication. Resubmissions that argue around the deficiency without new data have a weaker track record. One example is filing over protest on the same clinical evidence ⁸²⁸³.
• Sponsors have three standard routes after an RTF: amend and resubmit; request an informal conference (a Type A meeting at CDER) within 30 days and then file over protest; or end the program. In exceptional cases, such as ALKS 5461, clarifying the existing submission has led FDA to rescind an RTF.

Legal basis

For NDAs, 21 CFR 314.101(d) allows FDA to refuse to file an application that lacks a completed form, is not in the required form, is incomplete on its face, lacks an adequate environmental assessment or categorical exclusion claim, lacks accurate English translations, or lacks required statements on nonclinical GLP compliance, IRB compliance, or informed consent ²⁰⁰²⁰¹. FDA may also refuse to file duplicative applications, or a 505(b)(2) application for a duplicate of a listed drug that is eligible for approval under 505(j) ²⁰¹. Paragraph (e) covers regulatory bars: the product is subject to licensing under the PHS Act, or a statutory provision bars submission of the 505(b)(2) application ²⁰².

For BLAs, 21 CFR Part 601 provides that an application is not considered filed until FDA has received all pertinent information and data. That includes safety, purity, and potency data, manufacturing and stability information, labeling, facility information, financial disclosure, and an environmental assessment or categorical exclusion ¹⁹⁵.

CDER's MAPP directs staff to refuse to file an application that is incomplete, has deficiencies that cannot readily be corrected or have not been corrected, or is inconsistent with regulatory practice. The MAPP's example of the last point is a 505(b)(2) submission that should have been a 505(j) application ²³⁹. CDER may also refuse to file for inaccessible electronic data or noncompliance with electronic submission requirements ²⁴⁰.

The most common RTF deficiencies

1. Inadequate evidence of effectiveness in the submitted package

The guidance gives one clinical example directly. An application may be incomplete if it relies on a single adequate and well-controlled trial after FDA and the sponsor agreed at an end-of-phase-2 meeting that more than one was needed. FDA may also file the adequately supported portion of an application for one indication and refuse the portion for another indication ³¹⁴.

Documented cases:

• Translarna (ataluren), PTC Therapeutics. The first RTF was based on a single Phase 2b trial that missed statistical significance on its prespecified analysis ⁷⁸. The second RTF, dated February 22, 2016, said the NDA was not sufficiently complete for review. FDA viewed both the Phase 2b and Phase 3 ACT DMD trials as negative, objected to a proposed post hoc adjustment that excluded data from a majority of enrolled patients, and cited inadequate abuse-potential information ⁸¹.
• Forzinity (elamipretide), NDA 215244. FDA found that the original application lacked a single adequate and well-controlled trial capable of establishing effectiveness. Among other issues, FDA pointed to failed primary endpoints in the randomized portion of SPIBA-201 and difficulty interpreting uncontrolled or effort-dependent outcomes ¹⁵¹¹⁵².
• ALKS 5461, Alkermes. The company reported that FDA saw insufficient evidence of overall effectiveness and an inadequate bridging strategy. FDA itself made no public statement about the pending NDA ⁵⁸⁵.
• ChiRhoStim (synthetic human secretin), NDA 021256. The original NDA contained insufficient clinical data for review ¹⁵⁶.
• Hectorol Injection, NDA 21-027. The RTF letter cited deficiencies in the clinical studies and the supporting PK data, including potentially inadequate or absent controls and variable washout periods ³⁹.

2. Clinical pharmacology, biopharmaceutics, and nonclinical gaps

CDER's clinical pharmacology filing checklist asks, among other things, whether the application includes required PK studies or a waiver request, comparative bioavailability data for 505(b)(2) applications, and data supporting the validity of the analytical assays ²⁴¹. These gaps can lead to RTF when they prevent FDA from writing dosing or interaction labeling.

• Zeposia (ozanimod). FDA refused to file on February 23, 2018. RP112273 (CC112273), a predominant active metabolite, had not been adequately characterized ⁵⁶¹. Plasma stability of the metabolite was established only to 136 days, yet retained samples had been analyzed outside that window, some more than a year after collection. FDA therefore considered the clinical PK inadequately characterized for dosing and drug-interaction labeling ⁵⁶³. On the nonclinical side, the toxicokinetic data were not enough to show adequate metabolite exposure across the species and regimens used in the pivotal toxicology studies ⁵⁶⁴.
• Forzinity. The same RTF letter also cited undefined dataset variables, missing PK files and reports, and major metabolites whose in vitro interactions had not been characterized ¹⁵².
• 505(b)(2) biowaivers. For Pemetrexed Injection (NDA 208419), the active and inactive ingredients differed markedly from those of the listed drug (Alimta), and FDA did not grant the requested biowaiver ¹⁴⁹. For Glycopyrrolate Injection (NDA 214919), FDA found insufficient data to support a biowaiver, alongside CMC, clinical, and nonclinical issues ¹⁴⁵¹⁴⁶.
• ReadyPrep CHG, NDA 207964. The application was not filed mainly because of clinical and nonclinical issues. FDA cited an unaddressed nonclinical safety issue and shortcomings in the published literature offered to support safety ⁴³⁴⁴⁴⁵.
• Abuse potential. The guidance lists failure to submit an abuse-potential assessment as an RTF example when one is needed to inform scheduling and labeling. This applies, for example, to CNS-active drugs, drugs that resemble drugs with known abuse potential, and drugs with psychoactive effects ⁴⁶⁹.

3. CMC and facility readiness

Drugs@FDA filing reviews document this category more often than any other. The recurring patterns are:

The CMC meetings guidance lists the issues sponsors should settle before submission. These include differences between the phase 3 and to-be-marketed product (and any bridging studies needed), adequacy of stability data, coordination with DMF holders, and facility readiness for inspection ³¹⁵.

4. Unreviewable organization, integrated summaries, and electronic data

The guidance treats a materially deficient or poorly organized application as an RTF ground when it prevents timely, efficient multidisciplinary review ³¹⁶. It also covers electronic submissions. An application can be refused for content not submitted in the required electronic format, or for organization, file format, coding, or formatting problems specified in applicable guidance ⁴⁹⁵.

• Fluorodopa F18, NDA 200655. The RTF deficiencies were the missing Integrated Summaries of Efficacy and Safety (ISE and ISS). The original NDA also omitted both pivotal studies, which the reviewer described as a major filing deficiency even though it was not listed in the letter ³⁷³⁸.
• Lidopel (lidocaine/epinephrine), NDA 21-486. FDA sent an RTF after major flaws remained uncorrected. The integrated safety summary could not be reviewed, and the electronic database was hard to use, with inaccurate or poorly defined entries ⁴²⁰.
• Xyzal, NDA 022064. A reviewer recommended RTF because the required ISE was missing. The row documents a recommendation, not an issued letter ⁴¹⁸.

5. Administrative and regulatory defects

These are the 314.101(d) items: forms, translations, environmental assessments, and compliance statements ²⁰⁰. Financial disclosure, or the due-diligence certification when disclosure cannot be obtained, is also a filing requirement ³¹⁷. The RTF letter for Ximino (minocycline), NDA 201922, cited missing signed debarment certification and financial disclosure forms ⁵⁰. For NME NDAs and original BLAs reviewed under the PDUFA Program, minor components that were agreed for late submission must arrive within 30 calendar days. If they do not, the application is considered incomplete and may be refused ²⁹⁷⁴⁹⁶.

How sponsors resolved RTFs

Procedural routes

• Amend and resubmit. The resubmitted application gets a new filing determination ²⁷⁶. At CDER, its review designation (priority or standard) is based on the information available at resubmission ²⁵².
• Informal conference, then file over protest. For an NDA refused under 314.101(d), the applicant may request an informal conference in writing within 30 days of the RTF notification ²⁰³. CDER provides the conference when a Type A meeting is requested within that window ²⁵³. After the conference, the applicant may ask FDA to file the application over protest, with or without corrective amendments. No duplicate submission is required, and the NDA filing date becomes 60 days after receipt of the conference request ²⁷⁶. Refusals under 314.101(e) can only be resolved by amending and resubmitting ²⁰³.
• CBER timelines. CBER's RTF letter lists the deficiencies and the file-over-protest option ²⁵⁰. The applicant may request a meeting within 30 days of the letter and request filing over protest within 30 days after that meeting ².
• User fees. Under PDUFA VII, FDA refunds 75% of the application fee for an application refused for filing. A later resubmission generally owes a new full application fee unless a waiver or reduction applies; sponsors filing over protest should confirm fee treatment, including any refund already issued, with FDA ²⁸².

Case outcomes

Patterns in what worked

1. Data-gap RTFs were closed with new data, not argument. Zeposia is the clearest case. FDA named two specific gaps (metabolite PK and TK coverage), and the resubmission answered each one with new stability, drug-interaction, and bridging toxicology data. FDA's clinical pharmacology reviewers then accepted the application for review ^565567569.
2. CMC RTFs had the shortest path back. Inbrija's resubmission came about five months after the original June 27, 2017 submission and was accepted roughly two months later ^530531113. Liptruzet and cyclophosphamide were also cleared once facilities were inspection-ready, master production records were filed, and stability data covered the proposed shelf life ^4514749.
3. Filing over protest on contested efficacy evidence led to a CRL in the documented case. PTC's filing over protest of Translarna got a standard review but ended in a complete response ⁸²⁸³. Filing over protest makes FDA review the application as submitted. It does not fix a weak evidentiary package.
4. Clarification can reverse an RTF. ALKS 5461 shows that an RTF based on FDA misreading what the submission contained can be rescinded without a new submission or new data ¹¹¹¹¹².
5. Narrowing scope is a legitimate fix. FDA can file part of an application and refuse another part ³¹⁴, and the ChiRhoStim resubmission dropped a proposed indication ¹⁵⁷.
6. A partial fix can leave the deficiency in place. The Fluorodopa F18 resubmission still lacked the ISE and ISS that the RTF letter had named ¹⁵. Lidopel's follow-up submission lacked the materials FDA needed to treat it as a complete RTF response, so FDA handled it as a minor amendment ⁴⁰.

Prevention: what FDA says reduces RTF risk

• Use pre-NDA and pre-BLA meetings to raise significant clinical, safety, and manufacturing issues before submission, and submit a complete, readable, well-organized application ³¹⁸³¹⁹.
• Document any presubmission agreement on late minor components, and deliver those components within 30 days ²⁹⁷.
• Before submission, settle the CMC topics in the CMC meetings guidance: phase 3 to commercial bridging, stability, DMF coordination, and inspection readiness ³¹⁵.
• For drugs with circulating active metabolites, confirm bioanalytical stability windows and nonclinical exposure coverage before locking the PK package. The Zeposia RTF turned on both points ⁵⁶³⁵⁶⁴.
• Run the submission against FDA's published filing-review checklists ³⁴¹. Expect the review division to raise easily correctable deficiencies during the filing period. CDER notes, however, that offering a chance to correct does not extend the day-60 deadline, and that numerous minor deficiencies can themselves warrant an RTF ²⁴³.