Regulatory Signal: Notice of Decision on a Hearing Request Regarding a Proposal To Refuse To Approve a New Drug Application — NDA 218489 (tradipitant capsules, 85 mg) | Federal Register, March 31, 2026 | Document 2026-06187
On March 31, 2026, the FDA published its Notice of Decision on a Hearing Request Regarding a Proposal To Refuse To Approve a New Drug Application in the Federal Register, bringing a formal close to a multi-year regulatory dispute between Vanda Pharmaceuticals, Inc. and the Center for Drug Evaluation and Research (CDER). The agency upheld its refusal to approve NDA 218489 for TRADIPITANT capsules (85 mg) as a treatment for the symptoms of gastroparesis, and simultaneously denied Vanda's request for a formal evidentiary hearing.
The decision is significant beyond its immediate commercial implications. It illuminates how FDA applies the "genuine and substantial issue of fact" standard when evaluating whether a formal hearing is warranted — a threshold that is far more demanding than many sponsors assume. It also raises a question that cuts to the heart of pharmaceutical development strategy: what does it mean when the same molecule, submitted for two different indications, receives an approval for one and a firm refusal for the other?
For regulatory affairs professionals, clinical development teams, and anyone navigating the NDA process, this case offers a detailed study in where FDA's evidence standards draw hard lines — and what happens when a sponsor pushes back against those lines through every available procedural channel.
Gastroparesis: The Treatment Problem That Has Not Been Solved
Gastroparesis is a chronic condition of delayed gastric emptying in the absence of mechanical obstruction. The stomach does not contract normally, and food moves too slowly into the small intestine. Patients experience persistent nausea, vomiting, early satiety, bloating, and abdominal pain — often for years, frequently severely enough to impair nutrition and quality of life.
The scale of the problem is substantial. Estimates suggest gastroparesis affects between 1.5 and 5 million Americans, with diabetic and idiopathic gastroparesis accounting for the majority of cases. Women are disproportionately affected. The condition is frequently misdiagnosed or underdiagnosed, and the path from symptom onset to confirmed diagnosis can span years.
What makes the gastroparesis treatment landscape genuinely grim from a pharmacological standpoint is the state of approved therapy. Metoclopramide is the only FDA-approved drug specifically indicated for the symptomatic treatment of gastroparesis in the United States — and it carries a black box warning for tardive dyskinesia, a potentially irreversible neurological movement disorder that becomes more likely with prolonged use. FDA generally limits its use to 12 weeks. Domperidone is accessible through FDA's Expanded Access program but has not been approved. Off-label use of other antiemetics, dietary management, and gastric electrical stimulation devices fill the gap inadequately.
This unmet need is the backdrop against which tradipitant's development must be understood. The clinical rationale for an NK-1 receptor antagonist in gastroparesis is not speculative — neurokinin-1 signaling plays a role in nausea and vomiting pathways, and Phase 2 data generated real clinical optimism. The question was always whether that optimism would survive a rigorous Phase 3 trial. As the NDA process ultimately demonstrated, it did not — at least not to FDA's standard.
Tradipitant's Clinical Development Arc: Phase 2 Promise to Phase 3 Failure
Tradipitant is a selective, oral NK-1 (neurokinin-1) receptor antagonist developed by Vanda Pharmaceuticals. In the gastroparesis indication, the proposed regimen was 85 mg capsules taken twice daily. NK-1 receptor antagonists block the binding of substance P, a neuropeptide involved in transmitting nausea and vomiting signals — the same mechanism class used in highly effective antiemetic agents like aprepitant for chemotherapy-induced nausea.
The Phase 2 Signal That Generated Optimism
The foundational clinical evidence for tradipitant in gastroparesis came from a Phase 2 randomized controlled trial published in 2020, enrolling 152 adults across a four-week treatment period. The results were genuinely encouraging: tradipitant demonstrated a statistically significant reduction in nausea severity versus placebo (reduction of 1.2 vs. 0.7 on a standardized scale). In the pre-specified subgroup of patients with both nausea and vomiting at baseline, the effect size was larger — a reduction of 1.4 versus 0.4. These results provided a scientifically credible basis for advancing to Phase 3.
The Phase 2 findings also informed the design of the Phase 3 trial, including the patient population, the primary endpoint selection, and the treatment duration. This is standard practice — Phase 2 data shapes Phase 3 assumptions. The problem is that Phase 2 trials are not powered or controlled at the same level as Phase 3 trials, and what appears statistically significant in a smaller, shorter study does not always replicate at scale.
Phase 3 Study 3301: Where the Evidence Broke Down
Vanda submitted NDA 218489 to FDA on September 18, 2023, relying primarily on Phase 3 Study 3301. The trial enrolled 201 adults and ran for 12 weeks — a meaningful increase in both sample size and duration from Phase 2. The primary endpoint was change from baseline to Week 12 in biweekly average nausea severity, measured in the intent-to-treat (ITT) population.
The ITT population analysis at Week 12 did not show a statistically significant difference between tradipitant and placebo. The primary endpoint was not met. There were also no nominally significant differences between tradipitant and placebo on the multiplicity-controlled secondary endpoints, which had been designed to assess individual signs and symptoms of gastroparesis. The clinical trial had generated the data FDA needed to evaluate the claim — and that data did not support the claim.
FDA issued a Complete Response Letter (CRL) in September 2024, requesting that Vanda conduct additional studies before the application could be approved. The CRL is not a final refusal; it is FDA's mechanism for communicating that the current application cannot be approved as submitted and identifying what additional data would be needed. For Vanda, the CRL framed the problem: the Phase 3 data was not sufficient, and further study was required.
The Regulatory Battle: From CRL to Hearing Denial
Vanda did not accept the CRL as the final word. The company pursued the formal regulatory mechanism available to NDA applicants who dispute FDA's assessment: a request for a formal evidentiary hearing under 21 CFR Part 314, §314.200.
The Procedural Timeline
The sequence of events following the CRL reflects the full exercise of Vanda's available procedural rights:
On January 7, 2025, CDER issued a Notice of Opportunity for Hearing (NOOH), formally proposing to refuse approval of NDA 218489. This notice was published in the Federal Register on January 16, 2025. Vanda submitted its notice of participation and request for a formal evidentiary hearing on January 28, 2025. CDER submitted its Proposed Order denying Vanda's hearing request on July 18, 2025. Vanda submitted its reply to CDER's Proposed Order on September 17, 2025. FDA issued its final decision on March 26, 2026, published in the Federal Register on March 31, 2026 as Document 2026-06187.
From NDA submission to final decision spans roughly two and a half years. The hearing request process alone — from NOOH to final decision — took over 14 months after the CRL was issued.
What Vanda Argued
Vanda's hearing request challenged FDA's analysis on several grounds. The company argued that exposure-response analyses demonstrated significant treatment effects among patients who achieved adequate drug exposure — suggesting that when the drug reached therapeutic concentrations, it worked, and that confounding factors in the ITT analysis obscured a real treatment benefit. Vanda also contended that baseline severity inflation (patients entering the trial at higher symptom severity than typical clinical populations) and rescue medication use by placebo patients distorted the primary endpoint results.
Vanda characterized FDA's Complete Response Letter as "conclusory in nature" and argued that the agency had "generally disregarded the evidence provided." The company also took issue with FDA's suggestion that additional studies should be designed with certain parameters — arguing this advice was "inconsistent with advice of key experts in the field." Repeatedly throughout the process, Vanda requested that FDA convene an Expert Advisory Committee to provide external scientific review of the clinical evidence. FDA declined each request.
Why FDA Denied the Hearing
Under the regulatory standard governing formal hearing requests, FDA is required to convene a hearing only if it determines there is a "genuine and substantial issue of fact" in genuine dispute — a factual disagreement that could not be resolved on the existing record and that would be material to the outcome. This is a demanding standard, and it is deliberately so. The hearing mechanism is not an appeal of scientific disagreement; it is a procedural safeguard for genuine factual disputes that require formal evidentiary resolution.
FDA's position, upheld in its final decision, was that the core issue — whether Study 3301 provided substantial evidence of effectiveness for the proposed indication — was not a matter of factual dispute requiring a formal hearing. The trial missed its pre-specified primary endpoint. Post-hoc analyses and subgroup arguments, however scientifically creative, do not convert a failed primary endpoint into substantial evidence of effectiveness under FDA's standard. Exposure-response analyses that were not pre-specified as primary analyses cannot serve as the basis for approval when the primary analysis is negative. These are not merely procedural positions; they reflect FDA's longstanding and consistent interpretation of what "substantial evidence" means under the FD&C Act.
The denial of the hearing request is FDA's formal statement that Vanda raised no genuine factual issue that would change this calculus. The agency reviewed the arguments, considered Vanda's reply to the Proposed Order, and concluded that the refusal to approve was correct.
What the Hearing Denial Signals About FDA's Evidentiary Standards
The decision against Vanda is worth examining not just for what happened to tradipitant, but for what it reveals about how FDA applies its evidence standards when challenged through the hearing process.
The first point is that FDA does not treat a failed primary endpoint as a starting point for negotiation. The Phase 3 primary endpoint in Study 3301 was pre-specified and agreed upon through the clinical development process. When that endpoint is not met in the ITT analysis, FDA's view is clear: the trial has not generated substantial evidence of effectiveness for the proposed indication. Post-hoc arguments that the drug "really worked" in patients who happened to achieve adequate exposure are scientifically interesting but cannot substitute for a successful pre-specified primary analysis. This is not an arbitrary position — it reflects the core protection against selective reporting and outcome-switching that pre-specified primary endpoints provide.
The second point concerns the "genuine and substantial issue of fact" standard for hearing requests. This standard does not ask whether the sponsor and FDA disagree about the science. Of course they disagree — that is why the hearing is requested. The standard asks whether there is a genuine dispute about a specific fact that would be material to the outcome and that cannot be resolved on the existing record. When the primary endpoint is negative and the scientific question is whether post-hoc analyses should change that conclusion, FDA consistently holds that this is a question of regulatory policy and statutory interpretation — not a factual dispute requiring a hearing. Vanda's arguments were scientific arguments about how to interpret clinical data, not genuine factual disputes in the legal sense that triggers hearing rights.
The third point is procedural: FDA's consistent refusal to convene an Advisory Committee at Vanda's request. FDA is not required to convene advisory committees on demand. The agency has the expertise and authority to make these determinations, and the existence of an advisory committee process does not obligate FDA to use it every time a sponsor requests one. The refusal to convene an advisory committee here is not unusual; it reflects FDA's assessment that the scientific questions presented did not require external expert input beyond what CDER's own reviewers provided.
The NEREUS Paradox: Same Molecule, Different Outcome
The tradipitant story has a dimension that will be referenced in pharmaceutical development discussions for years: on December 30, 2025, just three months before FDA's final refusal of the gastroparesis NDA, the agency approved tradipitant under the brand name NEREUS for a different indication — the prevention of vomiting induced by motion sickness. NEREUS became the first new drug approved for motion sickness in approximately 40 years.
The NEREUS approval was based on two Phase 3 trials, designated "Motion Syros" and "Motion Serifos," which demonstrated statistically significant reductions in vomiting rates: 10.4% to 18.3% with NEREUS versus 37.7% on placebo. Those trials met their pre-specified primary endpoints. The evidence package was sufficient. The approval followed.
This creates what might appear to be a paradox: the same molecule, the same company, regulatory success in one indication and a firm refusal in another. But the paradox dissolves when examined through the correct analytical lens. FDA approvals are indication-specific. The agency does not approve molecules — it approves drug-indication-dose combinations based on the evidence submitted for that specific use. A successful NDA for motion sickness demonstrates that tradipitant reduces vomiting in a controlled provocation environment; it does not establish that tradipitant treats the chronic, multifactorial symptom complex of gastroparesis. The clinical question, the patient population, the endpoint design, and the evidence standard are all distinct.
The NEREUS approval also demonstrates that Vanda's development program was not fundamentally flawed in its clinical design capabilities. The company ran trials that met their endpoints in motion sickness. That makes the Study 3301 failure in gastroparesis a genuine scientific puzzle — either the drug does not work for gastroparesis at the doses and endpoints studied, or the trial design had structural problems that precluded detecting a real effect. Vanda has publicly argued the latter; FDA's assessment is effectively the former. The regulatory apparatus has no mechanism for resolving that underlying scientific disagreement without additional clinical data.
What Comes Next: Options for Vanda, and the State of Gastroparesis Treatment
Following FDA's final decision, Vanda's available paths forward are narrow but not closed. The company has publicly stated its intention to continue advancing tradipitant for gastroparesis and has also indicated interest in developing tradipitant for GLP-1 receptor agonist-induced nausea and vomiting — an indication with rapidly growing commercial relevance given the widespread adoption of GLP-1 drugs for diabetes and obesity management.
For the gastroparesis indication specifically, the primary path to approval now requires new clinical data. This likely means designing and executing an additional Phase 3 trial — or trials — with a protocol that addresses the shortcomings FDA identified, including a primary endpoint that can demonstrate the treatment effect in the ITT population, cleaner control of confounding variables, and a design that does not generate the same post-hoc interpretation problems that Study 3301 created. The advice FDA reportedly provided about study design — advice Vanda publicly disagreed with — is worth taking seriously at this juncture, not because FDA is infallible, but because FDA has signaled what evidence it would need.
Vanda could also pursue federal litigation under the Administrative Procedure Act, challenging FDA's decision as arbitrary or capricious. This is an available avenue but a difficult one — courts give substantial deference to FDA's scientific and regulatory judgments, particularly when the agency's evidentiary standard is well-established and consistently applied.
For gastroparesis patients, the immediate reality has not changed. Metoclopramide with its black box warning remains the only approved option. The tradipitant refusal does not eliminate hope for new therapies, but it delays it and removes what appeared to be the most advanced candidate from the near-term pipeline. Other compounds are in development — but they are earlier stage, and the gastroparesis indication has now accumulated additional evidence of the difficulty in meeting FDA's evidence threshold.
Lessons for Regulatory Affairs Professionals and Clinical Development Teams
The tradipitant NDA story is not a unique tragedy; it is a concentrated illustration of several recurring dynamics in pharmaceutical regulatory affairs that every development team should study carefully.
Pre-Specification Is Not Optional
The single most important lesson from Study 3301 is that pre-specified endpoints are not bureaucratic formalities — they are the contractual structure of the evidence. When FDA and a sponsor agree on a primary endpoint, that agreement defines the evidentiary bar. A drug that fails its pre-specified primary endpoint in the ITT population has not generated substantial evidence of effectiveness, regardless of what post-hoc slicing of the data reveals. Sponsors who rely on exposure-response subgroups or sensitivity analyses to argue for approval after a failed primary analysis will consistently encounter the same wall Vanda encountered. The lesson is not that post-hoc analyses are worthless — they inform future study design — but that they do not substitute for the pre-specified analysis in the current application.
The CRL Is a Second Chance, Not a Final Verdict
FDA's Complete Response Letter is a formal communication that the application cannot be approved as submitted — but it identifies what is needed to make it approvable. Many sponsors read a CRL as a rejection and immediately pivot to dispute mechanisms. In some cases, the dispute mechanism is the correct response — particularly when the sponsor believes FDA has made a legal or factual error. But when the CRL is grounded in a legitimate clinical evidence gap, the more productive path is usually to design and execute the additional studies FDA has requested. The two-and-a-half-year timeline of the tradipitant NDA dispute — including the hearing process — consumed time and resources that could have been applied to a new trial. That is a real cost that development teams should factor into their strategic calculus when deciding how to respond to a CRL.
The Hearing Request Mechanism Has a High Threshold
The formal hearing request process under 21 CFR Part 314 is a legitimate and available tool, but its threshold is higher than many sponsors appreciate. The "genuine and substantial issue of fact" standard is not satisfied by scientific disagreement about how to interpret clinical data. It requires a specific, material factual dispute that could not be resolved on the existing record. Sponsors who use the hearing mechanism primarily as a delaying tactic or as a vehicle to relitigate scientific disagreements are unlikely to succeed, and FDA's consistent application of this standard in cases like Vanda's should put the industry on notice about what the mechanism is and is not designed to accomplish.
Indication Selection and Clinical Design Are Inseparable
The NEREUS approval for motion sickness and the tradipitant refusal for gastroparesis illustrate a fundamental truth in pharmaceutical development: the difficulty of demonstrating efficacy is indication-specific. Motion sickness is a provoked, acute condition with a binary endpoint (vomiting or not) that is highly measurable in controlled settings. Gastroparesis is a chronic, heterogeneous condition with complex symptom measurement, significant placebo response, and substantial patient-to-patient variability. Trial design for gastroparesis is genuinely harder — and the historical failure rate for gastroparesis clinical trials reflects that difficulty. Sponsors entering this therapeutic area need to design for the complexities of the indication, not just the mechanism of the compound.
Regulatory Intelligence About Study Design Matters
One of the most notable elements of Vanda's public posture was its disagreement with FDA's advice about study design — characterizing that advice as "inconsistent with advice of key experts in the field." This disagreement is understandable but strategically risky. FDA's advice about what a future study would need to look like to support approval is the agency's roadmap for what evidence it will accept. Rejecting that advice on the grounds that external experts would disagree does not change the regulatory standard. If Vanda pursues additional clinical development for gastroparesis, aligning its study design with FDA's stated requirements — even if that design is more conservative or more costly than what the company believes is necessary — is the path most likely to result in approval.
Key Takeaways
FDA's Notice of Decision on a Hearing Request Regarding a Proposal To Refuse To Approve NDA 218489 for tradipitant in gastroparesis, published March 31, 2026, closes the current chapter of this regulatory dispute with several clear conclusions:
A Phase 3 trial that misses its pre-specified primary endpoint in the ITT population does not generate substantial evidence of effectiveness, regardless of what secondary or post-hoc analyses suggest. FDA's "genuine and substantial issue of fact" standard for formal hearing requests is demanding and is not satisfied by scientific disagreement about data interpretation. The same molecule can legitimately receive approval for one indication and refusal for another when the evidence packages are structurally different. Gastroparesis remains a severely underserved therapeutic area with one approved treatment that carries a serious safety limitation, and the tradipitant refusal leaves that gap unaddressed. Sponsors facing a CRL grounded in clinical evidence deficiencies should carefully weigh the strategic costs of prolonged dispute processes against the cost of designing and executing the additional studies FDA has requested.
For the gastroparesis patient community, this decision is a setback. For the regulatory affairs profession, it is a case study in the disciplined application of evidence standards — and a reminder that FDA's requirements exist not to impede development but to ensure that the drugs approved for clinical use actually work for the patients who take them.
Citation-Ready Summary: Key Facts for Reference
On March 31, 2026, FDA published Document 2026-06187 in the Federal Register — a Notice of Decision on a Hearing Request Regarding a Proposal To Refuse To Approve a New Drug Application — upholding CDER's refusal to approve NDA 218489 for TRADIPITANT capsules (85 mg, twice daily) for the treatment of symptoms of gastroparesis, and denying Vanda Pharmaceuticals, Inc.'s request for a formal evidentiary hearing.
The refusal was based on Phase 3 Study 3301's failure to demonstrate a statistically significant difference between tradipitant and placebo on the primary endpoint (change from baseline to Week 12 in biweekly average nausea severity, ITT population) and the absence of nominally significant differences on multiplicity-controlled secondary endpoints.
The hearing denial was issued under 21 CFR Part 314, §314.200, on the grounds that Vanda failed to raise a genuine and substantial issue of fact warranting formal evidentiary proceedings. The same compound (tradipitant) was approved as NEREUS on December 30, 2025, for prevention of vomiting induced by motion sickness, based on separate Phase 3 trials that met their pre-specified primary endpoints.
About the Author
Jared Clark, JD, MBA, PMP, CMQ-OE, CPGP, CFSQA, RAC is the Principal Consultant at Certify Consulting, where he has guided 200+ medical device and pharmaceutical manufacturers through FDA submissions, ISO 13485 certification, and regulatory compliance programs — with a 100% first-time audit pass rate over 8+ years of practice. Jared specializes in QMS strategy, regulatory affairs, and FDA compliance for life sciences companies from startup to enterprise scale.
Last updated: 2026-04-12
Primary source: Federal Register, Document 2026-06187, March 31, 2026. Phase 3 clinical data: Clinical Gastroenterology and Hepatology.
Jared Clark
Principal Consultant, Certify Consulting
Jared Clark is the founder of Certify Consulting, helping organizations achieve and maintain compliance with international standards and regulatory requirements.