AzTrials
AzTrials

Eosinophilic EsophagitisPhase 2NCT06851559

A Study in Adult Participants With EoE to Evaluate Vonoprazan 20 mg Compared to Placebo After 12 Weeks and to Evaluate Vonoprazan 20 mg Up to 24 Weeks

A Phase 2 study testing Vonoprazan in people with Eosinophilic Esophagitis, run by Phathom Pharmaceuticals, Inc. at 41 sites in United States.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
Search all trials

Trial summary

The primary objective of this study is to assess the efficacy of vonoprazan 20 mg once daily (QD) compared to placebo QD in the number of participants with a peak eosinophilic histologic response <15 eosinophils per high-power field (eos/hpf) after 12 weeks of therapy. Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
Eosinophilic Esophagitis
What is being tested?
Vonoprazan
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
95 participants
Where
41 sitesUnited States
Study dates
30 Oct 2025to Dec 2026
Phase
Phase 2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • The participant is ≥18 years of age at the time of informed consent signing.
  • In the opinion of the investigator or subinvestigators, the participant is capable of understanding and complying with protocol requirements, including completion and compliance with the electronic diary. The diary must be completed on at least 11 of the last 14 days in the 2 weeks prior to Visit 2 (Day -1).
  • The participant signs and dates a written informed consent form (ICF) and any required privacy authorization prior to the initiation of any study procedures.
  • The participant has a peak eosinophil count of at least 15 eos/hpf [X 400] from at least 2 of the 3 esophageal levels on screening endoscopy as measured in at least 6 biopsies, at least 2 each from the proximal, mid, and distal segments of the esophagus based on central reading.
  • The participant has 4 or more days with dysphagia episodes documented via electronic diary in the 2 weeks prior to Visit 2 (Day -1).
  • The participant must remain on a stable diet for at least 6 weeks prior to the Screening Period and is expected to remain on a stable diet during the course of the study; stable diet is defined as not initiating new elimination diets or reintroducing previously eliminated foods.
  • A female participant of childbearing potential who is or may be sexually active with a non-sterilized male partner agrees to routinely use adequate contraception from the signing of informed consent until 4 weeks after the last dose of study drug.

Who cannot join

  • The participant is on a pure liquid diet.
  • The participant has documented erosive esophagitis at the screening endoscopy.
  • The participant has other known causes of esophageal eosinophilia or either of the following conditions: hypereosinophilic syndrome, or eosinophilic granulomatosis with polyangiitis (Churg-Strauss Syndrome).
  • The participant has a documented diagnosis of eosinophilic gastritis, duodenitis, jejunitis, ileitis, proctitis, or colitis.
  • The participant has endoscopic Barrett's esophagus (>1 cm of columnar-lined esophagus) or dysplastic changes in the esophagus.
  • The participant has a history of achalasia, Crohn's disease, ulcerative colitis, or celiac disease.
Show all 35Show fewer
  • The participant has a known active Helicobacter pylori infection.
  • The participant has any other clinically significant structural conditions affecting the esophagus, including: esophageal varices, viral or fungal infection, and history of radiation therapy, radiofrequency ablation, endoscopic mucosal resection, cryotherapy to the esophagus, caustic or physiochemical trauma (including sclerotherapy or esophageal variceal band ligation), or esophageal surgery.
  • The participant has a history of surgery or non-EoE endoscopic intervention, such as gastric bypass, fundoplication, gastric sleeve, or a history of gastric or duodenal surgery (except endoscopic removal of benign polyps).
  • The participant has gastric ulcer(s) or duodenal ulcer(s) within 4 weeks before the first dose of study drug.
  • The participant has had clinically significant upper or lower gastrointestinal bleeding within 4 weeks prior to the Screening Period.
  • The participant has esophageal stricture(s) unable to be passed with an 8 to 10 mm endoscope, clinically requires dilation, or has a history of dilation within the 3 months prior to the Screening Period.
  • Use of prescription or non-prescription PPIs or PCABs within 2 months prior to the Screening Period.
  • Use of swallowed topical corticosteroid or budesonide oral suspension for EoE within 2 months prior to the Screening Period.
  • Use of systemic corticosteroid for any condition within 3 months prior to the Screening Period.
  • Use of inhaled or nasal glucocorticoids within 3 months prior to the Screening Period, except stable dose for at least 3 months prior to the Screening Period for any condition (should not be changed during the study).
  • Use of dupilumab within 3 months prior to the Screening Period.
  • The participant has received any investigational compound within 30 days or any investigational biologic within 3 months prior to the start of the Screening Period (including those in post-marketing studies) or vonoprazan in a clinical trial at any time. A participant who has been screen failed from another clinical study and who has not been dosed may be considered for enrollment in this study.
  • The participant has used immunomodulatory therapy within 3 months prior to the Screening Period or anticipates using immunomodulatory therapy during the study (except for any ongoing regimen of allergy therapy).
  • The participant is a study site employee, an immediate family member, is in a dependent relationship with a study site employee who is involved in the conduct of this study (eg, spouse, parent, child, sibling), or who may have consented under duress.
  • The participant has a history of hypersensitivity or allergies to vonoprazan (including the formulation excipients: D-mannitol, microcrystalline cellulose, hydroxypropyl cellulose, ascorbic acid, fumaric acid, croscarmellose sodium, magnesium stearate, hypromellose, macrogol 8000, titanium oxide, or red ferric oxide). Skin testing may be performed according to local standard practice to confirm hypersensitivity.
  • The participant has a history of alcohol abuse, illegal drug use, drug addiction or regularly consumes alcohol within the 12 months prior to the Screening Period (based on self-report). Participants must have a negative urine drug screen for non-prescribed medications at screening. Participants taking prescription drugs will be allowed. Occasional, recreational use of cannabis is allowed. However, participants with a cannabis use disorder (eg, frequent use, functional-social impairment, withdrawal symptoms) per the opinion of the investigator should be excluded.
  • The participant is taking any excluded medications or treatments listed in the protocol.
  • If female, the participant is pregnant, lactating, or intending to become pregnant before, during, or within 4 weeks after participating in this study, or intending to donate ova during such time period.
  • The participant has a history or clinical manifestations of significant central nervous system, cardiovascular, pulmonary, metabolic, other gastrointestinal, urological, endocrine, or hematological disease that, in the opinion of the investigator, would confound the study results or compromise participant safety.
  • The participant has a history of malignancy (including MALToma) or has been treated for malignancy within 5 years prior to the start of the Screening Period (Visit 1). The participant may be included in the study if he/she has recovered from cutaneous basal cell carcinoma or cervical carcinoma in situ.
  • The participant has acquired immunodeficiency syndrome or human immunodeficiency virus infection, or tests positive for the hepatitis B surface antigen, hepatitis C virus (HCV) antibody, or HCV-ribonucleic acid (RNA). However, participants who test positive for HCV antibody but negative for HCV-RNA are permitted to participate.
  • The participant has Zollinger-Ellison syndrome or other gastric acid hypersecretory conditions.
  • The participant requires hospitalization or has surgery scheduled during the course of the study or has undergone major surgical procedures within 30 days prior to the Screening Period.
  • The participant has moderate to severe hepatic impairment (Child-Pugh Class B and Child-Pugh Class C).
  • The participant has severe renal impairment (estimated glomerular filtration rate <30 mL/min).
  • The participant has any of the following abnormal laboratory test values at the start of the Screening Period:
  • Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2 × the upper limit of normal (ULN) or total bilirubin >2 × ULN (except participants with Gilbert Syndrome).
  • Creatinine levels: >2 mg/dL (>177 μmol/L)
  • The participant is refractory to prior PPI therapy as judged by the investigator.

Trial locations and contacts

41 sites in 1 country.

41 sites in 1 country

United States41 sites

  • Treasure Valley Medical Research

    Boise, Idaho, 83706

  • Boston Specialists

    Boston, Massachusetts, 02111

  • Brigham and Women's Hospital

    Boston, Massachusetts, 02115

  • Connecticut Clinical Research Institute

    Bristol, Connecticut, 06010

  • GI Alliance

    Cedar Park, Texas, 78613

  • UNC Clinical & Translational Research Center

    Chapel Hill, North Carolina, 27514

  • Galen Medical Group - Galen Digestive Health

    Chattanooga, Tennessee, 37404

  • Northwestern Medicine Digestive Health Center

    Chicago, Illinois, 60611

  • GW Research, Inc

    Chula Vista, California, 91910

  • GCGA Physicians, LLC dba/Gastro Health Research

    Cincinnati, Ohio, 45219

  • The Hospitals of Providence Memorial Campus

    El Paso, Texas, 79902

  • Woodholme Gastroenterology Associates

    Glen Burnie, Maryland, 21061

  • GI Alliance - Gurnee

    Gurnee, Illinois, 60031

  • Texas Digestive Specialists

    Harlingen, Texas, 78550

  • Houston Endoscopy and Research Center

    Houston, Texas, 77079

  • Research Physicians Network, LLC

    Houston, Texas, 77089

  • Grand Teton Research Group

    Idaho Falls, Idaho, 83404

  • Nature Coast Clinical Research

    Inverness, Florida, 34452

  • Encore Borland-Groover Clinical Research

    Jacksonville, Florida, 32256

  • Combined Gastro, LLC

    Lafayette, Louisiana, 70503

  • Rocky Mountain Gastroenterology

    Lakewood, Colorado, 80228

  • Preferred Research Partners, Inc

    Little Rock, Arkansas, 72211

  • Southern California Research Institute Medical Group

    Los Angeles, California, 90045

  • Blue Ridge Medical Research

    Lynchburg, Virginia, 25402

  • Gastroenterology Associates of Central Georgia, LLC

    Macon, Georgia, 31201

  • Tandem Clinical Research GI, LLC

    Marrero, Louisiana, 70072

  • Biopharma Informatic, LLC

    McAllen, Texas, 78503

  • Great Lakes Gastroenterology Research LLC

    Mentor, Ohio, 44060

  • Quality Medical Research

    Nashville, Tennessee, 37211

  • Weill Cornell Medicine, New York Presbyterian Hospital

    New York, New York, 10065

  • Care Access - Ogdon

    Ogden, Utah, 84403

  • Advanced Research Institute

    Ogden, Utah, 84405

  • Pearland Physicians

    Pearland, Texas, 77581

  • University of Pennsylvania

    Philadelphia, Pennsylvania, 19104

  • Advanced Research Institute

    Reno, Nevada, 89511

  • Gastroenterology Research of San Antonio

    San Antonio, Texas, 78229

  • Advanced Research Institute

    Sandy City, Utah, 84070

  • International Center for Research

    Tampa, Florida, 33614

  • Texas Gastro Consultants

    Tomball, Texas, 73375

  • Western States Clinical Research, Inc.

    Wheat Ridge, Colorado, 80033

  • Huron Gastroenterology Associates

    Ypsilanti, Michigan, 48197

Other trials in United States

About this study

Official title: A Phase 2, Randomized, Double-Blind, Multi-Center Study in Adult Subjects With Eosinophilic Esophagitis (EoE) to Evaluate the Safety and Efficacy of Vonoprazan 20 mg Compared to Placebo After 12 Weeks and to Evaluate the Safety and Efficacy of Vonoprazan 20 mg Up to 24 Weeks

The primary objective of this study is to assess the efficacy of vonoprazan 20 mg once daily (QD) compared to placebo QD in the number of participants with a peak eosinophilic histologic response <15 eosinophils per high-power field (eos/hpf) after 12 weeks of therapy.

Being tested
Vonoprazan, Placebo
Keywords
Vonoprazan, Adults
Medical subject headings
Eosinophilic Esophagitis

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • VonoprazanDrug

    Vonoprazan will be administered orally as a tablet

  • PlaceboDrug

    Placebo will be administered orally as tablet

Study groups in NCT06851559
Study groupRoleWhat they receive
Vonoprazan 20 mgExperimentalParticipants will be administered vonoprazan at a dose of 20 mg for 12 weeks. Participants will continue to receive the same dose for an additional 12 weeks.
Receives: Drug: Vonoprazan
PlaceboExperimentalParticipants will be administered placebo for 12 weeks. Participants will then receive vonoprazan 20 mg for an additional 12 weeks.
Receives: Drug: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Number of Participants at Week 12 Achieving Peak Esophageal Intraepithelial Eosinophil Count <15 eos/hpf.

    Measured: Week 12

Secondary outcomes (3)

  1. Mean Change from Baseline to Week 12 in Dysphagia Days

    Measured: Baseline and Week 12

  2. Mean Change from Baseline to Week 12 in EoE Endoscopic Reference Score (EREFS).

    Measured: Baseline and Week 12

  3. Mean Change from Baseline to Week 12 in Peak Esophageal Intraepithelial Eosinophil Count.

    Measured: Baseline and Week 12

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted28 Feb 2025
  2. Study start30 Oct 2025
  3. Primary completion11 Sep 2026
  4. Study completionDec 2026 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Model description
The study will enroll participants ≥18 years of age.
Masking
Double blind
Who is masked
Participant, Investigator
Enrolment
95 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06851559
Sponsor's protocol ID
EoE-201
Status last verified
Oct 2026
First submitted
24 Feb 2025
Last updated
13 Oct 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Vonoprazan in people with Eosinophilic Esophagitis, run by Phathom Pharmaceuticals, Inc. at 41 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 7 inclusion and 35 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 13 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 41 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Number of Participants at Week 12 Achieving Peak Esophageal Intraepithelial Eosinophil Count <15 eos/hpf. (time frame: Week 12). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06851559.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Oct 2026.

AzTrials uses cookies for analytics and advertising. You can accept or reject them; the site works either way. Privacy Policy.

Free account

Log in to keep searching

You’ve used your 3 free searches. AzTrials is free: log in or create a free account to keep searching clinical trials and save the ones you want to follow.

Create a free accountLog in