A Phase 2 Study to Investigate the Efficacy and Safety of Zelicapavir in Participants Aged ≥28 Days to ≤36 Months of Age Infected With Respiratory Syncytial Virus

July 17, 2026 updated by: Enanta Pharmaceuticals, Inc

Phase 2, Randomized, Double-blind, Placebo-controlled Study to Evaluate the Efficacy and Safety of Zelicapavir in Participants ≥28 Days to ≤36 Months of Age Infected With Respiratory Syncytial Virus

Zelicapavir is a novel, orally administered, nonfusion replication inhibitor of RSV. It is being investigated in this Phase 2 study (EDP 938-203) as a potential treatment for RSV infection in both hospitalized and non-hospitalized children aged ≥28 days to ≤36 months who present with symptomatic RSV infection.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
150

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Thailand
      • Bangkok, Thailand, 10330
        • Recruiting
        • Center of Excellence for Pediatric Infectious Diseases and Vaccines Faculty of Medicine, Chulalongkorn University (CE-PID)
        • Contact:
        • Principal Investigator:
          • Napaporn Chantasrisawad, MD
      • Chiang Mai, Thailand, 50200
        • Recruiting
        • Maharaj Nakorn Chiang Mai Hospital
        • Contact:
        • Principal Investigator:
          • Tavitiya Sudjaritruk, MD
      • Chiang Mai, Thailand, 50180
        • Recruiting
        • Nakornping Hospital
        • Contact:
        • Principal Investigator:
          • Rujirek Kamolrattana, MD
      • Chiang Rai, Thailand, 57000
        • Recruiting
        • Chiangrai Prachanukroh Hospital
        • Contact:
        • Principal Investigator:
          • Suchada Ruenglerdpong, MD
      • Khon Kaen, Thailand, 40000
        • Recruiting
        • Khon Kaen Hospital
        • Contact:
        • Principal Investigator:
          • Ussanee Srirompotong, MD
      • Lampang, Thailand, 52000
        • Recruiting
        • Lampang Hospital
        • Contact:
        • Principal Investigator:
          • Pakawadi Vuttipittayamongkol, MD
      • Lamphun, Thailand, 51000
        • Recruiting
        • Lamphun Hospital
        • Contact:
        • Principal Investigator:
          • Sangravee Juhong, MD
      • Maha Sarakham, Thailand, 44000
        • Recruiting
        • Maha Sarakham Hospital
        • Contact:
        • Principal Investigator:
          • Supawan Papakhee, MD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Participants diagnosed with RSV infection using an approved diagnostic assay, without known and/or documented coinfection with SARS-CoV-2 or influenza
  • Participant has signs of RSV infection with onset ≤3 days (72 hours) at the time of randomization
  • In the Investigator's opinion, the participant's caregiver understands and is able to comply with protocol requirements, instructions, and restrictions, and the participant is likely to complete the study as planned. The caregiver(s) should be of legal age.

Exclusion Criteria:

  • Participant has any condition that in the opinion of the Investigator would interfere with the evaluation of the study drug or participant safety.
  • Participant has underlying immune deficiency. Participants with immunoglobulin A deficiency are not excluded.
  • Participant has had major surgery within 6 weeks prior to randomization or has major surgery planned during the course of the study.
  • Participant is currently taking either chronically or has taken within 7 days prior to randomization, or is anticipated to receive during the course of the study, systemic medications that are known to cause immunosuppression other than corticosteroids for >5 days.
  • Participant has received an investigational agent within the last 30 days or 5 half-lives of the investigational agent, whichever is longer.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: zelicapavir
zelicapavir, oral suspension, once daily for 7 days
Drug: zelicapavir
Oral suspension
Placebo Comparator: Placebo
Matching placebo, orally, once daily for 7 days
Drug: Placebo
Placebo oral suspension to match zelicapavir

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Time to complete resolution of clinical signs of RSV as measured by RESOLVE-P
Time Frame: Day 1 through Day 14
Day 1 through Day 14

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Time to sustained resolution of clinical signs of RSV as measured by RESOLVE-P
Time Frame: Day 1 through Day 14
Day 1 through Day 14
Change in severity of clinical signs of RSV from Baseline to D7 as measured by RESOLVE-P
Time Frame: Day 1 through Day 7
Day 1 through Day 7
Proportion of participants with Lower Respiratory Tract Infection (LRTI)
Time Frame: D1 through D14
D1 through D14
Change in severity of RSV from Baseline to D7 and D14
Time Frame: Baseline to D7 and D14
Baseline to D7 and D14
Proportion of outpatient participants who were hospitalized due to RSV or other causes during the study period
Time Frame: Day 1 through Day 35
Day 1 through Day 35
Change in RSV viral load as measured by RT-qPCR
Time Frame: Baseline to D7
Baseline to D7
Proportion of participants with viral load Target Not Detected (TND)
Time Frame: Day 4, Day 7 and Day 14
Day 4, Day 7 and Day 14
Time to viral load TND
Time Frame: Day 1 through Day 14
Day 1 through Day 14
Plasma PK Concentrations of zelicapavir
Time Frame: Up to Day 7
Up to Day 7
Safety as measured by frequency of adverse events (AEs)
Time Frame: Up to Day 35
Up to Day 35

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Enanta Pharmaceuticals, Inc

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
PENTA Foundation
AMS-PHPT Research Collaboration, Chiang Mai University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Enanta Pharmaceuticals, Inc, Enanta Pharmaceuticals, Inc

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
July 9, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 1, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 1, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 16, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 16, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 19, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 20, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 17, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • EDP 938-203

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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