Respiratory Syncytial Virus InfectionPhase 2/3NCT06079320
A Study to Learn About the Study Medicine Sisunatovir in Adults With Respiratory Syncytial Virus (RSV) Infection
A Phase 2/3 study testing Sisunatovir in people with Respiratory Syncytial Virus Infection, run by Pfizer at 19 sites in 4 countries.
Trial summary
The purpose of this study is to learn about the safety and effects of sisunatovir. Sisunatovir is studied for the possible treatment of Respiratory Syncytial Virus (RSV). RSV is a virus that causes lung infections with cold-like symptoms, but it can cause severe illness in some people. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Respiratory Syncytial Virus Infection
- What is being tested?
- Sisunatovir
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 16 participants
- Where
- 19 sitesin 4 countries
- Study dates
- 8 Dec 2023to 30 Sep 2024
- Phase
- Phase 2/3
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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
- Participants aged 18 years or older at screening.
- Diagnosis of RSV infection collected within 5 days prior to randomization.
- New onset or worsening (if present chronically) of at least one of the following signs and/or symptoms consistent with a viral acute respiratory infection (ARI), within 5 days prior to randomization: nasal congestion, nasal discharge, sore throat, cough, sputum production, shortness of breath, or wheezing.
- Has at least 1 of the following characteristics or underlying medical conditions: a) 65 years of age or older b) Chronic lung disease, c) Heart failure, d) Immunosuppressive disease/condition or immune-weakening medications
Who cannot join
- Any medical or psychiatric condition that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study or interfere with the evaluation of response to the study intervention.
- Diagnosis of viral respiratory infections other than RSV including influenza and SARS-CoV-2
- Current need for hospitalization or anticipated need for hospitalization for any reason to provide inpatient/acute care within 24 hours after randomization
- Any clinically significant ECG abnormality in the pre-dose ECG that, per investigator judgement, may affect participant safety
- Has hypersensitivity to or other contraindication to any of the components of the study interventions, as determined by the investigator.
Trial locations and contacts
19 sites in 4 countries.
19 sites in 4 countries
United States14 sites
DM Clinical Research - AOM
Brooklyn, New York, 11220
Mercury Street Medical Group, PLLC
Butte, Montana, 59701
Zenos Clinical Research
Dallas, Texas, 75230
National Institute of Clinical Research
Garden Grove, California, 92844
Biopharma Informatic, LLC
Houston, Texas, 77043
Salma Mazhar, MD PA
Mesquite, Texas, 75149
SMS Clinical Research
Mesquite, Texas, 75149
De La Cruz Research Center, LLC
Miami, Florida, 33184
Adult Medicine of Lake County, Inc.
Mt. Dora, Florida, 32757
Adult Medicine of Lake County
Mt. Dora, Florida, 32757
Accellacare - DuPage
Oak Lawn, Illinois, 60453
Preferred Primary Care Physicians, Preferred Clinical Research (Ofc 18)
Pittsburgh, Pennsylvania, 15236
CHEAR Center LLC
The Bronx, New York, 10455
National Institute of Clinical Research
Westminster, California, 92683
Japan3 sites
National Hospital Organization Minami Kyoto Hospital
Jōyō, Kyoto, 610-0113
Koukankai Koukan Clinic
Kawasaki-Shi, Kanagawa, 210-0852
Nanbu Tokushukai Hospital
Shimajiri, Okinawa, 901-0493
About this study
Official title: AN INTERVENTIONAL PHASE 2/3, ADAPTIVE, MULTI-CENTER, RANDOMIZED, DOUBLE-BLIND STUDY TO INVESTIGATE EFFICACY AND SAFETY OF ORAL SISUNATOVIR COMPARED WITH PLACEBO IN NON-HOSPITALIZED SYMPTOMATIC ADULTS WITH RESPIRATORY SYNCYTIAL VIRUS INFECTION WHO ARE AT RISK OF PROGRESSION TO SEVERE ILLNESS
The purpose of this study is to learn about the safety and effects of sisunatovir. Sisunatovir is studied for the possible treatment of Respiratory Syncytial Virus (RSV). RSV is a virus that causes lung infections with cold-like symptoms, but it can cause severe illness in some people. Sisunatovir is studied in adults:
- who are not admitted to the hospital and
- who have high chances of having a severe illness from RSV infection.
Read more
This study is seeking participants who:
- Are confirmed to have RSV.
- Have symptoms of a lung infection.
- Are 18 years of age or older.
- Have one or more of the following which increases the chances of RSV illness:
- A long-term lung disease.
- heart failure.
- a condition that weakens the immune system.
- Are 65 years of age or older and do not have any of the conditions above
Half of the participants in this study will receive sisunatovir. The other half will receive a placebo for 5 days. Placebo looks same like the study medicine but does not have any medication. Both sisunatovir and placebo will be taken by mouth. The study will compare the experiences of people receiving sisunatovir to those of the people who do not. This will help decide if sisunatovir is safe and effective.
Participants will attend about 8-10 study visits over 5 weeks. During this time, they will have:
- visits at the study clinic,
- blood work,
- swabs of the nose,
- questionnaires,
- a follow-up phone call.
- Conditions
- Respiratory Syncytial Virus Infection
- Being tested
- Sisunatovir, Placebo
- Medical subject headings
- Respiratory Syncytial Virus Infections
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
SisunatovirDrug
Participants will receive tablets from Day 1 to Day 5
PlaceboDrug
Participants will receive matching placebo tablets from Day 1 to Day 5
| Study group | Role | What they receive |
|---|---|---|
| Sisunatovir | Experimental | Not described Receives: Drug: Sisunatovir |
| Placebo | Placebo comparator | Not described Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Participants With Respiratory Syncytial Virus (RSV) Related Hospitalization or Death From Any Cause Through Day 28
RSV related hospitalization included a specialized acute medical care unit within an assisted living facility or nursing home.
Measured: From Day 1 (start of study intervention) up to Day 28
Secondary outcomes (17)
Number of Participants With RSV-Related Visits (Urgent Care/ Emergency Department (ED)/Hospital) or Death From Any Cause Through Day 28
Participants with RSV related visits in a hospital/urgent care or ED requiring no minimum duration of hospitalization were reported in this outcome measure. Investigators determined if a medical visit was related to RSV. RSV-related medical visits were those attendances that would not otherwise occur in the absence of the RSV infection. These may have included: deterioration or decompensation of the lung function that required supplemental oxygen; development of secondary respiratory tract infections that required antibiotic treatment; management of severe symptoms associated with RSV such as fever; worsening or decompensation of cardiac or renal function in participants with underlying cardiac or renal disease.
Measured: From Day 1 (start of study intervention) up to Day 28
Number of Participants With Progression of Lower Respiratory Tract Infection (LRTI) Through Day 10
Progression of LRTI was defined as development of LRTI or transition from non-severe LRTI-RSV at randomization to severe LRTI-RSV at any time up to and including Day 10. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 less than (<) 95 percent (%) or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: From randomization on Day 1 up to Day 10
Number of Participants With Development of LRTI Through Day 10
Development of LRTI was defined as transitioning from not having LRTI at randomization but having nsLRTI-RSV or sLRTI-RSV at any time up to and including Day 10. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95 % or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: From randomization on Day 1 up to Day 10
Number of Participants With Resolution of LRTI at Day 15
Resolution of LRTI was defined as transition from RSV-related non-severe LRTI (nsLRTI-RSV) or RSV-related severe LRTI (sLRTI-RSV) at randomization to not having nsLRTI and sLRTI-RSV. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95 % or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: Day 15
Mean Number of Hospital Free Days Through Day 28
Measured: From Day 1 (start of study intervention) up to Day 28
Number of Participants With Progression of LRTI Through Days 3, 5, 15 and 28
Progression of LRTI was defined as development of LRTI or transition from non severe LRTI-RSV at randomization to severe LRTI-RSV at any time up to and including Days 3, 5, 15 and 28. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95 % or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: From randomization on Day 1 up to Days 3, 5, 15 and 28
Number of Participants With Development of LRTI Through Days 3, 5, 15 and 28
Development of LRTI was defined as transitioning from not having LRTI at randomization but having nsLRTI-RSV or sLRTI-RSV at any time up to and including Days 3, 5, 15 and 28. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95 % or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: From randomization on Day 1 up to Days 3, 5, 15 and 28
Number of Participants With Resolution of LRTI at Days 3, 5, 10 and 28
Resolution of LRTI was defined as transition from nsLRTI-RSV or sLRTI-RSV at randomization to not having nsLRTI and sLRTI-RSV. LRTI was defined as >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95% or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: At Days 3, 5, 10 and 28
Number of Participants With Improvement of LRTI at Days 3, 5, 10, 15 and 28
Improvement in LRTI status was defined as LRTI resolution or transition from sLRTI-RSV at randomization to nsLRTI-RSV. LRTI was defined as: >= 2 lower respiratory signs or symptoms for at least 24 hours including at least 1 lower respiratory sign; or 3 lower respiratory symptoms for at least 24 hours. Lower respiratory symptoms included following: new or increased sputum, new or increased cough, new or increased dyspnea (shortness of breath). Lower respiratory signs included: new or increased wheezing, new or increased crackles/ronchi based on chest auscultation, respiratory rate >= 20 respirations/minute, low or decreased oxygen saturation (O2 < 95 % or <= 90% if pre-season baseline is < 95%), need for new or increased oxygen supplementation.
Measured: At Days 3, 5, 10, 15 and 28
Mean Number of RSV Related Days in Hospital Through Day 28
RSV related hospitalization included a specialized acute medical care unit within an assisted living facility or nursing home.
Measured: From Day 1 (start of study intervention) up to Day 28
Mean Number of RSV Related Days in Intensive Care Unit (ICU) Through Day 28
Measured: From Day 1 (start of study intervention) up to Day 28
Number of Participants With a Clinical Response of Improvement or Resolution at Days 5, 10, 15, and 28
Improvement was defined as no new acute respiratory infection (ARI) signs or symptoms, and no worsening of existing signs or symptoms compared to the Day 1 visit. At least one sign or symptom (but not all) present at Day 1 was absent, improved or returned to pre-infection status. Resolution was defined as all ARI signs or symptoms were absent or returned to pre-infection status. Clinical response was evaluated by the investigator.
Measured: At Days 5, 10, 15, and 28
Number of Participants With Undetectable RSV Viral Load at Days 3, 5, 10, 15 and 28
Undetectable RSV viral load at a visit was defined as a central PCR laboratory result of target not detected (TND).
Measured: At Days 3, 5, 10, 15, and 28
Change From Baseline in Log10 Transformed Total RSV Viral Load at Days 3, 5, 10, 15 and 28
Undetectable viral load was considered to be 0 copies/mL for this analysis.
Measured: Baseline (within 1 hour post start of study intervention on Day 1) and Days 3, 5, 10, 15, and 28
Number of Participants With Treatment Emergent Adverse Events (TEAEs) Through Day 35
An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An adverse event was considered a TEAE if the event started on or after the study intervention start date (Day 1).
Measured: From Day 1 of study intervention up to 28-30 days after last dose of study drug (up to Day 35)
Number of Participants With Treatment Emergent Serious Adverse Events (TESAE) Through Day 35
An SAE was defined as any untoward medical occurrence that, at any dose, met one or more of the criteria listed below: resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, suspected transmission via a Pfizer product of an infectious agent, pathogenic or nonpathogenic and other important medical event.
Measured: From Day 1 of study intervention up to 28-30 days after last dose of study drug (up to Day 35)
Plasma Concentrations of Sisunatovir at Days 3 and 5
Measured: Anytime between 3 to 8 hours post dose on Day 3, and pre-dose on Day 5
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 Oct 2023
- Study start8 Dec 2023
- Primary completion30 Sep 2024
- Study completion30 Sep 2024
Why it stopped: Study discontinued due to business reasons. There were no safety concerns in the decision to stop study and no changes to sponsor's assessment of the risk-benefit profile for participants who received sisunatovir in the study.
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Respiratory Syncytial Virus InfectionStudies of the same condition, open and under way.
- More trials run by PfizerThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
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 2/3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This is a Phase 2/ Phase 3, superiority, adaptive, two parallel-arm, randomized, multi-center, placebo-controlled, double-blind study.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 16 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06079320
- Sponsor's protocol ID
- C5241007
- Other IDs
- 2023-505922-32-00, 2023
- Status last verified
- Oct 2025
- First submitted
- 6 Oct 2023
- Last updated
- 10 Nov 2025
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.
Study at a glance
From the registry record, last updated by the sponsor on 10 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- AN INTERVENTIONAL PHASE 2/3, ADAPTIVE, MULTI-CENTER, RANDOMIZED, DOUBLE-BLIND STUDY TO INVESTIGATE EFFICACY AND SAFETY OF ORAL SISUNATOVIR COMPARED WITH PLACEBO IN NON-HOSPITALIZED SYMPTOMATIC ADULTS WITH RESPIRATORY SYNCYTIAL VIRUS INFECTION WHO ARE AT RISK OF PROGRESSION TO SEVERE ILLNESS
- ClinicalTrials.gov ID
- NCT06079320
- Acronym / sponsor ID
- C5241007
- Conditions
- Respiratory Syncytial Virus Infection
- Phase
- Phase 2/3
- Study type
- Interventional
- Recruitment status
- TerminatedReason stopped: Study discontinued due to business reasons. There were no safety concerns in the decision to stop study and no changes to sponsor's assessment of the risk-benefit profile for participants who received sisunatovir in the study.
- Enrolment
- 16 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 8 Dec 2023 (actual)
- Primary completion
- 30 Sep 2024 (actual)
- Study completion
- 30 Sep 2024 (actual)
- First posted
- 12 Oct 2023 (actual)
- Results
- Posted 10 Nov 2025
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this study is to learn about the safety and effects of sisunatovir. Sisunatovir is studied for the possible treatment of Respiratory Syncytial Virus (RSV). RSV is a virus that causes lung infections with cold-like symptoms, but it can cause severe illness in some people. Sisunatovir is studied in adults:
- who are not admitted to the hospital and
- who have high chances of having a severe illness from RSV infection.
This study is seeking participants who:
- Are confirmed to have RSV.
- Have symptoms of a lung infection.
- Are 18 years of age or older.
- Have one or more of the following which increases the chances of RSV illness:
- A long-term lung disease.
- heart failure.
- a condition that weakens the immune system.
- Are 65 years of age or older and do not have any of the conditions above
Half of the participants in this study will receive sisunatovir. The other half will receive a placebo for 5 days. Placebo looks same like the study medicine but does not have any medication. Both sisunatovir and placebo will be taken by mouth. The study will compare the experiences of people receiving sisunatovir to those of the people who do not. This will help decide if sisunatovir is safe and effective.
Participants will attend about 8-10 study visits over 5 weeks. During this time, they will have:
- visits at the study clinic,
- blood work,
- swabs of the nose,
- questionnaires,
- a follow-up phone call.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- This is a Phase 2/ Phase 3, superiority, adaptive, two parallel-arm, randomized, multi-center, placebo-controlled, double-blind study.
| Arm | Type | Receives |
|---|---|---|
| Sisunatovir | Experimental | Drug: Sisunatovir |
| Placebo | Placebo comparator | Drug: Placebo |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Participants aged 18 years or older at screening.
- Diagnosis of RSV infection collected within 5 days prior to randomization.
- New onset or worsening (if present chronically) of at least one of the following signs and/or symptoms consistent with a viral acute respiratory infection (ARI), within 5 days prior to randomization: nasal congestion, nasal discharge, sore throat, cough, sputum production, shortness of breath, or wheezing.
- Has at least 1 of the following characteristics or underlying medical conditions: a) 65 years of age or older b) Chronic lung disease, c) Heart failure, d) Immunosuppressive disease/condition or immune-weakening medications
Key exclusion criteria (5 listed)
- Any medical or psychiatric condition that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study or interfere with the evaluation of response to the study intervention.
- Diagnosis of viral respiratory infections other than RSV including influenza and SARS-CoV-2
- Current need for hospitalization or anticipated need for hospitalization for any reason to provide inpatient/acute care within 24 hours after randomization
- Any clinically significant ECG abnormality in the pre-dose ECG that, per investigator judgement, may affect participant safety
- Has hypersensitivity to or other contraindication to any of the components of the study interventions, as determined by the investigator.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| SisunatovirParticipants will receive tablets from Day 1 to Day 5 | Drug | Sisunatovir |
| PlaceboParticipants will receive matching placebo tablets from Day 1 to Day 5 | Drug | Placebo |
Primary outcome
Number of Participants With Respiratory Syncytial Virus (RSV) Related Hospitalization or Death From Any Cause Through Day 28
Time frame: From Day 1 (start of study intervention) up to Day 28
RSV related hospitalization included a specialized acute medical care unit within an assisted living facility or nursing home.
17 secondary outcomes
Number of Participants With RSV-Related Visits (Urgent Care/ Emergency Department (ED)/Hospital) or Death From Any Cause Through Day 28
Time frame: From Day 1 (start of study intervention) up to Day 28
Number of Participants With Progression of Lower Respiratory Tract Infection (LRTI) Through Day 10
Time frame: From randomization on Day 1 up to Day 10
Number of Participants With Development of LRTI Through Day 10
Time frame: From randomization on Day 1 up to Day 10
Number of Participants With Resolution of LRTI at Day 15
Time frame: Day 15
Mean Number of Hospital Free Days Through Day 28
Time frame: From Day 1 (start of study intervention) up to Day 28
Number of Participants With Progression of LRTI Through Days 3, 5, 15 and 28
Time frame: From randomization on Day 1 up to Days 3, 5, 15 and 28
Number of Participants With Development of LRTI Through Days 3, 5, 15 and 28
Time frame: From randomization on Day 1 up to Days 3, 5, 15 and 28
Number of Participants With Resolution of LRTI at Days 3, 5, 10 and 28
Time frame: At Days 3, 5, 10 and 28
Number of Participants With Improvement of LRTI at Days 3, 5, 10, 15 and 28
Time frame: At Days 3, 5, 10, 15 and 28
Mean Number of RSV Related Days in Hospital Through Day 28
Time frame: From Day 1 (start of study intervention) up to Day 28
Mean Number of RSV Related Days in Intensive Care Unit (ICU) Through Day 28
Time frame: From Day 1 (start of study intervention) up to Day 28
Number of Participants With a Clinical Response of Improvement or Resolution at Days 5, 10, 15, and 28
Time frame: At Days 5, 10, 15, and 28
Number of Participants With Undetectable RSV Viral Load at Days 3, 5, 10, 15 and 28
Time frame: At Days 3, 5, 10, 15, and 28
Change From Baseline in Log10 Transformed Total RSV Viral Load at Days 3, 5, 10, 15 and 28
Time frame: Baseline (within 1 hour post start of study intervention on Day 1) and Days 3, 5, 10, 15, and 28
Number of Participants With Treatment Emergent Adverse Events (TEAEs) Through Day 35
Time frame: From Day 1 of study intervention up to 28-30 days after last dose of study drug (up to Day 35)
Number of Participants With Treatment Emergent Serious Adverse Events (TESAE) Through Day 35
Time frame: From Day 1 of study intervention up to 28-30 days after last dose of study drug (up to Day 35)
Plasma Concentrations of Sisunatovir at Days 3 and 5
Time frame: Anytime between 3 to 8 hours post dose on Day 3, and pre-dose on Day 5
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 10 Nov 2025.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- To obtain contact information for a study center near you, click here.Link provided by the sponsor.
- Individual participant dataSharing planned: Yes. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pfizer CT.gov Call Center study director
Pfizer
19 sites in 4 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2/3 study testing Sisunatovir in people with Respiratory Syncytial Virus Infection, run by Pfizer at 19 sites in 4 countries.
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 4 inclusion and 5 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: stopped early, as of the sponsor's last update on 10 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 19 sites in United States, Japan, China, India. 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. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined 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.
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 10 Nov 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
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 With Respiratory Syncytial Virus (RSV) Related Hospitalization or Death From Any Cause Through Day 28 (time frame: From Day 1 (start of study intervention) up to Day 28). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 10 Nov 2025.