A Phase 3 interventional study of ibuzatrelvir and placebo in COVID-19 SARS-CoV-2 Infection, sponsored by Pfizer. Recruiting at 256 sites in 19 countries. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Pfizer · Phase 3, Interventional, and Treatment
The purpose of the study is to evaluate whether ibuzatrelvir is effective and safe in adults and adolescents with COVID-19 who do not need to be in the hospital but who are at high risk for progression to severe disease. Eligible participants will be randomly assigned (by chance) to receive ibuzatrelvir or matching placebo orally for 5 days. Co-administration of locally available standard of care is allowed. The total duration of the study is around 6 months.
7,990 studies on the registry are indexed under COVID-19; 466 are open to participants now.
This study's planned enrollment of 2,330 is above the median of 102 across 4,364 interventional studies indexed under COVID-19.
Browse COVID-19 studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Compared within COVID-19, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Pneumonia, Viral. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Presence of risk factors for progression to severe COVID-19 at the time of screening based on age:
The list of risk factors includes:
≥35 kg/m2; Current smoker; Chronic lung disease; Cardiovascular disease; Type 1 or Type 2 diabetes mellitus; Mild to moderate renal impairment; Neurodevelopmental disorders; Sickle cell disease; Moderate .
Exclusion Criteria:
10.Has received any other antiviral for the treatment of COVID-19, including remdesivir, nirmatrelvir/ritonavir, molnupiravir, or COVID-19 mAbs within 30 days or 5 half-lives [whichever is longer] prior to screening, or received convalescent COVID-19 plasma within 12 months.
12.Received any dose of a COVID-19 vaccine within 4 months of randomization or expected to receive one through Day 34.
13.Previous administration of an product (drug or vaccine) within 30 days or 5 half lives preceding the first dose of study intervention used in this study (whichever is longer).
14.Prior participation in this clinical trial or any other clinical trial of ibuzatrelvir.
15.Investigator site staff directly involved in the conduct of the study and their family members, site staff otherwise supervised by the investigator, and sponsor and sponsor delegate employees directly involved in the conduct of the study and their family members.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
A score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Creatinine clearance (CrCl)
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Child-Pugh class
A score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Ibuzatrelvir administered orally every 12 hours (twice daily) for a total of 5 days.
Drug: ibuzatrelvir
placebo administered orally every 12 hours (twice daily) for 5 days.
Drug: placebo
ibuzatrelvir tablets
Also known as: PF-07817883
placebo tablets
Proportion of participants with COVID-19 related emergency department visits, all cause hospitalization and all cause mortality
The difference in proportions of patients requiring COVID 19 related emergency department visits with administration of supplemental oxygen, COVID-19 antiviral or IV treatment (eg hydration, antibiotics, or corticosteroids), all-cause hospitalization, or all-cause death through Day 28 between ibuzatrelvir and placebo, among patients who were treated ≤5 days after COVID-19 symptom onset and who were not receiving background SoC treatment for their COVID-19 infection at baseline.
Time frame: Day 1 through Day 28
Time to sustained resolution of all COVID-19 targeted symptoms
The difference in median time to sustained resolution of all targeted symptoms. Symptoms will be assessed through a daily electronic diary and include sore throat, cough, fever and diarrhea, among others.
Time frame: Day 1 to Day 28
Proportion of participants with post acute COVID-19 medical events
Medical events include cardiovascular events, pulmonary events, acute kidney disease and thromboembolic events.
Time frame: Day 29 to Week 24
Proportion of participants with cardiovascular, renal and pulmonary events
Medical events include cardiovascular events, pulmonary events, acute kidney disease and thromboembolic events.
Time frame: Day 1 to Week 24
Proportion of participants with Long COVID symptoms
The difference in proportions of patients with Long COVID symptoms at Week 24. Symptoms will be assessed through a weekly electronic diary.
Time frame: Day 29 to Week 24
Changes from baseline in SARS-CoV-2 RNA levels in nasopharyngeal/nasal swabs
The viral load is measured in nasal or nasopharyngeal samples using reverse transcription polymerase chain reaction (RT-PCR)
Time frame: Day 1 through Day 34
Time to SARS-CoV-2 RNA <LLOQ
Time needed to achieve a viral load below the lower limit of quantification of the essay used to measure it.
Time frame: Day 1 through Day 34
Proportion of participants with SARS-CoV-2 RNA <LLOQ at each visit
Proportion of participants with a SARS-CoV-2 viral load below the lower limit of quantification of the essay used to measure it.
Time frame: Day 1 through Day 34
Proportion of participants with rebound in SARS-CoV-2 RNA levels in nasopharyngeal swab
Virologic rebound is defined as: at any follow up visit, a viral RNA level increase from End of Treatment (Day 5) of ≥ 1.0 log10 copies/mL resulting in a viral RNA level ≥3.0 log10 copies/mL.
Time frame: Day 10 and Day 14
Proportion of participants with virologic and symptomatic rebound through Day 28
symptoms rebound is defined as: after achieving short symptom recovery (the first day of at least two consecutive diary entries where all targeted symptoms are absent), symptom rebound is the first day of at least two consecutive diary entries after Day 5 where there is any targeted symptom (regardless of severity), or when a participant is hospitalized after symptom recovery.
Time frame: Day 10 to Day 34
Proportion of participants with COVID-19-related hospitalization or all cause death through Day 28.
Time frame: Day 1 to Day 28
Number of days in hospital and ICU stay in participants with hospitalization (all-cause).
Time frame: Day 1 to Week 24
Number of medical visits through Week 24.
medical visits include emergency department visits, hospitalizations, visits to the general practitioner and specialist.
Time frame: Day 1 to Week 24
Proportion of participants with hospitalization (all-cause) or death (all-cause) through Week 24.
Time frame: Day 1 to Week 24
Time (days) to sustained alleviation of all targeted symptoms through Day 28.
The difference in median time to sustained alleviation of all targeted symptoms. Symptoms will be assessed through a daily electronic diary and include sore throat, cough, fever and diarrhea, among others.
Time frame: Day 1 to Day 28
Proportion of participants with severe symptoms attributed to COVID-19 through Day 28.
Participants are required to record the severity of their Covid-19 symptoms over the past 24 hours daily on a 4-point scale ranging from 0 to 3, higher scores indicated more severity. The scale was reported as 0= no symptoms, 1=mild, 2=moderate and 3=severe. A participant with severe score for any targeted symptoms post-baseline is counted as severe. Percentage of participants with severe Covid-19 signs and symptoms is reported.
Time frame: Day 1 to Day 28
Duration of each targeted COVID-19 symptom.
Duration of each targeted COVID-19 symptom is defined as (First Date when the symptom achieved sustained alleviation/resolved)-(First Dose Date) + I for each participant with baseline severity of mild, moderate, or severe.
Time frame: Day 1 to Day 28
Proportion of participants with symptomatic rebound through Day 28.
Definition of symptomatic rebound: After achieving short symptom recovery (the first day of at least two consecutive diary entries where all targeted symptoms are absent), symptom rebound is the first day of at least two consecutive diary entries after Day 5 where there is any targeted symptom (regardless of severity), or when a participant is hospitalized after symptom recovery
Time frame: Day 1 to Day 28
Incidence of treatment emergent adverse events
An adverse event (AE) is any untoward medical occurrence in a participant, temporarily associated with the use of study intervention, whether or not considered related to the study intervention. Serious adverse event (SAE) is any untoward medical occurrence that, at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent or significant disability/ incapacity; congenital anomaly/birth defect; a suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic and other important medical events. AEs included both SAEs and all non-SAEs. An AE is considered as TEAE if the event started on or after start date of study intervention.
Time frame: Day 1 to Day 34
Incidence of SAEs and AEs leading to discontinuations.
Time frame: Day 1 to Day 34
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Plan to share: 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.
Data sharing details ↗ · www.pfizer.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Ibuzatrelvir