A Study of How Ibuzatrelvir is Taken up Into the Blood of Healthy Adults After Taking Different Tablets of Ibuzatrelvir

A PHASE 1, OPEN-LABEL, RANDOMIZED, SINGLE-DOSE, 4-PERIOD, CROSSOVER STUDY TO ESTIMATE THE RELATIVE BIOAVAILABILITY AND EFFECT OF FOOD FOLLOWING ORAL ADMINISTRATION OF A NEW TABLET FORMULATION RELATIVE TO THE ORIGINAL FORMULATION OF IBUZATRELVIR IN HEALTHY ADULT PARTICIPANTS

Healthy adults will be enrolled into this open-label, Phase 1 research study. Participants will spend about 9 nights and 10 days in the clinical research unit (CRU) and the total time in the study will be about 11 weeks.

The goal of this clinical trial is to compare how much of the study drug ibuzatrelvir is in participants' blood after taking one of the two different types of tablets containing the same amount of ibuzatrelvir without food. The study will also measure how much ibuzatrelvir is in participants' blood after taking one type of the tablets dispersed in water and when one type of the tablets is taken with food. This study drug is taken by mouth.

Study Overview

• Status: Recruiting
• Conditions: Respiratory Tract Diseases; COVID-19; Pneumonia; Lung Diseases; Coronavirus Disease 2019; Coronavirus Disease 2019 (COVID-19); COVID-19 Infection; Upper Respiratory Tract Infections; Respiratory Tract Infection; COVID-19 (Coronavirus Disease 2019); COVID-19 SARS-CoV-2 Infection
• Intervention / Treatment: Drug: Ibuzatrelvir co-process API film coated tablet; Drug: Ibuzatrelvir filmcoated tablet

Detailed Description

This is a Phase 1, open-label, randomized, 4-period, 6-sequence crossover study in healthy adult participants. The goal of this clinical study is to compare how much of the oral (taken by mouth) study drug ibuzatrelvir is in participants' blood after taking one of the two different types of tablets containing the same amount of ibuzatrelvir without food (fasted). The study will also measure how much ibuzatrelvir is in participants' blood after taking one type of the tablets dispersed in water and when one type of the tablets is taken with food. Safety and tolerability after taking the study medication will also be assessed.

Healthy adult participants will be screened within 28 days prior to the first day of study treatment. Participants will take one dose of study drug on the first day of each of 4 dosing periods that are 2-3 days each. Participants will remain in the clinical research unit (CRU) from Day -1 of Period 1 until completion of procedures on Day 3 of Period 4. This means that participants will stay in the CRU for a total of 9 nights and 10 days. The follow-up phone call will take place approximately 28-35 days after the last dose of study drug. The total time in the study is about 10-11 weeks.

The study treatments are:

Treatment A: ibuzatrelvir (original) fasted Treatment B: ibuzatrelvir (new) fasted Treatment C: ibuzatrelvir (new as dispersion in water) fasted Treatment D: ibuzatrelvir (new) fed

This is a crossover study which means that the treatment groups will receive the same treatments (A, B, C, and D) in a different order during the 4 dosing periods.

Group Period 1 Period 2 Period 3 Period 4

1. A (fasted) B (fasted) C (fasted) D (Fed)
2. A (fasted) C (fasted) B (fasted) D (Fed)
3. B (fasted) A (fasted) C (fasted) D (Fed)
4. B (fasted) C (fasted) A (fasted) D (Fed)
5. C (fasted) A (fasted) B (fasted) D (Fed)
6. C (fasted) B (fasted) A (fasted) D (Fed)

During the screening and time in the CRU participants will have:

• Blood and urine samples collected for safety lab tests
• Pharmacokinetics (PK) blood samples collected to detect concentrations of ibuzatrelvir (up to 40 samples)
• Up to 8 electrocardiograms (ECGs - records the electrical signals controlling your heart)
• To fast (not eat) for at least 10 hours overnight before 3 of the 4 doses

Approximately 18 participants will be enrolled in the study.

• Study Type: Interventional
• Enrollment (Estimated): 18
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Pfizer CT.gov Call Center; Phone Number: 1-800-718-1021; Email: ClinicalTrials.gov_Inquiries@pfizer.com

Study Locations

• Belgium
  • Bruxelles-capitale, Région de
    • Brussels, Bruxelles-capitale, Région de, Belgium, B-1070
      • Recruiting
      • Pfizer Clinical Research Unit - Brussels

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion criteria:

1. 18 years of age or older (or the minimum age of consent in accordance with local regulations) at screening who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and ECGs.
2. BMI of 16-32 kg/m2; and a total body weight >45 kg.
3. Participants who are capable of giving signed informed consent and willing and able to comply with all scheduled visits, treatment plans, laboratory tests, lifestyle considerations, and other study procedures.

Exclusion Criteria

1. Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).

   • Any condition possibly affecting drug absorption (eg, gastrectomy, cholecystectomy).
   • History of HIV infection, hepatitis B, or hepatitis C; positive testing for HIV, HBsAg, or HCVAb. Hepatitis B vaccination is allowed.
2. Any medical or psychiatric condition including any active suicidal ideation in the past year or suicidal behavior in the past 5 years or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
3. Use of prescription or nonprescription drugs and dietary and herbal supplements within 14 days or 5 half-lives (whichever is longer) prior to the first dose of study intervention with the exception of moderate or strong CYP3A inducers which are prohibited within 14 days plus 5 half-lives prior to the first dose of study intervention.
4. Previous administration of an investigational 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).
5. Participation in studies of other investigational products (drug or vaccine) at any time during participation in this study.
6. A positive urine drug test. A single repeat for positive drug screen may be allowed.
7. Screening supine BP ≥140 mm Hg (systolic) or ≥90 mm Hg (diastolic) for participants <60 years; and ≥150/90 mm/Hg for participants ≥60 years old, following at least 5 minutes of supine rest. If systolic BP is ≥140 or 150 mm Hg (based on age) or diastolic ≥90 mm Hg, the BP should be repeated 2 more times and the average of the 3 BP values should be used to determine the participant's eligibility.
8. An eGFR <60 mL/min/1.73 m² as determined by the CKD-EPI equation using Screat.
9. Standard 12 lead ECG that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results (including, but not limited to, QTcF >450 ms, complete LBBB, signs of an acute or indeterminate age myocardial infarction, ST segment and/or T wave changes suggestive of myocardial ischemia, second or third degree AV block, or serious bradyarrhythmias or tachyarrhythmias). If QTcF exceeds 450 ms, or QRS exceeds 120 ms, the ECG should be repeated twice and the average of the 3 QTcF or QRS values used to determine the participant's eligibility. Computer interpreted ECGs with abnormal findings should be overread by an investigator experienced in reading ECGs before excluding a participant.

10. Participants with ANY of the following abnormalities in clinical laboratory tests at screening, as assessed by the study specific laboratory and confirmed by a single repeat test, if deemed necessary:

    • ALT, AST, T Bili >1.5× ULN.

11. History of alcohol abuse or repeated binge drinking and/or any other illicit drug use or dependence within 6 months of screening. Binge drinking is defined as a pattern of 5 (male) and 4 (female) or more alcoholic drinks in about 2 hours. As a general rule, alcohol intake should not exceed 14 units per week (1 unit = 8 ounces (240 mL) beer, 1 ounce (30 mL) of 40% spirit, or 3 ounces (90 mL) of wine).
12. 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.
13. Use of tobacco/nicotine containing products in excess of the equivalent of 5 cigarettes/day or 2 chews of tobacco/day.
14. History of sensitivity reactions to ibuzatrelvir or any of the formulation components of ibuzatrelvir.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Treatment A; single dose of ibuzatrelvir original tablet formulation in the fasted state on Day 1 of the treatment period	Drug: Ibuzatrelvir co-process API film coated tablet; original
Experimental: Treatment B; single dose of ibuzatrelvir new tablet formulation in the fasted state on Day 1 of the treatment period	Drug: Ibuzatrelvir filmcoated tablet; new
Experimental: Treatment C; single dose of ibuzatrelvir of the new tablet formulation dispersed in water and given in the fasted state on Day 1 of the treatment period	Drug: Ibuzatrelvir filmcoated tablet; new
Experimental: Treatment D; single dose of ibuzatrelvir new tablet formulation in the fed state on Day 1 of the treatment period	Drug: Ibuzatrelvir filmcoated tablet; new

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma ibuzatrelvir AUCinf (as data permit, otherwise AUClast) in the fasted state	Relative bioavailability of a new oral formulation of ibuzatrelvir compared to the original tablet formulation in the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period
Plasma ibuzatrelvir AUCinf (as data permit, otherwise AUClast) in the fasted state	Relative bioavailability of a dispersion of a new oral formulation of ibuzatrelvir compared to the original tablet formulation in the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period
Plasma ibuzatrelvir Cmax in the fasted state	Relative bioavailability of a new oral formulation of ibuzatrelvir compared to the original tablet formulation in the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period
Plasma ibuzatrelvir Cmax in the fasted state	Relative bioavailability of a dispersion of a new oral formulation of ibuzatrelvir compared to the original tablet formulation in the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of AEs, clinical laboratory measurements, vital signs, and standard 12-lead ECGs	Evaluate the safety and tolerability of different single-dose oral treatments of ibuzatrelvir	Day 1-35
Plasma ibuzatrelvir AUCinf (as data permit, otherwise AUClast)	Relative bioavailability of a new oral formulation of ibuzatrelvir administered in the fed state compared to the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period
Plasma ibuzatrelvir Cmax	Relative bioavailability of a new oral formulation of ibuzatrelvir administered in the fed state compared to the fasted state	Hour 0 pre-dose in each period and 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 post-dose in each period

Collaborators and Investigators

• Sponsor: Pfizer
• Investigators: Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

Helpful Links

• To obtain contact information for a study center near you, click here.

Study record dates

Study Major Dates

• Study Start (Actual): April 13, 2026
• Primary Completion (Estimated): June 3, 2026
• Study Completion (Estimated): July 6, 2026

Study Registration Dates

• First Submitted: April 7, 2026
• First Submitted That Met QC Criteria: April 22, 2026
• First Posted (Actual): April 27, 2026

Study Record Updates

• Last Update Posted (Actual): April 27, 2026
• Last Update Submitted That Met QC Criteria: April 22, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Pneumonia; COVID-19; Coronavirus infection; COVID-19 infection; Infections; Enzyme inhibitor; Protease inhibitor; Lung disease; Respiratory tract infections; Pneumonia, viral; Anti-infectives; RNA virus infection; Viral protease inhibitor; Anti-viral agents; Ibuzatrelvir
• Additional Relevant MeSH Terms: Virus Diseases; Coronaviridae Infections; Nidovirales Infections; COVID-19; Lung Diseases; Pneumonia; Infections; Respiratory Tract Infections; Respiratory Tract Diseases; Coronavirus Infections; Pneumonia, Viral; RNA Virus Infections
• Other Study ID Numbers: C5091029; 2025-525041-43-00 (Registry Identifier: REGISTRY: CTIS (EU))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: 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.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No