A Study to Learn About How Different Forms of Study Medicine Prifetrastat Are Taken Up Into the Blood in Healthy Adults

A PHASE 1, RANDOMIZED, OPEN-LABEL, 2-PERIOD, 4-SEQUENCE SINGLE-DOSE CROSSOVER STUDY IN HEALTHY PARTICIPANTS TO INVESTIGATE THE RELATIVE BIOAVAILABILITY OF PRIFETRISTAT DRUG PRODUCT DIFFERING IN PARTICLE SIZE DISTRIBUTION

The purpose of this study is to understand the relative amount of drug that enters bloodstream from prifetrastat product lots differing in active ingredient particle size distribution.

The study is seeking participants who are:

Healthy males and females of non-childbearing potential >=18 years of age at screening

Participants in the study will receive a single dose of prifetrastat by mouth. After at least 14 days, they will receive another dose of prifetrastat by mouth. Each dose received by the patient will be in tablet form. The sequence in which tablets are given will be random.

The study will help understand how the difference in particle size distributions of the tablets may, or may not, affect how the drug is absorbed, processed, and eliminated by the body.

Participants will remain in the study clinic for 21 days. However, they may be permitted to leave between periods, and will have one follow-up contact.

Study Overview

• Status: Recruiting
• Conditions: Healthy Participant
• Intervention / Treatment: Drug: prifetrastat Reference; Drug: prifetrastat Test 1; Drug: prifetrastat Test 2

• Study Type: Interventional
• Enrollment (Estimated): 32
• 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

• Females of non-childbearing potential and males >=18 years of age at screening who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, vital signs and 12-lead ECGs.
• BMI of 18-32 kilogram per meter square(Kg/m^2); and a total body weight >50 kg (110 lb).

Exclusion

• 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
• Prior use of epigenetic modifying agents. Participants will only be permitted to enroll in a single arm of this study (cannot participate in Arm 1 and Arm 2).
• Current use of any prohibited concomitant medication(s) or unwillingness or inability to use a required concomitant medication(s).
• current use or anticipated need for food or drugs that are known strong inducers or inhibitors of CYP2C9 or CYP3A4, including their administration within 14 days plus 5 half-lives of the strong inducers or inhibitors of CYP2C9 or CYP3A4, whichever is longer, prior to first dose of study intervention, during the treatment period, and within 2 days after the last dose of prifetrastat
• Proton pump inhibitors must be discontinued at least 14 days prior to the first dose of study medication and throughout treatment period.

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

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Arm 1 prifetrastat; Crossover	Drug: prifetrastat Reference; Reference Treatment; Drug: prifetrastat Test 1; Test 1 Treatment
Active Comparator: Arm 2 prifetrastat; Crossover	Drug: prifetrastat Reference; Reference Treatment; Drug: prifetrastat Test 2; Test 2 Treatment

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Area under the Plasma Concentration-Time profile from time 0 to extrapolated infinite time (AUCinf) of Reference treatment of prifetrastat (AUClast If data does not permit AUCinf)	AUCinf was area under the plasma concentration time-curve from zero (pre-dose) extrapolated out to infinite time (If data permits).	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2
Maximum Observed Plasma Concentration (Cmax) profile of Reference prifetrastat treatment	Cmax was the maximum observed plasma concentration directly observed from data.	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2
Area under the Plasma Concentration-Time profile from time 0 to extrapolated infinite time (AUCinf) of Test 1 treatment of prifetrastat (AUClast If data does not permit AUCinf)	AUCinf was area under the plasma concentration time-curve from zero (pre-dose) extrapolated out to infinite time (If data permits).	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2
Maximum Observed Plasma Concentration (Cmax) profile of Test 1 prifetrastat treatment	Cmax was the maximum observed plasma concentration directly observed from data.	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2
Area under the Plasma Concentration-Time profile from time 0 to extrapolated infinite time (AUCinf) of Test 2 treatment of prifetrastat (AUClast If data does not permit AUCinf)	AUCinf was area under the plasma concentration time-curve from zero (pre-dose) extrapolated out to infinite time (If data permits).	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2
Maximum Observed Plasma Concentration (Cmax) profile of Test 2 prifetrastat treatment	Cmax was the maximum observed plasma concentration directly observed from data.	Pre-dose, 0, 0.5, 1, 1.5, 2, 3, 4 ,6 , 8, 12, 24, 36, 48, 72, 96, 144 hours post dose in period 1 and period 2

Secondary Outcome Measures

Outcome Measure	Time Frame
Number of Participants With Treatment Emergent Adverse Events (TEAEs)	Up to Day 35 after the last dose of study intervention in Period 2
Number of Participants with Clinically Significant Abnormalities in Laboratory Parameters	Up to Day 35 after the last dose of study intervention in Period 2
Number of Participants With Clinically Significant Abnormalities in Vital Signs	Up to Day 35 after the last dose of study intervention in Period 2
Number of Participants With Clinically Significant Electrocardiogram (ECG) Abnormalities	Up to Day 35 after the last dose of study intervention in Period 2
Number of Participants With Clinically Significant Physical Examination Abnormalities	Up to Day 35 after the last dose of study intervention in Period 2

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): July 14, 2026
• Primary Completion (Estimated): December 8, 2026
• Study Completion (Estimated): December 8, 2026

Study Registration Dates

• First Submitted: July 16, 2026
• First Submitted That Met QC Criteria: July 20, 2026
• First Posted (Actual): July 23, 2026

Study Record Updates

• Last Update Posted (Actual): July 23, 2026
• Last Update Submitted That Met QC Criteria: July 20, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Pharmacokinetics; Bioavailability; Distribution; Absorption; Metabolism; Elimination; Healthy Adults
• Other Study ID Numbers: C4551017; 2026-526038-26-00 (Registry Identifier: 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