HealthyPhase 1NCT05536440

A Study to Learn About Study Medicine Called PF-07261271 in Healthy People

A Phase 1 study testing PF-07261271 in people with Healthy, run by Pfizer at 4 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Trial summary

The purpose of this clinical trial is to learn about the safety and effects of the study medicine PF-07261271 for the potential treatment of Inflammatory Bowel Disease. Read more about this study

Who is it for?: Ages 18 to 65 yearsHealthy volunteers can take part
Conditions the study is for: Healthy
What is being tested?: PF-07261271
Type of treatment: Injection or infusion
Could I receive a placebo?: Yes, some participants may receive a placebo
How many people: 35 participants
Where: 4 sitesUnited States
Study dates: 17 Oct 2022to 29 Feb 2024
Phase: Phase 1
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 to 65 years
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Healthy individuals as determined by medical evaluation
Body mass index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lb).

Who cannot join

Clinically significant medical conditions
History of HIV infection, hepatitis B, or hepatitis C
BP ≥140 mm Hg (systolic) or ≥90 mm Hg (diastolic)
Clinically relevant ECG abnormalities
Previous study drug administration within 30 days or 5 half-lives of first planned dose
History of drug/alcohol abuse or >20 cigarettes/day

Trial locations and contacts

4 sites in 1 country.

United States4 sites

Clinilabs
Eatontown, New Jersey, 07724
Orange County Research Center
Lake Forest, California, 92630
ICON
Salt Lake City, Utah, 84124
Orange County Research Center
Tustin, California, 92780

Other trials in United States

About this study

Official title: A PHASE 1, RANDOMIZED, DOUBLE-BLIND, SPONSOR OPEN, PLACEBO CONTROLLED, DOSE ESCALATING STUDY TO EVALUATE THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF SINGLE INTRAVENOUS AND MULTIPLE SUBCUTANEOUS AND INTRAVENOUS DOSES OF PF-07261271 IN HEALTHY PARTICIPANTS

The purpose of this clinical trial is to learn about the safety and effects of the study medicine PF-07261271 for the potential treatment of Inflammatory Bowel Disease.

Conditions: Healthy
Being tested: PF-07261271, Placebo
Keywords: Healthy volunteer, Healthy, IBD, Inflammatory bowel disease
Medical subject headings: Inflammatory Bowel Diseases

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

PF-07261271Drug
IV or SC
PlaceboDrug
IV or SC

Study groups in NCT05536440
Study group	Role	What they receive
Cohort 1 active	Experimental	Dose A Receives: Drug: PF-07261271
Cohort 1 placebo	Placebo comparator	Dose A Receives: Drug: Placebo
Cohort 2 active	Experimental	Dose B Receives: Drug: PF-07261271
Cohort 2 placebo	Placebo comparator	Dose B Receives: Drug: Placebo
Cohort 3 active	Experimental	Dose C Receives: Drug: PF-07261271
Cohort 3 placebo	Placebo comparator	Dose C Receives: Drug: Placebo
Cohort 4 active	Experimental	Dose D Receives: Drug: PF-07261271
Cohort 4 placebo	Placebo comparator	Dose D Receives: Drug: Placebo
Cohort 5 active	Experimental	Dose E Receives: Drug: PF-07261271
Cohort 5 placebo	Placebo comparator	Dose E Receives: Drug: Placebo
Cohort 6 active	Experimental	Dose F Receives: Drug: PF-07261271
Cohort 6 placebo	Placebo comparator	Dose F Receives: Drug: Placebo
Cohort 7 active	Experimental	Dose G Receives: Drug: PF-07261271
Cohort 7 placebo	Placebo comparator	Dose G Receives: Drug: Placebo
Cohort 8 active	Experimental	Dose H Receives: Drug: PF-07261271
Cohort 8 placebo	Placebo comparator	Dose H Receives: Drug: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

Number of Participants With Treatment Emergent Adverse Events (TEAEs): SAD Cohort
An adverse event (AE) was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the end of the last follow-up date, were considered as TEAEs. AEs included all SAEs and Non-SAEs.
Measured: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Number of Participants With Treatment Emergent Adverse Events (TEAEs): MD Cohort
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the end of the last follow-up date, were considered as TEAEs. AEs included all SAEs and Non-SAEs.
Measured: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Number of Participants With Serious Adverse Events (SAEs): SAD Cohort
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. SAEs were defined as any untoward medical occurrence that, at any dose, met one or more of the criteria: 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, was a suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic or other medically significant event.
Measured: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Number of Participants With Serious Adverse Events (SAEs): MD Cohort
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. SAEs were defined as any untoward medical occurrence that, at any dose, met one or more of the criteria: 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, was a suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic or other medically significant event.
Measured: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Number of Participants With Clinically Significant Changes in Vital Signs Abnormalities: SAD Cohort
Criteria for abnormal values of vital signs: systolic blood pressure (millimeters of mercury [mmHg]) value less than (<) 90 mmHg, change greater than or equal to (>=) 30 mmHg increase, change >= 30 mmHg decrease; diastolic blood pressure (mmHg), value <50 mmHg, change >=20 mmHg increase, change >=20 mmHg decrease; pulse rate (beats per minute [bpm]) value <40bpm, value greater than (>) 120bpm. Clinical significance was determined based on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Number of Participants With Clinically Significant Changes in Vital Signs Abnormalities: MD Cohort
Criteria for abnormal values of vital signs: systolic blood pressure (mmHg) value < 90 mmHg, change >= 30 mmHg increase, change >= 30 mmHg decrease; diastolic blood pressure (mmHg), value <50 mmHg, change >=20 mmHg increase, change >=20 mmHg decrease; pulse rate (bpm) value < 40bpm, value > 120bpm. Clinical significance was determined based on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Number of Participants With Clinically Significant Changes in Laboratory Abnormalities: SAD Cohort
Criteria:Hematology(Activated partial thromboplastin time>1.1*upper limit of normal(ULN); Basophils \&eosinophils>1.2*ULN; erythrocytes,hematocrit,hemoglobin,lymphocytes,neutrophils <0.8*lower limit of normal(LLN); leukocytes <0.6*LLN, >1.5*ULN; monocytes >1.2*ULN; platelets <0.5*LLN; prothrombin international randomized ratio \&prothrombin Time >1.1*ULN), clinical chemistry (alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase >3.0*ULN; albumin, protein <0.8*LLN, >1.2*ULN; bicarbonate, calcium, chloride, potassium <0.9*LLN,>1.1*ULN; bilirubin >1.5*ULN; creatinine >1.3*ULN; glucose, Glucose-FASTING <0.6*LLN,>1.5*ULN; Sodium <0.95*LLN,>1.05*ULN; Urate: >1.2*ULN;Urea Nitrogen: >1.3*ULN),urinalysis(Bacteria > 20;epithelial cells >=6;granular, hyaline, RBC\&WBC casts >1;ketones,leukocyte esterase, nitrite, urine glucose, urine hemoglobin, urine protein>=1,urine erythrocytes,leukocytes >=20;pH(scalar)<4.5,>8.Clinical significance determined on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Number of Participants With Clinically Significant Changes in Laboratory Abnormalities: MD Cohort
Criteria:Hematology(Activated partial thromboplastin time>1.1*upper limit of normal(ULN); Basophils \&eosinophils>1.2*ULN; erythrocytes,hematocrit,hemoglobin,lymphocytes,neutrophils <0.8*lower limit of normal(LLN); leukocytes <0.6*LLN, >1.5*ULN; monocytes >1.2*ULN; platelets <0.5*LLN; prothrombin international randomized ratio \&prothrombin Time >1.1*ULN), clinical chemistry (alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase >3.0*ULN; albumin, protein <0.8*LLN, >1.2*ULN; bicarbonate, calcium, chloride, potassium <0.9*LLN,>1.1*ULN; bilirubin >1.5*ULN; creatinine >1.3*ULN; glucose, Glucose-FASTING <0.6*LLN,>1.5*ULN; Sodium <0.95*LLN,>1.05*ULN; Urate: >1.2*ULN;Urea Nitrogen: >1.3*ULN),urinalysis(Bacteria > 20;epithelial cells >=6;granular, hyaline, RBC\&WBC casts >1;ketones,leukocyte esterase, nitrite, urine glucose, urine hemoglobin, urine protein>=1,urine erythrocytes,leukocytes >=20;pH(scalar)<4.5,>8.Clinical significance determined on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Number of Participants With Clinically Significant Changes in Electrocardiogram (ECG) Abnormalities: SAD Cohort
Criteria for abnormal values of ECG parameters: pulse rate (PR) interval greater than or equal to (>=)300 milliseconds (msec); PR interval change >=25 percent (%) or >=50 %, QRS interval >=140 msec and QRS interval change: >=50%. QT interval using Fridericia's correction (QTcF) range from 450 msec to less than (<)480 msec, less than (<) 480 msec to maximum less than or equal to (<=)500 msec, >500 msec, <=30 to <60 msec and >=60 msec. Only rows which included at least 1 participant with abnormality are reported in this outcome measure. Clinical significance was determined based on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Number of Participants With Clinically Significant Changes in ECG Abnormalities: MD Cohort
Criteria for abnormal values of ECG parameters: pulse rate (PR) interval greater than or equal to (>=)300 milliseconds (msec); PR interval change >=25 percent (%) or >=50 %, QRS interval >=140 msec and QRS interval change: >=50%. QT interval using Fridericia's correction (QTcF) range from 450 msec to less than (<)480 msec, less than (<) 480 msec to maximum less than or equal to (<=)500 msec, >500 msec, <=30 to <60 msec and >=60 msec. Only rows which included at least 1 participant with abnormality are reported in this outcome measure. Clinical significance was determined based on investigator's discretion.
Measured: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months

Secondary outcomes (13)

Area Under the Concentration Versus Time Curve From Time Zero to the Last Quantifiable Time Point (AUClast) of PF-07261271: SAD Cohort
AUClast was determined using Linear Log trapezoidal method.
Measured: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Area Under the Serum Concentration Time Profile From Time Zero Extrapolated to Infinite Time (AUCinf) of PF-07261271: SAD Cohort
AUCinf was determined as AUClast + (Clast*/kel), where Clast* is the predicted serum concentration at the last quantifiable time point estimated from the log-linear regression analysis.
Measured: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Maximum Plasma Concentration (Cmax) of PF-07261271: SAD Cohort
Cmax was defined as maximum serum concentration.
Measured: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Time to Maximum Plasma Concentration (Tmax) of PF-07261271: SAD Cohort
Tmax was defined as time for Cmax.
Measured: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Terminal Elimination Half-life (t1/2) of PF-07261271: SAD Cohort
t1/2 was determined using Loge (2)/kel, where kel is the terminal phase rate constant calculated by a linear regression of the log linear -concentration time- curve.
Measured: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Area Under the Concentration Time Profile From Time Zero to Time Tau (τ), the Dosing Interval (AUCtau) of PF-07261271: MD Cohort
AUCtau was defined as area under the concentration time profile from time zero to time tau (τ), the dosing interval, where tau=672 hours for every 4-week dosing. AUCtau was determined by Linear Log trapezoidal method.
Measured: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Cmax of PF-07261271: MD Cohort
Cmax was defined as maximum serum concentration.
Measured: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Tmax of PF-07261271: MD Cohort
Tmax was defined as time for Cmax.
Measured: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Terminal Elimination Half-life (t1/2) of PF-07261271: MD Cohort
t1/2 was determined using Loge (2)/kel, where kel is the terminal phase rate constant calculated by a linear regression of the log linear -concentration time- curve.
Measured: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Number of Participants With Anti-drug Antibodies (ADA) Against PF-07261271: SAD Cohort
ADA positive was defined as ADA titer >= 100; ADA negative defined as ADA titer < 100. Baseline was defined as the last pre-dose measurement
Measured: Baseline up to 15 months
Number of Participants With ADA Against PF-07261271: MD Cohort
ADA positive defined as ADA titer >= 100; ADA negative defined as ADA titer < 100. Baseline was defined as the last pre-dose measurement.
Measured: Baseline up to 15.5 months
Number of Participants With Neutralizing Antibodies (NAb) Against PF-07261271: SAD Cohort
NAb was determined by electrochemiluminescent (ECL) competitive ligand binding assay using the Meso Scale Discovery (MSD) platform.
Measured: Baseline up to 15 months
Number of Participants With NAb Against PF-07261271: MD Cohort
NAb was determined by electrochemiluminescent (ECL) competitive ligand binding assay using the Meso Scale Discovery (MSD) platform.
Measured: Baseline up to 15.5 months

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

17 Oct 202229 Feb 2024

First posted10 Sep 2022
Study start17 Oct 2022
Primary completion29 Feb 2024
Study completion29 Feb 2024

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.
Publications (1)Papers the sponsor has linked to this study.
Other trials for HealthyStudies 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 1
Primary purpose: Treatment
Allocation: Randomised
Intervention model: Sequential
Masking: Double blind
Who is masked: Participant, Investigator
Enrolment: 35 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT05536440
Sponsor's protocol ID: C4631001
Status last verified: Feb 2025
First submitted: 7 Sep 2022
Last updated: 24 Mar 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: No
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: No: 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.

Publications

Neelakantan S, Banfield C, Hung K, Sapone A, Pradhan V, Zhao Y, Parsons-Rich D, Lee G, Johnson BG, Peeva E, Vincent MS, Clerin VM. A phase 1 study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of PF-07261271 in healthy participants. Br J Clin Pharmacol. 2026 Jun 3. doi: 10.1002/bcp.70602. Online ahead of print.
PubMed 42235928

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 24 Mar 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A PHASE 1, RANDOMIZED, DOUBLE-BLIND, SPONSOR OPEN, PLACEBO CONTROLLED, DOSE ESCALATING STUDY TO EVALUATE THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF SINGLE INTRAVENOUS AND MULTIPLE SUBCUTANEOUS AND INTRAVENOUS DOSES OF PF-07261271 IN HEALTHY PARTICIPANTS
ClinicalTrials.gov ID: NCT05536440
Acronym / sponsor ID: C4631001
Conditions: Healthy
Keywords: Healthy volunteer, Healthy, IBD, Inflammatory bowel disease
Phase: Phase 1
Study type: Interventional
Recruitment status: Completed
Enrolment: 35 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 17 Oct 2022 (actual)
Primary completion: 29 Feb 2024 (actual)
Study completion: 29 Feb 2024 (actual)
First posted: 10 Sep 2022 (actual)
Results: Posted 24 Mar 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 clinical trial is to learn about the safety and effects of the study medicine PF-07261271 for the potential treatment of Inflammatory Bowel Disease.

Study design

Primary purpose: Treatment
Allocation: Randomised
Intervention model: Sequential
Masking: Double blind (participant, investigator)
Number of arms: 16

Arm	Type	Receives
Cohort 1 active	Experimental	Drug: PF-07261271Dose A
Cohort 1 placebo	Placebo comparator	Drug: PlaceboDose A
Cohort 2 active	Experimental	Drug: PF-07261271Dose B
Cohort 2 placebo	Placebo comparator	Drug: PlaceboDose B
Cohort 3 active	Experimental	Drug: PF-07261271Dose C
Cohort 3 placebo	Placebo comparator	Drug: PlaceboDose C
Cohort 4 active	Experimental	Drug: PF-07261271Dose D
Cohort 4 placebo	Placebo comparator	Drug: PlaceboDose D
Cohort 5 active	Experimental	Drug: PF-07261271Dose E
Cohort 5 placebo	Placebo comparator	Drug: PlaceboDose E
Cohort 6 active	Experimental	Drug: PF-07261271Dose F
Cohort 6 placebo	Placebo comparator	Drug: PlaceboDose F
Cohort 7 active	Experimental	Drug: PF-07261271Dose G
Cohort 7 placebo	Placebo comparator	Drug: PlaceboDose G
Cohort 8 active	Experimental	Drug: PF-07261271Dose H
Cohort 8 placebo	Placebo comparator	Drug: PlaceboDose H

Who may qualify

Ages: 18 to 65 years
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (2 listed)

Healthy individuals as determined by medical evaluation
Body mass index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lb).

Key exclusion criteria (6 listed)

Clinically significant medical conditions
History of HIV infection, hepatitis B, or hepatitis C
BP ≥140 mm Hg (systolic) or ≥90 mm Hg (diastolic)
Clinically relevant ECG abnormalities
Previous study drug administration within 30 days or 5 half-lives of first planned dose

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
PF-07261271IV or SC	Drug	Cohort 1 active, Cohort 2 active, Cohort 3 active, Cohort 4 active, Cohort 5 active, Cohort 6 active, Cohort 7 active, Cohort 8 active
PlaceboIV or SC	Drug	Cohort 1 placebo, Cohort 2 placebo, Cohort 3 placebo, Cohort 4 placebo, Cohort 5 placebo, Cohort 6 placebo, Cohort 7 placebo, Cohort 8 placebo

Primary outcome

Number of Participants With Treatment Emergent Adverse Events (TEAEs): SAD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
An adverse event (AE) was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the end of the last follow-up date, were considered as TEAEs. AEs included all SAEs and Non-SAEs.
Number of Participants With Treatment Emergent Adverse Events (TEAEs): MD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the end of the last follow-up date, were considered as TEAEs. AEs included all SAEs and Non-SAEs.
Number of Participants With Serious Adverse Events (SAEs): SAD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. SAEs were defined as any untoward medical occurrence that, at any dose, met one or more of the criteria: 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, was a suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic or other medically significant event.
Number of Participants With Serious Adverse Events (SAEs): MD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. SAEs were defined as any untoward medical occurrence that, at any dose, met one or more of the criteria: 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, was a suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic or other medically significant event.
Number of Participants With Clinically Significant Changes in Vital Signs Abnormalities: SAD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Criteria for abnormal values of vital signs: systolic blood pressure (millimeters of mercury [mmHg]) value less than (<) 90 mmHg, change greater than or equal to (>=) 30 mmHg increase, change >= 30 mmHg decrease; diastolic blood pressure (mmHg), value <50 mmHg, change >=20 mmHg increase, change >=20 mmHg decrease; pulse rate (beats per minute [bpm]) value <40bpm, value greater than (>) 120bpm. Clinical significance was determined based on investigator's discretion.
Number of Participants With Clinically Significant Changes in Vital Signs Abnormalities: MD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Criteria for abnormal values of vital signs: systolic blood pressure (mmHg) value < 90 mmHg, change >= 30 mmHg increase, change >= 30 mmHg decrease; diastolic blood pressure (mmHg), value <50 mmHg, change >=20 mmHg increase, change >=20 mmHg decrease; pulse rate (bpm) value < 40bpm, value > 120bpm. Clinical significance was determined based on investigator's discretion.
Number of Participants With Clinically Significant Changes in Laboratory Abnormalities: SAD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Criteria:Hematology(Activated partial thromboplastin time>1.1*upper limit of normal(ULN); Basophils \&eosinophils>1.2*ULN; erythrocytes,hematocrit,hemoglobin,lymphocytes,neutrophils <0.8*lower limit of normal(LLN); leukocytes <0.6*LLN, >1.5*ULN; monocytes >1.2*ULN; platelets <0.5*LLN; prothrombin international randomized ratio \&prothrombin Time >1.1*ULN), clinical chemistry (alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase >3.0*ULN; albumin, protein <0.8*LLN, >1.2*ULN; bicarbonate, calcium, chloride, potassium <0.9*LLN,>1.1*ULN; bilirubin >1.5*ULN; creatinine >1.3*ULN; glucose, Glucose-FASTING <0.6*LLN,>1.5*ULN; Sodium <0.95*LLN,>1.05*ULN; Urate: >1.2*ULN;Urea Nitrogen: >1.3*ULN),urinalysis(Bacteria > 20;epithelial cells >=6;granular, hyaline, RBC\&WBC casts >1;ketones,leukocyte esterase, nitrite, urine glucose, urine hemoglobin, urine protein>=1,urine erythrocytes,leukocytes >=20;pH(scalar)<4.5,>8.Clinical significance determined on investigator's discretion.
Number of Participants With Clinically Significant Changes in Laboratory Abnormalities: MD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Criteria:Hematology(Activated partial thromboplastin time>1.1*upper limit of normal(ULN); Basophils \&eosinophils>1.2*ULN; erythrocytes,hematocrit,hemoglobin,lymphocytes,neutrophils <0.8*lower limit of normal(LLN); leukocytes <0.6*LLN, >1.5*ULN; monocytes >1.2*ULN; platelets <0.5*LLN; prothrombin international randomized ratio \&prothrombin Time >1.1*ULN), clinical chemistry (alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase >3.0*ULN; albumin, protein <0.8*LLN, >1.2*ULN; bicarbonate, calcium, chloride, potassium <0.9*LLN,>1.1*ULN; bilirubin >1.5*ULN; creatinine >1.3*ULN; glucose, Glucose-FASTING <0.6*LLN,>1.5*ULN; Sodium <0.95*LLN,>1.05*ULN; Urate: >1.2*ULN;Urea Nitrogen: >1.3*ULN),urinalysis(Bacteria > 20;epithelial cells >=6;granular, hyaline, RBC\&WBC casts >1;ketones,leukocyte esterase, nitrite, urine glucose, urine hemoglobin, urine protein>=1,urine erythrocytes,leukocytes >=20;pH(scalar)<4.5,>8.Clinical significance determined on investigator's discretion.
Number of Participants With Clinically Significant Changes in Electrocardiogram (ECG) Abnormalities: SAD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months
Criteria for abnormal values of ECG parameters: pulse rate (PR) interval greater than or equal to (>=)300 milliseconds (msec); PR interval change >=25 percent (%) or >=50 %, QRS interval >=140 msec and QRS interval change: >=50%. QT interval using Fridericia's correction (QTcF) range from 450 msec to less than (<)480 msec, less than (<) 480 msec to maximum less than or equal to (<=)500 msec, >500 msec, <=30 to <60 msec and >=60 msec. Only rows which included at least 1 participant with abnormality are reported in this outcome measure. Clinical significance was determined based on investigator's discretion.
Number of Participants With Clinically Significant Changes in ECG Abnormalities: MD Cohort
Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months
Criteria for abnormal values of ECG parameters: pulse rate (PR) interval greater than or equal to (>=)300 milliseconds (msec); PR interval change >=25 percent (%) or >=50 %, QRS interval >=140 msec and QRS interval change: >=50%. QT interval using Fridericia's correction (QTcF) range from 450 msec to less than (<)480 msec, less than (<) 480 msec to maximum less than or equal to (<=)500 msec, >500 msec, <=30 to <60 msec and >=60 msec. Only rows which included at least 1 participant with abnormality are reported in this outcome measure. Clinical significance was determined based on investigator's discretion.

13 secondary outcomes

Area Under the Concentration Versus Time Curve From Time Zero to the Last Quantifiable Time Point (AUClast) of PF-07261271: SAD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Area Under the Serum Concentration Time Profile From Time Zero Extrapolated to Infinite Time (AUCinf) of PF-07261271: SAD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Maximum Plasma Concentration (Cmax) of PF-07261271: SAD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Time to Maximum Plasma Concentration (Tmax) of PF-07261271: SAD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Terminal Elimination Half-life (t1/2) of PF-07261271: SAD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 24, 48, 72, 192, 360, 768, 1104, 1464, 2184, 4344, 5064, 5784, 6504, 7224, 7944, 8664, 10824 hours post dose
Area Under the Concentration Time Profile From Time Zero to Time Tau (τ), the Dosing Interval (AUCtau) of PF-07261271: MD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Cmax of PF-07261271: MD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Tmax of PF-07261271: MD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Terminal Elimination Half-life (t1/2) of PF-07261271: MD Cohort
Time frame: Predose and 0, 2, 4, 8, 12, 48, 96, 192, 360, 720, 744, 1224, 1584, 1944, 2664, 4104, 4824, 5544, 6264, 6984, 7704, 8424, 9144 and 11304 hours post-dose on Day 1 and 29
Number of Participants With Anti-drug Antibodies (ADA) Against PF-07261271: SAD Cohort
Time frame: Baseline up to 15 months
Number of Participants With ADA Against PF-07261271: MD Cohort
Time frame: Baseline up to 15.5 months
Number of Participants With Neutralizing Antibodies (NAb) Against PF-07261271: SAD Cohort
Time frame: Baseline up to 15 months
Number of Participants With NAb Against PF-07261271: MD Cohort
Time frame: Baseline up to 15.5 months

Results and safety

Results posted to the registry on 24 Mar 2025, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
SAD: Placebo	8	8
SAD: PF-07261271 Dose Level 1	2	2
SAD: PF-07261271 Dose Level 2	2	2
SAD: PF-07261271 Dose Level 3	4	4
SAD: PF-07261271 Dose Level 4	6	6
SAD: Placebo (Japanese Participants)	1	1
SAD: PF-07261271 Dose Level 4 (Japanese Participants)	4	4
MD: Placebo	2	2
MD: PF-07261271 Dose Level 3	6	5

Primary outcome: Number of Participants With Treatment Emergent Adverse Events (TEAEs): SAD Cohort

Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months. Count of participants. Unit: Participants

Measure	SAD: Placebo n = 8	SAD: PF-07261271 Dose Level 1 n = 2	SAD: PF-07261271 Dose Level 2 n = 2	SAD: PF-07261271 Dose Level 3 n = 4	SAD: PF-07261271 Dose Level 4 n = 6	SAD: Placebo (Japanese Participants) n = 1	SAD: PF-07261271 Dose Level 4 (Japanese Participants) n = 4
Value	4	1	1	3	2	0	1

Population analysed: Safety analysis set included all participants randomly assigned to study intervention who took at least 1 dose of study intervention.

Primary outcome: Number of Participants With Treatment Emergent Adverse Events (TEAEs): MD Cohort

Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months. Count of participants. Unit: Participants

Measure	MD: Placebo n = 2	MD: PF-07261271 Dose Level 3 n = 6
Value	2	5

Population analysed: Safety analysis set included all participants randomly assigned to study intervention who took at least 1 dose of study intervention.

Primary outcome: Number of Participants With Serious Adverse Events (SAEs): SAD Cohort

Time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months. Count of participants. Unit: Participants

Measure	SAD: Placebo n = 8	SAD: PF-07261271 Dose Level 1 n = 2	SAD: PF-07261271 Dose Level 2 n = 2	SAD: PF-07261271 Dose Level 3 n = 4	SAD: PF-07261271 Dose Level 4 n = 6	SAD: Placebo (Japanese Participants) n = 1	SAD: PF-07261271 Dose Level 4 (Japanese Participants) n = 4
Value	0	0	0	0	0	0	0

Population analysed: Safety analysis set included all participants randomly assigned to study intervention who took at least 1 dose of study intervention.

Primary outcome: Number of Participants With Serious Adverse Events (SAEs): MD Cohort

Time frame: From start of study intervention (Day 1) up to end of study, approximately of 15.5 months. Count of participants. Unit: Participants

Measure	MD: Placebo n = 2	MD: PF-07261271 Dose Level 3 n = 6
Value	0	0

Population analysed: Safety analysis set included all participants randomly assigned to study intervention who took at least 1 dose of study intervention.

13 secondary outcomes are reported in the full results.

Adverse events

Time frame: SAD Cohort: From start of study intervention (Day 1) up to approximately 15 months and MD Cohort: From start of study intervention (Day 1) up to approximately 15.5 months. Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
SAD: Placebo	0 of 8 (0%)	4 of 8 (50%)	0 of 8
SAD: PF-07261271 Dose Level 1	0 of 2 (0%)	1 of 2 (50%)	0 of 2
SAD: PF-07261271 Dose Level 2	0 of 2 (0%)	1 of 2 (50%)	0 of 2
SAD: PF-07261271 Dose Level 3	0 of 4 (0%)	3 of 4 (75%)	0 of 4
SAD: PF-07261271 Dose Level 4	0 of 6 (0%)	2 of 6 (33.3%)	0 of 6
SAD: Placebo (Japanese Participants)	0 of 1 (0%)	0 of 1 (0%)	0 of 1
SAD: PF-07261271 Dose Level 4 (Japanese Participants)	0 of 4 (0%)	1 of 4 (25%)	0 of 4
MD: Placebo	0 of 2 (0%)	2 of 2 (100%)	0 of 2
MD: PF-07261271 Dose Level 3	0 of 6 (0%)	5 of 6 (83.3%)	0 of 6

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 24 Mar 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 42235928Neelakantan S, Banfield C, Hung K, Sapone A, Pradhan V, Zhao Y, Parsons-Rich D, Lee G, Johnson BG, Peeva E, Vincent MS, Clerin VM. A phase 1 study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of PF-07261271 in healthy participants. Br J Clin Pharmacol. 2026 Jun 3. doi: 10.1002/bcp.70602. Online ahead of print.
To obtain contact information for a study center near you, click here.Link provided by the sponsor.
Individual participant dataSharing planned: No. 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

4 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 1 study testing PF-07261271 in people with Healthy, run by Pfizer at 4 sites in United States.

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 2 inclusion and 6 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: finished, as of the sponsor's last update on 24 Mar 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 4 sites in United States. 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 phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

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 24 Mar 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 Treatment Emergent Adverse Events (TEAEs): SAD Cohort (time frame: From start of study intervention (Day 1) up to end of study, approximately up to 15 months). The study lists 10 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05536440, which also lists 1 linked publication.

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 24 Mar 2025.