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

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.