The purpose of this clinical trial is to learn about the safety and effects of study medicine PF-07264660 compared to a placebo. This is the first study of PF-07264660 in humans. All participants in this study will received PF-07264660 or a placebo and it will be assigned by chance. People may be able to participate if they are healthy. The study medicine may be given by shots under the skin or through a vein depending on which group you are assigned to. If you are assigned into Part A, you will receive the study medicine once, stay overnight at the research unit from 3 to 5 overnight stays and you will need to visit the clinic about 11 follow-up visits. Participants will be in this study for up to about 541 days. If you are assigned into Part B, you will receive the study medicine three times, stay overnight at the clinic from 3 to 5 overnight stays and you will need to visit the research unit about 12 follow-up visits. Participants willbe in this study for up to about 561 days.

This is an first-in-human within-cohort randomized, participant- and investigator-blind, sponsor-open, placebo-controlled study of the safety, tolerability, pharmacokinetics, and pharmacodynamics following single ascending dose and multiple ascending dose.

PF-07264660 that will be conducted in healthy adults. Up to approximately 67 participants will be enrolled into the study and randomly assigned to receive PF-07264660 or placebo. This will include up to approximately 43 healthy participants (including 5 optional Japanese participants) in Part A, and up to approximately 24 healthy participants (including 8 participants in optional multiple ascending dose cohort) in Part B.

Inclusion Criteria:

• Healthy volunteer male and female participants between 18 to 65 years of age
• Body Mass Index (BMI) of 17.5 to 32 kg/m2; and a total body weight >50 kg (110 lb)

Exclusion Criteria:

• 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).
• Evidence of active, latent, or inadequately treated infection with Mycobacterium tuberculosis
• Participants with acute or chronic infections or infection history
• History of human immunodeficiency virus (HIV); Infection with hepatitis B or hepatitis C viruses according to protocol specific testing algorithm
• History of febrile illness within 5 days prior to the first dose of investigational product.
• Recent exposure to live or attenuated vaccines within 28 days of the screening visit.
• Failure to comply with coronavirus disease 2019 (COVID-19) vaccination requirements as per site protocols.
• Have any malignancies or have a history of malignancies with the exception of adequately treated or excised non-metastatic basal cell or squamous cell cancer of the skin, or cervical carcinoma in situ.
• History of any lymphoproliferative disorder such as Epstein-Barr Virus (EBV) related lymphoproliferative disorder, history of lymphoma, leukemia, or signs and symptoms suggestive of current lymphatic or lymphoid tissue disease.
• Undergone significant trauma or major surgery within 1 month of the first dose of study drug
• Previous administration with an investigational product (drug or vaccine) within 30 days (or as determined by the local requirement) or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer)
• Screening supine blood pressure (BP) ≥140 mm Hg (systolic) or ≥90 mm Hg (diastolic), following at least 5 minutes of supine rest
• Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) level ≥1.5 × Upper limit of normal (ULN);
• Total bilirubin level ≥1.5 × ULN; participants with a history of Gilbert's syndrome may have direct bilirubin measured and would be eligible for this study provided the direct bilirubin level is ≤ULN.
• estimated glomerular filtration rate (eGFR) ≤75 mL/min/1.73 m2 based on chronic kidney disease epidemiology (CKD-EPI) equation
• History of alcohol abuse or binge drinking and/or any other illicit drug use or dependence within 6 months of Screening
• Participants with more than 5 cigarettes per day or ≥10 pack years
• Blood donation (excluding plasma donations) of approximately 1 pint (500 mL) or more within 60 days prior to dosing

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.

Investigators and other site staff will be blinded to participants' assigned study intervention.

Participants will be assigned to receive study intervention according to the assigned treatment group from the randomization scheme. Investigators will remain blinded to each participant's assigned study intervention throughout the course of the study.

In the event of a Quality Assurance audit, the auditor(s) will be allowed access to unblinded study intervention records at the site(s) to verify that randomization/dispensing has been done accurately.

Sponsor staff not directly involved in the conduct of the study will be unblinded to participants' assigned study intervention.