The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics of PF-06946860 in healthy adult subjects following single ascending doses This is the first clinical study of PF-06946860.

Key Inclusion Criteria:

• Healthy female subjects of nonchildbearing potential and/or male subjects who, at the time of screening, are between the ages of 18 and 55 years, inclusive
• Body mass index (BMI) within 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lb)
• Evidence of a personally signed and dated informed consent document indicating that the subject has been informed of all pertinent aspects of the study
• Subjects enrolling as Japanese must have four biologically Japanese grandparents born in Japan.

Key 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.
• History of allergic reactions to diagnostic or therapeutic protein or human albumin.
• History of recurrent infections or active infection within 28 days of screening.
• Exposure to live vaccines within 28 days of screening.
• History of regular alcohol consumption or positive drug test
• Treatment with an investigational drug within 30 days (or as determined by the local requirement) or 5 half lives preceding the first dose of IP (whichever is longer).
• Fertile male subjects who are unwilling or unable to use a highly effective method of contraception for the duration of the study and for at least 28 days after the last dose.
• Use of prescription or nonprescription drugs and dietary supplements within 7 days or 5 half lives (whichever is longer) prior to the first dose

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.