The purpose of the study is to look at how the body processes a study medicine called vepdegestrant in participants with loss of liver function relative to people with normal liver function.

This study is seeking participants who are:

• females who cannot have children or males
• between 18 and 70 years of age
• weigh more than 50 Kilograms (110 pounds)
• either healthy with normal liver function or have loss of liver function

All participants in this study will take one dose of vepdegestrant by mouth. This study looks at how the medicine is changed and removed from the body after being taken by the participants. The amount of vepdegestrant in participants with loss of liver function will be compared to the amount of vepdegestrant in participants with normal liver function.

All participants will stay at the study clinic for about 11 days and 10 nights.

Inclusion criteria including but not limited to:

• Female participants of non-childbearing potential, or male participants between the age of 18 years (or the minimum age of consent in accordance with local regulations) and 70 years, inclusive, at screening.
• Body mass index of 17.5-38 kg/m2, inclusive, and a total body weight >50 kg (110 lb).

Normal hepatic function group only:

-Overtly healthy as determined by medical evaluations including medical history, physical examination, laboratory tests, vital signs and standard 12-lead ECGs.

Hepatic impairment groups only:

• Satisfy the criteria for Class B (Group 2: moderate hepatic impairment) or C (Group 3: severe hepatic impairment) of the modified Child-Pugh Classification.
• Stable hepatic impairment, defined as no clinically significant change in disease status within the last 28 days prior to the screening visit, as documented by the participant's recent medical history.

Exclusion criteria including but not limited to:

• Any condition possibly affecting drug absorption.
• Use of prohibited prior or concomitant medications.

Normal hepatic function group only:

-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).

Hepatic impairment groups only:

-A diagnosis of hepatic dysfunction secondary to any acute ongoing hepatocellular process that is documented by medical history, PE, liver biopsy, hepatic ultrasound, CT scan, or MRI.

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.