The purpose of this study is to understand how Osivelotor is processed in people with loss of liver function.

This study is seeking participants that are:

• stable loss of liver function with mild or moderate severity
• none of underlying conditions possibly affecting the study medicine being absorbed by the body

All participants will receive one amount of Osivelotor by mouth before breakfast on the first day at the study clinic. A number of blood samples will be collected to understand how Osivelotor is changed and removed from the body. Participants will also have to undergo physical examination and other tests. This will help to understand if Osivelotor is safe.

Participants will take part in the study for a maximum of 112 days. During this time, participants will have to stay onsite for 5 days. There will be 5 study visits at the study clinic.

Inclusion Criteria:

• Body mass index (BMI) of 16 to 40 kg/m2, inclusive; and a total body weight greater than 50 kg (greater than 110 lb)
• Stable hepatic impairment that meets the criteria for Class A or B of the Child Pugh classification with no clinically significant change in disease status within the 28 days prior to the screening visit
• Stable concomitant medications for the management of individual participants' medical history

Exclusion Criteria:

• Any condition possibly affecting drug absorption (eg, prior bariatric surgery, gastrectomy, ileal resection, prior status portacaval shunt surgery);
• Hepatic carcinoma or hepatorenal syndrome or limited predicted life expectancy;
• A diagnosis of hepatic dysfunction secondary to any acute ongoing hepatocellular process that is documented by medical history, physical examination, liver biopsy, hepatic ultrasound, computerized tomography scan, or MRI;
• Presence of clinically active Stage 3 or 4 hepatic encephalopathy. Clinically active Stage 2 encephalopathy is allowed if, in the opinion of the investigator, the participant is able to provide informed consent.

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.