A Study to Investigate the Influence of Hepatic Insufficiency on the Pharmacokinetics of MK-1439 (MK-1439-019)

Inclusion Criteria:

- Body Mass Index (BMI) between 19 and 40 kg/m^2

- Continuous non-smoker or moderate smoker of <20 cigarettes or equivalent per day.
Agrees to consume <=10 cigarettes or equivalent per day from the time of screening
through the period of sample collection.

- In good health and with no clinically significant electrocardiogram abnormality

- Hepatic impairment participants: diagnosis of chronic (>6 months), stable hepatic
insufficiency with features of cirrhosis due to any etiology. Part 1 only: score of 7
to 9 on the Child-Pugh scale. Part 2: score of 5 to 6 on the Child-Pugh scale.

- Females of childbearing potential: sexually inactive for >=14 days before study drug
administration and throughout the study, or using 2 acceptable methods of barrier
contraception from screening until 14 days after study drug administration.

Exclusion Criteria:

- Mentally or legally incapacitated or has significant emotional problems at the time
of screening or expected during the study

- History or presence of clinically significant medical or psychiatric condition or
disease

- History or presence of drug abuse within the past 2 years

- History or presence of hypersensitivity or idiosyncratic reaction to the study drug
or related compounds

- Female participant who is pregnant or lactating

- Positive results for breath alcohol or urine drug screen (unless due to prescription
drug use and is approved by the investigator) at screening

- Positive for HIV at screening

- Unable to refrain from or anticipates the use of any drug known to be a significant
inhibitor or inducer of cytochrome oxidase CYP3A or P-glycoprotein, or any medication
or substance which cannot be discontinued at least 14 days before study drug
administration and throughout the study.

- Donation of >500 mL of blood or had significant blood loss within 56 days before
study drug administration

- Plasma donation within 7 days before study drug administration

- Dosed in another clinical trial within 28 days before study drug administration

- Healthy control participants only: positive for hepatitis B surface antigen (HBsAg)
or hepatitis C virus (HCV) at screening;