Single-Dose Pharmacokinetics of MK-3866 in Participants With Hepatic Impairment (MK-3866-006)

Inclusion Criteria: * Body mass index ≥19 \& ≤40 kg/m\^2 * Continuous non-smoker prior to screening \& enrollment * HI Participants: Baseline health judged to be stable based on medical history (except for the HI condition), physical examination, vital signs, electrocardiograms, \& laboratory safety tests * Healthy control participants: Is medically healthy with no clinically significant medical history, physical examination, laboratory profiles, vital signs, or electrocardiograms * HI Participants: Diagnosis of chronic (\>6 months), stable (no acute episodes of illness within the previous 2 months due to deterioration in hepatic function) HI with features of cirrhosis * HI Participants - Panel A (moderate HI) only: score on the Child-Pugh scale from 7 to 9 (moderate HI). At least 3 participants must have a score of 2 or higher on at least one of the laboratory parameters (i.e., albumin, international normalized ratio, and/or bilirubin) on the Child-Pugh scale * HI Participants - Panel B (severe HI) only: Score on the Child-Pugh scale from 10 to 15 (severe HI) * Is completely informed of the unknown risks of pregnancy \& agrees not to become pregnant or father a child during time in study * For a female of childbearing potential: is either sexually inactive (abstinent) for 14 days prior to dosing \& throughout the study or is using an acceptable birth control method * Non-vasectomized male: Participants must agree to use a condom with spermicide or abstain from sexual intercourse from dosing until 90 days after dosing Exclusion Criteria: * Mentally or legally incapacitated or has significant emotional problems at the time of the screening visit or expected during the conduct of the study * Has a history or presence of clinically significant medical or psychiatric condition or disease (other than HI - Panels A \& B) that might confound the results of the study or poses an additional risk to the participant. Remote history of cholecystectomy that is not an active issue may be included. * Panels A \& B: Has a clinically significant history of cancer. Remote history with full cure or limited disease with complete resection (cure) may be included * Has a history of drug/alcohol abuse within the past 6 months prior to dosing (Panels A \& B) or within the past 2 years prior to dosing (Panel C \[Healthy controls\]) * Panels A \& B: Consumes more than 3 glasses of alcoholic beverages (1 glass approximately equivalent to: beer \[354 mL/12 ounces\], wine \[118 mL/4 ounces\], or distilled spirits \[29.5 mL/1 ounce\]) per day, within 6 months of screening. Participants that consume 4 glasses of alcoholic beverages/day may be enrolled * Panels A \& B: Consumes excessive amounts, defined as more than 6 servings (1 serving approximately equivalent to 120 mg of caffeine), of coffee, tea, cola, energy-drinks, or other caffeinated beverages/day * Panels A \& B: Has a history of a liver transplant * Has a history or presence of hypersensitivity or idiosyncratic reaction to the study drugs or related compounds * Has moderate or severe renal insufficiency (estimated glomerular filtration rate of ≤60 mL/min/1.73 m2 for moderate HI or healthy control participants or ≤50 mL/min/1.73 m2 for severe HI participants) * Panel C: Has positive macroscopic urine protein at screening (trace protein by dipstick allowed) * Is a female participant who is pregnant or lactating * Has positive results for the urine or breath alcohol screen and/or urine drug screen at screening * Has positive results at screening for human immunodeficiency virus (HIV) (Panels A \& B) or for HIV, HBsAg, or hepatitis C virus (HCV) (Panel C) * Panels A \& B: Participants with active HCV infection or hepatitis B virus (HBV) infection. Participants with prior/inactive HCV infection or past HBV infection may be enrolled. * Is unable to refrain from or anticipates use of any medication or substance prohibited in study * Has taken amiodarone at any time in their life