A Study of Effects of Selpercatinib in Hepatically Impaired Participants and Healthy Participants

Inclusion Criteria: * Female participants of non-childbearing potential who are agreeable to take birth control measures until study completion * Males who are capable of fathering a child must agree to use one of the following methods of contraception from the time of the dose administration through 6 months after dose administration: * Male sterilization, with documented confirmation of surgical success. Male subjects will be surgically sterile for at least 90 days prior to Check-in (Day -1). If documentation is not available, male subjects must follow one of the contraception methods below: * Male condom with spermicide, or * For a female partner of male study participant: * Intrauterine device (IUD) (hormonal IUD; eg, Mirena®). Copper IUDs are acceptable (eg, ParaGard®); * Established use of oral, implanted, transdermal, or hormonal method of contraception associated with inhibition of ovulation; or * Bilateral tubal ligation. * Body mass index (BMI) ≥ 18.0 and ≤ 32.0 kilograms per meter squared (kg/m²) and had a minimum weight of at least 50 kg at screening * Have normal blood pressure, pulse rate, electrocardiogram (ECG), and blood and urine laboratory test results that are acceptable for the study Exclusion Criteria: * Are currently participating in or completed a clinical trial within the last 30 days or any other type of medical research judged to be incompatible with this study * Have previously participated or withdrawn from this study * Have or used to have health problems or laboratory test results or ECG readings that, in the opinion of the doctor, could make it unsafe to participate, or could interfere with understanding the results of the study * Had blood loss of more than 500 milliliters (mL) within the previous 30 days of study screening * Require treatment with inducers or inhibitors of cytochrome P450 (CYP) CYP3A within 14 days before the first dose of study drug through the end of treatment or early termination