The primary purpose of this study is to evaluate the effect of hepatic impairment on the systemic pharmacokinetics, safety, and tolerability of icenticaftor in participants with varying degrees of hepatic impairment.

This is a Phase 1, multi-center study with parallel groups. The study employs a single-dose, open-label design in subjects with mild, moderate, or severe hepatic impairment along with matched healthy control subjects with normal hepatic function. Subjects with normal hepatic function will be matched with subjects with hepatic impairment for gender, age (± 10 years), body weight (± 15%), and smoking status (smoker or non-smoker).

Up to a total of 48 participants will be enrolled in this study (approximately 8 in each mild [Child-Pugh A], moderate [Child-Pugh B], severe hepatic impairment [Child-Pugh C] groups), and up to 24 healthy control subjects). Each participant will receive a single oral dose of 300 mg of icenticaftor (QBW251) on Day 1 under fasting conditions.

The study is comprised of an up to 28-day screening period (Days -28 to -1), a baseline evaluation (Day -1) prior to treatment on Day 1, and a follow-up period of 7 days for pharmacokinetics (PK) sample collection (pre-dose, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 24, 36, 48, 72, 96, 120, 144 and 168 hours post-dose). A safety follow-up contact will be done 30 days after administration of the study drug.

The primary purpose of this study is to evaluate the effect of hepatic impairment on the systemic PK, safety, and tolerability of icenticaftor in participants with varying degrees of hepatic impairment.

All Participants:

Inclusion Criteria:

• Male and non-child bearing potential female participants, 18 to 75 years of age (inclusive) at Screening.
• Participants must weigh at least 50.0 kg and must have a body mass index (BMI) within the range of 18.0 to 38.0 kg/m2, inclusive, at Screening.
• Must be a non-smoker or agree to smoke no more than 5 cigarettes (or equivalent) per day from Screening until the End of Study. Participants must maintain the same smoking status throughout the study (i.e. smoker or non smoker).

Exclusion Criteria:

• Use of other investigational drugs within 5 half-lives prior to dosing of study treatment, or within 30 days, whichever is longer; or longer if required by local regulations.
• Are taking medications prohibited to be taken with the study treatment
• Known history of, or current clinically significant arrhythmias. Have clinically significant ECG abnormality or history of long-QT syndrome or whose QT interval corrected by Fridericia's formula (QTcF) is prolonged (> 480 msec) at Screening. Participants having myocardial infarction ≥ 5 years ago are eligible to participate.
• Major gastrointestinal tract surgery such as gastrectomy, gastroenterostomy, or bowel resection.

Healthy Participants:

• Each participant must match in age (± 10 years), gender, weight (± 15%), and smoking status to participants in Group 2, 3, or 4.
• Seated vital signs must be within the following ranges at Screening and Baseline:
• Body temperature, 35.0 to 37.5°C, inclusive.
• Systolic blood pressure, 89 to 149 mmHg, inclusive.
• Diastolic blood pressure, 50 to 89 mmHg, inclusive.
• Pulse rate, 40 to 90 bpm, inclusive.
• Participants must be in good health as determined by medical history, physical examination, ECG, and clinical laboratory tests at Screening.

Exclusion Criteria:

• Liver disease or liver injury as indicated by abnormal liver function tests.
• Chronic infection with HBV or HCV.
• History or presence of impaired renal function.

Hepatic Impairment Participants:

Inclusion Criteria:

• Seated vital signs must be within the following ranges at Screening and Baseline:
• Body temperature, 35.0 to 37.5°C, inclusive.
• Systolic blood pressure, 89 to 159 mmHg, inclusive.
• Diastolic blood pressure, 50 to 99 mmHg, inclusive.
• Pulse rate, 50 to 99 bpm, inclusive.
• Hepatic impairment as defined by the Child-Pugh classification for severity of liver disease

Exclusion Criteria:

• Have severe complications of liver disease within the preceding 3 months of Screening.
• Emergency room visit or hospitalization due to liver disease within the preceding 3 months of Screening.
• Have received liver transplant at any time in the past.
• Have encephalopathy Grade 3 or worse within 28 days prior to dosing of study treatment.
• Have acute hepatitis B (HBV) or hepatitis C (HCV) infection.
• Clinically significant abnormal findings in physical examination or clinical laboratory evaluations not consistent with known liver disease.

Other protocol-defined inclusion/exclusion criteria may apply