The purpose of this study was to evaluate the safety, tolerability, and pharmacokinetics (PK) of ACH-0144471 (danicopan) in participants with hepatic impairment (HI) as compared to healthy matched participants.

Key Inclusion Criteria:

• Body mass index range of 18.0 to 40.0 kilograms (kg)/square meter with a minimum body weight of 50 kg at Screening.
• Females must be of non-childbearing potential.
• Males must agree to abstinence or use a highly effective method of contraception.

HI Participants:

• Be sufficiently healthy for study participation.
• Diagnosis of chronic (>6 months) stable hepatic insufficiency.
• A stable medication regimen.
• In good general health at Screening and check-in, allowing for the concurrent illnesses associated with HI.
• Evidence of cirrhosis due to hepatitis C virus (HCV), hepatitis B virus (HBV) infection, cryptogenic, alcohol abuse, or nonalcoholic steatohepatitis.
• No evidence of hepatocellular carcinoma.
• Have HI as assessed by a Child-Pugh classification score at Screening.

Healthy Participants:

• Participants must be demographically matched to a hepatically impaired participant.
• Medically healthy and without a clinically significant medical history.

Key Exclusion Criteria:

• Evidence of any other clinically significant deviation from normal in a clinical laboratory for the match-controlled participants and laboratory findings beyond those that are consistent with the degree of HI from hepatic participants.
• History of any medical or psychiatric condition or disease.
• Any previous procedure that could alter the absorption or excretion of orally administered drugs.
• Body temperature greater than or equal to 38 degrees centigrade on Day -1 or Day 1 prior to dosing; history of febrile illness or other evidence of infection within 14 days prior to dosing.
• History or presence of drug or alcohol abuse within 6 months prior to dosing; current tobacco/nicotine user; positive for alcohol and/or drugs-of-abuse at Screening or check in.
• Participants who have received eculizumab at any dose or interval within the past 75 days.
• Participation in any other investigational study drug trial 30 days before dosing.
• Donation of whole blood from 3 months before dosing or of plasma from 30 days before dosing; receipt of blood products within 6 months before dosing.

HI Participants:

• Any acute or chronic non-hepatic condition that would limit the participant's ability to participate in this study.
• Any other unspecified reason that would make the participant unsuitable for enrollment.
• Any screening laboratory evaluation outside the laboratory reference ranges not related to HI.
• Fluctuating or rapidly deteriorating hepatic function within the screening period and up to 30 days prior to Day 1.
• History of chronic liver disease due to Wilson's disease.
• History of liver or other solid organ transplants.

Healthy Participants:

• Clinical laboratory evaluations outside of the reference range at Screening or check-in.
• Evidence of acute or chronic liver disease.
• Use of any prescription medications/products within 14 days prior to dosing.
• Use of over-the-counter, nonprescription preparations within 7 days prior to dosing.
• Evidence of chronic HBV or chronic HCV infection.