A Phase 1, multiple center, nonrandomized, open-label, parallel group study of a single oral dose of GBT440 administered in subjects with mild, moderate, or severe renal impairment disease and healthy subjects with normal renal function.

Up to 40 adult subjects will be enrolled. Safety and PK assessments will be performed at selected time points throughout the study.

Inclusion Criteria:

All subjects:

• Males or females, 18 to 80 years old
• Willing and able to give written informed consent

Subjects with renal impairment:

• Severe renal impairment (eGFR < 30 mL/min/1.73m2, not on dialysis)
• Moderate renal impairment (30 mL/min/1.73m2 = or < eGFR < 60 mL/min/1.73m2)
• Mild renal impairment (60 mL/min/1.73m2 = or < eGFR < 90 mL/min/1.73m2)

Healthy subjects:

• Match in age, gender and body mass index with renal impaired subjects
• Healthy and without clinically significant abnormalities in vital signs, ECGs, physical exam, clinical laboratory evaluations, medical and surgical history

Exclusion Criteria:

All subjects:

• Participation in another clinical trial of an investigational drug (or medical device) within 30 days of the last dose of investigational drug or 5 half lives whichever is longer, prior to screening, or is currently participating in another trial of an investigational drug (or medical device)
• Any signs or symptoms of acute illness at screening or Day -1
• History or presence of clinically significant allergic, hematological, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, or neurological disease

Subjects with renal impairment:

- History of clinically significant hepatic disease e.g. hepatitis, cirrhosis and or liver enzymes (ALT, AST, GGT and total bilirubin) > 5 times the upper limit of normal within the past year