 - Subjects with sickle cell disease who smoke 10 cigarettes per day; have hemoglobin level 6 gdL or 10.4 gdL ULN appropriately corrected for gender for Cohort 15 at screening; have aspartate aminotransferase AST 4x upper limit of normal or alanine aminotransferase ALT, or alkaline phosphatase ALK 3x upper limit of normal reference range ULN at screening; have moderate or severe renal dysfunction 