This phase I, open-label, single-dose study evaluated the pharmacokinetics, safety, and tolerability of renally excreted drug dexpramipexole in subjects with normal and impaired renal function, i.e. mild, moderate, severe renal impairment, or end-stage renal disease (ESRD) requiring hemodialysis when matched by age and sex. Dexpramipexole area under the curves (AUCs), but not Cmax, were significantly increased with the severity of renal impairment after a single dose administration. The geometric mean ratio of dose-normalized AUC(0–72) was 1.4, 1.7, 2.7, and 4.5, respectively, in mild, moderate, severe renal impairment, and ESRD subjects when compared to healthy subjects. There was a strong association between renal function (eGFR) and dexpramipexole CLr. The slope (90% confidence interval(CI)) of eGFR and renal clearance (CLr) in the regression model was 3.1 (2.4, 3.7). Dexpramipexole elimination in ESRD subjects during both dialysis and non-dialysis (i.e., interval between dialysis) was insignificant. Single 75 mg and 150 mg doses of dexpramipexole were well tolerated, and the safety profile was comparable across renal function groups. Extensive drug accumulation may occur with repeated dosing in patients with significant renal impairment. It is recommended that dexpramipexole not to be given to patients with severe renal impairment or in those with ESRD.