Evaluate the Pharmacokinetics of GS-9876 in Subjects with Impaired Renal Function

Cohort 1 (Moderate Renal Impairment): single oral dose of GS-9876 20 mg (2 × 10 mg tablet) in a fasted state on Day 1. Adaptive Cohort 2 (Severe Renal Impairment): single oral dose of GS-9876 20 mg (2 × 10 mg tablet) in a fasted state on Day 1. Adaptive Cohort 3 (Mild Renal Impairment): single oral dose of GS-9876 20 mg (2 × 10 mg tablet) in a fasted state on Day 1. Based on safety and PK results from subjects with moderate renal impairment (Cohort 1), subjects with severe renal impairment (Cohort 2) and/or mild renal impairment (Cohort 3) will be enrolled. Cohorts 2 and 3 may not be enrolled or may be enrolled sequentially or in parallel, as governed by safety and PK data in Cohort 1. Dose administered following an overnight fast of at least 8 hours (no food or drink except water), study drug will be administered in the morning with 240 mL of water. Subjects will continue to fast until after collection of the 4-hour PK sample, relative to study drug dosing. Additionally, subjects will be restricted from water consumption 1 hour before until 2 hours after dosing, except for the 240 mL given with the study treatment. The investigator will maintain an accurate inventory of all study drug(s). Each dose of the study drug(s) administered at the study center will be administered by qualified study center staff. The dose of study drug(s) administered to subjects in the clinic under the supervision of staff will be accurately recorded, which indicates the date and quantity of each dosage formulation dispensed to individual subjects. Used and unused study drug supplies, including empty containers, are to be returned to the shipping facility from which it came for destruction following drug accountability and drug inventory reconciliation.