Evaluation of HepQuant SHUNT to Assess Liver Disease; Substudy Within GS-US-416-2124

The main study is a Phase 2, double blind, proof-of-concept, randomized study evaluating the safety, tolerability, and biological activity of GS-4997 in combination with prednisolone, compared to prednisolone alone, in subjects with severe, histologically-confirmed AH. This substudy uses the HepQuant SHUNT Liver Diagnostic test to assess severity of disease at baseline and to track disease progression or improvement over the 24 weeks of the study. The HepQuant SHUNT test will be performed at baseline (Day 1) and at Weeks 1, 2, 4, 12, and 24 regardless of treatment Arm. GS-4997 Dose and Mode of Administration. Subjects will be randomized 1:1 to either: * Treatment Group A: GS-4997 18 mg (1 x 18 mg tablet) AND prednisolone 40 mg (4 x 10 mg tablets), both administered orally once daily * Treatment Group B: GS-4997 placebo (1 tablet) AND prednisolone 40 mg (4 x 10 mg tablets), both administered orally once daily