The primary objective of this study is to evaluate the safety and tolerability of firsocostat in adults with nonalcoholic steatohepatitis (NASH).

Key Inclusion Criteria:

• Meets all of the following conditions:

  • A clinical diagnosis of nonalcoholic fatty liver disease (NAFLD)

  • Screening magnetic resonance imaging - proton density fat fraction (MRI-PDFF) with ≥ 8% steatosis

  • Screening magnetic resonance elastography (MRE) with liver stiffness ≥ 2.5 kPa

    • OR

  • A historical liver biopsy consistent with NASH and non-cirrhotic fibrosis

• Platelet count ≥ 100,000/mm^3

• Creatinine Clearance (CLcr ) as calculated by the Cockcroft-Gault equation ≥ 60 ml/min

Key Exclusion Criteria:

• Pregnant or lactating females

• Alanine aminotransferase (ALT) > 5 x upper limit of the normal range (ULN)

• Other causes of liver disease including autoimmune, viral, and alcoholic liver disease

• Cirrhosis of the liver

  • Prior history of decompensated liver disease, including ascites, hepatic encephalopathy or variceal bleeding

• Body mass index (BMI) < 18 kg/m^2

• International normalized ratio (INR) > 1.2 unless on anticoagulant therapy

• Total bilirubin > 1 x ULN, except with diagnosis of Gilbert's syndrome

NOTE: Other protocol defined Inclusion/ Exclusion criteria may apply.