Key Inclusion Criteria:
1. The patient or parent/legal guardian (as appropriate) is willing and able to provide signed informed consent, and where required, the patient is willing to provide assent, prior to any screening procedures.
2. The patient has biopsy-proven primary focal segmental glomerulosclerosis (FSGS) or documentation of a genetic mutation in a podocyte protein associated with FSGS.
3. Sites within the US: The patient is male or female aged 8 to 75 years, inclusive. Sites outside the US: The patient is male or female aged 18 to 75 years, inclusive.
4. The patient has a urine protein/creatinine (Up/C) ≥1.5 g/g at screening.
5. The patient has an eGFR ≥30 mL/min/1.73 m2 at screening.
6. Women of childbearing potential (WOCBP) must agree to the simultaneous use of 2 medically accepted methods of contraception from Day 1/Randomization until 90 days after the last dose of study medication.
7. Males must be surgically sterile (more than 3 months post-vasectomy) or must agree to the use of medically accepted methods of contraception that are considered highly reliable from Day 1/Randomization until 90 days after the last dose of study medication.
Key Exclusion Criteria:
1. The patient has FSGS secondary to another condition.
2. The patient has positive serological tests of primary or secondary glomerular injury not consistent with a diagnosis of primary or genetic FSGS.
3. The patient has a history of type 1 diabetes mellitus, uncontrolled type 2 diabetes mellitus.
4. The patient has undergone any organ transplantation, with the exception of corneal transplants, or has received certain immunosuppressive medications.
5. The patient has a documented history of heart failure, coronary artery disease or cerebrovascular disease.
6. The patient has significant liver disease.
7. The patient is positive at screening for the human immunodeficiency virus (HIV) or markers indicating acute or chronic hepatitis B infection or hepatitis C infection.
8. The patient has a history of malignancy other than adequately treated basal cell or squamous cell skin cancer or cervical carcinoma within the past 2 years.
9. The patient has disqualifying laboratory abnormalities during a screening.
10. The patient is >18 years of age with a body mass index (BMI) >40, or is ≤18 years of age with a BMI in the 99th percentile plus 5 units at screening.
11. The patient has a history of alcohol or illicit drug use disorder.
12. The patient has a history of serious side effect or allergic response to any angiotensin II antagonist or endothelin receptor antagonist.
13. The female patient is pregnant, plans to become pregnant during the course of the study, or is breastfeeding.
14. The male patient plans to father a child during the course of the study.
15. The patient, in the opinion of the Investigator, is unable to adhere to the requirements of the study, including the ability to swallow the study medication capsules whole.