A Study of the Efficacy and Safety of DMX-200 in Patients With FSGS Who Are Receiving an ARB

DOUBLE BLIND PERIOD Inclusion Criteria:

1. Patients must be 12 to 80 years old
2. A diagnosis of primary FSGS, genetic FSGS, or FSGS of undetermined cause. Confirmed bykidney biopsy or documentation of a genetic mutation in a podocyte protein associatedwith FSGS
3. Must be either receiving an ARB at the maximal tolerated dose or willing to transition
4. If taking corticosteroids, the dosage must be stable for ≥4 weeks prior to Screeningand during Stablization
5. If taking aldosterone inhibitors, mineralocorticoid receptor antagonists, direct renininhibitors, sodium-glucose co-transporter-2 (SGLT2) inhibitors, or endothelin receptorantagonists (ERAs, including dual antagonists), the dose and regimen must be stablefor ≥12 weeks prior to Screening and during Stablization
6. Urine PCR >1.5 g/g (>169.5 mg/mmol) or 24-hour total protein >1.5 g/day based on 24-hour urine collection during Screening.
7. Estimated GFR ≥25 mL/min/1.73 m2 at Screening
8. Seated blood pressure ≤160/100 mm Hg (mean of 3 values) (patients ≥18 years of age) orbetween the 5th and 95th percentile for age, sex, and height 29 (patients <18 years ofage) at Screening.
9. Body weight ≥35 kg (all patients) AND a BMI ≤40 kg/m2 (patients ≥18 years of age) orbetween the 5th and 98th percentile for age and sex (patients <18 years of age) atScreening.
10. A female patient is eligible to participate if she is not pregnant or planning tobecome pregnant during the study, not breastfeeding, and at least one of the followingconditions applies:
11. Is not of childbearing potential
12. If of childbearing potential and beginning at menarche, agrees to use a highlyeffective method of contraception consistently during the treatment period.
13. A male patient with a female partner of childbearing potential is eligible toparticipate if he agrees to use acceptable contraception
14. A patient or parent/legal guardian (as appropriate) who is capable of giving signedinformed consent, and where required, the patient is capable of providing assent.

Exclusion Criteria:

1. Has FSGS secondary to another condition.
2. History of type 1 diabetes mellitus, or uncontrolled type 2 diabetes mellitus (definedas glycated hemoglobin [HbA1c] >8%)
3. History of lymphoma, leukemia, or any active malignancy within the past 2 years
4. Active clinically significant hepatobiliary disease.
5. Documented history of heart failure (New York Heart Association Class III/IV) or amajor adverse cardiac event within 12 weeks prior to Screening.
6. Has a physical, medical, or psychological condition, that in the opinion of theInvestigator, may interfere with the evaluation the study.
7. The patient has a history of alcohol or illicit drug use disorder within 1 year priorto Screening.
8. Had a prior organ transplant or stem cell transplant, with the exception of cornealtransplant.
9. Positive screening assessment for viral hepatitis B surface antigen, or anti-hepatitisC virus antibody AND positive HCV RNA, or human immunodeficiency virus 1 and 2.
10. Serum potassium levels >5.5 mmol/L at Screening.
11. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) >2 × upper limitof normal (ULN) at Screening
12. Treatment with immunosuppressant biological drugs, calcineurin inhibitors,cyclophosphamide, azathioprine, or mycophenolate mofetil within 12 weeks prior toScreening.
13. History of serious side effects or allergic response to an angiotensin II antagonistor has a known sensitivity to any components in the Investigational Product.
14. Unable to swallow oral medication.
15. Prior participation in any Dimerix-sponsored DMX-200 clinical study.
16. Participation in a clinical study with an Investigational Product within 28 days or 5half-lives (whichever is longer) prior to Screening or plans to participate in anotherstudy during the course of this study.
17. Are study site personnel directly affiliated with this study and their immediatefamilies. OLE PERIOD Inclusion Criteria:
18. A patient or parent/legal guardian (as appropriate) who is capable of giving signedinformed consent, and where required, the patient is capable of providing assent.
19. Patients who have completed participation in the double-blind period, including theWeek 104 visit, and who may derive benefit from (continued) treatment with DMX-200,and/or continued follow-up
20. The patient received blinded Investigational Product throughout the duration of thedouble-blind period up to the Week 104 visit
21. The patient continues to meet the contraceptive requirements Exclusion Criteria:
22. The patient has met the criteria for permanent IP discontinuation or studydiscontinuation
23. Any safety concerns identified during the double-blind period which, in theInvestigator's opinion, may interfere with the patient's continued participationduring the OLE period.