• Patients must be 12 to 80 years old

• A diagnosis of primary FSGS, genetic FSGS, or FSGS of undetermined cause. Confirmed by kidney biopsy within 7 years of screening

• Must be either receiving an ARB at the maximal tolerated dose or willing to transition

• If taking corticosteroids, the dosage must be stable for ≥4 weeks prior to Screening and during Stabilization

• If taking aldosterone inhibitors, mineralocorticoid receptor antagonists, direct renin inhibitors, sodium-glucose co-transporter-2 (SGLT2) inhibitors, or endothelin receptor antagonists (ERAs, including dual antagonists), the dose and regimen must be stable for ≥12 weeks prior to Screening and during Stabilization

• 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.

• Estimated eGFR ≥25 and ≤120 mL/min/1.73 m2 at Screening for adults \& eGFR ≥25mL/min/1.73 m2 for adolescent patients (\<18 years)

• Seated blood pressure ≤160/100 mm Hg (mean of 3 values) (patients ≥18 years of age) or between the 5th and 95th percentile for age, sex, and height (patients \<18 years of age) at Screening

• Body weight ≥35 kg (all patients) AND a body mass index (BMI) ≤40 kg/m2 (patients ≥18 years of age) or between the 5th and 98th percentile for age and sex (patients \<18 years of age) at Screening.

⁃ A female patient is eligible to participate if she is not pregnant or planning to become pregnant during the study, not breastfeeding, and at least one of the following conditions applies:

∙ Is not of childbearing potential

‣ If of childbearing potential and beginning at menarche, agrees to use a highly effective method of contraception consistently during the treatment period.

⁃ A male patient with a female partner of childbearing potential is eligible to participate if he agrees to use acceptable contraception

⁃ A patient or parent/legal guardian (as appropriate) who is capable of giving signed informed consent, and where required, the patient is capable of providing assent.

• A patient or parent/legal guardian (as appropriate) who is capable of giving signed informed consent, and where required, the patient is capable of providing assent.

• Patients who have completed participation in the double-blind period, including the Week 104 visit, and who may derive benefit from (continued) treatment with DMX-200, and/or continued follow-up

• The patient received blinded Investigational Product throughout the duration of the double-blind period up to the Week 104 visit

• The patient continues to meet the contraceptive requirements