1 dose of placebo and 5 doses of active drug will be administered by subcutaneous (SC) injection

5 doses of placebo and 1 dose of active drug will be administered by subcutaneous (SC) injection

Tonlamarsen will be administered subcutaneously (SC) every 4 weeks during the randomized part of the study

Percent Change from baseline (Week 0) in plasma angiotensinogen (AGT) levels to Week 20

Change from baseline (Week 0) in mean office seated systolic blood pressure to Week 20

Incidence and severity of treatment emergent adverse events (TEAEs). Incidence of clinically significant abnormalities in laboratory assessments, ECGs and vital signs. Incidence of: (1) Hyperkalemia, defined as serum potassium >5.5 mmol/L. (2) Hypotension, defined as systolic blood pressure <90 mmHg, or systolic blood pressure <100 mmHg and symptomatic and/or requiring clinical intervention. (3) Renal dysfunction, defined as a decrease of eGFR >30% from baseline value. (4) Increased proteinuria, defined as UPCR >0.5 mg/mg from baseline value.