• Patients must present serum potassium levels of 5.5-6.5 mEq/L at patient selection visit (V0)

• Patients must present serum potassium levels of 5.0-6.5 mEq/L at randomization visit (V1).

• Provision of patient or legal representative informed consent prior to any study specific procedures.

• Individuals receiving background standard of care for HF and treated according to locally recognized guidelines. Specific treatment should include RAASi and/or MRA treatment at first consultation and at least should have been stable for ≥ 4 weeks at maximum tolerated doses.

• Patients with CKD not on dialysis (Stages 2-5: estimated glomerular filtration rate (eGFR) between 15-60 ml/min/1,73m2 or eGFR between 60-90 ml/min/ 1.73 m2 with albuminuria/creatinuria (\> 30 mg/g) in the previous three months). The estimated GFR can be reported by the laboratory or calculated by the researcher with serum creatinine, age, and sex (CKD-EPI equation).

• 18 years at the time of signing ICF.

• Negative pregnancy test (urine or serum) for female subjects of childbearing potential.

• Female subjects must be 1 year post-menopausal, surgically sterile, or using an acceptable method of contraception (an acceptable method of contraception is defined as a barrier method in conjunction with a spermicide) for the duration of the study (from the time they sign ICF) and for 3 months after the last dose of SZC. In addition, oral contraceptives, approved contraceptive implant, long-term injectable contraception, intrauterine device, or tubal ligation are allowed. Oral contraception alone is not acceptable; additional barrier methods in conjunction with spermicide must be used.