This is a multicentre, 2-part, single-blind, randomised, withdrawal, placebo-controlled study, that includes a 4-week patiromer treatment phase (Part A) followed by an 8-week randomised placebo-controlled withdrawal phase (Part B) and a 2-week follow-up period.

In Part A, participants who meet all eligibility criteria will initiate patiromer at an oral dose of 8.4 g (1 packet/day). The dose will be adjusted based on the serum potassium (sK+) levels.

After the completion of part A, all the participants who meet the eligibility criteria for Part B will be randomised to receive patiromer or placebo. Participants will start Part B with the same dose of patiromer they were receiving at the end Part A. However, Patiromer dose may be up- or down-titrated based on sK+ levels.

The primary objectives of the study are:

Part A - To evaluate the efficacy of patiromer for the treatment of hyperkalemia in Chinese subjects.

Part B - To evaluate the effect of withdrawing patiromer on sK+ control. To determine if the treatment with patiromer will result in continued use of renin-angiotensin-aldosterone system inhibitor (RAASi) medications.

Inclusion Criteria:

• - Chinese subjects at least 18 years of age.
• - Chronic Kidney Disease (CKD) stage 3 and 4.
• - Mean of 2 measurement of serum potassium higher than 5.0 and lower than 6.5 mEq/L at baseline.
• - Subjects on any stable dose of at least 1 RAASi medication for at least 28 days before Day 0/baseline.
• - If on antihypertensive medication, have a stable dose for 28 days before Day 0/baseline.
• - Women of childbearing potential must agree to continue using contraception throughout the study and for 4 weeks after study completion.

Exclusion Criteria:

• - Any level of hyperkalemia at Day 0/baseline that, in the opinion of the Investigator, requires emergency intervention.
• - Type 1 diabetes or Type 2 diabetes mellitus with glycated haemoglobin (Hb A1c) higher than 10.0% at screening/Part A baseline.
• - History of acute renal insufficiency in the past 3 months prior to the beginning of the study.
• - Diseases affecting the hearth muscle and heart's ability to pump blood around the body
• - Major surgery including thoracic and cardiac within 3 months prior to the beginning of the study or anticipated need during study participation.
• - Heart or kidney transplant recipient or anticipated need for transplant during study participation
• - Diagnosis or treatment of a malignancy in the past 2 years before Day 0/baseline.
• - Use of potassium supplements, bicarbonate or baking soda in the last 7 days prior to Day 0/baseline.
• - Pregnant women or breastfeeding.