Potassium Correction for RAAS Optimization in Chronic Kidney Disease

The PROMISE trial is a randomized, double-blind, placebo controlled cross-over trial where individuals are participating for 36 weeks. The trial consists of a 6-week run-in period, followed by two 12-week study periods, separated by a 6-week washout period.

First, during a run-in period, each participant will be converted from their ACEi/ARB dose to irbesartan 150 mg once daily. Individuals who already used irbesartan 150mg once daily before trial participation will remain on this dose during the run-in period. After six weeks, blood and 24-hour urine samples will be collected (baseline visit) and participants will be randomized to patiromer or placebo (start of study period A). The participant, research team, and treating physician will be blinded to treatment allocation (patiromer or placebo), while irbesartan will remain open-label.

At one week after start of study period A and B, participants will perform a home blood pressure measurement and visit a local lab to verify the plasma potassium level (safety visit), in combination with a scheduled phone consultation. The following actions may be taken: 1) If plasma potassium is \>5.0 mmol/L or eGFR is \>25% lower than baseline, the dose of irbesartan will be reduced to 150 mg/d and remain so during the remainder of the study period; 2) If systolic blood pressure is \<110 mmHg, the participant has symptoms of hypotension, and plasma potassium is \<5.0 mmol/L, antihypertensive co-medication may be adjusted, if applicable. If there is no antihypertensive co-medication that can be adjusted, the irbesartan dose will be reduced to 150 mg/d during the remainder of the study period.

At six weeks after start of the study period, there will be an in-hospital study visit. Blood samples will be collected, and office blood pressure will be measured. Any of the same two actions as described above may be taken in case of hyperkalaemia, severe acute kidney function decline or hypotension, respectively.

At the end of each 12-week study period, blood and 24-hour urine samples will be collected, and home (as well as office) blood pressure will be measured to establish the study endpoints. In addition, the study medication (patiromer/placebo) will be stopped and irbesartan dose will be reduced (or maintained) at 150 mg once daily. After a 6-week washout period, the second baseline will take place (measurements identical to the first baseline), which marks the start of study period B. During study period B, participants who had been randomized to patiromer in period A will now receive placebo and vice versa. The measurements during study period B will be identical to period A. At 12 weeks after the start of study period B, the protocol is completed and patients will return to their original medication.