A 70-year-old man with chronic kidney disease stage 3b (eGFR 35 mL/min/1.73 m²) and hypertension is found to have persistent albuminuria with urine albumin-to-creatinine ratio 45 mg/mmol. His blood pressure is 148/88 mm Hg on amlodipine. What is the most appropriate next step to slow progression of kidney disease?