A 62-year-old man with a 15-year history of type 2 diabetes has an eGFR of 48 mL/min/1.73 m² and urine albumin-creatinine ratio 35 mg/mmol despite good blood pressure control on an ACE inhibitor. HbA1c is 7.4%. What is the most appropriate additional measure to reduce progression of diabetic kidney disease and cardiovascular risk?