A 68-year-old man with type 2 diabetes presents for review. His latest HbA1c is 68 mmol/mol. He is currently taking metformin 1g BD and gliclazide 80mg BD. His BMI is 31 kg/m², and eGFR is >60 mL/min/1.73m². He has no history of cardiovascular disease or heart failure. According to NICE NG28, what is the most appropriate next agent to add?