A 59-year-old man with type 2 diabetes (duration 8 years), hypertension and dyslipidaemia attends for review. His latest HbA1c is 8.4% (68 mmol/mol) despite metformin 1 g twice daily. BMI is 32 kg/m2, eGFR 80 mL/min/1.73 m2. According to the RACGP diabetes handbook, which additional agent is preferred to improve glycaemic control and provide cardiovascular benefit?