A 52-year-old man with obesity (BMI 32 kg/m²) is newly diagnosed with type 2 diabetes mellitus after HbA1c is 7.6% (60 mmol/mol) on two occasions. He has no symptoms, no cardiovascular disease and eGFR is 80 mL/min/1.73 m². Lifestyle modification has been discussed. According to Australian general practice diabetes guidelines, what is the most appropriate initial pharmacological therapy?