A 68-year-old woman with heart failure with reduced ejection fraction (left ventricular ejection fraction 30 percent) remains symptomatic with exertional dyspnoea despite maximally tolerated doses of an angiotensin receptor neprilysin inhibitor, a beta-blocker, and a mineralocorticoid receptor antagonist. She has type 2 diabetes and an estimated glomerular filtration rate of 55 mL per minute per 1.73 m2. According to the 2021 CCS heart failure guideline update, which additional medication should be added to reduce mortality and hospitalisation?