The purpose of this study is to assess the efficacy of HSK7653 (as monotherapy) compared with placebo after 24 weeks, and the safety (up to 52 weeks) of HSK7653 in Chinese patients with Type 2 diabetes who are insufficient glycaemic control with diet and exercise.

The treatment period is composed of a 24-week double-blind period (week 1-24) and a 28-week open-label period (week 25-52). During the double-blind period, participants will receive 10 mg or 25 mg dose of HSK7653 and matching placebo, or placebo only. During the open-label period, all participants will receive 25 mg dose of HSK7653.

Inclusion Criteria:

• Age ≥ 18 and ≤ 75 years, Male and female patients;
• Type 2 diabetes mellitus;
• Control the blood glucose level only with diet and exercise in last 8 weeks;
• Did not receive regular long-term medication of oral hypoglycemic drugs or insulin within 1 year prior to informed consent;
• HbA1c in the range of ≥7.5 to ≤11.0% at screening;
• FPG < 15 mmol/L at screening;
• BMI (Body Mass Index) in the range of ≥ 18.0 kg/m² to ≤ 35.0 kg/m² at screening.

Exclusion Criteria:

• Diabetic ketoacidosis, hyperglycemia hypertonic state, serious complications of diabetes, myocardial infarction, stroke within 6 months prior to informed consent;
• History of severe endocrine disease, uncured cancer, acute pancreatitis prior to informed consent;
• Current hemoglobinopathy, uncontrolled hypertension, serious nephropathy or hepatopathy prior to informed consent;
• Serious gastrointestinal disease within 2 weeks prior to informed consent;
• Serious infection, trauma and surgery within 3 months prior to informed consent;
• History of treatment with Dipeptidyl-Peptidase 4 (DPP-4) inhibitor, Glucose-dependent insulinotropic polypeptide (GIP) or Glucagon-like peptide-1 (GLP-1) receptor agonist;
• Treatment with drugs that affect glucose metabolism within 8 weeks prior to informed consent;
• Hemoglobin (HGB) < 10.0 g/dL(100 g/L);
• Alcohol abuse within 6 months or drug abuse history within 5 years prior to informed consent;
• Active infectious diseases;
• Participation in another trial with an investigational drug or instrument within 3 months prior to informed consent;
• Women who are nursing or pregnant, or subjects with birth plans;
• Contraindication for metformin;
• Other protocol-defined inclusion/exclusion criteria.