This is the phase 3 randomized, double-blind, placebo-controlled clinical study to evaluate the efficacy and long-term safety of SAL067 in T2DM patients uncontrolled by metformin, comprising 24 weeks of double-blind treatment period followed by an open-label treatment period, making up a total of 52 weeks.

All eligible subjects would enter the 24 weeks of double-blind treatment period and were randomized into the SAL067 group (12 mg once daily) or placebo group at a 2:1:1 ratio. After 24 weeks of double-blind treatment, subjects would enter the extended open-label treatment period. Subjects in the placebo group were to be switched to SAL067 (12 mg once daily) treatment, while patients in the SAL067 groups continued the same treatment until the end of the whole 52 weeks.

Inclusion Criteria:

1. Type 2 diabetes patients who meet the diagnostic criteria for diabetes issued by the World Health Organization (WHO) in 1999;
2. Men or women aged 18 to 75 years old at the day of signing the informed consent;
3. Body mass index: BMI 19kg/m2 to 35kg/m2, [BMI=weight (kg)/height 2 (m2)];
4. Subjects treated with metformin≥ 1500mg/day constantly for at least 8 consecutive weeks before screnning;
5. Glycated hemoglobin (HbA1c): Screening period: HbA1c 7.5% to 10.5% (tested by the research center), when randomly enrolled: HbA1c 7.0% to 10.0% (central laboratory test) Measurement);
6. Screening period and random time fasting blood glucose <=13.9mmol/L.

Exclusion Criteria:

1. Drug compliance during the introduction period <80% or >120%;

2. Use other hypoglycemic drugs other than test drugs during the introduction period;

3. The patient may have any contraindications, allergies or hypersensitivity to fuglitagliptin (including study drug and placebo) or its excipients, DPP4 drugs, metformin;

4. Before screening, have any of the following endocrine-related medical history or evidence:

   • Diabetes other than type 2 diabetes, such as type 1 diabetes, single-gene mutation diabetes, diabetes caused by pancreatic injury or secondary diabetes, such as diabetes caused by Cushing's syndrome or acromegaly;
   • diabetic ketoacidosis, hyperglycemia and hyperosmolarity, lacticacidosis and other acute complications of diabetes within 6 months before screening;
   • severe hypoglycemia episodes (such as sleepiness caused by hypoglycemia, unconsciousness, nonsense, and even coma), or a serious history of unconscious hypoglycemia;

5. Before screening, there is a history or evidence of any of the following diseases:

   • Unstable angina, stroke or transient ischemic attack, myocardial infarction, coronary artery bypass graft or percutaneous coronary intervention (diagnostic angiography is allowed of);
   • Decompensated heart failure before screening (New York Heart Association NYHA heart function grades III and IV, persistent and clinically significant arrhythmia;
   • A history of acute and chronic pancreatitis, symptomatic gallbladder disease or history of pancreatic injury, etc. may lead to high risk factors for pancreatitis.

Double-blind