Efficacy and Safety of a Half-dose Bolus of r-SAK Prior to Primary PCI in ST-elevation Myocardial Infarction

Inclusion Criteria: 1. Age 18-75 years, weight ≥45 kg 2. Diagnosed as STEMI (meeting the following two conditions simultaneously) 1. Ischemic chest pain lasts ≥ 30 minutes 2. ECG indicates that ST-segment elevation of two or more contiguous precordial leads ≥ 0.1 mV, or ST-segment elevation of two or more contiguous precordial leads ≥ 0.2 mV 3. Time from onset of persistent chest pain to randomization ≤12 hours 4. Primary PCI expected to be performed ≥30 minutes, and ≤120 minutes Exclusion Criteria: 1. Cardiogenic shock 2. Active bleeding or known at high risk of bleeding (including grade Ⅲ or Ⅳ retinopathy or retinal gastrointestinal or urinary tract hemorrhage within the past 1 month) 3. Ischemic stroke or TIA in the past 6 months 4. History of hemorrhagic stroke 5. Known intracranial aneurysm 6. Severe trauma, surgery or head injury within 1 month 7. Suspected aortic dissection or infective endocarditis 8. Puncture with difficult hemostasis by compression within 1 month (e.g., visceral biopsy, compartment puncture) 9. Currently taking anticoagulants 10. Poorly controlled hypertension ( ≥180/110 mmHg) 11. Severe hepatic or renal impairment indicated by the consultation or previous history (glutamic-pyruvic transaminase or glutamic oxalacetic transaminase \>3 times upper limit of normal value; eGFR \<15 ml/min/1.73m\^2, calculated based on CKD-EPI) 12. Known allergy to r-SAK 13. Pregnancy, lactation, or planning for pregnancy 14. History of chronic total occlusion, myocardial infarction or CABG 15. Having taken antiplatelet drugs other than aspirin and ticagrelor, such as clopidogrel, prasugrel or cilostazol after the symptom onset 16. Patients with other conditions that made them unsuitable to be recruited at the discretion of the investigators