Background We investigated whether the effects of adjunctive therapy with intracoronary urokinase would be noninferior to those of intracoronary tirofiban in primary percutaneous coronary intervention (PCI) for patients with ST-elevation myocardial infarction (STEMI)Methods A total of 490 patients with acute STEMI undergoing primary PCI were randomized to intracoronary bolus of tirofiban (10 μg/kg; n=247) or urokinase (250 kU/20 ml; n=243).Levels of P-selectin, vWF, CD40L and serum amyloid A (SAA) in the coronary sinus were measured before and after intracoronary administration.The primary endpoint was the rate of complete (≥70％) ST-segment-resolution (STR) at 90 min post-intervention.We assumed a 59％ complete STR rate in the intracoronary tirofiban group, and the noninferiority margin was set to 15％.The secondary endpoints included corrected TIMI frame count (cTFC), left ventricular ejection fraction (LVEF), and major adverse cardiac events(MACE) at 6-month follow-up.