Clinical Brief

Two Trials of a New Platelet Receptor Inhibitor

The results of the platelet receptor inhibition for Ischemic Syndrome Management (PRISM) trial and PRISM in Patients Limited to very Unstable Signs and symptoms (PRISM-PLUS) trial were presented on March 17, 1997, at the ACC Annual Scientific Sessions. PRISM compared 1615 patients with unstable angina (including non-Q MI) treated with 48 hours of intravenous tirofiban (glycoprotein IIB/IIIa blocker) to 1616 heparin treated patients. All patients also received aspirin. PRISM patients had to have either ECG changes or increased cardiac enzymes or a history of coronary artery disease. After 48, hours the tirofiban-treated patients exhibited a 36% reduction in the combined primary end point of death, MI, and refractory ischemia (3.8% tirofiban vs 5.3% on heparin). At 30 days, mortality was 39% less on tirofiban. PRISM-PLUS patients had ECG changes or elevated cardiac enzymes. All patients received aspirin, and 773 received tirofiban intravenously for 96 hours vs. 797 who received only heparin. Tirofiban reduced the combined primary end point of death, MI, and refractory ischemia at seven days by 34% and at 30 days by 31%. Also, it decreased the risk of death and MI at seven days by 44% and the risk of MI at seven days by 47%. The authors of both studies concluded that tirofiban’s beneficial effect in unstable angina was better than expected and a tremendous advance. Clearly, this is more highly positive data on this new class of agents. While some of these agents are available now for intravenous use in high-risk patients, their full potential will not be realized until an oral agent is developed. —mhc