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Concerning the mechanism of pexelizumab's benefit in acute myocardial infarction
Paul W Armstrong1, Kenneth W Mahaffey, Wei-Ching Chang
1The University of Alberta, Edmonton, Alberta, Canada. paul.armstrong@ualberta.ca
Insights
Pexelizumab reduced mortality in ST-elevation myocardial infarction (STEMI) patients undergoing angioplasty, particularly those with hemodynamic compromise. The benefit was not linked to infarct size or reperfusion, suggesting novel mechanisms of action.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Trials
Background:
- The COMplement inhibition in Myocardial infarction treated with Angioplasty (COMMA) trial found pexelizumab reduced mortality in myocardial infarction (MI) patients.
- This benefit occurred despite no change in MI size, prompting further investigation into its mechanisms.
Purpose of the Study:
- To investigate if the mortality benefit of pexelizumab in ST-elevation myocardial infarction (STEMI) patients is associated with baseline characteristics, treatment timing, or reperfusion.
- To explore potential modulators of clinical benefit in STEMI patients treated with pexelizumab.
Main Methods:
- Randomized trial of 814 STEMI patients undergoing percutaneous coronary intervention (PCI).
- Three groups: placebo, pexelizumab bolus, and pexelizumab bolus with infusion.
- Assessed mortality, creatine kinase-myocardial band (CK-MB) area under the curve, ST resolution, and hemodynamic status.
Main Results:
- Pexelizumab bolus with infusion was associated with sustained low mortality during the randomization window.
- A significant mortality benefit was observed in patients with high hemodynamic compromise (heart rate ≥ 90 bpm, systolic blood pressure ≤ 118 mm Hg).
- Clinical benefit was independent of infarct size, ST resolution, or reperfusion evidence.
Conclusions:
- The mortality benefit of pexelizumab in STEMI patients may be mediated by mechanisms beyond infarct size reduction.
- Novel pathways, potentially including apoptosis reduction, could explain the observed clinical benefits of pexelizumab.
Background:
The COMplement inhibition in Myocardial infarction treated with Angioplasty (COMMA) trial previously demonstrated an unexpected dose-dependent reduction in 90-day mortality after bolus/infusion of pexelizumab despite no reduction in the primary end point of myocardial infarction (MI) size. We examined whether the mortality benefit was related to established modulators of clinical benefit such as baseline demographics, time to treatment from symptom onset, myocardial perfusion post-percutaneous coronary intervention (PCI), and extent of ST resolution.
Methods And Results:
Eight hundred fourteen patients were randomized into 3 groups; (1) placebo, (2) pexelizumab bolus 2.0 mg/kg and placebo infusion for 20 hours, and (3) pexelizumab bolus 2.0 and 0.05 mg/kg per hour infusion for 20 hours commencing 4 hours after the bolus. Subjects presented with ST elevation MI within 6 hours of symptom onset and underwent PCI, creatine kinase (CK), and CK-MB measurements taken sequentially to define CK-MB area under the curve (AUC) and sequential ECG's defined ST resolution and QRS infarct size. Whereas mortality for both placebo and bolus pexelizumab groups rose during later time after presentation, it remained low and did not change appreciably during the 6-hour randomization window when patients received pexelizumab bolus infusion. Amplification of the mortality benefit was evident in patients with the highest quartile of hemodynamic compromise, that is, heart rate > or = 90 beat/min and systolic blood pressure < or = 118 mm Hg (3.2% vs 11.3% P = .004). A significant interaction between treatment assignment and hemodynamic status (P = .013) existed after adjusting for age, race, and MI location. Clinical benefit was not related to infarct size, extent of ST elevation, or evidence of angiographic or electrocardiographic reperfusion.
Conclusions:
These data raise the possibility that the clinical benefit of pexelizumab is mediated through novel pathways such as reduction in apoptosis or other mechanisms.
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