Anti-inflammatory therapy with the experimental drug pexelizumab does not improve morbidity or mortality compared with standard treatment in the 30 days after angioplasty for acute myocardial infarction, according to a late-breaking clinical trial presented at the American Heart Association meeting.

The Assessment of PEXelizumab in Acute Myocardial Infarction (APEX AMI) Study involved 5,745 patients and was the largest ever done involving percutaneous coronary intervention following acute ST-elevation heart attack (STEMI), said Paul W. Armstrong, M.D., chair of the study and director of the Canadian VIGOUR Centre, professor of medicine at the University of Alberta and a cardiologist at University Hospital in Alberta, Canada.

The patients (average age, 61 years; 77 percent men) were treated at more than 296 medical centers in 17 countries. They were randomized to one dose of pexelizumab or placebo at 2 milligrams per kilogram body weight (mg/kg) for 10 minutes prior to the procedure, followed by an intravenous dose (0.05 mg/kg per hour) of drug or placebo during the following 24 hours.

For the primary endpoint of 30-day all-cause death, 3.92 percent of placebo patients had died compared to 4.06 percent of pexelizumab patients. A secondary endpoint was the combination of death, congestive heart failure or shock. The 30-day risk for the composite endpoint was 9.19 percent for placebo and 8.99 percent for pexelizumab.

Researchers also found no evidence of subgroup benefits based on time, age, gender, infarct location, or Killip Class. Killip Class is a classification system used in individuals with an acute heart attack to identify their risk level. Individuals with a low Killip class are less likely to die within the first 30 days after their heart attack than individuals with a high Killip Class.

“Smaller studies found that the drug could have reduced death by as much as two thirds although these estimates were imprecise,” Armstrong said. “It now appears that chance may have been a factor in the previous studies. In addition, the low placebo event rate (3.92 percent) may have hindered the ability to detect a treatment effect in this trial.”

Researchers said they had anticipated an event rate of 6.5 percent for that group.

Researchers also had some indications that standard care has improved since earlier studies addressed this question. For instance, patients who qualify for angioplasty seem to be getting it sooner based on unexpectedly low average times to intervention in this study. In addition, 36 percent of patients in this study were transferred from one medical facility to another to receive their procedure, indicating that angioplasty was applied to a broad cross section of patients.

“Despite the benefits of percutaneous coronary intervention in reopening blocked arteries, this intervention can lead to problems of its own,” Armstrong said. “This collateral damage, called reperfusion injury, is thought to occur through the body’s inflammatory and immune system response, which is what pexelizumab was designed to affect.”