Ribi ImmunoChem Research Inc. announced Tuesday thatenrollment has been initiated in a Phase II human clinicalstudy to evaluate the prophylactic use of MPL (R)-Cimmunomodulator in heart bypass patients to prevent orreduce post-ischemic cardiac dysfunction.

The Phase II clinical testing of MPL-C in coronary arterybypass graft (CABG) surgery patients at risk of experiencingpost-bypass ischemia-reperfusion dysfunction will beconducted at up to four study centers. The randomized,placebo-controlled, double-blinded study involvesapproximately eight dose levels of MPL-C administered topatients prior to CABG surgery. Up to 48 patients will beenrolled; each dose level is expected to accrue six patients.

MPL, or monophosphoryl lipid A, is an attenuated form of theendotoxin produced by Gram-negative bacteria and thus apotentially potent activator of the immune system.

"Animal studies to date have suggested positive benefits; weare hopeful these observations can be duplicated in humans,"said Robert Ivy, chief executive officer, president and chairmanof Ribi (NASDAQ:RIBI) of Hamilton, Mont. "We will use thisstudy to assess the safety and biological activity of MPL-C inthis patient group. "

Cardiac ischemia-reperfusion dysfunction is believed to occurwhen the heart muscle undergoes an extended period ofischemia (deprivation of blood and thereby oxygen) during anevent such as a heart attack, cardiovascular surgery or cardiactransplantation, followed by reperfusion (return of blood flow).

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