ICOS Announces Results of Pafase and LeukArrest Clinical Trials.

Business Editors

BOTHELL, Wash--(BUSINESS WIRE)--April 20, 2000

ICOS Corporation (Nasdaq:ICOS) announced today results from advanced clinical trials of two product candidates. A Phase 2 trial of Pafase(TM) demonstrated striking clinical benefit in critically ill patient populations. Additionally, ICOS reported the results of an interim analysis from the Phase 3 trial with LeukArrest(TM) in patients following an ischemic stroke.

The Pafase(TM) study was a randomized, double-blind, placebo-controlled trial conducted in 33 U.S. medical centers that evaluated two Pafase(TM) doses in 240 patients with severe sepsis or severe traumatic injuries at risk for the development of ARDS (acute respiratory distress syndrome). Both dose groups showed quantifiable differences. The results that follow represent one of the Pafase(TM) dose groups as compared to placebo.

Treatment with Pafase(TM) in patients that were at risk for the development of ARDS resulted in a statistically significant reduction of death compared to placebo: for 28-day all cause mortality, the death rate with Pafase(TM) was 14.5% vs. 28.4% for placebo (p less than or equal to 0.034). This decreased mortality was accompanied by a statistically significant reduction in the incidence of ARDS (ARDS: 23.8% for Pafase(TM) vs. 37.0% for placebo, p less than or equal to 0.049) and a trend toward a reduction in median length of stay in the intensive care unit (10 days for Pafase(TM) vs. 16 days for placebo).

The results for the two patient populations can be reported separately for the same dose group. In patients with severe sepsis, the reduction in 28-day all cause mortality was statistically significant with a death rate of 21.4% with Pafase(TM) vs. 44.2% with placebo (p less than or equal to 0.026), the incidence of ARDS was 35.6% with Pafase(TM) vs. 48.8% with placebo, and the median length of stay in the intensive care unit was 11 days with Pafase(TM) vs. 20 days with placebo. In patients with severe traumatic injuries, 28-day all cause mortality was 5.9% with Pafase(TM) vs. 10.5% with placebo, the incidence of ARDS was 8.6% with Pafase(TM) vs. 23.7% with placebo, and the median length of stay in the intensive care unit was 8.0 days with Pafase(TM) vs. 15.5 days with placebo.

Administration of Pafase(TM) to patients with severe sepsis or severe traumatic injuries was safe and well tolerated. No serious treatment-related adverse events attributable to Pafase(TM) were reported in the study.

"This study is the only one to demonstrate a decrease in the incidence of ARDS in severely injured trauma patients as well as a significant decrease in mortality in septic patients," commented Michael Metzler, M.D. of the University of Missouri School of Medicine and co-principal investigator. Daniel Schuster, M.D. of Washington University School of Medicine and co-principal investigator added, "The possibility of preventing ARDS is extremely important because of the high mortality associated with this disease. The reduction in mortality of septic patients is nearly 50% -- this is very striking and is among the highest ever suggested by any study."

ICOS has been testing Pafase(TM) in patients at risk for ARDS in this severe sepsis and traumatic injury trial, as well as a separate trial for severe acute pancreatitis patients also at risk for ARDS. The number of patients with severe sepsis or trauma is estimated to be 650,000 annually in the U.S. Severe acute pancreatitis afflicts less than 50,000 patients per year. "Our success with Pafase(TM) in patients with severe sepsis or traumatic injuries has prompted us to pursue only this indication with Pafase(TM)," said Paul Clark, ICOS Chairman and CEO. "We have elected not to complete our Phase 2 pancreatitis study so we can direct our resources where we have strong clinical results, where the commercial potential is the highest, and where we can enroll patients fastest."

"The decisions on Pafase(TM) are consistent with our strategy to have multiple clinical candidates, make early decisions and focus our resources on the candidates with the most commercial potential," continued Paul Clark. "We are pleased with our positive Pafase(TM) Phase 2 results on mortality and ARDS and will aggressively move forward to an early initiation of Phase 3 by the fourth quarter this year."

LeukArrest(TM) has been in a Phase 3 study that enrolled over 400 patients following an ischemic stroke. The results of an interim efficacy analysis failed to meet the Company's predefined criteria for success. "While LeukArrest(TM) was safe and well tolerated," Paul Clark said, "at the interim analysis it was clear that it was unlikely we could demonstrate an adequate clinical benefit by continuing the clinical study."

ICOS is discovering and developing new pharmaceuticals by seeking points of intervention in disease processes that may lead to more specific and efficacious drugs. The Company's research and drug development programs involve both acute and chronic conditions.

NOTE: This news release contains forward-looking statements that involve risks and uncertainties, including risks associated with clinical development, regulatory approvals, product commercialization and other risks described from time to time in the SEC reports filed by ICOS, including the most recently filed Form 10-K and Form 10-Q.