FREMONT, Calif., April 18 — Protein Design Labs, Inc. (PDL) has reported positive results from a Phase II clinical study, known as the SIRIUS II trial, of the natriuretic peptide ularitide in patients with decompensated congestive heart failure (DHF).

The SIRIUS II trial was a randomized, double-blind, placebo-controlled clinical trial conducted at 19 centers in Europe. Primary endpoints in the study were change in pulmonary capillary wedge pressure (PCWP) and change in dyspnea (shortness of breath) score, both at six hours. A total of 221 patients were randomized equally to receive ularitide 7.5, 15, or 30 ng/kg/min given intravenously as a 24-hour infusion, or placebo. In the assessment of the primary endpoints, ularitide significantly reduced PCWP (p&gt0.05) and improved dyspnea score (p&gt0.05) in all three dose groups compared to placebo. The main adverse events through day three were dose-dependent decreases in blood pressure compared to placebo. Serum creatinine levels were unchanged during and after ularitide treatment when compared to placebo. The incidence of serious adverse events was similar for all three treatment groups and the placebo group.

“Based on these encouraging data, we intend to further study ularitide as a potential treatment for patients with decompensated congestive heart failure,” said Steven Benner, M.D., Senior Vice President and Chief Medical Officer, PDL. “We have submitted an abstract summarizing these data for possible presentation at the Scientific Meeting of the Heart Failure Society of America to be held September 18-21 at Boca Raton, Florida. We may additionally submit an abstract to the European Society of Cardiology Congress to be held in Stockholm, Sweden, September 3-7.” Following these potential presentations, PDL expects to discuss its development strategy and future study timelines during an R&D Update to be scheduled for late September or early October 2005 in New York.

The SIRIUS II clinical trial was conducted by CardioPep Pharma GmbH. PDL has acquired from CardioPep, through a license agreement between CardioPep and ESP Pharma, Inc., PDL’s wholly-owned subsidiary, exclusive rights to conduct all subsequent development and exclusive marketing rights for ularitide for all indications in the United States, Canada, the European Union and Switzerland. To date, the clinical development of ularitide has taken place in Europe. A U.S. IND has not yet been filed by CardioPep.