Myogen, Inc., a biopharmaceutical company focused on the discovery, development and commercialization of small molecule therapeutics for the treatment of cardiovascular disorders, has announced that two abstracts describing the effects of ambrisentan in patients with pulmonary arterial hypertension (PAH) were selected for presentation at ATS 2005, San Diego, the annual International Conference of the American Thoracic Society.

These abstracts summarize additional results from the Phase II study of ambrisentan in 64 patients with PAH (AMB-220) and the subsequent open-label extension study (AMB-220-E). One-year follow-up safety and efficacy results, as well as comparable effects of ambrisentan in WHO functional Class II and Class III PAH patients, will be presented.

The one-year data demonstrate that ambrisentan produced a significant and durable benefit on exercise capacity and other clinical measures of PAH. These data also indicate a survival benefit to patients treated with ambrisentan when compared with predicted survival based on the National Institutes of Health Registry formula. Data from the second abstract demonstrate that WHO Class II and III PAH patients have significant and comparable improvement in exercise capacity, which suggests that the effects of ambrisentan are not limited by a "ceiling effect" in patients with less severe PAH symptoms, Myogen said in a release.

Myogen completed "AMB-220 - A Phase II, Randomized, Double-Blind, Dose-Controlled, Dose-Ranging, Multi-centre Study of Ambrisentan Evaluating Exercise Capacity in Patients with Moderate to Severe Pulmonary Arterial Hypertension" in September 2003 and the initial study results were presented at ATS 2004, Orlando in May 2004. This study demonstrated a statistically significant increase in the primary efficacy endpoint, change from baseline in the 6-minute walk distance after 12 weeks of treatment, for all dose groups evaluated. Clinically meaningful improvements were observed in several secondary endpoints, including dyspnea (breathlessness) score, WHO functional class and cardiopulmonary hemodynamics. The subsequent open-label extension study titled, "AMB-220-E - An Open-Label, Long-term Study of Ambrisentan in Pulmonary Hypertension Subjects Having Completed Myogen Study AMB-220," remains on going with a mean ambrisentan exposure of nearly two years.