Gilead Sciences to Collaborate with GlaxoSmithKline in Phase IV Clinical Trial

In a release, the Company noted:

The study, Ambition (a randomized, double-blind, multicenter study of first-line combination therapy with AMBrIsentan and Tadalafil in subjects with pulmonary arterial hypertensION), will evaluate first-line combination use with ambrisentan, an endothelin receptor antagonist (ERA) and tadalafil, a PDE5 inhibitor, in patients with PAH. Ambrisentan is approved under the tradename Letairis (ambrisentan 5 mg and 10 mg tablets) as a once-daily treatment for PAH (WHO Group 1) in patients with WHO functional class II or III symptoms to improve exercise capacity and delay clinical worsening.

"The question of first-line combination therapy versus monotherapy is one of the most important outstanding clinical questions in PAH," said Lewis J. Rubin, MD, Professor of Medicine, University of California, San Diego. "As the first large, randomized clinical trial to address the efficacy of initial combination therapy in PAH, AMBITION has the potential to be a landmark study."

Ambition will be a double-blind, multicenter study, in which more than 300 treatment-naive PAH patients will be randomized to receive either the combination of ambrisentan and tadalafil or monotherapy (ambrisentan or tadalafil). Gilead and GSK are working with regulatory agencies and the PAH research community to finalize details of the study and plan to begin enrollment in 2010.

About Letairis

Letairis (ambrisentan) is an endothelin receptor antagonist that has a high affinity for the endothelin type-A (ETA) receptor. Activation of the ETA receptor by endothelin-1 (ET-1), a small peptide hormone, leads to vasoconstriction (narrowing of blood vessels) and cell proliferation. The clinical impact of high selectivity for ETA is not known. Endothelin concentrations are higher in the lung tissue of PAH patients, thus suggesting that ET-1 may play a critical role in the pathogenesis or progression of PAH.

PAH is a debilitating disease characterized by constriction of the blood vessels in the lungs leading to high pulmonary arterial pressures. These high pressures make it difficult for the heart to pump blood through the lungs to be oxygenated. Patients with PAH suffer from shortness of breath as the heart struggles to pump against these high pressures, causing such patients to ultimately die of heart failure. PAH can occur with no known underlying cause, or it can occur secondary to diseases such as connective tissue disease, congenital heart defects, cirrhosis of the liver and HIV infection. PAH afflicts approximately 200,000 patients worldwide.

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes therapeutics in areas of unmet medical need.

Full prescribing information for Letairis:

www.gilead.com and at http://www.letairis.com/downloads/LETAIRIS_prescribing_information.pdf

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