(RTTNews) -  Monday, Gilead Sciences Inc. (GILD: News ) in association with GlaxoSmithKline Plc (GSK: News , GSK.L), announced plans for a Phase-IV clinical trial to evaluate first-line combination use of ambrisentan and tadalafil, in patients with pulmonary arterial hypertension, as compared to monotherapy. The study is due to begin enrollment in 2010, subject to regulatory and other approvals.

The international, event-driven -morbidity and mortality- multi-center study dubbed AMBITION will be conducted as a double-blind clinical trial in more than 300 treatment-naive pulmonary arterial hypertension or PAH patients, randomized to receive either the combination of ambrisentan and tadalafil or monotherapy with either of the drugs. The company believes results of the study will answer "one of the most important outstanding clinical questions" of first-line combination therapy versus monotherapy in PAH.

Ambrisentan, an endothelin receptor antagonist, was approved under the trade name Letairis by the FDA on June 15, 2007. The drug is used as a once-daily treatment for PAH, classified by the World Health Organization or WHO as Group I, in patients with WHO functional class II or III symptoms. Letairis, marketed by Gilead, earned $112.9 million in net sales for 2008, a five-fold increase from $21.0 million in 2007.

Tadalafil is a PDE5 inhibitor, marketed as Cialis by Lilly ICOS LLC, the joint venture of ICOS Corp. and Eli Lilly and Co. (LLY: News ). Initially approved for treating erectile dysfunction in December 2003, Cialis won the FDA approval in May 2009 for the treatment of pulmonary arterial hypertension. The drug earned $1.45 billion for Eli Lilly in 2008, a 26% year-on-year increase from 2007 annual sales.

UK- based Glaxo also has a PDE5 inhibitor drug Levitra, generically known as vardenafil, for male erectile dysfunction. The drug has a lower half-life (4-5 hours) compared with Cialis (17.5 hours). The drug contributed GBP 60 million in 2008, up 12% from last year to the company.
PAH, (WHO Class I) is a debilitating disease characterized by constriction of the blood vessels in the lungs leading to high pulmonary arterial pressures, resulting in shortness of breath. The heart struggles to pump against these high pressures, ultimately leading to heart failure. The disease afflicts approximately 200,000 patients worldwide.

GILD is currently trading up 19 cents or 0.45%, at US$42.74 on 1.73 million shares, on the Nasdaq.

GSK is currently trading at U$40.58, down 58 cents or 1.41%, on 1.19 million shares on the NYSE. GSK.L closed at GBP 1,247 down GBP 3 on the London Stock Exchange, on Monday.

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by RTT Staff Writer

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