West Coast Editor

New York-based Pfizer Inc. won FDA approval for Revatio, its lower-dose form of sildenafil citrate for pulmonary arterial hypertension.

Better known as the active ingredient in Viagra, Pfizer's blockbuster compound for erectile dysfunction, oral sildenafil - with its ability to open blood vessels - goes up against Tracleer (bosentan), the dual endothelin receptor antagonist from Actelion Ltd., of Allschwil, Switzerland, approved in late 2001. (See BioWorld Today, Nov. 26, 2001.)

A report at the start of this year by analyst Ruth Brown at Decision Resources in Waltham, Mass., hailed Revatio's side effect profile. Brown told BioWorld Today the drug "has the potential to challenge bosentan in less severely ill patients," and - because it's likely to be less expensive - could find a place for itself as a therapy in combination with other PAH drugs.

Pfizer said nothing about pricing in its disclosure of approval, but predicted the drug would be in the hands of pharmacists in July.

PAH, characterized by dangerously high pressure in the blood vessels that lead from the heart to the lungs, afflicts about 100,000 people worldwide, who suffer symptoms that include difficulty breathing, dizziness and fatigue. Without treatment, they survive an average of less than three years after diagnosis.

Giving Revatio priority review, the FDA approved Pfizer's drug based on results from a 277-patient study showing patients in each of three dosage groups gained highly significant improvements in the six-minute walk distance. Since researchers found no differences among the Revatio doses, the approved amount is 20 mg three times daily.

Others recently in the news pursuing the PAH indication include Houston-based Encysive Pharmaceuticals Inc., which late last month filed a new drug application for its lead candidate, Thelin (sitaxsentan), also an endothelin receptor antagonist. (See BioWorld Today, May 26, 2005.)

One inhaled product for PAH is available - Ventavis (iloprost) - a prostacyclin from CoTherix Inc., of South Francisco, approved at the end of last year. CoTherix in-licensed the compound from Berlin-based Schering AG in the fall of 2003.

Pfizer's new drug, like Tracleer, is oral, which provides an advantage over the prostacyclin Remodulin (treprostinil sodium) from United Therapeutics Corp., of Silver Spring, Md., cleared in 2002 as a continuous subcutaneous infusion. Late last year, the FDA extended the Remodulin label to include an IV formulation and help the most severely ill PAH patients. But Remodulin is said to be more stable and more convenient than London-based GlaxoSmithKline plc's IV drug Flolan (epoprostenol).