October 09 ,2013 | By Márcio Barra
Adempas (riociguat), a first-in-class oral soluble guanylate cyclase stimulator from Bayer, has been approved today by the FDA for the treatment of Pulmonary Artery Hypertension (PAH) and as the first approved treatment for Chronic ThromboEmbolic Pulmonary Hypertension (CTEPH).
“Adempas is the first in its drug class approved to treat pulmonary hypertension and the first drug of any class to be shown to be effective for patients with CTEPH,” said Norman Stockbridge, director of the Division of Cardiovascular and Renal Drug Products in the FDA’s Center for Drug Evaluation and Research.
The drug, reviewed under the FDA’s 6 months priority review program, is noteworthy as it is the first approved treatment for chronic thromboembolic pulmonary hypertension, a more severe subset of pulmonary hypertension characterized by blockage of large pulmonary arteries by acute and recurrent pulmonary emboli, and organisation of these blood clots, which affects between 2 and 4% of all PAH patients. No treatment was available until now for patients with this disease save for anticoagulation drugs with or without fibrinolysis.
In two pivotal trials, CHEST-1 and PATENT-1, PAH patients and CTEPH patients treated with Adempas showed improved exercise capacity, measured by the six minute walk test (6MWT).
Riociguat is the first stimulator of soluble guanylate cyclase (sGC) approved by the FDA. In patients with pulmonary arterial hypertension endothelial Nitric Oxide synthase, the enzyme that is responsible for the production of Nitric Oxide (a potent vasodilator), is expressed in reduced levels. The vasodilation mechanism of Nitric Oxide is dependent on its interaction withsGC, and if less Nitric Oxide is available to stimulate sGC, vasodilation is compromised in these patients. Riociguat skips the need for Nitric Oxide to stimulate sGC by directly stimulating sGC to relax muscle cells and promote vasodilation.
Other drugs approved for the treatment of Pulmonary Artery Hypertension include Actelion’s endothelin antagonist Tracleer (bosentan), which currently leads the market, with $1.6bn in sales last year; prostacylin drugs like United Therapeutics’ Remodulin (treprostinil); and PDE-5 inhibitors like Revatio (sildenafil, the active molecule of Viagra). None of these drug classes have proved particularly effective in treating CTEPH.
Bayer has also filed for approval of riociguat as a treatment for PAH and CTEPH in Europe in February and in Japan in May.