The past two weeks have been an exciting time for the treatment of PAH. Two drugs were approved by the FDA (Food and Drug Administration)—Adempas (Riociguat) and Opsumit (Macitentan). These drugs are the 12th and 13th to be approved for pulmonary arterial hypertension.
Adempas (Riociguat) Used to Treat PAH and Chronic Thomboembolic Pulmonary Hypertension
Adempas is the first in a new class of medications (soluble guanylate cyclase stimulators) approved by the FDA to treat PAH. It works by stimulating an enzyme inside cells called soluble guanylate cyclase. By increasing the activity of this enzyme, there is an increase in the production of cyclic GMP, which in turn leads to relaxation of the pulmonary arteries and improvements in pulmonary hypertension. The pathway by which Adempas works is similar to the way in which PDE5 inhibitors work but at an earlier point in the cascade. Two studies have been published recently in the New England Journal of Medicine that showed that Adempas improved exercise capacity and delayed clinical worsening in patients with PAH and chronic thromboembolic pulmonary hypertension. The most common side effects were head ache, stomach symptoms, swelling of the legs and low blood pressure. The medication is taken orally and the dose is gradually increased from 05.mg to a maximum of 2.5mg three times daily. This medicine is a teratogen meaning it can cause harm to a developing fetus. Women must use two methods of reliable birth control and have monthly pregnancy tests while taking the medication. Adempas has not become available commercially at this point and we expect it to be dispensed by a small network of specialty pharmacies.
Opsumit (Macitentan) Used To Treat Pulmonary Arterial Hypertension
Opsumit is the third endothelin receptor antagonist (ERA) approved by the FDA to treat PAH. It is considered to be a dual ERA meaning that it binds to and blocks the A and B receptors (similar to Tracleer). By blocking these receptors, Opsumit is able to delay clinical worsening by reducing the likelihood of hospitalization and the need for additional medications. There were also small increases in exercise capacity. The New England Journal of Medicine just published the results of the pivotal trial. This study involved 742 patients and took almost 4 years to complete. A dose of 10mg once daily by mouth was found to be effective and safe. The most common side effect was upper respiratory symptoms. An increased incidence of anemia (a decreased number of red blood cells) was also found. The medication is a teratogen. Women must use two methods of reliable birth control and have monthly pregnancy tests. Blood tests are required prior to starting this medication. Opsumit is expected to become available sometime in November 2013 and will only be available through specialty pharmacies.