How Tyvaso works
In PAH, the blood vessels of the lungs, the pulmonary arteries, are narrowed. This restricts blood flow through the lungs and causes abnormally high blood pressure in pulmonary arteries. Among other symptoms, this makes it more difficult for patients to exercise because of a lack of oxygen in the blood.
Prostacyclin, a molecule naturally produced by the body that dilates blood vessels is found at abnormally low levels in some PAH patients, and is thought to contribute to the development of the disease. Prostacyclin also stops platelets, a type of blood cell, from clumping together and potentially blocking arteries.
The active component of Tyvaso is a synthetic substance that mimics the action of prostacyclin. By binding to receptors on the cells of the arterial walls, it triggers the relaxing of the arterial wall muscles, making it easier for blood to be pumped through the lungs, and increases oxygen transport throughout the body.
Tyvaso in clinical trials
Results from TRIUMPH (NCT00147199), a double-blind, placebo-controlled, randomized Phase 3 clinical trial, were key in the FDA’s decision to approve Tyvaso for PAH treatment in July 2009.
TRIUMPH enrolled 235 PAH patients who were already taking Tracleer (bosentan) or Revatio (sildenafil citrate), to receive either Tyvaso or a placebo four times daily for 12 weeks. The trial assessed whether Tyvaso improved patients’ ability to exercise, measured by the six-minute walk test, compared with placebo. After 12 weeks, patients given Tyvaso saw an improvement of 20 meters in the distance walked in six minutes, a significant increase compared with the placebo group. The results were published in the Journal of the American College of Cardiology. The trial took place at 30 sites in the U.S., Europe, and Israel.
A total of 206 patients who completed the TRIUMPH trial enrolled in an open-label extension study to test the long-term safety of Tyvaso for up to two years. The results of this extension study, published in the Journal of Heart and Lung Transplantation, suggested that Tyvaso had a continued benefit on exercise ability and was well-tolerated long term.
The safety and effectiveness of Tyvaso as a treatment for pulmonary hypertension associated with other conditions is also being investigated. This includes a Phase 2/3 trial (NCT02630316) that is recruiting up to 314 participants to test Tyvaso as a therapy for pulmonary hypertension associated with interstitial lung disease (ILD).
The most common side effects of Tyvaso include cough, headache, throat irritation and pain, nausea, flushing of the face and neck, and fainting.
In October 2017, the FDA approved a third-generation nebulizer for the Tyvaso inhalation system called TD-300/A.
United Therapeutics also produces two other approved treprostinil formulations. These are marketed under the brand names Orenitram (extended release oral tablets) and Remodulin (administered as an injection into the vein or under the skin).
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