The US Food and Drug Administration has approved Letairis (chemical name ambrisentan) for treating a rare, life-threatening high blood pressure condition known as pulmonary arterial hypertension (PAH) that affects the arteries of the lungs. Letairis is an endothelin receptor antagonist (ERA).
PAH is where the small arteries in the lungs become narrow or get blocked which makes the heart pump harder to push the blood through for oxygenatation in the lungs. This can weaken the heart muscle which lessens its ability to pump enough blood through the lungs, causing PAH patients to have shortness of breath, tiredness and fatigue, fainting and dizzy spells which are made worse by exertion.
Patients eventually die of heart failure. Patients can get PAH with no known underlying cause, or as a result of other conditions such as connective tissue disease, congenital heart defects, cirrhosis of the liver and HIV infection.
There are about 200,000 people in the world with PAH.
Director of FDA’s Office of New Drugs, Dr John Jenkins said that:
“Letairis represents a valuable addition to the treatment alternatives for this orphan disease.”
“Letairis is similar to an existing drug, but offers the potential for fewer drug interactions,” he added.
The drug will only be available in 5 mg and 10 mg tablets to be taken once a day.
Because of the risks of liver injury and birth defects, the drug, which will be available this week in the US, will only be issued to patients through the Letairis Education and Access Program (LEAP).
LEAP is a restricted distribution program that helps patients learn about the risks of taking Letairis. Only pharmacies and prescribers registered with LEAP will be able to dispense and prescribe the drug, and even then only to patients who are registered and meet all the qualification criteria for LEAP.
The drug’s safety and efficacy were tested in two international clinical trials with 393 patients. It significantly improved patients’ ability to complete a six-minute walk, compared with placebo (a standard test). It also delayed the worsening of the pulmonary hypertension.
The most common side-effects include swelling of legs and ankles, congestion of nasal passages, sinusitis and getting red in the face (flushing).
Pregnant women, or women who may become pregnant should not take the drug because there is a risk of birth defects. Patients who take the drug are required to take monthly blood tests to check for liver injury.
In the US, Letairis is made by Gilead Sciences, a biopharmaceutical company with headquarters in Foster City, California, US. It got the rights to ambrisentan when it acquired Myogen Inc last year.
Outside the US GlaxoSmithKline holds the rights to ambrisentan.
This is the first time Letairis has been licensed in the US, and it was given a priority review, a fast track status reserved for drugs that treat conditions without current treatments. The FDA sets a timetable of 6 months within which it has to complete all the stages of the review and take action.
The FDA also gave the drug orphan status because it is for a rare condition, among other things, which qualifies the sponsor for tax credit and marketing support.
Written by: Catharine Paddock
Writer: Medical News Today