Results From the AMBITION Study of First-Line Treatment With Letairis and Tadalafil in Pulmonary Arterial Hypertension Published in The New England Journal of Medicine
Letairis, a selective endothelin type-A receptor antagonist, and
tadalafil, a PDE5 inhibitor, are each approved in
“The only other published, large-scale, event-driven study to date in
PAH compared an endothelin receptor antagonist to placebo in patients
who were either treatment-naïve or on background therapy, however, all
patients in AMBITION received an approved therapy for PAH,” said
AMBITION was a multicenter, randomized, double-blind phase 3/4 study designed to compare the safety and efficacy of investigational first-line combination therapy (Letairis and tadalafil) to first-line monotherapy (Letairis or tadalafil) in patients with WHO/NYHA functional class II and III PAH. In the primary study analysis, 500 patients were randomized (2:1:1) to receive Letairis and tadalafil (n=253) or monotherapy with Letairis (n=126) or tadalafil (n=121) (titrated from 5 mg to 10 mg once-daily and from 20 mg to 40 mg once-daily for Letairis and tadalafil, respectively).
The primary endpoint was time to first clinical failure event, a composite endpoint that incorporates both the traditional components of clinical worsening (death, hospitalization and disease worsening) with a component of unsatisfactory long-term clinical response (all events adjudicated by an independent, blinded committee).
The treatment effect for the composite primary endpoint of time to clinical failure was driven mainly by a reduced number of hospitalizations due to PAH, with a reduced risk of hospitalization due to PAH of 63 percent (hazard ratio = 0.37; 95 percent CI: 0.22, 0.64; p<0.001).
Consistently favorable reductions in clinical failure events were observed based on etiology, WHO functional class, age, geographical area and gender. The predefined subgroup analysis of the primary endpoint suggested that patients with WHO functional class II (n=155; hazard ratio = 0.21; 95 percent CI: 0.07, 0.63); p=0.005) responded even more positively than patients with WHO functional class III (n=345; hazard ratio = 0.58; 95 percent CI: 0.39, 0.86; p=0.006).
Statistically significant improvements were also observed with the following secondary endpoints versus the pooled monotherapy arm: change from baseline at week 24 in N-terminal pro-B-type natriuretic peptide (NT-proBNP) (-67 percent vs. -50 percent; p<0.001), percentage of patients with satisfactory clinical response at week 24 (39 percent vs. 29 percent; odds ratio 1.56; p=0.03) and median change from baseline to week 24 in six-minute walk distance (6MWD) (49 meters vs. 24 meters; p<0.001). There was no difference between treatment groups in the change from baseline to week 24 for WHO functional class.
No new safety signals were detected with the combination of Letairis and tadalafil. Adverse events occurring more frequently in the combination arm than in either monotherapy arm were peripheral edema (Combination: 45 percent; Letairis: 33 percent; tadalafil: 28 percent), headache (Combination: 42 percent; Letairis: 33 percent; tadalafil: 35 percent), nasal congestion (Combination: 21 percent; Letairis: 15 percent; tadalafil: 12 percent) and anemia (Combination: 15 percent; Letairis: 6 percent; tadalafil: 12 percent).
Additional results from the study are available at www.nejm.org.
Gilead submitted the AMBITION data in a Letairis supplemental new drug
application (sNDA) to the
In the U.S., Letairis has a labeled BOXED WARNING and an associated Risk Evaluation and Mitigation Strategy (REMS) program regarding the risk of embryo-fetal toxicity; see below for Important U.S. Safety Information for Letairis.
AMBITION was cosponsored by Gilead and GSK.
About Pulmonary Arterial Hypertension (
PAH is a debilitating disease characterized by constriction of the blood vessels in the lungs leading to high pulmonary arterial pressures. These high pressures make it difficult for the heart to pump blood through the lungs to be oxygenated. Patients with PAH suffer from shortness of breath as the heart struggles to pump against these high pressures, causing such patients to ultimately die of heart failure. PAH can occur with no known underlying cause, or it can occur secondary to diseases such as connective tissue disease, congenital heart defects, cirrhosis of the liver and HIV infection.
Important U.S. Safety Information for Letairis
BOXED WARNING: EMBRYO-FETAL TOXICITY
Do not administer Letairis to a pregnant female because it may cause fetal harm. Letairis is very likely to produce serious birth defects if used by pregnant females, as this effect has been seen consistently when it is administered to animals.
Exclude pregnancy before the initiation of treatment with Letairis. Females of reproductive potential must use acceptable methods of contraception during treatment with Letairis and for one month after treatment. Obtain monthly pregnancy tests during treatment and 1 month after discontinuation of treatment.
Because of the risk of embryo-fetal toxicity birth defects, females can only receive Letairis through a restricted program called the Letairis REMS program.
- Do not administer Letairis to a pregnant woman because it can cause fetal harm.
Letairis is contraindicated in patients with Idiopathic Pulmonary
Fibrosis (IPF) including IPF patients with pulmonary hypertension (
Warnings and precautions
- Embryo-fetal Toxicity: Letairis may cause fetal harm when administered during pregnancy.
Letairis REMS Program: For all females, Letairis is only
available through a restricted program called Letairis REMS. Some
requirements of the Letairis REMS Program include:
- Prescribers must be certified with the program by enrolling and completing training.
All females, regardless of reproductive potential, must enroll in
the Letairis REMS Program prior to initiating Letairis. Male
patients are not enrolled in the REMS.
Pharmacies that dispense Letairis must be certified with the program and must dispense to female patients who are authorized to receive Letairis.
Further information is available at www.letairisrems.com or 1-866-664-5327.
- Mild to moderate peripheral edema: Peripheral edema occurred more frequently in elderly patients (age ≥65 years) receiving Letairis (29 percent; 16/56) compared to placebo (4 percent; 1/28). Peripheral edema is a known class effect of endothelin receptor antagonists. In addition, there have been postmarketing reports of fluid retention occurring within weeks after starting Letairis that required intervention with a diuretic, fluid management, or, in some cases, hospitalization for decompensating heart failure.
- Pulmonary Edema with PVOD: If patients develop acute pulmonary edema during initiation of therapy with vasodilating agents such as Letairis, pulmonary veno-occlusive disease should be considered, and if confirmed, Letairis should be discontinued.
- Decreases in sperm count have been observed in patients taking endothelin receptor antagonists and in animal fertility studies with ambrisentan. Counsel patients about potential effects on fertility.
- Hematologic changes: Decreases in hemoglobin have been observed within the first few weeks of treatment with Letairis, and may persist during treatment. There have been postmarketing reports of anemia requiring transfusion. Measure hemoglobin prior to initiation, at 1 month, and periodically thereafter. Initiation of Letairis therapy is not recommended for patients with clinically significant anemia.
|Most Common Adverse Reactions (>3% compared to placebo)|
|Placebo (N=132)||LETAIRIS (N=261)|
|Adverse reaction||n (%)||n (%)||Placebo-adjusted (%)|
|Peripheral edema||14 (11)||45 (17)||6|
|Nasal congestion||2 (2)||15 (6)||4|
|Sinusitis||0 (0)||8 (3)||3|
|Flushing||1 (1)||10 (4)||3|
- During 12-week controlled clinical trials, the incidence of liver aminotransferase (AST, ALT) elevations >3x ULN was 0 percent for Letairis and 2.3 percent for placebo.
- In postmarketing experience, elevations of aminotransferases have been reported with Letairis use; in most cases alternative causes of liver injury could be identified (heart failure, hepatic congestion, hepatitis, alcohol use, hepatotoxic medications). In practice, cases of hepatic injury should be carefully evaluated for cause.
- Other ERAs have been associated with aminotransferase elevations, hepatotoxicity, and cases of liver failure.
- Discontinue Letairis if aminotransferase elevations are >5x ULN or if elevations are accompanied by bilirubin >2x ULN or by signs or symptoms of liver dysfunction, and other causes are excluded.
- Multiple-dose co-administration of Letairis and cyclosporine resulted in an approximately two-fold increase in Letairis exposure in healthy volunteers. Limit the dose of Letairis to 5 mg once daily when co-administered with cyclosporine.
Dosage and administration
Adult Dosage: Initiate treatment at 5 mg once daily, and consider increasing the dose to 10 mg once daily if 5 mg is tolerated. Tablets may be taken with or without food. Tablets should not be split, crushed, or chewed. Doses higher than 10 mg once daily have not been studied in patients with pulmonary arterial hypertension (PAH).
Pregnancy Testing in Females of Reproductive Potential: Initiate treatment with, Letairis in females of reproductive potential only after a negative pregnancy test. Obtain monthly pregnancy tests during treatment.
Not recommended in patients with moderate or severe hepatic impairment. There is no information on the use of Letairis in patients with mild hepatic impairment; however, exposure to Letairis may be increased in these patients.
This press release includes forward-looking statements, within the
meaning of the Private Securities Litigation Reform Act of 1995, that
are subject to risks, uncertainties and other factors, including the
possibility that the
Letairis and Volibris are registered trademarks of
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Gilead Sciences, Inc.
Patrick O’Brien, 650-522-1936 (Investors)
Nathan Kaiser, 650-522-1853 (Media)