Ambrisentan

Ambrisentan
Black Box Warning
Adult Indications & Dosage
Pediatric Indications & Dosage
Contraindications
Warnings & Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Administration & Monitoring
Overdosage
Pharmacology
Clinical Studies
How Supplied
Images
Patient Counseling Information
Precautions with Alcohol
Brand Names
Look-Alike Names

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Gerald Chi

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Black Box Warning

WARNING: EMBRYO-FETAL TOXICITY See full prescribing information for complete Boxed Warning. * 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, females can only receive Letairis through a restricted program called the Letairis REMS program.

Overview

Ambrisentan is an endothelin receptor antagonist that is FDA approved for the {{{indicationType}}} of pulmonary arterial hypertension. There is a Black Box Warning for this drug as shown here. Common adverse reactions include edema, decreased hemoglobin, and headache.

Adult Indications and Dosage

FDA-Labeled Indications and Dosage (Adult)

Pulmonary Arterial Hypertension

• Letairis is indicated for the treatment of pulmonary arterial hypertension (PAH) (WHO Group 1) to improve exercise ability and delay clinical worsening. Studies establishing effectiveness included predominantly patients with WHO Functional Class II–III symptoms and etiologies of idiopathic or heritable PAH (64%) or PAH associated with connective tissue diseases (32%).

• Dosing Information

• 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 administered 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.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Ambrisentan in adult patients.

Non–Guideline-Supported Use

There is limited information regarding Off-Label Non–Guideline-Supported Use of Ambrisentan in adult patients.

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

• Safety and effectiveness of Letairis in pediatric patients have not been established.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Ambrisentan in pediatric patients.

Non–Guideline-Supported Use

There is limited information regarding Off-Label Non–Guideline-Supported Use of Ambrisentan in pediatric patients.

Contraindications

• Pregnancy

• Letairis may cause fetal harm when administered to a pregnant female. Letairis is contraindicated in females who are pregnant. Letairis was consistently shown to have teratogenic effects when administered to animals. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus.

• Idiopathic Pulmonary Fibrosis

• Letairis is contraindicated in patients with Idiopathic Pulmonary Fibrosis (IPF), including IPF patients with pulmonary hypertension (WHO Group 3)

Warnings

WARNING: EMBRYO-FETAL TOXICITY See full prescribing information for complete Boxed Warning. * 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, females can only receive Letairis through a restricted program called the Letairis REMS program.

Embryo-fetal Toxicity

• Letairis may cause fetal harm when administered during pregnancy and is contraindicated for use in females who are pregnant. In females of reproductive potential, exclude pregnancy prior to initiation of therapy, ensure use of acceptable contraceptive methods, and obtain monthly pregnancy tests.
• Letairis is only available for females through a restricted program under a REMS.

Letairis REMS Program

• For all females, Letairis is available only through a restricted program called the Letairis REMS, because of the risk of embryo-fetal toxicity.
• Notable requirements of the Letairis REMS program include the following:

• 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.

• Females of reproductive potential must comply with the pregnancy testing and contraception requirements.

• 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.

Fluid Retention

• Peripheral edema is a known class effect of endothelin receptor antagonists, and is also a clinical consequence of PAH and worsening PAH. In the placebo-controlled studies, there was an increased incidence of peripheral edema in patients treated with doses of 5 or 10 mg Letairis compared to placebo. Most edema was mild to moderate in severity, and it occurred with greater frequency and severity in elderly patients.
• In addition, there have been postmarketing reports of fluid retention in patients with pulmonary hypertension, occurring within weeks after starting Letairis. Patients required intervention with a diuretic, fluid management, or, in some cases, hospitalization for decompensating heart failure.
• If clinically significant fluid retention develops, with or without associated weight gain, further evaluation should be undertaken to determine the cause, such as Letairis or underlying heart failure, and the possible need for specific treatment or discontinuation of Letairis therapy.

Pulmonary Edema with Pulmonary Veno-occlusive Disease (PVOD)

• If patients develop acute pulmonary edema during initiation of therapy with vasodilating agents such as Letairis, the possibility of PVOD should be considered, and if confirmed Letairis should be discontinued.

Decreased Sperm Counts

• Decreased sperm counts have been observed in human and animal studies with another endothelin receptor antagonist and in animal fertility studies with ambrisentan. Letairis may have an adverse effect on spermatogenesis. Counsel patients about potential effects on fertility.

Hematological Changes

• Decreases in hemoglobin concentration and hematocrit have followed administration of other endothelin receptor antagonists and were observed in clinical studies with Letairis. These decreases were observed within the first few weeks of treatment with Letairis, and stabilized thereafter. The mean decrease in hemoglobin from baseline to end of treatment for those patients receiving Letairis in the 12-week placebo-controlled studies was 0.8 g/dL.
• Marked decreases in hemoglobin (>15% decrease from baseline resulting in a value below the lower limit of normal) were observed in 7% of all patients receiving Letairis (and 10% of patients receiving 10 mg) compared to 4% of patients receiving placebo. The cause of the decrease in hemoglobin is unknown, but it does not appear to result from hemorrhage or hemolysis.
• In the long-term open-label extension of the two pivotal clinical studies, mean decreases from baseline (ranging from 0.9 to 1.2 g/dL) in hemoglobin concentrations persisted for up to 4 years of treatment.
• There have been postmarketing reports of decreases in hemoglobin concentration and hematocrit that have resulted in anemia requiring transfusion.
• Measure hemoglobin prior to initiation of Letairis, at one month, and periodically thereafter. Initiation of Letairis therapy is not recommended for patients with clinically significant anemia. If a clinically significant decrease in hemoglobin is observed and other causes have been excluded, consider discontinuing Letairis.

Adverse Reactions

Clinical Trials Experience

• Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
• Safety data for Letairis were obtained from two 12-week, placebo-controlled studies in patients with pulmonary arterial hypertension (PAH) (ARIES-1 and ARIES-2) and four nonplacebo-controlled studies in 483 patients with PAH who were treated with doses of 1, 2.5, 5, or 10 mg once daily. The exposure to Letairis in these studies ranged from 1 day to 4 years (N = 418 for at least 6 months and N = 343 for at least 1 year).
• In ARIES-1 and ARIES-2, a total of 261 patients received Letairis at doses of 2.5, 5, or 10 mg once daily and 132 patients received placebo. The adverse reactions that occurred in >3% more patients receiving Letairis than receiving placebo are shown in Table 1.

This image is provided by the National Library of Medicine.

• Most adverse drug reactions were mild to moderate and only nasal congestion was dose-dependent.
• Few notable differences in the incidence of adverse reactions were observed for patients by age or sex. Peripheral edema was similar in younger patients (<65 years) receiving Letairis (14%; 29/205) or placebo (13%; 13/104), and was greater in elderly patients (≥65 years) receiving Letairis (29%; 16/56) compared to placebo (4%; 1/28). The results of such subgroup analyses must be interpreted cautiously.
• The incidence of treatment discontinuations due to adverse events other than those related to PAH during the clinical trials in patients with PAH was similar for Letairis (2%; 5/261 patients) and placebo (2%; 3/132 patients). The incidence of patients with serious adverse events other than those related to PAH during the clinical trials in patients with PAH was similar for placebo (7%; 9/132 patients) and for Letairis (5%; 13/261 patients).
• During 12-week controlled clinical trials, the incidence of aminotransferase elevations >3 × upper limit of normal (ULN) were 0% on Letairis and 2.3% on placebo. In practice, cases of hepatic injury should be carefully evaluated for cause.

Use in Patients with Prior Endothelin Receptor Antagonist (ERA) Related Serum Liver Enzyme Abnormalities

• In an uncontrolled, open-label study, 36 patients who had previously discontinued endothelin receptor antagonists (ERAs: bosentan, an investigational drug, or both) due to aminotransferase elevations >3 × ULN were treated with Letairis. Prior elevations were predominantly moderate, with 64% of the ALT elevations <5 × ULN, but 9 patients had elevations >8 × ULN. Eight patients had been re-challenged with bosentan and/or the investigational ERA and all eight had a recurrence of aminotransferase abnormalities that required discontinuation of ERA therapy. All patients had to have normal aminotransferase levels on entry to this study. Twenty-five of the 36 patients were also receiving prostanoid and/or phosphodiesterase type 5 (PDE5) inhibitor therapy. Two patients discontinued early (including one of the patients with a prior 8 × ULN elevation). Of the remaining 34 patients, one patient experienced a mild aminotransferase elevation at 12 weeks on Letairis 5 mg that resolved with decreasing the dosage to 2.5 mg, and that did not recur with later escalations to 10 mg. With a median follow-up of 13 months and with 50% of patients increasing the dose of Letairis to 10 mg, no patients were discontinued for aminotransferase elevations. While the uncontrolled study design does not provide information about what would have occurred with re-administration of previously used ERAs or show that Letairis led to fewer aminotransferase elevations than would have been seen with those drugs, the study indicates that Letairis may be tried in patients who have experienced asymptomatic aminotransferase elevations on other ERAs after aminotransferase levels have returned to normal.

Postmarketing Experience

• The following adverse reactions were identified during postapproval use of Letairis. Because these reactions were reported voluntarily from a population of uncertain size, it is not possible to estimate reliably the frequency or to establish a causal relationship to drug exposure: anemia, heart failure (associated with fluid retention), hypersensitivity (eg, angioedema, rash), nausea, and vomiting.
• Elevations of liver aminotransferases (ALT, AST) have been reported with Letairis use; in most cases alternative causes of the liver injury could be identified (heart failure, hepatic congestion, hepatitis, alcohol use, hepatotoxic medications). Other endothelin receptor antagonists have been associated with elevations of aminotransferases, hepatotoxicity, and cases of liver failure.

Drug Interactions

• Multiple dose coadministration of ambrisentan and cyclosporine resulted in an approximately 2-fold increase in ambrisentan exposure in healthy volunteers; therefore, limit the dose of ambrisentan to 5 mg once daily when coadministered with cyclosporine.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA):

• Pregnancy Category X

• Risk Summary

• Letairis may cause fetal harm when administered to a pregnant woman and is contraindicated during pregnancy. Letairis was teratogenic in rats and rabbits at doses which resulted in exposures of 3.5 and 1.7 times, respectively, the human dose of 10 mg per day. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, advise the patient of the potential hazard to a fetus.

• Animal Data

• Letairis was teratogenic at oral doses of ≥ 15 mg/kg/day (AUC 51.7 h•µg/mL) in rats and ≥ 7 mg/kg/day (24.7 h•µg/mL) in rabbits; it was not studied at lower doses. These doses are of 3.5 and 1.7 times, respectively, the human dose of 10 mg per day (14.8 h•µg/mL) based on AUC. In both species, there were abnormalities of the lower jaw and hard and soft palate, malformation of the heart and great vessels, and failure of formation of the thymus and thyroid.
• A preclinical study in rats has shown decreased survival of newborn pups (mid and high doses) and effects on testicle size and fertility of pups (high dose) following maternal treatment with ambrisentan from late gestation through weaning. Doses tested were 17 ×, 51 ×, and 170 × (on a mg/kg:mg/m2 basis) the maximum oral human dose of 10 mg and an average adult body weight of 70 kg.

Pregnancy Category (AUS):

• Australian Drug Evaluation Committee (ADEC) Pregnancy Category

There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Ambrisentan in women who are pregnant.

Labor and Delivery

There is no FDA guidance on use of Ambrisentan during labor and delivery.

Nursing Mothers

• It is not known whether ambrisentan is present in human milk. Because many drugs are present in human milk and because of the potential for serious adverse reactions in nursing infants from Letairis, a decision should be made whether to discontinue nursing or discontinue Letairis, taking into account the importance of the drug to the mother.

Pediatric Use

• Safety and effectiveness of Letairis in pediatric patients have not been established.

Geriatic Use

• In the two placebo-controlled clinical studies of Letairis, 21% of patients were ≥65 years old and 5% were ≥75 years old. The elderly (age ≥65 years) showed less improvement in walk distances with Letairis than younger patients did, but the results of such subgroup analyses must be interpreted cautiously. Peripheral edema was more common in the elderly than in younger patients.

Gender

There is no FDA guidance on the use of Ambrisentan with respect to specific gender populations.

Race

There is no FDA guidance on the use of Ambrisentan with respect to specific racial populations.

Renal Impairment

• The impact of renal impairment on the pharmacokinetics of ambrisentan has been examined using a population pharmacokinetic approach in PAH patients with creatinine clearances ranging between 20 and 150 mL/min. There was no significant impact of mild or moderate renal impairment on exposure to ambrisentan [see Clinical Pharmacology (12.3)]. Dose adjustment of Letairis in patients with mild or moderate renal impairment is therefore not required. There is no information on the exposure to ambrisentan in patients with severe renal impairment.
• The impact of hemodialysis on the disposition of ambrisentan has not been investigated.

Hepatic Impairment

• Pre-existing Hepatic Impairment

• The influence of pre-existing hepatic impairment on the pharmacokinetics of ambrisentan has not been evaluated. Because there is in vitro and in vivo evidence of significant metabolic and biliary contribution to the elimination of ambrisentan, hepatic impairment might be expected to have significant effects on the pharmacokinetics of ambrisentan. Letairis is not recommended in patients with moderate or severe hepatic impairment. There is no information on the use of Letairis in patients with mild pre-existing impaired liver function; however, exposure to ambrisentan may be increased in these patients.

• Elevation of Liver Transaminases

• Other endothelin receptor antagonists (ERAs) have been associated with aminotransferase (AST, ALT) elevations, hepatotoxicity, and cases of liver failure. In patients who develop hepatic impairment after Letairis initiation, the cause of liver injury should be fully investigated. Discontinue Letairis if elevations of liver aminotransferases are >5 × ULN or if elevations are accompanied by bilirubin >2 × ULN, or by signs or symptoms of liver dysfunction and other causes are excluded.

Females of Reproductive Potential and Males

• Pregnancy Testing

• Female patients of reproductive potential must have a negative pregnancy test prior to initiation of treatment, monthly pregnancy test during treatment, and 1 month after stopping treatment with Letairis. Advise patients to contact their healthcare provider if they become pregnant or suspect they may be pregnant. Perform a pregnancy test if pregnancy is suspected for any reason. For positive pregnancy tests, counsel patient on the potential risk to the fetus and patient options.

• Contraception

• Female patients of reproductive potential must use acceptable methods of contraception during treatment with Letairis and for 1 month after stopping treatment with Letairis. Patients may choose one highly effective form of contraception (intrauterine device (IUD), contraceptive implant, or tubal sterilization) or a combination of methods (hormone method with a barrier method or two barrier methods). If a partner's vasectomy is the chosen method of contraception, a hormone or barrier method must be used along with this method. Counsel patients on pregnancy planning and prevention, including emergency contraception, or designate counseling by another healthcare provider trained in contraceptive counseling.

• Infertility in Males

• In a 6-month study of another endothelin receptor antagonist, bosentan, 25 male patients with WHO functional class III and IV PAH and normal baseline sperm count were evaluated for effects on testicular function. There was a decline in sperm count of at least 50% in 25% of the patients after 3 or 6 months of treatment with bosentan. One patient developed marked oligospermia at 3 months, and the sperm count remained low with 2 follow-up measurements over the subsequent 6 weeks. Bosentan was discontinued and after 2 months the sperm count had returned to baseline levels. In 22 patients who completed 6 months of treatment, sperm count remained within the normal range and no changes in sperm morphology, sperm motility, or hormone levels were observed. Based on these findings and preclinical data from endothelin receptor antagonists, it cannot be excluded that endothelin receptor antagonists such as Letairis have an adverse effect on spermatogenesis. Counsel patients about the potential effects on fertility.

Immunocompromised Patients

There is no FDA guidance one the use of Ambrisentan in patients who are immunocompromised.

Administration and Monitoring

Administration

• Oral

Monitoring

There is limited information regarding Monitoring of Ambrisentan in the drug label.

• xx

IV Compatibility

There is limited information regarding IV Compatibility of Ambrisentan in the drug label.

Overdosage

Acute Overdose

Signs and Symptoms

• Description

Management

• xx

Chronic Overdose

There is limited information regarding Chronic Overdose of Ambrisentan in the drug label.

Pharmacology

Ambrisentan
Systematic (IUPAC) name
(2S)-2-[(4,6-dimethylpyrimidin-2-yl)oxy]-3-methoxy- 3,3-diphenylpropanoic acid
Identifiers
CAS number	177036-94-1
ATC code	C02KX02
PubChem	6918493
Chemical data
Formula	Template:OrganicBox atomTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox
Mol. mass	378.421 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	Undetermined
Protein binding	99%
Metabolism	?
Half life	15 hours (terminal)
Excretion	?
Therapeutic considerations
Licence data	EU, US
Pregnancy cat.	X(AU) X(US)
Legal status	Prescription Only (S4)(AU) ?(CA) POM(UK) [[Prescription drug|Template:Unicode-only]](US)
Routes	Oral

Mechanism of Action

Structure

This image is provided by the National Library of Medicine.

Pharmacodynamics

There is limited information regarding Pharmacodynamics of Ambrisentan in the drug label.

Pharmacokinetics

There is limited information regarding Pharmacokinetics of Ambrisentan in the drug label.

Nonclinical Toxicology

There is limited information regarding Nonclinical Toxicology of Ambrisentan in the drug label.

Clinical Studies

There is limited information regarding Clinical Studies of Ambrisentan in the drug label.

How Supplied

Storage

There is limited information regarding Ambrisentan Storage in the drug label.

Images

Drug Images

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Package and Label Display Panel

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Patient Counseling Information

There is limited information regarding Patient Counseling Information of Ambrisentan in the drug label.

Precautions with Alcohol

• Alcohol-Ambrisentan interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

Brand Names

• Letairis®

Look-Alike Drug Names

• Letairis® — Letaris®

Drug Shortage Status

Price

References

The contents of this FDA label are provided by the National Library of Medicine.

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