Ambrisentan

Box Warning 4/2025 Indications and Usage (1) 4/2025 Dosage and Administration, Pregnancy Testing in Females of Reproductive Potential (2.2) 4/2025 Warnings and Precautions for Use Embryo-fetal Toxicity (5.1) 4/2025 Ambrisentan Risk Evaluation and Mitigation Strategy (REMS) (5.2) (removed) 4/2025 Box Warning 4/2025 Indications and Usage ( 1 ) 4/2025 Dosage and Administration, Pregnancy Testing in Females of Reproductive Potential ( 2.2 ) 4/2025 Warnings and Precautions for Use Embryo-fetal Toxicity ( 5.1 ) 4/2025 Ambrisentan Risk Evaluation and Mitigation Strategy (REMS) ( 5.2 ) (removed) 4/2025

1 INDICATIONS AND USAGE Ambrisentan tablets are indicated for the treatment of pulmonary arterial hypertension (PAH) (WHO Group 1) in adult patients: To improve exercise ability and delay clinical worsening. In combination with tadalafil to reduce the risks of disease progression and hospitalization for worsening PAH, and to improve exercise ability [see Clinical Studies ( 14.2 )] . Studies establishing effectiveness included predominantly patients with WHO Functional Class II–III symptoms and etiologies of idiopathic or heritable PAH (60%) or PAH associated with connective tissue diseases (34%). Ambrisentan is an endothelin receptor antagonist indicated for the treatment of pulmonary arterial hypertension (PAH) (WHO Group 1) in adult patients: To improve exercise ability and delay clinical worsening. In combination with tadalafil to reduce the risks of disease progression and hospitalization for worsening PAH, and to improve exercise ability. Studies establishing effectiveness included trials predominantly in patients with WHO Functional Class II–III symptoms and etiologies of idiopathic or heritable PAH (60%) or PAH associated with connective tissue diseases (34%) ( 1 ).

2 DOSAGE AND ADMINISTRATION Initiate treatment at 5 mg once daily ( 2.1 ). May be started with tadalafil ( 2.1 ). Titrate at 4-week intervals as needed and tolerated ( 2.1 ). Do not split, crush, or chew tablets ( 2.1 ). 2.1. Adult Dosage Initiate treatment at 5 mg once daily, with or without tadalafil 20 mg once daily. At 4-week intervals, either the dose of ambrisentan or tadalafil can be increased, as needed and tolerated, to ambrisentan tablets, 10 mg or tadalafil 40 mg. Do not split, crush, or chew tablets. 2.2. Pregnancy Testing in Females of Reproductive Potential Initiate treatment with ambrisentan in females of reproductive potential only after a negative pregnancy test. Obtain monthly pregnancy tests during treatment [see Use in Specific Populations (8.3) ] .

3 DOSAGE FORMS AND STRENGTHS Ambrisentan Tablets are available containing 5 mg or 10 mg of ambrisentan. • The 5 mg tablets are pink, film-coated, round, unscored tablets debossed with M on one side of the tablet and AN on the other side. • The 10 mg tablets are pink, film-coated, capsule shaped, unscored tablets debossed with M on one side of the tablet and AN1 on the other side. Tablet: 5 mg and 10 mg ( 3 )

4 CONTRAINDICATIONS Pregnancy ( 4.1 ) Idiopathic Pulmonary Fibrosis ( 4.2 ) 4.1 Pregnancy Ambrisentan tablets may cause fetal harm when administered to a pregnant female. Ambrisentan tablets are contraindicated in females who are pregnant. Ambrisentan tablets were 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 [see Dosage and Administration ( 2.2 ), Warnings and Precautions ( 5.1 ), and Use in Specific Populations ( 8.1 )] . 4.2 Idiopathic Pulmonary Fibrosis Ambrisentan tablets are contraindicated in patients with Idiopathic Pulmonary Fibrosis (IPF), including IPF patients with pulmonary hypertension (WHO Group 3) [see Clinical Studies ( 14.4 )] .

6 ADVERSE REACTIONS Clinically significant adverse reactions that appear in other sections of the labeling include: Embryo-fetal Toxicity [see Warnings and Precautions (5.1) , Use in Specific Populations (8.1) ] Fluid Retention [see Warnings and Precautions (5.3) ] Pulmonary Edema with PVOD [see Warnings and Precautions (5.4) ] Decreased Sperm Count [see Warnings and Precautions (5.5) ] Hematologic Changes [see Warnings and Precautions (5.6) ] Most common adverse reactions (>3% compared to placebo) are peripheral edema, nasal congestion, sinusitis, and flushing ( 6.1 ). When used in combination with tadalafil, most common adverse reactions (>5% compared with either Monotherapy) are peripheral edema, headache, nasal congestion, cough, anemia, dyspepsia, and bronchitis ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Sigmapharm Laboratories, LLC, Pharmacovigilance at 1-855-332-0731 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1. 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 ambrisentan are presented from two 12-week, placebo-controlled studies (ARIES-1 and ARIES-2) in patients with pulmonary arterial hypertension (PAH), and one randomized, double-blind, active-controlled trial in 605 patients with PAH (AMBITION) comparing ambrisentan plus tadalafil to ambrisentan or tadalafil alone. The exposure to ambrisentan in these studies ranged from 1 day to 4 years (N=357 for at least 6 months and N=279 for at least 1 year). In ARIES-1 and ARIES-2, a total of 261 patients received ambrisentan 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 ambrisentan than receiving placebo are shown in Table 1. Table 1 Adverse Reactions with Placebo-Adjusted Rates >3% in ARIES-1 and ARIES-2 Placebo (N = 132) Ambrisentan (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 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 (3 x upper limit of normal (ULN) were 0% on ambrisentan and 2.3% on placebo. In practice, cases of hepatic injury should be carefully evaluated for cause. Combination Use with Tadalafil The mean exposure to ambrisentan + tadalafil in the AMBITION study was 78.7 weeks. The adverse reactions that occurred in >5% more patients receiving ambrisentan + tadalafil than receiving ambrisentan or tadalafil monotherapy in AMBITION are shown in Table 2. Table 2 Adverse Reactions Reported More Commonly (>5%) on Ambrisentan + Tadalafil than on Ambrisentan or Tadalafil Monotherapy (ITT) in AMBITION Adverse Reactions Ambrisentan + Tadalafil Combination Therapy (N=302) n (%) Ambrisentan Monotherapy (N=152) n (%) Tadalafil Monotherapy (N=151) n (%) Peripheral edema 135 (45%) 58 (38%) 43 (28%) Headache 125 (41%) 51 (34%) 53 (35%) Nasal congestion 58 (19%) 25 (16%) 17 (11%) Cough 53 (18%) 20 (13%) 24 (16%) Anemia 44 (15%) 11 (7%) 17 (11%) Dyspepsia 32 (11%) 5 (3%) 18 (12%) Bronchitis 31 (10%) 6 (4%) 13 (9%) Peripheral edema was more frequent on combination therapy; however, there was no notable difference observed in the incidence of peripheral edema in elderly patients (≥65 years) versus younger patients (3 x ULN were treated with ambrisentan. Prior elevations were predominantly moderate, with 64% of the ALT elevations 8 x ULN. Eight patients had been re-challenged with bosentan and/or the investigational ERA and all eight had a recurrence of aminotransferase abnormalities that …

7 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 [see Clinical Pharmacology (12.3) ]. Cyclosporine increases ambrisentan exposure; limit ambrisentan dose to 5 mg once daily ( 7 ).

Drug Interactions In Vitro Studies Studies with human liver tissue indicate that ambrisentan is metabolized by CYP3A, CYP2C19, and uridine 5’-diphosphate glucuronosyltransferases (UGTs) 1A9S, 2B7S, and 1A3S. In vitro studies suggest that ambrisentan is a substrate of the Organic Anion Transporting Polypeptides OATP1B1 and OATP1B3, and P-glycoprotein (P-gp). Drug interactions might be expected because of these factors; however, a clinically relevant interaction has been demonstrated only with cyclosporine [see Drug Interactions (7) ] . In vitro studies found ambrisentan to have little to no inhibition of human hepatic transporters. Ambrisentan demonstrated weak dose-dependent inhibition of OATP1B1, OATP1B3, and NTCP (IC 50 of 47 μM, 45 μM, and approximately 100 μM, respectively) and no transporter-specific inhibition of BSEP, BRCP, P-gp, or MRP2. Ambrisentan does not inhibit or induce drug metabolizing enzymes at clinically relevant concentrations. In Vivo Studies The effects of other drugs on ambrisentan pharmacokinetics and the effects of ambrisentan on the exposure to other drugs are shown in Figure 2 and Figure 3, respectively. Figure 2 Effects of Other Drugs on Ambrisentan Pharmacokinetics Figure 3 Effects of Ambrisentan on Other Drugs Figure 2 Effects of Other Drugs on Ambrisentan Pharmacokinetics Figure 3 Effects of Ambrisentan on Other Drugs

8 USE IN SPECIFIC POPULATIONS • Breastfeeding: Choose ambrisentan tablets or breastfeeding ( 8.2 ). • Not recommended in patients with moderate or severe hepatic impairment ( 8.7 ). 8.1 Pregnancy Risk Summary Based on data from animal reproduction studies, ambrisentan tablets may cause fetal harm, including birth defects and fetal death, when administered to a pregnant woman and is contraindicated during pregnancy. There are limited data on ambrisentan tablets use in pregnant women. Available data from postmarketing reports and published literature over decades of use with endothelin receptor antagonists in the same class as ambrisentan tablets have not identified an increased risk of major birth defects; however, these data are limited. Methodological limitations of these postmarketing reports and published literature include lack of a control group; limited information regarding dose, duration, and timing of drug exposure; and missing data. These limitations preclude establishing a reliable estimate of the risk of adverse fetal and neonatal outcomes with maternal endothelin receptor antagonist use. In animal reproduction studies, ambrisentan tablets were 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 [see Animal Data ] . 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 [see Contraindications (4.1) , Warnings and Precautions (5.1) ]. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. Data Animal Data Ambrisentan tablets were teratogenic at oral dosages 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 dosages. These dosages 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 dosages) and effects on testicle size and fertility of pups (high dosage) following maternal treatment with ambrisentan from late gestation through weaning. The mid and high dosages were 51 x, and 170 x (on a mg/m 2 body surface area basis) the maximum oral human dose of 10 mg and an average adult body weight of 70 kg. These effects were absent at a maternal dosage 17 x the human dose based on mg/m 2 . 8.2 Lactation Risk Summary 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 breastfed infants from ambrisentan tablets, a decision should be made whether to discontinue breastfeeding or discontinue ambrisentan tablets, taking into account the importance of the drug to the mother. 8.3 Females and Males of Reproductive Potential Based on data from animal reproductive toxicity studies, ambrisentan may cause fetal harm, including birth defects and fetal death, when administered to a pregnant patient and is contraindicated during pregnancy [see Contraindications (4.1) , Use in Specific Populations (8.1) ] . Pregnancy Testing Verify that patients who can become pregnant are not pregnant prior to initiating ambrisentan. The patient should contact their physician immediately for pregnancy testing if onset of menses is delayed or pregnancy is suspected. If the pregnancy test is positive, the physician and patient should discuss the risks to the pregnancy and the fetu …

12.1 Mechanism of Action Endothelin-1 (ET-1) is a potent autocrine and paracrine peptide. Two receptor subtypes, ET A and ET B , mediate the effects of ET-1 in the vascular smooth muscle and endothelium. The primary actions of ET A are vasoconstriction and cell proliferation, while the predominant actions of ET B are vasodilation, antiproliferation, and ET-1 clearance. In patients with PAH, plasma ET-1 concentrations are increased as much as 10-fold and correlate with increased mean right atrial pressure and disease severity. ET-1 and ET-1 mRNA concentrations are increased as much as 9-fold in the lung tissue of patients with PAH, primarily in the endothelium of pulmonary arteries. These findings suggest that ET-1 may play a critical role in the pathogenesis and progression of PAH. Ambrisentan is a high-affinity (K i = 0.011 nM) ET A receptor antagonist with a high selectivity for the ET A versus ET B receptor (> 4000-fold). The clinical impact of high selectivity for ET A is not known.

11 DESCRIPTION Ambrisentan is an endothelin receptor antagonist that is selective for the endothelin type-A (ET A ) receptor. The chemical name of ambrisentan is (+)-(2 S )-2-[(4,6-dimethylpyrimidin-2-yl)oxy]-3-methoxy-3,3-diphenylpropanoic acid. It has a molecular formula of C 22 H 22 N 2 O 4 and a molecular weight of 378.42. It contains a single chiral center determined to be the ( S ) configuration and has the following structural formula: Figure 1 Ambrisentan Structural Formula Ambrisentan is a white to off-white, crystalline solid. It is a carboxylic acid with a pKa of 4.0. Ambrisentan is practically insoluble in water and in aqueous solutions at low pH. Solubility increases in aqueous solutions at higher pH. In the solid state ambrisentan is very stable, is not hygroscopic, and is not light sensitive. Ambrisentan tablets are available as 5 mg and 10 mg film-coated tablets for once daily oral administration. The tablets include the following inactive ingredients: croscarmellose sodium, lactose monohydrate, magnesium stearate and microcrystalline cellulose. The tablets are film-coated with a coating material containing FD&C Red #40 aluminum lake, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide. Ambrisentan tablets, 5 mg tablets also contain FD&C Blue #2. Each square shaped, light pink ambrisentan tablet contains 5 mg of ambrisentan. Each oval shaped, dark pink ambrisentan tablet contains 10 mg of ambrisentan. Ambrisentan tablets are unscored. figure1

10 OVERDOSAGE There is no experience with overdosage of ambrisentan tablets. The highest single dose of ambrisentan tablets administered to healthy volunteers was 100 mg, and the highest daily dose administered to patients with PAH was 10 mg once daily. In healthy volunteers, single doses of 50 mg and 100 mg (5 to 10 times the maximum recommended dose) were associated with headache, flushing, dizziness, nausea, and nasal congestion. Massive overdosage could potentially result in hypotension that may require intervention.

16 HOW SUPPLIED/STORAGE AND HANDLING Ambrisentan Tablets, 5 mg are pink-colored, round shaped, film-coated tablets debossed with "1179" on one side and plain on the other side and are supplied as follows: NDC 70710-1179-3 in bottle of 30 tablets with child-resistant closure NDC 70710-1179-9 in bottle of 90 tablets with child-resistant closure NDC 70710-1179-1 in bottle of 100 tablets with child-resistant closure NDC 70710-1179-7 in unit-dose blister cartons of 10 tablets (1 x 10 unit-dose) NDC 70710-1179-8 in unit-dose blister cartons of 30 tablets (3 x 10 unit-dose) Ambrisentan Tablets, 10 mg are white to off-white, oval shaped, film-coated tablets debossed with "1180" on one side and plain on the other side and are supplied as follows: NDC 70710-1180-3 in bottle of 30 tablets with child-resistant closure NDC 70710-1180-9 in bottle of 90 tablets with child-resistant closure NDC 70710-1180-1 in bottle of 100 tablets with child-resistant closure NDC 70710-1180-7 in unit-dose blister cartons of 10 tablets (1 x 10 unit-dose) NDC 70710-1180-8 in unit-dose blister cartons of 30 tablets (3 x 10 unit-dose) Store at 20° C to 25° C (68° F to 77° F); excursions permitted to 15 ° C to 30° C (59 ° F to 86° F) [see USP Controlled Room Temperature]. Store ambrisentan tablets in its original packaging.