1. Name Of The Medicinal Product
Tracleer
2. Qualitative And Quantitative Composition
Each film-coated tablet contains 125 mg bosentan (as monohydrate).
For a full list of excipients, see section 6.1.
3. Pharmaceutical Form
Film-coated tablet (tablets):
Orange-white, oval, biconvex, film-coated tablets, embossed with “125” on one side.
4. Clinical Particulars
4.1 Therapeutic Indications
Treatment of pulmonary arterial hypertension (PAH) to improve exercise capacity and symptoms in patients with WHO functional class III. Efficacy has been shown in:
• Primary (idiopathic and heritable) PAH
• PAH secondary to scleroderma without significant interstitial pulmonary disease
• PAH associated with congenital systemic-to-pulmonary shunts and Eisenmenger's physiology
Some improvements have also been shown in patients with PAH WHO functional class II (see section 5.1).
Tracleer is also indicated to reduce the number of new digital ulcers in patients with systemic sclerosis and ongoing digital ulcer disease (see section 5.1).
4.2 Posology And Method Of Administration
Tablets are to be taken orally morning and evening, with or without food. The film-coated tablets are to be swallowed with water.
Pulmonary arterial hypertension
Treatment should only be initiated and monitored by a physician experienced in the treatment of pulmonary arterial hypertension.
In adult patients, Tracleer treatment should be initiated at a dose of 62.5 mg twice daily for 4 weeks and then increased to the maintenance dose of 125 mg twice daily.
For paediatric patients aged 2 years or older, the optimal maintenance dose has not been defined in well-controlled studies. However, paediatric pharmacokinetic data have shown that bosentan plasma concentrations in children were on average lower than in adult patients and were not increased by increasing the dose of Tracleer above 2 mg/kg body weight twice daily (see section 5.2). Based on these pharmacokinetic results, higher doses are unlikely to be more effective, and greater adverse event rates cannot formally be excluded in young children if the dose is increased. No clinical study has been conducted to compare the efficacy/safety ratio of 2 mg/kg to 4 mg/kg body weight twice daily in children.
There is only limited clinical experience in paediatric patients under 2 years of age.
In the case of clinical deterioration (e.g., decrease in 6-minute walk test distance by at least 10% compared with pre-treatment measurement) despite Tracleer treatment for at least 8 weeks (target dose for at least 4 weeks), alternative therapies should be considered. However, some patients who show no response after 8 weeks of treatment with Tracleer may respond favourably after an additional 4 to 8 weeks of treatment.
In the case of late clinical deterioration despite treatment with Tracleer (i.e., after several months of treatment), the treatment should be re-assessed. Some patients not responding well to 125 mg twice daily of Tracleer may slightly improve their exercise capacity when the dose is increased to 250 mg twice daily. A careful benefit/risk assessment should be made, taking into consideration that the liver toxicity is dose dependent (see sections 4.4 and 5.1).
Discontinuation of treatment
There is limited experience with abrupt discontinuation of Tracleer. No evidence for acute rebound has been observed. However, to avoid the possible occurrence of harmful clinical deterioration due to potential rebound effect, gradual dose reduction (halving the dose for 3 to 7 days) should be considered. Intensified monitoring is recommended during the discontinuation period.
If the decision to withdraw Tracleer is taken, it should be done gradually while an alternative therapy is introduced.
Systemic sclerosis with ongoing digital ulcer disease
Treatment should only be initiated and monitored by a physician experienced in the treatment of systemic sclerosis.
Tracleer treatment should be initiated at a dose of 62.5 mg twice daily for 4 weeks and then increased to the maintenance dose of 125 mg twice daily.
Controlled clinical study experience in this indication is limited to 6 months (see section 5.1).
The patient's response to treatment and need for continued therapy should be re-evaluated on a regular basis. A careful benefit/risk assessment should be made, taking into consideration the liver toxicity of bosentan (see sections 4.4 and 4.8).
There are no data on the safety and efficacy in patients under the age of 18 years. Pharmacokinetic data are not available for Tracleer in young children with this disease.
Special populations
Dosage in hepatic impairment
No dose adjustment is needed in patients with mild hepatic impairment (i.e., Child-Pugh class A) (see section 5.2). Tracleer is contraindicated in patients with moderate to severe liver dysfunction (see sections 4.3, 4.4 and 5.2).
Dosage in renal impairment
No dose adjustment is required in patients with renal impairment. No dose adjustment is required in patients undergoing dialysis (see section 5.2).
Dosage in elderly patients
No dose adjustment is required in patients over the age of 65 years.
4.3 Contraindications
• Hypersensitivity to the active substance or to any of the excipients
• Moderate to severe hepatic impairment , i.e., Child-Pugh class B or C (see section 5.2)
• Baseline values of liver aminotransferases, i.e., aspartate aminotransferases (AST) and/or alanine aminotransferases (ALT), greater than 3 times the upper limit of normal (see section 4.4)
• Concomitant use of cyclosporine A (see section 4.5)
• Pregnancy (see sections 4.4 and 4.6)
• Women of child-bearing potential who are not using reliable methods of contraception (see sections 4.4, 4.5 and 4.6)
4.4 Special Warnings And Precautions For Use
The efficacy of Tracleer has not been established in patients with severe pulmonary arterial hypertension. Transfer to a therapy that is recommended at the severe stage of the disease (e.g., epoprostenol) should be considered if the clinical condition deteriorates (see section 4.2).
The benefit/risk balance of bosentan has not been established in patients with WHO class I functional status of pulmonary arterial hypertension.
Tracleer should only be initiated if the systemic systolic blood pressure is higher than 85 mmHg.
Tracleer has not been shown to have a beneficial effect on the healing of existing digital ulcers.
Liver function
Elevations in liver aminotransferases, i.e., aspartate and alanine aminotransferases (AST and/or ALT), associated with bosentan are dose dependent. Liver enzyme changes typically occur within the first 26 weeks of treatment but may also occur late in treatment (see section 4.8). These increases may be partly due to competitive inhibition of the elimination of bile salts from hepatocytes but other mechanisms, which have not been clearly established, are probably also involved in the occurrence of liver dysfunction. The accumulation of bosentan in hepatocytes leading to cytolysis with potentially severe damage of the liver, or an immunological mechanism, are not excluded. Liver dysfunction risk may also be increased when medicinal products that are inhibitors of the bile salt export pump, e.g., rifampicin, glibenclamide and cyclosporine A (see sections 4.3 and 4.5), are co-administered with bosentan, but limited data are available.
Liver aminotransferase levels must be measured prior to initiation of treatment and subsequently at monthly intervals for the duration of treatment with Tracleer. In addition, liver aminotransferase levels must be measured 2 weeks after any dose increase.
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ULN = Upper Limit of Normal
Haemoglobin concentration
Treatment with bosentan has been associated with dose-related decreases in haemoglobin concentration (see section 4.8). In placebo-controlled studies, bosentan-related decreases in haemoglobin concentration were not progressive, and stabilised after the first 4–12 weeks of treatment. It is recommended that haemoglobin concentrations be checked prior to initiation of treatment, every month during the first 4 months, and quarterly thereafter. If a clinically relevant decrease in haemoglobin concentration occurs, further evaluation and investigation should be undertaken to determine the cause and need for specific treatment. In the post-marketing period, cases of anaemia requiring red blood cell transfusion have been reported (see section 4.8).
Women of child-bearing potential
Tracleer treatment must not be initiated in women of child-bearing potential unless they practise reliable contraception (see section 4.5) and the result of the pre-treatment pregnancy test is negative (see section 4.6).
Before the initiation of Tracleer treatment in women of child-bearing potential, the absence of pregnancy should be checked, appropriate advice on reliable methods of contraception provided, and reliable contraception initiated. Patients and prescribers must be aware that, due to potential pharmacokinetic interactions, Tracleer may render hormonal contraceptives ineffective (see section 4.5). Therefore, women of child-bearing potential must not use hormonal contraceptives (including oral, injectable, transdermal and implantable forms) as the sole method of contraception but should use an additional or an alternative reliable method of contraception. If there is any doubt about what contraceptive advice should be given to the individual patient, consultation with a gynaecologist is recommended.
Because of possible hormonal contraception failure during Tracleer treatment and also bearing in mind the risk that pulmonary hypertension severely deteriorates with pregnancy, monthly pregnancy tests during treatment with Tracleer are recommended to allow early detection of pregnancy.
Pulmonary veno-occlusive disease
Cases of pulmonary oedema have been reported with vasodilators (mainly prostacyclins) when used in patients with pulmonary veno-occlusive disease. Consequently, should signs of pulmonary oedema occur when Tracleer is administered in patients with PAH, the possibility of associated veno-occlusive disease should be considered. In the post-marketing period there have been rare reports of pulmonary oedema in patients treated with Tracleer who had a suspected diagnosis of pulmonary veno-occlusive disease.
Pulmonary arterial hypertension patients with concomitant left ventricular failure
No specific study has been performed in patients with pulmonary hypertension and concomitant left ventricular dysfunction. However, 1,611 patients (804 bosentan- and 807 placebo-treated patients) with severe chronic heart failure (CHF) were treated for a mean duration of 1.5 years in a placebo-controlled study (study AC-052-301/302 [ENABLE 1 & 2]). In this study there was an increased incidence of hospitalisation due to CHF during the first 4–8 weeks of treatment with bosentan, which could have been the result of fluid retention. In this study, fluid retention was manifested by early weight gain, decreased haemoglobin concentration and increased incidence of leg oedema. At the end of this study, there was no difference in overall hospitalisations for heart failure nor in mortality between bosentan- and placebo-treated patients. Consequently, it is recommended that patients be monitored for signs of fluid retention (e.g., weight gain), especially if they concomitantly suffer from severe systolic dysfunction. Should this occur, starting treatment with diuretics is recommended, or the dose of existing diuretics should be increased. Treatment with diuretics should be considered in patients with evidence of fluid retention before the start of treatment with Tracleer.
Pulmonary arterial hypertension associated with HIV infection
There is limited clinical study experience with the use of Tracleer in patients with PAH associated with HIV infection, treated with antiretroviral medicinal products (see section 5.1). An interaction study between bosentan and lopinavir+ritonavir in healthy subjects showed increased plasma concentrations of bosentan, with the maximum level during the first 4 days of treatment (see section 4.5). When treatment with Tracleer is initiated in patients who require ritonavir-boosted protease inhibitors, the patient's tolerability of Tracleer should be closely monitored with special attention, at the beginning of the initiation phase, to the risk of hypotension and to liver function tests. An increased long-term risk of hepatic toxicity and haematological adverse events cannot be excluded when bosentan is used in combination with antiretroviral medicinal products. Due to the potential for interactions related to the inducing effect of bosentan on CYP450 (see section 4.5), which could affect the efficacy of antiretroviral therapy, these patients should also be monitored carefully regarding their HIV infection.
Pulmonary hypertension secondary to chronic obstructive pulmonary disease (COPD)
Safety and tolerability of bosentan was investigated in an exploratory, uncontrolled 12-week study in 11 patients with pulmonary hypertension secondary to severe COPD (stage III of GOLD classification). An increase in minute ventilation and a decrease in oxygen saturation were observed, and the most frequent adverse event was dyspnoea, which resolved with discontinuation of bosentan.
Concomitant use with other medicinal products
Glibenclamide: Tracleer should not be used concomitantly with glibenclamide, due to an increased risk of elevated liver aminotransferases (see section 4.5). An alternative antidiabetic medicinal product should be used in patients in whom an antidiabetic treatment is indicated.
Fluconazole: concomitant use of Tracleer with fluconazole is not recommended (see section 4.5). Although not studied, this combination may lead to large increases in plasma concentrations of bosentan.
Rifampicin: co-administration of Tracleer with rifampicin is not recommended (see section 4.5).
Concomitant administration of both a CYP3A4 inhibitor and a CYP2C9 inhibitor with Tracleer should be avoided (see section 4.5).
4.5 Interaction With Other Medicinal Products And Other Forms Of Interaction
Bosentan is an inducer of the cytochrome P450 (CYP) isoenzymes CYP2C9 and CYP3A4. In vitro data also suggest an induction of CYP2C19. Consequently, plasma concentrations of substances metabolised by these isoenzymes will be decreased when Tracleer is co-administered. The possibility of altered efficacy of medicinal products metabolised by these isoenzymes should be considered. The dosage of these products may need to be adjusted after initiation, dose change or discontinuation of concomitant Tracleer treatment.
Bosentan is metabolised by CYP2C9 and CYP3A4. Inhibition of these isoenzymes may increase the plasma concentration of bosentan (see ketoconazole). The influence of CYP2C9 inhibitors on bosentan concentration has not been studied. The combination should be used with caution. Concomitant administration with fluconazole, which inhibits mainly CYP2C9, but to some extent also CYP3A4, could lead to large increases in plasma concentrations of bosentan. The combination is not recommended. For the same reason, concomitant administration of both a potent CYP3A4 inhibitor (such as ketoconazole, itraconazole or ritonavir) and a CYP2C9 inhibitor (such as voriconazole) with Tracleer is not recommended.
Cyclosporine A: co-administration of Tracleer and cyclosporine A (a calcineurin inhibitor) is contraindicated (see section 4.3). Indeed, when co-administered, initial trough concentrations of bosentan were approximately 30-fold higher than those measured after bosentan alone. At steady state, bosentan plasma concentrations were 3- to 4-fold higher than with bosentan alone. The mechanism of this interaction is most likely inhibition of transport protein-mediated uptake of bosentan into hepatocytes by cyclosporine. The blood concentrations of cyclosporine A (a CYP3A4 substrate) decreased by approximately 50%. This is most likely due to induction of CYP3A4 by bosentan.
Tacrolimus, sirolimus: co-administration of tacrolimus or sirolimus and Tracleer has not been studied in man but co-administration of tacrolimus or sirolimus and Tracleer may result in increased plasma concentrations of bosentan in analogy to co-administration with cyclosporine A. Concomitant Tracleer may reduce the plasma concentrations of tacrolimus and sirolimus. Therefore, concomitant use of Tracleer and tacrolimus or sirolimus is not advisable. Patients in need of the combination should be closely monitored for adverse events related to Tracleer and for tacrolimus and sirolimus blood concentrations.
Glibenclamide: co-administration of bosentan 125 mg twice daily for 5 days decreased the plasma concentrations of glibenclamide (a CYP3A4 substrate) by 40%, with potential significant decrease of the hypoglycaemic effect. The plasma concentrations of bosentan were also decreased by 29%. In addition, an increased incidence of elevated aminotransferases was observed in patients receiving concomitant therapy. Both glibenclamide and bosentan inhibit the bile salt export pump, which could explain the elevated aminotransferases. In this context, this combination should not be used (see section 4.4). No drug-drug interaction data are available with the other sulfonylureas.
Hormonal contraceptives: co-administration of bosentan 125 mg twice daily for 7 days with a single dose of oral contraceptive containing norethisterone 1 mg + ethinyl estradiol 35 mcg decreased the AUC of norethisterone and ethinyl estradiol by 14% and 31%, respectively. However, decreases in exposure were as much as 56% and 66%, respectively, in individual subjects. Therefore, hormone-based contraceptives alone, regardless of the route of administration (i.e., oral, injectable, transdermal or implantable forms), are not considered as reliable methods of contraception (see sections 4.4 and 4.6).
Warfarin: co-administration of bosentan 500 mg twice daily for 6 days decreased the plasma concentrations of both S-warfarin (a CYP2C9 substrate) and R-warfarin (a CYP3A4 substrate) by 29% and 38%, respectively. Clinical experience with concomitant administration of bosentan with warfarin in patients with pulmonary arterial hypertension did not result in clinically relevant changes in International Normalized Ratio (INR) or warfarin dose (baseline versus end of the clinical studies). In addition, the frequency of changes in warfarin dose during the studies due to changes in INR or due to adverse events was similar among bosentan- and placebo-treated patients. No dose adjustment is needed for warfarin and similar oral anticoagulant agents when bosentan is initiated, but intensified monitoring of INR is recommended, especially during bosentan initiation and the up-titration period.
Simvastatin: co-administration of bosentan 125 mg twice daily for 5 days decreased the plasma concentrations of simvastatin (a CYP3A4 substrate) and its active β-hydroxy acid metabolite by 34% and 46%, respectively. The plasma concentrations of bosentan were not affected by concomitant simvastatin. Monitoring of cholesterol levels and subsequent dosage adjustment should be considered.
Ketoconazole: co-administration for 6 days of bosentan 62.5 mg twice daily with ketoconazole, a potent CYP3A4 inhibitor, increased the plasma concentrations of bosentan approximately 2-fold. No dose adjustment of Tracleer is considered necessary. Although not demonstrated through in vivo studies, similar increases in bosentan plasma concentrations are expected with the other potent CYP3A4 inhibitors (such as itraconazole or ritonavir). However, when combined with a CYP3A4 inhibitor, patients who are poor metabolisers of CYP2C9 are at risk of increases in bosentan plasma concentrations that may be of higher magnitude, thus leading to potential harmful adverse events.
Rifampicin: co-administration in 9 healthy subjects for 7 days of bosentan 125 mg twice daily with rifampicin, a potent inducer of CYP2C9 and CYP3A4, decreased the plasma concentrations of bosentan by 58%, and this decrease could achieve almost 90% in an individual case. As a result, a significantly reduced effect of bosentan is expected when it is co-administered with rifampicin. Data on other CYP3A4 inducers, e.g., carbamazepine, phenobarbital, phenytoin and St. John's wort are lacking, but their concomitant administration is expected to lead to reduced systemic exposure to bosentan. A clinically significant reduction of efficacy cannot be excluded.
Epoprostenol: limited data obtained from a study (AC-052-356 [BREATHE-3]) in which 10 paediatric patients received the combination of bosentan and epoprostenol indicate that after both single- and multiple-dose administration, the Cmax and AUC values of bosentan were similar in patients with or without continuous infusion of epoprostenol (see section 5.1).
Sildenafil: co-administration of bosentan 125 mg twice daily (steady state) with sildenafil 80 mg three times a day (at steady state) concomitantly administered during 6 days in healthy volunteers resulted in a 63% decrease in the sildenafil AUC and a 50% increase in the bosentan AUC. Caution is recommended in the case of co-administration.
Digoxin: co-administration for 7 days of bosentan 500 mg twice daily with digoxin decreased the AUC, Cmax and Cmin of digoxin by 12%, 9% and 23%, respectively. The mechanism for this interaction may be induction of P-glycoprotein. This interaction is unlikely to be of clinical relevance.
Lopinavir+ritonavir (and other ritonavir-boosted protease inhibitors): co-administration of bosentan 125 mg twice daily and lopinavir+ritonavir 400+100 mg twice daily for 9.5 days in healthy volunteers resulted in initial trough plasma concentrations of bosentan that were approximately 48-fold higher than those measured after bosentan administered alone. On day 9, plasma concentrations of bosentan were approximately 5-fold higher than with bosentan administered alone. Inhibition by ritonavir of transport protein-mediated uptake into hepatocytes and of CYP3A4, thereby reducing the clearance of bosentan, most likely causes this interaction. When administered concomitantly with lopinavir+ritonavir, or other ritonavir-boosted protease inhibitors, the patient's tolerability of Tracleer should be monitored.
After co-administration of bosentan for 9.5 days, the plasma exposures of lopinavir and ritonavir decreased to a clinically non significant extent (by approximately 14% and 17%, respectively). However, full induction by bosentan might not have been reached and a further decrease of protease inhibitors cannot be excluded. Appropriate monitoring of the HIV therapy is recommended. Similar effects would be expected with other ritonavir-boosted protease inhibitors (see section 4.4).
Other antiretroviral agents: no specific recommendation can be made with regard to other available antiretroviral agents due to the lack of data. It is emphasised that due to the marked hepatotoxicity of nevirapine, which could accumulate with bosentan liver toxicity, this combination is not recommended.
4.6 Pregnancy And Lactation
Pregnancy
Studies in animals have shown reproductive toxicity (teratogenicity, embryotoxicity, see section 5.3). There are no reliable data on the use of Tracleer in pregnant women. The potential risk for humans is still unknown. Tracleer is contraindicated in pregnancy (see section 4.3).
Use in women of child-bearing potential
Before the initiation of Tracleer treatment in women of child-bearing potential, the absence of pregnancy should be checked, appropriate advice on reliable methods of contraception provided, and reliable contraception initiated. Patients and prescribers must be aware that due to potential pharmacokinetic interactions, Tracleer may render hormonal contraceptives ineffective (see section 4.5). Therefore, women of child-bearing potential must not use hormonal contraceptives (including oral, injectable, transdermal or implantable forms) as the sole method of contraception but must use an additional or an alternative reliable method of contraception. If there is any doubt about what contraceptive advice should be given to the individual patient, consultation with a gynaecologist is recommended. Because of possible hormonal contraception failure during Tracleer treatment, and also bearing in mind the risk that pulmonary hypertension severely deteriorates with pregnancy, monthly pregnancy tests during treatment with Tracleer are recommended to allow early detection of pregnancy.
Use during lactation
It is not known whether bosentan is excreted into human breast milk. Breast-feeding is not recommended during treatment with Tracleer.
4.7 Effects On Ability To Drive And Use Machines
No studies on the effect of Tracleer on the ability to drive and use machines have been performed. Tracleer may cause dizziness, which could affect the ability to drive or use machines.
4.8 Undesirable Effects
In 20 placebo-controlled studies, conducted in a variety of therapeutic indications, a total of 2,486 patients were treated with bosentan at daily doses ranging from 100 mg to 2000 mg and 1,838 patients were treated with placebo. The mean treatment duration was 45 weeks. The most commonly reported adverse drug reactions (as occurring in at least 1% of patients on bosentan and at a frequency at least 0.5% more than on placebo) are headache (11.5% vs 9.8%), oedema/fluid retention (13.2% vs 10.9%), abnormal liver function test (10.9% vs 4.6%) and anaemia/haemoglobin decrease (9.9% vs 4.9%).
Treatment with bosentan has been associated with dose-dependent elevations in liver aminotransferases and decreases in haemoglobin concentration (see section 4.4, Special warnings and precautions for use).
Adverse reactions/undesirable effects in 20 placebo-controlled studies with bosentan are ranked according to frequency using the following convention: very common (Italics, with frequency categories based on adverse event reporting rates on bosentan in the 20 placebo-controlled studies.
Frequency categories do not account for other factors, including varying study duration, pre-existing conditions, and baseline patient characteristics. Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness. No clinically relevant differences in undesirable effects were observed between the overall dataset and the approved indications.
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1 Frequency cannot be estimated from the available data.
2 Hypersensitivity reactions were reported in 9.9% of patients on bosentan and 9.1% of patients on placebo.
3 Headache was reported in 11.5% of patients on bosentan and 9.8% of patients on placebo.
4 These types of reactions can also be related to the underlying disease.
5 Oedema or fluid retention was reported in 13.2% of patients on bosentan and 10.9% of patients on placebo.
In the post-marketing period rare cases of unexplained hepatic cirrhosis were reported after prolonged therapy with Tracleer in patients with multiple co-morbidities and therapies with medicinal products. There have also been rare reports of liver failure. These cases reinforce the importance of strict adherence to the monthly schedule for monitoring of liver function for the duration of treatment with Tracleer (see section 4.4).
Uncontrolled studies in paediatric patients with PAH (AC-052-356 [BREATHE-3]; AC-052-365 [FUTURE 1])
The safety profile in this population (BREATHE-3: n = 19, bosentan 2 mg/kg twice daily; treatment duration 12 weeks; FUTURE 1: n = 36, bosentan 2 mg/kg twice daily for 4 weeks followed by 4 mg/kg twice daily; treatment duration 12 weeks) was similar to that observed in the pivotal trials in adult patients with PAH. In BREATHE-3, the most frequent adverse events were flushing (21%), headache, and abnormal liver function test (each 16%). In FUTURE 1, the most frequent adverse events were infections (33%) and abdominal pain/discomfort (19%). There were no cases of liver enzyme elevations in the FUTURE 1 study.
Laboratory abnormalities
Liver test abnormalities
In the clinical programme, dose-dependent elevations in liver aminotransferases generally occurred within the first 26 weeks of treatment, usually developed gradually, and were mainly asymptomatic. In the post-marketing period rare cases of liver cirrhosis and liver failure have been reported.
The mechanism of this adverse effect is unclear. These elevations in aminotransferases may reverse spontaneously while continuing treatment with the maintenance dose of Tracleer or after dose reduction, but interruption or cessation may be necessary (see section 4.4).
In the 20 integrated placebo-controlled studies, elevations in liver aminotransferases
Haemoglobin
A decrease in haemoglobin concentration to below 10 g/dL from baseline was reported in 8.0% of bosentan-treated patients and 3.9% of placebo-treated patients (see section 4.4).
4.9 Overdose
Bosentan has been administered as a single dose of up to 2400 mg to healthy subjects and up to 2000 mg/day for 2 months in patients with a disease other than pulmonary hypertension. The most common adverse event was headache of mild to moderate intensity.
Massive overdose may result in pronounced hypotension requiring active cardiovascular support. In the post-marketing period there was one reported overdose of 10,000 mg of Tracleer taken by an adolescent male patient. He had symptoms of nausea, vomiting, hypotension, dizziness, sweating and blurred vision. He recovered completely within 24 hours with blood pressure support. Note: bosentan is not removed through dialysis.
5. Pharmacological Properties
5.1 Pharmacodynamic Properties
Pharmacotherapeutic group: other antihypertensives, ATC code: C02KX01
Mechanism of action
Bosentan is a dual endothelin receptor antagonist (ERA) with affinity for both endothelin A and B (ETA and ETB) receptors. Bosentan decreases both pulmonary and systemic vascular resistance resulting in increased cardiac output without increasing heart rate.
The neurohormone endothelin-1 (ET-1) is one of the most potent vasoconstrictors known and can also promote fibrosis, cell proliferation, cardiac hypertrophy and remodelling, and is pro-inflammatory. These effects are mediated by endothelin binding to ETA and ETB receptors located in the endothelium and vascular smooth muscle cells. ET-1 concentrations in tissues and plasma are increased in several cardiovascular disorders and connective tissue diseases, including pulmonary arterial hypertension, scleroderma, acute and chronic heart failure, myocardial ischaemia, systemic hypertension and atherosclerosis, suggesting a pathogenic role of ET-1 in these diseases. In pulmonary arterial hypertension and heart failure, in the absence of endothelin receptor antagonism, elevated ET-1 concentrations are strongly correlated with the severity and prognosis of these diseases.
Bosentan competes with the binding of ET-1 and other ET peptides to both ETA and ETB receptors, with a slightly higher affinity for ETA receptors (Ki = 4.1–43 nanomolar) than for ETB receptors (Ki = 38-730 nanomolar). Bosentan specifically antagonises ET receptors and does not bind to other receptors.
Efficacy
Animal models
In animal models of pulmonary hypertension, chronic oral administration of bosentan reduced pulmonary vascular resistance and reversed pulmonary vascular and right ventricular hypertrophy. In an animal model of pulmonary fibrosis, bosentan reduced collagen deposition in the lungs.
Efficacy in adult patients with pulmonary arterial hypertension
Two randomised, double-blind, multi-centre, placebo-controlled studies have been conducted in 32 (study AC-052-351) and 213 (study AC-052-352 [BREATHE-1]) adult patients with WHO functional class III–IV pulmonary arterial hypertension (primary pulmonary hypertension or pulmonary hypertension secondary mainly to scleroderma). After 4 weeks of bosentan 62.5 mg twice daily, the maintenance doses studied in these studies were 125 mg twice daily in AC-052-351, and 125 mg twice daily and 250 mg twice daily in AC-052-352.
Bosentan was added to patients' current therapy, which could include a combination of anticoagulants, vasodilators (e.g., calcium channel blockers), diuretics, oxygen and digoxin, but not epoprostenol. Control was placebo plus current therapy.
The primary endpoint for each study was change in 6-minute walk distance at 12 weeks for the first study and 16 weeks for the second study. In both studies, treatment with bosentan resulted in significant increases in exercise capacity. The placebo-corrected increases in walk distance compared to baseline were 76 metres (p = 0.02; t-test) and 44 metres (p = 0.0002; Mann-Whitney U test) at the primary endpoint of each study, respectively. The differences between the two groups, 125 mg twice daily and 250 mg twice daily, were not statistically significant but there was a trend towards improved exercise capacity in the group treated with 250 mg twice daily.
The improvement in walk distance was apparent after 4 weeks of treatment, was clearly evident after 8 weeks of treatment and was maintained for up to 28 weeks of double-blind treatment in a subset of the patient population.
In a retrospective responder analysis based on change in walking distance, WHO functional class and dyspnoea of the 95 patients randomised to bosentan 125 mg twice daily in the placebo-controlled studies, it was found that at week 8, 66 patients had improved, 22 were stable and 7 had deteriorated. Of the 22 patients stable at week 8, 6 improved at week 12/16 and 4 deteriorated compared with baseline. Of the 7 patients who deteriorated at week 8, 3 improved at week 12/16 and 4 deteriorated compared with baseline.
Invasive haemodynamic parameters were assessed in the first study only. Treatment with bosentan led to a significant increase in cardiac index associated with a significant reduction in pulmonary artery pressure, pulmonary vascular resistance and mean right atrial pressure.
A reduction in symptoms of pulmonary arterial hypertension was observed with bosentan treatment. Dyspnoea measurement during walk tests showed an improvement in bosentan-treated patients. In the AC-052-352 study, 92% of the 213 patients were classified at baseline as WHO functional class III and 8% as class IV. Treatment with bosentan led to a WHO functional class improvement in 42.4% of patients (placebo 30.4%). The overall change in WHO functional class during both studies was significantly better among bosentan-treated patients as compared with placebo-treated patients. Treatment with bosentan was associated with a significant reduction in the rate of clinical worsening compared with placebo at 28 weeks (10.7% vs 37.1%, respectively; p = 0.0015).
In a randomised, double-blind, multi-centre, placebo-controlled study (AC-052-364 [EARLY]), 185 PAH patients in WHO functional class II (mean baseline 6-minute walk distance of 435 metres) received bosentan 62.5 mg twice daily for 4 weeks followed by 125 mg twice daily (n = 93), or placebo (n = 92) for 6 months. Enrolled patients were PAH-treatment-naïve (n = 156) or on a stable dose of sildenafil (n = 29). The co-primary endpoints were percentage change from baseline in pulmonary vascular resistance (PVR) and change from baseline in 6-minute walk distance to Month 6 versus placebo. The table below illustrates the pre-specified protocol analyses.
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