Long-term safety and tolerability of ambrisentan treatment for pediatric patients with pulmonary arterial hypertension: An open-label extension study

This open-label, extension study assessed long-term safety, tolerability, and efficacy of ambrisentan in a pediatric population (age 8- < 18 years) with pulmonary arterial hypertension (PAH). Following completion of a 6-month, randomized study, participants entered the long-term extension at individualized ambrisentan dosages (2.5/5/7.5 or 10 mg/day). Safety assessments included adverse events (AEs), AEs of special interest, and serious AEs (SAEs); efficacy outcomes included 6-min walking distance (6MWD) and World Health Organization functional class (WHO FC). Thirty-eight of 41 (93%) randomized study participants entered the extension; 21 (55%) completed (reaching age 18 years). Most participants received concomitant phosphodiesterase-5 inhibitors (n = 25/38, 66%). Median ambrisentan exposure was 3.5 years. Most participants experienced ≥ 1 AE (n = 34/38, 89%), and 21 (55%) experienced SAEs, most commonly worsening PAH (n = 3/38, 8%), acute cardiac failure, pneumonia, or anemia (n = 2/38; 5% each); none considered ambrisentan-related. Seven participants (18%) died, with recorded reasons (MedDRA preferred term): cardiac failure (n = 2), PAH (n = 2), COVID-19 (n = 1), acute right ventricular failure (n = 1), and failure to thrive (n = 1); median time to death: 5.2 years. Anemia and hepatotoxicity AEs were generally mild to moderate and did not require ambrisentan dose adjustment. Assessed at study end in 29 participants (76%), mean 6MWD improved by 17% (standard deviation: 34.3%), and all (29/29, 100%) had improved or unchanged WHO FC.    Conclusion: Long-term weight-based ambrisentan dosing, alone or combined with other PAH therapies in children with PAH aged 8- < 18 years, exhibited tolerability and clinical improvements consistent with prior randomized study results.    Trial registration: NCT01342952, April 27, 2011. What is Known: • The endothelin receptor antagonist, ambrisentan, is indicated for treatment of pulmonary arterial hypertension (PAH). Previous studies have shown similar efficacy and tolerability in pediatric patients as in adults. What is New: • This open-label extension study assessed the long-term use of ambrisentan in pediatric patients (8-<18 years) with PAH, most of whom were also receiving recommended background PAH treatment. • Weight-based dosing of ambrisentan, given alone or in combination with other PAH therapies, was well tolerated with clinical improvements consistent with prior randomized study results.

A Novel Chitosan-coated Leciplex Loaded with Ambrisentan as a Possible Pulmonary Nanosystem: Optimization, Characterization, and Pharmacokinetics Assessments

The purpose of this research was to formulate, optimize, and characterize ambrisentan chitosan-coated LeciPlex (AMS-CTS-LPX) to increase the therapeutic effectiveness and bioavailability of ambrisentan. A central composite design (CCD) was implemented to assess the impact of various factors on the production of AMS-CTS-LPX and to identify the optimum formulation via the use of Design Expert® software. The assembly of AMS-CTS-LPX was conducted using a single-step process. Subsequently, the optimal formulation was chosen and subjected to further assessments. Further, a comparative pharmacokinetic study was carried out using a rat model. The optimized formulation exhibited an entrapment efficiency of 82.39%, with a diameter of 137.53 nm and a surface charge of +43.65 mV. Additionally, it had a sustained cumulative release of 90.41% after 8 h and showed good stability. The safety of AMS-CTS-LPX administered intratracheally was confirmed by in vivo histopathological studies. The pharmacokinetic investigations revealed a 5.6-fold increase in the bioavailability of AMS from the optimal AMS-CTS-LPX formulation compared to the oral AMS solution. Collectively, the results of the current study suggest that CTS-LPX may be beneficial as a pulmonary nanosystem for the administration of AMS.

The potential effect of ambrisentan as monotherapy and combined with tadalafil on diabetic erectile dysfunction in rats

INTRODUCTION

This study investigated the role of ambrisentan; the selective endothelin type-A receptor (ETAR) blocker on experimental diabetic erectile dysfunction in rats.

MATERIALS AND METHODS

Eighty-four adult male Sprague Albino rats were divided randomly into 7 groups. Three control groups received 1 mL saline, 0.2 mg/kg/d ambrisentan and 1.5 mg/kg/d tadalafil, respectively orally for 4 weeks. The remaining four groups were fed high fat diet for 14 days. Diabetes was induced by a single intra-peritoneal injection of 40 mg/kg streptozotocin. After 72 h, diabetes was confirmed by plasma glucose level ⩾250 mg/dL. Diabetic rats were divided randomly into four groups, numbered from 4 to 7. The fourth group was the diabetic-control group, while the fifth and sixth groups received ambrisentan and tadalafil respectively. The seventh group received a combination of both drugs. Treatment continued for 4 weeks then, copulatory, intracavernous pressure measurement, and laboratory tests were conducted.

RESULTS

In diabetic rats, ambrisentan and tadalafil improved fasting glucose, insulin, insulin resistance, testosterone, nitric oxide, and rho kinase (ROCK) values compared to diabetic group with the maximum improvement achieved in ambrisentan/tadalafil group (p < 0.05). Ambrisentan also enhanced ICP and improved latency to erection and number of mounts with a tolerable SBP. Yet, ambrisentan/tadalafil combined therapy resulted in deterioration in SBP with consecutive worsening in ICP and mating indices.

CONCLUSION

Ambrisentan showed significant therapeutic potential to prevent and improve diabetic ED in rats comparable to tadalafil.

Oral delivery of ambrisentan-loaded lipid-core nanocapsules as a novel approach for the treatment of pulmonary arterial hypertension

Ambrisentan (AMB) is an orphan drug approved for oral administration that has been developed for the treatment of pulmonary arterial hypertension (PAH), a chronic and progressive pathophysiological state that might result in death if left untreated. Lipid-core nanocapsules (LNCs) are versatile nanoformulations capable of loading lipophilic drugs for topical, vaginal, oral, intravenous, pulmonary, and nasal administration. Our hypothesis was to load AMB into these nanocapsules (LNC_amb) and test their effect on slowing or reducing the progression of monocrotaline-induced PAH in a rat model, upon oral administration. LNC_amb displayed a unimodal distribution of diameters (around 200 nm), negative zeta potential (-11.5 mV), high encapsulation efficiency (78%), spherical shape, and sustained drug release (50-60% in 24 h). The in vivo pharmacodynamic effect of the LNC_amb group was evaluated by observing the echocardiography, hemodynamic, morphometric, and histological data, which showed a significant decrease in PAH in this group, as compared to the control group (AMB_solution). LNC_amb showed the benefit of reversing systolic dysfunction and preventing vascular remodeling with greater efficacy than that observed in the control group. The originality and contribution of our work reveal the promising value of this nanoformulation as a novel therapeutic strategy for PAH treatment.

A randomized, double-blind, placebo-controlled study to evaluate sildenafil, ambrisentan combination therapy in pulmonary hypertension, particularly of Eisenmenger syndrome

Pulmonary arterial hypertension (PAH) - a complex and progressive disease that carries significant morbidity and mortality despite optimal medical treatment. Combination therapy for PAH can be more effective than monotherapy. The present randomized trial compared the safety and efficacy of sildenafil ambrisentan combination therapy with sildenafil monotherapy. Twenty-two patients of Eisenmenger syndrome and five patients of idiopathic PAH were randomized to two arms. There was a significant improvement in NYHA functional class and mean pulmonary artery pressure, while an insignificant improving trend was observed for 6-min walk distance and oxygen saturation, following the 12 weeks of combination therapy. An upfront combination therapy was found to be safe and effective in the management of PAH patients.

Synergic effect of atorvastatin and ambrisentan on sinusoidal and hemodynamic alterations in a rat model of NASH

In non-alcoholic steatohepatitis (NASH), decreased nitric oxide and increased endothelin-1 (ET-1, also known as EDN1) released by sinusoidal endothelial cells (LSEC) induce hepatic stellate cell (HSC) contraction and contribute to portal hypertension (PH). Statins improve LSEC function, and ambrisentan is a selective endothelin-receptor-A antagonist. We aimed to analyse the combined effects of atorvastatin and ambrisentan on liver histopathology and hemodynamics, together with assessing the underlying mechanism in a rat NASH model. Diet-induced NASH rats were treated with atorvastatin (10 mg/kg/day), ambrisentan (30 mg/kg/day or 2 mg/kg/day) or a combination of both for 2 weeks. Hemodynamic parameters were registered and liver histology and serum biochemical determinations analysed. Expression of proteins were studied by immunoblotting. Conditioned media experiments were performed with LSEC. HSCs were characterized by RT-PCR, and a collagen lattice contraction assay was performed. Atorvastatin and ambrisentan act synergistically in combination to completely normalize liver hemodynamics and reverse histological NASH by 75%. Atorvastatin reversed the sinusoidal contractile phenotype, thus improving endothelial function, whereas ambrisentan prevented the contractile response in HSCs by blocking ET-1 response. Additionally, ambrisentan also increased eNOS (also known as Nos3) phosphorylation levels in LSEC, via facilitating the stimulation of endothelin-receptor-B in these cells. Furthermore, the serum alanine aminotransferase of the combined treatment group decreased to normal levels, and this group exhibited a restoration of the HSC quiescent phenotype. The combination of atorvastatin and ambrisentan remarkably improves liver histology and PH in a diet-induced NASH model. By recovering LSEC function, together with inhibiting the activation and contraction of HSC, this combined treatment may be an effective treatment for NASH patients.

Summary: Combining atorvastatin with ambrisentan is safe and effective in reducing intrahepatic resistance and portal hypertension in an experimental model of NASH. This liver histology amelioration highlights a promising therapeutic strategy.

Endothelin antagonism and sodium glucose Co-transporter 2 inhibition. A potential combination therapeutic strategy for COVID-19

The novel coronavirus 2019 (COVID-19) infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global pandemic that requires a multi-faceted approach to tackle this unprecedent health crisis. Therapeutics to treat COVID-19 are an integral part of any such management strategy and there is a substantial unmet need for treatments for individuals most at risk of severe disease. This perspective review provides rationale of a combined therapeutic regimen of selective endothelin-A (ET-A) receptor antagonism and sodium glucose co-transporter-2 (SGLT-2) inhibition to treat COVID-19. Endothelin is a potent vasoconstrictor with pro-inflammatory and atherosclerotic effects. It is upregulated in a number of conditions including acute respiratory distress syndrome and cardiovascular disease. Endothelin mediates vasocontractility via endothelin (ET-A and ET-B) receptors on vascular smooth muscle cells (VSMCs). ET-B receptors regulate endothelin clearance and are present on endothelial cells, where in contrast to their role on VSMCs, mediate vasodilation. Therefore, selective endothelin-A (ET-A) receptor inhibition is likely the optimal approach to attenuate the injurious effects of endothelin and may reduce ventilation-perfusion mismatch and pulmonary inflammation, whilst improving pulmonary haemodynamics and oxygenation. SGLT-2 inhibition may dampen inflammatory cytokines, reduce hyperglycaemia if present, improve endothelial function, cardiovascular haemodynamics and cellular bioenergetics. This combination therapeutic approach may therefore have beneficial effects to mitigate both the pulmonary, metabolic and cardiorenal manifestations of COVID-19. Given these drug classes include medicines licensed to treat heart failure, diabetes and pulmonary hypertension respectively, information regarding their safety profile is established. Randomised controlled clinical trials are the best way to determine efficacy and safety of these medicines in COVID-19.

Effect of ambrisentan on echocardiographic and Doppler measures from patients in China with pulmonary arterial hypertension

BACKGROUND

We retrospectively evaluated the echocardiographic data of ambrisentan-treated patients with pulmonary arterial hypertension (PAH) (NCT01808313).

METHODS

Change from baseline in right ventricle (RV) systolic function, right heart structure, and pulmonary artery systolic pressure (PASP) prognosis to Weeks 12 and 24 was evaluated by echocardiography.

RESULTS

In the overall population, the mean tissue Doppler-derived tricuspid lateral annular systolic velocity (S') increased by 0.6 cm/s at both Weeks 12 (p < 0.001) and 24 (p = 0.004) and tricuspid annular plane systolic excursion increased by 0.13 cm at Week 12 and 0.15 cm at Week 24 (both p < 0.001). A marked decrease in transverse and longitudinal RV and RA diameter at Weeks 12 and 24 was observed. A significant decrease in diastolic eccentricity index at both Weeks 12 (-0.1; p = 0.02) and 24 (-0.1; p = 0.001). The decrease in PASP from baseline was significant at both Weeks 12 (-9.5 mmHg; p<0.001) and 24 (-7.6 mmHg; p<0.001), while a decrease in the estimated right atrium pressure was found to be significant at Week 24 (-0.8mmHg; p = 0.01).

CONCLUSION

Significant improvements in a number of RV echocardiographic parameters were observed at Weeks 12 and 24 after ambrisentan treatment in patients with PAH.

The Clinical Efficacy of Endothelin Receptor Antagonists in Patients with Pulmonary Arterial Hypertension

Therapeutic strategies for pulmonary arterial hypertension (PAH) have made remarkable progress over the last two decades. Currently, 3 types of drugs can be used to treat PAH; prostacyclins, phosphodiesterase 5 inhibitors, and endothelin receptor antagonists (ERA). In Japan, the first generation ERA bosentan was reimbursed in 2005, following which the 2nd generation ERAs ambrisentan and macitentan were reimbursed in 2009 and 2015, respectively. The efficacy of each ERA on hemodynamics in PAH patients remains to be elucidated. The aims of this study were to evaluate the hemodynamic effects of ERAs and compare these effects among each generation of ERAs.We retrospectively examined the clinical parameters of 42 PAH patients who were prescribed an ERA (15 bosentan, 12 ambrisentan, and 15 macitentan) and who underwent a hemodynamic examination before and after ERA introduction at our institution from January 2007 to July 2019.In a total of 42 patients, mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) were significantly decreased and cardiac index was significantly increased after ERA introduction (P < 0.001) and the World Health Organization-Functional class (WHO-Fc) was significantly improved after ERA introduction (P = 0.005). Next, in a comparison between 1st and 2nd generation ERAs, 2nd generation ERAs were found to have brought about greater improvements in hemodynamic parameters (mPAP and PVR. P < 0.01), heart rate, brain natriuretic peptide, arterial oxygen saturation, and mixed venous oxygen saturation than the 1st generation ERA bosentan.We conclude that all ERAs could successfully improve the hemodynamics of PAH patients and that the newer generation ERAs, ambrisentan and macitentan, seemed to be preferable to bosentan.

muLTi-Arm Therapeutic study in pre-ICu patients admitted with Covid-19-Experimental drugs and mechanisms (TACTIC-E): A structured summary of a study protocol for a randomized controlled trial

Objectives

To determine if a specific intervention reduces the composite of progression of patients with COVID-19-related disease to organ failure or death as measured by time to incidence of any one of the following: death, invasive mechanical ventilation, ECMO, cardiovascular organ support (inotropes or balloon pump), or renal failure (estimated Cockcroft Gault creatinine clearance <15ml/min).

Trial design

Randomised, parallel arm, open-label, adaptive platform Phase 2/3 trial of potential disease modifying therapies in patients with late stage 1/stage 2 COVID-19-related disease, with a diagnosis based either on a positive assay or high suspicion of COVID-19 infection by clinical, laboratory and radiological assessment.

Participants

Patients aged 18 and over, with a clinical picture strongly suggestive of COVID-19-related disease (with/without a positive COVID-19 test) AND a risk count (as defined below) >3 OR ≥3 if risk count includes “Radiographic severity score >3”. A risk count is calculated by the following features on admission (1 point for each): radiographic severity score >3, male gender, non-white ethnicity, diabetes, hypertension, neutrophils >8.0 x10⁹/L, age >40 years and CRP >40 mg/L.

Patients should be considered an appropriate subject for intervention with immunomodulatory or other disease modifying agents in the opinion of the investigator and are able to swallow capsules or tablets. The complete inclusion and exclusion criteria as detailed in the Additional file 1 should be fulfilled. Drug specific inclusion and exclusion criteria will also be applied to the active arms. Patients will be enrolled prior to the need for invasive mechanical ventilation, cardiac or renal support. Participants will be recruited across multiple centres in the UK including initially at Cambridge University Hospitals NHS Foundation Trust and St George’s University NHS Foundation Trust. Other centres will be approached internationally in view of the evolving pandemic.

Intervention and comparator

There is increasing evidence of the role of immunomodulation in altering the course of COVID-19. Additionally, various groups have demonstrated the presence of pulmonary shunting in patients with COVID-19 as well as other cardiovascular complications. TACTIC-E will assess the efficacy of the novel immunomodulatory agent EDP1815 versus the approved cardio-pulmonary drugs, Dapagliflozin in combination with Ambrisentan versus the prevailing standard of care.

EDP1815 will be given as 2 capsules twice daily (1.6 x 10¹¹ cells) for up to 7 days with the option to extend up to 14 days at the discretion of the principal investigator or their delegate, if the patient is felt to be clinically responding to treatment, is tolerating treatment, and is judged to be likely to benefit from a longer treatment course. Ambrisentan 5mg and Dapagliflozin 10mg will be given in combination once daily orally for up to maximum of 14 days. Patients will be randomised in a 1:1:1 ratio across treatments. Each active arm will be compared with standard of care alone. Additional arms may be added as the trial progresses. No comparisons will be made between active arms in this platform trial.

Main outcomes

The primary outcome is the incidence (from baseline up to Day 14) to the occurrence of the any one of the following events: death, invasive mechanical ventilation, extra corporeal membrane oxygenation, cardiovascular organ support (inotropes or balloon pump), or renal failure (estimated Cockcroft Gault creatinine clearance <15ml/min).

Randomisation

Eligible patients will be randomised using a central web-based randomisation service (Sealed Envelope) in a 1:1:1 ratio, stratified by site to one of the treatment arms or standard of care.

Blinding (masking)

This is an open-label trial. Data analysis will not be blinded.

Numbers to be randomised (sample size)

There is no fixed sample size for this study. There will be an early biomarker-based futility analysis performed at a point during the study. If this biomarker futility analysis is not conclusive, then a second futility analysis based on clinical endpoints will be performed after approximately 125 patients have been recruited per arm. Provisionally, further analyses of clinical endpoints will be performed after 229 patients per active arm and later 469 patients per arm have been recruited. Further additional analyses may be triggered by the independent data monitoring committee.

Trial Status

TACTIC-E Protocol version number 1.0 date May 27^th, 2020. Recruitment starts on the 3^rd of July 2020. The end trial date will be 18 months after the last patient’s last visit and cannot be accurately predicted at this time.

Trial registration

Registered on EU Clinical Trials Register EudraCT Number: 2020-002229-27 registered: 9 June 2020.

The trial was also registered on ClinicalTrials.gov (NCT04393246) on 19 May 2020.

Full protocol

The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest in expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.

Efficacy and safety of ambrisentan in Chinese patients with connective tissue disease-pulmonary arterial hypertension: a post-hoc analysis

BACKGROUND

The efficacy and safety of ambrisentan has been previously evaluated in Chinese patients with pulmonary arterial hypertension (PAH). This post-hoc analysis assessed the efficacy and safety of ambrisentan in a subgroup of connective tissue disease (CTD) patients with PAH.

METHODS

In this open-label, single-arm study, patients received ambrisentan 5 mg once daily for 12 weeks, followed by 12-week dose titration period (dose up to 10 mg). Efficacy endpoints included change from baseline in exercise capacity (measured by 6-min walk test [6MWT]), N-terminal pro B type natriuretic peptide (NT-proBNP) plasma levels, WHO Functional Class (FC) and Borg Dyspnoea Index (BDI) scores from baseline to weeks 12 and 24. Safety endpoints included time to clinical worsening and incidence of adverse events (AEs).

RESULTS

In total, 71 Chinese patients with CTD-PAH were included in this analysis. Ambrisentan treatment significantly improved exercise capacity (6MWT) from baseline (mean: 366.4 m) to week 12 (63.8 m, p < 0.001) and week 24 (73.2 m, p < 0.001). A significant reduction in NT-proBNP levels was observed from baseline (mean: 1837.5 ng/L) to week 12 (- 1156.8 ng/L, p < 0.001) and week 24 (- 1095.5 ng/L, p < 0.001). BDI scores decreased significantly at week 12 (- 0.6, p < 0.001) and week 24 (- 0.4, p = 0.002) from baseline (mean: 2.7). The WHO FC improved in 29 (40.8%) and 34 (47.9%) patients at weeks 12 and 24, respectively. Adverse events were reported in 52 (73.2%) patients. One patient (1.4%) experienced clinical worsening at week 24.

CONCLUSION

Ambrisentan showed significant improvement in exercise capacity and no clinical worsening in the majority of Chinese patients with CTD-PAH in the 24-week treatment period. The AEs observed in the CTD-PAH subgroup were consistent with the known safety profile of ambrisentan in the overall Chinese PAH population.

TRIAL REGISTRATION

ClinicalTrial.gov Identifier, https://clinicaltrials.gov/, NCT01808313 Registration date (first time): February 28, 2013.

Endothelin receptor antagonists alleviate blood-brain barrier disruption and cerebral edema in a mouse model of traumatic brain injury: A comparison between bosentan and ambrisentan

Traumatic brain injury (TBI) is induced by the immediate physical disruption of brain tissue. TBI causes disruption of the blood-brain barrier (BBB) and brain edema. In the cerebrospinal fluid (CSF) of TBI patients, endothelin-1 (ET-1) is increased, suggesting that ET-1 aggravates TBI-induced brain damage. In this study, the effect of bosentan (ET_A/ET_B antagonist) and ambrisentan (ET_A antagonist) on BBB dysfunction and brain edema were examined in a mouse model of TBI using lateral fluid percussion injury (FPI). FPI to the mouse cerebrum increased the expression levels of ET-1 and ET_B receptors. Administration of bosentan (3 or 15 mg/kg/day) and ambrisentan (0.1 or 0.5 mg/kg/day) at 6 and 24 h after FPI ameliorated BBB disruption and cerebral brain edema. Delayed administration of bosentan from 2 days after FPI also reduced BBB disruption and brain edema, while ambrisentan had no significant effects. FPI-induced expression levels of ET-1 and ET_B receptors were reduced by bosentan, but not by ambrisentan. In cultured mouse astrocytes and brain microvessel endothelial cells, ET-1 (100 nM) increased prepro--ET-1 mRNA, which was inhibited by bosentan, but not by ambrisentan. FPI-induced alterations of the expression levels of matrix metalloproteinase-9, vascular endothelial growth factor-A, and angiopoietin-1 in the mouse cerebrum were reduced by delayed administration of bosentan, while ambrisentan had no significant effects. These results suggest that ET antagonists are effective in improving BBB disruption and cerebral edema in TBI patients and that an ET_A/ET_B non-selective type of antagonists is more effective.

Ambrisentan use in a HIV-1 infected patient with end-stage renal disease and pulmonary hypertension: minimal removal by hemodialysis - a case report

BACKGROUND

Ambrisentan is a selective endothelin receptor antagonist used for the treatment of pulmonary arterial hypertension (PAH). Little is known about ambrisentan removal by hemodialysis in patients with end-stage renal disease (ESRD).

CASE PRESENTATION

A 53-year-old woman with HIV/hepatitis C virus (HCV) co-infection, PAH and ESRD on regular hemodialyis was admitted in our hospital due to refractory heart failure while on treatment with bosentan (125 mg twice daily) and tadalafil (20 mg once daily) for PAH and antiretroviral treatment (cART) including darunavir/cobicistat (800/150 mg once daily). Excessive exposure to bosentan due to drug interactions between bosentan and darunavir/cobicistat was suspected. Bosentan was replaced by ambrisentan, with progressive improvement in her clinical condition. Pre- and postdialyzer cocentrations of ambrisentan in plasma were determined and hemodialysis extraction ratio for ambrisentan was 2%.

CONCLUSIONS

Our results suggest that hemodialysis results in minimal ambrisentan removal, and therefore no specific ambrisentan dosage adjustment seems to be required in ESRD patients undergoing hemodialysis.

Early treatment with ambrisentan of mildly elevated mean pulmonary arterial pressure associated with systemic sclerosis: a randomized, controlled, double-blind, parallel group study (EDITA study)

Objective

The objective of this randomized, placebo-controlled, double-blind, parallel group, trial was to assess the effect of ambrisentan on mean pulmonary arterial pressure (mPAP) in patients with systemic sclerosis (SSc) and mildly elevated pulmonary hypertension (PH).

Methods

Thirty-eight SSc patients with mildly elevated mPAP at rest between 21 and 24 mmHg and/or > 30 mmHg during low-dose exercise were randomly assigned to treatment with either ambrisentan 5–10 mg/day or placebo. Right heart catheterization and further clinical parameters were assessed at baseline and after 6 months. The primary endpoint was the difference of mPAP change at rest between groups.

Results

After 6 months, the two groups did not differ in the primary endpoint (ambrisentan mPAP − 1 ± 6.4 mmHg vs. placebo − 0.73 ± 3.59 mmHg at rest, p = 0.884). However, three patients from the placebo group but none of the ambrisentan group progressed to SSc-associated pulmonary arterial hypertension. Furthermore, ambrisentan treatment showed significant improvements in the secondary endpoints cardiac index (CI) and pulmonary vascular resistance (PVR) at rest (CI 0.36 ± 0.66 l/min/m² vs. − 0.31 ± 0.71 l/min/m², p = 0.010; PVR − 0.70 ± 0.78 WU vs. 0.01 ± 0.71 WU, p = 0.012) and during exercise (CI 0.7 ± 0.81 l/min/m² vs. − 0.45 ± 1.36 l/min/m², p = 0.015; PVR − 0.84 ± 0.48 WU vs. − 0.0032 ± 0.34 WU, p < 0.0001).

Conclusion

This is the first randomized, double-blind, placebo-controlled study testing the effect of ambrisentan in patients with mildly elevated mPAP and/or exercise PH. The primary endpoint change in mPAP did only tendentially improve in the ambrisentan group, but the significant improvement of other hemodynamic parameters points to a possible benefit of ambrisentan and will be helpful to design future trials.

Trial registration

www.ClinicalTrials.gov, unique identifier NCT: NCT02290613, registered 14^th of November 2014.

Safety and Efficacy of Ambrisentan-Phosphodiesterase Type 5 (PDE5) Inhibitor Combination Therapy for Japanese Pulmonary Arterial Hypertension Patients in Real-World Clinical Practice

Background: This retrospective study was conducted to evaluate the safety and efficacy of ambrisentan combination therapy with phosphodiesterase type 5 (PDE5) inhibitors in Japanese patients with pulmonary arterial hypertension (PAH).

Methods and Results: PAH patients who received ambrisentan for the first time in combination with a PDE5 inhibitor between January 2013 and the end of August 2015 were included in this study. Adverse drug reaction (ADR) safety analysis, as well as the efficacy analysis focusing on changes in clinical parameters, were investigated for overall cases and cases stratified by patient background. Forty-eight consecutive patients (n=21, 43.8% with idiopathic PAH; male/female, 18/30; average age, 43.3±17.4 years; World Health Organization functional class III/IV, n=22, 45.8%) who were treated with ambrisentan and a PDE5 inhibitor in Japan underwent the safety analysis. A total of 14 ADR occurred in 10 patients (20.8%). ADR included headache (8.3%), face edema (4.2%), angina pectoris (2.1%), hyperemia (2.1%), dyspnea (2.1%), pulmonary hypertension (i.e., worsening of PAH, 2.1%), nausea (2.1%), hepatic function abnormal (2.1%), edema (2.1%), and sudden death (2.1%). On analysis of hemodynamics parameters, there was a significant improvement in the mean pulmonary arterial pressure (−13.5 mmHg, P=0.0001) and pulmonary vascular resistance (−563.53 dyn·s·cm⁻⁵, P=0.0033).

Conclusions: Ambrisentan combination therapy is safe and effective in hemodynamics improvement.

A prospective, open-label, non-comparative study of ambrisentan with anti-fibrotic agent combination therapy in the treatment of diffuse systemic sclerosis

Background

Systemic Sclerosis is a multifactorial autoimmune rheumatic disease characterized by inflammation, fibrosis, immune dysregulation and vascular dysfunction.

Methods

An open label, prospective, non-comparative study evaluating ambrisentan with an antifibrotic agent in diffuse cutaneous systemic sclerosis (dcSSc). Recruited 15 consecutive patients with dcSSc who were already on a stable dose of an antifibrotic agent and if they met inclusion criteria they were initiated on ambrisentan 5 mg/day for 12 months. Primary outcome measure was the modified Rodnan skin score (mRSS) while secondary measures were the short form 36 (SF-36) questionnaire, the Medsger severity score and pulmonary function studies.

Results

Fifteen patients were recruited and ten patients completed all 12 months of the study. An intention to treat was used to analyze the data. There was statistical improvement of the mean mRSS and the perceived change in health component of the SF-36. The Medsger severity score and pulmonary function studies remained unchanged over the course of the study.

Conclusion

Patients who tolerated the combination of an antifibrotic with ambrisentan had an improvement of their mRSS over the course of the study as well as an improvement of their perceived health.

Trial registration

Clinicaltrials.gov, NCT01093885; March 2010.

Enhancement of solubility and bioavailability of ambrisentan by solid dispersion using Daucus carota as a drug carrier: formulation, characterization, in vitro, and in vivo study

Ambrisentan is an US FDA approved drug, it is the second oral endothelin A receptor antagonist known for the treatment of pulmonary arterial hypertension, but its oral administration is limited due to its poor water solubility. Hence, the objective of the investigation was focused on enhancement of solubility and bioavailability of ambrisentan by solid dispersion technique using natural Daucus carota extract as drug carrier. Drug carrier was evaluated for solubility, swelling index, viscosity, angle of repose, hydration capacity, and acute toxicity test (LD₅₀). Ambrisentan was studied for the saturation solubility, phase solubility, and Gibbs free energy change. Compatibility of drug and the natural carrier was confirmed by DSC, FTIR, and XRD. Solid dispersions were evaluated for drug content, solubility, morphology, in vitro, and in vivo study. Screening of the natural carrier showed the desirable properties like water solubility, less swelling index, less viscosity, and acute toxicity study revealed no any clinical symptoms of toxicity. Drug and carrier interaction study confirmed the compatibility to consider its use in the formulation. Formed particles were found to be spherical with smooth surface. In vitro studies revealed higher drug release from the solid dispersion than that of the physical mixture. Bioavailability study confirms the increased absorption and bioavailability by oral administration of solid dispersion. Hence, it can be concluded that the natural Daucus carota extract can be the better alternative source for the preparation of solid dispersion and/or other dosage forms for improving solubility and bioavailability.

Combination targeted pulmonary hypertension therapy in the resolution of Dasatinib-associated pulmonary arterial hypertension

Dasatinib is a small-molecule tyrosine kinase inhibitor used in the treatment of hematological malignancies. Pulmonary arterial hypertension (PAH) is a rare but known complication. The mainstay of treatment is cessation of Dasatinib, and while clinical improvement is rapid, complete hemodynamic resolution of pulmonary hypertension (PH) still remains exceedingly uncommon. We present a case of Dasatinib-induced PAH in a woman with chronic myeloid leukemia, who demonstrated rapid and complete clinical and hemodynamic resolution following treatment with combination pulmonary vasodilator therapy using an endothelin receptor antagonist and a phosphodiesterase-5 inhibitor. This case suggests there may be an association between the use of targeted PH medication in combination and the complete resolution of dasatinib-associated PAH, but further investigation is required.

Functional estimation of endothelin-1 receptor antagonism by bosentan, macitentan and ambrisentan in human pulmonary and radial arteries in vitro

BACKGROUND

Endothelin receptor antagonists are approved for pulmonary arterial hypertension. Development of selective ET_A-receptor antagonists over mixed or dual receptor antagonists has depended on a range of receptor binding assays, second messenger assays and functional blood vessel assays. This study compared the 3 clinically-approved endothelin receptor antagonists in assays of human isolated pulmonary and radial arteries in vitro.

METHODS

Human isolated pulmonary (i.d. 5.5mm) and human radial (i.d. 3.23mm) artery ring segments were mounted in organ baths for isometric force measurement. Single concentration-contraction curves to endothelin-1 were constructed in the absence or presence of bosentan (1-10µM), macitentan (0.03-0.3µM) or ambrisentan (0.1-1µM).

RESULTS

All 3 endothelin antagonists caused competitive rightward shifts in the endothelin-1 concentration-response curves in both arteries. The Clark plot and analysis gave the following pK_B values: bosentan, pulmonary artery 6.28±0.13 and radial artery 6.04±0.10; macitentan, pulmonary artery 8.02±0.13 and radial artery 7.49±0.08; and ambrisentan, pulmonary artery 7.38±0.13 and radial artery 6.96±0.10.

CONCLUSIONS

Noting the maximum plasma levels attained from recommended oral doses of each antagonist in volunteers, the pK_B findings here show that there would be significant antagonism of endothelin-1 contraction in the pulmonary and radial arteries at therapeutic plasma levels. This functional assay confirms in human tissue that much higher plasma concentrations of endothelin-1 receptor antagonists are required to be effective than those predicted from binding or other biochemical assays.

Plasma Drug Concentrations in Patients with Pulmonary Arterial Hypertension on Combination Treatment

BACKGROUND

Combination therapy with the phosphodiesterase type 5 inhibitors (PDE-5i) sildenafil or tadalafil and the endothelin receptor antagonists (ERA) bosentan, ambrisentan, or macitentan may cause mutual pharmacokinetic interactions in patients with pulmonary arterial hypertension (PAH).

OBJECTIVE

The objective of this study was to analyze plasma drug concentrations in PAH patients receiving different combination treatments.

METHODS

PAH patients receiving a stable combination treatment with ERA and PDE-5i with targeted dosage for at least 1 month were routinely assessed, including clinical parameters and plasma drug concentrations. Concentrations were normalized considering dose and time from last medication intake and presented as multiples of the expected mean (MoM) of the respective monotherapies.

RESULTS

A total of 125 PAH patients (84 female, 41 male, 57% idiopathic/heritable) were included. Sildenafil and tadalafil concentrations were lowest in combination with bosentan (MoM 0.44 ± 0.42, 95% confidence interval [CI] 0.30-0.57, and MoM 0.89 ± 0.53, 95% CI 0.50-1.28, respectively) compared to the combination with ambrisentan (MoM 1.3 ± 0.97, 95% CI 0.86-1.73, and MoM 1.67 ± 0.63, 95% CI 1.40-1.94, respectively) and macitentan (MoM 1.16 ± 0.87, 95% CI 0.86-1.46, and MoM 1.59 ± 0.99, 95% CI 0.80-2.38, respectively). The combination of sildenafil and bosentan led to more than twice the expected bosentan concentrations in 53.8%. Patients switching from sildenafil-bosentan to macitentan showed a significant increase in sildenafil concentrations (p < 0.001).

CONCLUSIONS

Only the combination with macitentan or ambrisentan led to targeted mean PDE-5i plasma concentrations and should therefore be preferred to combination with bosentan. Sildenafil-bosentan showed the strongest interaction, with low sildenafil and high bosentan concentrations. The study was not powered to analyze whether lower PDE-5i concentrations cause unsatisfying clinical response. However, plasma concentrations within a targeted range are desirable and may become of increasing importance.

Clinical and hemodynamic improvements after adding ambrisentan to background PDE5i therapy in patients with pulmonary arterial hypertension exhibiting a suboptimal therapeutic response (ATHENA-1)

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a condition which may lead to right ventricular failure and premature death. While recent data supports the initial combination of ambrisentan (a selective ERA) and tadalafil (a PDE5i) in functional class II or III patients, there is no published data describing the safety and efficacy of ambrisentan when added to patients currently receiving a PDE5i and exhibiting a suboptimal response. The ATHENA-1 study describes the safety and efficacy of the addition of ambrisentan in this patient population.

METHODS

PAH patients with a suboptimal response to current PDE5i monotherapy were assigned ambrisentan in an open-label fashion and evaluated for up to 48 weeks. Cardiopulmonary hemodynamics (change in PVR as primary endpoint) were evaluated at week 24 and functional parameters and biomarkers were measured through week 48. Time to clinical worsening (TTCW) and survival are also described.

RESULTS

Thirty-three subjects were included in the analysis. At week 24, statistically significant improvements in PVR (-32%), mPAP (-11%), and CI (+25%) were observed. Hemodynamic improvements at week 24 were further supported by improvements in the secondary endpoints: 6-min walk distance (+18 m), NT-proBNP (-31%), and maintenance or improvement in WHO FC in 97% of patients. Adverse events were consistent with known effects of ambrisentan.

CONCLUSION

The hemodynamic, functional, and biomarker improvements observed in the ATHENA-1 study suggests that the sequential addition of ambrisentan to patients not having a satisfactory response to established PDE5i monotherapy is a reasonable option.

Evaluation of efficacy, safety and tolerability of Ambrisentan in Chinese adults with pulmonary arterial hypertension: a prospective open label cohort study

Background

Although several new drugs have been approved in recent years, pulmonary arterial hypertension (PAH) remains a rapidly progressive disease with a poor prognosis. Ambrisentan, a selective endothelin type A antagonist, has been approved for treatment of PAH. This open label study assessed the efficacy and safety of ambrisentan in Chinese subjects with PAH.

Methods

Eligible patients with PAH (World Health Organisation [WHO] functional class [FC] II orIII) were enrolled and received Ambrisentan (5 mg) once daily for a 12-week preliminary evaluation period, and a 12-week dose-adjustment period (dose titration to 10 mgallowed). Endpoints included: change from baseline in 6-Minute Walk Distance (6-MWD), N-Terminal Pro B-Type Natriuretic Peptide (NT-pro-BNP), WHO FC, Borg Dyspnoea Index (BDI), clinical worsening of PAH and incidences of adverse events (AE).

Results

One hundred thirty-three subjects (85 % women, mean age: 36 years) with PAH (WHOFC II or III) were enrolled and received ambrisentan (5 mg) once daily for a 12-week preliminary evaluation period, and a 12-week dose-adjustment period. Mean (SD) duration of drug exposure was 161.7 (27.13) days. Ambrisentan (average daily dose of 6.27 mg) significantly improved exercise capacity (6MWD) from baseline (mean: 377.1 m [m]) at week 12 (+53.6 m, p < 0.001) (primary endpoint). Improvement in exercise capacity was noted as early as week 4, and was sustained up to week 24 (+ 64.4 m, p < 0.001). NT-pro-BNP plasma levels decreased significantly (p < 0.001) at week 12 (−861.4 ng/L) and week 24 (−806 ng/L) from baseline (mean: 1600.7 ng/L). The WHO FC showed improvements for 44 subjects at week 12 and 51 subjects at week 24. BDI scores decreased significantly at week 12 (−0.3, p < 0.001) and week 24 (−0.2, p = 0.003) from baseline (mean: 2.5). Four patients died during the study (sudden cardiac death [n = 2], cerebral haemorrhage [n = 1], cardiac failure [n = 1]). Drug related adverse events occurred in 34.3 % of subjects; peripheral oedema (11.2 %) and flushing (8.2 %) occurred most frequently.

Conclusion

Ambrisentan (5 and 10 mg, orally) significantly improved the exercise capacity in Chinese PAH subjects with a safety profile similar to that observed in global studies.

Trial registration

NCT No. (ClinicalTrials.gov): NCT01808313; Registration date (first time): February 28, 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0361-9) contains supplementary material, which is available to authorized users.

Antifibrotic effects of ambrisentan, an endothelin-A receptor antagonist, in a non-alcoholic steatohepatitis mouse model

AIM: To examine the effects of the endothelin type A receptor antagonist ambrisentan on hepatic steatosis and fibrosis in a steatohepatitis mouse model.

METHODS: Fatty liver shionogi (FLS) FLS-ob/ob mice (male, 12 wk old) received ambrisentan (2.5 mg/kg orally per day; n = 8) or water as a control (n = 5) for 4 wk. Factors were compared between the two groups, including steatosis, fibrosis, inflammation, and endothelin-related gene expression in the liver.

RESULTS: In the ambrisentan group, hepatic hydroxyproline content was significantly lower than in the control group (18.0 μg/g ± 6.1 μg/g vs 33.9 μg/g ± 13.5 μg/g liver, respectively, P = 0.014). Hepatic fibrosis estimated by Sirius red staining and areas positive for α-smooth muscle actin, indicative of activated hepatic stellate cells, were also significantly lower in the ambrisentan group (0.46% ± 0.18% vs 1.11% ± 0.28%, respectively, P = 0.0003; and 0.12% ± 0.08% vs 0.25% ± 0.11%, respectively, P = 0.047). Moreover, hepatic RNA expression levels of procollagen-1 and tissue inhibitor of metalloproteinase-1 (TIMP-1) were significantly lower by 60% and 45%, respectively, in the ambrisentan group. Inflammation, steatosis, and endothelin-related mRNA expression in the liver were not significantly different between the groups.

CONCLUSION: Ambrisentan attenuated the progression of hepatic fibrosis by inhibiting hepatic stellate cell activation and reducing procollagen-1 and TIMP-1 gene expression. Ambrisentan did not affect inflammation or steatosis.

Enantioseparation and impurity determination of ambrisentan using cyclodextrin-modified micellar electrokinetic chromatography: Visualizing the design space within quality by design framework

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral drug ambrisentan has been developed following the Quality by Design principles. The selected separation system consisted of a micellar pseudostationary phase made by sodium dodecyl sulphate with the addition of γ-cyclodextrin. The effects of critical process parameters (capillary length, temperature, voltage, borate concentration, pH, sodium dodecyl sulphate concentration, γ-cyclodextrin concentration) on enantioresolution of ambrisentan and analysis time were extensively investigated by multivariate strategies involving a screening phase and Response Surface Methodology. The Design Space was defined with a desired probability level π≥90%, and the working conditions, with the limits of the Design Space, corresponded to the following: capillary length, 64.5cm; temperature, 22°C; voltage, 30kV (26-30kV); background electrolyte, 100mM borate buffer pH 9.20 (8.80-9.60), 100mM sodium dodecyl sulphate, 50mM (43-50mM) γ-cyclodextrin. A Plackett-Burman design was applied for robustness testing, and a method control strategy was established. The method was fully validated according to the International Conference on Harmonisation guidelines and was applied to ambrisentan coated tablets.

Ambrisentan response in connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) - A subgroup analysis of the ARIES-E clinical trial

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a condition which may lead to right ventricular failure and early mortality and is an important complication in patients with connective tissue disease (CTD). Previously, the endothelin A selective receptor antagonist, ambrisentan, demonstrated efficacy and safety in treating patients with PAH due to WHO Group I etiologies. These analyses describe the 3-year efficacy and safety of ambrisentan in patients specifically with CTD associated PAH (CTD-PAH).

METHODS

Patients with CTD-PAH participating in the ARIES-1 and -2 clinical trials and their long-term extension were evaluated. Efficacy evaluations including 6-min walk distance (6MWD), clinical worsening, and survival were collected at routine study visits. Additional analyses of 6MWD categorical (30 m) breakpoints were conducted to determine any relationship between 6MWD and a prognostic threshold for survival.

RESULTS

124 patients with CTD-PAH were evaluated. 62.6%, 57.3%, and 58.2% of CTD-PAH patients treated with ambrisentan exhibited increases in 6MWD at 1-, 2-, and 3- years respectively. At 3 years, 64% of patients were free from clinical worsening and 76% of patients were still alive (Kaplan-Meier estimates). Identified factors holding prognostic relevance for survival include: baseline functional class, CTD-PAH subgroup, patient sex, improvement in 6MWD ≥30 m over the first 12 weeks of treatment, the most recent 6MWD, and a 6MWD absolute threshold of 222 m.

CONCLUSION

These first analyses of the 3-year treatment of CTD-PAH patients with ambrisentan revealed fewer clinical worsening events and improved survival compared to historical controls. Key exercise parameters were also identified which appear important in guiding treatment.

[Pulmonary arterial hypertension associated with human immunodeficiency virus infection: study of 4 cases]

BACKGROUND AND OBJECTIVE

Pulmonary arterial hypertension (PAH) is a rare and progressive disease that can be inherited as autosomal dominant form. The BMPR2, ACVRL1 and ENG genes are main genes involved in the pathology. PAH associated to human immunodeficiency virus (HIV) is another rare disease with a low incidence, prevalence and survival. The main objective of this analysis was to study the clinical and molecular characteristics of PAH associated to HIV patients.

PATIENTS

We present 4 cases of HIV patients who developed PAH and have been treated with ambrisentan.

RESULTS

Pathogenic mutations have been identify in analyzed genes in 3 of the four analyzed patients. In addition, these patients present other changes classified as benign after a thorough in silico analysis. We identified some changes in genetic modifiers that predispose to these patients to more severe phenotype.

CONCLUSIONS

The clinical analysis can help to define monitoring for these patients and the administration of appropriate treatment. These patients also have shown several pathogenic mutations.

Endothelin receptors and their antagonists

All three members of the endothelin (ET) family of peptides, ET-1, ET-2, and ET-3, are expressed in the human kidney, with ET-1 being the predominant isoform. ET-1 and ET-2 bind to two G-protein–coupled receptors, ET_A and ET_B, whereas at physiological concentrations ET-3 has little affinity for the ET_A receptor. The human kidney is unusual among the peripheral organs in expressing a high density of ET_B. The renal vascular endothelium only expresses the ET_B subtype and ET-1 acts in an autocrine or paracrine manner to release vasodilators. Endothelial ET_B in kidney, as well as liver and lungs, also has a critical role in scavenging ET-1 from the plasma. The third major function is ET-1 activation of ET_B in in the nephron to reduce salt and water re-absorption. In contrast, ET_A predominate on smooth muscle, causing vasoconstriction and mediating many of the pathophysiological actions of ET-1. The role of the two receptors has been delineated using highly selective ET_A (BQ123, TAK-044) and ET_B (BQ788) peptide antagonists. Nonpeptide antagonists, bosentan, macitentan, and ambrisentan, that are either mixed ET_A/ET_B antagonists or display ET_A selectivity, have been approved for clinical use but to date are limited to pulmonary hypertension. Ambrisentan is in clinical trials in patients with type 2 diabetic nephropathy. This review summarizes ET-receptor antagonism in the human kidney, and considers the relative merits of selective versus nonselective antagonism in renal disease.

Ambrisentan for the treatment of adults with pulmonary arterial hypertension: a review

OBJECTIVE

To provide an overview of the drug profile of the orally active, selective endothelin A receptor antagonist ambrisentan, and its efficacy and safety in the treatment of patients with pulmonary arterial hypertension (PAH).

RESEARCH DESIGN AND METHODS

Medical literature on the use of ambrisentan in PAH was identified using MEDLINE and EMBASE. Additional references were identified from the reference lists of published articles and from the authors' own bibliographies.

RESULTS

Significant improvements in exercise capacity were observed with approved dosages of ambrisentan (5 or 10 mg once daily) in the AMB-220 dose-ranging study and the pivotal ARIES-1 and ARIES-2 trials, with sustained effects up to 2 years observed in ARIES-E. Improvements in cardiopulmonary hemodynamic variables were reported in AMB-220 and ARIES-E (subset analysis). Ambrisentan had little or no effect on hepatic transporters in in vitro studies and displayed a low risk of potential drug-drug interactions, including those with other PAH therapies. Results from the VOLT post-marketing program confirmed the safety profile of ambrisentan observed in the ARIES studies, including the low incidence of liver function test abnormalities. Peripheral edema and anemia were common side effects of endothelin receptor antagonist therapies, including ambrisentan. In the recently completed AMBITION study (ClinicalTrials.gov Identifier: NCT01178073), upfront initial combination therapy with ambrisentan and tadalafil significantly reduced the risk of clinical failure (primary endpoint) by 50% compared with the pooled monotherapy groups.

CONCLUSIONS

The long-term efficacy and safety profile of ambrisentan in patients with PAH is supported by data from a comprehensive clinical trial program and real-life, post-marketing observations.

Hemodynamic effects of ambrisentan-tadalafil combination therapy on progressive portopulmonary hypertension

Intravenous epoprostenol is recommended for World Health Organization functional class (WHO-FC) IV patients with pulmonary arterial hypertension (PAH) in the latest guidelines. However, in portopulmonary hypertension (PoPH) patients, advanced liver dysfunction and/or thrombocytopenia often makes the use of intravenous epoprostenol challenging. Here we report the cases of two WHO-FC IV PoPH patients who were successfully treated with a combination of two oral vasodilators used to treat PAH: ambrisentan and tadalafil. Oral vasodilator therapy using a combination of ambrisentan and tadalafil may be a safe and effective therapeutic option for WHO-FC IV PoPH patients and should be considered for selected patients with severe and rapidly progressing PoPH.

Stability-Indicating RP-HPLC Method for the Determination of Ambrisentan and Tadalafil in Pharmaceutical Dosage Form

A simple, rapid, and highly selective RP-HPLC method was developed for the simultaneous determination of Ambrisentan (AMB) and Tadalafil (TADA) drug substances in the fixed dosage strength of 10 mg and 40 mg, respectively. Effective chromatographic separation was achieved using a Hypersil GOLD C18 column (150 mm × 4.6 mm internal diameter, 5 μm particle size) with a mobile phase composed of methanol, water, and acetonitrile in the ratio of 40:40:20 (by volume). The mobile phase was pumped using a gradient HPLC system at a flow rate of 0.5 mL/min, and quantification of the analytes was based on measuring their peak areas at 260 nm. The retention times for Ambrisentan and Tadalafil were about 2.80 and 7.10 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. Calibration curves were linear in the ranges of 1-20 μg/mL for Ambrisentan and 4-80 μg/mL for Tadalafil with correlation coefficients >0.990. The proposed method proved to be selective and stability-indicating by the resolution of the two analytes from the forced degradation (hydrolysis, oxidation, and photolysis) products. The validated HPLC method was successfully applied to the analysis of AMB and TADA in pharmaceutical dosage form.

BMPR2 gene mutation in pulmonary arteriovenous malformation and pulmonary hypertension: a case report

The transforming growth factor-β superfamily signaling pathway is thought to be involved in the pathogenesis of pulmonary arteriovenous malformation (PAVM). However, the association between bone morphogenetic protein receptor type 2 (BMPR2) gene mutations and PAVM remains unclear. We present a case of concurrent PAVM and pulmonary arterial hypertension (PAH), with a deletion mutation in exon 6 and exon 7 of the BMPR2 gene. Drug treatment for PAH improved the patient's hemodynamics and exercise capacity, but worsened oxygenation. This case suggests that BMPR2 gene mutation may be associated with the complex presentation of PAVM combined with PAH.

Effect of ambrisentan on peripheral circulation in patients with systemic sclerosis

Systemic sclerosis (SSc) is characterized by disturbed blood circulation. The effect of ambrisentan, an endothelin-A receptor-selective antagonist, on impaired peripheral circulation in SSc remains largely elusive. Here we show SSc patients, whose clinical symptoms such as cyanosis and Raynaud's phenomenon, were ameliorated by the treatment with ambrisentan. Additionally, objective evaluations with thermography showed improvement of hand coldness in steady-state and cold challenge tests. Ambrisentan might have a potential to improve peripheral circulation in SSc.

Extractive spectrophotometric determination of ambrisentan

PURPOSE

Ambrisentan (ABS) is an antihypertensive drug used in the treatment of pulmonary atrial hypertension. The survey of literature for ABS revealed only two spectrophotometric methods for its quantification. The reported methods lack the sensitivity. This study is aimed at developing two sensitive extractive spectrophotometric methods for the determination of ABS in bulk and in tablets.

METHODS

The proposed methods are based on the formation of colored chloroform extractable ion-pair complexes of ABS with methylene blue (MB method) and safranine O (SO method) in buffered solution at pH 9.8. The extracted complexes showed maximum absorbance at 525 and 515 nm for methylene blue and safranine O, respectively.

RESULTS

In both the methods, the calibration curve was linear from 1-15 µg mL(-1) of drug. Apparent molar absorpitivities were 1.7911 x 10(5), 2.3272 x 10(5) L mol(-1) cm(-1); Sandell's sensitivities were 0.0215, 0.0162 µg cm(-2); LOD were 0.182, 0.175 µg mL(-1); LOQ were 0.551, 0.531 µg mL(-1) for methods MB and SO, respectively. The relative standard deviation and percent recovery ranged from 0.206-1.310% and 99.0-101.5%, respectively.

CONCLUSION

The results demonstrate that the proposed methods are sensitive, precise, accurate and inexpensive. These methods can easily be used for the assay of ABS in quality control laboratories.