Sitaxsentan,a selective endothelin-A receptor antagonist for the treatment of pulmonary arterial hypertension

Sitaxsentan, a highly selective endothelin-A (ET_A) receptor antagonist (6500-fold more selective for ET_A receptors than endothelin-B (ET_B) receptors), may benefit patients with pulmonary artery hypertension (PAH) by blocking the vasoconstrictor effects of ET_A receptors while maintaining the vasodilator/clearance functions of ET_B receptors. In its first randomised, placebo-controlled study, Sitaxsentan to Relieve Impaired Exercise-1 (STRIDE-1), sitaxsentan improved exercise capacity assessed by 6 min walk, New York Heart Association functional class, cardiac index and pulmonary vascular resistance in New York Heart Association class II, III and IV patients with idiopathic PAH, PAH related to connective tissue disease or PAH related to congenital heart disease. In STRIDE-1, doses of 100 and 300 mg/day p.o. were evaluated. Although both doses showed equivalent efficacy, the lower dose had a more tolerable safety profile. Additional studies are ongoing to assess the relative safety and efficacy of 50 and 100 mg/day doses, both in de novo patients and in patients previously treated with the ET_A/ET_B receptor antagonist bosentan. Long-term comparative studies are necessary to determine whether there is a clinically meaningful difference between selective ET_A receptor antagonism and ET_A/ET_B receptor antagonism.     

Physiologically based pharmacokinetic model of renally cleared antibacterial drugs in Chinese renal impairment patients

To preliminarily develop physiologically based population models for Chinese renal impairment patients and to evaluate the prediction performance of new population models by renally cleared antibacterial drugs. First, demographic data and physiological parameters of Chinese renal impairment patients were collected, and then the coefficients of the relative demographic and physiological equation were recalibrated to construct the new population models. Second, drug‐independent parameters of ceftazidime, cefodizime, vancomycin, and cefuroxime were collected and verified by Chinese healthy volunteers, Caucasian healthy volunteers, and Caucasian renal impairment population models built in Simcyp. Finally, the newly developed population models were applied to predict the plasma concentration of four antibacterial drugs in Chinese renal impairment patients. The new physiologically based pharmacokinetic (PBPK) population models can predict the main pharmacokinetic parameters, including area under the plasma concentration–time curve extrapolated to infinity (AUC_inf), renal clearance (CL_r), and peak concentration (C_max), of ceftazidime, cefodizime, vancomycin, and cefuroxime following intravenous administrations with less than twofold error in mild, moderate, and severe Chinese renal impairment patients. The accuracy and precision of the predictions were improved compared with the Chinese healthy volunteers and Caucasian renal impairment population models. The PBPK population models were preliminarily developed and the first‐step validation results of four antibacterial drugs following intravenous administration showed acceptable accuracy and precision. The population models still need more systematic validation by using more drugs and scenarios in future studies to support their applications on dosage recommendation for Chinese renal impairment patients.     

双重内皮素受体阻滞剂波生坦

波生坦是一种相对分子质量低的竞争性双重内皮素受体阻滞剂,通过与ETA和ETB的结合来阻止ET-1的作用.它能降低血管压力,阻止心脏和血管增生,减轻肺纤维化和炎症,用于治疗WHO功能组Ⅲ和Ⅳ型肺动脉高压.现综述波生坦的药理学、药动学和临床应用方面的进展.     

Application of a physiologically based pharmacokinetic model for the prediction of mirabegron plasma concentrations in a population with severe renal impairment

We previously verified a physiologically based pharmacokinetic (PBPK) model for mirabegron in healthy subjects using the Simcyp Simulator by incorporating data on the inhibitory effect on cytochrome P450 (CYP) 2D6 and a multi‐elimination pathway mediated by CYP3A4, uridine 5′‐diphosphate‐glucuronosyltransferase (UGT) 2B7 and butyrylcholinesterase (BChE). The aim of this study was to use this PBPK model to assess the magnitude of drug–drug interactions (DDIs) in an elderly population with severe renal impairment (sRI), which has not been evaluated in clinical trials. We first determined the system parameters, and meta‐analyses of literature data suggested that the abundance of UGT2B7 and the BChE activity in an elderly population with sRI was almost equivalent to and 20% lower than that in healthy young subjects, respectively. Other parameters, such as the CYP3A4 abundance, for an sRI population were used according to those built into the Simcyp Simulator. Second, we confirmed that the PBPK model reproduced the plasma concentration–time profile for mirabegron in an sRI population (simulated area under the plasma concentration–time curve (AUC) was within 1.5‐times that of the observed value). Finally, we applied the PBPK model to simulate DDIs in an sRI population. The PBPK model predicted that the AUC for mirabegron with itraconazole (a CYP3A4 inhibitor) was 4.12‐times that in healthy elderly subjects administered mirabegron alone, and predicted that the proportional change in AUC for desipramine (a CYP2D6 substrate) with mirabegron was greater than that in healthy subjects. In conclusion, the PBPK model was verified for the purpose of DDI assessment in an elderly population with sRI.     

Vasodilator effects of the endothelin ET receptor selective antagonist BMS-193884 in healthy men

AIMS: A number of endothelin receptor antagonists (ERAs) are currently in clinical development as potential therapies in states characterized by vasoconstriction, such as systemic hypertension. We investigated the haemodynamic effects of locally and systemically active doses of BMS-193884, an endothelin A (ET(A)) receptor selective ERA, and its influence on vasoconstriction to endothelin-1 (ET-1) in healthy men. METHODS: In three separate randomized, placebo-controlled studies, the forearm blood flow (FBF) response to intra-arterial (i.a.) infusion of ET-1 (5 pmol min(-1)) was assessed during i.a. co-infusion of BMS-193884 (5 and 50 nmol min(-1)), and at 12 and at 24 h after oral administration of BMS-193884 (50, 100 and 200 mg at 12 h; and 200 mg at 24 h). Data were examined by repeated-measures analysis of variance (anova) with treatment and subject as factors. RESULTS: ET-1 caused significant forearm vasoconstriction, attenuated after oral dosing with BMS-193884 (200 mg) at 12 (P < 0.01) and 24 h (P < 0.0001). BMS-193884 (50 nmol min(-1), i.a.) caused local vasodilatation (25 +/- 11%) when infused alone (P = 0.02) and abolished forearm vasoconstriction to ET-1 (P < 0.0001 vs. ET-1 alone). Orally, BMS-193884 (200 mg) caused a reduction in total systemic vascular resistance at 12 (-14 +/- 9%, P = 0.03) and 24 h (-12 +/- 7%, P < 0.0001). There was no rise in plasma ET-1 levels. CONCLUSION: BMS-193884 causes local and systemic vasodilatation and attenuation of local vasoconstriction to ET-1. The absence of a rise in plasma endothelin levels suggests BMS-193884 is selective for the ET(A) receptor. This form of pharmacodynamic modelling may be useful in the development of ERAs in cardiovascular disease.     

内皮素受体拮抗剂在心力衰竭治疗中的应用

内皮素是一种重要的心血管活性物质。内皮素在心力衰竭的发生发展中发挥重要作用。内皮素受体拮抗剂通过阻止内皮素和其受体的结合从而抑制结合后产生的效应，不仅有利于缓解心力衰竭病人的症状，而且可延迟心力衰竭病理过程的进展，是治疗心力衰竭的一种新的途径。     

Investigation of mutual pharmacokinetic interactions between macitentan,a novel endothelin receptor antagonist,and sildenafil in healthy subjects

AimTo study the mutual pharmacokinetic interactions between macitentan, an endothelin receptor antagonist, and sildenafil in healthy male subjects.MethodsIn this open-label, randomized, three way crossover study, 12 healthy male subjects received the following oral treatments: A) a loading dose of 30 mg macitentan on day 1 followed by 10 mg once daily for 3 days, B) sildenafil 20 mg three times a day for 3 days and a single 20 mg dose on day 4 and C) both treatments A and B concomitantly. Plasma concentration−time profiles of macitentan and its active metabolite ACT-132577 (treatments A and C) and sildenafil and its N-desmethyl metabolite (treatments B and C) were determined on day 4 and analyzed non-compartmentally.ResultsThe pharmacokinetics of macitentan were not affected by sildenafil. In the presence of sildenafil C_max and AUC_τ of the metabolite ACT-132577 decreased with geometric mean ratios (90% confidence interval (CI)) of 0.82 (0.76, 0.89) and 0.85 (90% CI 0.80, 0.91), respectively. In the presence of macitentan, plasma concentrations of sildenafil were higher than during treatment with sildenafil alone, resulting in increased C_max and AUC_τ values. The respective geometric mean ratios were 1.26 (90% CI 1.07, 1.48) and 1.15 (90% CI 0.94, 1.41). The pharmacokinetics of N-desmethylsildenafil were not affected by macitentan. All treatments were well tolerated.ConclusionA minor, not clinically relevant, pharmacokinetic interaction was observed between macitentan and sildenafil. Based on these results, no dose adjustment of either compound appears necessary during concomitant treatment with macitentan and sildenafil.     

A pharmacokinetic study of prazosin in patients with varying degrees of chronic renal failure

Summary Pharmacokinetic parameters of prazosin (t_1/2, t_max, C_max and AUC have been studied in 18 hypertensive patients with varying degrees of chronic renal failure (serum creatinine ranging from 1.6 to 11.4 mg/dl). An oral dose of 2 mg of prazosin was added to the preexisting antihypertensive medication. The degree of renal impairment did not influence the peak drug concentration, the time to peak or the serum half-life. On the other hand, the hypotensive action after 2 mg prazosin, was more pronounced in patients with severe chronic renal failure. This effect could not be explained by a difference in the pharmacokinetics of prazosin in severe as compared to moderate chronic renal failure or to normal renal function.     

Physiologically based pharmacokinetic modelling to predict exposure differences in healthy volunteers and subjects with renal impairment: Ceftazidime case study

Ceftazidime is a widely used β‐lactam antibiotic and almost entirely excreted via glomerular filtration in kidney. The objective of this analysis was to assess the ability of physiologically based pharmacokinetic (PBPK) model to predict ceftazidime exposure in healthy volunteers and subjects with renal impairment. A full PBPK model of ceftazidime was developed using physiochemical properties and clinical data. The total clearance of 115 mL/min and renal clearance of 100 mL/min were obtained from ceftazidime package insert. Healthy and chronic kidney disease (CKD) populations were applied for sampling of virtual subjects. The established PBPK model predicted mean plasma AUC_inf were 138.5 ± 19.6, 230.7 ± 22.2, 369.3 ± 53.1 and 561.8 ± 92.4 h   µg/mL in healthy, mild, moderate and severe renal impairment subjects, respectively, after administration of 1 g ceftazidime intravenous bolus dose. The predicted values were in close agreement with the weighted mean of the five reported clinical studies. The exposure was slightly under predicted in subjects with severely impaired renal function, but still within 1.5‐fold range. The concentration‐time profiles of ceftazidime were also well captured in healthy volunteers and subjects with renal impairment. The developed PBPK model along with systems pharmacokinetics (PK) (renal impaired populations) well predicted the ceftazidime exposure. PBPK models verified with clinical study in healthy volunteers could be potentially applied to predict PK and recommend dose adjustment for CKD patients.     

Effect of clazosentan, a selective endothelin A receptor antagonist, and tezosentan, a dual endothelin A/B antagonist, on pulsatile shear stress induced constriction of the iliac in the anaesthetized pig

1. The effects of changes in mean and pulsatile shear stress on the diameter of the iliac of the anaesthetized pig were investigated in the presence of clazosentan and tezosentan. 2. A total of 17 pigs were used. Mean shear stress was increased by infusing acetylcholine downstream (2-20 μg/min) through the deep femoral artery. Pulsatile shear stress was enhanced first by injecting varying volumes (1-10 mL) of calcium gluconate (stock 10 mg/mL) directly into the left ventricle. Second, by electrical stimulation of the left sympathetic nerves to the heart (1-16 Hz, 4 min duration, supramaximal voltage). 3. An increase in mean shear stress induced a vasodilation that was not altered significantly by the selective endothelin A antagonist clazosentan (10 mg/kg i.v.). Similarly, the vasoconstriction induced by an increase in pulsatile shear stress brought about by either calcium gluconate injections or left sympathetic nerve stimulation was unaffected by clazosentan. However, tezosentan (10 mg/kg i.v.), significantly attenuated the vasoconstriction induced by an increase in pulsatile shear stress. 4. In conclusion, an increase in pulsatile shear stress causes vasoconstriction of the pig iliac artery, which is attenuated by dual endothelin receptor antagonism, but not by specific endothelin A blockade.     

Pharmacokinetics of SB-247083, a potent and selective endothelin(A) receptor antagonist,in the rat,dog, and monkey

The endothelins (ET) are among the most potent vasoconstrictors identified to date, and have been implicated in such diseases as renal failure, pulmonary hypertension, atherosclerosis, and congestive heart failure. There is currently interest in developing selective antagonists of the ET-A subtype receptor, and one such antagonist is SB-247083 ((E)-[1-butyl-5-[2-(2-carboxyphenyl) methoxy-4-chlorophenyl]-1H-pyrazole-4-yl]-2-[5-methoxydihydrobenzofuran-6-yl]methyl]-2-propionic acid). This investigation was conducted to evaluate the preclinical pharmacokinetics of SB-247083. Clearance of SB-247083 was low to moderate in the rat and monkey, and high in the dog. Oral bioavailability of SB-247083 administered as a solid formulation of the free acid was 24% in the rat, but low in the dog (4%) and the monkey (2%). An extensive in vitro salt form and formulation screen resulted in the identification of a formulation containing the monoarginyl salt with improved dissolution properties. This formulation provided a 2- to 4-fold increase in oral bioavailability in each of the preclinical species. In the dog, this improvement was reversed by the pre-administration of 0.1 N HCl to normalize the achlorhydric fasting dog stomach. These data show that SB-247083 may have suitable drug properties for progression in development.     

Ambrisentan,an endothelin receptor type A-selective endothelin receptor antagonist,for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a disease of the pulmonary vasculature characterized by vasoconstriction and vascular proliferation, which leads to right heart failure and death. Prostacyclin, NO and endothelin are felt to be key mediators in the development of PAH. We present the available published and presented data about ambrisentan, an ET_A-selective endothelin receptor antagonist (ERA) and newest ERA agent to be approved by the FDA for the treatment of PAH in patients with WHO functional class II and III symptoms. Randomized, placebo-controlled trials have demonstrated a significant improvement in exercise capacity and decrease in time to clinical worsening, along with evidence to support an improvement in WHO functional class and quality of life for patients receiving ambrisentan. Long-term data have shown a 1-year survival of 95%; of the survivors, 94% remained on ambrisentan monotherapy. Endothelin receptor antagonists as a drug class have previously been associated with peripheral edema, aminotransferases abnormalities and a teratogenic risk to a developing fetus. Peripheral edema was observed in patients receiving ambrisentan; however, a greater percentage was experienced in patients aged > 65 years. In contrast, significant aminotransferase abnormalities were not observed with ambrisentan treatment in the placebo-controlled trials, and in all clinical trials combined the 1-year risk seems to be low (< 3%). Despite these data, the FDA requires monthly liver function tests monitoring. As with other ERAs, monthly pregnancy testing is required in all women of child bearing potential.     

The peptide endothelin receptor antagonist, TAK-044, produces sustained inhibition of endothelin-1 mediated arteriolar vasoconstriction

Aims Endothelin-1 (ET-1) has been implicated in the pathophysiology of a number of cardiovascular diseases for which endothelin receptor antagonists are currently under clinical development. We have previously reported that systemic administration of the combined endothelin A/B receptor antagonist, TAK-044, abolishes the forearm vasoconstriction caused by intrabrachial ET-1 infusion for at least 3 h. In this study we investigated whether TAK-044 can inhibit ET-1 mediated forearm vasoconstriction for longer periods. Methods Eighteen subjects were recruited to a randomized, placebo-controlled, single-blind, three-way, crossover study. Subjects were divided into three groups of six. Groups received 25 mg, 50 mg or 100 mg TAK-044 on two separate occasions, 6 and 10 h before the start of a 2 h intrabrachial infusion of ET-1 (5 pmol min⁻¹ ). On a third occasion subjects received only placebo before intra-arterial ET-1 infusion. Forearm vasoconstriction to ET-1 was measured by venous occlusion plethysmography. Results In the placebo phase, ET-1 caused significant, slowly-progressive local forearm vasoconstriction of ∼30% (P<0.01) in all three groups. All three doses of TAK-044, administered at both timepoints, tended to blunt the vasoconstriction caused by ET-1. When the responses from all three groups were combined, TAK-044 significantly reduced ET-1 mediated vasoconstriction compared with placebo −9% (95% CI −15 to −3; P=0.01) at 8 h and by −9% (95% CI −17 to −2; P=0.01) 12 h after dosing. Conclusions TAK-044 attenuated, but did not abolish, local ET-1 mediated vasoconstriction, for up to 12 h after administration. Vasoconstriction to local intra-arterial administration of ET-1 appears to represent a safe and reproducible pharmacodynamic index of systemic endothelin receptor antagonism in humans.     

选择性内皮素A型受体拮抗剂GF063对内皮素-1诱导的心肌细胞肥大的影响

目的探讨选择性内皮素A型(ETA)受体拮抗剂GF063对内皮素-1(ET-1)诱导的心肌细胞肥大的影响。方法利用差速贴壁法分离得到原代SD乳大鼠心肌细胞,心肌细胞用ET-1或ET-1+GF063处理24h,以BQ123为阳性对照,分别采用MTT比色法检测细胞存活、显微镜观察心肌细胞形态并计算细胞表面积、[3H]亮氨酸掺入法测定心肌细胞蛋白质合成速率、RT-PCR法检测心肌细胞心钠素(ANP)mRNA表达。结果与正常对照组比较,ET-1 10 nmo.lL-1作用24 h后,心肌细胞表面积明显增大80.6%,[3H]亮氨酸掺入明显增多73%,ANP mRNA表达量明显增加80%(P<0.05)。单独给予GF063 1 nmo.lL-1~10μmo.lL-1对心肌细胞存活率,细胞表面积,心肌细胞蛋白合成和ANPmRNA表达均无明显影响。但GF063 1μmo.lL-1可以显著抑制ET-1诱导的心肌细胞表面积增大(P<0.05),GF063 0.1和1μmol.L-1可显著降低心肌细胞蛋白合成(P<0.05),GF063 10μmol.L-1抑制ANP mRNA表达升高(P<0.05),作用强度与阳性对照药BQ123相当。结论 GF063能够抑制ET-1诱导的心肌细胞肥大作用。     

Influence of different degrees of liver impairment on the pharmacokinetics of clazosentan

AIM

To investigate the effect of mild, moderate and severe liver impairment on the pharmacokinetics (PK), tolerability and safety of clazosentan, an intravenous endothelin receptor antagonist.

METHODS

Healthy subjects with normal liver function (n = 8), subjects with mild (Child Pugh A, n = 8), and with moderate (Child-Pugh B, n = 8) liver impairment received a continuous intravenous infusion of 1 mg h⁻¹ and subjects with severe liver impairment (Child Pugh C, n = 8) received a continuous intravenous infusion of 0.5 mg h⁻¹ clazosentan for a duration of 6 h. The pharmacokinetic (PK) parameters of clazosentan were determined by both model-independent and model-dependent methods.

RESULTS

Mean plasma concentrations of clazosentan increased with increasing severity of liver impairment. Geometric means of area under the plasma concentration–time curve from 0 to infinity (AUC_(0,∞)) were 1.41- (90% CI 1.04, 1.90), 2.37- (90% CI 1.75, 3.19), and 3.79- (90% CI 2.81, 5.11) fold higher in subjects with mild, moderate and severe liver impairment, respectively, compared with healthy subjects. Similar results were obtained by non-compartmental and two-compartmental analysis. A significant positive correlation between clazosentan AUC_(0,∞) and Child-Pugh score (r = 0.83), bilirubin (r = 0.78) and prothrombin time (r = 0.62), and a significant negative correlation with albumin concentrationl (r = 0.71) was observed. Administration of clazosentan was well tolerated in all groups.

CONCLUSIONS

The increase in exposure to clazosentan in Child-Pugh A patients is not expected to be clinically relevant and no dose adjustment for these patients is proposed. It is recommended to reduce the dose of clazosentan to half in Child-Pugh B and to one fourth in Child-Pugh C patients.     

The renoprotective potential of endothelin receptor antagonists

The endothelin system has been identified as having a substantial role in renal failure, both acute and chronic. Beside its well characterised haemodynamic effects, its mitogenic and pro-fibrotic properties have gained increased interest in the pathophysiology of chronic renal failure. This review outlines the role of endothelin in the pathogenesis of various renal diseases with a special focus on the potential of blocking this system with endothelin receptor antagonists. So far, most data were derived from animal models, but they provide strong evidence that endothelin receptor antagonists may represent a powerful therapeutic strategy in ameliorating the course of acute and chronic renal failure.     

Pharmacokinetics of atenolol in patients with renal impairment

Summary The pharmacokinetics of atenolol, a new cardioselective -adrenoceptor blocking agent, were determined following both acute and chronic dosing in 33 hypertensive patients with widely differing levels of renal impairment. In patients with normal renal function the atenolol half-life was calculated to be about six hours following single 100 mg oral doses. This value increased markedly in patients with renal insufficiency and the blood clearance of atenolol was found to have a significant correlation with the glomerular filtration rate. This demonstrated the importance of the kidneys in the elimination of the drug. After 8 weeks oral treatment with atenolol (100 mg twice daily) a significant decrease in blood pressure, heart rate and plasma renin activity was observed, but no correlation was established between the blood levels of atenolol and any of its pharmacodynamic effects. A positive correlation was found however between the anti-hypertensive action of atenolol and the pretreatment value of the plasma renin activity.     

Meloxicam pharmacokinetics in renal impairment

Aims The aim of the present study was to determine how the pharmacokinetics of meloxicam are affected by kidney dysfunction and consequently to define the appropriate dose for the use of meloxicam in patients with mild or moderate renal impairment.
Methods Meloxicam was administered to subjects with mild (creatinine clearance 41–60 ml min⁻¹) to moderate (20–40 ml min⁻¹) renal impairment compared with normal renal function (>60 ml min⁻¹). Thirty-eight subjects received meloxicam 15 mg once daily over 9 days. Meloxicam plasma concentrations were determined from blood samples taken during the study and pharmacokinetic parameters calculated according to noncompartmental methods.
Results Subjects with no or mild renal impairment showed sinular pharmacokinetic profiles (geometric mean AUC_SS (%gCV) 55 (33%) vs 55 (38%) μg ml⁻¹ h). Subjects with moderate renal impairment demonstrated lower total plasma meloxicam concentrations (AUC_SS 35 (50%) μg ml ⁻¹ h, with corresponding higher plasma clearance ( P = 0.013) compared with subjects with no renal impairment. However, this was combined with higher meloxicam free fractions in moderately impaired subjects such that free meloxicam concentrations were similar in all three groups. Meloxicam was well tolerated with few adverse events occurring and no difference in incidence observable between groups.
Conclusions On the basis of these results there is no necessity for a dosage adjustment when administering meloxicam to patients with mild to moderate renal impairment.     

An experimental model for pharmacokinetic analysis in renal failure

A renal failure model was developed in the dog to evaluate the effect of varying degrees of renal failure on drug pharmacokinetics. A controlled impairment of renal function was induced by electrocoagulating portions of one kidney and excising the contralateral kidney. The magnitude of renal dysfunction, defined by the percentage of normal glomerular filtration rate (% NGFR), was estimated by ¹²⁵ I-iothalamate total body clearance. The model was evaluated by comparing the pharmacokinetics of oxytetracycline (OTC) before and after the induction of renal failure in two experiments: single intraveneous dose (11dogs); single intravenous and oral doses (8dogs). Renal failure (RF) was studied in three classes according to % NGFR: <25%,severe RF; 25–39%,moderate RF; and 40%,mild RF. Significant reductions were observed over RF class in OTC pharmacokinetic parameters for elimination and distribution but not for oral absorption.     

选择性内皮素受体阻滞剂darusentan的合成

目的:合成ETA选择性内皮素受体阻滞剂darusentan,降低合成的成本和操作难度.方法:以二苯甲酮为原料,经与氯乙酸乙酯在无溶剂的条件下进行Darzens缩合;对甲苯磺酸的催化下醇解;甲基亚硫酸钠的催化下与2-氯4,6-二甲氧基嘧啶进行亲核取代反应;碱性条件下水解得到目标化合物.结果:目标化合物经红外光谱、核磁共振氢谱、质谱确证其化学结构.结论:该法操作简便,成本低,总收率达53.5%.