ETA (IC50 = 3.4 nM); ETA (pA2 = 6.7); ETB (IC50 = 987 nM); ETB (pA2 = 5.5)

When applied to nonrecombinant cells (main human pulmonary smooth muscle cells, rat aortic smooth muscle cell line A10, and mouse fibroblast cell line 3T3), aproticentan (ACT-132577) completely inhibits the intracellular calcium rise caused by ET-1[1].

In rats, aprobicitentan (ACT-132577) has a longer half-life than its parent chemical and a volume of distribution larger than the plasma volume[1]. The range of Aprocitentan (ACT-132577) mean recovery in rat plasma is 82.6 % to 90.6%, while the range of Aprocitentan (ACT-132577) matrix effect in rat plasma is 101.4% to 115.2%[2].

Macitentan, also called Actelion-1 or ACT-064992 [N-[5-(4-bromophenyl)-6-(2-(5-bromopyrimidin-2-yloxy)ethoxy)-pyrimidin-4-yl]-N'-propylaminosulfonamide], is a new dual ET(A)/ET(B) endothelin (ET) receptor antagonist designed for tissue targeting. Selection of macitentan was based on inhibitory potency on both ET receptors and optimization of physicochemical properties to achieve high affinity for lipophilic milieu. In vivo, macitentan is metabolized into a major and pharmacologically active metabolite, ACT-132577. Macitentan and its metabolite antagonized the specific binding of ET-1 on membranes of cells overexpressing ET(A) and ET(B) receptors and blunted ET-1-induced calcium mobilization in various natural cell lines, with inhibitory constants within the nanomolar range. In functional assays, macitentan and ACT-132577 inhibited ET-1-induced contractions in isolated endothelium-denuded rat aorta (ET(A) receptors) and sarafotoxin S6c-induced contractions in isolated rat trachea (ET(B) receptors). In rats with pulmonary hypertension, macitentan prevented both the increase of pulmonary pressure and the right ventricle hypertrophy, and it markedly improved survival. In diabetic rats, chronic administration of macitentan decreased blood pressure and proteinuria and prevented end-organ damage (renal vascular hypertrophy and structural injury). In conclusion, macitentan, by its tissue-targeting properties and dual antagonism of ET receptors, protects against end-organ damage in diabetes and improves survival in pulmonary hypertensive rats. This profile makes macitentan a new agent to treat cardiovascular disorders associated with chronic tissue ET system activation.[1]

Calibration standards and quality control samples[2]
The stock solutions of ACT-132577 (1.0 mg/mL) and diazepam (IS) (100 µg/mL) were prepared in methanol-water (50:50, v/v). The 0.25 µg/mL working standard solution of the IS was prepared from the IS stock solution by dilution with methanol; working solutions for calibration and controls were prepared from stock solutions in the same manner. All of the solutions were stored at 4°C and were brought to room temperature before use.

ACT-132577 calibration standards were prepared by spiking blank rat plasma with appropriate amounts of the working solutions. Calibration plots were offset to range between 10-4000 ng/mL for ACT-132577 in rat plasma (10, 20, 50, 100, 200, 500, 1000, 2000 and 4000 ng/mL). Quality-control (QC) samples were prepared in the same manner as the calibration standards, in three different plasma concentrations (20, 1800, and 3600 ng/mL). The analytical standards and QC samples were stored at -20°C.

The selectivity of the method was evaluated by analyzing blank rat plasma, blank plasma-spiked ACT-132577 and IS, and a rat plasma sample.

Calibration curves were constructed by analyzing spiked calibration samples on three separate days. Peak area ratios of ACT-132577-to-IS were plotted against analyte concentrations. Resultant standard curves were well fitted to the equations by linear regression, with a weighting factor of the reciprocal of the concentration (1/x) in the concentration range of 10-4000 ng/mL. The lower Limit of quantitation (LLOQ) was defined as the lowest concentration on the calibration curves.

Stability of ACT-132577 in rat plasma were evaluated by analyzing three replicates of plasma samples at concentrations of 20 or 3600 ng/mL which were all exposed to different conditions. These results were compared with the freshly-prepared plasma samples. Short-term stability was determined after the exposure of the spiked samples to room temperature for 2 h, and the ready-to-inject samples (after protein precipitation) in the HPLC autosampler at room temperature for 24 h. Freeze/thaw stability was evaluated after three complete freeze/thaw cycles (-20 to 25°C) on consecutive days. Long-term stability was assessed after storage of the standard spiked plasma samples at -20°C for 20 days. The stability of the IS (50 ng/mL) was evaluated similarly

Pharmacokinetic study[2]
Twelve Male Sprague-Dawley rats (200-220 g) were used. The ethical number of the experiment animals was wydw2013-0071. All experimental procedures and protocols were reviewed and approved by the Animal Care and Use Committee of Wenzhou Medical University. Diet was prohibited for 12 h before the experiment but water was freely available. Blood samples (0.2 mL) were collected from the caudal vein into heparinized 1.5 mL tapered plastic centrifuge tubes at 0.0333, 0.15, 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 h after oral (15 mg/kg, n=6) and intravenous (5 mg/kg, n=6) administration of macitentan, respectively. The caudal vein of rat was cleaned by 75% alcohol, after that the end of caudal vein was cut by scissors. A 1.5 mL tapered plastic centrifuge tube was used to collect the blood which dropped from the end of caudal vein by squeezing and massaging gently. The samples were immediately centrifuged at 3000 × g for 10 min. The plasma as-obtained (50 µL) was stored at -20°C until UPLC-MS/MS analysis. Plasma ACT-132577 concentration versus time data for each rat was analyzed by DAS (Drug and Statistics) software.

Aprocitentan was well tolerated across all doses. No serious adverse events (AEs) occurred. The most frequently reported AE was headache. Small increases in body weight were recorded in subjects receiving 100 mg qd. Plasma concentration–time profiles of aprocitentan were similar after single- and multiple-dose administration, and support a qd dosing regimen based on a half-life of 44 hours. After multiple doses, PK was dose proportional. Accumulation at steady state, reached by Day 8, was 3-fold. Only minor differences in exposure between healthy females and males, healthy elderly and adult subjects, and fed and fasted conditions were observed. Plasma ET-1 concentrations, reflecting ETB receptor antagonism, significantly increased with doses ≥25 mg. Time-matched analysis of electrocardiogram (ECG) parameters did not suggest drug-induced ECG effects. Exposure–response analysis indicated no QTc prolongations at plasma levels up to 10 µg/mL.Drug Des Devel Ther. 2019; 13: 949–964.

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
No information is available on the clinical use of aprocitentan during breastfeeding. Because aprocitentan is more than 99% bound to plasma proteins, the amount in milk is likely to be low. However, its half-life is 41 hours and it might accumulate in the infant. Because no information is available on the use of aprocitentan during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

[1]. Pharmacology of macitentan, an orally active tissue-targeting dual endothelin receptor antagonist. J Pharmacol Exp Ther. 2008 Dec;327(3):736-45.

[2]. Pharmacokinetic study of ACT-132577 in rat plasma by ultra performance liquid chromatography-tandem mass spectrometry. Int J Clin Exp Med. 2015 Oct 15;8(10):18420-6.

ACT-132577 is a member of the class of sulfamides in which one of the amino groups of sulfonamide is substituted by a 5-(4-bromophenyl)-6-{2-[(5-bromopyrimidin-2-yl)oxy]ethoxy}pyrimidin-4-yl group. An active metabolite of macitentan (obtained by oxidative depropylation), an orphan drug used for the treatment of pulmonary arterial hypertension. It has a role as an antihypertensive agent, an endothelin receptor antagonist, a drug metabolite and a xenobiotic metabolite. It is an aromatic ether, an organobromine compound, a member of pyrimidines and a member of sulfamides. It is functionally related to an ethylene glycol.
Aprocitentan is under investigation in clinical trial NCT03541174 (A Research Study to Show the Effect of Aprocitentan in the Treatment of Difficult to Control (Resistant) High Blood Pressure (Hypertension) and Find Out More About Its Safety).

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Drug Indication
Treatment of hypertension.

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Macitentan, also called Actelion-1 or ACT-064992 [N-[5-(4-bromophenyl)-6-(2-(5-bromopyrimidin-2-yloxy)ethoxy)-pyrimidin-4-yl]-N'-propylaminosulfonamide], is a new dual ET(A)/ET(B) endothelin (ET) receptor antagonist designed for tissue targeting. Selection of macitentan was based on inhibitory potency on both ET receptors and optimization of physicochemical properties to achieve high affinity for lipophilic milieu. In vivo, macitentan is metabolized into a major and pharmacologically active metabolite, ACT-132577. Macitentan and its metabolite antagonized the specific binding of ET-1 on membranes of cells overexpressing ET(A) and ET(B) receptors and blunted ET-1-induced calcium mobilization in various natural cell lines, with inhibitory constants within the nanomolar range. In functional assays, macitentan and ACT-132577 inhibited ET-1-induced contractions in isolated endothelium-denuded rat aorta (ET(A) receptors) and sarafotoxin S6c-induced contractions in isolated rat trachea (ET(B) receptors). In rats with pulmonary hypertension, macitentan prevented both the increase of pulmonary pressure and the right ventricle hypertrophy, and it markedly improved survival. In diabetic rats, chronic administration of macitentan decreased blood pressure and proteinuria and prevented end-organ damage (renal vascular hypertrophy and structural injury). In conclusion, macitentan, by its tissue-targeting properties and dual antagonism of ET receptors, protects against end-organ damage in diabetes and improves survival in pulmonary hypertensive rats. This profile makes macitentan a new agent to treat cardiovascular disorders associated with chronic tissue ET system activation.[1]

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It was reported that macitentan was metabolized predominantly by cytochrome P450 3A4, and ACT-132577, its pharmacologically active metabolite, is fivefold less potent at blocking ET receptors than macitentan. In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of ACT-132577 in rat plasma was developed and validated. After addition of diazepam as an internal standard (IS), protein precipitation by acetonitrile was used to prepare samples. Chromatographic separation was achieved on a UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 μm) with 0.2% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 546.9→200.6 for ACT-132577, and m/z 285.1→193.1 for IS. Calibration plots were linear throughout the range 10-4000 ng/mL for ACT-132577 in rat plasma. Mean recovery of ACT-132577 in rat plasma ranged from 82.6% to 90.6%, matrix effect of ACT-132577 in rat plasma ranged from 101.4% to 115.2%. RSD of intra-day and inter-day precision were both less than 11%. The accuracy of the method ranged from 96.1% to 103.5%. The method was successfully applied to pharmacokinetic study of ACT-132577 after oral and intravenous administration of macitentan. [2]

C₁₆H₁₀D₄BR₂N₆O₄S

546.194

543.916

C, 35.18; H, 2.58; Br, 29.26; N, 15.39; O, 11.72; S, 5.87

1103522-45-7

Aprocitentan-d4

25099191

White to off-white solid powder

4.385

2

10

8

29

597

0

C1=CC(=CC=C1C2=C(N=CN=C2OCCOC3=NC=C(C=N3)Br)NS(=O)(=O)N)Br

DKULOVKANLVDEA-UHFFFAOYSA-N

InChI=1S/C16H14Br2N6O4S/c17-11-3-1-10(2-4-11)13-14(24-29(19,25)26)22-9-23-15(13)27-5-6-28-16-20-7-12(18)8-21-16/h1-4,7-9H,5-6H2,(H2,19,25,26)(H,22,23,24)

N-[5-(4-bromophenyl)-6-{2-[(5-bromopyrimidin-2-yl)oxy]ethoxy}pyrimidin-4-yl]sulfuric diamide

ACT 132577; ACT-132577; Aprocitentan; ACT132577; N-Despropyl-macitentan; Tryvio; Aprocitentan [USAN]; Macitentan metabolite m6; MZI81HV01P; Despropyl Macitentan.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~25 mg/mL (~45.77 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.58 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.58 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)