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Trade names | Opsumit |
Other names | ACT-064992 |
AHFS/Drugs.com | Monograph |
MedlinePlus | a615033 |
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Routes of administration | By mouth |
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Metabolism | Hydrolysis, oxidation (CYP3A4) |
Excretion | 2/3 urine, 1/3 faeces |
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Chemical and physical data | |
Formula | C19H20Br2N6O4S |
Molar mass | 588.28 g·mol−1 |
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Macitentan, sold under the brand name Opsumit, is an endothelin receptor antagonist developed by Actelion and approved for the treatment of pulmonary arterial hypertension (PAH). [5] Macitentan is a dual endothelin receptor antagonist, meaning that it acts as an antagonist of two endothelin (ET) receptor subtypes, ETA and ETB. [5] However, macitentan has a 50-fold increased selectivity for the ETA subtype compared to the ETB subtype. [6]
Macitentan was approved for medical use in the United States in October 2013. [3] [7] Macitentan is available as a generic medication. [8]
The FDA prescription label contains a boxed warning for embryo-fetal toxicity. It is only available to females in the US through a risk evaluation and mitigation strategy (REMS) program. [3]
This section may be too technical for most readers to understand.(March 2014) |
Endothelin (ET) is an extremely potent blood vessel constricting substance that is secreted by endothelial cells. [9] In the lungs, the most common ET form released is ET-1. [9] ET-1 release can occur through both constitutive and non-constitutive pathways. [9] Upon release, ET-1 can bind to the ET receptors that are expressed on arterial smooth muscle cells and fibroblasts in the lungs. [9] ET receptors are G protein coupled receptors and, when activated, lead to an increase in intracellular calcium levels via the Gαq signaling pathway. [9] There are two receptor subtypes that endothelin will bind to: ETA and ETB. ETA is associated with cell growth and vasoconstriction while ETB is responsible for anti-proliferation of cells, vasodilation and ET-1 clearance. The rise in intracellular calcium leads to contraction of the arterial smooth muscle, as well as vascular remodelling due to cell proliferation. [9] Prolonged constriction and fibrosis are factors in the pathogenesis of PAH. [5]
Macitentan blocks the ET1-dependent rise in intracellular calcium by inhibiting the binding of ET-1 to ET receptors. Blocking of the ETA receptor subtype seems to be of more importance in the treatment of PAH than blocking of ETB, likely because there are higher numbers of ETA receptors than ETB receptors in pulmonary arterial smooth muscle cells. [9] The blocking of Endothelin 1 leads to vasodilation and decreases the proliferation of cells in the vessels of the arteries which contributes to the narrowing and leads to the pulmonary arterial hypertension.
Macitentan is taken as a 10 mg oral dose once a day. [5] Its half-life in humans is about 16 hours and steady state is reached by the third day of administration. [10] It is absorbed slowly into the plasma. [11] Macitentan dealkylates into the active metabolite aprocitentan (ACT-132577), which reaches its peak plasma concentration about 30 hours after the first dose is administered, and has a half-life of approximately 48 hours. [11] Although aprocitentan has a lower affinity for the ET receptors than its parent compound, [6] It maintains higher plasma concentrations than macitentan. [11] Both compounds can be excreted from the body through the urine or feces. [10]
Co-administration of ciclosporin has only a slight effect on the concentrations of macitentan and its active metabolite, while rifampicin decreases the area under the curve (AUC) of the drug's blood plasma concentration by 79%, and ketoconazole approximately doubles it. This corresponds to the finding that macitentan is mainly metabolised via the liver enzyme CYP3A4. [12]
Macitentan has slow association kinetics. [9] Its potency increases 6.3-fold when it is pre-incubated with pulmonary arterial smooth muscle cells for 120 minutes compared to 10 minutes with pulmonary arterial smooth muscle cells. [9] Macitentan also has a high receptor occupancy half-life (approximately 17 minutes) compared to bosentan (approximately 70 seconds) and ambrisentan (approximately 40 seconds). [9] This increased receptor occupancy half-life allows macitentan to act as a non-competitive antagonist of ET receptors. [9] Bosentan and ambrisentan are both competitive antagonists. [9]
Pulmonary hypertension is a condition of increased blood pressure in the arteries of the lungs. Symptoms include shortness of breath, fainting, tiredness, chest pain, swelling of the legs, and a fast heartbeat. The condition may make it difficult to exercise. Onset is typically gradual. According to the definition at the 6th World Symposium of Pulmonary Hypertension in 2018, a patient is deemed to have pulmonary hypertension if the pulmonary mean arterial pressure is greater than 20mmHg at rest, revised down from a purely arbitrary 25mmHg, and pulmonary vascular resistance (PVR) greater than 3 Wood units.
Sitaxentan sodium (TBC-11251) is a medication for the treatment of pulmonary arterial hypertension (PAH). It was marketed as Thelin by Encysive Pharmaceuticals until Pfizer purchased Encysive in February 2008. In 2010, Pfizer voluntarily removed sitaxentan from the market due to concerns about liver toxicity.
An endothelin receptor antagonist (ERA) is a drug that blocks endothelin receptors.
Endothelins are peptides with receptors and effects in many body organs. Endothelin constricts blood vessels and raises blood pressure. The endothelins are normally kept in balance by other mechanisms, but when overexpressed, they contribute to high blood pressure (hypertension), heart disease, and potentially other diseases.
Bosentan, sold under the brand name Tracleer among others, is a dual endothelin receptor antagonist medication used in the treatment of pulmonary artery hypertension (PAH).
Iloprost, sold under the brand name Ventavis among others, is a medication used to treat pulmonary arterial hypertension (PAH), scleroderma, Raynaud's phenomenon, frostbite, and other conditions in which the blood vessels are constricted and blood cannot flow to the tissues. Iloprost is a prostacyclin mimetic.
Portopulmonary hypertension (PPH) is defined by the coexistence of portal and pulmonary hypertension. PPH is a serious complication of liver disease, present in 0.25 to 4% of all patients with cirrhosis. Once an absolute contraindication to liver transplantation, it is no longer, thanks to rapid advances in the treatment of this condition. Today, PPH is comorbid in 4-6% of those referred for a liver transplant.
There are at least four known endothelin receptors, ETA, ETB1, ETB2 and ETC, all of which are G protein-coupled receptors whose activation result in elevation of intracellular-free calcium, which constricts the smooth muscles of the blood vessels, raising blood pressure, or relaxes the smooth muscles of the blood vessels, lowering blood pressure, among other functions.
Ambrisentan, sold under the brand name Letairis among others, is a drug used for the treatment of pulmonary hypertension. It is an endothelin receptor antagonist.
Endothelin 1 (ET-1), also known as preproendothelin-1 (PPET1), is a potent vasoconstrictor peptide produced by vascular endothelial cells, as well as by cells in the heart and kidney. The protein encoded by this gene – EDN1 – is proteolytically processed to release endothelin 1. Endothelin 1 is one of three isoforms of human endothelin.
Atrasentan is an experimental drug that is being studied for the treatment of various types of cancer, including non-small cell lung cancer. It is also being investigated as a therapy for diabetic kidney disease.
Endothelin receptor type B, (ET-B) is a protein that in humans is encoded by the EDNRB gene.
Endothelin receptor type A, also known as ETA, is a human G protein-coupled receptor.
Endothelin-3 is a protein that in humans is encoded by the EDN3 gene.
Terguride, sold under the brand name Teluron, is a serotonin receptor antagonist and dopamine receptor agonist of the ergoline family. It is approved for and used as a prolactin inhibitor in the treatment of hyperprolactinemia in Japan. Terguride is taken by mouth.
Riociguat, sold under the brand name Adempas, is a medication by Bayer that is a stimulator of soluble guanylate cyclase (sGC). It is used to treat two forms of pulmonary hypertension (PH): chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary arterial hypertension (PAH). Riociguat constitutes the first drug of the class of sGC stimulators. The drug has a half-life of 12 hours and will decrease dyspnea associated with pulmonary arterial hypertension.
PRX-08066 is a drug discovered and developed by Predix Pharmaceuticals [Dale S. Dhanoa et al. Patent US 7,030,240 B2], which acts as a potent and selective antagonist at the serotonin 5-HT2B receptor, with a 5-HT2Bbinding affinity (Ki) of 3.4nM, and high selectivity over the closely related 5-HT2A and 5-HT2C receptors and other receptor targets. PRX-08066 and other selective 5-HT2B antagonists are being researched for the treatment of pulmonary arterial hypertension, following the discovery that the potent 5-HT2B agonist norfenfluramine produces pulmonary arterial hypertension and subsequent heart valve damage. In animal studies, PRX-08066 has been found to reduce several key indicators of pulmonary arterial hypertension and improved cardiac output, with similar efficacy to established drugs for this condition such as bosentan, sildenafil, beraprost and iloprost. It is also being researched for potential anti-cancer applications, due to its ability to inhibit fibroblast activation.
Actelion Pharmaceuticals Ltd. is a pharmaceuticals and biotechnology company established in December 1997, headquartered in Allschwil near Basel, Switzerland.
Selexipag, sold under the brand name Uptravi, is a medication developed by Actelion for the treatment of pulmonary arterial hypertension (PAH). Selexipag and its active metabolite, ACT-333679, are agonists of the prostacyclin receptor, which leads to vasodilation in the pulmonary circulation. It is taken by mouth or administered intravenously.
Sarafotoxins (SRTXs) are a group of toxins present in the venom of Atractaspis engaddensis, and in clinical trials cause similar symptoms to patients diagnosed with acute giardiasis. Their etymology is from the name of the snake "שרף עין גדי" in Hebrew, pronounced "Saraf Ein Gedi". Together with endothelins (ETs), they form a homogenous family of strong vasoconstrictor isopeptides. Among them, a few slightly different substances can be named as SRTX-a, SRTX-b, SRTX-c, which were initially derived from A. engaddensis. Each one contains twenty-one amino acid residues that spontaneously fold into a defined tertiary structure, with two interchain-cysteine linkages and a long hydrophobic tail. There are also other compounds, however, they are mostly derivations of previously mentioned ones. The main differences in the family of endothelin and sarafotoxins appear at N-terminal of peptides, as C-terminal in all of them is almost the same.
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