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An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins. They are sometimes called blockers; examples include alpha blockers, beta blockers, and calcium channel blockers. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, and binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors. Antagonists mediate their effects by binding to the active site or to the allosteric site on a receptor, or they may interact at unique binding sites not normally involved in the biological regulation of the receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist–receptor complex, which, in turn, depends on the nature of antagonist–receptor binding. The majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally defined binding sites on receptors.
ATC code C02Antihypertensives is a therapeutic subgroup of the Anatomical Therapeutic Chemical Classification System, a system of alphanumeric codes developed by the World Health Organization (WHO) for the classification of drugs and other medical products. Subgroup C02 is part of the anatomical group C Cardiovascular system.
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.
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).
An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.
The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP for its ligand ketazocine, is a G protein-coupled receptor that in humans is encoded by the OPRK1 gene. The KOR is coupled to the G protein Gi/G0 and is one of four related receptors that bind opioid-like compounds in the brain and are responsible for mediating the effects of these compounds. These effects include altering nociception, consciousness, motor control, and mood. Dysregulation of this receptor system has been implicated in alcohol and drug addiction.
Signaling peptide receptor is a type of receptor which binds one or more signaling peptides or signaling proteins.
Ambrisentan is a drug indicated for use in the treatment of pulmonary hypertension.
Endothelin 1 (ET-1), also known as preproendothelin-1 (PPET1), is a potent vasoconstrictor peptide produced by vascular endothelial cells. 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.
BQ-123, also known as cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu-), is a cyclic pentapeptide that was first isolated from a fermentation broth of Streptomyces misakiensis in 1991. NMR studies indicate that the polypeptide backbone consists of a type II beta turn and an inverse gamma turn. The side-chains adopt different orientations depending on the solvent used. The proline carbonyl oxygen atom located at the onset of a beta turn is a sodium ion binding site. It has a high affinity for sodium ions and can coordinate up to three of them. Studies have shown that BQ123 is effective in reversing Ischemia-induced acute renal failure, and it has been suggested that this might be because BQ123 increases reabsorption of sodium ions in the proximal tubule cells.
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 is a pharmaceuticals and biotechnology company established in December 1997, headquartered in Allschwil near Basel, Switzerland.
Macitentan, sold under the brand name Opsumit, is an endothelin receptor antagonist (ERA) developed by Actelion and approved for the treatment of pulmonary arterial hypertension (PAH). The other two ERAs marketed as of 2014 are bosentan and ambrisentan. Macitentan is a dual ERA, meaning that it acts as an antagonist of two endothelin (ET) receptor subtypes, ETA and ETB. However, macitentan has a 50-fold increased selectivity for the ETA subtype compared to the ETB subtype. The drug received approval from the U.S. Food and Drug Administration (FDA) on October 13, 2013.
BQ-788 is a selective ETB antagonist.
Aprocitentan is an endothelin receptor antagonist active at both endothelin A and endothelin B receptors. It is developed for resistant hypertension by Idorsia, which sold it to Janssen but purchased the rights back in 2023 for $343 million.
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