 | |
| Identifiers | |
|---|---|
| |
| CAS Number | |
| PubChem CID | |
| ChemSpider | |
| UNII | |
| Chemical and physical data | |
| Formula | C18H24F2N2O |
| Molar mass | 322.392 g·mol−1 |
| 3D model (JSmol) | |
| |
| |
| (verify) | |
PF-03654746 is a potent and selective histamine H3 receptor antagonist developed by Pfizer and currently undergoing clinical trials for the treatment of ADHD, Tourette syndrome [1] as well as potential anti-allergy applications. [2] [3] [4] [5]
H2 antagonists, sometimes referred to as H2RAs and also called H2 blockers, are a class of medications that block the action of histamine at the histamine H2 receptors of the parietal cells in the stomach. This decreases the production of stomach acid. H2 antagonists can be used in the treatment of dyspepsia, peptic ulcers and gastroesophageal reflux disease. They have been surpassed by proton pump inhibitors (PPIs); the PPI omeprazole was found to be more effective at both healing and alleviating symptoms of ulcers and reflux oesophagitis than the H2 blockers ranitidine and cimetidine.
Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discovered in 1910, it has been considered a local hormone (autocoid) because it lacks the classic endocrine glands to secrete it; however, in recent years, histamine has been recognized as a central neurotransmitter. Histamine is involved in the inflammatory response and has a central role as a mediator of itching. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues. It consists of an imidazole ring attached to an ethylamine chain; under physiological conditions, the amino group of the side-chain is protonated.
Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremors in parkinsonism, and nausea. It is taken by mouth, injected into a vein, injected into a muscle, or applied to the skin. Maximal effect is typically around two hours after a dose, and effects can last for up to seven hours.
Chlorphenamine, also known as chlorpheniramine, is an antihistamine used to treat the symptoms of allergic conditions such as allergic rhinitis. It is taken orally. The medication takes effect within two hours and lasts for about 4-6 hours.
Fexofenadine, sold under the brand name Allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.
Histamine H3 receptors are expressed in the central nervous system and to a lesser extent the peripheral nervous system, where they act as autoreceptors in presynaptic histaminergic neurons and control histamine turnover by feedback inhibition of histamine synthesis and release. The H3 receptor has also been shown to presynaptically inhibit the release of a number of other neurotransmitters (i.e. it acts as an inhibitory heteroreceptor) including, but probably not limited to dopamine, GABA, acetylcholine, noradrenaline, histamine and serotonin.
The histamine H4 receptor, like the other three histamine receptors, is a member of the G protein-coupled receptor superfamily that in humans is encoded by the HRH4 gene.
The H1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors. This receptor is activated by the biogenic amine histamine. It is expressed in smooth muscles, on vascular endothelial cells, in the heart, and in the central nervous system. The H1 receptor is linked to an intracellular G-protein (Gq) that activates phospholipase C and the inositol triphosphate (IP3) signalling pathway. Antihistamines, which act on this receptor, are used as anti-allergy drugs. The crystal structure of the receptor has been determined (shown on the right/below) and used to discover new histamine H1 receptor ligands in structure-based virtual screening studies.
H2 receptors are positively coupled to adenylate cyclase via Gs alpha subunit. It is a potent stimulant of cAMP production, which leads to activation of protein kinase A. PKA functions to phosphorylate certain proteins, affecting their activity. The drug betazole is an example of a histamine H2 receptor agonist.
Causes and origins of Tourette syndrome have not been fully elucidated. Tourette syndrome is an inherited neurodevelopmental disorder that begins in childhood or adolescence, characterized by the presence of multiple motor tics and at least one phonic tic, which characteristically wax and wane. Tourette's syndrome occurs along a spectrum of tic disorders, which includes transient tics and chronic tics.
ABT-239 is an H3-receptor inverse agonist developed by Abbott. It has stimulant and nootropic effects, and has been investigated as a treatment for ADHD, Alzheimer's disease, and schizophrenia. ABT-239 is more active at the human H3 receptor than comparable agents such as thioperamide, ciproxifan, and cipralisant. It was ultimately dropped from human trials after showing the dangerous cardiac side effect of QT prolongation, but is still widely used in animal research into H3 antagonists / inverse agonists.
Ciproxifan is an extremely potent histamine H3 inverse agonist/antagonist.
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic drug that can be bought without a prescription and provides relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. Antihistamines are usually for short-term treatment. Chronic allergies increase the risk of health problems which antihistamines might not treat, including asthma, sinusitis, and lower respiratory tract infection. Consultation of a medical professional is recommended for those who intend to take antihistamines for longer-term use.
Dopamine receptor D1, also known as DRD1. It is one of the two types of D1-like receptor family — receptors D1 and D5. It is a protein that in humans is encoded by the DRD1 gene.
An H3 receptor antagonist is a type of antihistaminic drug used to block the action of histamine at H3 receptors.
JNJ-7777120 was a drug being developed by Johnson & Johnson Pharmaceutical Research & Development which acts as a potent and selective antagonist at the histamine H4 receptor. It has anti-inflammatory effects, and has been demonstrated to be superior to traditional (H1) antihistamines in the treatment of pruritus (itching). The drug was abandoned because of its short in vivo half-life and hypoadrenocorticism toxicity in rats and dogs, that prevented advancing it into clinical studies.
GSK-189,254 is a potent and selective H3 histamine receptor inverse agonist developed by GlaxoSmithKline. It has subnanomolar affinity for the H3 receptor (Ki = 0.2nM) and selectivity of over 10,000x for H3 over other histamine receptor subtypes. Animal studies have shown it to possess not only stimulant and nootropic effects, but also analgesic action suggesting a role for H3 receptors in pain processing in the spinal cord. GSK-189,254 and several other related drugs are currently being investigated as a treatment for Alzheimer's disease and other forms of dementia, as well as possible use in the treatment of conditions such as narcolepsy, or neuropathic pain which do not respond well to conventional analgesic drugs.
Pitolisant, sold under the brand name Wakix among others, is a medication for the treatment of excessive daytime sleepiness in adults with narcolepsy. It is a histamine 3 (H3) receptor antagonist/inverse agonist. It represents the first commercially available medication in its class. Pitolisant enhances the activity of histaminergic neurons in the brain that function to improve a person's wakefulness.
Ecopipam is a dopamine antagonist which is under development for the treatment of Lesch-Nyhan syndrome, Tourette's syndrome, speech disorders, and restless legs syndrome. It is taken by mouth.
Toreforant (JNJ-38518168) is an orally-dosed selective antagonist of the histamine H4 receptor that has been studied for various health conditions. It is the successor of a number of H4-selective compounds developed by Johnson & Johnson. Phase IIa clinical trials completed as recently as November 2018 continue to suggest that toreforant is safe.
 | This pharmacology-related article is a stub. You can help Wikipedia by expanding it. |
