This is a list of agonists of the serotonin receptor subtype 5-HT2A (and other 5-HT2 subtypes to a varying extent) which fall outside the common structural classes. Most agonists at this receptor are either substituted phenethylamine derivatives from the 2C, DOx and 25-NB groups, or substituted tryptamines and related compounds along with more complex derivatives of these such as lysergamides and iboga-type alkaloids. [1] There are however numerous 5-HT2A receptor agonists which do not fall within any of these groups, some representative examples of which are listed below. Ki and EC50 values vary depending on the assay conditions used and so may not be directly comparable between sources. Many of these compounds have been designed to be non-psychoactive derivatives for medical applications, and it should not be assumed that a compound which acts as a 5-HT2A agonist will necessarily be psychedelic in nature. [2]
Structure | Name | Chemical name | h5-HT2A Ki (EC50) (nM) | PubChem | CAS number | Reference |
---|---|---|---|---|---|---|
Compound 11a | 11-chloro-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,7-a]indole | 6.5 | 20726100 | 599173-28-1 | [3] | |
Compound 23 | 9-Chloro-7-(2-ethoxy-phenyl)-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,7-a]indole | 32 | 44315398 | 599173-25-8 | [3] | |
Compound 10d | 7-Benzyloxy-8-bromo-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine | 22 | 10472780 | 616201-60-6 | [4] | |
Example 22.67 | 4-(6,7,8,9-tetrahydro-5H-pyrido[2,3-d]azepin-2-yl)thiomorpholine | 21 | 44124494 | [5] | ||
Compound 3d (N-Bn-THAZ) | 2-benzyl-5,6,7,8-tetrahydro-4H-[1,2]oxazolo[4,5-d]azepin-3-one | (549) | 14515725 | 125115-66-4 | [6] | |
Compound 11 | (3R)-N,N-diethyl-5-(1H-indol-4-yl)-1-methyl-3,6-dihydro-2H-pyridine-3-carboxamide | (<10) | 156278040 | [7] | ||
Compound 106 | 6-chloro-1-(2,4,5-trimethoxyphenyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole | 4376990 | 528525-37-3 | [8] | ||
Compound 6c | (6S)-2,3-dichloro-7,8,9,10-tetrahydro-6H-6,9-epiminocyclohepta[b]quinoxaline | (400) | [9] | |||
Compound 70 | 3-(4-bromo-2-methylpyrazol-3-yl)-N-(4-chlorophenyl)-4-methoxyaniline | 1.77 | 9952456 | [10] | ||
Compound 22 | 7-(trifluoromethoxy)-2,3,4,10b-tetrahydro-1H-pyrazino[1,2-b]isoindol-6-one | 67 (87) | 11448649 | [10] | ||
Example 1 (ZC-B) | 3-(4-bromo-2,5-dimethoxyphenyl)azetidine | (1.6) | 156337249 | 2641630-65-9 | [11] | |
2C-B-aminorex | 5-(4-bromo-2,5-dimethoxyphenyl)-4,5-dihydro-1,3-oxazol-2-amine | 165360199 | [12] | |||
2-(2,5-dimethoxy-4-bromophenyl)morpholine | 2-(2,5-dimethoxy-4-bromophenyl)morpholine | 20.6 | 11429275 | [13] | ||
LPH-5 | (3S)-3-[2,5-dimethoxy-4-(trifluoromethyl)phenyl]piperidine | (3.2) | 156337168 | 2641630-97-7 | [14] | |
2C-B-PP | 1-(2,5-dimethoxy-4-bromophenyl)piperazine | 4738744 | 100939-87-5 | [15] | ||
cis-urocanic acid (cis-UCA) | (Z)-3-(1H-imidazol-5-yl)prop-2-enoic acid | 4.6 | 1549103 | 7699-35-6 | [16] [17] [18] | |
CPD-1 | (3S)-3-Methyl-1-[4-(trifluoromethyl)-1-benzofuran-7-yl]piperazine | 9925822 | 325145-37-7 | [19] | ||
Efavirenz | (4S)-6-Chloro-4-(2-cyclopropylethynyl)-4-(trifluoromethyl)-2,4-dihydro-1H-3,1-benzoxazin-2-one | 64139 | 154598-52-4 | [20] | ||
IHCH-7079 | (6bR,10aS)-8-(2-Methoxyphenethyl)-3-methyl-2,3,6b,7,8,9,10,10a-octahydro-1H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxaline | 169488014 | 2957888-63-8 | [21] | ||
IHCH-7113 | (6bR,10aS)-3-methyl-2,3,6b,7,8,9,10,10a-octahydro-1H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxaline | 21302499 | 313368-85-3 | [21] | ||
NDTDI | N,N-diethyl-3-[methyl(1,3,4,5-tetrahydrobenzo[cd]indol-4-yl)amino]propanamide | 163192742 | [22] | |||
Mefloquine | 2,8-bis(trifluoromethyl)quinolin-4-yl-(2-piperidyl)methanol | 40692 | 53230-10-7 | [23] | ||
ORG-12962 | 1-(5-trifluoromethyl-6-chloropyridin-2-yl)piperazine | 9796408 | 210821-63-9 | [24] | ||
ORG-37684 | (3S)-3-[(2,3-dihydro-5-methoxy-1H-inden-4-yl)oxy]pyrrolidine | 9794656 | 213007-95-5 | [25] | ||
OSU-6162 | (3S)-3-[3-(methylsulfonyl)phenyl]-1-propylpiperidine | 9795741 | 156907-84-5 | [26] | ||
PHA-57378 | 2,7,8,9,10,11-hexahydro-1H-azepino[4,5-b][1,4]oxazino[2,3,4-hi]indole | 4.1 | 10198481 | 303798-94-9 | [3] | |
P-54 | 2-(5-methoxypyrazolo[1,5-a]pyridin-3-yl)-N,N-dimethylethanamine | 168946740 | [27] | |||
(R)-69 | 3-[(5R)-5-methyl-1,2,5,6-tetrahydropyridin-3-yl]-1H-pyrrolo[2,3-b]pyridine | 164513426 | [28] | |||
RS134-49 | 4-methyl-3-(1,2,3,6-tetrahydropyridin-5-yl)-1H-indole | 168941768 | [29] [30] | |||
RH-34 | 3-[2-(2-methoxybenzylamino)ethyl]-1H-quinazoline-2,4-dione | 10041987 | 1028307-48-3 | [31] | ||
SCHEMBL5334361 | 7-[(3-methoxyphenoxy)methyl]-2,3,4,5-tetrahydro-1H-3-benzazepine | (0.4) | 59027940 | 959867-47-1 | [32] | |
Tabernanthalog | 8-methoxy-3-methyl-2,4,5,6-tetrahydro-1H-azepino[4,5-b]indole | 146026994 | 2483829-59-8 | [33] | ||
TKU-II-100 | [(1S,2S)-2-(2-fluorophenyl)cyclopropyl]methanamine | 0.62 | 44572747 | [34] | ||
WAY-470 | 1,16-diazatetracyclo[8.8.1.02,9.014,19]nonadeca-2(9),10,12,14(19)-tetraene | 36 | 10037962 | [35] | ||
WXVL_BT0793LQ2118 | 6-fluoro-4-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1H-indole | [36] | ||||
Z2825713589 | (4-amino-3,3a,4,5,6,6a-hexahydro-1H-cyclopenta[c]pyrrol-2-yl)-(6-methoxypyrazin-2-yl)methanone | 167788805 | [36] | |||
Z2876442907 | ethyl 2-[[2-(4-methyl-1H-indol-3-yl)ethylamino]methyl]-1,3-thiazole-5-carboxylate | 167850865 | [36] | |||
Z3517967757 | 4-[1-(1-pyrimidin-2-ylethyl)piperidin-3-yl]phenol | 167949972 | [36] | |||
Z3881312504 | 2-bromo-4-[2-[methyl-[2-(1,3-thiazol-2-yl)ethyl]amino]ethyl]phenol | 167904469 | [36] | |||
Z4154032166 | 2,2,2-trifluoro-1-[6-(1,2,3,6-tetrahydropyridin-5-yl)pyridin-2-yl]ethanol | 167878716 | [36] | |||
Z5247692566 | 4-[(3,3-dimethyloxolan-2-yl)methyl]-3-[(1H-indol-3-yl)methyl]morpholine | [36] | ||||
Z5247692629 | 1-(1-bicyclo[1.1.1]pentanyl)-4-[[5-(4-chlorophenyl)-1H-pyrazol-4-yl]methyl]piperazine | 166358273 | [36] | |||
Psilocin is a substituted tryptamine alkaloid and a serotonergic psychedelic substance. It is present in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin. Psilocin is a Schedule I drug under the Convention on Psychotropic Substances. Acting on the 5-HT2A receptors, psilocin modulates the production and reuptake of serotonin. The mind-altering effects of psilocin are highly variable and subjective and resemble those of LSD and DMT.
2C-BFLY is a psychedelic phenethylamine and designer drug of the 2C family. It was first synthesized in 1996 by Aaron Monte, Professor of Chemistry at UW-La Crosse.
The 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations.
A serotonin receptor agonist is an agonist of one or more serotonin receptors. They activate serotonin receptors in a manner similar to that of serotonin, a neurotransmitter and hormone and the endogenous ligand of the serotonin receptors.
TCB-2 is a hallucinogen discovered in 2006 by Thomas McLean working in the lab of David Nichols at Purdue University. It is a conformationally-restricted derivative of the phenethylamine 2C-B, also a hallucinogen, and acts as a potent agonist for the 5-HT2A and 5-HT2C receptors with a Ki of 0.26 nM at the human 5-HT2A receptor. In drug-substitution experiments in rats, TCB-2 was found to be of similar potency to both LSD and Bromo-DragonFLY, ranking it among the most potent phenethylamine hallucinogens yet discovered. This high potency and selectivity has made TCB-2 useful for distinguishing 5-HT2A mediated responses from those produced by other similar receptors. TCB-2 has similar but not identical effects in animals to related phenethylamine hallucinogens such as DOI, and has been used for studying how the function of the 5-HT2A receptor differs from that of other serotonin receptors in a number of animal models, such as studies of cocaine addiction and neuropathic pain.
YM-348 is an indazole derivative drug which acts as a potent and selective 5-HT2C receptor agonist, with an EC50 of 1nM and 15x selectivity over 5-HT2A, although it only has moderate selectivity of 3x over the closely related 5-HT2B receptor. It has thermogenic and anorectic effects in animal studies, making it potentially useful for the treatment of obesity.
PNU-22394 is a drug which acts as an agonist at serotonin 5-HT2 receptors, with strongest binding affinity for 5-HT2A and 5-HT2C and slightly weaker at 5-HT2B, although it is only a full agonist at 5-HT2C, but partial agonist at 5-HT2A and 5-HT2B. It has anorectic effects in both animal studies and human trials, along with "Pro-Cognitive Properties", although it has never been developed for medical use.
Adatanserin is a mixed 5-HT1A receptor partial agonist and 5-HT2A and 5-HT2C receptor antagonist. It was under development by Wyeth as an antidepressant but was ultimately not pursued.
SB-206553 is a drug which acts as a mixed antagonist for the 5-HT2B and 5-HT2C serotonin receptors. It has anxiolytic properties in animal studies and interacts with a range of other drugs. It has also been shown to act as a positive allosteric modulator of α7 nicotinic acetylcholine receptors. Modified derivatives of SB-206553 have been used to probe the structure of the 5-HT2B receptor.
Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH2) group via an ethyl (−CH2–CH2−) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.
5-MeO-NBpBrT is a N-substituted member of the methoxytryptamine family of compounds. Like other such compounds it acts as an antagonist for the 5-HT2A receptor, with a claimed 100x selectivity over the closely related 5-HT2C receptor. While N-benzyl substitution of psychedelic phenethylamines often results in potent 5-HT2A agonists, it had been thought that N-benzyl tryptamines show much lower efficacy and are either very weak partial agonists or antagonists at 5-HT2A, though more recent research has shown stronger agonist activity for 3-substituted benzyl derivatives. Extending the benzyl group to a substituted phenethyl can also recover agonist activity in certain cases.
5-HT2C receptor agonists are a class of drugs that activate 5-HT2C receptors. They have been investigated for the treatment of a number of conditions including obesity, psychiatric disorders, sexual dysfunction and urinary incontinence.
PNU-181731 is a drug which acts as an agonist at serotonin 5-HT2 receptors, with strongest binding affinity for the 5-HT2C subtype at 4.8nM, and weaker 5-HT2A affinity of 18nM. It has anxiolytic effects in animal studies with around one tenth the potency of alprazolam and no significant ataxia or other side effects noted.
PHA-57378 is a drug which acts as an agonist at serotonin 5-HT2 receptors, having a binding affinity of 4.1 nM at the 5-HT2A subtype and 4.3 nM at 5-HT2C. It has anxiolytic effects in animal studies.
25CN-NBOH is a compound indirectly derived from the phenethylamine series of hallucinogens, which was discovered in 2014 at the University of Copenhagen. This compound is notable as one of the most selective agonist ligands for the 5-HT2A receptor yet discovered, with a pKi of 8.88 at the human 5-HT2A receptor and with 100x selectivity for 5-HT2A over 5-HT2C, and 46x selectivity for 5-HT2A over 5-HT2B. A tritiated version of 25CN-NBOH has also been accessed and used for more detailed investigations of the binding to 5-HT2 receptors and autoradiography.
1-Methylpsilocin is a tryptamine derivative which acts as a selective agonist for the 5-HT2C receptor (IC50 of 12 nM, vs 633 nM at 5-HT2A), and an inverse agonist at 5-HT2B (Ki of 38 nM). While 1-methylpsilocin does have higher affinity for 5-HT2C than 5-HT2A, it does produce a head-twitch response in mice that are dependent on 5-HT2A, so it is not entirely free of effects on 5-HT2A in vivo. In contrast to psilocin, 1-methylpsilocin did not activate 5-HT1A receptors in mice. 1-Methylpsilocin has been investigated for applications such as treatment of glaucoma, OCD, and cluster headaches, as these conditions are amenable to treatment with psychedelic drugs but are not generally treated with such agents due to the hallucinogenic side effects they produce, which are considered undesirable. 1-Methylpsilocin therefore represents a potential alternative treatment to psilocin that may be less likely to produce hallucinogenic effects.
2C-B-BUTTERFLY is a conformationally-restricted derivative of the phenethylamine hallucinogen 2C-B, which was discovered in 1999 by Michael S. Whiteside and Aaron Monte. It is a ring-expanded homologue of the better known compound 2C-B-FLY, and has similar properties as an agonist for serotonin receptors, but with more selectivity for 5-HT2C over 5-HT2A.
The 25-NB (25x-NBx) series, sometimes alternatively referred to as the NBOMe compounds, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C family. They act as selective agonists of the serotonin 5-HT2A receptor. The 25-NB family is unique relative to other classes of psychedelics in that they are, generally speaking, extremely potent and relatively selective for the 5-HT2A receptor. Use of NBOMe series drugs has caused many deaths and hospitalisations since the drugs popularisation in the 2010s. This is primarily due to their high potency, unpredictable pharmacokinetics, and sellers passing off the compounds in the series as LSD.
CPD-1 (LS-193743) is a drug with a benzofuranyl piperazine structure, which acts as a potent and selective agonist for the 5-HT2 receptor family, with highest affinity and full agonist efficacy at the 5-HT2C subtype, and lower affinity and partial agonist action at the 5-HT2A and 5-HT2B subtypes.
CYB210010 (2C-T-TFM) is a lesser-known psychedelic drug related to compounds such as 2C-T-21. Alexander Shulgin attempted to synthesise this compound in the 1990s, and mentions it in his book PiHKAL under the entry for 2C-T-21, but was unsuccessful in producing a key intermediate and never assigned it a 2C-T number. This compound was ultimately first synthesised by Geoffrey Varty and colleagues at Irish biopharmaceutical company Cybin in 2023. It has a Ki of 0.35 nM at 5-HT2A, and an EC50 of 4.1 nM at 5-HT2A and 7.3 nM at 5-HT2C, compared to 88 nM at 5-HT2B. It is a potent, selective, long acting and orally active agonist for the 5-HT2A and 5-HT2C receptors and produces psychedelic-like responding in several different animal species. It is not known to have been tested in humans.