Cannabinoids are several structural classes of compounds found in the cannabis plant primarily and most animal organisms or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoactive compound in cannabis. Cannabidiol (CBD) is also a major constituent of temperate cannabis plants and a minor constituent in tropical varieties. At least 100 distinct phytocannabinoids have been isolated from cannabis, although only four have been demonstrated to have a biogenetic origin. It was reported in 2020 that phytocannabinoids can be found in other plants such as rhododendron, licorice and liverwort, and earlier in Echinacea.
Rimonabant (also known as SR141716; trade names Acomplia, Zimulti) is an anorectic antiobesity drug approved in Europe in 2006 but was withdrawn worldwide in 2008 due to serious psychiatric side effects; it was never approved in the United States. Rimonabant is an inverse agonist for the cannabinoid receptor CB1 and was first-in-class for clinical development.
Tetrahydrocannabivarin is a homologue of tetrahydrocannabinol (THC) having a propyl (3-carbon) side chain instead of pentyl (5-carbon), making it non-psychoactive in lower doses. It has been shown to exhibit neuroprotective activity, appetite suppression, glycemic control and reduced side effects compared to THC, making it a potential treatment for management of obesity and diabetes. THCV was studied by Roger Adams as early as 1942.
Taranabant (codenamed MK-0364) is a cannabinoid receptor type 1 (CB1) inverse agonist that was investigated as a potential treatment for obesity due to its anorectic effects. It was developed by Merck & Co.
VCHSR is a drug used in scientific research which acts as a selective antagonist of the cannabinoid receptor CB1. It is derived from the widely used CB1 antagonist rimonabant, and has similar potency and selectivity for the CB1 receptor, but has been modified to remove the hydrogen bonding capability in the C-3 substituent region, which removes the inverse agonist effect that rimonabant produces at high doses, so that VCHSR instead acts as a neutral antagonist, blocking the receptor but producing no physiological effect of its own.
A cannabinoid receptor antagonist, also known simply as a cannabinoid antagonist or as an anticannabinoid, is a type of cannabinoidergic drug that binds to cannabinoid receptors (CBR) and prevents their activation by endocannabinoids. They include antagonists, inverse agonists, and antibodies of CBRs. The discovery of the endocannabinoid system led to the development of CB1 receptor antagonists. The first CBR inverse agonist, rimonabant, was described in 1994. Rimonabant blocks the CB1 receptor selectively and has been shown to decrease food intake and regulate body-weight gain. The prevalence of obesity worldwide is increasing dramatically and has a great impact on public health. The lack of efficient and well-tolerated drugs to cure obesity has led to an increased interest in research and development of CBR antagonists. Cannabidiol (CBD), a naturally occurring cannabinoid and a non-competitive CB1/CB2 receptor antagonist, as well as Δ9-tetrahydrocannabivarin (THCV), a naturally occurring cannabinoid, modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. CBD is a very low-affinity CB1 ligand, that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant.
Ibipinabant (SLV319, BMS-646,256) is a drug used in scientific research which acts as a potent and highly selective CB1 antagonist. It has potent anorectic effects in animals, and was researched for the treatment of obesity, although CB1 antagonists as a class have now fallen out of favour as potential anorectics following the problems seen with rimonabant, and so ibipinabant is now only used for laboratory research, especially structure-activity relationship studies into novel CB1 antagonists. SLV330, which is a structural analogue of Ibipinabant, was reported active in animal models related to the regulation of memory, cognition, as well as in addictive behavior. An atom-efficient synthesis of ibipinabant has been reported.
CB-13 (CRA13, SAB-378) is a cannabinoid drug, which acts as a potent agonist at both the CB1 and CB2 receptors, but has poor blood–brain barrier penetration, and so produces only peripheral effects at low doses, with symptoms of central effects such as catalepsy only appearing at much higher dose ranges. It has antihyperalgesic properties in animal studies, and has progressed to preliminary human trials.
AM-630 (6-Iodopravadoline) is a drug that acts as a potent and selective inverse agonist for the cannabinoid receptor CB2, with a Ki of 32.1 nM at CB2 and 165x selectivity over CB1, at which it acted as a weak partial agonist. It is used in the study of CB2 mediated responses and has been used to investigate the possible role of CB2 receptors in the brain. AM-630 is significant as one of the first indole derived cannabinoid ligands substituted on the 6-position of the indole ring, a position that has subsequently been found to be important in determining affinity and efficacy at both the CB1 and CB2 receptors, and has led to the development of many related derivatives.
AM-2233 is a drug that acts as a highly potent full agonist for the cannabinoid receptors, with a Ki of 1.8 nM at CB1 and 2.2 nM at CB2 as the active (R) enantiomer. It was developed as a selective radioligand for the cannabinoid receptors and has been used as its 131I derivative for mapping the distribution of the CB1 receptor in the brain. AM-2233 was found to fully substitute for THC in rats, with a potency lower than that of JWH-018 but higher than WIN 55,212-2.
SR144528 is a drug that acts as a potent and highly selective CB2 receptor inverse agonist, with a Ki of 0.6 nM at CB2 and 400 nM at the related CB1 receptor. It is used in scientific research for investigating the function of the CB2 receptor, as well as for studying the effects of CB1 receptors in isolation, as few CB1 agonists that do not also show significant activity as CB2 agonists are available. It has also been found to be an inhibitor of sterol O-acyltransferase, an effect that appears to be independent from its action on CB2 receptors.
O-1269 is a drug that is a diarylpyrazole derivative, related to potent cannabinoid antagonist drugs such as rimonabant and surinabant. However O-1269 and several related drugs were unexpectedly found to act as full or partial agonists at the cannabinoid receptors rather than antagonists, and so produce the usual effects expected of cannabinoid agonists in animal tests, such as sedation and analgesic effects. The N-heptyl homolog O-1270 and the N-propyl homolog O-1399 also act as cannabinoid agonists with similar potency in vivo, despite weaker binding affinity at cannabinoid receptors compared to the pentyl homolog O-1269. Agonist-like and atypical cannabinoid activity has also been observed with a number of related compounds.
AM-6545 is a drug which acts as a peripherally selective silent antagonist for the CB1 receptor, and was developed for the treatment of obesity. Other cannabinoid antagonists such as rimonabant have been marketed for this application, but have subsequently been withdrawn from sale because of centrally mediated side effects such as depression and nausea. Because AM-6545 does not cross the blood–brain barrier to any significant extent, it does not produce these kinds of side effects, but has still been shown to effectively reduce appetite and food consumption in animal studies.
Rosonabant (INN; E-6776) is a drug acting as a CB1 receptor antagonist/inverse agonist that was under investigation by Esteve as an appetite suppressant for the treatment of obesity. Development of the drug for clinical use was apparently halted shortly after the related CB1 antagonist rimonabant was discontinued in November 2008, due to the reports of severe psychiatric adverse effects such as anxiety, depression, and suicidal ideation associated with it and with similarly acting agents.
Drinabant (INN; AVE-1625) is a drug that acts as a selective CB1 receptor antagonist, which was under investigation varyingly by Sanofi-Aventis as a treatment for obesity, schizophrenia, Alzheimer's disease, Parkinson's disease, and nicotine dependence. Though initially studied as a potential treatment for a variety of different medical conditions, Sanofi-Aventis eventually narrowed down the therapeutic indications of the compound to just appetite suppression. Drinabant reached phase IIb clinical trials for this purpose in the treatment of obesity but was shortly thereafter discontinued, likely due to the observation of severe psychiatric side effects including anxiety, depression, and thoughts of suicide in patients treated with the now-withdrawn rimonabant, another CB1 antagonist that was also under development by Sanofi-Aventis.
LBP-1 is a drug originally developed by Organon for the treatment of neuropathic pain, It acts as a potent and selective cannabinoid receptor agonist, with high potency at both the CB1 and CB2 receptors, but low penetration of the blood–brain barrier. This makes LBP-1 peripherally selective, and while it was effective in animal models of neuropathic pain and allodynia, it did not produce cannabinoid-appropriate responding suggestive of central effects, at any dose tested.
JD5037 is an antiobesity drug candidate which acts as a peripherally-restricted cannabinoid inverse agonist at CB1 receptors. It is very selective for the CB1 subtype, with a Ki of 0.35nM, >700-fold higher affinity than it has for CB2 receptors.
5F-AB-FUPPYCA (also known as AZ-037) is a pyrazole-based synthetic cannabinoid that is presumed to be an agonist of the CB1 receptor and has been sold online as a designer drug. It was first detected by the EMCDDA as part of a seizure of 540 g white powder in France in February 2015.
Monlunabant is a peripherally selective cannabinoid receptor 1 inverse agonist, discovered as a β-arrestin-2-biased cannabinoid receptor 1 antagonist by Dr George Kunos, Dr Resat Cinar, and Dr Malliga Iyer at the National Institutes of Health. It was developed as a weight loss drug by Inversago Pharma.
