Psychoplastogens are a group of small molecule drugs that produce rapid and sustained effects on neuronal structure and function, intended to manifest therapeutic benefit after a single administration. [1] [2] Several existing psychoplastogens have been identified and their therapeutic effects demonstrated; several are presently at various stages of development as medications including ketamine, MDMA, scopolamine, and the serotonergic psychedelics, including LSD, psilocin (the active metabolite of psilocybin), DMT, and 5-MeO-DMT. Compounds of this sort are being explored as therapeutics for a variety of brain disorders including depression, addiction, and PTSD. The ability to rapidly promote neuronal changes via mechanisms of neuroplasticity was recently discovered as the common therapeutic activity and mechanism of action. [3]
The term psychoplastogen comes from the Greek roots psych- (mind), -plast (molded), and -gen (producing) and covers a variety of chemotypes and receptor targets. It was coined by David E. Olson in collaboration with Valentina Popescu, both at the University of California, Davis. [3]
The term neuroplastogen is sometimes used as a synonym for psychoplastogen, especially when speaking to the biological substrate rather than the therapeutic.
Psychoplastogens come in a variety of chemotypes and chemical families, but, by definition, are small-molecule drugs. [1] Ketamine has been described as, "the prototypical psychoplastogen". [3]
Psychoplastogens exert their effects by promoting structural and functional neural plasticity through diverse targets including, but not limited to, 5-HT2A, NMDA, and muscarinic receptors. Some are biased agonists. While each compound may have a different receptor binding profile, signaling appears to converge at the tyrosine kinase B (TrkB) and mammalian target of rapamycin (mTOR) pathways. [3] [4] Convergence at TrkB and mTOR parallels that of traditional antidepressants with known efficacies, but with more rapid onset. [5]
Due to their rapid and sustained effects, psychoplastogens could potentially be dosed intermittently. In addition to the neuroplasticity effects, these compounds can have other epiphenomena including sedation, dissociation, and hallucinations. [6]
Psychedelics show complex effects on neuroplasticity and can both promote and inhibit neuroplasticity depending on the circumstances. [7] Single doses of DMT, 5-MeO-DMT, psilocybin, and DOI have been found to produce robust and long-lasting increases in neuroplasticity in animals. [7] Likewise, repeated doses of LSD for 7 days increased neuroplasticity. [7] However, chronic intermittent administration of DMT for several weeks resulted in dendritic spine retraction, suggesting physiological homeostatic compensation in response to overstimulation. [7] In addition, DOI has been found to decrease brain-derived neurotrophic factor (BDNF) levels in the hippocampus. [7] The effects of psychedelics on neuroplasticity appear to be dependent on serotonin 5-HT2A receptor activation, as they are abolished in 5-HT2A receptor knockout mice. [7] Non-hallucinogenic serotonin 5-HT2A receptor agonists, like tabernanthalog and lisuride, have also been found to increase neuroplasticity, and to a magnitude comparable to psychedelics. [7]
In terms of neurogenesis, DOI and LSD showed no impact on hippocampal neurogenesis, while psilocybin and 25I-NBOMe decreased hippocampal neurogenesis. [7] 5-MeO-DMT however has been found to increase hippocampal neurogenesis, and this could be blocked by sigma σ1 receptor antagonists. [7]
Several psychoplastogens have either been approved or are in development for the treatment of a variety of brain disorders associated with neuronal atrophy where neuroplasticity can elicit beneficial effects. [6]
Esketamine, sold under the brand name Spravato and produced by Janssen Pharmaceuticals, was approved by the FDA in March 2019 for the treatment of Treatment-Resistant Depression (TRD) and suicidal ideation. [8] As of 2022, it is the only psychoplastogen approved in the US for the treatment of a neuropsychiatric disorder. [6] Esketamine is the S(+) enantiomer of ketamine and functions as an NMDA receptor antagonist. [9]
Other psychoplastogens that are being investigated in the clinic include:
Psilocybin, also known as 4-phosphoryloxy-N,N-dimethyltryptamine (4-PO-DMT), and formerly sold under the brand name Indocybin, is a naturally occurring psychedelic prodrug compound produced by more than 200 species of fungi. Psilocybin is itself biologically inactive but is quickly converted by the body to psilocin, which has mind-altering effects similar, in some aspects, to those of other classical psychedelics. Effects include euphoria, hallucinations, changes in perception, a distorted sense of time, and perceived spiritual experiences. It can also cause adverse reactions such as nausea and panic attacks.
Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary mental states and a perceived "expansion of consciousness". Also referred to as classic hallucinogens or serotonergic hallucinogens, the term psychedelic is sometimes used more broadly to include various types of hallucinogens, such as those which are atypical or adjacent to psychedelia like salvia and MDMA, respectively.
5-MeO-DMT (5-methoxy-N,N-dimethyltryptamine), also known as O-methylbufotenin or mebufotenin, is a naturally occurring psychedelic of the tryptamine family. It is found in a wide variety of plant species, and is also secreted by the glands of at least one toad species, the Colorado River toad. It may occur naturally in humans as well. Like its close relatives dimethyltryptamine (DMT) and bufotenin (5-HO-DMT), it has been used as an entheogen in South America. Slang terms include five-methoxy, the power, bufo, and toad venom.
Psychedelic therapy refers to the proposed use of psychedelic drugs, such as psilocybin, ayahuasca, LSD, psilocin, mescaline (peyote), DMT, 5-MeO-DMT, Ibogaine, MDMA, to treat mental disorders. As of 2021, psychedelic drugs are controlled substances in most countries and psychedelic therapy is not legally available outside clinical trials, with some exceptions.
Psilocin, also known as 4-hydroxy-N,N-dimethyltryptamine (4-OH-DMT), is a substituted tryptamine alkaloid and a serotonergic psychedelic. 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 serotonin 5-HT2A receptors, psilocin's psychedelic effects are directly correlated with the drug's occupancy at these receptor sites. The subjective mind-altering effects of psilocin are highly variable and are said to resemble those of lysergic acid diethylamide (LSD) and N,N-dimethyltryptamine (DMT).
Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences apparent lasting or persistent visual hallucinations or perceptual distortions after using drugs, including but not limited to psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being designated as a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.
The Beckley Foundation is a UK-based think tank and UN-accredited NGO, dedicated to activating global drug policy reform and initiating scientific research into psychoactive substances. The foundation is a charitable trust which collaborates with leading scientific and political institutions worldwide to design and develop research and global policy initiatives. It also investigates consciousness and its modulation from a multidisciplinary perspective, working in collaboration with scientists. The foundation is based at Beckley Park near Oxford, United Kingdom. It was founded in 1998, and is directed by Amanda Feilding, Countess of Wemyss.
2-Bromo-LSD, also known as BOL-148 or as bromolysergide, is a derivative of lysergic acid invented by Albert Hofmann, as part of the original research from which the closely related compound LSD was also derived. It is a non-hallucinogenic serotonin 5-HT2A receptor partial agonist, as well as acting at other targets, with psychoplastogenic and antidepressant-like effects in animals.
ALTO-100, previously known as NSI-189, is a drug described as a hippocampal neurogenesis stimulant and indirect brain-derived neurotrophic factor (BDNF) modulator which is under development for the treatment of major depressive disorder (MDD), bipolar depression, and post-traumatic stress disorder (PTSD). There has also been interest in ALTO-100 for possible treatment of cognitive impairment and neurodegeneration. It is taken by mouth.
MDMA-assisted psychotherapy is the use of prescribed doses of MDMA as an adjunct to psychotherapy sessions. Research suggests that MDMA-assisted psychotherapy for post-traumatic stress disorder (PTSD), including complex PTSD (C-PTSD), might improve treatment effectiveness. In 2017, a Phase II clinical trial led to a breakthrough therapy designation by the U.S. Food and Drug Administration (FDA) for potential use as a treatment for PTSD.
DLX-001, also known as AAZ-A-154 or as (R)-5-methoxy-N,N-dimethyl-α-methylisotryptamine, is a novel isotryptamine derivative which acts as a serotonin 5-HT2A receptor agonist discovered and synthesized by the lab of Professor David E. Olson at the University of California, Davis. It is being developed for the treatment of major depressive disorder and other central nervous system disorders.
Mind Medicine (MindMed) Inc., doing business as MindMed, is a New York-based biotechnology company that is currently developing clinical and therapeutic applications for psychedelic and, more broadly, psychoplastogenic drugs.
Delix Therapeutics is an American biotech company based in Boston, Massachusetts. The company develops novel neuroplasticity-promoting therapeutics for central nervous system (CNS) diseases such as depression and post-traumatic stress disorder (PTSD). It was co-founded in 2019 by David E. Olson and Nick Haft.
Psychedelic treatments for trauma-related disorders are the use of psychedelic substances, either alone or used in conjunction with psychotherapy, to treat trauma-related disorders. Trauma-related disorders, such as post-traumatic stress disorder (PTSD), have a lifetime prevalence of around 8% in the US population. However, even though trauma-related disorders can hinder the everyday life of individuals with them, less than 50% of patients who meet criteria for PTSD diagnosis receive proper treatment. Psychotherapy is an effective treatment for trauma-related disorders. A meta-analysis of treatment outcomes has shown that 67% of patients who completed treatment for PTSD no longer met diagnostic criteria for PTSD. For those seeking evidence-based psychotherapy treatment, it is estimated that 22-24% will drop out of their treatment. In addition to psychotherapy, pharmacotherapy (medication) is an option for treating PTSD; however, research has found that pharmacotherapy is only effective for about 59% of patients. Although both forms of treatment are effective for many patients, high dropout rates of psychotherapy and treatment-resistant forms of PTSD have led to increased research in other possible forms of treatment. One such form is the use of psychedelics.
A trip killer, or hallucinogen antidote, is a drug that aborts or reduces the effects of a hallucinogenic drug experience. As there are different types of hallucinogens that work in different ways, there are different types of trip killers. They can completely block or reduce the effects of hallucinogens or they can simply provide anxiety relief and sedation. Examples of trip killers, in the case of serotonergic psychedelics, include serotonin receptor antagonists, like antipsychotics and certain antidepressants, and benzodiazepines. Trip killers are sometimes used by recreational psychedelic users as a form of harm reduction to manage so-called bad trips, for instance difficult experiences with prominent anxiety. They can also be used clinically to manage effects of hallucinogens, like anxiety and psychomotor agitation, for instance in the emergency department.
ITI-1549 is a putatively non-hallucinogenic serotonin 5-HT2A receptor agonist which is under development for the treatment of mood disorders and other psychiatric disorders. In addition to acting at the serotonin 5-HT2A receptor, it is also an antagonist of the serotonin 5-HT2B receptor and an agonist of the serotonin 5-HT2C receptor. The drug's route of administration has not been specified.
BMB-202 is a serotonin 5-HT2A receptor agonist and psychedelic hallucinogen which is under development for the treatment of depressive disorders and post-traumatic stress disorder (PTSD). It is taken by mouth. However, BMB-202 has also been evaluated by injection in preclinical studies.
isoDMT, also known as N,N-dimethylisotryptamine, is a putatively non-hallucinogenic serotonin 5-HT2A receptor agonist and psychoplastogen of the isotryptamine group. It is the isotryptamine homologue of dimethyltryptamine (DMT), a more well-known serotonergic psychedelic of the tryptamine family, and represents a small structural modification of DMT.