Psychedelic Compounds

Executive summary: 2C-x denotes a family of synthetic phenethylamine psychedelics defined by a 2,5-dimethoxyphenethylamine scaffold with a variable 4-position substituent (“X”). Across the class, the best-supported core mechanism is serotonergic psychedelic activity mediated primarily through 5-HT2A receptor signalling, with many compounds also showing functional activity at 5-HT2C and (importantly for safety discussions) 5-HT2B. 2C-B (4-bromo-2,5-dimethoxyphenethylamine) functions as the empirical archetype because it dominates the modern controlled-human literature relative to other 2C analogues. Clinically, 2C-x remains a “mechanism-rich, evidence-thin” space. The human evidence base is concentrated in small mechanistic studies: (i) early non-controlled observational work assessing acute subjective and physiological effects and (saliva/oral-fluid) pharmacokinetics; (ii) controlled, within-subject, placebo-controlled comparisons to psilocybin in healthy volunteers; and (iii) the beginning of biomarker-enabled Phase I crossover work that explicitly benchmarks 2C-B against MDMA and psilocybin and includes plasma oxytocin and BDNF endpoints. This makes 2C-x scientifically legible (mechanistically comparable) but not yet clinically “actionable” for patient indications in the way the psilocybin and MDMA programmes are. Regulatorily, 2C-B is tightly controlled: it is Schedule I under US federal law (listed as 4-bromo-2,5-dimethoxyphenethylamine) and has been internationally controlled since 2001 via placement in Schedule II of the 1971 Convention on Psychotropic Substances. In the UK it is Class A and placed in Schedule 1 of the Misuse of Drugs Regulations, reflecting “no recognised therapeutic use” under current UK frameworks. Canada lists 2C-B in Schedule III, and Australia lists it in Schedule 9 of the Poisons Standard. This landscape has two consequences for 2C-x: (i) research remains licence- and infrastructure-intensive; (ii) commercial strategies that depend on routine prescribing are structurally disadvantaged relative to rescheduled or late-stage agents. Why attention is warranted now: the broader regulatory and commercial “centre of gravity” for serotonergic psychedelics is shifting. On 17 February 2026, Compass Pathways reported its second positive Phase III trial for synthetic psilocybin in treatment-resistant depression, including quantified Week 6 MADRS separations, rapid-onset claims, and an intention to pursue an NDA on a rolling basis. In parallel, a German-led European consortium (named publicly by MIND Foundation as including SPRIN-D, Usona, and ZI Mannheim) describes a planned Phase III/HTA reimbursement-oriented trial (“DiMension”) that remains in preparation and is explicitly seeking public and philanthropic funding. Against that backdrop, the 2C-x field has simultaneously matured methodologically: biomarker panels (oxytocin/BDNF), validated PK methods in plasma, and 7T resting-state fMRI mapping for 2C-B have appeared or progressed. Taken together, the moment is scientifically timely (tools exist to characterise 2C-x properly) but translationally constrained (pathways to near-term clinical adoption remain uncertain).

A potent tryptamine psychedelic known for profound mystical experiences, currently under clinical investigation for TRD and anxiety.

Ayahuasca is a botanical decoction traditionally made from the Banisteriopsis caapi vine and Psychotria viridis leaves. Its active ingredient is DMT (N,N-dimethyltryptamine), a potent 5-HT2A agonist, combined with β-carboline MAO-A inhibitors (harmine, harmaline, tetrahydroharmine) from caapi【28†L459-L464】【31†L1-L4】. The MAO inhibitors prevent gut breakdown of DMT, rendering it orally active【30†L200-L209】【31†L1-L4】. Onset is typically 30–60 minutes after ingestion, with peak effects around 1–2 hours and total duration ~3–6 hours【28†L466-L474】【38†L502-L506】. Acute effects include intense hallucinations, emotional catharsis and the characteristic purging (nausea/vomiting) seen in ceremonial contexts【28†L466-L474】. Ayahuasca’s mechanism overlaps with other classic psychedelics: DMT is a full agonist at 5-HT2A and 5-HT2C receptors【10†L314-L322】 (and also binds 5-HT1A and sigma-1 sites【43†L232-L239】), while the harmala alkaloids are reversible MAO-A inhibitors【34†L253-L259】. In neuroimaging, ayahuasca acutely suppresses default-mode network activity (e.g. precuneus, medial PFC)【34†L225-L234】 and increases limbic and visual cortex perfusion, mirroring the “reset” profile of other psychedelics. Post-dose, biomarkers of neuroplasticity rise: for example, plasma BDNF is significantly higher 48h after ayahuasca (correlating with symptom improvement)【4†L388-L392】, and animal studies show DMT stimulates hippocampal neurogenesis【43†L232-L239】. Clinical interest in ayahuasca has surged due to its rapid-acting antidepressant and anti-addiction potential. For example, a 2019 Phase II placebo-controlled RCT (Palhano-Fontes et al.) found that a single ayahuasca dose produced large reductions in depression scores (MADRS) in treatment-resistant depression (Cohen’s d≈1.49 at 7 days, p<0.0001)【27†L403-L410】. Response rates at one week were 64% on ayahuasca versus 27% on placebo【27†L403-L410】. Likewise, Erritzoe et al. (2026) reported a Phase IIa RCT of IV DMT (ayahuasca’s active alkaloid) in major depression: one dose yielded a mean MADRS reduction of ~−21 points by day 7 (mean difference vs placebo ≈−10.75, p=0.002, d=1.09)【24†L274-L281】. Observational studies of ritual use echo these findings: large cohorts report sustained improvements in mood, anxiety and substance use up to 6+ months after ceremony【2†L1-L4】【68†L1877-L1881】. No regulated therapeutic use is yet approved, but the resurgence of modern trials (and even biotech formulations of DMT) reflects unprecedented momentum. Note that DMT itself is Schedule I under UN/US law【60†L138-L142】, so ayahuasca is illegal in many countries (Class A in the UK【64†L290-L298】) except where traditional use is protected. Brazil explicitly exempted ayahuasca for religious use in 1987【28†L453-L459】, and US/Canadian courts have granted church exemptions (UDV 2006, Santo Daime 2009)【64†L304-L312】. In sum, ayahuasca’s unique pharmacology and promising trial results have attracted intense research and investment interest at this juncture. Key Findings for Researchers and Investors: - A single ayahuasca dose produced robust antidepressant effects in an RCT: Palhano-Fontes et al. (2019) saw significantly larger MADRS reductions than placebo (day-7 Cohen’s d≈1.49, p<0.0001)【27†L403-L410】, with response in 64% of patients vs 27% on placebo by day 7【27†L403-L410】. - Erritzoe et al. (2026, Imperial College/Helus Pharma) found one IV infusion of DMT caused rapid symptom relief in depression: by day 7 the mean MADRS difference vs placebo was ~–10.75 points (p=0.002, d=1.09)【24†L274-L281】, with ~85% of subjects responding. - Naturalistic and cohort data indicate reductions in addictive behaviors: e.g., a six-month follow-up of an Indigenous Canadian cohort showed marked drops in alcohol, tobacco and cocaine use after ayahuasca ceremonies【68†L1877-L1881】. - Neuroimaging evidence shows ayahuasca acutely lowers default-mode network activity (precuneus/medial PFC)【34†L225-L234】, consistent with other psychedelics’ “entropy” effect. - Neuroplasticity biomarkers rise post-treatment: e.g. de Almeida et al. report elevated BDNF at 48h after ayahuasca (correlated with mood improvement)【4†L388-L392】, and preclinical work shows DMT induces hippocampal neurogenesis (via σ1-receptors)【43†L232-L239】. - Safety profile in trials is benign: most trials report only transient GI effects and mild sympathomimetic signs【70†L426-L434】. No serious organ toxicity or long-term psychiatric sequelae have been seen. In Palhano-Fontes’s study, 100% experienced nausea/vomiting but all remained physically safe【69†L7-L10】. Like other psychedelics, ayahuasca carries no evidence of dependence. However, its MAOI content means dangerous interactions with SSRIs or stimulants are possible【70†L411-L418】, so strict screening and supportive set-and-setting are standard in therapeutic contexts.

A powerful, short-acting tryptamine psychedelic found in many botanical sources, known for rapid onset and intense subjective experiences.

Esketamine is the (S)-enantiomer of ketamine, a fully synthetic arylcyclohexylamine with dissociative anaesthetic properties. At clinically relevant concentrations it behaves primarily as a non-competitive antagonist at the N-methyl-D-aspartate (NMDA) receptor complex, although ketamine-class compounds show broader pharmacology (including measurable affinity for other receptor systems and transporters). The antidepressant mechanism of intranasal esketamine is not established; the dominant working model links transient NMDA blockade to downstream glutamatergic and synaptic-plasticity cascades rather than direct monoamine reuptake inhibition. citeturn20view1turn10search29turn22search24turn8view1 In clinical and commercial practice, esketamine is now largely synonymous with Spravato, a single-use intranasal device delivering 28 mg per device and dosed intermittently under supervision. In the United States, the current label authorises intranasal esketamine for adults with treatment-resistant depression (TRD) either as monotherapy or in conjunction with an oral antidepressant, and for depressive symptoms in adults with major depressive disorder (MDD) with acute suicidal ideation or behaviour in conjunction with an oral antidepressant and comprehensive standard of care. These indications sit alongside a restrictive Risk Evaluation and Mitigation Strategy (REMS) that prohibits home dispensing and requires post-dose monitoring in a certified healthcare setting. citeturn2view0turn34view1turn31view3turn34view3 In the European Union, marketing authorisation similarly positions intranasal esketamine as a psychiatrist-led intervention requiring supervised self-administration and post-dose observation; the EU label includes TRD (in combination with an SSRI or SNRI) and an acute short-term indication for rapid reduction of depressive symptoms in a moderate-to-severe MDD episode that, in clinical judgement, constitutes a psychiatric emergency. In the UK, the Summary of Product Characteristics aligns with use in combination with an SSRI or SNRI for TRD, but NICE has not recommended esketamine nasal spray within its technology appraisal scope, which has been a material constraint on NHS commissioning. citeturn20view0turn12search0turn12search6 Esketamine is particularly salient in 2026 because the field has moved from small, investigator-led ketamine infusion experiments to regulated, scalable service models with defined dosing schedules, formalised safety governance, and accumulating long-term exposure data. The 2025 US label update permitting TRD monotherapy has the potential to broaden eligibility and simplify pathways for patients who do not tolerate, or do not accept, ongoing oral antidepressants. Commercially, Johnson & Johnson reports continued rapid growth, with Spravato 2025 worldwide sales of $1,696m (Q4: $503m), indicating that payers and providers are increasingly willing to operationalise and reimburse a rapid-acting, glutamatergic antidepressant model despite the delivery frictions and controlled-substance safeguards. In parallel, UK policy attention to ketamine-related harms has intensified, underscoring why supervised, risk-managed delivery has become central to esketamine’s value proposition. citeturn20view6turn30view2turn13view1

A unique indole alkaloid with complex pharmacology, investigated primarily for its capacity to interrupt substance use disorders and withdrawal.

A dissociative anesthetic with rapid-acting antidepressant properties, widely used in clinical settings for mood and pain disorders.

Lysergic acid diethylamide (LSD) is a classic psychedelic in the ergoline (lysergamide) chemical family, originally synthesised as a semi-synthetic derivative of lysergic acid. Its acute psychoactive effects are mediated primarily via serotonin 5‑HT2A receptor agonism, with a broader “receptorome” that includes other serotonergic sites and functionally relevant dopaminergic and adrenergic interactions; this broader binding profile differentiates LSD from comparatively narrower tryptamine psychedelics such as psilocin. citeturn22search8turn22search2turn22search9 A central translational feature is its very high potency (effective doses in the microgram range) and long duration of action, with controlled human pharmacokinetic work showing peak subjective effects roughly 2–3 hours after oral dosing and an average acute subjective duration around 8–9 hours (with wide interindividual range). citeturn22search8turn38search0 Clinically, LSD has shifted from being a predominantly historical psychiatric research tool to a compound with credible, modern randomised evidence in anxiety disorders and an active commercial development programme. In a landmark modern pilot, entity["people","Gasser","lsd anxiety trial lead"] and colleagues conducted a double-blind, randomised, active-placebo-controlled study in patients with anxiety associated with life‑threatening illness, reporting large effect sizes on anxiety measures at 2 months and sustained improvements at 12 months, without treatment-related serious adverse events. citeturn34view0 More recently, entity["people","Holze","lsd anxiety trial lead"] and colleagues reported Phase II placebo-controlled data for LSD-assisted therapy in anxiety, including follow-up analyses indicating sustained symptom reductions over extended time horizons. citeturn32search15turn36view0 In parallel, an oral pharmaceutical formulation of lysergide D‑tartrate (MM120) has produced Phase IIb dose-finding evidence in generalised anxiety disorder (GAD) with clinically meaningful reductions versus placebo at higher doses and a tolerability profile consistent with expected acute psychedelic effects. citeturn37view0 Regulatory status remains a core constraint. LSD is tightly controlled internationally and in most major jurisdictions, limiting use primarily to licensed research. citeturn19view1turn11search10turn10view0turn8search6turn15view0 However, the current moment is unusually consequential: a high-visibility Phase IIb psychiatric trial published in a leading medical journal, combined with a sponsor-reported entity["organization","US Food and Drug Administration","federal health regulator, us"] Breakthrough Therapy Designation for MM120 in GAD, has accelerated expectations of a near-term pivotal programme and forced the field to confront practical questions of scalability, blinding integrity, and safety governance in real-world clinical delivery. citeturn37view0turn3search5turn31search1 Attention is warranted because the scientific and translational bottlenecks around LSD are now being addressed directly. Mechanistically, modern imaging work has moved beyond coarse “hallucination” narratives towards network-level models (including altered cortico-striato-thalamo-cortical signalling and changes in functional integration and hierarchy). citeturn30search7turn5search2turn0search3 Practically, the historical objection that LSD “lasts too long” is being tackled via pharmacological modulation (e.g., post-dose 5‑HT2A antagonism with ketanserin markedly shortening subjective duration) and via industrial formulation/IP strategies aimed at controllability and clinic throughput. citeturn31search2turn4search4

MDMA (3,4‑methylenedioxymethamphetamine; proposed INN: midomafetamine) is a fully synthetic, ring‑substituted amphetamine (phenethylamine family) originally synthesised at entity["company","Merck","darmstadt, germany"] in 1912 as an intermediate in other medicinal chemistry work. In contemporary neuropsychopharmacology it is classified as an entactogen/empathogen rather than a classic psychedelic, because its acute subjective and behavioural effects are dominated by monoaminergic release rather than primary 5‑HT2A agonism. At the synapse, MDMA is transported by SERT (and to a lesser extent NET/DAT), reverses transporter flux, and mobilises vesicular monoamines via VMAT2, producing substantial increases in extracellular serotonin alongside measurable increases in noradrenaline and dopamine. In controlled human studies this pharmacology maps onto heightened positive mood, affiliative/prosocial effects and reduced threat responsivity, with comparatively limited perceptual disturbance and typically no frank hallucinosis at clinical‑range doses. citeturn31search0turn31search8turn23view0turn23view2turn27search3 MDMA’s near‑term clinical significance centres on its use as a pharmacological catalyst for intensive, manualised psychotherapy in post‑traumatic stress disorder (PTSD). Across two pivotal Phase III, multi‑site, randomised, double‑blind, placebo‑controlled trials (MAPP1: NCT03537014; MAPP2: NCT04077437), MDMA‑assisted therapy produced larger reductions in clinician‑rated PTSD severity (CAPS‑5) than identical psychotherapy with placebo, with moderate‑to‑large between‑group effect sizes (d=0.91 in MAPP1; d=0.7 in MAPP2) and parallel improvements in functional impairment (Sheehan Disability Scale). The adverse‑event profile in these trials was dominated by transient sympathomimetic and somatic effects (e.g., blood pressure/heart‑rate increases, jaw tension, nausea, sweating), with no deaths reported. citeturn21view0turn21view1turn3view2 In 2024, the regulatory narrative changed materially. The entity["organization","FDA","us medicines regulator"]’s entity["organization","PDAC","fda advisory committee"] voted 9–2 that the available data did not demonstrate effectiveness for PTSD and 10–1 that benefits did not outweigh risks even with a proposed Risk Evaluation and Mitigation Strategy (REMS), citing concerns including functional unblinding/expectancy effects, incomplete safety characterisation (including for abuse‑relevant events), and uncertainty regarding durability. The FDA subsequently issued a Complete Response Letter for NDA 215455 (midomafetamine capsules plus assisted therapy), declining approval and requesting, in effect, an additional well‑controlled trial design that better captures abuse‑relevant events, durability beyond the Week‑18 endpoint, and generalisability to routine PTSD populations. citeturn20view2turn16view0turn16view1turn16view2 The sponsor ecosystem has also undergone rapid organisational change. entity["organization","MAPS","psychedelic research nonprofit"]’ commercial subsidiary entity["company","MAPS PBC","subsidiary of maps"] rebranded to entity["company","Lykos Therapeutics","psychedelic drug developer"] in January 2024 alongside an oversubscribed financing reported as >$100m, and following the FDA’s 2024 Complete Response Letter and subsequent restructuring it has been reported to be rebranding again as entity["company","Resilient Pharmaceuticals","psychedelic drug developer"]. Meanwhile, peer‑reviewed Phase II pooled analyses and long‑term follow‑up publications that historically underpinned confidence in durability have been formally retracted by their journal editors due to undisclosed protocol violations at a study site, sharpening regulator and investor focus on governance, documentation, and bias‑resistant trial design. citeturn2search4turn2search0turn0news43turn2news41turn2search25turn33view0turn33view1

A naturally occurring phenethylamine psychedelic found in certain cacti, investigated for its role in religious practice and psychiatric research.

Pharmacological details and clinical history for this compound are currently being indexed.

Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) is a naturally occurring substituted tryptamine produced by numerous fungal species, and is also manufactured as a purified synthetic active pharmaceutical ingredient for clinical research and drug development. In humans it acts primarily as a prodrug: it is rapidly dephosphorylated (notably by alkaline phosphatases) to psilocin (4-hydroxy-N,N-dimethyltryptamine), the pharmacologically active compound. Psilocin’s acute psychoactive effects are driven predominantly by agonism at the serotonin 5-HT2A receptor, with meaningful engagement of other serotonergic targets that shape overall phenomenology and downstream neurobiological signalling. Clinically, psilocybin has moved from proof-of-concept psychiatry into late-stage development as a drug-plus-psychological-support intervention. Randomised controlled trials in major depressive disorder (MDD) and treatment-resistant depression (TRD) show that one or two supervised sessions can produce rapid reductions in depressive symptoms and functional impairment, with durability extending well beyond the drug’s pharmacokinetic presence, suggesting that the therapeutic mechanism is not limited to transient receptor stimulation. The clinical and regulatory landscape shifted materially in February 2026, when COMPASS Pathways reported that both of its Phase III TRD trials (COMP005 and COMP006) met their primary endpoints on the Montgomery–Åsberg Depression Rating Scale (MADRS), and stated an intention to engage the FDA on a rolling submission with the goal of filing an NDA in Q4 2026. In parallel, access pathways outside conventional marketing authorisation have expanded: Australia permits psychiatrist prescribing under a controlled framework despite the absence of a TGA-approved psilocybin product; Germany has implemented the European Union’s first psilocybin Compassionate Use Programme for TRD at two specialist centres; and US state-level “regulated access” models (notably Oregon and Colorado) are generating real-world implementation data under non-medical service frameworks. Psilocybin is particularly significant right now because the field is transitioning from “does it work?” to “how can it be deployed safely, reproducibly, and at scale?”. The limiting factors are increasingly operational: therapist training, site logistics for 6–8 hour dosing days, careful risk stratification for suicidality and bipolar-spectrum vulnerability, and credible adverse-event surveillance. This is one driver behind a wave of ‘second-generation’ approaches (for example deuterated psilocin/psilocybin analogues such as CYB003) that aim to preserve clinical benefit while reducing duration, variability, and service burden—although it remains uncertain how reliably such molecular modifications translate into superior real-world effectiveness and safety.