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Author: kodiac

Mucuna pruriens

Plain-language summaryIntrigue 58 / 100

Mucuna pruriens (velvet bean) is a tropical legume with high concentrations of L-DOPA, the direct precursor to dopamine. Used in Ayurveda and as a natural Parkinson disease aid. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

26/100

Natural L-DOPA source with thin pharmacokinetic differentiation and limited bench utility

Look, Mucuna pruriens is essentially a vehicle for L-DOPA delivery, and L-DOPA has been a therapeutic compound since the 1960s. The mechanism isn’t novel – dopamine precursor supplementation is textbook neurochemistry. What makes Mucuna interesting at all is the question of whether the plant matrix changes how that L-DOPA behaves in practice, and honestly, that question is still mostly unanswered.

The small Parkinson trials comparing Mucuna to carbidopa-levodopa are real data points. A handful of studies, primarily from Tharayil et al. and a few Indian groups, found broadly similar motor benefit at equivalent L-DOPA content. Some reports suggest slower onset and potentially longer duration of effect compared to standard formulations. If that pharmacokinetic story holds up it would be genuinely interesting – but the evidence base is thin and uncontrolled. Trials are underpowered, and the variability in L-DOPA content across preparations makes dose-matching unreliable enough to compromise any clean mechanistic conclusion.

What we dont find compelling is the bench research angle. An investigator studying dopaminergic pharmacology, Parkinson pathology, or L-DOPA-induced dyskinesia is going to reach for pharmaceutical-grade levodopa every time. The reproducibility problems with botanical extracts – lot-to-lot variation in L-DOPA content, presence of uncharacterized alkaloids, NADH and putative monoamine oxidase activity from co-extractants – are liabilities in a controlled research context, not assets. The “other constituents” story gets cited occasionally but no specific pharmacologically active fractions have been rigorously characterized or isolated in replicated work.

From a novelty standpoint, Mucuna’s L-DOPA content was characterized in the 1930s and the Ayurvedic use predates that by centuries. Thats not a knock on its own – old compounds can find new relevance – but there isnt a new mechanism story here, no surprising receptor interaction, no novel target class that would organize a research program specifically around this plant.

We think the only genuinely interesting research question Mucuna opens up is the PK comparison to synthetic formulations, and specifically whether the natural matrix affects tolerability or dyskinesia burden in PD management. That question has clinical relevance and is underserved in the literature. At bench scale, though, utility is limited. Researchers interested in L-DOPA pharmacology have better-controlled tools; researchers interested in botanical ethnopharmacology have more scientifically active targets. Mucuna sits in an awkward middle ground – a well-understood drug dressed as an herb, without the quality control of the former or the novelty of the latter.

Novelty

18

Mechanism promise

20

In-category differentiation

20

Evidence quality

35

Translational signal

45

Research bench value

20

Rationale Mucuna pruriens is fundamentally a botanical L-DOPA delivery system built around a 60-year-old therapeutic mechanism; the small comparative PD trials demonstrate equivalence to synthetic formulations rather than superiority, and lot-to-lot variability in L-DOPA content makes it an unreliable research tool compared to pharmaceutical-grade levodopa.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Velvet bean / L-DOPA source

A tropical bean traditionally used in Ayurveda for Parkinsonian symptoms, the natural source of L-DOPA used as standardized extracts containing 15 to 50 percent L-DOPA.

Abstract

Mucuna pruriens (velvet bean, kapikacchu) is a tropical legume used in Ayurvedic medicine for Parkinsonism, infertility, and “vata” disorders. The seeds contain L-DOPA (L-3,4-dihydroxyphenylalanine) at 5 to 7 percent of seed weight, the highest natural concentration known. Standardized extracts contain 15 to 50 percent L-DOPA depending on processing. The compound has been compared with synthetic L-DOPA in small Parkinson disease trials with broadly similar efficacy at equivalent L-DOPA content; some reports suggest slower onset and longer duration than carbidopa-levodopa formulations, possibly due to other constituents that influence pharmacokinetics. The compound is sold as a dietary supplement; doses are typically 500 to 2000 mg of extract standardized to 15 to 50 percent L-DOPA. Use for Parkinson disease should be supervised; the supplement market includes preparations with insufficient L-DOPA content for therapeutic use and potential misuse for non-Parkinson recreational dopaminergic effects.

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The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
CX-717

Plain-language summaryIntrigue 52 / 100

CX-717 is a methylsulfonyl benzoxazine ampakine investigated for ADHD and respiratory depression. The respiratory application was based on AMPA-mediated stimulation of central respiratory networks. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished, active research

49/100

The furthest-advanced CX-series ampakine, with real military human data but stalled Phase 2 development

Look, CX-717 is probably the most serious compound in the CX-series to ever see human volunteers, and that matters. Most ampakines from the Cortex Pharmaceuticals pipeline stayed in rodents or at best healthy volunteer Phase 1 work. CX-717 actually made it into DoD-funded sleep deprivation trials, and the published data from those studies is real: modest but reproducible improvements in vigilance and working memory during 24-72 hour sleep deprivation windows. Turner and colleagues published those results and they held up. Thats a bar that most research chemicals in this space never clear.

The mechanism here is AMPA receptor positive allosteric modulation. Specifically, CX-717 slows AMPA receptor deactivation and desensitization, which has downstream effects on synaptic strengthening, BDNF expression, and arousal-relevant circuitry. The benzoxazine class was specifically engineered to avoid the respiratory depression issues that dogged earlier ampakines like CX-516 and CX-614. That engineering worked, and the cleaner safety profile is part of why this one made it furthest in clinical development. AMPA PAM is not a new idea in 2025, but its still a genuinely interesting mechanism for cognitive enhancement and one the field hasn’t fully cracked at the translational level.

Where things get complicated is in the so-what question. CX-717 ran Phase 2 work in adult ADHD and the results were partial at best. The compound never advanced to Phase 3 or FDA review. That stall tells you something: the effect sizes weren’t compelling enough to justify continued development at commercial scale, or there were tolerability issues at higher doses that the low-impact class designation didn’t fully solve. We don’t know the full picture because incomplete pharma clinical data is rarely published cleanly.

As a bench tool, we think CX-717 has real but specialized utility. If you’re investigating AMPA-mediated plasticity, cognitive resilience under sleep debt, or BDNF upregulation pathways, having a compound with published human PK and real Phase 2 dose data is actually useful. You’re not working blind on the translational side. But if you want to study AMPA biology more broadly, newer PAMs with better characterized profiles exist and the competitive landscape has shifted since the early Cortex Pharmaceuticals era.

Honestly, the score here reflects a compound that showed genuine promise and cleared real bars that most research chemicals never approach, but ultimately hit a ceiling. The human signal is there; the effect size isn’t paradigm-defining. It sits comfortably in the worth-knowing, worth-studying-in-the-right-context zone rather than the immediately-prioritize-this tier.

Novelty

40

Mechanism promise

60

In-category differentiation

52

Evidence quality

50

Translational signal

40

Research bench value

48

Rationale CX-717 earns credit for being the most clinically advanced benzoxazine ampakine, with published DoD sleep-deprivation human data and Phase 2 ADHD work that most CX-series compounds never approached; however, the stalled development arc, modest effect sizes in published studies, and the maturity of the AMPA PAM class hold it solidly in established-active territory rather than novel-frontier.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Methylsulfonyl benzoxazine ampakine

A methylsulfonyl benzoxazine ampakine that advanced furthest of the CX-series in human trials, including military sleep deprivation studies.

Abstract

CX-717 (1-(N-methyl-N-methylsulfonyl-aminobenzoyl)pyrrolidine; CAS 412960-03-7) is a methylsulfonyl benzoxazine ampakine developed at Cortex Pharmaceuticals that advanced further in human trials than other CX-series compounds. The compound was studied by DARPA and the Department of Defense for cognitive performance maintenance during sleep deprivation in military personnel; published results showed modest but reproducible improvements in vigilance and working memory performance during 24- to 72-hour sleep deprivation. CX-717 was also studied for adult ADHD with partial Phase 2 results. The compound did not advance to FDA approval. Pharmacokinetics: plasma half-life approximately 3 to 4 hours; oral bioavailability adequate. The compound is sold as a research chemical with limited availability.

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The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Sembragiline

Plain-language summaryIntrigue 40 / 100

Sembragiline is an investigational selective reversible MAO-B inhibitor from Roche and EVOTEC, originally developed as a possible Alzheimer disease treatment. The rationale was elegant: MAO-B is upregulated in the reactive astrocytes that surround amyloid plaques in Alzheimer brain tissue, and that upregulation contributes to oxidative damage. Selectively shutting it down with a reversible blocker should, in theory, reduce that damage without interfering with normal brain function. The Phase 2 MAyflOwer RoAD trial in mild-to-moderate Alzheimer disease failed to show clinical benefit, however, and development was halted. The compound retains research value as a mechanistic probe but has no clinical future. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundNiche research probe

38/100

Failed Alzheimer phase 2 candidate with residual tool value as a clean reversible selective MAO-B probe

Look, sembragiline is a clean story about a drug that asked the right question and got the wrong answer. The mechanistic rationale was genuinely reasonable: MAO-B is upregulated in reactive astrocytes in Alzheimer brain tissue, it contributes to oxidative stress, and there’s a plausible chain from that to amyloid pathology. Roche and Evotec built a highly selective reversible inhibitor to probe this, with a selectivity ratio above 1000:1 over MAO-A. Thats pharmacologically elegant. The reversibility angle was the key idea: unlike selegiline or rasagiline, which ablate MAO-B activity for the life of the enzyme, sembragiline gives you tunable, titratable inhibition without committing to an irreversible mechanism.

Then the MAyflOwer RoAD trial happened. Phase 2, n=542, mild-to-moderate Alzheimer disease, 52 weeks. No significant slowing of cognitive decline. Development halted. The compound didn’t fail because of bad pharmacology; it failed because the hypothesis didn’t translate. MAO-B inhibition in Alzheimer’s turned out not to be a sufficient lever on disease progression, at least not at the population level or the dose ranges tested.

What’s left is a genuinely useful but narrow tool compound. Academic neuroscience groups use sembragiline specifically because of what it is: the reference reversible selective MAO-B inhibitor with the cleanest selectivity profile available. If you’re studying MAO-B’s contribution to neuroinflammatory signaling, dopamine metabolism in Parkinson’s-adjacent biology, or oxidative stress dynamics in reactive astrocytes, you need something that lets you toggle the enzyme without the complication of irreversibility. Safinamide is also reversible and approved, but it carries a sodium channel component that complicates clean mechanistic attribution. Sembragiline is cleaner for this purpose.

We think the bench value is real but specific. If your research program touches MAO-B biology directly, this is worth having and using. If it doesn’t, theres not much here. The failed phase 2 is decisive for the Alzheimer’s indication, and the compound has no obvious pivot to another indication with real human signal. Novelty is modest: MAO-B inhibition is a mature mechanistic class, and reversible selectivity within it is a refinement, not a new direction.

Honestly, what keeps this at 38 is arithmetic. The mechanism class is established, the clinical hypothesis was falsified, and the tool value is specific enough to matter only to a subset of neuroscience programs. Sembragiline ran a clean trial and learned something real. That’s exactly what research should do. It just doesn’t make the compound a priority target for most investigators, and the score should say so plainly.

Novelty

32

Mechanism promise

35

In-category differentiation

48

Evidence quality

44

Translational signal

22

Research bench value

55

Rationale Sembragiline’s mechanistic rationale was scientifically sound but the MAyflOwer RoAD trial (n=542, 52 weeks) produced a clear null result, decisively closing the AD indication. Its remaining value is as the reference reversible, highly selective MAO-B inhibitor (greater than 1000:1 over MAO-A) for academic studies of MAO-B’s contribution to neurodegeneration, but that utility is narrow enough that bench_value can’t rescue the overall from niche-probe territory.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Selective reversible MAO-B inhibitor (investigational)

A selective reversible MAO-B inhibitor investigated for Alzheimer disease; failed phase 2 efficacy.

Abstract

Sembragiline (EVT-302, RG1577; molecular formula C19H22FN3O; molecular weight 327.40) is a selective reversible MAO-B inhibitor developed at Roche and EVOTEC as a candidate for Alzheimer disease. The mechanistic rationale: MAO-B is upregulated in reactive astrocytes in Alzheimer brain tissue, contributing to oxidative stress and amyloid pathology; selective reversible inhibition might reduce this contribution without the irreversible enzyme abolition of selegiline or rasagiline. Phase 2 MAyflOwer RoAD trial in mild-to-moderate Alzheimer disease (n=542) failed to show significant slowing of cognitive decline at 52 weeks; development was halted. The compound retains research utility as a clean tool for selective reversible MAO-B inhibition (selectivity ratio greater than 1000:1 over MAO-A) and is used in academic studies of MAO-B’s role in neurodegeneration. Used as the reference reversible selective MAO-B inhibitor in academic neuroscience.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Clozapine

Plain-language summaryIntrigue 78 / 100

Clozapine (Clozaril) is the most effective antipsychotic ever developed, and it has held that title since the 1980s without serious challenger. It was approved by the FDA in 1989 specifically for treatment-resistant schizophrenia and remains the only drug demonstrated to reduce suicidality in schizophrenia. The catch is severe: roughly one in 100 patients develops agranulocytosis, a potentially fatal collapse of white blood cell production, which is why every patient on clozapine in the United States must submit to weekly, then biweekly, then monthly blood draws indefinitely. Mechanistically it is the prototype atypical antipsychotic, with weak D2 blockade compensated by potent 5-HT2A blockade and a wide net of effects on histamine, muscarinic, and adrenergic receptors. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

57/100

Gold standard for treatment-resistant schizophrenia but low novelty and exhausted mechanism space limit research appeal

Look, clozapine is one of the most clinically important psychiatric compounds in modern medicine. The gold standard for treatment-resistant schizophrenia since the early 1990s, it consistently outperforms every other antipsychotic in TRS populations across decades of multi-center trials. That 1% agranulocytosis incidence is genuinely dangerous and the weekly CBC monitoring requirement through the first six months is a real burden on both patient and system, and still no other drug in the class has managed to displace it for TRS. That clinical track record is not marketing. Its real, its replicated, and its durable.

The receptor pharmacology is what put clozapine on the map as a research object. The weak D2 antagonism (Ki ~130 nM) paired with potent 5-HT2A antagonism (Ki ~16 nM), plus a broad off-target profile spanning D4, muscarinic M1-M5, H1, alpha-1, and multiple 5-HT subtypes, gave investigators the receptor-binding template that defined the entire atypical antipsychotic class. The M1 affinity (Ki ~7 nM) is particularly interesting for anyone studying muscarinic contributions to cognition or psychosis. The M4 partial agonism that produces paradoxical hypersalivation in an otherwise anticholinergic compound is one of the genuinely under-worked threads still worth pursuing.

Here’s the thing though: as a forward-looking research target, novelty is a real problem. This is a 1989 approved drug whose core mechanism has been studied exhaustively for 35 years. The atypical class it spawned has been dissected from every angle conceivable. The literature isnt sparse, its saturated. You can open any receptor pharmacology textbook and find clozapine used as the canonical example. Investigators reach for it precisely because the answers are known, not because theres something new to find. Thats the opposite of an underexplored compound.

What keeps clozapine relevant in a research library is its probe and comparator value. For anyone working on antipsychotic mechanism studies, its the reference everyone is implicitly measuring against. For investigators studying TRS biology, its essentially the only validated positive control. For labs interrogating D4 receptor function specifically, clozapines selectivity profile is still a useful tool despite the years. We think the M4 partial agonism angle and the CYP1A2 metabolism interactions (particularly in smokers, who dramatically accelerate clearance) remain underexplored relative to the compounds clinical importance.

Honestly, the positioning is this: outstanding evidence quality, strong translational signal, real bench probe value in the right context, but genuinely low novelty and a mechanism space that most investigators have already mapped thoroughly. For a lab focused on whats next in CNS pharmacology, clozapine is background knowledge. For a lab working specifically on treatment resistance mechanisms, comparative antipsychotic pharmacology, or muscarinic-dopamine crosstalk, it earns its place on the bench.

Novelty

20

Mechanism promise

40

In-category differentiation

65

Evidence quality

82

Translational signal

78

Research bench value

75

Rationale Clozapine earns strong marks on evidence quality, translational signal, and bench probe value given its canonical reference-compound role and unmatched TRS clinical record, but 1989 FDA approval, fully characterized multireceptor pharmacology, and a thoroughly saturated literature drag novelty and mechanism scores down sharply. No scheduling cap or structural category cap applies; the score reflects a genuinely important but mature compound with limited frontier value for forward-looking research programs.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Atypical antipsychotic / D4-D2 multireceptor antagonist

The prototype atypical antipsychotic; the gold standard for treatment-resistant schizophrenia, limited by agranulocytosis risk requiring weekly blood monitoring.

Abstract

Clozapine (8-chloro-11-(4-methylpiperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine; CAS 5786-21-0; molecular formula C18H19ClN4; molecular weight 326.82) is a dibenzodiazepine atypical antipsychotic developed at Wander/Sandoz and approved by the FDA in 1989 under the trade name Clozaril. The compound is the prototype atypical antipsychotic, introducing the receptor profile that defines the class: weak D2 antagonism (Ki approximately 130 nM) combined with potent 5-HT2A antagonism (Ki approximately 16 nM), producing antipsychotic efficacy without the extrapyramidal symptoms typical of high-affinity D2 antagonists. Off-target activity is broad: H1, alpha-1, muscarinic M1-M5 (Ki approximately 7 nM at M1), 5-HT2C, 5-HT3, 5-HT6, 5-HT7 antagonism, contributing to sedation, weight gain, sialorrhea (paradoxical from M4 partial agonism), and orthostatic hypotension. The defining clinical feature is efficacy in treatment-resistant schizophrenia, where clozapine consistently outperforms other antipsychotics; the limitation is approximately 1 percent agranulocytosis incidence, requiring weekly CBC monitoring through the first 6 months and biweekly thereafter. Plasma half-life is 12 hours; metabolism is via CYP1A2 (primary), CYP3A4, CYP2D6. Used as the canonical atypical antipsychotic in mechanism studies and as the gold standard for treatment-resistant schizophrenia.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Quetiapine

Plain-language summaryIntrigue 65 / 100

Quetiapine (Seroquel) is a workhorse atypical antipsychotic from AstraZeneca, approved in 1997, that has become equally famous as an off-label sleep aid because its potent histamine-receptor blockade makes the low-dose form (25 to 100 mg) profoundly sedating. At full antipsychotic doses (300 to 800 mg) it is used for schizophrenia and acute mania. At intermediate doses (150 to 300 mg) it is FDA-approved for bipolar depression and as add-on for major depression. The active leftover after liver metabolism, norquetiapine, blocks the norepinephrine pump and contributes to the antidepressant effect. Metabolic side effects (weight gain, lipid and glucose disturbance) are real and dose-related, which has prompted concern about its widespread use as a sleep drug. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

45/100

Well-evidenced atypical antipsychotic; low novelty, the norquetiapine metabolite angle is its only remaining research hook

Look, quetiapine is about as far from a frontier compound as you can get. Approved by the FDA in 1997, it’s had nearly three decades of clinical scrutiny across schizophrenia, bipolar disorder, and adjunctive MDD, and the literature is enormous. That massive evidence base is real and we’d never dispute the clinical utility. But clinical utility isn’t what this library is scoring, and on novelty and differentiation, quetiapine earns almost nothing.

The receptor profile is famously broad: 5-HT2A, H1, alpha-1, 5-HT1A partial agonism, and a D2 Ki of roughly 770 nM that makes it the weakest D2 binder in the class. That weak D2 story was actually interesting at one point, back when investigators were trying to understand why some atypicals showed fewer extrapyramidal effects. But that conversation is decades old and well-resolved. The mechanism that still earns quetiapine some research attention is the norquetiapine metabolite angle: norquetiapine is a potent NET inhibitor (Ki around 35 nM) and a 5-HT2C antagonist, which explains the compound’s antidepressant signal and its FDA approval as an MDD adjunct. Thats genuinely interesting pharmacology; a real example of a case where the metabolite carries a mechanistically distinct payload from the parent. We like that story. What we don’t like is that the story is also well-characterized at this point, with the norquetiapine mechanism essentially textbook since the early 2010s.

The translational and evidence scores are high because quetiapine simply has an exceptional clinical database. Multiple phase 3 trials across multiple indications, replicated over years, with regulatory consensus in several jurisdictions. If you want a reference atypical antipsychotic for mechanism work or as a comparison arm in a preclinical model, quetiapine is a reasonable choice. That’s real bench value and we’re crediting it. But a reference compound isn’t the same as an indispensable probe, and nothing about quetiapine’s mechanism lets you answer a question you genuinely couldn’t answer with a contemporary or successor compound.

The off-label hypnotic use, which is where most investigators encounter it outside psychiatry, is an honest embarrassment. Using a broad-spectrum atypical at 25 to 100 mg for sleep is largely an H1-mediated antihistamine effect, and the side-effect burden relative to that marginal signal is hard to defend. No serious investigator is building a sleep research program around this compound right now.

What quetiapine is, in the end, is a well-understood and clinically important drug that happens to have a metabolite worth knowing about. The norquetiapine/NET angle is genuinely interesting as a case study in active metabolite pharmacology. The compound itself as a research target scores where it scores: high on evidence, low on novelty, and not particularly differentiated in a very crowded class.

Novelty

18

Mechanism promise

38

In-category differentiation

28

Evidence quality

82

Translational signal

75

Research bench value

45

Rationale Quetiapine’s near-three-decade clinical history yields high evidence and translational scores, but novelty and differentiation are floor-level for an approved drug in a crowded antipsychotic class; the norquetiapine NET inhibitor story keeps mechanism and bench value from bottoming out but doesn’t rescue the overall.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Atypical antipsychotic

A dibenzothiazepine atypical antipsychotic with broad receptor binding; the active metabolite norquetiapine is a NET inhibitor contributing to antidepressant efficacy.

Abstract

Quetiapine (2-[2-(4-dibenzo[b,f][1,4]thiazepin-11-yl-piperazin-1-yl)ethoxy]ethanol; CAS 111974-69-7; molecular formula C21H25N3O2S; molecular weight 383.51) is a dibenzothiazepine atypical antipsychotic developed at AstraZeneca and approved by the FDA in 1997 under the trade name Seroquel. The receptor profile is broad: D2 (Ki approximately 770 nM, the weakest of the antipsychotic class), 5-HT2A (Ki approximately 295 nM), H1 (Ki approximately 11 nM), alpha-1 (Ki approximately 22 nM), 5-HT1A partial agonism. The active metabolite norquetiapine (formed via CYP3A4) is a potent NET inhibitor (Ki approximately 35 nM) and a 5-HT2C antagonist, contributing to antidepressant efficacy and supporting the FDA-approved adjunctive use in major depressive disorder. Plasma half-life is 6 to 7 hours; metabolism is via CYP3A4. Approved for schizophrenia, bipolar I disorder (mania, depression, maintenance), and adjunctive in MDD. Off-label use as a hypnotic at 25 to 100 mg is widespread despite a poor efficacy-to-side-effect ratio for that indication. Used as a reference broad-spectrum atypical antipsychotic in mechanism studies.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Olanzapine

Plain-language summaryIntrigue 64 / 100

Olanzapine (Zyprexa) is the closest pharmacological cousin of clozapine, brought to market by Eli Lilly in 1996 specifically to capture clozapine’s effectiveness without its agranulocytosis risk. That worked: olanzapine is reliably one of the more effective antipsychotics for schizophrenia and acute mania, and patients do not need weekly blood draws. The trade-off is the worst metabolic profile of any drug in its class. Patients on olanzapine routinely gain 10 to 30 pounds, develop dyslipidemia, and progress to type 2 diabetes at high rates. Used for schizophrenia, acute mania, and treatment-resistant depression in combination with fluoxetine (the Symbyax product). The recent intramuscular long-acting injection (Zyprexa Relprevv) carries an unusual risk of post-injection delirium and sedation. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

50/100

Mature reference atypical antipsychotic with settled science and minimal frontier research value

Look, the compound’s story begins and essentially ends in 1996, when Eli Lilly got FDA approval for Zyprexa. Thats almost thirty years of data, which is simultaneously olanzapine’s greatest asset and its most damning liability as a research target. The evidence base is unimpeachable. CATIE, multiple phase 3 head-to-heads, decades of real-world pharmacovigilance across millions of patients: if you want to know what olanzapine does, the literature tells you with unusual clarity. This is not a compound with ambiguous effects or contested mechanisms.

The receptor profile is genuinely broad and worth understanding in structural terms. D2 (Ki approximately 11 nM), 5-HT2A (Ki approximately 4 nM), H1 (Ki approximately 0.087 nM, among the tightest H1 affinities in clinical antipsychotic use), plus alpha-1, muscarinic, and multiple serotonin subtypes. That H1 affinity is the most pharmacologically interesting feature: combined H1 and 5-HT2C antagonism produces a metabolic syndrome signature that is the worst of any commonly used antipsychotic, with mean weight gain of 4 to 12 kg over 12 weeks and incident type 2 diabetes well-documented. If your research program is specifically interrogating hypothalamic H1/5-HT2C co-blockade as a driver of metabolic dysregulation, olanzapine is a legitimate and well-characterized probe for that question.

The structural comparison with clozapine also has real value for SAR work. Olanzapine is essentially clozapine with a thieno ring substitution that eliminates the agranulocytosis liability while preserving the broad-spectrum atypical pharmacology. For investigators studying what the clozapine scaffold actually buys you mechanistically, comparing these two compounds is worth pulling apart carefully. Clozapine remains the efficacy gold standard in treatment-resistant schizophrenia; olanzapine is the closest approximation you can study without REMS infrastructure.

What we don’t like: the novelty is gone. The mechanism of atypical antipsychotic action via D2/5-HT2A ratio modulation is settled territory, worked out through the 1990s and confirmed repeatedly since. Theres no fresh frontier here, no emerging indication driving genuine bench excitement, no mechanistic surprise hiding in the data. The compound functions as a reference comparator in clinical trials precisely because it is established science, and that same quality makes it a low-priority target for investigators trying to do something new.

The most active current research angle is low-dose antiemetic use, particularly as a triplet-regimen adjunct for chemotherapy-induced nausea and vomiting. That’s real, has plausible mechanistic support via 5-HT3 and 5-HT2 blockade, and ASCO guidelines now reflect it. But it’s an adjacent application of settled pharmacology, not a discovery. We stock olanzapine as a reference compound. For a CNS pharmacology program that needs a canonical broad-spectrum atypical for mechanistic comparison or metabolic interrogation, it earns its place on the shelf. For investigators hunting genuinely fresh targets, the literature here is already written.

Novelty

18

Mechanism promise

32

In-category differentiation

48

Evidence quality

85

Translational signal

80

Research bench value

55

Rationale Olanzapine scores high on evidence and translational signal because it is an FDA-approved drug with three decades of replicated clinical data, but both novelty and mechanism promise are low: the D2/5-HT2A atypical pharmacology story has been understood since the clozapine era, and there is no emerging indication or mechanistic surprise driving serious bench interest. Bench value is moderate because it functions as a canonical reference compound and a legitimate probe for H1/5-HT2C-driven metabolic effects.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Atypical antipsychotic

A thienobenzodiazepine atypical antipsychotic structurally and mechanistically related to clozapine, without the agranulocytosis risk.

Abstract

Olanzapine (2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine; CAS 132539-06-1; molecular formula C17H20N4S; molecular weight 312.43) is a thienobenzodiazepine atypical antipsychotic developed at Eli Lilly and approved by the FDA in 1996 under the trade name Zyprexa. The receptor profile is closely related to clozapine: D2 (Ki approximately 11 nM, higher affinity than clozapine), 5-HT2A (Ki approximately 4 nM), H1 (Ki approximately 0.087 nM, among the most potent in clinical use), alpha-1, muscarinic, 5-HT2C, 5-HT3, 5-HT6, 5-HT7. The structural difference from clozapine eliminates the agranulocytosis liability while preserving the broad-spectrum atypical pharmacology. Plasma half-life is 21 to 54 hours; metabolism is via CYP1A2 and direct glucuronidation. The compound carries the highest metabolic risk profile of any commonly used antipsychotic: dyslipidemia, weight gain (mean 4 to 12 kg over 12 weeks), and incident type 2 diabetes are well-documented, attributed to combined H1 and 5-HT2C antagonism. Approved for schizophrenia, bipolar I disorder, and treatment-resistant depression in combination with fluoxetine (Symbyax). Used as a reference broad-spectrum atypical antipsychotic.

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May 9, 2026
Aripiprazole

Plain-language summaryIntrigue 73 / 100

Aripiprazole (Abilify) was the first third-generation antipsychotic, approved by the FDA in 2002. The mechanistic novelty is partial agonism at the dopamine D2 receptor: rather than fully blocking dopamine signaling like first- and second-generation antipsychotics, it sits in the receptor and produces about 30 percent of dopamine’s normal signal. The functional result is region-dependent: where dopamine signaling is excessive (mesolimbic, in psychosis) it acts as a brake; where dopamine signaling is deficient (prefrontal, in negative symptoms) it acts as a mild stimulator. That property makes aripiprazole much less prone to causing the prolactin elevation and metabolic burden of older antipsychotics, although akathisia (motor restlessness) is its signature side effect. Used in schizophrenia, bipolar, depression augmentation, and irritability in autism. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

52/100

The prototype D2 partial agonist, proven clinically across six indications but now superseded on the research frontier by its own successors

Look, aripiprazole is one of the genuinely important pharmacological advances of the past thirty years. The D2 partial agonism concept (Ki around 0.34 nM, intrinsic activity around 30 percent) was a real conceptual breakthrough when Otsuka published it. The logic that a single molecule could behave as a functional antagonist in high-tone mesolimbic circuits while preserving some agonism in low-tone mesocortical and nigrostriatal pathways was elegant, and the clinical results validated it. Six approved indications, long-acting injectable formulations that transformed adherence outcomes, and a metabolic risk profile that sits meaningfully below olanzapine or clozapine. That’s a strong record.

The problem for us is that we’re rating research merit in 2026, not 2002. And in 2026, aripiprazole is textbook. The partial agonism mechanism is fully characterized, the pharmacokinetics (75-hour half-life, CYP3A4 and CYP2D6 metabolism) are well-established, and the clinical literature is enormous to the point of diminishing returns. There isnt a meaningful open question about aripiprazoles mechanism that a bench scientist is going to answer with a new experiment. The interesting unknowns have been answered over the past two decades.

What happened to the research frontier is that the partial agonist concept aripiprazole pioneered got refined by its successors. Cariprazine pushed D3 selectivity significantly higher and produced more interesting data on negative symptoms and cognition. Brexpiprazole modified the receptor profile for a different side-effect footprint. If youre doing D2 partial agonism mechanism work today, aripiprazole is still the canonical reference probe because it’s the most characterized compound in the class, and its 5-HT1A partial agonism (Ki around 1.7 nM, intrinsic activity around 70 percent) plus 5-HT2A antagonism make it genuinely multi-target in a way thats useful for mechanistic dissection. That probe value is real and we credit it.

The evidence quality here is excellent by any standard. Multiple phase 3 RCTs, regulatory approval across jurisdictions, a multi-decade pharmacovigilance record. Translational signal is definitive: this compound works in humans in its target indications. But high evidence quality in an established drug is not the same thing as high research interest. A compound that has been fully characterized and approved is one the field is done discovering. The interesting work now is on the successors and the biology they reveal, not on aripiprazole itself.

We think this belongs in any serious neuropsychiatric research library as the D2 partial agonist reference standard. But honest investigators should go in with calibrated expectations: this is a mature tool with excellent provenance, not a frontier compound. The score reflects that honestly.

Novelty

22

Mechanism promise

45

In-category differentiation

38

Evidence quality

85

Translational signal

82

Research bench value

60

Rationale Aripiprazole scores very high on evidence quality and translational signal because it’s a well-replicated approved drug, but novelty and differentiation drag the overall down sharply. Cariprazine and brexpiprazole have refined the partial agonist concept with better D3 selectivity and cleaner negative-symptom profiles, making aripiprazole the historical reference point rather than the active frontier.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

D2/D3 partial agonist atypical antipsychotic

A piperazinyl-quinolinone partial agonist at D2 and 5-HT1A receptors; the prototype third-generation antipsychotic.

Abstract

Aripiprazole (7-[4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butoxy]-3,4-dihydroquinolin-2(1H)-one; CAS 129722-12-9; molecular formula C23H27Cl2N3O2; molecular weight 448.39) is a piperazinyl-quinolinone D2 partial agonist developed at Otsuka and approved by the FDA in 2002 under the trade name Abilify. Distinct from earlier antipsychotics by partial agonism: D2 affinity is high (Ki approximately 0.34 nM) but intrinsic activity is approximately 30 percent, producing antagonism in regions of high dopaminergic tone (mesolimbic, treating psychosis) and agonism in regions of low tone (mesocortical, mitigating negative symptoms; nigrostriatal, reducing extrapyramidal effects). Additional 5-HT1A partial agonism (Ki approximately 1.7 nM, intrinsic activity approximately 70 percent) and 5-HT2A antagonism complete the profile. The metabolic risk is intermediate (lower than olanzapine or clozapine). Plasma half-life is 75 hours; metabolism is via CYP3A4 and CYP2D6. Approved for schizophrenia, bipolar I disorder, MDD adjunctive, autism-associated irritability, and Tourette syndrome. Long-acting injectable formulations (Abilify Maintena, Aristada) provide monthly administration. Used as the reference D2 partial agonist in mechanism studies.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Brexpiprazole

Plain-language summaryIntrigue 62 / 100

Brexpiprazole (Rexulti) is Otsuka’s refined successor to aripiprazole, approved in 2015. The key tuning is lower intrinsic activity at the dopamine D2 receptor (about 14 percent rather than aripiprazole’s 30 percent), which translates to less akathisia (motor restlessness), the side effect that drove many patients off aripiprazole. The receptor occupancy profile is otherwise broadly similar. Brexpiprazole has FDA approval for schizophrenia, as add-on to antidepressants for major depressive disorder, and notably became the first drug specifically approved for agitation associated with Alzheimer dementia in 2023. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

45/100

Mature D2 partial agonist; a solid reference compound for intrinsic activity research, not a frontier target

Look, brexpiprazole is what happens when a well-understood mechanism gets refined rather than replaced. Otsuka took aripiprazole’s D2 partial agonist chassis and tuned the intrinsic activity down from about 30 percent to 14 percent. That’s real pharmacology. The result is reduced akathisia and a cleaner receptor profile, making it useful as a reference compound for separating out the consequences of D2 intrinsic activity from the other variables that shift across the atypical antipsychotic class. But from a research novelty standpoint, this conversation was largely over by the time Rexulti got FDA approval in 2015.

The mechanism profile is multi-target in the right ways: D2 partial agonism at Ki around 0.30 nM, 5-HT1A partial agonism at Ki around 0.12 nM, and 5-HT2A antagonism. Thats the third-generation antipsychotic formula that aripiprazole pioneered. Brexpiprazole doesn’t change the formula so much as optimize one parameter. For bench work probing the consequences of D2 intrinsic activity levels, it has genuine utility. Pair it with aripiprazole and cariprazine and you get a gradient of intrinsic activities to work across. That’s the legitimate research angle.

What’s actually interesting is the 2023 Alzheimer-associated agitation approval from the RAISE trial. In low-dopaminergic-tone patients, you want a partial agonist that doesn’t overshoot, and the low intrinsic activity specifically addresses that. The FDA approval validated the mechanism logic in a population where these distinctions really matter. We think that’s the most scientifically underappreciated part of the brexpiprazole story.

Evidence quality is solid. Multiple Phase 3 RCTs across schizophrenia, MDD adjunctive, and Alzheimer agitation give it a clinical database that most compounds in this library can’t claim. Translational signal is strong by antipsychotic standards. The problem is that a bench scientist looking for a novel target is going to find brexpiprazole thoroughly characterized. Pharmacokinetics are mapped (91-hour half-life, CYP3A4/2D6 metabolism). Receptor binding is quantified across labs. There’s not much terra incognita left.

Honestly, this is a compound that earns its library place as a reference tool and a case study in intrinsic activity pharmacology, not as a frontier target. We dont score it high because it isn’t asking a new question. It’s answering an old one very well. If your program needs a D2 partial agonist probe with low intrinsic activity and FDA-grade clinical data behind the mechanism, brexpiprazole is the right compound. If you’re hunting the frontier, look elsewhere.

Novelty

22

Mechanism promise

42

In-category differentiation

35

Evidence quality

75

Translational signal

65

Research bench value

38

Rationale Brexpiprazole is a 2015-approved incremental refinement of aripiprazole’s well-established D2 partial agonist mechanism, scoring low on novelty and differentiation but high on evidence quality and translational signal. Its primary research value is as a reference probe for intrinsic activity comparisons and, more recently, as a case study in how low D2 intrinsic activity performs in low-dopaminergic-tone populations following the 2023 Alzheimer agitation approval.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

D2 partial agonist atypical antipsychotic

A second-generation D2 partial agonist refined from aripiprazole; lower D2 intrinsic activity producing reduced akathisia.

Abstract

Brexpiprazole (7-{4-[4-(1-benzothiophen-4-yl)piperazin-1-yl]butoxy}-3,4-dihydroquinolin-2(1H)-one; CAS 913611-97-9; molecular formula C25H27N3O2S; molecular weight 433.57) is a D2 partial agonist developed at Otsuka as a successor to aripiprazole and approved by the FDA in 2015 under the trade name Rexulti. The structural change from aripiprazole replaces the 2,3-dichlorophenyl with a benzothiophen-4-yl, modulating receptor binding kinetics. D2 affinity (Ki approximately 0.30 nM) is comparable to aripiprazole, but intrinsic activity is lower (approximately 14 percent versus 30 percent), producing reduced akathisia and less D2 receptor activation in low-dopaminergic-tone regions. 5-HT1A partial agonism (Ki approximately 0.12 nM) and 5-HT2A antagonism are retained. Plasma half-life is 91 hours; metabolism is via CYP3A4 and CYP2D6. Approved for schizophrenia, MDD adjunctive, and (2023) Alzheimer-associated agitation. Used as the reference second-generation D2 partial agonist with reduced intrinsic activity.

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May 9, 2026
Lurasidone

Plain-language summaryIntrigue 67 / 100

Lurasidone (Latuda) is a Japanese atypical antipsychotic from Sumitomo Dainippon, approved by the FDA in 2010. It blocks dopamine D2, serotonin 5-HT2A, and 5-HT7 receptors in roughly balanced fashion, with very little activity at histamine or muscarinic receptors. That receptor profile gives it the lowest metabolic burden of the atypical antipsychotic class: minimal weight gain, minimal lipid or glucose disturbance, and minimal sedation. The 5-HT7 antagonism appears to contribute distinct procognitive and antidepressant effects, which is why it is approved for both schizophrenia and bipolar depression. The catch is that absorption is highly food-dependent: it must be taken with at least 350 calories or it does not work properly. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundNiche research probe

59/100

Reference 5-HT7 antagonist among approved antipsychotics with a clean metabolic and sedation profile

Look, lurasidone doesn’t show up in our library because it needs introduction. It’s Latuda. It’s been an approved atypical antipsychotic since 2010, used by millions of patients, and the core D2/5-HT2A story is as well-understood as anything in that class gets. The reason it earns a place here isn’t the receptor profile everyone already knows — it’s the 5-HT7 component, and specifically what that means for investigators trying to do clean receptor-level work in bipolar depression or cognitive-outcome models.

The 5-HT7 receptor is underappreciated. It’s a Gs-coupled receptor widely expressed in the SCN, thalamus, and limbic circuitry, implicated in circadian entrainment, mood regulation, and cognitive processing in ways the traditional D2 and 5-HT2A blockade story doesn’t fully explain. Lurasidone’s Ki at 5-HT7 sits around 0.5 nM — making it the most potent 5-HT7 antagonist among all approved antipsychotics in clinical use. That’s not a small thing. When you want to study 5-HT7 contribution to antidepressant effect in a system that also needs regulatory-grade pharmacokinetics and an established safety profile, lurasidone is the reference tool.

What we like is the selectivity shape. Minimal H1 activity means the sedation confound that wrecks olanzapine and quetiapine in any cognition paradigm is largely absent. Minimal muscarinic means no acetylcholine bleed-through in cholinergic-adjacent readouts. The 5-HT1A partial agonism adds complexity but also mirrors the profile of vilazodone, making cross-comparison useful in bipolar depression studies. The food-dependent absorption (roughly 350 kcal required) is an annoyance worth noting in preclinical translational design, and akathisia is the dose-limiting signal in clinical contexts.

Where it loses ground is novelty and bench ceiling. The compound is fifteen years old. The clinical literature for schizophrenia and bipolar I depression is well-replicated — multiple phase 3 trials, FDA approval, substantial real-world data — but that evidence base answers clinical questions, not mechanistic ones. If you want a clean 5-HT7 probe with no D2 confound, SB-269970 or SB-656104 are more selective research tools. Lurasidone’s value is translational: it’s what you reach for when you want to connect receptor-level findings back to a clinically-validated pharmacological context.

Thats the honest case for it. Not a frontier compound, not a workhorse for basic receptor characterization, but a well-validated clinical reference tool with the most potent 5-HT7 profile of anything approved. For investigators running bipolar depression models, circadian disruption paradigms, or cognitive-outcome studies where 5-HT7 contribution is the specific variable, it’s genuinely useful and not easily replaced by something better positioned.

Novelty

33

Mechanism promise

60

In-category differentiation

63

Evidence quality

78

Translational signal

72

Research bench value

52

Rationale Lurasidone holds its place as the most potent 5-HT7 antagonist in clinical use, with a selective receptor shape that limits sedation and metabolic confounds useful for cognition and mood paradigms; its 2010 approval and fully characterized mechanism keep novelty and differentiation modest, and the overall score reflects real but bounded bench utility as a translational tool rather than a frontier research target.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Atypical antipsychotic with 5-HT7 antagonism

A benzisothiazole atypical antipsychotic with prominent 5-HT7 receptor antagonism contributing to procognitive and antidepressant effects.

Abstract

Lurasidone ((3aR,4S,7R,7aS)-2-{(1R,2R)-2-[4-(1,2-benzisothiazol-3-yl)piperazin-1-ylmethyl]-cyclohexylmethyl}hexahydro-4,7-methano-2H-isoindole-1,3-dione; CAS 367514-87-2; molecular formula C28H36N4O2S; molecular weight 492.68) is a benzisothiazole atypical antipsychotic developed at Sumitomo Dainippon and approved by the FDA in 2010 under the trade name Latuda. The receptor profile features full D2 antagonism (Ki approximately 1 nM), potent 5-HT2A antagonism (Ki approximately 0.5 nM), 5-HT1A partial agonism (Ki approximately 6.4 nM), and prominent 5-HT7 antagonism (Ki approximately 0.5 nM, the most potent in clinical use). The 5-HT7 antagonism is associated with procognitive effects and improvement in bipolar depression. H1 and muscarinic activity is minimal, producing low sedation and metabolic burden compared to olanzapine and quetiapine; the principal limitation is dose-related akathisia. Plasma half-life is 18 hours; absorption requires food (approximately 350 kcal). Metabolism is via CYP3A4. Approved for schizophrenia (acute and maintenance), bipolar I depression (monotherapy or with lithium/valproate). Used as the reference 5-HT7-prominent antipsychotic.

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May 9, 2026
Risperidone

Plain-language summaryIntrigue 65 / 100

Risperidone (Risperdal) is the most prescribed atypical antipsychotic in the world. Janssen brought it to market in 1993 as the prototype of the combined dopamine D2 plus serotonin 5-HT2A blocker design that defined second-generation antipsychotics. Approved for schizophrenia, bipolar mania, and irritability in autism, it is also widely used off-label in dementia behavioral disturbance and various pediatric conditions. At low doses (1 to 2 mg) it acts more like a typical atypical; at higher doses (above 6 mg) the 5-HT2A advantage washes out and it produces extrapyramidal symptoms and prolactin elevation comparable to older haloperidol. Its active leftover is itself sold separately as paliperidone (Invega). Available as a long-acting injection (Risperdal Consta) for adherence support. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

47/100

The canonical D2/5-HT2A reference atypical: indispensable as a probe, not interesting as a discovery target

Look, risperidone is one of those compounds where the score almost writes itself. Approved in 1993, the most prescribed atypical antipsychotic on the planet, a metabolite (paliperidone) that got its own branded approval. The D2/5-HT2A dual antagonism profile was genuinely interesting when Janssen published it, but that was over thirty years ago, and the pharmacology has been beaten to death across thousands of studies. There is no open mechanism question here.

The receptor profile is textbook at this point: D2 at roughly 4 nM Ki, 5-HT2A at roughly 0.16 nM, a 25:1 ratio that drives the atypical character at low doses and collapses into something approaching haloperidol above 6 mg. The dose-EPS relationship is cited in every antipsychotic pharmacology lecture. The active metabolite contribution is fully characterized. The long-acting injectable formulations are mature commercial products. We’re not going to learn something new about risperidone by running another preclinical series on it.

Where it does hold up as a library entry is bench utility. If your lab is interrogating dopamine receptor biology, autism rodent models, antipsychotic-induced metabolic side effects, or the 5-HT2A / D2 interaction in prefrontal circuits, risperidone is the reference compound. Its well-characterized receptor kinetics and extensive pharmacokinetic database make it a reliable anchor for comparison studies. That’s not nothing. The bench value here is real, its just the value of a well-understood reference, not the value of a frontier probe.

Whats genuinely low here is novelty and mechanism promise. The combined D2/5-HT2A antagonist class is completely saturated. Aripiprazole took the partial agonist angle. Clozapine remains the efficacy benchmark with its messy multireceptor profile. Brexpiprazole and cariprazine refined the partial agonist story further. Risperidone sits as the prototype definition of the class, which means investigators in the field use it as a comparator, not an object of investigation. If you’re designing an experiment to answer a novel question about psychosis biology, risperidone is your control arm, not your experimental arm.

The evidence quality and translational scores are legitimately high. Three approved indications, multiple phase 3 programs, long-acting formulations with their own trial bases, decades of post-marketing surveillance. We’re not questioning the clinical reality. But the rubric asks whether a bench scientist should find this compound worth primary research time right now, and the honest answer is almost certainly no unless the goal is characterizing something new against a reliable reference. As a discovery target in 2025, risperidone is basically done.

Novelty

18

Mechanism promise

28

In-category differentiation

40

Evidence quality

82

Translational signal

75

Research bench value

65

Rationale Risperidone is a 1993-approved, fully characterized reference compound whose novelty and mechanism scores are floor-bound by three decades of settled pharmacology; evidence and translational scores are ceiling-bound by its FDA approval across three indications, but those high downstream scores can’t rescue the overall because the rubric weights novelty and mechanism heavily. Bench value is real but narrow: it scores meaningfully as a canonical probe for D2/5-HT2A biology, not as a frontier research target.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Atypical antipsychotic

A benzisoxazole atypical antipsychotic; the most prescribed atypical worldwide and the prototype combined D2 / 5-HT2A antagonist.

Abstract

Risperidone (3-{2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidin-1-yl]ethyl}-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one; CAS 106266-06-2; molecular formula C23H27FN4O2; molecular weight 410.49) is a benzisoxazole atypical antipsychotic developed at Janssen and approved by the FDA in 1993 under the trade name Risperdal. The receptor profile is the prototype combined D2/5-HT2A antagonist: D2 (Ki approximately 4 nM), 5-HT2A (Ki approximately 0.16 nM, ratio approximately 25:1 favoring 5-HT2A), with secondary alpha-1, alpha-2, and H1 antagonism. At doses below 6 mg the 5-HT2A predominates and EPS is minimal; above 6 mg the D2 antagonism produces dose-dependent EPS approaching haloperidol-like profile. The active metabolite 9-hydroxyrisperidone (paliperidone, marketed as Invega) carries similar receptor profile and contributes substantially to steady-state activity. Risperidone is the most prescribed atypical antipsychotic worldwide. Plasma half-life is 3 hours for parent, 24 hours for paliperidone metabolite. Long-acting injectables (Risperdal Consta, Perseris) provide biweekly or monthly administration. Approved for schizophrenia, bipolar mania, autism-associated irritability. Used as the canonical D2/5-HT2A reference atypical.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026

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