Atypical antipsychotic – Kodiac biolabs

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 Kodiac editorial, not peer-reviewed.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.

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.

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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.

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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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

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.

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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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

Tag: Atypical antipsychotic

Quetiapine

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Olanzapine

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Risperidone

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