Quetiapine – Kodiac biolabs

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 Kodiac editorial, not peer-reviewed.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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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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