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Research tools

URB694

An irreversible FAAH inhibitor: it raises anandamide levels, a research tool with no clinical use.

Unscheduled
Level of detail

Harm-reduction warning

No characterised human dose: animal / in vitro data only. Effect profile, safety margin and acute toxicity are not documented in human clinical practice. Extremely potent compound: severe effects, seizures and deaths reported in the literature.

C₁₉H₂₁NO₃

CID 44626363

Family
ECS pharmacological toolEnzyme inhibitor
Molar mass
311.40 g/mol

Updated on

In plain terms

URB694 is a molecule made in the laboratory: it does not come from hemp. It blocks the enzyme that destroys anandamide, a cannabinoid the body makes itself, which makes its level rise. It is used as a research tool in animals and, in radioactive form, as a marker for brain imaging; no clinical trial was found.

Receptors and activity

Target network

FAAH (fatty acid amide hydrolase)InhibitorIC50 = 30 nM · rat[3H]anandamide hydrolysis, rat brain membranes; irreversible inhibition; ex vivo 50% inhibitory dose of 0.16 mg/kg (mouse, intraperitoneal route)
  • Blocks or inhibits

The lower the cited value, the closer the target sits to URB694: one ring per factor of 100. A target with no measured value stays on the edge.

Where these targets live

Where each target has been found in humans, according to the cited studies. The map shows the target, not an effect of URB694.

Brain, side view
Body, front view
Blood

FAAHFAAH found in 7 regions of the body

  1. CortexpresentCortical pyramidal neurons1
  2. Basal gangliapresentStriatal neurons1
  3. HypothalamuspresentPresent in hypothalamic nuclei1
  4. CerebellumpresentPurkinje cells and cerebellar layers1
  5. BrainstempresentInferior olivary nuclei1
  6. Adipose tissuepresentExpressed in mature adipocytes2
  7. BonepresentPresent on osteoclasts3

Map sources

  1. Romero J et al. Fatty acid amide hydrolase localization in the human central nervous system: an immunohistochemical study. Brain Res Mol Brain Res, 2002 (new tab)
  2. Engeli S et al. Activation of the peripheral endocannabinoid system in human obesity. Diabetes, 2005 (new tab)
  3. Rossi F et al. The endovanilloid/endocannabinoid system in human osteoclasts: possible involvement in bone formation and resorption. Bone, 2009 (new tab)

Cited values

  1. FAAH (fatty acid amide hydrolase)InhibitorIC50 = 30 nM · rat59 out of 100

    Clapper et al., ChemMedChem 2009 (table 1) (new tab) · [3H]anandamide hydrolysis, rat brain membranes; irreversible inhibition; ex vivo 50% inhibitory dose of 0.16 mg/kg (mouse, intraperitoneal route)

Bar length follows the measured value (Ki, Kd, EC50 or IC50), on one scale shared by every entry, from 100 µM to 0.1 nM. A target with no cited value has no bar.

Pharmacology

URB694 is an O-aryl carbamate belonging to the second generation of FAAH inhibitors, the enzyme that degrades anandamide. It does not bind to cannabinoid receptors: it inhibits FAAH irreversibly, with an IC50 of 30 nM on rat brain membranes and a 50% inhibitory dose of 0.16 mg/kg in mice. Its half-life in rat plasma (950 minutes) is about 29 times longer than that of URB597, its peak brain concentration after 1 mg/kg intraperitoneally is about 2 times higher, and it reacts less with liver carboxylesterases (Clapper et al. 2009). Unlike URB937, it reaches the brain, a property exploited by [11C]CURB, a tracer of brain FAAH in positron emission tomography: the dosimetry study in six healthy volunteers (about 350 MBq and 2 µg) reported good tolerability with no adverse event attributed to the tracer (Boileau et al. 2014), and a voxel-level quantification method was validated in 2018 (Rusjan et al.). In rats, URB694 decreased anxiety-like behaviour and isoprenaline-induced ventricular tachyarrhythmias in high-anxiety rats, this cardiac effect being blocked by a CB1 but not a CB2 antagonist (Carnevali et al. 2015), and corrected depressive-like alterations induced by social stress (Carnevali et al. 2015; Barbetti et al. 2024). In squirrel monkeys it changed nicotine self-administration, but it was itself self-administered at a moderate rate, unlike URB597, a behaviour blocked by MK886 or rimonabant (Justinova et al. 2015). No therapeutic study in humans was found.

Key sources.

History

Source
An entirely synthetic molecule with no known natural occurrence: it was designed in the laboratory as a FAAH inhibitor (Clapper et al. 2009), then labelled with carbon-11 as a positron emission tomography imaging tracer (Boileau et al. 2014).

Origin

Research tool

No biosynthetic pathway: the compound comes from no living organism. It is an O-aryl carbamate, combining a cyclohexyl group with a hydroxylated biphenyl.

Classification

Family, origin and source verification

Family

ECS pharmacological tool › Enzyme inhibitor

Verification

Classification, sources and binding values checked on 20 October 2026; text read against its sources and Wikipedia.

Wikipedia (English)

No dedicated article.

References

  1. Clapper JR et al. A second generation of carbamate-based fatty acid amide hydrolase inhibitors with improved activity in vivo. ChemMedChem, 2009 (new tab)PMID 19637155
  2. Vacondio F et al. Structure-property relationships of a class of carbamate-based fatty acid amide hydrolase inhibitors: chemical and biological stability. ChemMedChem, 2009 (new tab)PMID 19554599
  3. Boileau I et al. Whole-body radiation dosimetry of 11C-carbonyl-URB694: a PET tracer for fatty acid amide hydrolase. J Nucl Med, 2014 (new tab)PMID 25413137
  4. Justinova Z et al. Effects of fatty acid amide hydrolase (FAAH) inhibitors in non-human primate models of nicotine reward and relapse. Neuropsychopharmacology, 2015 (new tab)PMID 25754762
  5. Carnevali L et al. Cardioprotective effects of fatty acid amide hydrolase inhibitor URB694, in a rodent model of trait anxiety. Sci Rep, 2015 (new tab)PMID 26656183
  6. Carnevali L et al. Antidepressant-like activity and cardioprotective effects of fatty acid amide hydrolase inhibitor URB694 in socially stressed Wistar Kyoto rats. Eur Neuropsychopharmacol, 2015 (new tab)PMID 26391492
  7. Rusjan PM et al. Voxel level quantification of [11C]CURB, a radioligand for fatty acid amide hydrolase, using high resolution positron emission tomography. PLoS One, 2018 (new tab)PMID 29444138
  8. Barbetti M et al. Social stress-induced depressive-like symptoms and changes in gut microbial and lipidomic profiles are prevented by pharmacological inhibition of FAAH activity in male rats. Prog Neuropsychopharmacol Biol Psychiatry, 2024 (new tab)PMID 38354897
  9. PubChem, URB694, CID 44626363 (identifiers and properties) (new tab)

Identifiers

Names

IUPAC name
(4-hydroxy-3-phenylphenyl) N-cyclohexylcarbamate
Other names
URB-694 · URB 694 · CURB · [11C]CURB · 6-Hydroxy-[1,1'-biphenyl]-3-yl cyclohexylcarbamate · FAAH Inhibitor, 2g

Identifiers

Formula
C₁₉H₂₁NO₃
PubChem CID
44626363(new tab)
InChIKey
KRJOFKFEYDSZAV-UHFFFAOYSA-N
SMILES
C1CCC(CC1)NC(=O)OC2=CC(=C(C=C2)O)C3=CC=CC=C3

Machine-readable entry (JSON)

LLM ingestion format: a structured superset of the entry (identifiers, binding, versioned legal status). Full corpus.