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Research tools

SR144528

Selective CB2 antagonist and inverse agonist (Sanofi, 1998), a laboratory tool with no human 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.

C₂₉H₃₄ClN₃O

CAS 192703-06-3

Family
ECS pharmacological toolAntagonist or inverse agonist
Molar mass
476.10 g/mol

Updated on

In plain terms

SR144528 is an entirely artificial molecule, developed by Sanofi in the late 1990s. It is not found in hemp and does not reproduce the effects of cannabis: it blocks one of the two receptors on which cannabinoids act, CB2, found mainly in immune cells. It serves as a laboratory tool; no study in humans was found.

Receptors and activity

Target network

CB2Inverse agonistKi = 0.6 nM · rat and humanradioligand binding, rat spleen and cloned human CB2; adenylate cyclase antagonism EC50 10 nM, MAP kinases IC50 39 nM, B lymphocytes IC50 20 nM; inverse agonist (Rhee and Kim 2002)
  • Blocks or inhibits
  • Binds or modulates

The lower the cited value, the closer the target sits to SR144528: 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 SR144528.

Brain, side view
Body, front view
Blood

CB2CB2 found in 5 regions of the body

  1. SpleendenseHighly abundant in the spleen1
  2. Immune cellspresentMainly B cells and natural killer cells1
  3. SkinpresentKeratinocytes, mast cells and nerve fibres2
  4. GutpresentImmune cells of the colonic mucosa3
  5. BonepresentPresent on osteoclasts4

Map sources

  1. Galiègue S et al. Expression of central and peripheral cannabinoid receptors in human immune tissues and leukocyte subpopulations. Eur J Biochem, 1995 (new tab)
  2. Ständer S et al. Distribution of cannabinoid receptor 1 (CB1) and 2 (CB2) on sensory nerve fibers and adnexal structures in human skin. J Dermatol Sci, 2005 (new tab)
  3. Wright K et al. Differential expression of cannabinoid receptors in the human colon: cannabinoids promote epithelial wound healing. Gastroenterology, 2005 (new tab)
  4. 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. CB2Inverse agonistKi = 0.6 nM · rat and human87 out of 100

    Rinaldi-Carmona et al., J Pharmacol Exp Ther 1998 (new tab) · radioligand binding, rat spleen and cloned human CB2; adenylate cyclase antagonism EC50 10 nM, MAP kinases IC50 39 nM, B lymphocytes IC50 20 nM; inverse agonist (Rhee and Kim 2002)

  2. CB1Binding (function not established)Ki = 400 nM · rat and human40 out of 100

    Rinaldi-Carmona et al., J Pharmacol Exp Ther 1998 (new tab) · radioligand binding, rat brain and cloned human CB1; roughly 700-fold selectivity for CB2; no functional effect at human CB1 up to 10 µM

  3. GPR6Inverse agonistno measured value cited

    Inverse agonist (cAMP accumulation and β-arrestin 2 recruitment), with functional selectivity towards β-arrestin 2; value not taken from the abstract (Laun et al. 2018)

  4. ACAT (acyl-CoA cholesterol acyltransferase)Inhibitorno measured value cited

    Reduces cholesteryl ester synthesis in mouse macrophages and liver microsomes, independently of CB2; value not taken from the abstract (Thewke et al. 2009)

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

SR144528 was described in 1998 by Sanofi Recherche as the first potent, selective, orally active antagonist of the CB2 receptor. Its affinity is subnanomolar for CB2 (Ki 0.6 nM) and about 700-fold lower for CB1 (Ki 400 nM), a selectivity that made it the reference tool for deciding whether an effect is due to CB2. At nanomolar concentrations it blocks CB2-mediated responses to CP 55,940 (adenylyl cyclase, MAP kinases, B-cell activation) without affecting the equivalent CB1 pathway (Rinaldi-Carmona et al. 1998). Given orally to mice, it totally displaced ex vivo [3H]CP 55,940 binding in spleen (ED50 0.35 mg/kg) with a long duration of action, without interacting with brain CB1 receptors. It is not a simple blocker: it acts as an inverse agonist of CB2 (Rhee and Kim 2002). Its status as a clean tool is qualified by two off-target actions: it inhibits acyl-CoA cholesterol acyltransferase independently of CB2 (Thewke et al. 2009) and has inverse agonist activity at GPR6 (Laun et al. 2018). No study in humans was found.

Key sources.

History

Source
An entirely synthetic molecule, developed by Sanofi Recherche (Rinaldi-Carmona et al. 1998). It belongs to the same chemical family as rimonabant (diarylpyrazole-3-carboxamide) and is known only as a laboratory compound.

Origin

Research tool

No natural biosynthetic pathway: SR144528 is a synthetic compound of the diarylpyrazole-3-carboxamide class, not described in any living organism.

Classification

Family, origin and source verification

Family

ECS pharmacological tool › Antagonist or inverse agonist

Verification

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

Wikipedia (English)

SR-144,528 (new tab)

Article paired by the molecule's structure (InChIKey), revision read on 19 October 2026. Read as a second opinion, never cited as a source.

References

  1. Rinaldi-Carmona M et al. SR 144528, the first potent and selective antagonist of the CB2 cannabinoid receptor. J Pharmacol Exp Ther, 1998 (new tab)PMID 9454810
  2. Rhee MH, Kim SK. SR144528 as inverse agonist of CB2 cannabinoid receptor. J Vet Sci, 2002 (new tab)PMID 12514329
  3. Thewke D et al. AM-251 and SR144528 are acyl CoA:cholesterol acyltransferase inhibitors. Biochem Biophys Res Commun, 2009 (new tab)PMID 19338772
  4. Laun AS, Shrader SH, Song ZH. Novel inverse agonists for the orphan G protein-coupled receptor 6. Heliyon, 2018 (new tab)PMID 30480157
  5. PubChem, SR144528, CID 3081355 (identifiers and properties) (new tab)

Identifiers

Names

IUPAC name
5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-N-[(1S,2S,4R)-1,3,3-trimethyl-2-bicyclo[2.2.1]heptanyl]pyrazole-3-carboxamide
Other names
SR 144528 · SR-144528

Identifiers

Formula
C₂₉H₃₄ClN₃O
CAS
192703-06-3
PubChem CID
3081355(new tab)
InChIKey
SUGVYNSRNKFXQM-XRHWURSXSA-N
SMILES
CC1=CC=C(C=C1)CN2C(=CC(=N2)C(=O)N[C@H]3[C@]4(CC[C@H](C4)C3(C)C)C)C5=CC(=C(C=C5)Cl)C

Machine-readable entry (JSON)

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