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TM38837

Synthetic peripherally acting CB1 antagonist, development halted at the phase I stage.

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.

C₃₀H₂₅Cl₂F₃N₄OS

CID 49779607

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

Updated on

In plain terms

TM38837 is a synthetic molecule developed by a Danish pharmaceutical company, not a hemp compound. It blocks the CB1 receptor, the one on which THC acts, but it was designed to reach the brain very little. It was tested in humans only in a phase 1 study in healthy volunteers; no medicine exists based on this molecule.

Receptors and activity

Target network

CB1Inverse agonistKd = 16 nM · not specifiedvalue cited by Micale et al. 2019 from a conference abstract (Nørregaard et al., ICRS 2010), against Kd ~0.61 nM for rimonabant; by PET in the monkey, in vivo affinity more than 100-fold lower than that of rimonabant (Takano et al. 2014)
  • Blocks or inhibits

The lower the cited value, the closer the target sits to TM38837: 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 TM38837.

Brain, side view
Body, front view
Blood

CB1CB1 found in 7 regions of the body

  1. Basal gangliadenseMost dense in basal ganglia outflow nuclei1
  2. CerebellumdenseVery dense in the cerebellum1
  3. HippocampusdenseVery high concentrations in the hippocampus2
  4. AmygdaladenseHigh concentrations in the amygdala2
  5. CortexpresentPresent throughout the neocortex2
  6. Adipose tissuepresentExpressed in adipose tissue3
  7. GutpresentColonic epithelium, smooth muscle and plexus4

Map sources

  1. Herkenham M et al. Cannabinoid receptor localization in brain. Proc Natl Acad Sci U S A, 1990 (new tab)
  2. Glass M et al. Cannabinoid receptors in the human brain: a detailed anatomical and quantitative autoradiographic study in the fetal, neonatal and adult human brain. Neuroscience, 1997 (new tab)
  3. Engeli S et al. Activation of the peripheral endocannabinoid system in human obesity. Diabetes, 2005 (new tab)
  4. Wright K et al. Differential expression of cannabinoid receptors in the human colon: cannabinoids promote epithelial wound healing. Gastroenterology, 2005 (new tab)

Cited values

  1. CB1Inverse agonistKd = 16 nM · not specified63 out of 100

    Micale et al., Front Pharmacol 2019 (new tab) · value cited by Micale et al. 2019 from a conference abstract (Nørregaard et al., ICRS 2010), against Kd ~0.61 nM for rimonabant; by PET in the monkey, in vivo affinity more than 100-fold lower than that of rimonabant (Takano et al. 2014)

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

TM38837 is an antagonist of the CB1 receptor designed to act only on peripheral receptors. Its affinity is of the order of 16 nM (Kd quoted by Micale et al. 2019), clearly lower than that of rimonabant (about 0.61 nM), but its brain penetration is very low: in rats, the brain receives about 1% of the plasma concentration and the liver about 300% (Cooper et al. 2025). A positron emission tomography study in three cynomolgus monkeys showed brain CB1 occupancy lower than that of rimonabant at the targeted plasma concentrations (Takano et al. 2014). In 24 healthy volunteers given THC, TM38837 at 100 mg did not change the central effects measured (feeling high, body sway), whereas 500 mg partly attenuated them; the effect on heart rate was comparable to that of rimonabant, and the estimated terminal half-life was 771 hours (Klumpers et al. 2013). In mice, only the oral dose of 100 mg/kg increased freezing in a conditioned fear test, like rimonabant at 10 mg/kg (Micale et al. 2019). In obese rats, weight loss was equivalent to that of rimonabant at an equivalent dose, with no significant c-Fos induction in the brain regions examined in lean rats at the selected dose (Cooper et al. 2025). No clinical development after phase 1 was found, and neither clinical efficacy nor long-term tolerability is established in humans.

Key sources.

History

Source
An entirely synthetic molecule, absent from cannabis and from any known organism: a CB1 antagonist designed by 7TM Pharma to have very limited brain penetration (Micale et al. 2019).

Origin

Research tool

No known biosynthetic pathway: TM38837 is a synthetic compound of the pyrazole-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)

TM-38837 (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. Klumpers LE et al. Peripheral selectivity of the novel cannabinoid receptor antagonist TM38837 in healthy subjects. Br J Clin Pharmacol, 2013 (new tab)PMID 23601084
  2. Takano A et al. Low brain CB1 receptor occupancy by a second generation CB1 receptor antagonist TM38837 in comparison with rimonabant in nonhuman primates: a PET study. Synapse, 2014 (new tab)PMID 24293119
  3. Micale V et al. The cannabinoid CB1 antagonist TM38837 with limited penetrance to the brain shows reduced fear-promoting effects in mice. Front Pharmacol, 2019 (new tab)PMID 30949045
  4. Cooper ME et al. Efficacy of the hepatotropic peripheral CB1R inverse agonist TM38837 in rat models of obesity and metabolic syndrome. J Mol Clin Med, 2025;8(1):36687 (new tab)DOI 10.31083/JMCM36687
  5. PubChem, TM-38837, CID 49779607 (identifiers and properties) (new tab)

Identifiers

Names

IUPAC name
1-(2,4-dichlorophenyl)-4-ethyl-N-piperidin-1-yl-5-[5-[2-[4-(trifluoromethyl)phenyl]ethynyl]thiophen-2-yl]pyrazole-3-carboxamide
Other names
TM-38837 · TM 38837

Identifiers

Formula
C₃₀H₂₅Cl₂F₃N₄OS
PubChem CID
49779607(new tab)
InChIKey
VQOCBFYUDSBDCZ-UHFFFAOYSA-N
SMILES
CCC1=C(N(N=C1C(=O)NN2CCCCC2)C3=C(C=C(C=C3)Cl)Cl)C4=CC=C(S4)C#CC5=CC=C(C=C5)C(F)(F)F

Machine-readable entry (JSON)

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