CP-55,940

CP-55,940 is a synthetic cannabinoid developed as a research compound during the search for non-opioid analgesics. It is a potent agonist at both CB₁ and CB₂ receptors and became an important tool in cannabinoid research, including studies that helped establish the pharmacology of the cannabinoid receptor system. It is not a medicine approved for routine human use.

Chemistry and research background

CP-55,940 is a non-classical bicyclic cannabinoid. Its structure differs from THC: it lacks the classical dibenzopyran ring system but retains structural features that allow it to interact strongly with cannabinoid receptors. It was developed by Pfizer and belongs to the same broad research series as CP-47,497.

Radiolabelled CP-55,940 was used in early experiments to identify cannabinoid binding sites in brain tissue. Those studies contributed to the identification of CB₁ receptors and the later distinction between CB₁ and CB₂ receptor pharmacology (Huffman and colleagues, 2008).

Pharmacology

CP-55,940 is a high-affinity, high-efficacy agonist at CB₁ and CB₂ receptors. One widely cited binding study reported Ki values of 0.58 nM at CB₁ and 0.69 nM at CB₂, although values vary between assay systems. It is often used as a reference full agonist when researchers compare the efficacy of other cannabinoid ligands (The structure–function relationships of classical cannabinoids, 2016).

Because CP-55,940 activates both receptor subtypes, it is not a selective CB₁ or CB₂ ligand. Its role in research is partly comparative: it provides a well-characterised reference point for measuring receptor binding and signalling by newer compounds.

Effects in experimental models

In animal studies, CP-55,940 produces a range of cannabimimetic responses, including reduced locomotor activity, hypothermia, antinociception and catalepsy. These effects are used to study cannabinoid receptor function and to compare the activity of experimental compounds. They do not establish a human subjective effect profile.

CP-55,940 has also been used in cell-based assays and radioligand-binding experiments. Its high receptor affinity makes it useful in laboratory work, but those properties should not be confused with evidence of clinical benefit or safety.

Human effects and toxicity

There is no substantial controlled human literature defining the subjective effects, pharmacokinetics or toxic range of CP-55,940. It is primarily a research ligand, not a compound with an established history of human therapeutic use. Effects reported for recreational synthetic cannabinoids cannot be assumed to occur with CP-55,940.

Its potent CB₁ activity is relevant to its pharmacology, but receptor potency alone does not determine how a compound behaves in people. Absorption, distribution, metabolism, route of exposure and receptor signalling all affect the overall response.

Related compounds

CP-55,940 is related to CP-47,497 and its C8 homologue. It is also frequently used as a reference compound in studies of JWH-018 and other synthetic cannabinoid receptor agonists.