Modifying One Position on THC Created Compounds That Preferentially Targeted the CB2 Immune Receptor | Research

The takeaway

Researchers identified a specific molecular position (C-1) on classical cannabinoids where modifications produced compounds with selectivity for the CB2 receptor, potentially separating therapeutic effects from psychoactive ones.

Read this if you are interested in the science behind developing non-psychoactive therapeutic cannabinoids.

CB2 selectivity ratio of 4.5 achieved through C-1 position modification

What the researchers found

Separating the mood-altering effects of cannabinoids from their therapeutic effects has been a long-standing goal. This study found that modifications at the C-1 position of classical cannabinoid structures produced compounds with selectivity for the CB2 receptor over the CB1 receptor.

A series of cyclic ether THC derivatives were synthesized and tested. Analogs containing an oxygen attached to C-9 showed the highest CB2 affinity and selectivity, with one compound achieving a CB2 binding affinity of 5.8 nM and a selectivity ratio of 4.5.

The compounds produced dose-dependent effects in tissue assays that were blocked by a CB1 antagonist. In live animals, one analog produced pain relief with reduced activity in three other behavioral measures, suggesting partial separation of therapeutic and psychoactive effects.

Why it matters

This study identified a specific molecular position for achieving CB2 receptor selectivity, which is important because CB2 activation may produce anti-inflammatory and pain-relieving effects without the psychoactive effects mediated by CB1. This work advanced the goal of creating therapeutic cannabinoids without the "high."

The numbers in context

Best CB2 compound: Ki(CB1) = 26 nM, Ki(CB2) = 5.8 nM, selectivity ratio 4.5. Another compound: Ki(CB1) = 90 nM, Ki(CB2) = 23 nM, selectivity ratio 3.9.

How the study worked

Medicinal chemistry study synthesizing five C-9 analogs of O,2-propano-delta-8-THC. Compounds were evaluated using radioligand displacement assays for CB1 and CB2 receptor affinity, mouse vas deferens tissue assays, and the mouse behavioral tetrad for in vivo cannabinoid activity.

What this study cannot tell us

The selectivity ratios achieved (3.9-4.5) were modest. Mouse behavioral assays may not predict human pharmacology. Only a small series of analogs was tested.

How to read the evidence

A medicinal chemistry study with in vitro binding assays and in vivo behavioral testing. Rigorous pharmacology but early-stage drug discovery.

When this study was published

Published in 1997. CB2-selective drug development has continued, with several compounds reaching clinical trials for various conditions.

The bigger picture

CB2-selective cannabinoids remain an active area of pharmaceutical development. The identification of the C-1 position as key for selectivity contributed to the rational design of subsequent CB2-selective compounds for potential treatment of inflammation, pain, and other conditions without psychoactive effects.

Questions still open

Can greater CB2 selectivity be achieved with further modifications? Do CB2-selective compounds produce meaningful therapeutic effects in humans? Has this C-1 position insight led to clinical development of CB2-selective drugs?

Common questions

What is the CB2 receptor?

CB2 is a cannabinoid receptor found primarily in immune cells and peripheral tissues. Unlike CB1 (found in the brain), CB2 activation is not thought to produce psychoactive effects.

Could this lead to non-psychoactive cannabis medicines?

That is the goal. By targeting CB2 selectively, researchers hope to create cannabinoid drugs that provide therapeutic benefits without the mind-altering effects of THC.

Read the original research

Importance of the C-1 substituent in classical cannabinoids to CB2 receptor selectivity: synthesis and characterization of a series of O,2-propano-delta 8-tetrahydrocannabinol analogs.

Journal of medicinal chemistry, 40(20), 3312-8

View on PubMed

Citation

Reggio, P H; Wang, T; Brown, A E; Fleming, D N; Seltzman, H H; Griffin, G; Pertwee, R G; Compton, D R; Abood, M E; Martin, B R. (1997). Importance of the C-1 substituent in classical cannabinoids to CB2 receptor selectivity: synthesis and characterization of a series of O,2-propano-delta 8-tetrahydrocannabinol analogs.. Journal of medicinal chemistry, 40(20), 3312-8.