6 research outputs found
C‑Ring Cannabinoid Lactones: A Novel Cannabinergic Chemotype
As a part of our controlled-deactivation
ligand development project,
we recently disclosed a series of (−)-Δ<sup>8</sup>-tetrahydrocannabinols
(THCs) with a metabolically labile ester group at the 2′-position
of the side chain. Now, we have replaced the C-ring in the classical
THC structure with a hydrolyzable seven-membered lactone. One of the
synthesized analogues binds with high affinity to the CB1 receptor
(<i>K</i><sub>i</sub> = 4.6 nM) and exhibits much lower
affinities for the mCB2 and the hCB2. Also, in vitro functional characterization
found the compound to be an agonist at rCB1. Consistent with our rational
design, the lead cannabinergic lactone identified here is susceptible
to metabolic inactivation by plasma esterases, while the respective
acid metabolite is inactive at CB receptors. These results are highlighted
with molecular modeling of the two regiosomeric lactones
3′-Functionalized Adamantyl Cannabinoid Receptor Probes
The aliphatic side chain plays a
pivotal role in determining the
cannabinergic potency of tricyclic classical cannabinoids, and we
have previously shown that this chain could be substituted successfully
by adamantyl or other polycyclic groups. In an effort to explore the
pharmacophoric features of these conformationally fixed groups, we
have synthesized a series of analogues in which the C3 position is
substituted directly with an adamantyl group bearing functionality
at one of the tertiary carbon atoms. These substituents included the
electrophilic isothiocyanate and photoactivatable azido groups, both
of which are capable of covalent attachment with the target protein.
Our results show that substitution at the 3′-adamantyl position
can lead to ligands with improved affinities and CB1/CB2 selectivities.
Our work has also led to the development of two successful covalent
probes with high affinities for both cannabinoid receptors, namely,
the electrophilic isothiocyanate AM994 and the photoactivatable aliphatic
azido AM993 analogues
Binding Site Characterization of AM1336, a Novel Covalent Inverse Agonist at Human Cannabinoid 2 Receptor, Using Mass Spectrometric Analysis
Cannabinoid 2 receptor (CB2R), a Class-A G-protein coupled receptor
(GPCR), is a promising drug target under a wide array of pathological
conditions. Rational drug design has been hindered due to our poor
understanding of the structural features involved in ligand binding.
Binding of a high-affinity biarylpyrazole inverse agonist AM1336 to
a library of the human CB2 receptor (hCB2R) cysteine-substituted mutants
provided indirect evidence that two cysteines in transmembrane helix-7
(H7) were critical for the covalent attachment. We used proteomics
analysis of the hCB2R with bound AM1336 to directly identify peptides
with covalently attached ligand and applied in silico modeling for
visualization of the ligand–receptor interactions. The hCB2R,
with affinity tags (FlaghCB2His6), was produced in a baculovirus–insect
cell expression system and purified as a functional receptor using
immunoaffinity chromatography. Using mass spectrometry-based bottom-up
proteomic analysis of the hCB2R-AM1336, we identified a peptide with
AM1336 attached to the cysteine C284(7.38) in H7. The hCB2R homology
model in lipid bilayer accommodated covalent attachment of AM1336
to C284(7.38), supporting both biochemical and mass spectrometric
data. This work consolidates proteomics data and in silico modeling
and integrates with our ligand-assisted protein structure (LAPS) experimental
paradigm to assist in structure-based design of cannabinoid antagonist/inverse
agonists
Novel C‑Ring-Hydroxy-Substituted Controlled Deactivation Cannabinergic Analogues
In pursuit of safer
controlled-deactivation cannabinoids with high
potency and short duration of action, we report the design, synthesis,
and pharmacological evaluation of novel C9- and C11-hydroxy-substituted
hexahydrocannabinol (HHC) and tetrahydrocannabinol (THC) analogues
in which a seven atom long side chain, with or without 1′-substituents,
carries a metabolically labile 2′,3′-ester group. Importantly,
in vivo studies validated our controlled deactivation approach in
rodents and non-human primates. The lead molecule identified here,
namely, butyl-2-[(6a<i>R</i>,9<i>R</i>,10a<i>R</i>)-1-hydroxy-9-(hydroxymethyl)-6,6-dimethyl-6a,7,8,9,10,10a-hexahydro-6<i>H</i>-benzoÂ[<i>c</i>]Âchromen-3-yl]-2-methylpropanoate
(AM7499), was found to exhibit remarkably high in vitro and in vivo
potency with shorter duration of action than the currently existing
classical cannabinoid agonists