Discovery of “Molecular Switches” within
a Series of mGlu5 Allosteric Ligands Driven by a “Magic
Methyl” Effect Affording Both PAMs and NAMs with In
Vivo Activity, Derived from an M1 PAM Chemotype
posted on 2021-10-15, 11:25authored byLisa Barbaro, Alice L. Rodriguez, Ashlyn N. Blevins, Jonathan W. Dickerson, Natasha Billard, Olivier Boutaud, Jerri L. Rook, Colleen M. Niswender, P.Jeffrey Conn, Darren W. Engers, Craig W. Lindsley
In the course of
optimizing an M1 PAM chemotype, introduction
of an ether moiety unexpectedly abolished M1 PAM activity
while engendering a “molecular switch” to afford a weak,
pure mGlu5 PAM. Further optimization was able to deliver
a potent (mGlu5 EC50 = 520 nM, 63% Glu Max),
centrally penetrant (Kp = 0.83), MPEP-site binding mGlu5 PAM 17a (VU6036486) that reversed amphetamine-induced
hyperlocomotion. A pronounced “magic methyl” effect
was noted with a regioisomeric methyl congener, leading to a change
in pharmacology to afford a potent (mGlu5 IC50 = 110 nM, 3% Glu Min), centrally penetrant (Kp = 0.94),
MPEP-site binding NAM 28d (VU6044766) that displayed
anxiolytic activity in a mouse marble burying assay. These data further
support the growing body of literature concerning the existence of
G protein-coupled receptor (GPCR) allosteric privileged structures,
and the value and impact of subtle methyl group walks, as well as
the highly productive fluorine walk, around allosteric ligand cores
to stabilize unique GPCR conformations.