Structure-Enabled Discovery of Novel Macrocyclic Inhibitors Targeting Glutaminase 1 Allosteric Binding Site

The
inhibition of glutaminase 1 (GLS1) represents a potential treatment
of malignant tumors. Structural analysis led to the design of a novel
series of macrocyclic GLS1 allosteric inhibitors. Through extensive
structure–activity relationship studies, a promising candidate
molecule 13b (LL202) was identified with
robust GLS1 inhibitory activity (IC50 = 6 nM) and high
GLS1 binding affinity (SPR, Kd = 24 nM;
ITC, Kd = 37 nM). The X-ray crystal structure
of the 13b–GLS1 complex was resolved, revealing
a unique binding mode and providing a novel structural scaffold for
GLS1 allosteric inhibitors. Importantly, 13b clearly
adjusted the cellular metabolites and induced an increase in the ROS
level by blocking glutamine metabolism. Furthermore, 13b exhibited a similar in vivo antitumor activity
as CB839. This study adds to the growing body of evidence
that macrocyclization provides an alternative and complementary approach
for the design of small-molecule inhibitors, with the potential to
improve the binding affinity to the targets.