Title:Targeting of SOS1: from SOS1 Activators to Proteolysis Targeting Chimeras
Volume: 29
Issue: 22
Author(s): Gerhard Hamilton*, Sandra Stickler and Barbara Rath
Affiliation:
- Institute of Pharmacology, Medical University of Vienna, Vienna, A-1090, Austria
Keywords:
KRAS, SOS1, PROTAC, agonist, inhibitors, proteasome.
Abstract: The most frequent mutated oncogene KRAS in lung cancer is targeted by KRAS G12C-directed
drugs, such as Sotorasib and Adagrasib. Still, other alleles frequently expressed in pancreatic and colon cancer
may be attacked indirectly by hitting the guanine nucleotide exchange factor (GEF) SOS1 that loads and activates
KRAS. The first modulators of SOS1 were found to act as agonists and defined a hydrophobic pocket at
the catalytic site. High throughput screenings resulted in the detection of SOS1 inhibitors Bay-293 and BI-3406
comprising amino quinazoline scaffolds optimized for binding to the pocket by various substituents. The first
inhibitor, BI-1701963, is in clinical studies alone or in combination with a KRAS inhibitor, a MAPK inhibitor
or chemotherapeutics. An optimized agonist, VUBI-1, shows activity against tumor cells by destructive overactivation
of cellular signaling. This agonist was used to formulate a proteolysis targeting chimera (PROTAC),
that labels SOS1 for degradation by proteasomal degradation through a linked VHL E3 ligase ligand. This
PROTAC exhibited the highest SOS1-directed activity due to target destruction, recycling and removal of
SOS1 as a scaffolding protein. Although other first PROTACs have entered clinical trials, each conjugate must
be meticulously adapted as an efficient clinical drug.