Novel CNS-penetrant SOS1 inhibitors enhance KRASG12C inhibitor efficacy by deepening tumor response in mice
Background
KRAS-dependent cancers, particularly colorectal cancer, represent a significant therapeutic challenge due to the oncogenic nature of mutated KRAS. Son of Sevenless Homologue 1 (SOS1) acts as a key guanine nucleotide exchange factor (GEF) for RAS, making it an attractive target to indirectly inhibit KRAS signaling. Current standard-of-care often faces limitations in efficacy and the ability to penetrate the central nervous system (CNS), which is crucial for treating brain metastases. Developing potent, selective, and CNS-penetrant SOS1 inhibitors is essential to overcome these hurdles and improve outcomes in RAS/MAPK pathway-driven malignancies.
Study Design
Researchers initiated a focused high-throughput screening (HTS) triage, identifying a singular SOS1 inhibitor series with a pyridyl core. Structure-based design was then applied to optimize these compounds, building into a buried lipophilic pocket. Strategic fluorination of aryl rings and substituents was employed to generate analogues with favorable physicochemical properties. Multiple SOS1 inhibitor analogues were subsequently progressed into in vivo PK/PD studies in mice, where their efficacy was evaluated both alone and in combination with a KRASG12C inhibitor. Primary endpoints included reductions in DUSP6 mRNA and phosphorylated ERK levels in tumors.
Results
The structural optimization efforts, particularly the conformational preference of the diamide pyridyl core, were critical for binding potency, favoring pyrazine and pyridyl motifs. Structure-based design led to a significant 50-fold potency enhancement for the optimized compounds. Strategic fluorination successfully generated analogues with favorable dipoles, low P-gp and BCRP efflux, and high rat Kpu,u, indicating excellent CNS penetration potential. In in vivo PK/PD studies, combination therapy with the novel SOS1 inhibitors and a KRASG12C inhibitor demonstrated superior efficacy. > Combination-treated tumors in mice showed deeper, more sustained reductions in DUSP6 mRNA and phosphorylated ERK compared to treatment with the KRASG12C inhibitor alone, signifying enhanced MAPK pathway inhibition.
Key Findings
- Structure-based design achieved a 50-fold potency enhancement for novel SOS1 inhibitors.
- Strategic fluorination yielded compounds with favorable dipoles, low P-gp/BCRP efflux, and high rat Kpu,u.
- Combination of SOS1 inhibitors with a KRASG12C inhibitor led to deeper, more sustained reductions in
DUSP6 mRNA. - Combination therapy also resulted in more sustained reductions in
phosphorylated ERKin mouse tumors.
Why It Matters
This discovery of CNS-penetrant SOS1 inhibitors offers a crucial advancement for patients with KRAS-driven cancers, especially those with or at risk of brain metastases. Combining these novel SOS1 inhibitors with existing RAS or MAPK pathway inhibitors could significantly enhance antitumor responses, potentially leading to more durable remissions and improved survival. The favorable pharmacokinetic profile, including low efflux and high CNS penetration, suggests these compounds could address a critical unmet need in oncology. This research paves the way for future clinical trials to validate these promising preclinical findings and establish new, more effective combination protocols for KRAS-mutant malignancies.
sos1-inhibitor
kras-dependent-cancer
cns-penetrant
combination-therapy
preclinical-animal
oncology