SOS1 and cancer: Son of sevenless homolog 1 (SOS1), a guanine nucleotide exchange factor (GEF), catalytically promotes the activation of RAS which in turn consecutively enhances the GEF function of SOS1.306 Targeting SOS1 to disturb its interaction with KRAS in tumors is referred to as an effective way to inhibit a wide panel of KRAS-driven cancers.930,981,982 Multiple SOS1 inhibitors have been developed, mainly including quinazoline-based SOS1 inhibitors such as BAY-293 and BI-3406.