HRX-0233 is a small-molecule MAP2K4 inhibitor. HRX-0233 results in strong tumor shrinkage without any apparent toxicity in H358 KRASG12C-mutant non-small cell lung cancers (NSCLC) in vivo. HRX-0233 efficiently prevents feedback activation of receptor tyrosine kinases (RTKs) upon monotherapy KRAS inhibitor Sotorasib and causes a more sustained and complete inhibition of MAPK signaling. HRX-0233 is promising for research of AR-negative prostate cancer , lung and colon cancers.