Book excerpt: KRAS Drug Discovery: Past, Present and Future is a comprehensive overview of the state-of-the-art medicinal chemistry approaches towards targeting the formerly undruggable oncogene, KRAS. It includes Seminal medicinal chemistry case histories of KRASG12C inhibitors such as Sotorosib, the first approved KRASG12C inhibitor for NSCLC, alongside the latest advances towards identification of in vivo tools and development candidates targeting KRAS G12D, KRAS G13C and other mutations. The book also provides the reader with a comprehensive overview of the in vitro assay systems, in vivo pharmacology xenograft models and chemical biology tools available to characterize small molecule inhibitors of KRAS.