KRAS and cancer: KRAS has been considered an “undruggable” target and it is difficult to inhibit its intracellular activity [5, 31] for the following reasons [31]: first, whether KRAS adopts an active or inactive form depends on its GTP or GDP binding status rather than it being a substrate of catalytic reactions; second, there is a picomolar affinity between KRAS and GTP while micromolar concentrations of GTP exist in cancer cells; third, KRAS lacks a sufficiently large and deep hydrophobic pocket for small molecule binding, aside from the challenging nucleotide-binding site [4–6, 32].