In vitro competition studies of 3344 binding to KRAS-G12V in waterLOGSY NMR show the anti-RAS scFv inhibits 3344 binding to KRAS. In view of the in vitro inhibition by the anti-RAS scFv of 3344 binding to RASand because the iDAb RAS interferes with BRET signal in cells, 3344 was used for valida?tion of the BRET2 toolbox for RAS-effector PPI inhibitors.