Activity-based protein profiling using 268-TCO, a trans-cyclooctene (TCO)-derivatized analogue of the pan-RAF DFG-out inhibitor LF-268, to characterize intracellular target engagement in live HCT-116 (mutant KRAS/WT RAF) cells. Cells were pre-treated with LF-268 (5 µM) or DMSO as competitor, followed by treatment with 268-TCO probe. After lysis, probe-bound protein complexes were captured via click chemistry using tetrazine (Tz)-coupled sepharose beads. Enriched proteins were identified and quantified by label-free LC-MS/MS.