Ruthenium-NHC complexes have been reported as inhibitors of cysteine- and selenocysteine-containing biomolecules, including TrxR and cathepsin B (CatB).18 The latter is a cysteine protease for which elevated expression levels are often associated with the progression of various tumours.19 Additionally, (p-cymene)(NHC)RuCl2 complexes act as antiproliferative agents, with IC50 values frequently in the low micromolar range.20,21. The gene discussed is CTSB; the disease is neoplasm.