CTSB and neoplasm: These authors indicated a preference of their compounds for the inhibition of the selenoenzyme TrxR compared to the cysteine-rich cathepsin B, with the IC50 calculated for TrxR being up to 50-times lower compared with those calculated for cathepsin B. Accordingly, the cytotoxic effects on tumor cell growth were accompanied by an appropriate decrease in cell impedance and cellular respiration.