However, its inhibitory ability on mitochondrial matrix thioredoxin reductase TrxR2 was weakened, with an IC50 value greater than 100 nmol/L, indicating that the target of gold (I) nitrogen heterocyclic carbene II8-b may be the cytoplasmic thioredoxin reductase TrxR1 in cancer cells [97]. This evidence concerns the gene PRDX5 and cancer.