Background
NKP-1339 is one of the most promising investigational non-platinum metal drugs in clinical development against solid malignancies. Recently, NKP-1339 was evaluated in a clinical phase I trial regarding its safety, tolerability, maximum tolerated dose, pharmacokinetics, and pharmacodynamics. The high tumor targeting potential of NKP-1339 is probably based on delivery to tumor sites by serum proteins such as albumin and transferrin as well as on the activation of the compound in the reductive tumor milieu. The reduction of ruthenium(III) to ruthenium(II) is favoured under hypoxic condition (frequently occurring in solid tumors) and is followed by severe disruption of the cellular redox balance and induction of apoptosis via the mitochondrial pathway.