Transport of therapeutic vanadium and ruthenium complexes by blood plasma components.

Low molecular weight and high molecular weight metal ion binders present in blood plasma are shortly described. The binding of vanadium and ruthenium complexes by these components has received much attention, namely their interactions with human serum albumin and transferrin, and these studies are critically reviewed. The influence of the protein binding on the bioavailability of the prospective drugs, namely on the transport by blood plasma and uptake by cells is also discussed. It is concluded that vanadium compounds are mainly transported in blood by transferrin, but that no study has properly addressed the influence of albumin and transferrin in the vanadium uptake by cells. Ruthenium complexes bind strongly to HSA, most likely at the level of His residues, leading to the formation of stable adducts. If the kinetics of binding to this protein is fast enough, probably they are mainly transported by this serum protein. Nevertheless, at least for a few Ru(III)-complexes, hTf seems to play an active role in the uptake of ruthenium, while HSA may provide selectivity and higher activity for the compounds due to an enhanced permeability effect.

Elucidation of the interactions of an anticancer ruthenium complex in clinical trials with biomolecules utilizing capillary electrophoresis hyphenated to inductively coupled plasma-mass spectrometry. Short communication.

The application of capillary electrophoresis (CE) combined with highly sensitive inductively-coupled-plasma mass spectrometric (ICP-MS) detection allows the interactions of metal complexes with biomolecules to be characterized. This technique has been used to provide new insights into the mode of action of the ruthenium-based anticancer drug candidate indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019). While the compound binds rapidly and efficiently to serum proteins, especially albumin, its reactivity towards the model DNA compound 2'-deoxyguanosine 5'-monophosphate (5'-dGMP) is moderate.

Capillary electrophoresis hyphenated to inductively coupled plasma-mass spectrometry: a novel approach for the analysis of anticancer metallodrugs in human serum and plasma.

The development of metal-based chemotherapeutics lacks methods which are capable of providing early indication on the potential of new metal complexes as future anticancer drugs. Since most of these compounds are administered intravenously, serum proteins are the first available biological binding partners in the bloodstream. For platinum-based anticancer drugs the interaction with serum proteins is regarded as an important contribution to the side effects accompanying chemotherapy. In contrast, newly developed ruthenium compounds are thought to be transported into the tumor in a protein-bound form. In here, the application of CE hyphenated to inductively coupled plasma (ICP)-MS, applying Polybrene-coated capillaries, is demonstrated for studying the interaction of indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) with HSA and transferrin, which are important transport proteins. Furthermore, the applicability of the method to human serum and plasma and, more importantly, to real-world patient samples was proven. KP1019 was found to bind to a high degree to HSA both in serum, plasma and the patient samples. Only minor fractions of ruthenium were found attached to other proteins.

Probing the stability of serum protein-ruthenium(III) drug adducts in the presence of extracellular reductants using CE.

A CE kinetic assay was developed to study the stability of the adducts of a novel ruthenium(III)-based anticancer agent with serum proteins under simulated reductive physiological conditions. Formation of the reactive Ru(II) species and their release from the serum proteins are thought to play an important role in the mode-of-action of indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) which has successfully finished a clinical phase I study. The CE method was adapted, in zone electrophoresis and affinity CE modes, to make obvious that such transformation would take place in the hypoxic tumor tissue rather than in the bloodstream. Indeed, no measurable effect of extracellular concentration levels of glutathione incorporated into the BGE on the UV signals of albumin and transferrin adducts was observed over 30 min of examination. Incubation of the KP1019-albumin adduct with the major blood reducing agent, ascorbic acid, revealed no changes in the continuously monitored peak areas (average corrected responses were 9.56 +/- 0.86 and 9.87 +/- 0.60 mAU for the adduct and its mixtures with ascorbic acid in the physiological range of 1 x 10(-5) -8 x 10(-5) M, respectively). On the other hand, both the transferrin adduct and transferrin itself accelerated the oxidation of ascorbic acid; however, the oxidation rate constants measured by CE were virtually the same: (19.1 +/- 4.4) x 10(-3) and (18.2 +/- 5.0) x 10(-3) min(-1), respectively. In order to confirm more unambiguously the stability of KP1019-protein adducts in the presence of ascorbic acid (UV absorbance detection does not distinguish the adduct and protein signals), CE with inductively coupled plasma (ICP) MS detection was applied to follow metal-selectively the signal of bound ruthenium, which remained unaffected by this reducing agent. This work appears the first to present the application of CE to the stability studies of the protein-bound metallodrugs.

Influence of the chemical form on the plasma clearance of ruthenium in humans.

The radioisotopes of ruthenium (103Ru and 106Ru) are abundant fission products and represent a radiological risk for the population in case of nuclear accidents. Few biokinetic studies have been performed on humans up to now and consequently the current model recommended by ICRP for ruthenium is derived mainly by extrapolation from animal data. The stable isotope 101Ru and proton activation analysis have been used to study the biokinetics of Ru in blood plasma samples taken during 8 studies in three healthy volunteers. The results obtained demonstrated that complexed Ru (in the form of citrate Ru(IV) complexes) is cleared from blood plasma very rapidly (characteristic half time of 17+/-2 min), while inorganic Ru remains longer in the systemic circulation, and is transferred to other organs and/or excreted with a biological half time of 23+/-2h. Good reproducibility of the clearance curves indicated no evidence of inter- or intra-individual variability when the same Ru solution was injected in repeated experiments to different subjects.