Comparison of the reactivity of oxaliplatin, pt(diaminocyclohexane)Cl2 and pt(diaminocyclohexane1)(OH2)2(2+) with guanosine and L-methionine

A new bis-pyrazolylpyridine ruthenium(III) complex as a potential anticancer drug: in vitro and in vivo activity in murine colon cancer

We synthesized and characterized the ruthenium(iii) pincer-type complex [RuCl3(H2Lt-Bu] (H2Lt-Bu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine, 1) by elemental analysis, IR and UV-Vis spectroscopy, and the mass spectrometry (MS) method ESI Q-TOF. For comparison reasons, we also studied ruthenium(iii) terpyridine complexes of the general formula [Ru(N-N-N)Cl3], where N-N-N = 4'-chloro-terpyridine (Cl-tpy; 2) or 4'-chlorophenyl-terpyridine (Cl-Ph-tpy; 3). A kinetic study of the substitution reactions of 1-3 with biomolecules showed that the rate constants depend on the properties of the spectator ligand and the nature of the entering nucleophile. The DNA/HSA binding study showed that in comparison to complex 1 (bis-pyrazolylpyridine), the other two (2 and 3) terpyridine complexes had a slightly better binding affinity to calf thymus DNA (CT DNA), while in the case of human serum albumin (HSA), complex 1 exhibited the strongest quenching ability. We demonstrated that 1 possesses significant in vitro cytotoxic activity against mouse colon carcinoma CT26 cells and in vivo antitumor activity in murine heterotopic colon carcinoma. Complex 1 induced G0/G1 cell cycle arrest and apoptotic death in CT26 cells. Additionally, 1 showed antiproliferative activity, as evaluated by the detection of the expression levels of the Ki67 protein. Furthermore, the in vivo results showed that 1 reduced primary tumour growth and the number and growth of lung and liver metastases, significantly prolonging the treated mice's survival rate. This study highlighted that 1 does not show hepato- and nephrotoxicity. Our data demonstrated the considerable antitumor activity of the ruthenium(iii) pincer complex against CT26 tumour cells and implicated further investigations of its role as a potential chemotherapeutic agent for colon carcinoma.

Stability of calcium levofolinate, 5-fluorouracil and oxaliplatin (FOLFOX) mixture

FOLFOX is the most common chemotherapy combination prescribed in colorectal cancer. It is composed of calcium levofolinate, 5-fluorouracil and oxaliplatin which demonstrated synergistic outcome. Nowadays, the lack of all-in-one formulation is due to the chemical composition of the pharmaceutical products and the highly pH-dependent stability of each drug. Herein, we aimed to investigate the stability of a ternary mixture of 5-fluorouracil, oxaliplatin and calcium levofolinate, knowing that coadministering these drugs would improve their efficacy. The effect of three pHs (5.0, 6.0 and 7.5) and two drug concentrations (8/3/6 and 1/1/1 mg/ml for 5-fluorouracil, oxaliplatin and calcium levofolinate, respectively) were examined. A high-performance liquid chromatography method was developed to separate and quantify the three drugs in one run. At higher concentrations, the ternary mixture was unstable regardless of pH. By reducing concentration, drug stability and compatibility in the mixture was improved at pH 5.0 for up to 3 days at +5°C ± 3 °C. In addition, binary mixtures provided stable properties at defined pHs. 5-fluorouracil/oxaliplatin mixture was stable at pH 5.0 over 48 hours while 5-fluorouracil/calcium levofolinate mixture was stable at pHs 6.0 and 7.5 up to 7 days.

Management of extravasation of oxaliplatin by mimicking its biotransformation

Although oxaliplatin (Oxali) plays a key role in the treatment of many types of cancer and has been reported to be an irritant, there is no specific and effective method for its extravasation and failure in Oxali extravasation management results in the need for plastic surgery. In the body, Oxali bio-transforms upon dilution in chloride-containing buffer salts to its di-chloro derivative and loses an oxalate molecule. Consequently, the chloride ions exchange with water molecules in the intracellular environment to produce the di-aqua derivative, which is the most active biotransformation product of Oxali in terms of forming the DNA adducts. Thus, inhibiting transformation of di-chloro to di-aqua derivatives by accumulating chloride ions at the site of extravasation and saturating the Oxali molecule with these ions is a strategy that could help manage extravasation. Injecting normal saline at this site is a simple yet effective way to achieve this goal.

New Pt-NNSO core anticancer agents: Structural optimization and investigation of their anticancer activity

A series of new platinum Pt(II) compounds possessing a bidentate leaving ligand modified from oxaliplatin has been synthesized, with one of the oxygen ligating atom substituted for a sulphur atom (resulting in a Pt-NNSO coordination core structure). The general structures are R,R-diaminocyclohexane (DACH)-Pt-(methylthio)acetic acid (K4) and DACH-Pt-(thiophenylacetic acid) (K4 derivatives). Substitution of an electron donating or withdrawing group at the ortho or para position on the phenyl ring of K4 derivatives was found to affect the complexes' stability, reactivity with the biological molecules (5'-guanosine monophosphate (5'-GMP) and L-methionine (L-Met)) and anticancer activity. ¹H NMR experiments demonstrated that Pt-NNSO complexes formed a mixture of mono- and diadduct with 5'-GMP in various ratios, which are different from the classical Pt drugs (forming mainly diadduct). In addition, all of the K4 derivatives with improved lipophilicity are less deactivated by L-Met in comparison to cisplatin (CDDP) and oxaliplatin. Biological assessments showed that all Pt-NNSO complexes are less toxic than CDDP in normal porcine kidney cells and are minimally affected by drug resistance. Some of the new compounds also displayed comparable anticancer activity to CDDP or better than carboplatin in a few cancer cell lines. The lower reactivity of the Pt-NNSO compounds than CDDP towards thiol molecules, presumably leading to less efflux in resistant cancer cells, and the ability to inhibit autophagy were believed to allow the new compounds to be less affected by Pt resistance.

Particle-water interactions of platinum-based anticancer drugs in river water and estuarine water

The cytotoxic, platinum-based anticancer drugs, cisplatin, carboplatin and oxaliplatin, enter the aquatic environment largely in municipal wastes via excretion from outpatients undergoing chemotherapy. The environmental behaviour, effects and fate of these drugs are, however, unknown. In this study, the adsorption of the drugs to untreated and chemically modified (oxide-free and organic-free) sediment was examined in both river water and low salinity (S=3.2) estuarine water in order to determine the nature and extent of their interactions with suspended particles. In all cases, adsorption isotherms were linear, and the slopes of the relationships, or distribution coefficients (KDs), ranged from about 10(2) to 10(3) ml g(-1). Overall, adsorption decreased in the order: cisplatin>carboplatin>oxaliplatin; in river water and: cisplatin>carboplatin, oxaliplatin; in estuarine water. There was no clear dependence of adsorption on sediment treatment but, for all sediment types, both cisplatin and carboplatin adsorption was greater in river water than in estuarine water. Qualitatively, these observations are consistent with the rates of formation of reactive, aquated degradation products and the dependencies of these rates on aqueous chloride concentration. We predict that during transport through an estuarine turbidity maximum (of suspended sediment concentration=1 g L(-1)), up to about 45% of cisplatin and 35% of carboplatin are filtered out from the aqueous phase but that no more than 7% of oxaliplatin is retained.

Oxaliplatin and its enantiomer induce different condensation dynamics of single DNA molecules

The interactions of DNA with oxaliplatin (Pt(R,R-DACH)) or its enantiomer (Pt(S,S-DACH)) were investigated using magnetic tweezers and atomic force microscope. In the process of DNA condensation induced by Pt-DACH, only diadducts and micro-loops are formed at low Pt-DACH concentrations, while at high Pt-DACH concentrations, besides the diadducts and micro-loops, long-range cross-links are also formed. The diadduct formation rate of Pt(R,R-DACH) is higher than that of Pt(S,S-DACH). However, the proportions of micro-loops and long-range cross-links for Pt(S,S-DACH) are higher than those for Pt(R,R-DACH). We propose a model to explain these differences between the effect of Pt(R,R-DACH) and that of Pt(S,S-DACH) on DNA condensation. The study has strong implications for the understanding of the effect of chirality on the interaction between Pt-DACH and DNA and the kinetics of DNA condensation induced by platinum complexes.

A complex of cyclohexane-1,2-diaminoplatinum with an amphiphilic biodegradable polymer with pendant carboxyl groups

A biodegradable and amphiphilic copolymer, MPEG-b-P(LA-co-MCC), which contains pendant carboxyl groups, was chosen as a drug carrier for the active anticancer part (DACH-Pt) of oxaliplatin to form an MPEG-b-P(LA-co-MCC/Pt) complex. It was able to self-assemble into micelles with a mean diameter of 30-40 nm, and a surface potential near -10 mV. The typical platinum content was 10 wt.%. The micelles showed acid-responsive drug release kinetics, which is beneficial for drug release in the intracellular environment. The Pt(II) species were released mainly in the form of DACH-Pt-Cl(2) in 150 mM NaCl solution and DACH-Pt(2+)-(H(2)O)(2) in pure water according to the results obtained by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. In vitro evaluation showed that the micelles displayed the same or higher cytotoxicities against SKOV-3, HeLa, and EC-109 cancer cells compared with oxaliplatin. The enhanced cytotoxicity against SKOV-3 cells is attributed to effective internalization of the micelles by the cells via endocytosis and the sensitivity of SKOV-3 cells to platinum drugs. This novel biodegradable and amphiphilic copolymer-based platinum drug will have great potential application in clinical use.

Effect of reactivity on cellular accumulation and cytotoxicity of oxaliplatin analogues

The purpose of this study was to systematically investigate the relationships between reactivity, cellular accumulation, and cytotoxicity of a panel of oxaliplatin analogues with different leaving groups in human carcinoma cells. The reactivity of the complexes towards the nucleotides 2'-deoxyguanosine 5'-monophosphate and 2'-deoxyadenosine 5'-monophosphate was studied using capillary electrophoresis. Cellular accumulation and cytotoxicity were measured in an oxaliplatin-sensitive and oxaliplatin-resistant ileocecal colorectal adenocarcinoma cell line pair (HCT-8/HCT-8ox). Platinum concentrations were determined by flameless atomic absorption spectrometry. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess cytotoxicity. Early cellular platinum accumulation was predominantly affected by lipophilicity. A relationship between reactivity and cellular accumulation was observed for three of four platinum complexes investigated, whereas the most lipophilic oxaliplatin analogue was an exception. Increased reactivity and reduced lipophilicity were associated with high cytotoxic activity. Resistance was influenced by lipophilicity but not by reactivity. The observed relationships may help in the design of analogues with high antitumoral activity in oxaliplatin-sensitive as well as oxaliplatin-resistant cells.

Laser desorption and ionization time-of-flightversus matrix-assisted laser desorption and ionization time-of-flight mass spectrometry of and metal complexes

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been recently established as a powerful, "soft" ionization technique for the analysis of both transition metal complexes, which are used as metallo-drugs in the therapy of various types of tumors, and biomolecules. Since some metal complexes absorb light in the UV range, it should be possible to analyse them without additional matrices, i.e. using LDI-TOF MS. In this study, the matrix-free approach was tested for the analysis of [PtCl2(dach)] (dichloride(1,2-diamincyclohexane) platinum(ii)), [RuCl2(en)2]Cl (dichloridobis(ethylenediamine) ruthenium(iii) chloride) and [RuCl2(bipy)2]Cl (bis(bipyridine)dichloridoruthenium(iii) chloride) and the detection limit for these compounds was determined. In summary, the LDI-TOF mass spectra of [PtCl2(dach)] and [RuCl2(en)2]Cl are rather simple, whereas in the presence of 2,5-DHB as a matrix, additional peaks are generated. On the other hand, the standard MALDI-TOF mass spectrum of [RuCl2(bipy)2]Cl exhibits only one peak arising from the complex, in contrast to six peaks detectable in the LDI-TOF mass spectrum. The detection limit in the MALDI-TOF MS analysis of [PtCl2(dach)] and [RuCl2(bipy)2]Cl complexes was lower than that determined in LDI-TOF MS. Taking all into account, in this paper, we have demonstrated some advantages and drawbacks of the matrix-free LDI-TOF mass spectrometric analysis of transition metal complexes.

Matrix-assisted laser desorption/ionization imaging mass spectrometry of oxaliplatin derivatives in heated intraoperative chemotherapy (HIPEC)-like treated rat kidney

Oxaliplatin [1,2-diaminocyclohexane (dach)-Pt complex] is a platinum anticancer drug which is mainly used in the treatment of advanced colorectal cancer, particularly in Heated Intraoperative Chemotherapy (HIPEC) for the treatment of colorectal peritoneal carcinomatosis. In order to better understand the penetration of oxaliplatin in treated tissues we performed a direct imaging of tissue sections from HIPEC-like treated rat kidney using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. This procedure allowed the detection and localization of oxaliplatin and its metabolites, the monocysteine and monomethionine complexes, in kidney sections. Specifically, oxaliplatin and its metabolites were localized exclusively in the kidney cortex, suggesting that it did not penetrate deeply into the organ. Based on these results, an imaging analysis of human tumors collected after HIPEC is currently in progress to assess the distribution of oxaliplatin and/or metabolites with the aim of defining clinical conditions to improve drug penetration.

Oxaliplatin pharmacokinetics and pharmacodynamics in adult cancer patients with impaired renal function

PURPOSE

To characterize the pharmacokinetics and pharmacodynamics of oxaliplatin in cancer patients with impaired renal function.

EXPERIMENTAL DESIGN

Thirty-four patients were stratified by 24-h urinary creatinine clearance (CrCL) into four renal dysfunction groups: group A (control, CrCL, >or=60 mL/min), B (mild, CrCL, 40-59 mL/min), C (moderate, CrCL, 20-39 mL/min), and D (severe, CrCL, <20 mL/min). Patients were treated with 60 to 130 mg/m2 oxaliplatin infused over 2 h every 3 weeks. Pharmacokinetic monitoring of platinum in plasma, plasma ultrafiltrates, and urine was done during cycles 1 and 2.

RESULTS

Plasma ultrafiltrate platinum clearance strongly correlated with CrCL (r2 = 0.712). Platinum elimination from plasma was triphasic, and maximal platinum concentrations (Cmax) were consistent across all renal impairment groups. However, only the beta-half-life was significantly prolonged by renal impairment, with values of 14.0 +/- 4.3, 20.3 +/- 17.7, 29.2 +/- 29.6, and 68.1 h in groups A, B, C, and D, respectively (P = 0.002). At a dose level of 130 mg/m2, the area under the concentration time curve increased in with the degree of renal impairment, with values of 16.4 +/- 5.03, 39.7 +/- 11.5, and 44.6 +/- 14.6 mug.h/mL, in groups A, B, and C, respectively. However, there was no increase in pharmacodynamic drug-related toxicities. Estimated CrCL using the Cockcroft-Gault method approximated the measured 24-h urinary CrCL (mean prediction error, -5.0 mL/min).

CONCLUSIONS

Oxaliplatin pharmacokinetics are altered in patients with renal impairment, but a corresponding increase in oxaliplatin-related toxicities is not observed.

Analysis of cytotoxicities of platinum compounds

Extent of DNA platination, loss of cell viability, DNA fragmentation, and impairment of cellular mitochondrial oxygen consumption are measures of drug cytotoxicity. We measured and compared these effects for cisplatin, oxaliplatin and carboplatin. Because reaction with intracellular thiols may be responsible for drug resistance, we also determined the rates of Pt drug reactions with metallothionein. Jurkat cells were exposed at 37 degrees C to 25 microM Pt drugs for 3 h. Pt-DNA adducts were determined at the end of the incubation period by atomic absorption spectroscopy. Viability, DNA fragmentation, and cellular respiration (microM O2/min/10(6) cells) were determined 24 h post drug exposure. The average amount of Pt-DNA adducts (Pt atoms/10(6) nucleotides) produced by cisplatin was 43.4, by oxaliplatin 4.8 and by carboplatin 1.5. Cisplatin decreased the rate of respiration by approximately 63% and oxaliplatin by approximately 37%. DNA fragmentation by cisplatin and oxaliplatin was very similar. Carboplatin produced an unnoticeable effect on cellular respiration, and only approximately 10% of the DNA fragmentation was produced by cisplatin or oxaliplatin. Although, for a given drug, all four measures of cytotoxicity were proportional, this did not hold for comparisons between the drugs. The rate constants (M-1 s-1) for reaction of cisplatin, oxaliplatin and carboplatin with Cd/Zn thionein were 0.75, 0.44 and 0.012, respectively. For comparison, the rate constants (M-1 s-1) for reaction of cisplatin, oxaliplatin and carboplatin with glutathione were 0.027, 0.038 and 0.0012, respectively. The low reactivity of carboplatin with metallothionein and glutathione suggests that its low cytotoxic activities are not due to reaction of Pt2+ with cellular thiols. Despite a tenfold difference in Pt-DNA adducts between cisplatin and oxaliplatin, the cytotoxicities of these compounds are very similar, suggesting that oxaliplatin lesions are more potent than cisplatin lesions. The results demonstrate a large influence of the ligands occupying Pt coordination spheres on the chemical and biologic activities of Pt drugs.

Determination of oxaliplatin in human plasma and plasma ultrafiltrate by graphite-furnace atomic-absorption spectrometry

A method for sensitive determination of the anti-cancer agent oxaliplatin in human plasma and human plasma ultrafiltrate (pUF) is presented. The method is based on the quantification of platinum by graphite-furnace atomic-absorption spectrometry, with Zeeman correction and an atomisation temperature of 2,700 degrees C. Sample pretreatment involves dilution of the samples with a solution containing 0.15 mol L(-1) NaCl and 0.20 mol L(-1) HCl in water. Validation was performed in accordance with the most recent FDA guidelines for bioanalytical method validation. All results were within requirements. The validated ranges of quantification were 0.10-400 micromol L(-1) for human pUF and 0.50-400 micromol L(-1) for plasma. The assay is now successfully used to support pharmacokinetic studies of cancer patients treated with oxaliplatin.

Novel molecular drug carrier: encapsulation of oxaliplatin in cucurbit[7]uril and its effects on stability and reactivity of the drug

Oxaliplatin forms a stable 1:1 inclusion complex with cucurbit[7]uril as indicated by NMR, mass spectrometry, isothermal titration calorimetry and X-ray crystallography. The encapsulation of the drug results in a large enhancement in stability, a moderate decrease in reactivity toward guanosine but a much larger decrease in reactivity toward L-methionine, which suggests the encapsulation not only increases the stability of the drug but also may reduce unwanted side effects caused by protein binding of the platinum drug. A preliminary in vitro assay using various tumor cell lines reveals that the encapsulation results in a decrease in the antitumor activity of oxaliplatin.

Polyamidoamine (Yet Not PAMAM) dendrimers as bioinspired materials for drug delivery: structure-activity relationships by molecular simulations

In this paper, we report the results obtained from a comprehensive characterization of newly synthesized dendrimeric molecules in a solvated environment, by computer-aided simulations. The evidences allowed us to formulate some structure-activity relationships (SARs) between the experimentally verified cytotoxicity/noncytotoxicity of these compounds and some molecular features such as, for instance, radius of gyration, molecular shape, and dimensions. In particular, all noncytotoxic dendrimers were characterized by a more dense and globular shape and by a smoother surface pattern, as quantified by their fractal dimension D.

Kinetic Study on the Reactions of Platinum Drugs with Glutathione

The binding of platinum (Pt) drugs (oxaliplatin, carboplatin, and cisplatin) to glutathione (GSH, 6.75 mM) was investigated at 37 degrees C in Hepes (100 mM, pH approximately 7.4) or Tris-NO(3) (60 mM, pH 7.4) buffer and NaCl (4.62, 6.63, or 7.82 mM). The conditions were chosen to mimic passage of clinical concentrations of the drugs (135 microM) through the cytosol. The reactions were monitored by UV-absorption spectroscopy, high-performance liquid chromatography (HPLC), and atomic absorption spectroscopy. The initial rates, detected by UV absorbance, were similar for oxaliplatin and cisplatin reacting with GSH and were more than 5-fold faster than for carboplatin reacting with GSH. The Pt contents in HPLC eluates corresponding to unbound drug decreased exponentially with time, confirming that the reactions were first order in [Pt drug] and allowing determination of the pseudo first-order rate constants (k(1)). The second-order rate constants (k(2)) were calculated as k(1) divided by [GSH]. The k(2) value for oxaliplatin reacting with GSH was approximately 3.8 x 10(-2) M(-1) s(-1), for cisplatin reacting with GSH approximately 2.7 x 10(-2) M(-1) s(-1), and for carboplatin reacting with GSH approximately 1.2 x 10(-3) M(-1) s(-1) (approximately 32-fold slower than that of oxaliplatin and approximately 23-fold slower than that of cisplatin). These results demonstrate an influence of ligands surrounding the Pt coordination sphere on the reactivity of Pt(2+) with GSH.