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Progressive vaccinia: immunological aspects and transfer factor therapy.

Progressive vaccinia is a rare and serious complication of smallpox vaccination. Depressed immune function can generally be found as an underlying disorder; thus adequate immuno-correction may be expected to be therapeutically effective. Humoral and cell-mediated immunity was repeatedly examined in one case throughout the course of the disease. Results indicated partial deficiency of cell-mediated immunity. No therapeutic effect was achieved by using human antivaccinia immunoglobulin and N-methylisatin beta-thiosemicarbazone. Transfer factor therapy was also attempted. Treatment with a non-specific transfer factor preparation was followed by a transitory clinical improvement. A specific transfer factor preparation given during the last month of life, however, had no therapeutic effect. The patient died on the 145th day after vaccination. Autopsy findings pointed to combined immune deficiency.

Humans↗

62Cu-PTSM and PET used for the assessment of angiotensin II-induced blood flow changes in patients with colorectal liver metastases.

The aim of this study was to establish a quantitative positron emission tomography (PET) method for investigating angiotensin II (AII)-induced changes in blood flow distribution in the liver. This was in order to evaluate the role of vascular manipulation applied to locoregional chemotherapy treatment in patients with colorectal liver metastases. The tracer selected was copper-62 (II) pyruvaldehyde bis-(N4-methyl)thiosemicarbazone (62Cu-PTSM), which exhibits high first-pass extraction and tissue retention following intra-arterial administration. The short half-life of the tracer and its availability from a 62Zn/62Cu generator enabled short-interval repeat PET scans on patients in a single imaging session. Distribution of tracer within the liver was imaged in a single view using a PET camera with rotating large-area detectors. By optimisation of the acquisition protocol, it was possible to acquire sufficient data to produce good-quality images and to quantify tracer uptake with an accuracy of <10%. Reproducibility of the imaging method was assessed in a single patient in whom three consecutive 62Cu-PTSM PET scans were obtained, and in whom no vascular manipulation was performed. Sets of scans (before, during and immediately after a 45-min AII infusion) were obtained in nine patients to assess blood flow changes associated with prolonged vascular manipulation. Significant individual responses, varying in both the magnitude and the duration of flow change, were observed in the majority of cases (7/11 lesions; 7/9 patients). These findings illustrate the potential of 62Cu-PTSM and PET for pharmacological studies. The wide range of individual patient responses to AII infusion suggests that PET blood flow assessment would be of value for selecting patients in whom this procedure may be effective.

Algorithms↗

Design of hypoxia-targeting radiopharmaceuticals: selective uptake of copper-64 complexes in hypoxic cells in vitro.

The well-known perfusion tracer CuPTSM, labelled with 62Cu or 64Cu, is believed to be trapped in cells non-selectively by a bioreductive mechanism. It is proposed that by modifying the ligand to increase its electron donor strength (for example by adding alkyl functionality or replacing sulphur ligands with oxygen ligands), the copper complexes will become less easily reduced and tracers with selectivity for hypoxic tissues could thus be developed. The aim of this work was to prepare 64Cu-labelled complexes of two series of ligands, based on the bis(thiosemicarbazone) (13 ligands) and bis(salicylaldimine) (3 ligands) skeletons, and to evaluate the hypoxia dependence of their uptake in cells. The complexes were incubated with Chinese hamster ovary cells under normoxic and hypoxic conditions, and the cells isolated by centrifugation to determine radioactivity uptake at various time points up to 90 min. Several members of both series demonstrated significant (P<0.05) or highly significant (P<0.01) hypoxia selectivity, indicating that both series of complexes offer a basis for development of hypoxia-targeting radiopharmaceuticals for positron emission tomography (60Cu, 61Cu, 62Cu, 64Cu) and targeted radiotherapy (64Cu, 67Cu).

Animals↗

Mononuclear and dinuclear complexes of 99mTc.

In the labeling of penicillamine (Pen) with 99mTc, various complexes were detected. Studies of the conditions for differentiating the product formed in order to understand the chemical and biological behavior were carried out. Marked roles of pH and SnCl2 concentration were observed. Controlled delivery of Sn2+ ion was obtained with the tin-adsorbed resin (Sn-resin) developed. Radiopharmaceutical and biological characterization of mononuclear and dinuclear complexes of Tc-Pen, under given sets of labeling condition, were established. Those studies provided a good basis in technetium chemistry which facilitated the development of new Tc-radiopharmaceuticals. Selection of the appropriate ligand offered a stable mononuclear complex of Tc-bleomycin for tumor detection, Tc-Pen-ethyl-ester for blood-element labeling and, above all, development of a bis-thiosemicarbazone derivative as a new bifunctional chelating agent to be coupled to proteins, fatty acids, glucose etc. On the other hand, various cholescintigraphic agents were better conceived of as dinuclear complexes and this created the possibility of generating a new agent, a phthalein derivative, Tc-PC, containing the required coordination environment for the technetium to be bridged in a dinuclear state.

Bleomycin↗

Metal chelators as potential antiviral agents.

Metal-chelating compounds can inhibit virus-induced enzymes in infected cells by coordinating with metal ions at their active sites. Consideration of the coordinating properties of ligands can explain the antiviral activity of these compounds. The antiviral actions of a number of compounds (e.g., thiosemicarbazones, pyrophosphate analogues, beta-diketones, cyclic polyethers and flavanoids) are discussed in the light of their metal-chelating properties.

Antiviral Agents↗

Inhibition of human immunodeficiency virus by N-methylisatin-beta 4':4'-diethylthiosemicarbazone and N-allylisatin-beta-4':4'-diallythiosemicarbazone.

N-methylisatin-beta 4':4'-diethylthiosemicarbazone(M-IBDET) and N-allylisatin-beta-4':4'-diallylthiosemicarbazone(A-IBDAT ) inhibit the production of Human Immunodeficiency virus (HIV). Virus inhibition was related to the thiosemicarbazone derivative (TSCD) concentrations and time of treatment. Inhibition of HIV production was confirmed by various parameters of virus assay employing reverse transcriptase activity, plaque forming units (PFU) and levels of viral structural proteins. Effective antiviral TSCD concentrations ranged from 0.17 microM to 2.04 microM for M-IBDET, and from 1.45 microM to 17.4 microM for A-IBDAT. Treatment of the chronic HIV-infected cells for 48 h with 0.34 microM M-IBDET or 2.9 microM A-IBDAT caused about 50% inhibition in as virus yield ED50 as assayed by the PFU method. Almost 2 logs of virus infectivity (PFU) was suppressed after 48 h of treatment with 17.4 microM A-IBDAT. Therapeutic index values of 20 and 30 were found for M-IBDET and A-IBDAT, respectively. A significant selective inhibition of HIV structural protein synthesis was shown by both M-IBDET and A-IBDAT.

Antiviral Agents↗

Charge transfer and oxy radicals in antimalarial action. Quinones, dapsone metabolites, metal complexes, iminium ions, and peroxides.

A mechanism of action is proposed that encompasses almost all of the main categories of antimalarial agents: quinones and precursors, dapsone metabolites, metal complexes of thiosemicarbazones and biguanides, iminium-type ions from acridines and quinolines, and peroxides. The toxic effect of the drugs is believed to result from the generation of reactive oxygen radicals that usually arise via charge transfer. Electrochemical studies (reduction potential and reversibility) were performed on a number of these agents. Reduction potentials range from -0.23 to -1.52 V. It is likely that the in vivo values are appreciably more positive in certain cases.

Aminacrine↗

Design, synthesis and 64Cu labeling of fatty acid analogs containing dithiosemicarbazone chelate.

For the development of 62Cu labeled fatty acid analogs, two fatty acid analogs, containing dithiosemicarbazone (DTS) molecule as the 62Cu coordinating site, were designed and synthesized: a fatty acid analog containing DTS molecule at the omega-position, (a) the 12,13-dioxotetradecanoic acid di(N-methyl-thiosemicarbazone) (FA-DTS), and an omega-phenyl fatty acid analog containing DTS molecule at the para-position, (b) the p-carboxyundecylphenylglyoxal-di (N-methylthiosemicarbazone] (PFA-DTS). FA-DTS was synthesized by the reaction of ethyl diethoxyacetate with ethyl 11-bromonundecanate by successive decarboxylation and hydrolysis and final condensation with N-methylthiosemicarbazide. PFA-DTS was synthesized by the Friedel-Craft acylation of ethyl 11-phenylundecanate, selenium oxidation of the acetophenone derivative, followed by the condensation with N-methylthiosemicarbazide. Radiolabeling of FA-DTS and PFA-DTS with [64Cu]copper acetate was simple, rapid and quantitative. When injected into mice, both compounds were distributed and retained in the myocardium. These results offer a good basis for further development of 62Cu labeled fatty acid analogs.

Animals↗

Evaluation of copper-labeled bifunctional chelate-albumin conjugates for blood pool imaging.

62Cu(T1/2 = 9.8 min) is a generator-produced positron-emitting radionuclide with a half-life amenable to blood-pool imaging with PET. Three bifunctional chelates [cyclic anhydride of diethylenetriaminepentaacetic acid (cDTPAA), 6-bromoacetamidobenzyl-1,4,8,11-tetraazacyclotetradecane-N,N ',N", N"'-tetraacetic acid (BAT), and p-carboxyethylphenylglyoxal-bis-(4N-methyl-thiosemicarbazone (CE-DTS)] were conjugated to HSA and labeled with 67Cu. The labeling efficiency of 67Cu-DTS-HSA was > 90%, whereas the labeling yields of 67Cu-DTPA-HSA and 67Cu-benzyl-TETA-HSA were less than 70%. Blood clearance and biodistribution of these three 67Cu-labeled conjugates were determined in rats. Of the three 67Cu-labeled bifunctional chelate-HSA conjugates, 67Cu-benzyl-TETA-HSA remained in the blood pool the longest, achieving stable blood levels at times longer than 24 h post-injection. The 67Cu radioactivity cleared the blood within 60 min post-injection of 67Cu-DTS-HSA, and within 10 min after administration of 67Cu-DTPA-HSA, indicating the dissociation of Cu2+ from these conjugates. Copper-labeled DTS-HSA achieved stable blood concentrations for at least 30 min post-injection and was therefore evaluated as a vascular imaging agent. DTS-HSA and benzyl-TETA-HSA were labeled with 62Cu and administered to a dog for blood-pool imaging using PET. Images were nearly identical to an image taken after administration of C15O. Because of the high labeling efficiency, DTS-HSA can be labeled with 62Cu without purification, making it more practical than 62Cu-benzyl-TETA-HSA as a blood-pool imaging agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Antiproliferative activities of iron and platinum conjugates of salicylaldehyde semi-/thiosemicarbazones against C6 glioma cells.

The identification of novel therapeutic agents for the management of malignant gliomas represents an area of active research. Here, we show that among the iron and platinum complexes of 2-hydroxybenzaldehyde semi-/thiosemicarbazones the latter inhibits the growth of C6 glioma cells in vitro with an IC50 value of 45 microM. Structural characterization reveals iron complexes to be octahedral having intermediate S = 3/2 spin states while platinum complexes are found to be square planar moieties. Our findings suggest that the platinum compounds of 2-hydroxybenzaldehyde thiosemicarbazone are potential candidates for the treatment of malignant gliomas.

Aldehydes↗

Synthesis, spectral, catalytic and antimicrobial studies of PPh3/AsPh3 complexes of Ru(II) with dibasic tridentate O, N, S donor ligands.

Complexes of the type [Ru(CO)(EPh(3))(B)(L)] (E = P or As; B = PPh(3), AsPh(3), py or pip; L=dianion of the Schiff bases derived from thiosemicarbazone with acetoacetanilide, acetoacet-o-toluidide and o-chloro acetoacetanilide) have been synthesized from the reactions of equimolar amounts of [RuHCl(CO)(EPh(3))(2)(B)] and Schiff bases in benzene. The new complexes have been characterized by analytical and spectral (IR, electronic, NMR) data. The arrangement of PPh(3) groups around ruthenium metal was determined from (31)P NMR spectra. An octahedral structure has been assigned for all the new complexes. All the complexes exhibited catalytic activity for the oxidation of benzyl alcohol and cyclohexanol in presence of N-methylmorpholine-N-oxide as co-oxidant. The complexes also exhibited antibacterial activity against E. coli, Aeromonas hydrophilla and Salmonella typhi. The activity was compared with standard streptomycin.

Aeromonas↗

In the procurement of a neutral and compact monomeric complex of dithiosemicarbazone (DTS) derivative: 99mTc-KTS.

As a basic structure of a bifunctional radiopharmaceutical (BR), dithiosemicarbazone (DTS) enables the formation of a small conjugated chelating ring with divalent metals (Cu2+, Zn2+, Ni2+), yielding stable and compact complexes. In the development of a neutral and compact monomeric DTS complex of technetium (99mTc), a DTS containing ligand, kethoxal-bis(thiosemicarbazone) (KTS) was selected. A well known monomeric Cu-KTS complex (or 64Cu-KTS) is taken as a model compound, and in vitro (TLC, EP, HPLC) and in vivo (mice biodistribution) studies were compared. Using the stannous chloride method, under conditions to avoid the hydrolytic polynucleation of technetium, a good yield of 99mTc-KTS with characteristics resembling the non-charged, compact and stable Cu-KTS is obtained, in in vitro as well as in vivo studies. The importance of DTS as the constituent of a BR is discussed.

Animals↗

The standardization of 62Cu and experimental determinations of dose calibrator settings for generator-produced 62CuPTSM.

The Positron Emission Tomography agent 62Cu Pyruvaldehyde Bis(N4-methyl)thiosemicarbazone (PTSM) has been standardized by the National Institute of Standards and Technology (NIST) using 4 pi beta liquid scintillation counting with 3H-standard efficiency tracing. Using a measurement model developed at NIST for the determination of experimental dose calibrator dial settings for short-lived radionuclides, the correct dial settings for 62CuPTSM in a clinically useful geometry (a 35 ml plastic syringe containing 33 ml of solution) as well as the standard NIST 5 ml glass ampoule have been elucidated. This measurement model is fully described, as is the treatment of associated uncertainties. The correct instrument settings for the NIST Capintec CRC-12 re-entrant ionization chamber ('dose calibrator') were found to be '499 +/- 6' and '489 +/- 8', respectively, for the syringe and ampoule geometries. The stated uncertainties are expanded (k = 2) uncertainties. The expanded uncertainties in the measured activity arising from these new dial settings are +/- 0.8% and +/- 1.4%, respectively, for the syringe and ampoule. The measured activities using these settings are lower than those obtained from the manufacture's recommended setting of '448' by 9.7% for the syringe and 7.7% for the ampoule, and underscore the need for experimental verification of the dose calibrator settings for each radionuclide and each geometry used in the clinic.

Calibration↗

Trityl isothiocyanate support for solid-phase synthesis.

Trityl isothiocyanate resin [1], prepared from commercially available trityl chloride resin, is a useful precursor of the trityl thiosemicarbazide resin [2]. This resin can be employed in the solid-phase synthesis of a variety of supported isatin beta-thiosemicarbazones [4] and their Mannich derivatives [6]. A variety of thioureas [7] can be easily prepared by the reaction of [1] with amines. The supported thioureas are directly and efficiently converted to 2-aminothiazole-5-carboxylates [8] by reaction with methyl 2-chloroacetoacetate.

Combinatorial Chemistry Techniques↗

Heterometallic compounds assembled from ferrocene-containing bisthiosemicarbazone clips.

Heteropolynuclear organometallic compounds have been constructed by using the ferrocene-based ligand H(2)L, [NH(2)SCNHN=C(CH(3))(C(5)H(4))](2)Fe. Reaction of the ligand H(2)L with the cobalt(II) salt gave a tetranuclear helicate Co(2)Fe(2) (1) with two ferrocene-based clips wrapped around the two cobalt atoms. The chiral helicates recognized the neighbors with same chirality through intermolecular hydrogen bonding between the thiosemicarbazone moieties to form a one-dimensional chiral channel. Reaction of the ligand H(2)L with the cadmium(II) salt afforded a tetranuclear dimeric compound Cd(2)Fe(2) (2), with two symmetric related parts bridged through two sulfur atoms. Reaction of the ligand H(2)L with the copper(I) salt, in the presence of triethylamine, resulted in a hexanuclear compound Cu(4)Fe(2) (3) with a crownlike Cu(4)S(4) octagon similar to that of S(8) sited inside and two ferrocene-containing ligands positioned outside. Electrochemical measurements were displayed to investigate the redox communications between the ferrocene moieties through metal centers.

Cadmium↗

Unprecedented [V2O]6+ core of a centrosymmetric thiosemicarbazonato dimer: spontaneous deoxygenation of oxovanadium(IV).

The complex cation [{V(daptsc)(MeOH)}2(mu-O)]2+ [daptsc(2-) = 2,6-diacetylpyridine bis(thiosemicarbazonate)] is the first crystallographically elucidated dimer to possess a [V2O]6+ core, the [V(IV)-O-V(IV)]6+ structural unit, formed by cleavage of the multiple bond in the oxo-cation VO2+, is linear with the oxo group residing on a crystallographic center of inversion, and the temperature dependence of the magnetic data of the dimer is consistent with weak antiferromagnetic coupling of the d1-d1 centers.

Crystallography, X-Ray↗

A class of iron chelators with a wide spectrum of potent antitumor activity that overcomes resistance to chemotherapeutics.

Novel chemotherapeutics with marked and selective antitumor activity are essential to develop, particularly those that can overcome resistance to established therapies. Iron (Fe) is critical for cell-cycle progression and DNA synthesis and potentially represents a novel molecular target for the design of new anticancer agents. The aim of this study was to evaluate the antitumor activity and Fe chelation efficacy of a new class of Fe chelators using human tumors. In this investigation, the ligands showed broad antitumor activity and could overcome resistance to established antitumor agents. The in vivo efficacy of the most effective chelator identified, di-2-pyridylketone-4,4,-dimethyl-3-thiosemicarbazone (Dp44mT), was assessed by using a panel of human xenografts in nude mice. After 7 weeks, net growth of a melanoma xenograft in Dp44mT-treated mice was only 8% of that in mice treated with vehicle. In addition, no differences in these latter animals were found in hematological indices between Dp44mT-treated mice and controls. No marked systemic Fe depletion was observed comparing Dp44mT- and vehicle-treated mice, probably because of the very low doses required to induce anticancer activity. Dp44mT caused up-regulation of the Fe-responsive tumor growth and metastasis suppressor Ndrg1 in the tumor but not in the liver, indicating a potential mechanism of selective anticancer activity. These results indicate that the novel Fe chelators have potent and broad antitumor activity and can overcome resistance to established chemotherapeutics because of their unique mechanism of action.

Animals↗

Potentiation of antiherpetic activity of acyclovir by ribonucleotide reductase inhibition.

Compound A723U, a 2-acetylpyridine thiosemicarbazone, produced apparent inactivation of herpes simplex virus type 1 (HSV-1) ribonucleotide reductase. Inactivation occurred after A723U formed a reversible complex with the enzyme and only while the enzyme was catalyzing the formation of deoxynucleotides. A723U inhibited HSV-1 replication at concentrations that were not toxic to the confluent host cells. Most importantly, A723U and acyclovir (ACV) were found to exhibit mutual potentiation of their antiviral activities. Subinhibitory concentrations of either compound greatly reduced the ED50 (median effective dose) of the other. Studies of the deoxynucleotide pool sizes and the levels of ACV triphosphate (ACV-P3) revealed that A723U not only significantly reduced the pool of dGTP but also increased the level of ACV-P3 in infected cells. The net result was an 80-fold increase in the ratio of ACV-P3 to dGTP. This should greatly facilitate the initial binding of ACV-P3 to HSV-1 DNA polymerase and probably accounts for the mechanism of potentiation.

Acyclovir↗