Search

The viral resistance of marketed antiviral drugs including the emergence of new viral resistance of the only marketed CCR5 entry inhibitor, maraviroc, makes it necessary to develop new CCR5 allosteric inhibitors. A mutagenesis/modeling approach was used (a) to remove the potential hERG liability in an otherwise very promising series of compounds and (b) to design a new class of compounds with an unique mutant fingerprint profile depending on residues in the N-terminus and the extracellular loop 2. On the basis of residues, which were identified by mutagenesis as key interaction sites, binding modes of compounds were derived and utilized for compound design in a prospective manner. The compounds were then synthesized, and in vitro evaluation not only showed that they had good antiviral potency but also fulfilled the requirement of low hERG inhibition, a criterion necessary because a potential approved drug would be administered chronically. This work utilized an interdisciplinary approach including medicinal chemistry, molecular biology, and computational chemistry merging the structural requirements for potency with the requirements of an acceptable in vitro profile for allosteric CCR5 inhibitors. The obtained mutant fingerprint profiles of CCR5 inhibitors were used to translate the CCR5 allosteric binding site into a general pharmacophore, which can be used for discovering new inhibitors.

Gold(III) compounds have been examined for potential anti-cancer activity. It is proposed that the molecular targets of these compounds are thiol-containing biological molecules such as the cathepsin cysteine proteases. These enzymes have been implicated in many diseases including cancer. The catalytic mechanism of the cathepsin cysteine proteases is dependent upon a cysteine at the active site which is accessible to the interaction of thiophilic metals such as gold. The synthesis and biological activity of square-planar six-membered cycloaurated Au(III) compounds with a pyridinyl-phenyl linked backbone and two monodentate or one bidentate leaving group is described. Gold(III) cycloaurated compounds were able to inhibit both cathepsins B and K. Structure/activity was investigated by modifications to the pyridinyl-phenyl backbone, and leaving groups. Optimal activity was seen with substitution at the 6 position of the pyridine ring. The reversibility of inhibition was tested by reactivation in the presence of cysteine with a bidentate thiosalicylate compound being an irreversible inhibitor. Five compounds were evaluated for in vitro cytotoxicity against a panel of human tumor cell lines. The thiosalicylate compound was tested in vivo against the HT29 human colon tumor xenograft model. A modest decrease in tumor growth was observed compared with the untreated control tumor.

Based on the attrition rate of CCR5 small molecule antagonists in the clinic the discovery and development of next generation antagonists with an improved pharmacology and safety profile is necessary. Herein, we describe a combined molecular modeling, CCR5-mediated cell fusion, and receptor site-directed mutagenesis approach to study the molecular interactions of six structurally diverse compounds (aplaviroc, maraviroc, vicriviroc, TAK-779, SCH-C and a benzyloxycarbonyl-aminopiperidin-1-yl-butane derivative) with CCR5, a coreceptor for CCR5-tropic HIV-1 strains. This is the first study using an antifusogenic assay, a model of the interaction of the gp120 envelope protein with CCR5. This assay avoids the use of radioactivity and HIV infection assays, and can be used in a high throughput mode. The assay was validated by comparison with other established CCR5 assays. Given the hydrophobic nature of the binding pocket several binding models are suggested which could prove useful in the rational drug design of new lead compounds.

The cysteine proteases of the trypanosomatid parasitic protozoa have been validated as targets for chemotherapy of Chagas' disease and leishmaniasis. Metal complexes of gold, platinum, iridium, palladium, rhodium and osmium have been reported to have activity against a variety of trypanosomatids, but the molecular target of these compounds has not been defined. The activity of gold(III) and palladium(II) cyclometallated complexes, and oxorhenium(V) complexes against mammalian and parasitic cysteine proteases was investigated. All gold(III) complexes (1-6) inhibited cathepsin B with IC(50) values in the range of 0.2-1.4 microM. Of the six palladium compounds, aceto[2,6-bis[(butylthio-kappa S)methyl]phenyl-kappa C]-, (SP-4-3)-palladium(II) (11) was the most potent inhibitor of cathepsin B with an IC(50) of 0.4 microM. A clear structure-activity relationship was observed with the oxorhenium(V) complexes with chloro[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium(V) (16) being the most potent inhibitor of cathepsin B with an IC(50) of 0.009 microM. Six complexes were further tested against the parasite cysteine proteases, cruzain from T. cruzi, and cpB from L. major; the most potent inhibitors were the two rhenium complexes (2(1H)-pyridinethionato-kappa S(2))[2,6-bis[(mercapto-kappa S)methyl]pyridine-kappa N(1)] oxorhenium(V) (15) and chloro[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium(V) (16). The compounds were also evaluated in assays for parasite growth. Two oxorhenium(V) compounds ((p-methoxyphenylthiolato-S)[2,6-bis[(mercapto-kappa S)methyl]pyridine-kappa N(1)] oxorhenium(V) (14) and (methanethiolato)[2,2'-(thio-kappa S)bis[ethanethiolato-kappa S)]] oxorhenium (V) (18)) and the palladium compound 11 inhibited T. cruzi intracellular growth, and compound 11 inhibited promastigote growth in three Leishmania species. In conclusion this preliminary data indicates that metal complexes targeted at parasite cysteine proteases show promise for the treatment of both Chagas' disease and leishmaniasis.

The synthesis of four new oxorhenium(V) complexes containing the “3 + 1” mixed-ligand donor set, ReO(SYS)X (where Y = S, py; X = Cl, Br), is described. All of the complexes tested exhibited selectivity for cathepsin B over K. Most notably, compound 6, ReO(SSS-2,2‘)Br (IC50(cathepsin B) = 1.0 nM), was 260 times more potent against cathepsin B. It was also discovered that complexes containing the same tridentate (SSS) ligand were more potent when the leaving group was bromide versus chloride (e.g., IC50(cathepsin B): ReO(SSS-2,2‘)Cl (4), 8.8 nM; ReO(SSS-2,2‘)Br (6), 1.0 nM). Mechanistic studies with cathepsin B showed that both compounds 2 (ReO(SpyS)(SPhOMe-p)) and 4 were active-site-directed. Compound 2 was determined to be a tight-binding, reversible inhibitor, while compound 4 was a time-dependent, slowly reversible inhibitor. The results described in this paper show that the oxorhenium(V) “3 + 1” complexes are potent, selective inhibitors of cathepsin B and have potential for the treatment of cancer.

The synthesis of several new oxorhenium(V) complexes containing the ‘3 + 1’ mixed-ligand donor set, ReO(SXS)(SR) (where X = S, O, N(R′); R = alkyl, aryl, heterocylce; R′ = H, alkyl, aryl), is described. The X-ray structure for four of these complexes ReO(SN(Ph)S)(SPh) ( 6 ), ReO(SN(CH 2 CH 2 NMe 2 )S)(SPhOMe- p ) ( 10 ), ReO(SOS)(SPh) ( 29 ) and ReO(SOS)(SPhNO 2 - p ) ( 30 ) was determined. The inhibitory activity of all of the oxorhenium(V) complexes reported herein was evaluated against the cysteine proteases cathepsin B and K in vitro. Compound 25 , ReO(SSS)(S-4py) · HCl, was the best inhibitor of the series against cathepsin B with an IC 50 of 10 nM. Several of the complexes exhibited specificity for cathepsin B over K, suggesting that oxorhenium(V) complexes can be designed to be enzyme specific. The results described in this paper show that the oxorhenium(V) ‘3 + 1’ complexes are potent inhibitors of cathepsin B and K, constituting promising potential for the treatment of cancer and osteoporosis, respectively.

In this study a series of Ru I I I complexes, chelated by analogues of ethylenediaminetetraacetic acid (edta) and diethylenetriaminepentaacetic acid (dtpa), were produced and tested for NO scavenging ability. Modifications to the edta and dtpa ligand frameworks were made in an effort to alter the reactivity, aqueous stability and pharmacokinetics of the resulting Ru I I I complexes. The X-ray structure of the nitrosyl complex 38 confirms that the Ru I I I complex 27 reacts with NO to form a linear {Ru-NO} [ 6 ] complex. The nitrosyl complex [C 1 5 H 1 5 N 4 O 1 1 Ru] crystallized in the P2 1 /c space group with a = 12.731(3) A, b = 10.894(2) A, c = 14.241 (3) A, β = 107.320(4)°, V = 1885.6(7)A 3 , and Z = 4. Kinetic studies on the reactions of 14 (k = 2.38×10 6 M - 1 s - 1 ) and 27 (k = 2.30x 10 5 M - 1 s - 1 ) with NO exemplify the difference in chemical properties obtained by ligand framework manipulation. Binding constants of 14 (K B = 5×10 6 M - 1 ) and 27 (K B = 2 × 10 5 M - 1 ) with NO were also measured, indicating the tight binding of NO by the Ru I I I complexes. The activity of the Ru I I I complexes to scavenge nitric oxide was evaluated using RAW264 murine macrophage cells. Ligand analogues of edta that have a pyridine donor as part of the N,N chelate such as 20 and 24 exhibit similar scavenging activity to the parent compound. Ligand analogues of dtpa that have R groups at the central amine in place of the carboxylic acid such as 31, 34, and 37 are also efficient NO scavengers.

Whilst nitric oxide (NO) has emerged as one of the most versatile and ubiquitous molecules in the human body with a diverse range of physiological functions, dysfunction in NO biosynthesis or metabolism has led to the pathogenesis of a number of disease states. A variety of therapeutic strategies have therefore emerged that either reduce or increase endogenous NO levels depending on the disease pathology. The predominant strategy to date to reduce levels of NO is to utilise specific isoform selective inhibitors of nitric oxide synthases, the enzymes responsible for NO biosynthesis. An alternative line of attack, not r elate d to specificity for a particular enzyme, but rather on compartmental localisation and pharmacokinetics, is to re move or sc ave nge the exce ss NO re sponsible for the dise ase pathology. In this regard, a number of NO scavenger molecules have demonstrated pharmacological activity across a broad spectrum of disease states. This review will highlight the rationale behind the development, and the current state of play, of one such class of NO scavengers, complexes of the d-block transition metal ruthenium. Prior to this, a brief overview of the remarkable diversity of NO, both from a chemical and biological viewpoint, will be provided for perspective.

Objectives: We tested whether nitric oxide scavenging with a ruthenium-based compound (AMD6221) would improve hemodynamics and alter nitric oxide synthase and matrix metalloproteinase activities in a canine model of cardiopulmonary bypass. Methods: Dogs were randomized to either cardiopulmonary bypass (n = 12) or control (n = 12) groups. They were further randomized to receive a continuous infusion of AMD6221 or placebo. Cardiopulmonary bypass was maintained for 90 minutes, and then, 4 hours later, dogs were killed. Cardiac, lung, and brain sections were snap frozen in liquid nitrogen for determination of nitric oxide synthase, matrix metalloproteinase 2, and matrix metalloproteinase 9 activities. Results: After cardiopulmonary bypass, 3 of 6 placebo-treated (cardiopulmonary bypass-placebo) and 0 of 6 AMD6221-treated (cardiopulmonary bypass-6221) animals required phenylephrine infusion to maintain a predetermined blood pressure (P

The preparation of two RuIII polyaminocarboxylate complexes, AMD6245 and AMD6221, and their nitrosyl analogues, AMD6204, AMD6263, and AMD3689, is described. The compounds are characterized by IR, ES-MS, and 13C and 15N NMR spectroscopy where appropriate and cyclic voltammetry. The crystal structures for AMD6245, AMD6263, and AMD3689 are presented. AMD6245 (C10H14N2O9Ru) crystallized in the P21/c space group with a = 8.4382(2) A, b = 8.8304(2) A, c = 17.6321(4) A, β = 99.603°, V = 1295.3(2) A3, and Z = 4. AMD6263 (C10H14N3O10Ru) crystallized in the P21/c space group with a = 9.9043(4) A, b = 13.1144(3) A, c = 12.0914(4) A, β = 100.191°, V = 1545.8(5) A3, and Z = 4. AMD3689 (C14H24.56N4O13.28Ru) crystallized in the P1 space group with a = 8.838(2) A, b = 9.452(3) A, c = 13.419(4) A, α = 78.413(6)°, β = 75.804(6)°, γ = 73.562(6)°, V = 1031.8(5) A3, and Z = 2. The reaction of AMD6245 and AMD6221 with nitric oxide is investigated using EPR spectroscopy and stopped flow kinetics. Upon reaction with NO, a linea...

The First International Conference on the Biology, Chemistry and Therapeutic Applications of Nitric Oxide represented a milestone in the history of nitric oxide (NO) research. This meeting combined the two major conferences on NO, the Biology of Nitric Oxide and the Biochemistry and Molecular Biology of Nitric Oxide. The conference was held at the Hyatt Regency Hotel in San Francisco under the auspices of the Nitric Oxide Society. This meeting successfully brought together scientists from all disciplines currently working in the field. There were three sessions on each day of the meeting, one session for each of the three areas (biology, chemistry and therapy). Each session consisted of two plenary lectures of 20 min duration followed by a series of short 10 min papers, with a total of 70 oral presentations. The meeting also included approximately 400 excellent poster presentations and a hot topics session. All the presentations and posters were of a very high standard and the conference chairs, J Parkins...

The essential role of nitric oxide (NO) in normal physiology and its involvement in the pathophysiology of a variety of diseases render the compound an attractive therapeutic target. NO donor drugs are used in the treatment of hypotension and angina where abnormalities in the L-arginine-nitric oxide pathway have been implicated. Overproduction of NO has been associated with a number of disease states including septic shock, inflammatory diseases, diabetes, ischaemia-reperfusion injury, adult respiratory distress syndrome, neurodegenerative diseases and allograft rejection. NO is produced by a group of enzymes, the nitric oxide synthases. Selective inhibition of the inducible isoform is one approach to the treatment of diseases where there is an overproduction of NO; an alternative approach is to scavenge or remove excess NO. A number of NO scavenger molecules have demonstrated pharmacological activity in disease models, particularly models of septic shock. These include organic molecules such as PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), haemoglobin derivatives such as the pyridoxalated haemoglobin polyoxyethylene conjugate (PHP), low molecular weight iron compounds of diethylenetriaminepentaacetic acid and diethyldithiocarbamate and ruthenium polyaminocarboxylate complexes. The data suggest a potential role for NO scavengers in the treatment of NO mediated disease.

The use of a screening strategy based on human tumor cell lines, which are also tumorigenic in immune-deprived mice, is described. Activity against the human tumor cells in vitro and in vivo, is complemented with studies on the mechanism of action. This aporoach is demonstrated using 2-[(dimethylamino)-methyl]phenyl (damp) gold(III) compounds of the type [Au X2(damp)], where X = chloride, thiocyanate, acetate, or the bidentate ligands oxalate and malonate. All compounds were shown to be selectively active against a human bladder tumor cell line (HT1376) in vitro, and active in an in vitro panel of ovarian tumor cell lines. The acetato complex was shown to be active in experimental animal models of both the HT1376 bladder tumor, and the CH1 ovarian tumor. Although the [AuX2(damp)] compounds share structural features in common with cisplatin, and exhibit interesting in vivo activity against human tumor cells, the data indicate that they have a very different biochemical mechanism from platinum-based drugs and represent a potentially new class of metal-based antitumor agents.

1 Ruthenium(III) reacts with nitric oxide (NO) to form stable ruthenium(II) mononitrosyls. Several Ru(III) complexes were synthesized and a study made of their ability to bind NO, in vitro and also in several biological systems following expression of the inducible isoform of nitric oxide synthase (iNOS). Here we report on the properties of two, related polyaminocarboxylate-ruthenium complexes: potassium chloro[hydrogen(ethylenedinitrilo)tetraacetato]ruthenate (=JM1226; CAS no.14741-19-6) and aqua[hydrogen(ethylenedinitrilo)tetraacetato]ruthenium (=JM6245; CAS no.15282-93-6). 2 Binding of authentic NO by aqueous solutions of JM1226 yielded a product with an infrared (IR) spectrum characteristic of an Ru(II)-NO adduct. A compound with a similar IR spectrum was obtained after reacting JM1226 with S-nitroso-N-acetylpenicillamine (SNAP). 3 The effect of JM1226 or JM6245 on nitrite (NO2−) accumulation in cultures of macrophages (RAW 264 line) 18 h after stimulating cells with lipolysaccharide (LPS) and interferon-γ (IFNγ) was studied. Activation of RAW264 cells increased NO2− levels in the growth medium from (mean±1 s.e.mean) 4.9±0.5 μM to 20.9±0.4 μM. This was blocked by actinomycin D (10 μM) or cycloheximide (5 μM). The addition of JM1226 or JM6245 (both 100 μM) to activated RAW264 cells reduced NO2− levels to 7.6±0.2 μM and 8.8±0.6 μM, respectively. NG-methyl-L-arginine (L-NMMA; 250 μM) similarly reduced NO2− levels, to 6.1±0.2 μM. 4 The effect of JM1226 or JM6245 on NO-mediated tumour cell killing by LPS+IFNγ-activated macrophages (RAW 264) was studied in a co-culture system, using a non-adherent murine mastocytoma (P815) line as the ‘target’ cell. Addition of JM1226 or JM6245 (both 100 μM) to the culture medium afforded some protection from macrophage-mediated cell killing: target cell viability increased from 54.5±3.3% to 93.2±7.1% and 80.0±4.6%, respectively (n=6). 5 Vasodilator responses of isolated, perfused, pre-contracted rat tail arteries elicited by bolus injections (10 μl) of SNAP were attenuated by the addition of JM1226 or JM6245 (10−4 M) to the perfusate: the ED50 increased from 6.0 μM (Krebs only) to 1.8 mM (Krebs+JM6245) and from 7 μM (Krebs only) to 132 μM (Krebs+JM1226). Oxyhaemoglobin (5 μM) increased the ED50 value for SNAP from 8 μM to 200 μM. 6 Male Wistar rats were injected with bacterial LPS (4 mg kg−1; i.p.) to induce endotoxaemia. JM1226 and JM6245 (both 100 μM) fully reversed the hyporesponsiveness to phenylephrine of tail arteries isolated from animals previously (24 h earlier) injected with LPS. Blood pressure recordings were made in conscious LPS-treated rats using a tail cuff apparatus. A single injection of JM1226 (100 mg kg−1, i.p.) administered 20 h after LPS (4 mg kg−1, i.p.) reversed the hypotension associated with endotoxaemia. 7 The results show that JM1226 and JM6245 are able to scavenge NO in biological systems and suggest a role for these compounds in novel therapeutic strategies aimed at alleviating NO-mediated disease states.

Reaction of (PhCNSSN) 2 with [Pt(PPh 3 ) 3 ] or [Pt(PPh 3 ) 4 ] produced two complexes [Pt{SNC(Ph)NS-S,S′}(PPh 3 ) 2 ] 1 and [Pt 3 {µ-SNC(Ph)NS-S,S′} 2 (PPh 3 ) 4 ] 2. In contrast, reaction with [Pd(PPh 3 ) 4 ] yielded only the trimetallic complex [Pd 3 {µ-SNC(Ph)NS-S,S′} 2 (PPh 3 ) 4 ] 3. The three complexes were characterised by X-ray crystallography as the following solvates: 1·MeCN, 2·2C 6 H 5 Me and 3·2CH 2 Cl 2 . In all three structures the S–S bond is formally broken [d ss in 1, 2 and 3 are 3.168(4), 3.046(8) and 3.044(8) A respectively], the metals increase their oxidation states to +2 and possess square-planar co-ordination geometries. The physical properties of the complexes are described and the biological activities of 1 and 2 are reported.

The redesign of the previously reported thiophene-3-yl-methyl urea series, as a result of potential cardiotoxicity, was successfully accomplished, resulting in the identification of a novel potent series of CCR5 antagonists containing the imidazolidinylpiperidinyl scaffold. The main redesign criteria were to reduce the number of rotatable bonds and to maintain an acceptable lipophilicity to mitigate hERG inhibition. The structure–activity relationship (SAR) that was developed was used to identify compounds with the best pharmacological profile to inhibit HIV-1. As a result, five advanced compounds, 6d, 6e, 6i, 6h, and 6k, were further evaluated for receptor selectivity, antiviral activity against CCR5 using (R5) HIV-1 clinical isolates, and in vitro and in vivo safety. On the basis of these results, 6d and 6h were selected for further development.

The only current clinical application for gold drugs is in the treatment of rheumatic diseases, primarily rheumatoid arthritis. Little has changed in this area since the introduction of the orally available gold drug auranofin in 1985. There has been considerable research effort to find alternative therapeutic applications for gold drugs, particularly for the treatment of cancer, but after promising early indications the lead candidate [Au(dppe)2]Cl failed to enter clinical trials due to cardiotoxicity. Despite this setback research in this field has not abated. Recent work in our own laboratory has indicated that stable gold(III) compounds have activity in disease models of human cancer and this may be the way forward in this area. Gold compounds also have potential as antimicrobial agents, particularly against topical infections. The most interesting advances in the pharmacology of gold drugs have come from studies on their mechanism of action. The diverse effects of gold drugs on the immune system have been known for some time but there has been no satisfactory biochemical explanation for these observations. Recent work on the effect of gold compounds on gene transcription provides a new clue to this mechanism. After 60 years of chrysotherapy perhaps an improved understanding of the molecular and biochemical mechanism of gold compounds will provide the impetus for new advances in the medical use of gold drugs.

Several new organogold(III) derivatives of the type [AuX(2)(damp)] (damp = o-C(6)H(4)CH(2)NMe(2)) have been prepared [X = CN, SCN, dtc, or X(2) = tm; dtc = R(2)NCS(2) (R = Me (dmtc) or Et (detc)); tm = SCH(CO(2))CH(2)CO(2)Na] together with [AuCl(tpca)(damp)]Cl (tpca = o-Ph(2)PC(6)H(4)CO(2)H), [Au(dtc)(damp)]Y (Y = Cl, BPh(4)) and K[Au(CN)(3)(damp)]. The (13)C NMR spectra of these and previous derivatives have been fully assigned. In [Au(dtc)(2)(damp)] and K[Au(CN)(3)(damp)], the damp ligand is coordinated only through carbon, as shown by X-ray crystallography and/or NMR. [Au(detc)(2)(damp)] has space group C2/c, with a = 29.884(4) Å, b = 13.446(2) Å, c = 12.401(2) Å, beta = 99.45(3)(o), V = 4915 Å(3), Z = 8, and R = 0.057 for 1918 reflections. The damp and one detc ligand are monodentate, the other detc is bidentate; in solution, the complex shows dynamic behavior, with the detc ligands appearing equivalent. The crystal structure of [Au(dmtc)(damp)]BPh(4) [Pna2(1), a = 26.149(5) Å, b = 11.250(2) Å, c = 11.921(2) Å, V = 3507 Å(3), Z = 4, R = 0.073, 1772 reflections] shows both ligands to be bidentate in the cation, but the two Au-S distances are nonequivalent. The crystal structure of [Au(tm)(damp)] has also been determined [P2(1)/n, a = 18.267(7) Å, b = 9.618(3) Å, c = 18.938(4) Å, beta = 113.45(3)(o), V = 3053 Å(3), Z = 8, R = 0.079, 1389 reflections]. The tm is bound through sulfur and the carboxyl group which allows five-membered ring formation. In all three structures, the trans-influence of the sigma-bonded aryl group is apparent. [AuCl(2)(damp)] has been tested in vitroagainst a range of microbial strains and several human tumor lines, where it displays differential cytotoxicity similar to that of cisplatin. Against the ZR-75-1 human tumor xenograft, both [AuCl(2)(damp)] and cisplatin showed limited activity.

Four analogues of the gold(III) complex [AuCl2(damp)] (1) (damp = 2-[(dimethylamino)methyl]phenyl) have been evaluated for antitumor activity. The compounds have structural features in common with cisplatin which was included as a comparison in the study. In vitro, against a panel of cell lines established from tumors of different tissue types, the gold complexes showed broadly similar growth inhibitory properties with some selectivity to the HT1376 bladder cell line. In a panel of human ovarian carcinoma cell lines, non-cross-resistance to cisplatin was observed, for the complexes, in an acquired cisplatin-resistant line. In vivo, using subcutaneously implanted xenografts derived from the HT1376 bladder and CH1 ovarian cell lines, [Au(acetato)2(damp)] (3) and [Au(malonato)(damp)] (5) (administered intraperitoneally) gave significant tumor inhibition. Mechanistic studies performed with compound 3 showed marked differences to cisplatin. Thus, much higher concentrations of the gold compound were required to affect Col E1 plasmid mobility, and an alkaline elution study showed that 3 did not cause interstrand DNA cross-links in SK-OV-3 cells. Exposure of SK-OV-3 cells to 3 induced only relatively minor changes in cell cycle distribution. Furthermore 3 was only marginally active in vivo against the cisplatin-sensitive murine ADJ/PC6 plasmacytoma. In summary, the gold-(III) complexes 3 and 5 exhibited selective cytotoxicity in vitro and showed in vivo antitumor activity against human carcinoma xenografts. Also, although 3 has some structural similarity to cisplatin, its mode of action appears to be different.

The gold salt [(tht)AuCl] was reacted with [1-N,N-dimethylaminométhyl-2-diphenylphosphino]ferrocene (1) forming the bimetallic derivative 4. The reaction of methyl iodide and tetramethylammonium bromide on the chloride 4 produced the ammonium salt 5 and the bromide 6 respectively. New aminophosphines 2 and 3, which represent two of the rare phosphorylated metallocenes containing P(III)-N bond have also been coordinated to gold(I) to form 7 and 8. The presence of the ethoxy group in 7 provides evidence for the lability of one nitrogen-phosphorus bond. The X-ray structure of compounds 4 and 7 have been established. Both crystallize in space group P21/c, monoclinic, with a = 11.095(2) Å, b = 12.030(3) Å, c = 17.763(4) Å, β= 94.02(2)∘, Z = 4 for 4 and a = 14.863(3) Å, b = 8.036(5)Å, c = 18.062(5)Å, β =101.64(1)°, Z = 4 for 7. A197u Mössbauer data are in good agreement with those for other linear P-Au-Cl containing complexes. The compounds were evaluated for in vitro anti-tumour activity against two human tumours. Differential cytotoxicity was observed with activity comparable to cisplatin, with the exception of one compound which was significantly more cytotoxic.

The discovery of the platinum anticancer drug cisplatin provided a major stimulus for research into metal-based drugs. The molecular target for the platinum agents is DNA; however recent developments in inorganic medicinal chemistry have identified several alternative novel targets for metal-based drugs. Biological molecules with essential thiol groups are attractive targets. Thiol-containing molecular targets include the redox enzymes thioredoxin reductase and glutathione reductase, transcription factors, and cysteine proteases such as caspases and cathepsins. Inorganic chemistry offers many opportunities for medicinal chemistry, and alternative targets for metal-based drugs are reviewed, with a focus on cysteine proteases. The cathepsin cysteine proteases have numerous physiological functions, and have been implicated in diseases including cancer, autoimmune and inflammatory, and parasitic diseases. The catalytic mechanism of these enzymes is dependent upon a cysteine at the active site. We postulate that metal complexes can inhibit these enzymes via a ligand substitution with the thiol of the active site cysteine. We have investigated several classes of metal complexes including cyclometalated organo gold(III) and Pd(II) complexes, and a series of rhenium(V) mixed ligand oxorhenium complexes as inhibitors of cathepsin cysteine proteases. Mechanistic studies were conducted on the latter supporting the hypothesis of active site-directed inhibition. These data are reviewed below and discussed in the context of possible therapeutic applications including cancer and parasitic disease.

Chemokines are a family of chemoattractant cytokines involved in leukocyte trafficking, activation, development, and hematopoeisis. Chemokines and their receptors have been implicated in several disease processes, particularly inflammatory and autoimmune disorders and cancer, and are therefore attractive targets for drug development. Chemokine receptors are members of the seven-transmembrane, G protein-coupled receptor (GPCR) family. As such they can be studied using GPCR assays such as ligand binding, G protein activation, and downstream signaling processes such as intracellular calcium flux. In this respect assessing GPCR activation by GTP binding is an important tool to study the early stage of signal transduction. Previously this has been done using the radiolabeled non-hydrolyzable GTP analogue [(35)S]GTPgammaS. In order to avoid the problems involved in working with radioactivity, a new non-radioactive version of the assay has been developed using a europium-labeled GTP analogue in which europium-GTP binding can be assayed using time-resolved fluorescence. We have adapted this assay for chemokine receptors. In this chapter, using the chemokine receptor CXCR4 as an example, we describe the steps for assay optimization. In addition we describe adaptation of this assay for the high-throughput screening of chemokine antagonists.

The new complexes Ti(η5-C5H5)Cl(OC6H4NH2-3)2, Ti(η5-C5H5)Cl(O2CPh)2, Ti(η5-C5H5)2(O2C(S)C6H4-1,2), Ti(η5-C5H5)2Cl(SC6H4OH-4), Ti(η5-C5H5)2(OC6H4NH2-3)2 and Ti(η5-C5H5)2Cl(OC6H4Z) (Z = NO2-2, NO2-3, NO2-4, NH2-3) have been synthesized. The free amine group in Ti(η5-C5H5)2Cl(OC6H4NH2-3) reacts with RCl [R = MeCO, PhCO, (OCCO)1/2, Br(CH2)3CO] in the presence of base to give Ti(η5-C5H5)2Cl(R) but, in the absence of base, PhCOCl reacts to give PhCONHC6H4OH-3 and Ti(η5-C5H5)2Cl2. The X-ray crystal structure of Ti(η5-C5H5)2(OPh)2 has been determined and reveals a pseudo-tetrahedral arrangement of the two η5-cyclopentadienyl and two phenoxide ligands around titanium. The Ti—O(Ph) distances are 1.907(3) A and O—Ti—O is 98.1(2)°. The anti-tumour activities of Ti(η5-C5H5)Cl(OC6H4NH2-3)2, Ti(η5-C5H5)Cl(O2CPh)2 and Ti(η5-C5H5)2(O2C(S)C6H4-1,2) have been assessed in vitro using a panel of seven human tumour cell lines.

The platinum anticancer drug cisplatin has made a major contribution to the treatment of testicular and ovarian cancer. This chance discovery has been the stimulus for research into other metal-based drugs. Inorganic chemistry offers many opportunities for medicinal chemistry, and the discovery of metal-based drugs has moved on from chance discovery to rational drug design. There are however, many challenges associated with the drug discovery and development process. The aim of this review is to provide case histories exemplifying the role of rational drug design in modern inorganic medicinal chemistry in the context of these challenges. The evolution of platinum drugs from cisplatin to third generation drugs is described. The molecular target for the platinum agents is DNA. Alternative molecular targets such as thiol-containing proteins and redox processes are proposed. The example of a simple, safe, efficacious metal-based drug, Fosrenol, is reviewed.

Excess production of nitric oxide by inducible nitric oxide synthase (iNOS) has been implicated in cardiovascular dysfunction associated with the acute phase of diabetes mellitus. We examined if the selective nitric oxide scavenger, AMD6221 (ruthenium[hydrogen(diethylenetrinitrilo)pentaacetato] chloride) improved cardiovascular function in rats with streptozotocin (60 mg/kg, i.v.)-induced diabetes. The cardiovascular effects of noradrenaline (16.5 nmol/kg/min, i.v.) were measured in thiobutabarbitone-anaesthetised diabetic and control rats before and after acute administration of AMD6221 (80 mg/kg). Rats in the acute phase of diabetes (3 weeks post injection of streptozotocin) had impaired mean arterial pressure, left ventricular systolic pressure and maximum rate of increase (+dP/dt) and decrease (-dP/dt) of left ventricular pressure responses to noradrenaline compared with control rats. AMD6221 significantly augmented noradrenaline-induced increases in left ventricular systolic pressure and +/-dP/dt in the diabetic but not control rats. The results show that selective scavenging of nitric oxide by AMD6221 improved cardiac response to noradrenaline in rats with streptozotocin-induced diabetes.

The preparation of a series of [Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)] (tacn = 1,4,7-triazacyclononane; dtc = dimethyldithiocarbamate, diethyldithiocarbamate, pyrrolidinedithiocarbamate, l-prolinedithiocarbamate, l-prolinemethyl ester dithiocarbamate, l-N-methylisoleucinedithiocarbamate) complexes, 5-11, is described. Complex 5 reacts with NO to form the ruthenium nitrosyl complex 12. A series of [Ru(III)(tacn)(pyc)Cl][PF(6)] (pyc = 2-pyridinecarboxylic acid, 2,4- and 2,6-pyridinecarboxylic acid) complexes, 14-16, were prepared along with [Ru(III)(tacn)(mida)][PF(6)] (mida = N-methyliminodiacetic acid), 13, and [Ru(III)(Hnota)Cl], 17, (Hnota = 1-acetic acid-4,7-bismethylcarboxylate-1,4,7-triazacyclononane). Complexes 5-17 were evaluated for use as NO scavengers in an in vitro assay using RAW264 murine macrophage cells. [Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)] complexes 5-11 are very efficient NO scavengers in this assay.

1 Metals in Biology 2 Historical Use of Gold in Medicine 3 Gold Therapy for Rheumatoid Arthritis 4 Mechanism of Action of Antiarthritic Gold Drugs 5 Antitumour 6 Anti-Infective 7 Conclusion 8 Acknowledgement Keywords: gold compounds and medicinal chemistry; metals and maintaining structural integrity; gold exploitation for medical properties throughout history; gold therapy for rheumatoid arthritis; gold therapy and inflammatory response side effects; gold compounds and potential antitumour activity; ligand gold complexes with antitumour activity; microbial infection and antimicrobial properties of gold complexes

Nitric oxide (NO) derived from the up-regulation of inducible NO synthase (iNOS) is believed to play an important role in organ rejection. In experimental models of acute cardiac transplant rejection (i.e., without immunosuppression), treatment using NOS inhibitors to prevent acute rejection have yielded conflicting results. This is most likely due to potential inhibition of constitutive NOS. Accordingly, agents that trap NO directly may have some advantage. In the current study, we evaluated the actions of a ruthenium-based NO scavenger, AMD6221, to inhibit the nitrosylation of myocardial protein and to prolong cardiac allograft survival in a model of acute cardiac transplant rejection (without immunosuppression). In addition, we evaluated the efficacy of AMD6221 used in combination with low-dose cyclosporine (CsA) (i.e., a model of delayed graft rejection). Heterotopic abdominal cardiac transplantation was performed using rat strains with disparities at major and minor histocompatibility loci. Grafts were harvested on postoperative day 6 for histologic examination or analysis of myocardial protein nitrosylation using electron paramagnetic resonance (EPR) spectroscopy. Other animals were monitored twice daily to determine rejection times. Plasma was also taken at postoperative day 6 for determining the concentration of NO by-products (nitrate plus nitrite). Treatment with AMD6221 either prolonged graft survival and/or caused a marked decrease in myocardial nitrosylprotein formation as determined by EPR spectroscopy. In vivo scavenging of NO by AMD6221 was verified by high-performance liquid chromatography analysis of nitrosylated-drug in plasma samples. Low-dose CsA given alone or in combination with AMD6221 completely blocked formation of myocardial nitrosylprotein complexes. Whereas low-dose CsA alone prolonged graft survival, combination therapy with CsA plus AMD6221 produced a synergistic effect on graft survival. These studies indicate that treatment with a ruthenium-based NO scavenger, such as AMD6221, may be an effective regimen used alone or in combination with CsA to protect myocardial proteins from posttranscriptional modification and to prolong cardiac graft survival.

Platinum compounds containing the ligand 1,2-diaminocyclohexane (DACH) such as tetraplatin [PtCl 4 (DACH)] have been found to be active in cisplatin-resistant tumour models. In an attempt to develop novel metal-based drugs with a different therapeutic profile to cisplatin, we have synthesised a series of tin compounds containing the DACH ligand, including the Sn analogue of tetraplatin [SnCl 4 (DACH)], and the di- and monoorganotin complexes [Ph 2 Sn(OAc) 2 (DACH)], [Bu 2 Sn(OAc) 2 (DACH)], [PhSnCl 3 (DACH)], [BuSn(OAc) 3 (DACH)], [BuSnCl 3 (DACH)], and [PhSn(OCOCF 3 ) 3 (DACH)]. Mossbauer and IR spectroscopy indicates that the Sn(DACH) complexes are hexacoordinated with a molecular structure similar to that of tetraplatin. These compounds were tested for potential antitumour activity against a panel of human tumour cell lines, (SW620, SW1116 colon carcinoma, ZR-75-1 breast carcinoma, HT1376 bladder carcinoma, SKOV-3, PA-1 ovarian carcinoma). [Ph 2 Sn(penicillinate)], [Ph 2 Sn(OCOCH 2 NCOCH 2 NH 2 )], [Ph 2 Sn(OAc) 2 ] were included for comparison. The results show that whereas [SnCl 4 (DACH)] and the monoorganotin complexes had limited or no activity, the diorganotin DACH complexes were cytotoxic with an associated increase in potency on going from diphenyl to dibutyltin, with mean IC 50 values of 7.26±4.09 μmol ml −1 for [Ph 2 Sn(OAc) 2 (DACH)] and 2.58±0.83 μmol ml −1 for [Bu 2 Sn(OAc) 2 (DACH)] across the cell line panel. Comparison with [Ph 2 Sn(OAc) 2 ] (IC 50 0.69±0.43 μmol ml −1 ) indicated that addition of the DACH ligand resulted in a decrease in cytotoxicity but increased differential toxicity across the cell line panel. These results indicate that the diorganotin DACH complexes merit further investigation as potential metal-based antitumour drugs.

Introduction, S.P. Fricker. Platinum Anti-Cancer Drugs L.R. Kelland. Gold, F. Shaw III. Ruthenium Compound in Cancer Therapy, G. Sava. Rhodium, Iridium and Palladium Compounds as Experimental Anticancer Drugs, G. Buckley. Organometallic Titanium, Vanadium, Niobium, Molybdenum and Rhenium Complexes - Early Transition Metal Anti-Tumour Drugs, P. Kopf-Maier and H. Kopf. Anti-tumour Activity of Tin Compounds, A.J. Crowe. Gallium Compounds in Cancer Therapy, P. Collery. Bleomycin and Metal Interactions, J.M.C. Gutteridge. The In Vivo use of Metallic Radioisotopes in Cancer Detection and Imaging, D.J. Hnatowich.

Erratum to ‘‘Metal compounds for the treatment of parasitic diseases” [J. Inorg. Biochem. 102 (2008) 1839–1845] Simon P. Fricker *, Renee M. Mosi , Beth R. Cameron , Ian Baird , Youngbao Zhu , Virginia Anastassov , Jennifer Cox , Patricia S. Doyle , Elizabeth Hansell , Gloria Lau , Jonathan Langille , Micki Olsen , Ling Qin , Renato Skerlj , Rebecca S.Y. Wong , Zefferino Santucci , James H. McKerrow c

The biological properties of the lanthanides, based on their similarity to calcium, have stimulated research into their therapeutic application. Historical medical uses of the lanthanides and recent advances and successes will be described in the context of the biological chemistry of lanthanides, including a new metal-based drug, lanthanum carbonate, which has recently been approved as a phosphate binder for the treatment of hyperphosphatemia. This tutorial review will be of interest to those working on metal-based drugs, including inorganic chemists, and biological scientists.

The gold(III) complex [Au(O2CMe)2(dmamp)][dmamp = 2-(dimethylaminomethyl)phenyl] is hydrolysed in wholly or partially aqueous solution. One acetate ligand, presumed to be that trans to the Au–C bond, exchanged with a water molecule rapidly on the NMR time-scale. At high concentrations of water a further hydrolysis step was also discernible, which involved the second acetate group while, in aged solutions, small amounts of a third species, possibly the second isomer of [Au(O2CMe)(dmamp)(H2O)]+, was formed. The reaction of aqueous or dimethyl sulfoxide solutions of the gold(III) complex with various biological ligands was followed by NMR spectroscopy and a range of reactivities was found: caffeine and adenosine showed no reaction, L-cysteine, glutathione and adenine reacted quantitatively and guanosine and inosine showed partial reaction. In in vitro biological tests for antibacterial activity, [Au(O2CMe)2(dmamp)] exhibited a potentially useful selectivity.

Threonine uptake by the parasitic protozoan Trypanosoma brucei has been assessed using an oil-phase separation technique for measuring rapid amino acid fluxes. It was shown that the storage conditions for the organism were critical for the production of reproducible data. Using this method it has been shown that threonine uptake occurs rapidly, being linear for less than 30 s at 37 degrees C in contrast with previous reported results. Kinetic analysis of threonine uptake at 25 degrees C and at physiological plasma threonine levels (20-700 microM) gave a Km of 250 microM and a Vmax of 8 nmol mg-1 cell protein min-1. At these concentrations threonine uptake takes place against a concentration gradient.