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While first- and second-generation EGFR inhibitors (EGFRi) have shown success against EGFR mutant non-small cell lung cancer (NSCLC), the emergence of resistance mechanisms has prevented long-term treatment for many patients. The third-generation inhibitor osimertinib, the current standard of care, is still prone to resistance. Combined with the failure of several late-stage candidates it is clear a novel approach is required. We have developed a transomic analysis platform, PROSPER (Protein Regulation with Objective Seeking Powerful Evidence Retrieval), employing an integrated analysis of genomics, transcriptomics, proteomics, and phosphoproteomics, termed transomics. This proprietary analysis allows us to interpret complex biological relationships and provide a functional map of the biochemical drivers of disease. We investigated the effects of a cross-section of EGFRi in a panel of EGFR mutant lung cancer cell lines and performed a transomics analysis to identify key differences between different EGFRi and drive novel drug discovery to circumvent resistance to EGFR-targeted drugs. Seven drugs, both approved and unapproved EGFRi, were evaluated against three NSCLC cell lines. The cell lines expressed wild-type EGFR (as a control), Ex19del activating mutation (to model EGFR mutant NSCLC), or L858R activating mutation plus T790M gatekeeper mutation (to model a subtype of EGFRi resistant NSCLC). Approved drugs included erlotinib, afatinib (first- and second-generation EGFRi, respectively), and osimertinib (third-generation drug that can overcome the T790M gatekeeper mutation that confers resistance to earlier drugs). The remaining drugs (maverlertinib, naquotinib, olmutinib, rociletinib) are unapproved third-generation inhibitors. The concentration required to inhibit cell growth (IC50) was determined after a 72 h incubation and viability was assessed by CellTiter-Glo. For the transomic analyses, the same drugs were incubated for 24 h with the IC50 concentration and cells were harvested for genomic, transcriptomic, proteomic and phosphoproteomic analyses. The subsequent analysis revealed striking differences between the seven drugs. Principal component analysis shows two distinct clusters between approved and unapproved drugs. Furthermore, the transomic signature for the third-generation approved drug osimertinib was significantly different to that for the drug olmutinib which failed clinical development due to toxicity. Transomic analysis of EGFRi has the potential to identify important differences between successful drugs, drugs that failed in clinical development, and to identify non-EGFR targets that may overcome resistance to current drugs. This hypothesis is currently being investigated across various resistant and undruggable cancers to unlock novel therapeutic targets. Citation Format: Christopher J. Nicholson, Arudhir Singh, Caitlin Westberg Brown, Simon P. Fricker, Jon Hu, Samantha Dale Strasser. An integrated transomics approach reveals significant differences between EGFR inhibitors with the potential to identify novel targets to overcome EGFR resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB063.

Combination immune checkpoint inhibition (ICI) with antibodies targeting PD-1 and CTLA-4 provides superior outcomes compared to either monotherapy alone. This combination has been approved for advanced melanoma, metastatic colon cancer and others. However, combination therapy with anti-PD-1/CTLA-4 antibodies results in serious immune related adverse events (irAEs), presenting an obstacle for effective treatment with combination systemic anti-PD-1/CTLA-4. Intratumoral (IT) immunotherapy is a strategy to enhance local activity while decreasing systemic irAEs. While clinical testing of IT antibodies is underway, antibodies' high molecular weight may limit their local diffusion and retention time within tumors. RNAi is an emerging therapeutic modality well-suited for local clinical application of ICI. We have demonstrated that self-delivering RNAi therapeutics built on proprietary INTASYL™ technology specifically silence their targets in tissues without need for specialized formulations or delivery systems, and convey robust antitumor efficacy in vivo. Furthermore, multiple INTASYL compounds can be easily co-formulated into a multi-targeting therapeutic, providing specific silencing of multiple therapeutic targets in a single injection. Here, we present proof-of-concept (POC) in vivo data demonstrating synergistic efficacy of a novel INTASYL dual-targeting murine PD-1 (mPH-762) and CTLA-4 (27790) coformulation in PBS in a syngeneic CT26 model of murine colon cancer. Dual on-target silencing was first validated in murine T cells in vitro. In vivo, CT26 cells were implanted subcutaneously into female BALB/c mice. Vehicle (PBS) or INTASYL IT treatment commenced when tumors reached a mean threshold volume (150 mm3; Day 1) with doses given on Days 1, 4, 7, 10, and 13. Mice received a total 1 mg/dose with the dual-targeting INTASYL, comprised of 0.5 mg of each compound. Another group received the dual-targeting INTASYL at 2 mg/dose. Tumor volumes and body weights were recorded longitudinally and analyzed by area under the curve (AUC). Tumors were isolated on Day 15 and mechanistic immunomodulation of the tumor microenvironment (TME) was assessed by flow cytometry. IT INTASYL dual-targeting PD-1 and CTLA-4 elicited robust dose-associated antitumor efficacy that was superior to the identical total dose of either single-targeting INTASYL, when comparing mean tumor volume AUC, demonstrating antitumor synergy by the dual-targeting coformulation. On-target mechanistic immunomodulatory effects were observed in the TME. These data demonstrate POC synergistic efficacy of IT INTASYL dual-targeting CTLA-4/PD-1 in vivo, supporting further development to maximize efficacy and minimize irAEs. PH-762 is currently under clinical investigation in a Phase 1b study for advanced melanoma. Citation Format: Benjamin G. Cuiffo, Andrew Boone, Dingxue Yan, Melissa Maxwell, Brianna Rivest, James Cardia, Simon P. Fricker. INTASYL self-delivering RNAi therapeutic dual targeting PD-1 and CTLA-4 provides synergistic antitumor efficacy in the treatment of murine colon cancer in vivo. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5113.

Immune checkpoint inhibitor (ICI) anti-PD-1 antibody (mAb) monotherapy represented a significant advancement in cancer treatment, however most patients will ultimately progress, signaling the need for improvement. Combination approaches with other ICI mAbs may improve outcomes, however, systemic administration of immunostimulatory mAb combinations further increases risk for treatment-induced immune related adverse effects (irAEs). We have previously shown that intratumoral (IT) administration of PH-894, a self-delivering RNAi compound targeting BRD4 built on proprietary INTASYL™ technology, imparts tumor control in vitro and in vivo via effects on both T cells and tumor cells. Local priming of the immune response has shown promise toward potentiating the impact of systemic immunotherapy; therefore, we hypothesized that IT PH-894 might potentiate the efficacy of systemic anti-PD-1 mAb therapy. To assess this in vivo, an identical inoculum (5e05) of CT26 cells was implanted subcutaneously into the bilateral flanks of BALB/c mice. Vehicle (PBS; IT), anti-PD-1 mAb (0.1 mg/dose; intraperitoneal (IP)), PH-894 (0.5 mg/dose; IT) or combination anti-PD-1 mAb (0.1 mg/dose; IP) + PH-894 (0.5 mg/dose; IT) were administered, with IT doses limited to the tumor on the left flank only, on Days 1, 4, 7, 10 and 13. Tumors on the opposite flank were left untreated. Tumor volumes and body weights were recorded. Tumors, spleens, and lymph nodes were isolated for ex vivo mechanistic studies. The abscopal effects of IT PH-894 were confirmed in a bilateral Hepa1-6 model of murine hepatoma. In the CT26 model, as expected, growth of both tumors was inhibited with systemic anti-PD-1. Treatment with IT PH-894 provided a similar level of tumor control compared to treatment with IP anti-PD-1 mAb, both for the PH-894 directly-treated tumors, but in addition also towards the PH-894 untreated distal tumors, an abscopal impact. Additionally, IT PH-894 enhanced the antitumor efficacy of systemic anti-PD-1 mAb therapy, not only for the PH-894 locally treated tumors, but for the PH-894 untreated distal tumors. These data show that IT administered PH-894 potentiated the efficacy of systemic anti-PD-1 mAb, both locally and toward PH-894 untreated distal tumors. In addition, PH-894 silencing of BRD4 not only inhibited tumor growth at the local site of therapy, but also elicited an abscopal effect toward distal tumors, with efficacy similar to that provided by systemically administered anti-PD-1 mAb. These results indicate that IT PH-894 can potentiate the efficacy of systemic anti-PD-1 mAb, warranting further investigation of clinical applications in combination with anti-PD-1 mAbs toward improving patient outcomes. Citation Format: Benjamin Cuiffo, Melissa Maxwell, Dingxue Yan, Shenghua Zhou, Brianna Rivest, Andrew Boone, James Cardia, Simon P. Fricker. Local administration of BRD4-targeting self-delivering RNAi (PH-894) provides abscopal efficacy toward untreated distal tumors and potentiates the efficacy of systemic anti-PD-1 antibody therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4237.

The chemokine receptors CCR5 and CCR2b share 89% amino acid homology. CCR5 is a co-receptor for HIV and CCR5 antagonists have been investigated as inhibitors of HIV infection. We describe the use of two CCR5 antagonists, Schering-C (SCH-C), which is specific for CCR5, and TAK-779, a dual inhibitor of CCR5 and CCR2b, to probe the CCR5 inhibitor binding site using CCR5/CCR2b chimeric receptors. Compound inhibition in the different chimeras was assessed by inhibition of chemokine-induced calcium flux. SCH-C inhibited RANTES (regulated on activation, normal T cell expressed and secreted) (CCL5)-mediated calcium flux on CCR5 with an IC50 of 22.8 nM but was inactive against monocyte chemoattractant protein-1 (CCL2)-mediated calcium flux on CCR2b. However, SCH-C inhibited CCL2-induced calcium flux against a CCR5/CCR2b chimera consisting of transmembrane domains IV-VI of CCR5 with an IC50 of 55 nM. A sequence comparison of CCR5 and CCR2b identified a divergent amino acid sequence located at the junction of transmembrane domain V and second extracellular loop. Transfer of the CCR5 sequence KNFQTLKIV into CCR2b conferred SCH-C inhibition (IC50 of 122 nM) into the predominantly CCR2b chimera. Furthermore, a single substitution, R206I, conferred partial but significant inhibition (IC50 of 1023 nM) by SCH-C. These results show that a limited amino acid sequence is responsible for SCH-C specificity to CCR5, and we propose a model showing the interaction with CCR5 Ile(198).

We examined whether antagonism of the CXCR4 receptor ameliorates the loss of renal function following ischemia-reperfusion. CXCR4 is ubiquitously expressed on leukocytes, known mediators of renal injury, and on bone marrow hematopoietic stem cells (HSCs). Plerixafor (AMD3100, Mozobil) is a small-molecule CXCR4 antagonist that mobilizes HSCs into the peripheral blood and also modulates the immune response in in vivo rodent models of asthma and rheumatoid arthritis. Treatment with plerixafor before and after ischemic clamping ameliorated kidney injury in a rat model of bilateral renal ischemia-reperfusion. Serum creatinine and blood urea nitrogen were significantly reduced 24 h after reperfusion, as were tissue injury and cell death. Plerixafor prevented the renal increase in the proinflammatory chemokines CXCL1 and CXCL5 and the cytokine IL-6. Flow cytometry of kidney homogenates confirmed the presence of significantly fewer leukocytes with plerixafor treatment; additionally, myeloperoxidase activity was reduced. AMD3465, a monocyclam analog of plerixafor, was similarly renoprotective. Four weeks postreperfusion, long-term effects included diminished fibrosis, inflammation, and ongoing renal injury. The mechanism by which CXCR4 inhibition ameliorates AKI is due to modulation of leukocyte infiltration and expression of proinflammatory chemokines/cytokines, rather than a HSC-mediated effect. The data suggest that CXCR4 antagonism with plerixafor may be a potential option to prevent AKI.

Chemokines and their receptors are integral components of the immune response, regulating lymphocyte development, homing and trafficking, and playing a key role in the pathophysiology of many diseases. Chemokine receptors have, therefore, become the target for both small-molecule, peptide and antibody therapeutics. Chemokine receptors belong to the family of seven transmembrane receptor class A G protein-coupled receptors. The publication of the crystal structure of the archetypal class A seven transmembrane receptor protein rhodopsin, and other G protein-coupled receptors, including C-X-C chemokine receptor 4 and C-C chemokine receptor 5, provided the opportunity to create homology models of chemokine receptors. In this review, we describe an interdisciplinary approach to chemokine receptor modeling and the utility of this approach for structure-based drug design of chemokine receptor inhibitors.

Autologous hematopoietic stem cell (HSC) transplantation is an important therapeutic option for patients with non-Hodgkin's lymphoma and multiple myeloma. The primary source of HSC is from the peripheral blood which requires mobilization from the bone marrow. Current mobilization regimens include cytokines such as G-CSF and/or chemotherapy. However not all patients mobilize enough HSC to proceed to transplant. The chemokine receptor CXCR4 and its ligand CXCL12 are an integral part of the mechanism of HSC retention in the bone marrow niche. The discovery of plerixafor, a selective inhibitor of CXCR4, has provided a new additional means of mobilizing HSC for autologous transplantation. Plerixafor consists of two cyclam rings with a phenylenebis(methylene) linker. It inhibits CXCL12 binding to CXCR4 and subsequent downstream events including chemotaxis. The molecular interactions of plerixafor have been defined indicating a unique binding mode to CXCR4. Plerixafor rapidly mobilizes HSC within hours compared with the multi-day treatment required by G-CSF in mouse, dog and non-human primate. The mobilized cells once transplanted are capable of timely and endurable engraftment. Additionally CXCR4 has been implicated in the pathology of HIV, inflammatory disease and cancer and the pharmacology of plerixafor in various disease models is described.

In order to enter and infect human cells HIV must bind to CD4 in addition to either the CXCR4 or the CCR5 chemokine receptor. AMD11070 was the first orally available small molecule antagonist of CXCR4 to enter the clinic. Herein we report the molecular pharmacology of AMD11070 which is a potent inhibitor of X4 HIV-1 replication and the gp120/CXCR4 interaction. Using the CCRF-CEM T cell line that endogenously expresses CXCR4 we have demonstrated that AMD11070 is an antagonist of SDF-1α ligand binding (IC50 = 12.5 ± 1.3 nM), inhibits SDF-1 mediated calcium flux (IC50 = 9.0 ± 2.0 nM) and SDF-1α mediated activation of the CXCR4 receptor as measured by a Eu-GTP binding assay (IC50 =39.8 ± 2.5 nM) or a [(35)S]-GTPγS binding assay (IC50 =19.0 ± 4.1 nM), and inhibits SDF-1α stimulated chemotaxis (IC50 =19.0 ± 4.0 nM). AMD11070 does not inhibit calcium flux of cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7, or ligand binding to CXCR7 and BLT1, demonstrating selectivity for CXCR4. In addition AMD11070 is able to inhibit the SDF-1β isoform interactions with CXCR4; and N-terminal truncated variants of CXCR4 with equal potency to wild type receptor. Further mechanistic studies indicate that AMD11070 is an allosteric inhibitor of CXCR4.

A series of CCR5 antagonists representing the thiophene-3-yl-methyl ureas were designed that met the pharmacological criteria for HIV-1 inhibition and mitigated a human ether-a-go-go related gene (hERG) inhibition liability. Reducing lipophilicity was the main design criteria used to identify compounds that did not inhibit the hERG channel, but subtle structural modifications were also important. Interestingly, within this series, compounds with low hERG inhibition prolonged the action potential duration (APD) in dog Purkinje fibers, suggesting a mixed effect on cardiac ion channels.

Since the introduction of the monomeric orally bioavailable anti-arthritic gold compound auranofin in 1985, and the success of the platinum-based anti-cancer drugs, there has been a great deal of interest in the use of gold compounds for cancer therapy. However this early promise has not materialized into an approved drug in spite of extensive and innovative efforts in gold chemistry. Therefore, in the light of this lack of success, the strategies for the biological evaluation of potential gold-based anti-cancer drugs are discussed. It is proposed that the biological testing strategy should be multi-faceted incorporating an understanding of the molecular properties of the compounds under investigation related to their behaviour in a biological environment, an evaluation of their comparative in vitro potency against tumor cells, ascertaining the biochemical mechanism of action and target identification to aid in medicinal chemistry design, evaluation of in vivo activity in relevant tumor models, and an understanding of their toxicological and pharmacokinetic properties. This strategy will be exemplified with work on Au(III) cyclometallated complexes in which an integrated approach to the search for new metal-based anticancer drugs was adopted, incorporating in vitro screening, in vivo human tumor xenograft models, and mechanistic studies. The importance of mechanistic studies which have led to the identification of new molecular targets for gold drugs, and in vivo evaluation are emphasized.

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.

Chemokines, small proinflammatory chemoattractant cytokines that bind to specific G-protein-coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The chemokine CXCL12 [stromal cell-derived factor-1 (SDF-1)] binds primarily to CXC receptor 4 (CXCR4; CD184). The binding of CXCL12 to CXCR4 induces intracellular signaling through several divergent pathways initiating signals related to chemotaxis, cell survival and/or proliferation, increase in intracellular calcium, and gene transcription. CXCR4 is expressed on multiple cell types including lymphocytes, hematopoietic stem cells, endothelial and epithelial cells, and cancer cells. The CXCL12/CXCR4 axis is involved in tumor progression, angiogenesis, metastasis, and survival. This pathway is a target for therapeutics that can block the CXCL12/CXCR4 interaction or inhibit downstream intracellular signaling. Clin Cancer Res; 16(11); 2927–31. ©2010 AACR.

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 chemokine receptor CXCR4 is widely expressed on different cell types, is involved in leukocyte chemotaxis, and is a co-receptor for HIV. AMD3100 has been shown to be a CXCR4 receptor antagonist, and to block HIV infection of T-tropic, X4-using, virus in vitro and in vivo. AMD3100 is an effective mobilizer of hematopoietic stem cells and is being investigated in clinical trials in multiple myeloma and non-Hodgkins lymphoma patients. Using the CCRF-CEM T-cell line that constitutively expresses CXCR4 we confirmed that AMD3100 was an antagonist of SDF-1/CXCL12 ligand binding (IC50=651+/-37 nM). We have also shown that AMD3100 inhibits SDF-1 mediated GTP-binding (IC50=27+/-2.2 nM), SDF-1 mediated calcium flux (IC50=572+/-190 nM), and SDF-1 stimulated chemotaxis (IC50=51+/-17 nM). AMD3100 did not inhibit calcium flux against cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7 when stimulated with their cognate ligands, nor did it inhibit receptor binding of LTB4. AMD3100 did not, on its own, induce a calcium flux in the CCRF-CEM cells, which express multiple GPCRs including CXCR4, CCR4 and CCR7. Furthermore, AMD3100 neither stimulated GTP-binding, an assay for GPCR activation, in CEM cell membranes; nor chemotaxis of CCRF-CEM cells. These data therefore demonstrate that AMD3100 is a specific antagonist of CXCR4, is not cross-reactive with other chemokine receptors, and is not an agonist of CXCR4.

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.

In order to enter and infect human cells HIV must bind to the CD4 receptor in addition to either CXCR4 or CCR5. {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 was the first orally available small molecule inhibitor of CXCR4 to enter the clinic. Here, we report in detail the molecular pharmacology of {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 which is a potent inhibitor of X4 HIV-1 replication in various CD4+ T cell lines, CXCR4-transfected cell lines and in PBMC (IC50 values of 14 ± 3 nM). In addition, {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 potently inhibited cell fusion between a CHO-K1 cell line expressing viral gp120 and the P4-R5 MAGI cells which express CD4 and CXCR4 with an IC50 of 1.5 ± 0.3 nM. No antiviral activity was observed with {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 against CCR5-using (R5) HIV-1 replication. Using CD4+ T cell lines that endogenously express CXCR4 we demonstrate that {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 is an antagonist of CXCL-12 (SDF-1a)-ligand binding (IC50: 12.5 ± 1.3 nM), inhibits CXCL-12-mediated signaling (IC50: 9 ± 2 nM) and that it inhibits CXCL-12-mediated chemotaxis (IC50: 19 ± 4 nM). {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 does not inhibit chemokine-induced Ca2+-signaling in cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7, demonstrating the compound selectivity for the CXCR4 receptor. In addition, {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 is able to inhibit the SDF-1beta isoform interactions with CXCR4 and N-terminal truncated variants of CXCR4 with equal potency as to the wild type CXCR4 receptor. These data indicate that {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 is an allosteric antagonist of CXCR4. A proof-of-concept clinical trial has shown that {"type":"entrez-protein","attrs":{"text":"AMD11070","term_id":"985559755","term_text":"AMD11070"}}AMD11070 can reduce the viral load of X4 HIV-1 in HIV-1-infected persons. Together these data further support to the potential beneficial role of orally bioavailable CXCR4 inhibitors as a therapeutic option for HIV/AIDS treatment.

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.

Pharmacological manipulation of CXCR4 has proven clinically useful for mobilization of stem and progenitor cells and in several preclinical models of disease. It is a key component in the localization of leukocytes and stem cells. For patients with multiple myeloma and non-Hodgkin’s Lymphoma, treatment with plerixafor, an inhibitor of CXCL12 binding to CXCR4, plus G-CSF mobilizes stem cells for autologous transplantation to a greater degree than the treatment with G-CSF alone, and in some cases when patients could not be mobilized with cytokines, chemotherapy, or the combination. Stem cells from healthy donors mobilized with single agent plerixafor have been used for allogeneic transplantation in acute myelogenous leukemia (AML) patients, although this is still in the early phase of clinical development. Plerixafor is also undergoing evaluation to mobilize tumor cells in patients with AML and chronic lymphocytic leukemia (CLL) to enhance the effectiveness of chemotherapy regimens. Plerixafor’s effect on neutrophils may also restore circulating neutrophil counts to normal levels in patients with chronic neutropenias such as in WHIMs syndrome. Other areas where inhibition of CXCR4 may be useful based upon preclinical or clinical data include peripheral vascular disease, autoimmune diseases such as rheumatoid arthritis, pulmonary inflammation, and HIV.

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.

CXCR4 is widely expressed in multiple cell types, and is involved in neonatal development, hematopoiesis, and lymphocyte trafficking and homing. Disruption of the CXCL12/CXCR4 interaction has been implicated in stem cell mobilization. Additionally CXCR4 is a co-receptor for HIV. Selective small molecule antagonists of CXCR4 therefore have therapeutic potential. AMD3465 is an N-pyridinylmethylene monocyclam CXCR4 antagonist which can block infection of T-tropic, CXCR4-using HIV. Using the CCRF-CEM T-cell line which expresses CXCR4 we have demonstrated that AMD3465 is an antagonist of SDF-1 ligand binding ( K i of 41.7 ± 1.2 nM), and inhibits SDF-1 mediated signaling as shown by inhibition of GTP binding, calcium flux, and inhibition of chemotaxis. AMD3465 is selective for CXCR4 and does not inhibit chemokine-stimulated calcium flux in cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7, nor does it inhibit binding of LTB 4 to its receptor, BLT1. The pharmacokinetics of AMD3465 was investigated in mice and dogs. Absorption was rapid following subcutaneous administration. AMD3465 was cleared from dog plasma in a biphasic manner with a terminal half-life of 1.56–4.63 h. Comparison of exposure to the intravenous and subcutaneous doses indicated 100% bioavailability following subcutaneous administration. AMD3465 caused leukocytosis when administered subcutaneously in mice and dogs, with peak mobilization occurring between 0.5 and 1.5 h following subcutaneous dosing in mice and with maximum peak plasma concentration of compound preceding peak mobilization in dogs, indicating that AMD3465 has the potential to mobilize hematopoietic stem cells. These data demonstrate the therapeutic potential for the CXCR4 antagonist AMD3465.

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.

CXC chemokine receptor (CXCR)4 is an HIV coreceptor and a chemokine receptor that plays an important role in several physiological and pathological processes, including hematopoiesis, leukocyte homing and trafficking, metastasis, and angiogenesis. This receptor belongs to the class A family of G protein-coupled receptors and is a validated target for the development of a new class of antiretroviral therapeutics. This study compares the interactions of three structurally diverse small-molecule CXCR4 inhibitors with the receptor and is the first report of the molecular interactions of the nonmacrocyclic CXCR4 inhibitor (S)-N'-(1H-benzimidazol-2-ylmethyl)-N'-(5,6,7,8-tetrahydroquinolin-8-yl)butene-1,4-diamine (AMD11070). Fourteen CXCR4 single-site mutants representing amino acid residues that span the entire putative ligand binding pocket were used in this study. These mutants were used in binding studies to examine how each single-site mutation affected the ability of the inhibitors to compete with (125)I-stromal-derived factor-1alpha binding. Our data suggest that these CXCR4 inhibitors bind to overlapping but not identical amino acid residues in the transmembrane regions of the receptor. In addition, our results identified amino acid residues that are involved in unique interactions with two of the CXCR4 inhibitors studied. These data suggest an extended binding pocket in the transmembrane regions close to the second extracellular loop of the receptor. Based on site-directed mutagenesis and molecular modeling, several potential binding modes were proposed for each inhibitor. These mechanistic studies might prove to be useful for the development of future generations of CXCR4 inhibitors with improved clinical pharmacology and safety profiles.

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.

CXCR4 is a major receptor for CXCL12 and is known to participate in multiple physiological systems. The present study tested a second generation CXCR4 antagonist, AMD3465, for effects on highly defined models of Th1- and Th2-cell-mediated hypersensitivity-type pulmonary granuloma formation. Type-1 and type-2 granulomas were induced, respectively, by intravenous challenge of sensitized CBA/J mice with Mycobacteria bovis purified protein derivative- or Schistosoma mansoni egg antigen-coated beads. Before challenge, mice were implanted with osmotic pumps releasing AMD3465 at 5 microg/hour (6 mg/kg/day). Compared to vehicle, AMD3465 had minimal effect on type-1 inflammation or cytokine responses in draining lymph nodes, but the type-2 inflammation was significantly abrogated with reductions in lesion size and eosinophil content as well as abrogated interleukin (IL)-5, IL-10, and IL-13 cytokine production in draining lymph nodes. The biased effect of AMD3465 correlated with greater CXCR4 ligand expression in the type-2 model. Treatment during a primary response impaired lymph node IL-2 production after both Mycobacteria bovis purified protein derivative and Schistosoma mansoni egg antigen challenge indicating an unbiased effect during immune induction. In summary, CXCR4 blockade inhibited eosinophil recruitment during type-2 granuloma formation and interfered with primary and secondary T-cell activation events in lymphoid tissue, suggesting potential therapeutic application for chronic hypersensitivity diseases.

AMD3100, a bicyclam antagonist of the chemokine receptor CXCR4, has been shown to induce rapid mobilization of CD34(+) hematopoietic cells in mice, dogs, and humans, offering an alternative to G-CSF mobilization of peripheral-blood hematopoietic stem cells. In this study, AMD3100-mobilized CD34(+) cells were phenotypically analyzed, marked with Neo(R)-containing retroviral vectors, and subsequently transplanted into myeloablated rhesus macaques. We show engraftment of transduced AMD3100-mobilized CD34(+) cells with Neo(R) gene marked myeloid and lymphoid cells up to 32 months after transplantation, demonstrating the ability of AMD3100 to mobilize true long-term repopulating hematopoietic stem cells. More AMD3100-mobilized CD34(+) cells are in the G(1) phase of the cell cycle and more cells express CXCR4 and VLA-4 compared with G-CSF-mobilized CD34(+) cells. In vivo gene marking levels obtained with AMD3100-mobilized CD34(+) cells were better than those obtained using CD34(+) cells mobilized with G-CSF alone. Overall, these results indicate that AMD3100 mobilizes a population of hematopoietic stem cells with intrinsic characteristics different from those of hematopoietic stem cells mobilized with G-CSF, suggesting fundamental differences in the mechanism of AMD3100-mediated and G-CSF-mediated hematopoietic stem cell mobilization. Thus, AMD3100-mobilized CD34(+) cells represent an alternative source of hematopoietic stem cells for clinical stem cell transplantation and genetic manipulation with integrating retroviral vectors.

Chemokine receptors have been implicated in several disease processes such as acute and chronic inflammation, cancer, and allograft rejection and are therefore targets for drug development. The chemokine receptors CCR5 and CXCR4 are of particular interest as they serve as entry cofactors for human immunodeficiency virus. These receptors are members of the G protein-coupled receptor (GPCR) family. In this respect, assessing GPCR activation by GTP binding is an important tool to study the early stage of signal transduction. The assay normally utilizes the non-hydrolysable GTP analogue guanosine 5'-gamma-[35S]thiotriphosphate. In order to avoid the problems involved in working with radioactivity, a new non-radioactive version of the assay was developed using a europium-labeled GTP analogue in which europium-GTP binding can be assayed using time-resolved fluorescence. The assay was optimized for CXCR4 and CCR5 and validated for screening of chemokine antagonists using the small molecule CXCR4 antagonist AMD3100 and CCR5 antagonists.

Peripheral-blood mononuclear cells (PBMCs) mobilized with AMD3100, a CXCR4 antagonist, combined with granulocyte colony-stimulating factor (G-CSF) have reconstituted autologous hematopoiesis in cancer patients following myeloablative conditioning. The engraftment potential of PBMCs mobilized with AMD3100 alone, however, has remained unproven. We therefore studied AMD3100-mobilized PBMCs in a canine model. Four dogs received 920 cGy total body irradiation (TBI) before infusion of autologous AMD3100-mobilized PBMCs (median CD34 cell count, 3.9 × 106/kg). Neutrophil (> 0.5 × 109/L [500/μL]) and platelet (> 20 ×/109/L [> 20 000/μL]) recoveries occurred at medians of 9 (range, 7-10) days and 25 (range, 23-38) days, respectively, after TBI, and all dogs had normal marrow function at 1 year after transplantation. To evaluate the long-term engraftment potential of AMD3100-mobilized PBMCs, 5 dogs were given 920 cGy TBI followed by infusion of AMD3100-mobilized PBMCs (median CD34 cell dose, 4.7 × 106/kg) from their dog leukocyte antigen (DLA)-identical littermates. Neutrophil and platelet recoveries occurred at medians of 8 (range, 8-10) days and 26 (range, 26-37) days, respectively, after TBI. With a median follow-up of 53 (range, 33-61) weeks, recipients' marrow function was normal, and blood-donor chimerism levels were 97% to 100%. In summary, both autologous and allogeneic AMD3100-mobilized PBMCs led to prompt and durable engraftment in dogs after 920 cGy TBI.