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II Clinical Trials (ii + clinical_trials)
Kinds of II Clinical Trials Selected AbstractsThe effects of telomerase inhibition on prostate tumor-initiating cellsINTERNATIONAL JOURNAL OF CANCER, Issue 2 2010Calin O. Marian Abstract Prostate cancer is the most common malignancy in men, and patients with metastatic disease have poor outcome even with the most advanced therapeutic approaches. Most cancer therapies target the bulk tumor cells, but may leave intact a small population of tumor-initiating cells (TICs), which are believed to be responsible for the subsequent relapse and metastasis. Using specific surface markers (CD44, integrin ,2,1 and CD133), Hoechst 33342 dye exclusion, and holoclone formation, we isolated TICs from a panel of prostate cancer cell lines (DU145, C4-2 and LNCaP). We have found that prostate TICs have significant telomerase activity which is inhibited by imetelstat sodium (GRN163L), a new telomerase antagonist that is currently in Phase I/II clinical trials for several hematological and solid tumor malignancies. Prostate TICs telomeres were of similar average length to the telomeres of the main population of cells and significant telomere shortening was detected in prostate TICs as a result of imetelstat treatment. These findings suggest that telomerase inhibition therapy may be able to efficiently target the prostate TICs in addition to the bulk tumor cells, providing new opportunities for combination therapies. [source] Haematopoietic stem cell transplantation in the treatment of severe autoimmune disease: results from phase I/II studies, prospective randomized trials and future directionsCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2005A. Tyndall Summary Around 700 patients have received an autologous haematopoietic stem cell transplant (HSCT) as treatment for a severe autoimmune disease (AD). The majority of these have been within the context of phase I/II clinical trials and following international guidelines proposed 7 years ago. In general, a positive benefit/risk ratio has led to phase III prospective randomized controlled trials in multiple sclerosis (MS), systemic sclerosis (SSc) and rheumatoid arthritis (RA) in Europe. In the US, similar trials are being planned for SSc, MS and systemic lupus erythematosus (SLE). Transplant related mortality (TRM) has fallen in all disease subgroups since the inception due to more appropriate patient selection, and so far a clear advantage of the more intense myeloablative regimens in terms of remission induction and relapse rate has not emerged. Although each AD has a different profile, over a third of patients have sustained a durable remission, often with no further need for immunosuppressive drugs. In those who relapsed, many responded to agents which pre transplant had been ineffective. The study of immune reconstitution and gene expression pre and post HSCT is being undertaken to further understand the mechanism of autoimmunity. [source] Comparative Solution Equilibrium Study of the Interactions of Copper(II), Iron(II) and Zinc(II) with Triapine (3-Aminopyridine-2-carbaldehyde Thiosemicarbazone) and Related LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Éva A. Enyedy Abstract The interactions of CuII, ZnII and FeII with Triapine (3-aminopyridine-2-carbaldehyde thiosemicarbazone), which is currently undergoing phase II clinical trials as a chemotherapeutic antitumour agent, were investigated in a water/DMSO mixture. The proton-dissociation constants of the ligands, the stability constants and the coordination modes of the metal complexes formed were determined by pH-potentiometric, UV/Vis spectrophotometric, EPR, 1H NMR spectroscopic and ESI-MS methods. Two N-terminally dimethylated derivatives of Triapine were also studied. Mono- and bis-ligand complexes in different protonation states were identified. Furthermore, the formation of the dinuclear species [Cu2L3]+ was confirmed for all ligands by EPR spectroscopy and ESI-MS measurements. The results showed that the N-terminally dimethylated ligands are much more potent chelators than Triapine for the divalent metal ions studied. All three ligands formed the least stable complexes with ZnII, whereas the FeII complexes were somewhat more stable than the corresponding CuII species. [source] Clofarabine in the treatment of poor risk acute myeloid leukaemiaHEMATOLOGICAL ONCOLOGY, Issue 3 2010Janusz Krawczyk Abstract Clofarabine is a second generation nucleoside analogue. It inhibits DNA repair and activates the mitochondrial apoptotic pathway leading to cell death. In vitro clofarabine has demonstrated synergy with daunorubicin and Ara-C and in phase II clinical trials has shown promising activity in poor risk Acute myeloid leukaemia (AML) patients. In our institution over a 24 month period 22 AML patients (11 M, 11 F) with poor risk features, deemed unsuitable for standard therapy, were treated with clofarabine, alone (eight patients) or in combination (14 patients) for up to three cycles of treatment. The median age was 67.5 years (24,76) with 16 patients > 60 years. At the time of treatment 18 patients had active AML. Four patients intolerant of standard induction received clofarabine as consolidation. The overall response rate (ORR) for the 18 patients with active AML was 61%, nine patients (50%) achieving a complete response (CR). Induction and consolidation were well tolerated with no unexpected toxicities. Predictably, all patients developed grade 4 neutropenia but the median duration was only 20 days (17,120). Induction mortality was acceptable at 17%. In conclusion, clofarabine (alone or in combination) is active in poor risk AML with an acceptable safety profile and should be considered a potential option in poor risk AML patients. Copyright © 2009 John Wiley & Sons, Ltd. [source] The Virtual International Stroke Trials Archive (VISTA): results and impact on future stroke trials and management of stroke patientsINTERNATIONAL JOURNAL OF STROKE, Issue 2 2010C. Weimar Background The Virtual International Stroke Trials Archive was established to improve stroke care and trial design through the collation, categorization and potential access to data sets from clinical trials for the treatment of stroke. Methods Virtual International Stroke Trials Archive currently provides access to a combined data set of 29 anonymised acute stroke trials and one acute stroke registry with data on >27 500 patients aged between 18 and 103 (mean 71) years. Results Virtual International Stroke Trials Archive has facilitated research across a broad canvas. The prognosis was poor in patients with very high blood pressure at the time of admission or with a wide variability of systolic blood pressure during the acute phase. The late occurrence of hyperthermia following an ischaemic stroke worsens the prognosis. Stroke lateralisation is not an important predictor of cardiac adverse events or 90-day mortality. Haemorrhagic transformation is seen frequently in patients with cardio-embolic strokes and is associated with a poor prognosis when occurring after the acute phase. Virtual International Stroke Trials Archive has allowed various prognostic models for patients with ischaemic or haemorrhagic stroke to be established and validated. More direct outcomes such as lesion volume can be useful in phase II clinical trials for determining whether a phase III trial should be undertaken. New outcome measures such as ,home time' may also strengthen future trials. On a worldwide level, the prognosis of stroke patients differs considerably between various countries. Conclusion Virtual International Stroke Trials Archive provides an excellent opportunity for analysis of natural history data and prognosis. It has the potential to influence clinical trial design and implementation through exploratory data analyses. [source] Review article: gene therapy, recent developments and future prospects in gastrointestinal oncologyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 8 2010Y. Touchefeu Aliment Pharmacol Ther 2010; 32: 953,968 Summary Background, Gene therapy consists of the introduction of genetic material into cells for a therapeutic purpose. A wide range of gene therapy vectors have been developed and used for applications in gastrointestinal oncology. Aim, To review recent developments and published clinical trials concerning the application of gene therapy in the treatment of liver, colon and pancreatic cancers. Methods, Search of the literature published in English using the PubMed database. Results, A large variety of therapeutic genes are under investigation, such as tumour suppressor, suicide, antiangiogenesis, inflammatory cytokine and micro-RNA genes. Recent progress concerns new vectors, such as oncolytic viruses, and the synergy between viral gene therapy, chemotherapy and radiation therapy. As evidence of these basic developments, recently published phase I and II clinical trials, using both single agents and combination strategies, in adjuvant or advanced disease settings, have shown encouraging results and good safety records. Conclusions, Cancer gene therapy is not yet indicated in clinical practice. However, basic and clinical advances have been reported and gene therapy is a promising, new therapeutic approach for the treatment of gastrointestinal tumours. [source] Review article: specifically targeted anti-viral therapy for hepatitis C , a new era in therapyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 1 2010C. M. Lange Aliment Pharmacol Ther 2010; 32: 14,28 Summary Background, Novel, directly acting anti-viral agents, also named ,specifically targeted anti-viral therapy for hepatitis C' (STAT-C) compounds, are currently under development. Aim, To review the potential of STAT-C agents which are currently under clinical development, with a focus on agents that target HCV proteins. Methods, Studies evaluating STAT-C compounds were identified by systematic literature search using PubMed as well as databases of abstracts presented in English at recent liver and gastroenterology congresses. Results, Numerous directly-acting anti-viral agents are currently under clinical phase I,III evaluation. Final results of phase II clinical trials evaluating the most advanced compounds telaprevir and boceprevir indicate that the addition of these NS3/4A protease inhibitors to pegylated interferon-alfa and ribavirin strongly improves the chance to achieve a SVR in treatment-naive HCV genotype 1 patient as well as in prior nonresponders and relapsers to standard therapy. Monotherapy with directly acting anti-virals is not suitable. NS5B polymerase inhibitors in general have a lower anti-viral efficacy than protease inhibitors. Conclusions, STAT-C compounds in addition to pegylated interferon-alfa and ribavirin can improve SVR rates at least in HCV genotype 1 patients. Future research needs to evaluate whether a SVR can be achieved by combination therapies of STAT-C compounds in interferon-free regimens. [source] Tyrosine kinase inhibitors: From rational design to clinical trialsMEDICINAL RESEARCH REVIEWS, Issue 6 2001Peter Traxler Abstract Protein kinases play a crucial role in signal transduction as well as in cellular proliferation, differentiation, and various regulatory mechanisms. The inhibition of growth related kinases, especially tyrosine kinases, might provide new therapies for diseases such as cancer. The progress made in the crystallization of protein kinases has confirmed that the ATP-binding domain of tyrosine kinases is an attractive target for drug design. Three successful examples of drug design at Novartis using a tyrosine kinase as a molecular target are described. PKI166, a pyrrolo[2,3,- d]pyrimidine derivative, is a dual inhibitor of both the EGFR and the ErbB2 kinases. The compound entered clinical trials in 1999, based on its favorable preclinical profile: potent inhibition of EGF-mediated signalling in cells, in vivo antitumor activity in several EGFR overexpressing xenograft tumor models in nude mice, long-lasting inhibition of EGF-stimulated EGFR autophosphorylation in tumor tissue, good oral bioavailability in animals, and no prohibitive in vitro and in vivo toxicity findings. The anilino-phthalazine derivative PTK787/ZK222584 (Phase I, co-developed by Schering AG, Berlin) is a potent and selective inhibitor of both the KDR and Flt-1 kinases with interesting anti-angiogenic and pharmacokinetic properties (orally bioavailable). STI571 (GlivecÔ, GleevecÔ), a phenylamino-pyrimidine derivative, is a potent inhibitor of the Abl tyrosine kinase, which is present in 95% of patients with chronic myelogenous leukemia (CML). The compound specifically inhibits proliferation of v-Abl and Bcr-Abl expressing cells (including cells from CML patients) and shows anti-tumor activity as a single agent in animal models at well-tolerated doses. Pharmacologically relevant concentrations are achieved in the plasma of animals (oral administration). Promising data from phase I and II clinical trials in CML patients (98% haematological response rate in Phase I) support the fact that the STI571 represents a new treatment modality for CML. In addition, potent inhibition of the PDGFR and c-Kit tyrosine kinases also indicates its possible clinical use in solid tumors. © 2001 John Wiley & Sons, Inc. Med Res Rev, 21, No. 6, 499,512, 2001 [source] In vitro metabolism of , -lapachone (ARQ 501) in mammalian hepatocytes and cultured human cellsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2009Xiu-Sheng Miao ARQ 501 (3,4-dihydro-2,2-dimethyl-2H -naphthol[1,2-b]pyran-5,6-dione, , -lapachone) is an anticancer agent, currently in multiple phase II clinical trials as monotherapy and in combination with other cytotoxic drugs. This study focuses on in vitro metabolism in cryopreserved hepatocytes from mice, rats, dogs and humans using [14C]-labeled ARQ 501. Metabolite profiles were characterized using liquid chromatography/mass spectrometry combined with an accurate radioactivity counter. Ion trap mass spectrometry was employed for further structural elucidation. A total of twelve metabolites were detected in the mammalian hepatocytes studied; all of which but one were generated from phase II conjugation reactions. Ten of the observed metabolites were produced by conjugations occurring at the reduced ortho -quinone carbonyl groups of ARQ 501. The metabolite profiles revealed that glucuronidation was the major biotransformation pathway in mouse and human hepatocytes. Monosulfation was the major pathway in dog, while, in rat, it appears glucuronidation and sulfation pathways contributed equally. Three major metabolites were found in rats: monoglucuronide M1, monosulfate M6, and glucuronide-sulfate M9. Two types of diconjugation metabolites were formed by attachment of the second glycone to an adjacent hydroxyl or to an existing glycone. Of the diconjugation metabolites, glucosylsulfate M10, diglucuronide M5, and glucuronide-glucoside M11 represent rarely observed phase II metabolites in mammals. The only unconjugated metabolite was generated through hydrolysis and was observed in rat, dog and human hepatocytes. ARQ 501 appeared less stable in human hepatocytes than in those of other species. To further elucidate the metabolism of ARQ 501 in extrahepatic sites, its metabolism in human kidney, lung and intestine cells was also studied, and only monoglucuronide M1 was observed in all the cell types examined. Copyright © 2008 John Wiley & Sons, Ltd. [source] Hemospan: Design Principles for a New Class of Oxygen TherapeuticARTIFICIAL ORGANS, Issue 2 2009Kim D. Vandegriff Abstract Hemoglobin-based oxygen carriers have been under development for decades, but safety concerns have prevented commercial approval. Early designs for modified hemoglobins by polymerization or intramolecular cross-linking reactions increased molecular size and decreased oxygen affinity, but all exhibited side effects of vasoconstriction and reduced blood flow. A new strategy has been established by applying principles of oxygen transport to cell-free hemoglobin. Sangart has developed a new oxygen therapeutic, Hemospan, using site-specific, poly(ethylene) glycol conjugation chemistry designed on two principles: (i) increased macromolecular size to prolong intravascular retention time, and (ii) increased oxygen affinity to prevent premature oxygen offloading in arterioles. In contrast to early-generation products, Hemospan infusion maintains normal arteriolar vascular tone and capillary flow. Phase I and Phase II clinical trials have been completed, showing that Hemospan is well-tolerated in humans, with evidence of efficacy to impart hemodynamic stability in surgical patients under anesthesia. Phase III trials in orthopedic surgery have recently completed enrollment in Europe. [source] CA19-9 as a predictor of tumor response and survival in patients with advanced pancreatic cancer treated with gemcitabine based chemotherapyASIA-PACIFIC JOURNAL OF CLINICAL ONCOLOGY, Issue 2 2010Nazik HAMMAD Abstract Aims: The aim of this study was to determine the predictive role of pretreatment carbohydrate antigen 19-9 (CA19-9) measurement and its change after one cycle of gemcitabine-based therapy for response, time to progression (TTP) and overall survival (OS). Methods: Analyses were derived from three consecutive gemcitabine-containing phase II clinical trials between 1997 and 2004. Results: A total of 111 patients with pancreas cancer was studied. Baseline CA19-9 concentrations were dichotomized near the median. Lower baseline CA19-9 levels were positively associated with OS (median 9.1 vs 6.1 months, P = 0.0057) and TTP (median 6.4 vs 4.2 months, P = 0.0044). The covariate adjusted hazard ratio (HR) for progression among patients with baseline CA19-9 , 1000 ng/mL was HR = 1.94 (95% CI 1.24,3.02), with P = 0.0035. The covariate adjusted risk of death among patients with baseline CA19-9 , 1000 ng/ml was similarly elevated: HR = 1.90 (95% CI 1.23,2.94), with P = 0.0039. Change in CA19-9 levels from baseline to the end of treatment cycle 1 did not predict objective response (P = 0.75). There was somewhat longer OS (median 8.7 vs 7.1 months) and TTP (median 7.1 vs 5.4 months) in patients with ,50% reduction in serum CA19-9 concentrations, but this was not statistically significant (P = 0.74 and 0.81, respectively). Conclusion: Baseline CA19-9 levels may predict survival in patients with advanced pancreas cancer. The change in CA19-9 levels determined within 1 month of the initiation of therapy did not predict treatment outcome. [source] Ultra scale-down studies of the effect of shear on cell quality; Processing of a human cell line for cancer vaccine therapyBIOTECHNOLOGY PROGRESS, Issue 5 2009Ryan McCoy Abstract Whole cell therapy is showing potential in the clinic for the treatment of many chronic diseases. The translation of laboratory-scale methods for cell harvesting and formulation to commercial-scale manufacturing offers major bioprocessing challenges. This is especially the case when the cell properties determine the final product effectiveness. This study is focused on developing an ultra scale-down method for assessing the impact of the hydrodynamic environment on human cells that constitute the therapeutic product. Small volumes of a prostate cancer cell line, currently being developed in late phase II clinical trials as an allogeneic whole cell vaccine therapy for prostate cancer, were exposed to hydrodynamic shear rates similar to those present in downstream process, formulation and vial filling operations. A small scale rotating disc shear device (20 mL) was used over a range of disc speeds to expose cells to maximum shear rates ranging from 90 × 103 to 175 × 103 s -1 (equivalent maximum power dissipation rates of 14 × 103 to 52 × 103 W kg -1). These cells were subsequently analyzed for critical cell quality attributes such as the retention of membrane integrity and cell surface marker profile and density. Three cell surface markers (CD9, CD147, and HLAA-C) were studied. The cell markers exhibited different levels of susceptibility to hydrodynamic shear but in all cases this was less than or equal to the loss of membrane integrity. It is evident that the marker, or combination or markers, which might provide the required immunogenic response, will be affected by hydrodynamic shear environment during bioprocessing, if the engineering environment is not controlled to within the limits tolerated by the cell components. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Enhanced killing of B lymphoma cells by granulocyte colony-stimulating factor-primed effector cells and Hu1D10 , a humanized human leucocyte antigen DR antibodyBRITISH JOURNAL OF HAEMATOLOGY, Issue 4 2002Bernhard Stockmeyer Summary. Antibody-based approaches have become a novel treatment modality for lymphoma patients. Humanized 1D10 (Hu1D10; Remitogen) is among the antibodies that are currently under evaluation in phase II clinical trials in lymphoma patients. The 1D10 antibody is directed against a polymorphic epitope on the ,-chain of human leucocyte antigen (HLA) class II. We found expression of the 1D10 epitope on B cells and monocytes from approximately 50% of healthy donors. Analyses of 1D10 expression on malignant cells revealed that approximately half of the HLA class II-positive haematological malignancies expressed the 1D10 epitope. In whole blood antibody-dependent cellular cytotoxicity (ADCC) assays, Hu1D10 was more effective than rituxan in killing malignant ARH-77 B cells. Interestingly, Hu1D10-mediated lymphoma cell lysis was significantly enhanced when blood from granulocyte colony-stimulating factor (G-CSF)-treated patients was compared with blood from healthy controls. Analyses of the relevant effector cell populations revealed that Fc,RI (CD64)-positive polymorphonuclear cells were critical for enhanced Hu1D10-mediated lymphoma killing during G-CSF therapy, while the same effector cell population induced only marginal lysis with rituxan. Furthermore, Hu1D10 was highly effective in inducing apoptosis in primary lymphoma cells from B chronic lymphocytic leukaemia patients. These preclinical results form the basis for a phase I/II clinical trial of Hu1D10 in combination with G-CSF. [source] FTY720 (fingolimod) in Multiple Sclerosis: therapeutic effects in the immune and the central nervous systemBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2009Volker Brinkmann FTY720 (fingolimod) is a first-in-class sphingosine 1-phosphate (S1P) receptor modulator that was highly effective in Phase II clinical trials for Multiple Sclerosis (MS). FTY720 is phosphorylated in vivo by sphingosine kinase-2 to form the active moiety FTY720-phosphate that binds to four of the five G protein-coupled S1P receptor subtypes. Studies using conditional S1P1 receptor-deficient and sphingosine kinase-deficient mice showed that the egress of lymphocytes from lymph nodes requires signalling of lymphocytic S1P1 receptors by the endogenous ligand S1P. The S1P mimetic FTY720-phosphate causes internalization and degradation of cell membrane-expressed S1P1, thereby antagonizing S1P action at the receptor. In models of human MS and demyelinating polyneuropathies, functional antagonism of lymphocytic S1P1 slows S1P-driven egress of lymphocytes from lymph nodes, thereby reducing the numbers of autoaggressive TH17 cells that recirculate via lymph and blood to the central nervous system and the sciatic/ischiatic nerves. Based on its lipophilic nature, FTY720 crosses the blood,brain barrier, and ongoing experiments suggest that the drug also down-modulates S1P1 in neural cells/astrocytes to reduce astrogliosis, a phenomenon associated with neurodegeneration in MS. This may help restore gap-junctional communication of astrocytes with neurons and cells of the blood,brain barrier. Additional effects may result from (down-) modulation of S1P3 in astrocytes and of S1P1 and S1P5 in oligodendrocytes. In conclusion, FTY720 may act through immune-based and central mechanisms to reduce inflammation and support structural restoration of the central nervous system parenchyma. Beyond the autoimmune indications, very recent studies suggest that short-term, low-dose administration of FTY720 could help treat chronic (viral) infections. Differential effects of the drug on the trafficking of naïve, central memory and effector memory T cell subsets are discussed. [source] Synthesis and Biological Testing of N -Aminoimidazole-Based p38, MAP Kinase InhibitorsCHEMMEDCHEM, Issue 7 2010Claudia Bracht Abstract The p38 mitogen-activated protein (MAP) kinase,, plays a central role in the regulation of cellular responses such as differentiation, proliferation, apoptosis, and inflammation. Inhibition of p38 results in decreased synthesis of pro-inflammatory cytokines. To date, diverse p38, inhibitors are in phase,II clinical trials for numerous cytokine-dependent diseases. 2-Sulfanylimidazole derivatives offer advantages over the prototype inhibitor SB,203580, including fewer cytochrome P450 interactions and better kinetic properties. The aim of this study was to develop novel 1,2,4,5-tetrasubstituted pyridinylimidazoles with acyl residues at the imidazole N1 position that can interact with the kinase's hydrophobic region,II (HR,II) or sugar pocket (SP) to improve both selectivity and activity. The substitution pattern was optimized by variation of the acyl moiety at the N1 position of the N -aminoimidazole core. Acylation of the amino function was used for optimization and led to potent p38, MAPK inhibitors. [source] BAFF: a local and systemic target in autoimmune diseasesCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2009I. Moisini Summary BAFF (B lymphocyte activating factor of the tumour necrosis factor family) is a vital homeostatic cytokine for B cells that helps regulate both innate and adaptive immune responses. Increased serum levels of BAFF are found in a number of different autoimmune diseases, and BAFF is found in inflammatory sites in which there is lymphoid neogenesis. BAFF antagonism has been used in several autoimmune disease models, resulting in B cell depletion, decreased activation of T cells and dendritic cells (DC) and a reduction in the overall inflammatory burden. BAFF, through its interaction with BAFF-R, is required for survival of late transitional, marginal zone and mature naive B cells, all of which are depleted by BAFF blockade. Through their interactions with TACI (transmembrane activator and calcium modulator and cyclophilin ligand interactor) and BCMA (B cell maturation protein), BAFF and its homologue APRIL (a proliferation-inducing ligand), support the survival of at least some subsets of plasma cells; blockade of both cytokines results in a decrease in serum levels of immunoglobulin (Ig)G. In contrast, neither BAFF nor APRIL is required for the survival or reactivation of memory B cells or B1 cells. BAFF also helps DC maturation and interleukin (IL)-6 release and is required for proper formation of a follicular dendritic cell (FDC) network within germinal centres, although not for B cell affinity maturation. The clinical efficacy of BAFF blockade in animal models of autoimmunity may be caused both by the decline in the number of inflammatory cells and by the inhibition of DC maturation within target organs. Blockade of BAFF and its homologue APRIL are being explored for human use; several Phase I and II clinical trials of BAFF inhibitors for autoimmunity have been completed and Phase III trials are in progress. [source] Oligonucleotide N3,,P5, Phosphoramidates and Thio -Phoshoramidates as Potential Therapeutic AgentsCHEMISTRY & BIODIVERSITY, Issue 3 2010Sergei Abstract Nucleic acids analogues, i.e., oligonucleotide N3,,P5, phosphoramidates and N3,,P5, thio -phosphoramidates, containing 3,-amino-3,-deoxy nucleosides with various 2,-substituents were synthesized and extensively studied. These compounds resist nuclease hydrolysis and form stable duplexes with complementary native phosphodiester DNA and, particularly, RNA strands. An increase in duplexes' melting temperature, ,Tm, relative to their phosphodiester counterparts, reaches 2.2,4.0° per modified nucleoside. 2,-OH- (RNA-like), 2,- O -Me-, and 2,- ribo -F-nucleoside substitutions result in the highest degree of duplex stabilization. Moreover, under close to physiological salt and pH conditions, the 2,-deoxy- and 2,-fluoro-phosphoramidate compounds form extremely stable triple-stranded complexes with either single- or double-stranded phosphodiester DNA oligonucleotides. Melting temperature, Tm, of these triplexes exceeds Tm values for the isosequential phosphodiester counterparts by up to 35°. 2,-Deoxy-N3,,P5, phosphoramidates adopt RNA-like C3,- endo or N -type nucleoside sugar-ring conformations and hence can be used as stable RNA mimetics. Duplexes formed by 2,-deoxy phosphoramidates with complementary RNA strands are not substrates for RNase H-mediated cleavage in vitro. Oligonucleotide phosphoramidates and especially thio -phosphoramidates conjugated with lipid groups are cell-permeable and demonstrate high biological target specific activity in vitro. In vivo, these compounds show good bioavailability and efficient biodistribution to all major organs, while exerting acceptable toxicity at therapeutically relevant doses. Short oligonucleotide N3,,P5, thio -phosphoramidate conjugated to 5,-palmitoyl group, designated as GRN163L (Imetelstat), was recently introduced as a potent human telomerase inhibitor. GRN163L is not an antisense agent; it is a direct competitive inhibitor of human telomerase, which directly binds to the active site of the enzyme and thus inhibits its activity. This compound is currently in multiple Phase-I and Phase-I/II clinical trials as potential broad-spectrum anticancer agent. [source] | ||||||||||||||||||||||