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Biomedical subjects

C McGuigan

Publications and source records attributed to C McGuigan.

At least 19 recordsLinked to original sources
PubMed2000

A QSAR study investigating the effect of L-alanine ester variation on the anti-HIV activity of some phosphoramidate derivatives of d4T.

A QSAR study, involving the use of calculated physical properties (TSAR), and the use of a neural network approach (TSAR), has been performed concerning the anti-HIV activity and cytotoxic effects of a series of d4T phosphoramidate derivatives with varying L-alanine esters. Models were obtained which allow reliable predictions for the anti-HIV activity, and cytotoxicity, of these derivatives.

Alanine↗
PubMed2000

Synthesis and antiviral activity of acyclovir-5'-(phenyl methoxy alaninyl) phosphate as a possible membrane-soluble nucleotide prodrug.

We describe a synthesis of acyclovir-5'-(phenyl methoxy alaninyl) phosphate (2) from acyclovir (1). This compound was designed to act as a lipophilic, membrane-soluble prodrug of the free nucleotide. However, the biological activities of this derivative against a range of viruses indicated poor intracellular phosphate delivery, in marked contrast to the earlier successful delivery of several dideoxy anti-HIV nucleotides.

Acyclovir↗
PubMed2000

Enhancing the aqueous solubility of d4T-based phosphoramidate prodrugs.

A range of polyether para-substituted phosphoramidates were synthesised and found to have substantially elevated aqueous solubilities compared to the underivatised parent prodrug. A 30-fold increase in aqueous solubility could be achieved without a substantial decrease of in vitro activity against HIV-1. Replacement of the aryl (i.e. phenolic) moiety by tyrosine led to a substantial enhancement in aqueous solubility but also to a decrease in antiviral potency. A previously unobserved trend was identified, relating increased aryl substituent steric bulk to decreased antiviral activity.

Amides↗
PubMed2000

[Management of hemoptysis in children].

Hemoptysis in children are infrequent and often self-limiting. They are a manifestation of the broader spectrum of pulmonary haemorrhage. Diffuse pulmonary haemorrhages are often associated with diseases of other organs (cardiopathies, systemic diseases). Focal haemorrhages have multiple aetiologies, dominated by bronchopulmonary infections and cystic fibrosis. Fiberoptic bronchoscopy allows one to localise the bleeding, look for local causes and diagnose pulmonary hemosiderosis by BAL. For local lesions and if the medical management fails, bronchial arteriography is indicated to perform the embolisation of the bleeding vessels.

Age Factors↗
PubMed2000

Activities of masked 2',3'-dideoxynucleoside monophosphate derivatives against human immunodeficiency virus in resting macrophages.

The anti-human immunodeficiency virus (HIV) activity of aryloxyphosphoramidate protides of a number of anti-HIV nucleoside analogues was assessed in resting primary monocyte-macrophages (M/M). While 2',3'-dideoxythymidine (d4T), 2',3'-dideoxyadenosine (ddA), and 2',3'-dideoxy-2',3'-didehydroadenosine (d4A) protides showed an anti-HIV activity that was 25- to 625-fold greater than the parent nucleotides d4T, ddA, and d4A, respectively, other aryloxyphosphoramidate protides showed similar or even lower anti-HIV activities than their parent compounds. This variable anti-HIV effect is most likely related to the different dynamics of intracellular nucleoside monophosphate release from the protides. Our results indicate the potential advantage of therapeutic use of this approach for some nucleotide analogues to affect HIV replication in M/M, one of the major reservoirs of HIV in vivo.

Anti-HIV Agents↗
PubMed2000

Phosphoramidate derivatives of stavudine as inhibitors of HIV: unnatural amino acids may substitute for alanine.

Some novel phosphoramidate derivatives of the nucleoside analogue stavudine have been prepared as membrane-soluble prodrugs of the bioactive free phosphate forms. Phenyl phosphates linked via nitrogen to methyl esterified amino acid analogues were studied, where the amino acid was an unnatural alpha-alkyl (or aryl) glycine or an alpha,alpha-dialkyl glycine. All compounds were characterized by a range of spectroscopic, spectrometric and analytical methods and were subjected to in vitro evaluation of their anti-human immunodeficiency virus efficacy. It is notable that certain unnatural amino acid derivatives could substitute for alanine with only a relatively small loss of activity and, moreover, that this activity did not fall-off with increasing alkyl chain length for the C2-C4 mono-alkyl series. These data are further probed by the application of our recently reported 31P-NMR-based carboxyl esterase assay, with informative results.

Alanine↗
PubMed1999

Potent and selective inhibition of varicella-zoster virus (VZV) by nucleoside analogues with an unusual bicyclic base.

We herein report the discovery of an entirely new category of potent antiviral agents based on novel deoxynucleoside analogues with unusual bicyclic base moieties. Target structures, previously known as byproducts in Pd-catalyzed coupling of terminal alkynes with 5-iodo-nucleosides, are recognized herein for the first time to be potent and selective inhibitors of varicella-zoster virus (VZV) in vitro. As an unusual structure-activity relationship we noted the absolute requirement of a long alkyl side chain, with an optimum length of C(8)-C(10), for antiviral activity. We thus report the synthesis and characterization of a series of chain-modified analogues and their extensive in vitro evaluation. The lead compounds have a ca. 300-fold enhancement in anti-VZV activity over the reference compound acyclovir, with no detectable in vitro cytotoxicity. The novel structure of these compounds, coupled with their ease of synthesis, excellent antiviral profile, and promising physical properties, makes them of great interest for possible antiviral drug development.

Antiviral Agents↗
PubMed1999

Design and synthesis of lipophilic phosphoramidate d4T-MP prodrugs expressing high potency against HIV in cell culture: structural determinants for in vitro activity and QSAR.

A series of new substituted-aryl phosphoramidate derivatives of the anti-HIV drug d4T were synthesized as membrane-soluble nucleotide prodrugs, to extend and quantify the SAR observed for an earlier series of related derivatives. All of the compounds were found to be significantly more potent against HIV in cell culture than the nucleoside analogue d4T, and most were also found to be significantly more potent than the parent phosphoramidate. A Hansch type QSAR analysis was applied to the combined series of 21 compounds. The results of this analysis revealed anti-HIV activity to be principally dependent on lipophilicity in a quadratic manner, with terms representing substituent steric bulk and electronic effects having a minimal significance.

Amides↗
PubMed1999

Simple mono-derivatisation of the aryl moiety of D4A and DDA-based phosphoramidate prodrugs significantly enhances their anti-HIV potency in cell culture.

Simple mono-derivatisation of the aryl moiety of some phosphoramidate pronucleotide derivatives of d4A and ddA served to increase the lipophilicity of these membrane-soluble prodrugs. A concomitant and significant enhancement of potency against HIV-1 and HIV-2 in vitro was observed for the ddA- and d4A-based prodrugs compared to the original underivatised prodrugs.

Anti-HIV Agents↗
PubMed1999

The presence of substituents on the aryl moiety of the aryl phosphoramidate derivative of d4T enhances anti-HIV efficacy in cell culture: A structure-activity relationship.

New substituted-aryl phosphoramidate derivatives of the anti-HIV drug d4T were synthesized as membrane-soluble intracellular prodrugs for the free bioactive phosphate to establish relationship(s) between compound structure and in vitro antiviral activity. The majority of compounds demonstrated an elevation of in vitro potency relative to that of the parent nucleoside, and unlike d4T, all retained full activity in thymidine kinase-deficient cells. The compound bearing a p-chloro aryl group (8e) expressed nanomolar activity in vitro, a 14-fold increase in activity relative to that of the unsubstituted phosphoramidate (100-fold compared to d4T). An assay using pig liver esterase was used to establish the stability of the compounds to enzymatic degradation. While there was no apparent correlation between in vitro activity and half-life of enzymatic degradation, there was a close correlation between compound lipophilicity, determined by octanol/water partition coefficient, and in vitro potency. We suggest that substitutions made to the aryl moiety of the aryl phosphoramidate of d4T that result in enhancing lipophilicity may serve to increase the cellular uptake of the prodrug by passive diffusion, leading to the expression of antiviral potency at reduced prodrug concentrations.

3T3 Cells↗
PubMed1999

Formin defines a large family of morphoregulatory genes and functions in establishment of the polarising region.

Formin was originally isolated as the gene affected by the murine limb deformity (ld) mutations, which disrupt the epithelial-mesenchymal interactions regulating patterning of the vertebrate limb autopod. More recently, a rapidly growing number of genes with similarity to formin have been isolated from many different species including fungi and plants. Genetic and biochemical analysis shows that formin family members function in cellular processes regulating either cytokinesis and/or cell polarisation. Another common feature among formin family members is their requirement in morphogenetic processes such as budding and conjugation of yeast, establishment of Drosophila oocyte polarity and vertebrate limb pattern formation. Vertebrate formins are predominantly nuclear proteins which control polarising activity in limb buds through establishment of the SHH/FGF-4 feedback loop. Formin acts in the limb bud mesenchyme to induce apical ectodermal ridge (AER) differentiation and FGF-4 expression in the posterior AER compartment. Finally, disruption of the epithelial-mesenchymal interactions controlling induction of metanephric kidneys in ld mutant embryos indicates that formin might function more generally in transduction of morphogenetic signals during embryonic pattern formation.

Amino Acid Sequence↗
PubMed1999

Characterization of the activation pathway of phosphoramidate triester prodrugs of stavudine and zidovudine.

The phosphoramidate triester prodrugs of anti-human HIV 2', 3'-dideoxynucleoside analogs (ddN) represent a convenient approach to bypass the first phosphorylation to ddN 5'-monophosphate (ddNMP), resulting in an improved formation of ddN 5'-triphosphate and, hence, higher antiviral efficacy. Although phosphoramidate derivatization markedly increases the anti-HIV activity of 2',3'-didehydro-2', 3'-dideoxythymidine (d4T) in both wild-type and thymidine kinase-deficient CEM cells, the concept is far less successful for the 3'-azido-2',3'-dideoxythymidine (AZT) triesters. We now investigated the metabolism of triester prodrugs of d4T and AZT using pure enzymes or different biological media. The efficiency of the first activation step, mediated by carboxylesterases, consists of the formation of the amino acyl ddNMP metabolite. The efficiency of this step was shown to be dependent on the amino acid, alkyl ester, and ddN moiety. Triesters that showed no conversion to the amino acyl ddNMP accumulated as the phenyl-containing intermediate and had poor, if any, anti-HIV activity. In contrast to the relative stability of the triesters in human serum, carboxylesterase-mediated cleavage of the prodrugs was found to be remarkably high in mouse serum. The subsequent conversion of the amino acyl ddNMP metabolite to ddNMP or ddN was highest in rat liver cytosolic enzyme preparations. Although L-alaninyl-d4TMP was efficiently converted to d4TMP, the main metabolite formed from L-alaninyl-AZTMP was the free nucleoside (AZT), thus explaining why d4T prodrugs, but not AZT prodrugs, retain anti-HIV activity in HIV-infected thymidine kinase-deficient cell cultures. The rat liver phosphoramidase responsible for the formation of ddNMP was shown to be distinct from creatine kinase, alkaline phosphatase, and phosphodiesterase.

Amino Acids↗
PubMed1998

Lactate cannot substitute for alanine in d4T-based anti-HIV nucleotide prodrugs--despite efficient esterase-mediated hydrolysis.

As part of our on-going effort to deliver masked phosphates of antiviral nucleosides inside living cells we have previously discovered that amino acid-derived phosphoramidates are particularly effective. Here we report that lactate analogues, with a simple change of bridging nitrogen for oxygen, are virtually inactive as antiviral agents and apparently do not achieve intracellular nucleoside phosphate delivery.

Alanine↗
PubMed1998

Marked inhibitory activity of masked aryloxy aminoacyl phosphoramidate derivatives of dideoxynucleoside analogues against visna virus infection.

Lipophilic masked aryloxyaminoacylphosphoramidate derivatives of 2',3'-dideoxynucleoside (ddN) analogues with potent anti-HIV activity (i.e., stavudine [d4T], azidothymidine [AZT], dideoxycytidine [ddC], 3'thio-2',3'-dideoxy cytidine [3TC], dideoxyadenosine [ddA], and 2',3'-didehydro-2',3'-dideoxyadenosine [d4A]) activity were evaluated for their activity against visna virus (VV) in sheep choroid plexus (SCP) cells. The activity of several prodrug derivatives against VV proved markedly superior to that of the corresponding free ddN analogues. In particular, the d4A and ddA prodrug derivatives were exquisitely inhibitory in this model system (50% effective concentration [EC50], < or = 0.003 microM), and their anti-VV potency exceeded by at least 200-fold the antiviral potency of the corresponding free nucleosides. Marked differences were noted in the anti-VV potencies of several of the test compounds depending on the nature of the amino acid linked to the 5'-phosphate moiety, the nature of the nucleoside, or both. In view of the stability of the prodrugs in lamb serum, the VV infection model in lambs may be considered highly useful for investigating the in vivo antiretroviral efficacy of these type of drugs, particularly the d4T, ddA, and d4A prodrug derivatives.

Animals↗
PubMed1998

Metabolism and anti-HIV activity of phosphoramidate derivatives of D4T-MP with variations in the amino acid moiety.

The metabolism of different phosphoramidate prodrugs of d4T-MP, in which the phosphate group is linked to a phenyl group and the alkyl ester of an amino acid was studied in crude CEM cell extracts. Significant (80-100%) conversion to the amino acyl d4T-MP metabolite was obtained with derivatives containing L-alanine or methyl-L-aspartic acid. A lower degree of conversion was seen with derivatives containing L-phenylalanine, L-methionine, methyl-L-glutamic acid or L-leucine. Derivatives containing D-alanine, beta-alanine, glycine, L-valine or L-lactate showed no conversion to the amino acyl d4T-MP metabolite. Overall, there was a close correlation between the anti-HIV activity of these prodrugs and their conversion rate to the amino acyl d4T-MP metabolite. Our data suggest that the enzymes involved in the formation of the amino acyl d4T-MP metabolite have a rather stringent specificity for L-alanine as the amino acid moiety. In addition, these enzymes were found to be markedly species-dependent, their activities being highest in mouse serum, followed by guinea pig serum, but only minimal in human serum. Mouse serum therefore appears to be the medium of choice to isolate and identify the enzymes that are involved in the metabolism of these phosphoramidate prodrugs.

Amino Acids↗
PubMed1998

Synthesis and anti-HIV activity of some novel chain-extended phosphoramidate derivatives of d4T (stavudine): esterase hydrolysis as a rapid predictive test for antiviral potency.

Novel chain-extended nucleoside phosphoramidates of the anti-human immunodeficiency virus (HIV) drug d4T (stavudine) have been prepared as possible membrane-permeable prodrugs of the bio-active free 5'-monophosphates. Phosphorochloridate chemistry gave the target compounds in moderate to high yields, and all materials were fully characterized by spectroscopic and analytical methods. The compounds are related to the previously reported phenyl methoxyalaninyl derivative of d4T, which was shown to be a potent and selective inhibitor of HIV. In this study the amino acid nitrogen and ester moieties were separated by methylene spacers of between two and six carbon atoms. In vitro evaluation of these compounds indicated an almost complete lack of anti-HIV activity, the compounds being several orders of magnitude less potent than the corresponding alpha-amino acid derivatives. The reasons for the virtual lack of anti-HIV activity appear to involve poor enzyme-mediated hydrolysis.

Animals↗
PubMed1998

Synthesis and evaluation of some masked phosphate esters of the anti-herpesvirus drug 882C (netivudine) as potential antiviral agents.

A number of symmetric and asymmetric 5'-phosphate esters of the potent anti-varicella-zoster virus (VZV) agent 1-(beta-D-arabinofuranosyl)-5-prop-1-ynyluracil (882C; netivudine) were prepared as potential lipophilic, membrane-soluble prodrugs of the bio-active phosphate forms. The compounds were prepared by the base-catalysed coupling of various phosphorochloridates with the free nucleoside analogue. Compounds were fully characterized by a range of spectroscopic and analytical methods and were studied for their inhibition of several viruses in tissue culture. All of the phosphate esters were inactive against human cytomegalovirus, herpes simplex virus type 2, VZV, human immunodeficiency virus type 1 and influenza A virus (EC50 > 100 microM) except the 5'-(4-nitrophenyl phenyl) phosphate, which inhibited influenza A virus. The relative rate of esterase-mediated hydrolysis of one of the lead target structures was measured in order to rationalize the poor antiviral action, and data were collected on possible metabolites in support of this analysis. Cell-specific esterases are implicated as key determinants of the antiviral potency of prodrugs of this type.

Animals↗