Biomedical subjects

J Balzarini

Publications and source records attributed to J Balzarini.

At least 127 records · Page 7Linked to original sources

PubMed2000

Mutational analysis of trp-229 of human immunodeficiency virus type 1 reverse transcriptase (RT) identifies this amino acid residue as a prime target for the rational design of new non-nucleoside RT inhibitors.

Trp-229 is part of the non-nucleoside reverse transcriptase inhibitor (NNRTI)-binding pocket of HIV type 1 (HIV-1) reverse transcriptase (RT), and is also part of the "primer grip" of HIV-1 RT. Using site-directed mutagenesis, seven RT mutants were constructed bearing the mutations 229Phe, 229Tyr, 229Ile, 229His, 229Lys, 229Cys, and 229Gln. We found that all of the mutants showed severely compromised RNA- and DNA-dependent DNA polymerase activities (<2% of wild-type activity). The recombinant 229Phe and 229Tyr RT enzymes were among the mutant enzymes with the highest activity (0.7 and 1.1% of wild-type activity, respectively) and we evaluated these for resistance against several NNRTIs. No resistance was found for the 229Phe RT, but the 229Tyr RT showed a approximately 20-fold resistance against UC-781 and lower resistance against emivirine and nevirapine. Attempts to make recombinant virus strains bearing the single 229Phe or 229Tyr RT mutation failed. Experiments in which we varied the pentenyl ether substituent of the thiocarboxanilide UC-781 revealed that Trp-229 can be specifically targeted by NNRTIs and that an alkenyloxy group length of five atoms assures an optimal interaction of the thiocarboxanilides with Trp-229. Our findings indicate that Trp-229, when combined with other crucial immutable amino acids (i.e., Tyr-318), is an appropriate candidate for the targeted design of new NNRTIs.

Anilides↗

PubMed1999

Potential multifunctional inhibitors of HIV-1 reverse transcriptase. Novel [AZT]-[TSAO-T] and [d4T]-[TSAO-T] heterodimers modified in the linker and in the dideoxynucleoside region.

In an attempt to combine the anti-HIV-inhibitory capacity of nucleoside reverse transcriptase (RT) inhibitors (NRTI) and non-nucleoside RT inhibitors (NNRTI), several heterodimer analogues of the previously reported [AZT]-(CH(2))(3)-[TSAO-T] prototype have been prepared. In these novel series, other NRTIs, an expanded range of linkers with different conformational freedom and other attachment sites for these linkers on the base part of the NRTI analogue have been explored. Moreover, in order to circumvent the dependence of the NRTI moiety of the heterodimer on activation by cellular nucleoside kinases, novel heterodimers in which the NRTI is bearing a masked monophosphate group at the 5'-position are described. Among the novel heterodimers, several derivatives show a potent anti-HIV-1 activity, which proved comparable, or even superior, to that of the AZT heterodimer prototype. The nature of the NRTI was important for the eventual anti-HIV-1 activity. In particular, the d4T heterodimer derivative containing a propyl linker between the N-3 positions of the base of TSAO-T and d4T was approximately 5- to 10-fold more inhibitory to HIV-1 than the corresponding AZT heterodimer prototype.

Anti-HIV Agents↗

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

Characterization of multiple nuclear localization signals in herpes simplex virus type 1 thymidine kinase.

We have reported previously that the herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) fused with green fluorescent protein (GFP) is localized in the nucleus of HSV-1 TK-GFP gene-transfected cells (Degrève et al. (1998) J. Virol. 72, 9535-9543). Deletion of the N-terminal 34 amino acids or selective mutation of the nonapeptide (25)RRTALRPRR(33), located in the N-terminal region of HSV-1 TK, resulted in the loss of the specific nuclear localization of HSV-1 TK. Utilizing information on the crystallographic structure of HSV-1 TK, we have now identified three additional putative nuclear localization signals and evaluated their potential role in the nuclear trafficking of HSV-1 TK by site-directed mutagenesis. We found that the sites containing the amino acids R236-R237 and K317-R318 are absolutely required for specific nuclear targeting of HSV-1 TK. The K317-R318 region, located at the interface between the two monomers in the dimeric HSV-1 TK structure, could act as a nuclear localization signal for monomeric HSV-1 TK. Alternatively, crystallographic data indicate that R318 might be essential for the formation of the TK dimer, and therefore it is required if HSV-1 TK is transported as a dimer.

Amino Acid Sequence↗

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

5'-Phosphoramidates and 5'-diphosphates of 2'-O-allyl-beta-D-arabinofuranosyluracil, -cytosine, and -adenine: inhibition of ribonucleotide reductase.

Continuing our studies on ribonucleotide reductase (RNR) mechanism-based inhibitors, we have now prepared the diphosphates (DP) of 2'-O-allyl-1-beta-D-arabinofuranosyl-uracil and -cytosine and 2'-O-allyl-9-beta-D-arabinofuranosyl-adenine and evaluated their inhibitory activity against recombinant murine RNR. 2'-O-Allyl-araUDP proved to be inhibitory to RNR at an IC(50) of 100 microM, whereas 2'-O-allyl-araCDP was only marginally active (IC(50) 1 mM) and 2'-O-allyl-araADP was completely inactive. The susceptibility of the parent nucleosides to phosphorylation by thymidine kinase and 2'-deoxycytidine kinase was also investigated, and all nucleosides proved to be poor substrates for the above-cited kinases. Moreover, prodrugs of 2'-O-allyl-araU and -araC monophosphates, namely 2'-O-allyl-5'-(phenylethoxy-L-alanyl phosphate)-araU and -araC, were prepared and tested against tumor cell proliferation but proved to be inactive. A molecular modeling study has been conducted in order to explain our results. The data confirm that for both the natural and analogue nucleoside diphosphates, the principal determinant interaction with the active site of RNR is with the diphosphate group, which forms strong hydrogen bonds with Glu623, Thr624, Ser625, and Thr209. Our findings indicate that the poor phosphorylation may represent an explanation for the lack of marked in vitro cytostatic activity of the test compounds.

Animals↗

PubMed1999

Cloning and characterization of the multisubstrate deoxyribonucleoside kinase of Drosophila melanogaster.

A Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) was reported to phosphorylate all four natural deoxyribonucleosides as well as several nucleoside analogs (Munch-Petersen, B., Piskur, J., and Sondergaard, L. (1998) J. Biol. Chem. 273, 3926-3931). The broad substrate specificity of this enzyme together with a high catalytic rate makes it unique among the nucleoside kinases. We have in the present study cloned the Dm-dNK cDNA, expressed the 29-kDa protein in Escherichia coli, and characterized the recombinant enzyme for the phosphorylation of nucleosides and clinically important nucleoside analogs. The recombinant enzyme preferentially phosphorylated the pyrimidine nucleosides dThd, dCyd, and dUrd, but phosphorylation of the purine nucleosides dAdo and dGuo was also efficiently catalyzed. Dm-dNK is closely related to human and herpes simplex virus deoxyribonucleoside kinases. The highest level of sequence similarity was noted with human mitochondrial thymidine kinase 2, and these enzymes also share many substrates. The cDNA cloning and characterization of Dm-dNK will be the basis for studies on the use of this multisubstrate nucleoside kinase as a suicide gene in combined gene/chemotherapy of cancer.

Amino Acid Sequence↗

PubMed1999

Role of antimetabolites of purine and pyrimidine nucleotide metabolism in tumor cell differentiation.

Transformed cells are characterized by imbalances in metabolic routes. In particular, different key enzymes of nucleotide metabolism and DNA biosynthesis, such as CTP synthetase, thymidylate synthase, dihydrofolate reductase, IMP dehydrogenase, ribonucleotide reductase, DNA polymerase, and DNA methyltransferase, are markedly up-regulated in certain tumor cells. Together with the concomitant down-modulation of the purine and pyrimidine degradation enzymes, the increased anabolic propensity supports the excessive proliferation of transformed cells. However, many types of cancer cells have maintained the ability to differentiate terminally into mature, non-proliferating cells not only in response to physiological receptor ligands, such as retinoic acid, vitamin D metabolites, and cytokines, but also following exposure to a wide variety of non-physiological agents such as antimetabolites. Interestingly, induction of tumor cell differentiation is often associated with reversal of the transformation-related enzyme deregulations. An important class of differentiating compounds comprises the antimetabolites of purine and pyrimidine nucleotide metabolism and nucleic acid synthesis, the majority being structural analogs of natural nucleosides. The CTP synthetase inhibitors cyclopentenylcytosine and 3-deazauridine, the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine, the dihydrofolate reductase inhibitor methotrexate, the IMP dehydrogenase inhibitors tiazofurin, ribavirin, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR) and mycophenolic acid, the ribonucleotide reductase inhibitors hydroxyurea and deferoxamine, and the DNA polymerase inhibitors ara-C, 9-(2-phosphonylmethoxyethyl)adenine (PMEA), and aphidicolin, as well as several nucleoside analogs perturbing the DNA methylation pattern, have been found to induce tumor cell differentiation through impairment of DNA synthesis and/or function. Thus, by selectively targeting those anabolic enzymes that contribute to the neoplastic behavior of cancer cells, the normal cellular differentiation program may be reactivated and the malignant phenotype suppressed.

Animals↗

PubMed1999

N6-cyclopropyl-PMEDAP: a novel derivative of 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP) with distinct metabolic, antiproliferative, and differentiation-inducing properties.

N6-Cyclopropyl-PMEDAP (cPr-PMEDAP) is a novel derivative of the acyclic nucleoside phosphonate 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP). Its cytostatic activity was found to be 8- to 20-fold more pronounced than that of PMEDAP and equivalent to that of the guanine derivative 9-(2-phosphonylmethoxyethyl)guanine (PMEG) against a variety of tumor cell lines. Unlike PMEDAP, but like PMEG, cPr-PMEDAP was equally cytostatic to wild-type and 9-(2-phosphonylmethoxyethyl)adenine/PMEDAP-resistant variants of the human erythroleukemia K562 and the murine leukemia L1210 cell lines. Also, cPr-PMEDAP and PMEG proved to be equipotent inducers of K562 and rat choriocarcinoma RCHO cell differentiation, whereas the differentiation-inducing activity of PMEDAP was 5- to 25-fold less pronounced. Furthermore, compared to PMEDAP, cPr-PMEDAP and PMEG were 10- to 25-fold more potent in inhibiting the progression of K562 cells through the S phase of the cell cycle, resulting in a marked accumulation of the four 2'-deoxyribonucleoside 5'-triphosphate pools. The biological effects of cPr-PMEDAP, but not PMEDAP, were reversed by the adenylate deaminase inhibitor 2'-deoxycoformycin (dCF). Formation of the deaminated derivative of cPr-PMEDAP (i.e. PMEG) was demonstrated in crude extracts from K562 and L1210 cells and in metabolism studies with radiolabeled cPr-PMEDAP and PMEG. This is the very first example of an acyclic nucleoside phosphonate analogue that is susceptible to deamination. However, cPr-PMEDAP was not recognized as a substrate by purified adenosine deaminase or by adenylate deaminase. These findings might point to an as yet unidentified cellular enzyme, sensitive to dCF but different from the common adenosine and AMP deaminases. Our data demonstrate the superior antiproliferative and differentiation-inducing effects of cPr-PMEDAP on tumor cells, as compared to the parent compound PMEDAP, based on the unique metabolic properties of this novel compound.

AMP Deaminase↗

PubMed1999

Suppression of resistance to drugs targeted to human immunodeficiency virus reverse transcriptase by combination therapy.

There are currently thirteen drugs approved for the treatment of human immunodeficiency virus (HIV)-infected individuals. Seven of them are targeted against the virus-encoded reverse transcriptase (RT). Appearance of drug-resistant virus strains under the selective pressure of anti-HIV chemotherapy rapidly occurs as a consequence of the low fidelity of the RT-catalyzed DNA polymerisation reaction and the massive viral turnover. Resistance-associated mutations appear in the RT of virus strains that are under selective pressure of both nucleoside RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs). A variety of these mutations cause cross-resistance to several other NRTIs or NNRTIs and consequently may hamper the effectiveness of the other drugs. Other RT mutations are quite specific and selective in their drug-resistance spectrum and do not influence the potency of the majority of other available drugs. Moreover, drug-specific mutations are identified that are able to restore drug sensitivity again when concomitantly present with other drug-specific mutations. Combination therapy has proven to be able to markedly suppress virus replication (and subsequent appearance of drug resistance) for a relatively long time period. However, in a number of cases, multiple drug combination therapy results in the appearance of a different mutation spectrum than is expected to emerge under monotherapy. Also, it has been shown that drugs that alter cellular deoxynucleotide pools not only are able to potentiate the antiviral efficacy of some RT inhibitors, but also may influence the resistance spectrum of certain anti-HIV drugs. All available information argues for the use of a rational combination of different anti-HIV inhibitors with different resistance spectra to suppress virus replication efficiently and to delay the emergence of drug-resistant virus as long as possible, but it also indicates that there is a strong need for additional drugs to further optimize and improve the efficacy of long-term HIV treatment.

Anti-HIV Agents↗

PubMed1999

Structure-antiviral activity relationship in the series of pyrimidine and purine N-[2-(2-phosphonomethoxy)ethyl] nucleotide analogues. 1. Derivatives substituted at the carbon atoms of the base.

A series of dialkyl esters of purine and pyrimidine N-[2-(phosphonomethoxy)ethyl] derivatives substituted at position 2, 6, or 8 of the purine base or position 2, 4, or 5 of the pyrimidine base were prepared by alkylation of the appropriate heterocyclic base with 2-chloroethoxymethylphosphonate diester in the presence of sodium hydride, cesium carbonate, or 1,8-diazabicyclo[5,4, 0]undec-7-ene (DBU) in dimethylformamide. Additional derivatives were obtained by the transformations of the bases in the suitably modified intermediates bearing reactive functions at the base moiety. The diesters were converted to the corresponding monoesters by sodium azide treatment, while the free acids were obtained from the diester by successive treatment with bromotrimethylsilane and hydrolysis. None of the PME derivatives in the pyrimidine series, their 6-aza or 3-deaza analogues, exhibited any activity against DNA viruses or retroviruses tested, except for the 5-bromocytosine derivative. Substitution of the adenine ring in PMEA at position 2 by Cl, F, or OH group decreased the activity against all DNA viruses tested. PMEDAP was highly active against HSV-1, HSV-2, and VZV in the concentration range (EC50) of 0.07-2 microg/mL. Also the 2-amino-6-chloropurine derivative was strongly active (EC50 = 0.1-0. 4 microg/mL) against herpes simplex viruses and (EC50 = 0.006-0.3 microg/mL) against CMV and VZV. PMEG was the most active compound of the whole series against DNA viruses (EC50 approximately 0.01-0.02 microg/mL), though it exhibited significant toxicity against the host cells. The base-modified compounds did not show any appreciable activity against DNA viruses except for 7-deazaPMEA (IC50 approximately 7.5 microg/mL) against HIV-1 and MSV. The neutral (diisopropyl, diisooctyl) diesters of PMEA were active against CMV and VZV, while the corresponding monoesters were inactive. The diisopropyl ester of the 2-chloroadenine analogue of PMEA showed substantially (10-100x) higher activity against CMV and VZV than the parent phosphonate. Also, the diisopropyl and diisooctyl ester of PMEDAP inhibited CMV and VZV, but esterification of the phosphonate residue did not improve the activity against either MSV or HIV.

Animals↗

PubMed1999

Antitumor activity of P-4055 (elaidic acid-cytarabine) compared to cytarabine in metastatic and s.c. human tumor xenograft models.

The antineoplastic efficacy of P-4055, a 5'-elaidic acid (C18:1, unsaturated fatty acid) ester of cytarabine, a nucleoside antimetabolite frequently used in the treatment of hematological malignancies, was examined in several in vivo models for human cancer. In initial dose-finding studies in nude mice, the efficacy of P-4055 was highest when using schedules with repeated daily doses. In a Raji Burkitt's lymphoma leptomeningeal carcinomatosis model in nude rats, the control cytarabine- and saline-treated animals (five in each group) had a mean survival time of 13.2 days, whereas treatment with P-4055 resulted in three of five long-time survivors (>70 days). In a systemic Raji leukemia model in nude mice, 8 of 10 of the P-4055-treated animals survived (>80 days), compared with none of the cytarabine-treated animals (mean survival time, 34.2 days). In s.c. xenograft models, the effects of maximum tolerated doses of P-4055 and cytarabine, given in four weekly cycles of daily bolus i.v. injections for 5 subsequent days, against seven tumors (three melanomas, one lung adenocarcinoma, one breast cancer, and two osteogenic sarcomas) were investigated. P-4055 induced partial or complete tumor regression of the lung carcinoma, as well as of all three malignant melanomas. In two of the melanomas the activity was highly superior to that of cytarabine, and both P-4055 and cytarabine were, in general, more effective than several clinically established drugs previously tested in the same tumor models. In in vitro studies, inhibitors of nucleoside carrier-dependent transport, nitrobenzylmercaptopurine riboside and dipyridamol, reduced strongly the cellular sensitivity to cytarabine, but not to P-4055, indicating that P-4055 uses an alternative/additional mechanism of internalization into the cell compared with cytarabine. The results explain, at least in part, the observed differences between the two compounds in in vivo efficacy, and together the data strongly support the evaluation of P-4055 in clinical studies.

Animals↗

PubMed1999

cycloSal-Pronucleotides of 2',3'-dideoxyadenosine and 2', 3'-dideoxy-2',3'-didehydroadenosine: synthesis and antiviral evaluation of a highly efficient nucleotide delivery system.

The synthesis, hydrolysis, and antiviral evaluation of novel, lipophilic cycloSal-ddAMP (9a-d) and cycloSal-d4AMP (10a-d) derivatives of the antiviral purine dideoxynucleoside analogues 2', 3'-dideoxyadenosine (ddA) (2) and 2',3'-dideoxy-2', 3'-didehydroadenosine (d4A) (3) are reported. These potential pronucleotides release ddAMP (7) or d4AMP (8) selectively by a controlled, chemically induced tandem reaction. All new compounds 9 and 10a-d were synthesized in good yields using our previously reported phosphorus(III) method starting from substituted salicyl alcohols 14a-h. The phosphotriesters 9 and 10 were obtained with a stereochemical preference of 2:1 with respect to the configuration at the phosphorus center. In an 1-octanol/water mixture phosphotriesters 9 and 10 exhibited 7-43-fold higher lipophilicity than the parent nucleosides ddA (2) and d4A (3) as judged by their log P values. In hydrolysis studies, 9 and 10 decomposed under mild aqueous basic conditions releasing solely ddAMP (7) and d4AMP (8), as well as the diols 14. Further hydrolysis studies under acidic conditions showed a marked increase in stability with respect to the acid-catalyzed cleavage of the glycosyl bond. Phosphotriesters 9 and 10 exhibited antiviral potencies against wild-type HIV-1 and HIV-2 strains in human T-lymphocyte (CEM/O) cells that were, respectively, 100- and 600-fold higher than those of ddA (2) and d4A (3). Furthermore, all triesters 9 and 10 were markedly more active than the corresponding ddI compounds 11 and 12, which supports the concept of the delivery of the adenine nucleotides. Studies with adenosine deaminase (ADA) and adenosine monophosphate deaminase (AMPDA) showed that the triesters were not substrates for enzymatic deamination. The studies reported herein demonstrate conclusively that the cycloSal triesters deliver exclusively the nucleotides ddAMP and d4AMP, not only under chemical-simulated hydrolysis but also under intracellular conditions fulfilling the adenosine deaminase bypass premise.

3T3 Cells↗

PubMed1999

cycloSal-Pronucleotides of 2'-fluoro-ara- and 2'-fluoro-ribo-2',3'- dideoxyadenosine as a strategy to bypass a metabolic blockade.

Novel, lipophilic cycloSal triesters 4a-c and 5a-c were synthesized, respectively, from the ara- and ribo-configurated 2'-fluorinated-2', 3'-dideoxyadenosines 2 and 3. The cycloSal phosphotriesters were used as tools to study the effects of the two different sugar pucker conformations induced by two opposite configurations of the fluorine substituent at C2' of the dideoxyribose moiety. F-ara-ddA (2) is known to be an active anti-HIV agent, whereas the ribo-analogue 3 is inactive. Hydrolysis studies with the triester precursors 4a-c and 5a-c showed selective formation of the monophosphates of 2 and 3. The lipophilicity of the triester prodrugs was considerably increased by the cycloSal mask with respect to ddA (1), F-ara-ddA (2), and F-ribo-ddA (3). Phosphotriesters 4 and 5 proved to be completely resistant to ADA and AMPDA deamination. In parallel experiments, ribo-nucleoside 3 showed a 50-fold faster deamination rate relative to the ara-analogue 2. Against HIV in CEM cells, the phosphotriesters 4 proved to be 10-fold more potent than the parent nucleoside 2. Furthermore, the prodrugs 4 were active against MSV-induced transformation of C3H/3T3 fibroblasts, while 2 was inactive. More interestingly, the ribo-configurated phosphotriesters 5, prepared from the inactive F-ribo-ddA (3), showed a level of anti-HIV activity that was even higher than that of F-ara-ddA (2). Our findings clearly prove that the application of the cycloSal-pronucleotide concept to F-ribo-ddA (3) overcomes a metabolic blockade in the formation of the corresponding monophosphate.

3T3 Cells↗

PubMed1999

Conformational and quantitative structure-activity relationship study of cytotoxic 2-arylidenebenzocycloalkanones.

Various 2-arylideneindanones 1, 2-arylidenetetralones 2, and 2-arylidenebenzosuberones 3 were synthesized with the aim of determining the relative orientations of the two aryl rings which favored cytotoxicity. Molecular modeling of the unsubstituted compound in each series revealed differences in the spatial arrangements of the two aryl rings, and evaluation of these compounds against P388, L1210, Molt 4/C8, and CEM cells as well as a panel of human tumor cell lines indicated that in general the order of cytotoxicity was 3 > 2 > 1. In particular 2-(4-methoxyphenylmethylene)-1-benzosuberone (3k) had the greatest cytotoxicity, possessing 11 times the potency of the reference drug melphalan when all five screens were considered. Series 3 was considered in further detail. First, excision of the aryl ring fused to the cycloheptanone moiety in series 3 led to some 2-arylidene-1-cycloheptanones 4 which had approximately one-third of the bioactivity of the analogues 3. Second, in some screens cytotoxicity was correlated negatively with the sigma values and positively with the MR constants of the substituents in the arylidene aryl ring of 3. Third, X-ray crystallography of five representative compounds (3i,k-n) revealed differences in the locations of the aryl rings which may have contributed to the variations in cytotoxicity. Finally three members of series 3 inhibited RNA and protein syntheses and induced apoptosis in human Jurkat T cells. This study has revealed that 2-arylidene-1-benzosuberones are a group of useful cytotoxic agents, and in particular 3k serves as a prototypic molecule for subsequent structural modifications.

Animals↗

PubMed1999

Novel potential agents for human cytomegalovirus infection: synthesis and antiviral activity evaluation of benzothiadiazine dioxide acyclonucleosides.

The first acyclonucleosides based on the benzothiadiazine dioxide system were synthesized following the silylation procedure. Several acyclic moieties, including acetoxyethoxymethyl, benzyloxymethyl, and propargyloxymethyl groups, were introduced. Two synthetic strategies were designed to selectively obtain the N-1 or N-3 derivatives. Lipase-mediated deacylation was used for the deprotection of the acyclonucleosides. Some of the benzothiadiazine dioxide acyclonucleosides, in particular 16, proved active against human cytomegalovirus (CMV) at concentrations slightly higher than that found for ganciclovir [50% inhibitory concentration (IC50) = 3. 5-3.7 micrograms/mL, cytotoxicity (CC50) >/= 40 micrograms/mL, MCC = 20 micrograms/mL]. Additionally, compound 16 inhibited the replication of human immunodeficiency virus type 1 (HIV-1) and HIV-2 in CEM cells at concentrations that were 5-fold lower than its cytotoxic concentration.

Anti-HIV Agents↗

PubMed1999

Impact of 9-(2-phosphonylmethoxyethyl)adenine on (deoxy)ribonucleotide metabolism and nucleic acid synthesis in tumor cells.

Following exposure to 9-(2-phosphonylmethoxyethyl)adenine (an inhibitor of the cellular DNA polymerases alpha, delta and epsilon), human erythroleukemia K562, human T-lymphoid CEM and murine leukemia L1210 cells markedly accumulated in the S phase of the cell cycle. In contrast to DNA replication, RNA synthesis (transcription) and protein synthesis (mRNA translation) were not affected by 9-(2-phosphonylmethoxyethyl)-adenine. The ribonucleoside triphosphate pools were slightly elevated, while the intracellular levels of all four deoxyribonucleoside triphosphates were 1.5-4-fold increased in 9-(2-phosphonylmethoxyethyl)adenine-treated K562, CEM and L1210 cells. The effect of 9-(2-phosphonylmethoxyethyl)adenine on de novo (thymidylate synthase-mediated) and salvage (thymidine kinase-mediated) dTTP synthesis was investigated using radio-labelled nucleoside precursors. The amount of thymidylate synthase-derived dTTP in the acid soluble pool was 2-4-fold higher in PMEA-treated than in untreated K562 cells, which is in accord with the 3-4-fold expansion of the global dTTP level in the presence of 9-(2-phosphonylmethoxyethyl)adenine. Strikingly, 2-derived dTTP accumulated to a much higher extent (i.e. 16-40-fold) in the soluble dTTP pool upon 9-(2-phosphonylmethoxyethyl)adenine treatment. In keeping with this finding, a markedly increased thymidine kinase activity could be demonstrated in extracts of 9-(2-phosphonylmethoxyethyl)adenine-treated K562 cell cultures. Also, in the presence of 200 microM 9-(2-phosphonylmethoxyethyl)adenine, 14-fold less thymidylate synthase-derived but only 3-fold less thymidine kinase-derived dTTP was incorporated into the DNA of the K562 cells. These data show that thymidine incorporation may be inappropriate as a cell proliferation marker in the presence of DNA synthesis inhibitors such as 9-(2-phosphonylmethoxyethyl)adenine. Our findings indicate that 9-(2-phosphonylmethoxyethyl)adenine causes a peculiar pattern of (deoxy)ribonucleotide metabolism deregulation in drug-treated tumor cells, as a result of the metabolic block imposed by the drug on the S phase of the cell cycle.

Adenine↗