Targeting of antiviral drugs to T4-lymphocytes: anti-HIV activity of neoglycoprotein-AZTMP conjugates in vitro

The delivery of the anti-HIV agent 3′-azido-3′-deoxythymidine (AZT), in its 5′-monophosphate form, (in)to human T-lymphocyte MT-4 cells in vitro through covalent coupling to neoglycoproteins was investigated. In vivo application of this drug targeting concept may lead to increased efficacy and/or diminished side effects caused by AZT during the treatment of AIDS and ARC patients. The rationale for the design of the neoglycoprotein carriers is based on the existence of sugar recognizing lectins on T-lymphocytes. Using a phenyl-linkage between sugar and Human Serum Albumin (HSA), various mannose-, fucose-, galactose- and glucose-containing neoglycoproteins were synthesized. The intrinsic anti-HIV activity of these neoglycoproteins was tested in vitro in HIV-1 infected MT-4 cells. Only the derivative having 40 moles mannose per mole protein (Man₄₀HSA) shows pronounced anti-HIV-1 activity itself. This effect may be caused by interference of the Man₄₀HSA with the gp120-CD4 mediated virus/MT-4 cell interaction. After conjugation with AZTMP, the mannose- as well as the fucose- and galactose-containing conjugates exhibited a pronounced activity. Conjugates of glucose-HSA and HSA displayed much less activity in spite of the fact that drug loading was considerably higher, compared with the galactose, mannose and fucose derivatives. In the series of mannose-neoglycoproteins, the Man₂₂HSA-AZTMP conjugate was shown to be more than 30 times as active against HIV-1 compared to HSA-AZTMP. Selectivity indices of Man₇- and Man₂₂HSA-AZTMP were exceeding the AZT and AZTMP indices, indicating that these conjugates possess a more selective action. Stability experiments indicate that the potent action of the galactose-, mannose- and fucose-HSA-AZTMP conjugates is not due to a complete extracellular hydrolysis of the covalent drug-protein bond. Since Man₂₂HSA has no intrinsic activity in the concentration range used, the antiviral effect is unlikely to be explained by synergism of extracellular released AZTMP/AZT and the carrier. Possibly, delivery of AZTMP through recognition of the neoglycoprotein by a component of the cell membrane and subsequent internalization and release of the drug from the conjugate may play a role.     

Neoglycoproteins as carriers for antiviral drugs: synthesis and analysis of protein-drug conjugates

In order to investigate whether neoglycoproteins can potentially act as carriers for targeting of antiviral drugs to certain cell types in the body, various neoglycoproteins were synthesized using thiophosgene-activated p-aminophenyl sugar derivatives. These neoglycoproteins were conjugated with the 5'-monophosphate form of the antiviral drug AZT. For a proper characterization of these preparations, both protein and drug content have to be determined. Comparison of the Lowry and the Bio-Rad protein assays revealed that for both the neoglycoprotein carriers themselves and the AZTMP conjugates, the Lowry assay yielded the most reliable and reproducible results. It was demonstrated that both the reagent used for drug conjugation (ECDI) as well as the introduction of phenyl-sugar groups in the protein interfered with the analysis of bound nucleotide as based on spectral differences between protein and protein-drug conjugate. Therefore, we developed a rapid HPLC system for determination of the drug-protein coupling ratio through acid hydrolysis of the covalently bound nucleotide. With the ECDI-mediated conjugation of 5'-monophosphate drug derivatives to neoglycoproteins, products with molar ratios of drug to protein ranging from 1.2 to 5.6 were obtained. The drug-neoglycoprotein conjugates appeared to be fairly stable during storage, in lyophilized form, at -20 degrees C. The anti-HIV-1 activity of the neoglycoprotein-drug conjugates, as determined in vitro in MT-4 cells, was shown to be dependent on glycosylation of the albumin and also on the kind of sugar present in the neoglycoprotein. The anti-HIV-1 activity of the AZTMP-mannose-albumin conjugate exceeded that of the parent drug by more than 4 times.     

Synthesis of new covalently bound kappa-carrageenan-AZT conjugates with improved anti-HIV activities

This paper describes the first covalent synthesis of kappa-carrageenan-3'-azido-3'-deoxythymidine (AZT) conjugates. A succinate diester spacer was used to covalently couple AZT onto kappa-carrageenan, resulting in a tripartite prodrug. Two methods (UV and radioactive counting) are described and validated to determine the AZT loading onto the kappa-carrageenan carrier. This polymeric carrier, through its own intrinsic anti-HIV activity, is expected to act not only as a drug delivery agent but also as an anti-HIV agent. Synergism between the two drugs (kappa-carrageenan and AZT) was demonstrated when MT-4 cells were preincubated with the kappa-carrageenan-AZT conjugate prior to HIV-1-infection. A threshold of AZT loaded onto the kappa-carrageenan was required to achieve this synergistic effect. Such kappa-carrageenan-AZT conjugates could be of great therapeutic interest because these conjugates, which contain a low AZT concentration, present improved anti-HIV activities relative to free AZT. Moreover, kappa-carrageenan is a well-tolerated biopolymer, already used in the food industry.     

两种AZT-氟喹诺酮偶联物体外抗HIV-1及抗菌活性的研究

目的体外测定两种AZT-氟喹诺酮偶联物SRLZ和SROZ的抗HIV-1活性及抗菌活性。方法通过合胞体抑制、HIV-1感染细胞保护、HIV-1 p24抗原测定等方法检测急性感染中化合物对HIV-1实验株、临床分离株的抑制作用和对慢性感染细胞中的病毒复制影响;通过体外金黄色葡萄球菌的抑制实验检测化合物的抗菌活性。结果AZT-氟喹诺酮偶联物SRLZ和SROZ能抑制HIV-1实验株诱导的合胞体形成,减少病毒感染细胞的死亡和抑制病毒在细胞内的复制;SRLZ和SROZ对HIV-1临床分离株也有较好的抑制作用;SRLZ和SROZ对HIV-1的抑制活性与AZT相近;AZT-氟喹诺酮偶联物也能抑制金黄色葡萄球菌,其MIC值与其相应的阳性药物相近。结论SRLZ和SROZ有很好的抗HIV-1活性和抗菌活性。     

Drug-antibody conjugates with anti-HIV activity

Human immunodeficiency virus (HIV)-specific peptide antibody-brefeldin A conjugates and antibody-glaucarubolone conjugates directed to cell surface viral glycoprotein epitopes were prepared and tested for antiviral activity. A selective response was observed both on survival of cell lines permanently infected with lentiviruses and on HIV infectivity. With human peripheral blood mononuclear cells (PBMCs), the conjugate also was effective in reducing virus titers. The effectiveness of an HIV-specific peptide antibody-brefeldin A conjugate was enhanced by combination with 3'-azido-3'-deoxythymidine (AZT) and was effective against AZT-resistant isolates in combination with AZT. The conjugates reduced virus production in MOLT-4 cells and in HIV-1-infected PBMCs without affecting the viability of uninfected cells.     

New 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate prodrugs: synthesis and anti-HIV evaluation

Prodrugs of zidovudine (AZT) have been synthesized in an effort to enhance its uptake by HIV-1 infected cells and its anti-HIV activity. The 5'-OH function of AZT was functionalized with various enzymatically labile alkyl groups using specific procedures. The prodrug moieties included 5'-O-carbonate, 5'-O-carbamate, and 5'-O-ester. Analogues of the 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate series were particularly interesting since they were rearranged through an intramolecular cyclic process during their enzymatic hydrolysis. Evidence of this prodrug rearrangement was confirmed by comparison of the serum half-lives of 5'-O-carbonate prodrugs with their corresponding 5'-O-ester- and 5'-O-carbamate-AZT prodrugs. Interestingly, the anti-HIV-1 activities (EC(50)) of 3'-azido-3'-deoxythymidin-5'-yl O-(4-hydroxybutyl) carbonate 10 in acutely infected MT-4 cells and in peripheral blood mononuclear cells (PBMCs) were 0.5 nM and 0.78 nM, respectively. Compound 10 was 30 to 50 times more potent than its parent drug AZT. Our results suggest that the specific intramolecular rearrangement associated with the 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate prodrugs could explain the remarkable anti-HIV-1 activity of this series of AZT prodrugs. Prodrug 10 may therefore have better clinical potential than AZT for the treatment of AIDS.     

Synthesis and anti-HIV evaluation of 2',3'-dideoxyribo-5-chloropyrimidine analogues: reduced toxicity of 5-chlorinated 2',3'-dideoxynucleosides

In view of the selective anti-HIV activity of 2',3'-dideoxy-3'-fluoro-5-chlorouridine (11), a series of eight 2',3'-dideoxy-5-chloropyrimidines were synthesized and evaluated for their inhibitory activity against human immunodeficiency virus type 1 (HIV-1) replication in MT-4 cells. A marked improvement in selectivity was noted for the 5-chlorouracil derivatives of 2,3-dideoxyribofuranose, 3-azido-2,3-dideoxyribofuranose, and 3-fluoro-2,3-dideoxyribofuranose, mainly due to decreased toxicity of the compounds for the host cells. While chlorination of 2',3'-dideoxycytidine removed the anti-HIV activity, introduction of a chlorine at the C-5 position of 3'-fluoro-, 3'-azido- or 2',3'-didehydro-2',3'-dideoxycytidine led to reduced cytotoxicity with only slightly reduced anti-HIV activity. X-ray analysis showed compound 11 to have two molecules in the asymmetric unit with chi = -168.8 (3) degrees and -131.3 (3) degrees and P = 179 (1) degree and 163 (1) degree, respectively; thus revealing no close resemblance to 3'-azido-3'-deoxythymidine (AZT).     

Ether phospholipid-AZT conjugates possessing anti-HIV and antitumor cell activity. Synthesis, conformational analysis, and study of their thermal effects on membrane bilayers

The 1-O-hexadecyl-2-O-methyl-sn-glyceryl phosphodiester AZT 4 and hexadecyl-phosphodiester AZT 5 derivatives were synthesized and found to be active against HIV-1, HIV-2, and tumor cell proliferation. Compared to AZT, compound 4 possessed ca. 10-fold lower anti-HIV activity and ca. 10-fold higher anti-tumor cell activity. Compound 5 was 10-fold less potent than compound 4 in both biological tests. In an attempt to correlate biological activity of compounds 4 and 5 with structure, their conformational and thermal effects on membrane bilayers were compared using a combination of NMR spectroscopy, computational analysis, and Differential Scanning Calorimetry. The obtained results showed that compound 4 adopts a compact conformation in which the alkyl chain, the 2-methoxyglyceryl functionality, and the methyl group of thymine are in spatial proximity, while analogue 5 possesses a less compact conformation of the nucleoside base and the alkyl chain. The presence of the 2-methoxyglyceryl group in compound 4 may augment its potency by inducing a turn of the alkyl chain stabilized by hydrophobic interactions. The DSC scans show that conjugate 4 affects less effectively the thermotropic properties of model membrane bilayers than compound 5. This may be attributed to the fact that compound 4 is incorporated in a compact conformation and does not perturb significantly the trans:gauche isomerization of the membrane phospholipids. In contrast, conjugate 5 may enter with a less compact conformation and perturb more the membrane bilayers.     

Inhibition of Human Mammary Cell Line Proliferation by Membrane Lectin-Mediated Uptake of Ha-ras Antisense Oligodeoxynucleotide

The Ha-ras oncogene promotes cell proliferation. Antisense oligonucleotides complementary to the ras gene sequence encompassing a mutated codon 12 selectively induce a cell proliferation inhibition. However, the concentration required to reach an effective inhibition is high due to the low efficiency of the oligonucleotide crossing through cell membranes, leading to a low concentration in the cytosol and/or the nucleoplasm. In the present paper, we show that anti-ras oligonucleotides linked to a glycosylated carrier, serum albumin bearing mannose 6-phosphate residues, are more efficient than free oligonucleotides or oligonucleotides bound to an unglycosylated carrier at inhibiting proliferation of a human tumor mammary cell line expressing the mutated Ha-ras. Using fluorescein-labeled neoglycoproteins and fluorescein-labeled oligonucleotides bound to neoglycoproteins, flow cytometry and confocal microscopy revealed that (i) these tumor cells express a membrane lectin specific for mannose 6-phosphate-bearing proteins, (ii) the membrane lectin actively mediates the uptake of macromolecules substituted with mannose 6-phosphate, and (iii) the fluorescein-labeled oligonucleotides bound to the neoglycoprotein accumulate in intracellular vesicles. Furthermore, with antisense oligonucleotides carried by the neoglycoproteins, the concentration required to inhibit cell proliferation is lower than that of the carrier-free antisense oligonucleotides.     

Biotin/Folate‐decorated Human Serum Albumin Nanoparticles of Docetaxel: Comparison of Chemically Conjugated Nanostructures and Physically Loaded Nanoparticles for Targeting of Breast Cancer

Docetaxel (DTX) is a widely used chemotherapeutic agent with very low water solubility. Conjugation of DTX to human serum albumin (HSA) is an effective way to increase its water solubility. Attachment of folic acid (FA) or biotin as targeting moieties to DTX‐HSA conjugates may lead to active targeting and specific uptake by cancer cells with overexpressed FA or biotin receptors. In this study, FA or biotin molecules were attached to DTX‐HSA conjugates by two different methods. In one method, FA or biotin molecules were attached to remaining NH₂ residues of HSA in DTX‐HSA conjugate by covalent bonds. In the second method, HSA‐FA or HSA‐biotin conjugates were synthesized separately and then combined by DTX‐HSA conjugate in proper ratio to prepare nanoparticles containing DTX‐HSA plus HSA‐FA or HSA‐biotin. Cell viability of different nanoparticle was evaluated on MDA‐MB‐231 (folate receptor positive), A549 (folate receptor negative), and 4T1 (biotin receptor positive) and showed superior cytotoxicity compared with free docetaxel (Taxotere^®). In vivo studies of DTX‐HSA‐FA and DTX‐HSA‐biotin conjugates in BULB/c mice, tumorized by 4T1 cell line, showed the conjugates prepared in this study were more powerful in the reduction in tumor size and increasing the survival rate when compared to free docetaxel.     

Relationship of deoxynucleotide changes to inhibition of DNA synthesis induced by the antiretroviral agent 3'-azido-3'-deoxythymidine and release of its monophosphate by human lymphoid cells (CCRF-CEM)

The metabolism and cytostatic effects of 3'-azido-3'-deoxythymidine (AZT), one of the most effective agents being used in the treatment of acquired immunodeficiency syndrome, were investigated in the CCRF-CEM line of human T lymphoid cells. The concentration of drug required to inhibit cell growth by 50% (CD50) was significantly lower when the cells were exposed to AZT for 24 hr (CD50 = 50 microM), as compared with 48 or 96 hr (CD50 = 225 and greater than 300 microM, respectively). AZT at 25 microM blocked the progression of cells in S phase for about 12 hr, but this effect was reversed by 24 hr, despite the continued presence of drug in the medium. At this drug concentration, the level of dTTP decreased to about 75% of the control level by 4 hr but rebounded to 30% above normal by 8 hr of drug exposure. dGTP and dATP pool sizes were unchanged, whereas the dCTP pool increased 5-fold. The time course of these biochemical changes indicated that the onset of S phase arrest was not directly related to the decrease in deoxynucleoside triphosphate pools. CCRF-CEM cells incubated with 25 microM AZT accumulated about 0.9 mM 5'-monophosphate (AZTMP) after 4 hr whereas levels of the 5'-di- and 5'-triphosphates (AZTDP and AZTTP) plateaued at about 2 and 5 microM, respectively. After this period, there was a rapid decrease in AZTMP accumulation, to one third its initial level by 24 hr, whereas AZTDP and AZTTP pools decreased to only about 70%. The loss in AZT nucleotide formation with time of drug exposure was associated with a concomitant accumulation of AZTMP in the medium. Cellular excretion of AZTMP was not associated with any detectable cell lysis or leakage of other cellular metabolites. The ability of CCRF-CEM cells to excrete AZTMP may be an important factor limiting the biochemical and biological effects of the drug.     

Correlation of anti-HIV activity with anion spacing in a series of cosalane analogues with extended polycarboxylate pharmacophores

Cosalane and its synthetic derivatives inhibit the binding of gp120 to CD4 as well as the fusion of the viral envelope with the cell membrane. The binding of the cosalanes to CD4 is proposed to involve ionic interactions of the negatively charged carboxylates of the ligands with positively charged arginine and lysine amino acid side chains of the protein. To investigate the effect of anion spacing on anti-HIV activity in the cosalane system, a series of cosalane tetracarboxylates was synthesized in which the two proximal and two distal carboxylates are separated by 6--12 atoms. Maximum activity was observed when the proximal and distal carboxylates are separated by 8 atoms. In a series of cosalane amino acid derivatives containing glutamic acid, glycine, aspartic acid, beta-alanine, leucine, and phenylalanine residues, maximum activity was displayed by the di(glutamic acid) analogue. A hypothetical model has been devised for the binding of the cosalane di(glutamic acid) conjugate to CD4. In general, the compounds in this series are more potent against HIV-1(RF) in CEM-SS cells than they are vs HIV-1(IIIB) in MT-4 cells, and they are least potent vs HIV-2(ROD) in MT-4 cells.     

Intracellular metabolism of CycloSaligenyl 3'-azido-2', 3'-dideoxythymidine monophosphate, a prodrug of 3'-azido-2', 3'-dideoxythymidine (zidovudine)

The administration of CycloSaligenyl 3'-azido-2',3'-dideoxythymidine monophosphate (CycloSal-AZTMP) to CEM cells resulted in a concentration- and time-dependent conversion to the 5'-monophosphate (AZTMP), 5'-diphosphate (AZTDP), and 5'-triphosphate (AZTTP) derivatives. High ratios of AZTMP/AZTTP were found in the CEM cell cultures treated with CycloSal-AZTMP. The intracellular T(1/2) of AZTTP in CEM cell cultures treated with either AZT and CycloSal-AZTMP was approximately 3 h. A variety of human T- and B-lymphocyte cell lines efficiently converted the prodrug to the AZT metabolites, whereas peripheral blood lymphocytes and primary monocyte/macrophages showed at least 10-fold lower metabolic conversion of the prodrug. CycloSal-AZTMP failed to generate marked levels of AZT metabolites in thymidine kinase-deficient CEM/TK(-) cells, an observation that is in agreement with the substantial loss of antiviral activity of CycloSal-AZTMP in CEM/TK(-) cells. The inability of CycloSal-AZTMP to generate AZTMP in CEM/TK(-) cells is presumably due to a relatively high hydrolysis rate of AZTMP to the parent nucleoside AZT, combined with the inability of CEM/TK(-) cells to phosphorylate AZT to AZTMP through the cytosolic salvage enzyme thymidine kinase.     

应用细胞模型初筛抗人免疫缺陷病毒药物

目的探讨采用已建立的细胞模型初筛抗人免疫缺陷病毒(HIV)药物的可靠性。方法以齐多夫定为阳性对照,使用HIV-1急性感染系统(MT-4/HIV-1ⅢB)、HIV-1耐药性毒株系统(MT-4/3TC耐药株)、HIV-1慢性感染系统(H9/HIV-1ⅢB)和HIV-1临床分离株感染系统(PBMC/HIV-1GX02),分别测定药物的细胞毒性和抗HIV-1活性,计算药物的半数细胞毒性浓度(TC50)、半抑制浓度(IC50)和治疗指数(TI)。同时对4种药物DPC961、牛膝多糖、艾乃吉1号和痰热清注射液进行了抗HIV活性检测。结果测定了齐多夫定在4种细胞-病毒系统的TC50,IC50和TI与文献报道相近。DPC961在4种细胞/病毒培养系统的TI分别为979,5348,3912和2745;牛膝多糖分别为323,223,2777和173;艾乃吉1号仅在MT-4/HIV-1ⅢB模型上T1为2.6。结论使用本细胞模型通过检测药物的TC50,IC50及TI进行药物初筛是可靠的。药物DPC961、牛膝多糖和艾乃吉Ⅰ号具有不同程度的体外抗HIV-1活性,痰热清注射液未检测到抗HIV-1活性。     

Synthesis and evaluation of novel ether lipid nucleoside conjugates for anti-HIV-1 activity

Combinations of an amidoalkylphosphocholine, 8, and AZT have been found to cause an apparent synergistic action in suppressing infectious HIV-1 replication. In addition, amidoalkyl, oxyalkyl, and thioalkyl ether lipids have been chemically linked to anti-HIV-1 nucleosides (AZT and DDI) through phosphate and phosphonate linkages. These conjugates have shown promising in vitro anti-HIV-1 activity. Also, the conjugates have a 5-10-fold reduction in cell cytotoxicity compared to AZT alone. The most active compound, an amidoalkyl ether lipid-AZT conjugates, 4A, was found to have a differential selectivity of 1793 in a syncytial plaque assay. In comparison, AZT alone has a value of 1281.