A novel, long-circulating, and functional liposomal formulation of antisense oligodeoxynucleotides targeted against MDR1

The goal of this study was to develop a small, stable liposomal carrier for antisense oligodeoxynucleotides (asODN) that would have high trapping efficiencies and long circulation times in vivo. Traditional cationic liposomes aggregate to large complexes and, when injected intravenously, rapidly accumulate in the liver and lung. We produced charge-neutralized liposome-asODN particles by optimizing the charge interaction between a cationic lipid and negatively charged asODN, followed by a procedure in which a layer of neutral lipids coated the exterior of the cationic lipid-asODN particle. The coated cationic liposomes had an average diameter of 188 nm and entrapped 85-95% of the asODN. The biodistribution and pharmacokinetics of an 18-mer 125I-labeled phosphorothioate ODN formulated by this method were determined after tail vein injection in mice. The majority of the asODN was cleared from blood, with a half-life of >10 hours compared with <1 hour for free asODN. When coupled with an anti-CD19 targeted antibody, this formulation was also effective at delivering an MDR1 asODN to a multidrug-resistant human B-lymphoma cell line in vitro, decreasing the activity of P-glycoprotein. No inhibition was found for nontargeted formulations or for free asODN. A number of therapeutic opportunities exist for the use of small, stable, long-circulating, and targetable liposomal carriers such as this, with high trapping efficiencies for asODN.

4-(beta-Arylvinyl)-3-(beta-arylvinylketo)-1-ethyl-4-piperidinols and related compounds: a novel class of cytotoxic and anticancer agents

The syntheses of a series of 1-aryl-5-diethylamino-1-penten-3-one hydrochlorides 1 and 1-aryl-3-diethylamino-1-propanone hydrochlorides 4 were accomplished. Attempts to prepare the corresponding bis(5-aryl-3-oxo-4-pentenyl)ethylamine hydrochlorides 2 and bis(3-aryl-3-oxopropyl)ethylamine hydrochlorides 5 led to the formation of a series of 4-(beta-arylvinyl)-3-(beta-arylvinylketo)-1-ethyl-4-piperidi nol hydrochlorides 9 and 4-aryl-3-arylketo-1-ethyl-4-piperidinol hydrochlorides 11, most of which were converted subsequently into the corresponding quaternary ammonium salts 10 and 12, respectively. The structures of these compounds were determined by 1H NMR spectroscopy and confirmed by X-ray crystallography of representative molecules. Most compounds displayed significant cytotoxicity toward murine P388 and L1210 cells as well as human tumors. In general, Mannich bases containing olefinic bonds were more cytotoxic than the analogues without this functional group, while the piperidines 9 and 11 were more potent than the acyclic analogues 1 and 4, respectively. Correlations were noted between various physicochemical constants in the aryl rings and cytotoxicity. Compound 9d displayed promising in vivo activity against colon cancers. This study has revealed that the piperidines 9 and 11 constitute new classses of cytotoxic agents.

Synthesis and cytotoxic evaluation of some carbohydrazones and thiocarbohydrazones of various unsaturated ketones and related Mannich bases

A number of 1-aryl-1-penten-3-ones 1 and related Mannich bases 2 were synthesized and converted either directly or indirectly to the corresponding biscarbohydrazones 3 and 4. Reaction of representative unsaturated ketones with thiocarbohydrazide led to the formation of only the monothiocarbohydrazones 5. The cytotoxicity of these compounds against murine P388 and L1210 cells, human T-lymphocytes and human tumour cell lines was undertaken in order to ascertain their bioactivity and review these data in the light of the theory of sequently cytotoxicity whereby the carbohydrazones would be predicted to be more than twice as cytotoxic as the ketones and Mannich bases from which they were derived. In general, conversion of 1 into 3 was accompanied by a lowering of cytotoxicity. On the other hand, in general the compounds in series 4 were significantly more potent cytotoxic agents than the analogues 2; in fact, some compounds displayed activity comparable with or exceeding that of melphalan. Thus the biscarbohydrazones 4 represent a novel group of cytotoxic agents serving as lead molecules for subsequent development.

Use of targeted cationic liposomes in enhanced DNA delivery to cancer cells

Cationic liposomes are considered to be safe vectors for gene transfer, but they are less efficient at delivering DNA to cells when compared with retroviral vectors. Cationic liposomes complexed with DNA were targeted to specific cells in vitro by means of monoclonal antibodies (mAbs) or ligands associated with the liposomes. Significant increases in expression of a beta-galactosidase reporter gene were observed in vitro in mAb-targeted liposomes, compared with non-targeted liposomes, in both an adherent tumor cell line (human adenocarcinoma) and a suspension cell line (human T-lymphoma). Also, use of asialofetuin as a targeting ligand significantly increased expression of the reporter gene in human hepatoma cells. Our results suggest that site-specific targeting of cationic liposomes is a good strategy for increasing both the selectivity and the efficiency of DNA delivery to cells and with further development may lead to targeted DNA delivery in vivo.

Attachment of antibodies to sterically stabilized liposomes: evaluation, comparison and optimization of coupling procedures

Several coupling methods for binding antibodies (Ab) to liposomes have previously been developed. We were interested in examining if some of these methods would be suitable for attaching Ab to long-circulating formulations of liposomes (SL), sterically stabilized with poly(ethylene glycol) (PEG). We studied three 'classical' coupling methods in which Ab was attached at the bilayer surface of SL, and two new coupling methods in which Ab was attached at the PEG terminus. Parameters examined including binding efficiency, antibody surface density, the ability of the immunoliposomes to remote-load the anticancer drug doxorubicin, and the specific binding of the resulting immunoliposomes to target cells. The non-covalent biotin-avidin coupling method resulted in low Ab densities at the cell surface, as did a coupling in method in which maleimide-derivatized Ab was attached to the liposome surface through a thiolated phospholipid incorporated into the liposomes. The low levels of Ab achieved in these method was likely due to interference by PEG with the access of the Ab to the liposome surface. However, when a maleimide-derivatized Ab was coupled to thiolated PEG, moving the coupling reaction away from the liposome surface, very high coupling efficiencies were achieved, and these immunoliposomes achieved good specific binding to their target cells. Oxidizing the Fc region of the Ab and coupling it to the PEG terminus through a hydrazone bond was a less efficient coupling method, but had the advantage of retaining Ab orientation. Efficient remote-loading of doxorubicin was found for immunoliposomes in which Ab was attached at the PEG terminus.

Synthesis and cytotoxic evaluation of some Mannich bases of alicyclic ketones

A number of Mannich bases of alicyclic ketones containing one and two basic centres were prepared in order to evaluate the theory of sequential cytotoxicity and develop structure-activity relationships in these series of compounds. The compounds were evaluated in vitro against murine P388 D1 lymphocytic leukemia cells. The data generated supported the theory of sequential cytotoxicity and in general, compounds containing alicyclic rings of five and six carbon atoms possessed greater activity than the corresponding dodecyl analogues. Those Mannich bases containing dialkylamino groups were associated with greater cytotoxicity than related compounds possessing a basic heterocycle. Calculations of the atomic charges of the enone groups from selected compounds afforded some rationalization for the cytotoxic screening results.

A new strategy for attachment of antibodies to sterically stabilized liposomes resulting in efficient targeting to cancer cells

The development of long-circulating formulations of liposomes (S-liposomes), sterically stabilized with lipid derivatives of poly(ethylene glycol) (PEG), has increased the likelihood that these liposomes, coupled to targeting ligands such as antibodies, could be used as drug carriers to deliver therapeutic drugs to specific target cell populations in vivo. We have developed a new methodology for attaching monoclonal antibodies to the terminus of PEG on S-liposomes. A new end-group functionalized PEG-lipid derivative pyridylthiopropionoylamino-PEG- distearoylphosphatidylethanolamine (PDP-PEG-DSPE) was synthesized for this purpose. Incorporation of PDP-PEG-DSPE into S-liposomes followed by mild thiolysis of the PDP groups resulted in formation of reactive thiol groups at the periphery of the lipid vesicles. Efficient attachment of maleimide-derivatized antibodies took place under mild conditions even when the content of the functionalized PEG-lipid in S-liposomes was below 1% of total lipid. The resulting S-immunoliposomes showed efficient drug remote loading, slow drug release rates and increased survival times in circulation compared to liposomes lacking PEG. When antibodies recognizing several different tumor-associated antigens were coupled to the PEG terminus of S-liposomes a significant increase in the in vitro binding of liposomes to the target cells was observed. The binding of S-immunoliposomes containing entrapped doxorubicin to their target cell population resulted in increased cytotoxicity compared to liposomes lacking the targeting antibody.

Synthesis and cytotoxic evaluation of mesna adducts of some 1-aryl-4,4-dimethyl-5-(1-piperidino)-1-penten-3-one hydrochlorides

Reaction of 1-(4-bromophenyl)-4,4-dimethyl-5-(1-piperidino)-1-penten-3-one hydrochloride (1f) with sodium 2-mercaptoethanesulphonate (mesna) gave rise to the thiol adduct. 3. Recrystallization of this compound led to the formation of the corresponding zwitterion 4f. A series of analogues of 4f were prepared and the structure of a representative compound was confirmed by X-ray crystallography. In general, the thiol adducts had similar activity towards P388 cells and human tumour cell lines as the precursor enones 1 although greater selectivity to malignant diseases was found with the thiol adducts. A stability study of representative compounds conducted by 1H NMR spectroscopy revealed that the thiol adducts decomposed in solution. In one case regeneration of the ketone was noted while for the other compounds, the decomposition products were not identified.

Cytotoxic evaluation of some 3,5-diarylidene-4-piperidones and various related quaternary ammonium compounds and analogs

A number of 3,5-diarylidene-4-piperidones (1) and some related quaternary ammonium salts (5) as well as closely related analogs were prepared principally as candidate cytotoxic agents in two screens. The first test system used an average of 54 human tumor cell lines from eight neoplastic diseases, namely leukemia, melanoma, colon, non-small-cell lung, small-cell lung, central nervous system, ovarian, and renal cancers. Selective toxicity was demonstrated by some of the compounds, especially toward leukemia. The second screen used L1210 lymphoid leukemia cells. In general, the compounds were less cytotoxic than the reference drug melphalan in both screens. Linear plots were made between the Hammett (sigma), fragment (f), and molar refractivity (MR) constants of the nuclear substituents in series 1 and 5 with the IC50 figures of both the human tumor cell lines and L1210 cells. Evaluation against the human tumor cell lines revealed that increases in the f values were correlated with elevation of cytotoxicity in both series 1 and 5; MR constants were also important in series 5. In the L1210 screen, sigma and MR constants were positively correlated with cytotoxicity. X-ray crystallography was undertaken on 3,5-bis-[[4'-(methylthio)phenyl]methylene]-1-methyl-4-piperidone methiodide (5d), which had significant cytotoxicity, and 3,5-bis(4-pyridylmethylene)-1-methyl-4-piperidone methiodide (6), which was virtually inactive in both screens.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytotoxic evaluation of some N-acyl and N-acyloxy analogues of 3,5-bis(arylidene)-4-piperidones

The preparation of thirteen N-acyl and N-acyloxy analogues of two 3,5-bis(arylidene)-4-piperidones were prepared as potential prodrugs of the parent ketones. Approximately half of the compounds demonstrated antileukemic properties when evaluated against murine L1210 lymphoid leukemia cells. Three of the derivatives were more active than or equipotent with the reference drug melphalan. All of the compounds were examined against approximately 55 human tumours representing eight different neoplastic diseases. Not only were most of the compounds more cytotoxic than melphalan but 60% of the derivatives displayed selective toxicity to leukemia. A stability study of six of the candidate prodrugs using 1H NMR spectroscopy revealed that while some decomposition in solution occurred, the parent amine was not liberated.

Synthesis and cytotoxic evaluation of some cyclic arylidene ketones and related oximes, oxime esters, and analogs

A number of arylidene derivatives of alicyclic ketones and some corresponding oximes, oxime esters, and related compounds were prepared as candidate cytotoxic agents. All of the compounds were evaluated against murine L1210 lymphoid leukemia cells. In general, cytotoxicity was greatest with the alpha,beta-unsaturated ketones and diminished with the oximes, and the oxime esters had little or no activity in this screen. When the same compounds were examined in both the in vitro L1210 and P388 leukemia screens, in the majority of cases the L1210 cells were more sensitive to these derivatives. Over half of the compounds prepared were evaluated against approximately 55 human tumors in vitro and showed selective toxicity toward one or more groups of neoplastic diseases, particularly leukemia. Some correlations between structure and bioactivity were discerned. The cytotoxicity screening and stability studies of representative compounds suggested that the ketones, oximes, and oxime esters were stable under the conditions of bioevaluation. X-ray crystallography of four representative compounds revealed structural features associated with cytotoxicity which may be considered in the design of future candidate cytotoxins.

Evaluation of some N-acyl analogues of 3,5-bis(arylidene)-4-piperidones for cytotoxic activity

The synthesis of fourteen N-acyl derivatives of two 3,5-bis(arylidene)-4-piperidones was accomplished and these compounds were evaluated against L1210 leukemia cells in vitro. With one exception, the compounds had IC50 values of less than 10 microM and six of them had IC50 figures in the 0.2-0.6 microM range which were comparable to a reference drug melphalan. Twelve of the sixteen compounds showed specificity for human leukemia cell lines in the NCI in vitro screen. Studies using 1H NMR spectroscopy revealed that solutions of three N-acetylated compounds underwent deamination and possibly other reactions, the deaminated product itself being unstable in the solvent used.

3,5-Bis-arylidene-1-methyl-4-piperidone methohalides and related compounds with activity against L 1210 cells and DNA binding properties

A series of 3,5-bis-arylidene-1-methyl-4-piperidone methohalides 2 and two related analogues in general demonstrated activity against L 1210 leukemia cells in vitro and bound to a synthetic DNA, poly[d(AT)]. Plots of various physicochemical constants of the aromatic substituents in series 2 versus the IC50 figures revealed correlations between the aryl MR and pi values but not the sigma constants. The delta Tm values of six members of series 2 were correlated with the MR figures of the aryl substituents but not the sigma nor pi values of the aromatic atoms and groups. Some suggestions for future molecular modification with a view to increasing cytotoxicity are presented.

Effect of probenecid on rat brain phenolsulfotransferase activity using dopamine as substrate

Dopamine sulfate (DAS) is formed by the action of phenolsulfotransferase (PST) on dopamine (DA). Since probenecid is often used to investigate the transport of monoamine acidic metabolites such as DAS from the brain, we investigated the effect of probenecid on rat brain PST activity utilizing DA as substrate. In the presence of 30 or 90 microM DA, probenecid had either no effect or a dose-related inhibitory effect on PST activity. PST activity increased at low probenecid concentrations, but decreased at high probenecid concentrations when 360 microM DA was utilized. Several conditions were found where PST activity was not affected by probenecid.