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Preparation and targeted delivery of immunoliposomes bearing poly(ethylene glycol)-coupled humanized anti-hepatoma disulfide-stabilized Fv (hdsFv25) in vitro.

Peptides in bee venom (PBV) have attracted considerable attention for anti-cancer therapy. In this study, sterically stabilized liposomal PBV (PBV-SL) was prepared using Soybean phosphatidylcholine, cholesterol, and the cholesterol derivatives of PEG with terminal COOH groups. The humanized anti-hepatoma disulfide-stabilized Fv (hdsFv25) was coupled to sterically stabilized liposomes. The hdsFv25-immunoliposome has strong affinity and specificity to SMMC-7721 cells in vitro. PBV-loaded sterically stabilized liposomes modified with the hdsFv25 can kill SMMC-7721 cells in vitro with higher efficiency than non-targeted liposomes. These results demonstrate that this strategy should also be applicable to immunotherapy for other cancers.

Antineoplastic Agents↗

Targeted delivery of peptide epitopes to class I major histocompatibility molecules by a modified Pseudomonas exotoxin.

Cytotoxic T lymphocytes (CTLs) expressing the CD8 surface marker recognize peptides in association with major histocompatibility complex (MHC) class I molecules. Although most peptides expressed on MHC class I molecules are derived from self- or virally encoded proteins, delivery of exogenous proteins to the cytosol can result in their being processed for presentation to CTLs on MHC class I molecules. We describe two fusion proteins (PEMa and PENP), consisting of the binding and translocating domains of Pseudomonas exotoxin A (PE), fused to peptide epitopes from influenza A matrix protein and nucleoprotein, respectively. These fusion proteins were internalized and processed by MHC class I-positive target cells, resulting in sensitization of target cells for lysis by peptide-specific CTLs. A point mutation known to interfere with intoxication by wild-type PE also reduced the ability of PEMa to sensitize target cells. Fusion of peptide or polypeptide epitopes with PE provides a potential means of eliciting CTLs without the use of self-replicating agents, as well as a useful probe for studying MHC class I-restricted antigen processing.

ADP Ribose Transferases↗

Targeted delivery of antibiotics using liposomes and nanoparticles: research and applications.

This review examines current technologies for increasing the bioavailability of antibiotics by means of liposomes or nanoparticles. The main focus is on liposomes. These carriers were preferentially developed because their composition is compatible with biological constituents. Biodegradable polymers in the form of colloidal particles have also been used and show promise for future applications in antimicrobial chemotherapy. The in vivo behaviour of both types of carriers and consequently their therapeutic potential, are determined by their route of administration. Conventional carrier strategies permit the mononuclear phagocyte system to be targeted by intravenous injection of antibiotics. Stealthy strategies avoid major uptake by these cells and extend the systemic presence of these carriers. The purpose of this review is to provide background information in antibiotic targeting gathered from papers published over the last twenty years. It seems clear that such drug carriers (liposomes, nanoparticles) allow increased drug concentration at infected sites but reduce drug toxicity.

Aminoglycosides↗

[Features of incorporation of several antibiotics into erythrocyte ghosts--a system of targeted delivery of chemotherapeutic drugs].

Features of incorporation of cefazolin, ampicillin, kanamycin and gentamicin into erythrocytic shadows in patients with abdominal diseases and apparently healthy persons during hypoosmotic hemolysis were studied. The highest percentage of kanamycin and gentamicin incorporation into the erythrocytic shadows was observed. The parameter of the antibiotic incorporation from the incubation fluid into the erythrocytic shadows depended on the antibiotic type and dose. Rather significant resistance of the erythrocytic carriers with incorporated gentamicin to possible desorption and excretion of the antibiotic from the shadows into the blood flow was revealed which made their use possible for target release of antibiotics in the liver.

Aminoglycosides↗

Enhanced inhibition of murine tumor and human breast tumor xenografts using targeted delivery of an antibody-endostatin fusion protein.

Endostatin can inhibit angiogenesis and tumor growth in mice. A potential limitation of endostatin as an antitumor agent in humans is the short serum half-life of the protein that may decrease effective concentration at the site of tumor and necessitate frequent dosing. In an effort to improve antitumor activity, endostatin was fused to an antibody specific for the tumor-selective HER2 antigen to create an antibody-endostatin fusion protein (anti-HER2 IgG3-endostatin). Normal endostatin rapidly cleared from serum in mice (T(1/2)(2), = 0.6-3.8 hours), whereas anti-HER2 IgG3-endostatin had a prolonged half-life (90% intact; T(1/2)(2), 40.2-44.0 hours). Antigen-specific targeting of anti-HER2 IgG3-endostatin was evaluated in BALB/c mice implanted with CT26 tumors or CT26 tumors engineered to express the HER2 antigen (CT26-HER2). Radio-iodinated anti-HER2 IgG3-endostatin preferentially localized to CT26-HER2 tumors relative to CT26 tumors. Administration of anti-HER2 IgG3-endostatin to mice showed preferential inhibition of CT26-HER2 tumor growth compared with CT26. Anti-HER2 IgG3-endostatin also markedly inhibited the growth of human breast cancer SK-BR-3 xenografts in severe combined immunodeficient mice. Anti-HER2 IgG3-endostatin inhibited tumor growth significantly more effectively than endostatin, anti-HER2 IgG3 antibody, or the combination of antibody and endostatin. CT26-HER2 tumors treated with the endostatin fusion protein had decreased blood vessel density and branching compared with untreated CT26-HER2 or CT26 treated with the fusion protein. The enhanced effectiveness of anti-HER2 IgG3-endostatin may be due to a longer half-life, improved serum stability, and selective targeting of endostatin to tumors, resulting in decreased angiogenesis. Linking of an antiangiogenic protein, such as endostatin, to a targeting antibody represents a promising and versatile approach to antitumor therapy.

Angiogenesis Inhibitors↗

Targeted delivery of inhaled drugs: current challenges and future goals.

Past success of topical delivery to the lung stems more from the therapeutic nature of drugs used rather than the delivery device. Both the pressurized metered dose inhaler (pMDI) and the dry powder inhaler (DPI) are inefficient, placing a small fraction of the dose at the site of action. Most of the drug deposits in the mouth and is swallowed. Modifications to the pMDI may redress this by improving the coordination of dose generation and inspiration, or by the use of spacers. The DPI can be improved by the use of special excipients. Nevertheless, fundamental weaknesses that limit improvements in targeting drugs to the lung remain. Ideally, a stationary or slow-moving cloud of a selected particle size distribution should be generated at the source by the device. The rate of cloud generation should be such that a patient can accommodate it during a slow inspiration. Many new devices are in development, harnessing one or more of these principles. Respimat (Boehringer Ingelheim, Ingelheim am Rhein, Germany), a soft mist inhaler, shows particular promise. It generates a fine slow-moving cloud over a period exceeding 1 second and incorporates many design features to win patient acceptance.

Administration, Inhalation↗

High-loading nanosized micelles of copoly(styrene-maleic acid)-zinc protoporphyrin for targeted delivery of a potent heme oxygenase inhibitor.

Amphiphilic styrene-maleic acid (SMA) copolymer efficiently formed micelles with a potent heme oxygenase inhibitor-zinc protoporphyrin (ZnPP). The micelles were constructed by subtle pH adjustments to form non-covalent interaction between the hydrophobic ZnPP and amphiphilic SMA. The micelles (SMA-ZnPP) thus formed were nanoparticles with narrow size distribution in water (mean diameter 176.5nm), having tunable loading (from 15% to 60% w/w of ZnPP) with remarkable aqueous solubility. SMA-ZnPP had an average molecular size of 144kDa as determined by size-exclusion chromatography (SEC), this size is a marked increase from the molecular weight of free ZnPP (626.03Da), suggesting the formation of micellar structure. The micelles showed a constant ZnPP release rate of about 0.5%/day in vitro at neutral pH. SMA-ZnPP micelles inhibited splenic microsomal HO-1 activity, in a competitive and dose-dependent manner, with an apparent inhibitory constant (K(i)) of 0.12mum, comparable to free ZnPP and also exhibited marked cytotoxic effect on KYSE-510 human esophageal cancer cells. The unique features of SMA-ZnPP micelles are that they are nanoparticles in aqueous solution having high water solubility and loading, yet macromolecular in nature, which can be beneficial in targeted release of a potent HO-1 inhibitor.

Biocompatible Materials↗

Poly(ethylene oxide)-modified poly(epsilon-caprolactone) nanoparticles for targeted delivery of tamoxifen in breast cancer.

This study was carried out to evaluate and compare the biodistribution profile of tamoxifen when administered intravenously (i.v.) as a simple solution or when encapsulated in polymeric nanoparticulate formulations, with or without surface-stabilizing agents. Tamoxifen-loaded, poly(ethylene oxide)-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles were prepared by solvent displacement process that allowed in situ surface modification via physical adsorption of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock polymeric stabilizer (Pluronic). The nanoparticles were characterized for particle size and surface charge. Presence of PEO chains on nanoparticle surface was ascertained by electron spectroscopy for chemical analysis (ESCA). In vivo biodistribution studies were carried out in Nu/Nu athymic mice bearing a human breast carcinoma xenograft, MDA-MB-231 using tritiated [(3)H]-tamoxifen as radio-marker for quantification. PEO-PCL nanoparticles with an average diameter of 150-250 nm, having a smooth spherical shape, and a positive surface charge were obtained with the formulation procedure. About 90% drug encapsulation efficiency was achieved when tamoxifen was loaded at 10% by weight of the polymer. Aqueous wettability, suspendability, and ESCA results showed surface hydrophilization of the PCL nanoparticles by the Pluronics. The primary site of accumulation for the drug-loaded nanoparticles after i.v. administration was the liver, though up to 26% of the total activity could be recovered in tumor at 6h post-injection for PEO-modified nanoparticles. PEO-PCL nanoparticles exhibited significantly increased level of accumulation of the drug within tumor with time as well as extended their presence in the systemic circulation than the controls (unmodified nanoparticles or the solution form). Pluronic surfactants (F-68 and F-108) presented simple means for efficient surface modification and stabilization of PCL nanoparticles to achieve preferential tumor-targeting and a circulating drug reservoir for tamoxifen.

Animals↗

Targeted delivery of indinavir to HIV-1 primary reservoirs with immunoliposomes.

The tissue distribution of indinavir, free or incorporated into sterically stabilized anti-HLA-DR immunoliposomes, has been evaluated after a single subcutaneous injection to C3H mice. Administration of free indinavir resulted in low drug levels in lymphoid organs. In contrast, sterically stabilized anti-HLA-DR immunoliposomes were very efficient in delivering high concentrations of indinavir to lymphoid tissues for at least 15 days post-injection increasing by up to 126 times the drug accumulation in lymph nodes. The efficacy of free and immunoliposomal indinavir has been evaluated in vitro. Results showed that immunoliposomal indinavir was as efficient as the free agent to inhibit HIV-1 replication in cultured cells. The toxicity and immunogenicity of repeated administrations of liposomal formulations have also been investigated in rodents. No significant differences in the levels of hepatic enzymes of mice treated with free or liposomal indinavir were observed when compared to baseline and control untreated mice. Furthermore, histopathological studies revealed no significant damage to liver and spleen when compared to the control group. Liposomes bearing Fab' fragments were 2.3-fold less immunogenic than liposomes bearing the entire IgG. Incorporation of antiviral agents into sterically stabilized immunoliposomes could represent a novel therapeutic strategy to target specifically HIV reservoirs and treat more efficiently this retroviral infection.

Alanine Transaminase↗

Targeted delivery of a substrate for P-glycoprotein to renal cysts in vitro.

Bodipy-verapamil has been tested as a fluorescent substrate for P-glycoprotein-mediated transepithelial secretion in MDCK-C5A epithelia. Net transepithelial secretion (Jnet) of [3H]vinblastine from basal-to-apical surfaces of monolayer epithelia is inhibited by taxotere, verapamil and Bodipy-verapamil primarily by a reduction in basal to apical vinblastine (Jb-a) transport. Bodipy-verapamil is itself subject to transepithelial net secretion by MDCK-C5A epithelia; at 5 microM a Jnet of -310 +/- 32 nmol cm-2 h-1 (n = 3) was observed. When MDCK-C5A cells are grown to form enclosed cysts in hydrated collagen gel. Bodipy-verapamil is accumulated within the cyst lumen showing that epithelial P-glycoprotein function may be used to target substrates to renal cysts.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Targeted delivery system for antisense oligonucleotides: a novel experimental strategy for neuroblastoma treatment.

Neuroblastoma (NB) is the most common neuroectoderma derived solid tumour of paediatric age. Since conventional treatments are often inefficient, novel therapeutic interventions are required. Among these, the use of antisense oligonucleotides (asODNs) as therapeutic antineoplastic agents has been recently investigated. Oligonucleotide in vivo applicability is impaired from their high sensitivity to cellular nuclease degradation. Encapsulating them within liposomes could nevertheless increase their stability. C-myb gene expression has been reported in several solid tumours of different embryonic origin, including NB, where it is linked to cell proliferation and/or differentiation. We performed a new technique to encapsulate c-myb antisense oligonucleotides within lipid particles. Liposomes resulting from this technique were called coated cationic liposomes (CCLs), since they were made up of a central core of a cationic phospholipid bound to myb-asODNs, and an outer shell of neutral lipids. A monoclonal antibody (mAb) specific for the neuroectoderma antigen disialoganglioside GD(2), has been covalently coupled to their external surface. The resulting anti-GD(2)-targeted CCLs showed high loading efficiency for the asODNs, small particle size and good stability. In vitro, they were able to deliver myb-asODNs selectively to GD(2)-positive NB cell lines more efficiently than non-targeted liposomes or free asODNs. Consequently, targeted formulations showed greater inhibition of cell proliferation than non-targeted formulations or free asODNs. Furthermore, we demonstrated that the inhibition of cell proliferation was dependent on the down-modulation of c-myb protein expression. Pharmacokinetic studies showed that these targeted liposomal formulations were long circulating in blood. Biodistribution studies presented differences between the free and the encapsulated myb-as ODN profiles, as well. While free myb-as ODNs are widely distributed (mainly liver, kidney and spleen) even after 30 min post-injection, myb-as ODN entrapped into CCL or anti-GD(2)-CCL presents only an accumulation in the spleen after 24 h. Future studies will be performed to evaluate the antitumour efficacy of the above formulations in animal models.

Antibodies, Monoclonal↗

Targeted delivery of antisense DNA in woodchuck hepatitis virus-infected woodchucks.

An asialoglycoprotein-based DNA delivery system containing an antisense oligo DNA against the polyadenylation region and adjacent upstream sequences of woodchuck hepatitis virus (WHV) was prepared. Experimental woodchucks were inoculated neonatally with the woodchuck virus 23 weeks before initiating the study, and all animals subsequently developed hepatitis as evidenced by the presence of measurable levels of circulating viral DNA. Animals were injected intravenously (i.v.) with asialoorosomucoid (AsOR)-poly-L-lysine complexes containing 0.1 mg kg-1 antisense DNA for five consecutive days. Levels of surface antigen did not differ substantially between treated and control animals. However, intravenous administration of complexed antisense DNA significantly decreased viraemia, as shown by a five- to 10-fold decrease in circulating viral DNA 25 days post treatment. The decline lasted for at least 2 weeks, after which there was a gradual increase in DNA levels. Antisense DNA alone or a complex containing a random oligo DNA of the same size and linkage failed to have any significant effect on viral DNA levels. We conclude that antisense oligo DNA can be targeted to the liver in vivo, resulting in a substantial and prolonged decrease in viral DNA levels in WHV-infected woodchucks.

Animals↗

Eradication of large colon tumor xenografts by targeted delivery of maytansinoids.

The maytansinoid drug DM1 is 100- to 1000-fold more cytotoxic than anticancer drugs that are currently in clinical use. The immunoconjugate C242-DM1 was prepared by conjugating DM1 to the monoclonal antibody C242, which recognizes a mucin-type glycoprotein expressed to various extents by human colorectal cancers. C242-DM1 was found to be highly cytotoxic toward cultured colon cancer cells in an antigen-specific manner and showed remarkable antitumor efficacy in vivo. C242-DM1 cured mice bearing subcutaneous COLO 205 human colon tumor xenografts (tumor size at time of treatment 65-130 mm3), at doses that showed very little toxicity and were well below the maximum tolerated dose. C242-DM1 could even effect complete regressions or cures in animals with large (260- to 500-mm3) COLO 205 tumor xenografts. Further, C242-DM1 induced complete regressions of subcutaneous LoVo and HT-29 colon tumor xenografts that express the target antigen in a heterogeneous manner. C242-DM1 represents a new generation of immunoconjugates that may yet fulfill the promise of effective cancer therapy through antibody targeting of cytotoxic agents.

Animals↗

Development and characterization of emulsomes for sustained and targeted delivery of an antiviral agent to liver.

In this study we developed emulsomes, a novel lipoidal vesicular system with an internal solid fat core surrounded by a phospholipid bilayer. Plain emulsomal formulations composed of solid lipid (trilaurin or tristearin), cholesterol and soya phosphatidylcholine and stearylamine containing cationic emulsomes loaded with an antiviral drug (zidovudine) were prepared by a simple cast film method followed by sonication to produce emulsomes of nanometric size range. All different types of formulations were optimized for lipid ratios and characterized in-vitro for shape, morphology, size and in-vitro drug release profile. Emulsomal formulations displayed a sufficiently slow drug release profile (12-15% after 24 h). In-vivo organ distribution studies in rats demonstrated better uptake of emulsomal formulations by the liver cells. Further, a significantly higher (P < 0.05) liver concentration of drug was estimated over a period of 24 h for cationic emulsomes than for plain neutral emulsomes. We concluded that cationic emulsomes could fuse with the endosomal membrane due to charge-charge interaction and were released in the cytoplasm before lysosomal degradation and could sustain drug release over a prolonged period. The proposed cationic emulsome-based system showed excellent potential for intracellular hepatic targeting and the strategy could play a vital role in the effective treatment of life-threatening viral infections, such as hepatitis, HIV and Epstein-Barr virus infection.

Amines↗

Targeted delivery of human neurofibromin and c-Raf-1 mutants to the cytoplasmic membrane by use of the influenza virus hemagglutinin.

Mutants of human neurofibromin and c-Raf-1 genes were fused to the 3' end of the hemagglutinin (HA) gene of influenza A virus by oligonucleotide-directed polymerase chain reaction (PCR). The two resulting chimeric genes, HA (1-534)/NF1 (1441-1518) and HA (1-534)/Raf-1 (51-132) which we designated HN and HR, respectively, were cloned in a vaccinia virus expression vector (pTMI) under the control of a T7 RNA polymerase promoter. The clones were expressed in a monkey cell line (CV-1) and the resulting chimeric proteins analysed. We found that expression levels of the chimeric proteins were similar to that of wild-type HA protein. Comparative endoglycosidase treatment revealed that the expressed chimeric proteins HN and HR were processed as wild-type HA, and FACS-analysis showed that both chimeric expression products localised in the cell membrane as the wild-type control. HN and HR expressing cells showed similar fusogenic activity as CV-1 cells transfected with wild-type HA indicating the correct topology of the fusion inducing portion (HA) of these chimera in the membrane. These findings show that the influenza virus hemagglutinin (HA) is a suitable vehicle to target foreign proteins with therapeutical potential into the cell membrane. In this respect HN and HR could potentially be used to block the abnormal signals generated by particular proteins in the cell membrane that lead to cell transformation.

Animals↗

Selective occlusion of tumor blood vessels by targeted delivery of an antibody-photosensitizer conjugate.

The irregular vasculature and high interstitial pressure of solid tumors hinder the delivery of cytotoxic agents to cancer cells. As a consequence, the doses of chemotherapy necessary to achieve complete tumor eradication are associated with unacceptably high toxicities. The selective thrombosis of tumor blood vessels has been postulated as an alternative avenue for combating cancer, depriving tumors of nutrients and oxygen and causing an avalanche of tumor cell deaths. The human antibody L19, specific to the EDB domain of fibronectin, a marker of angiogenesis, is capable of selective in vivo localization around tumor blood vessels and is thus a suitable agent for delivering toxic payloads to the tumor neovasculature. Here we show that a chemical conjugate of the L19 antibody with the photosensitizer bis(triethanolamine)Sn(IV) chlorin e(6), after intravenous injection and irradiation with red light, caused an arrest of tumor growth in mice with subcutaneous tumors. By contrast, a photosensitizer conjugate obtained with an antibody of identical pharmacokinetic properties but irrelevant specificity did not exhibit a significant therapeutic effect. These results confirm that vascular targeting strategies, aimed at the selective occlusion/disruption of tumor blood vessels, have a significant anticancer therapeutic potential and encourage the use of antibody-photosensitizer conjugates for the therapy of superficial tumors and possibly other angiogenesis-related pathologies.

Adenocarcinoma↗

Targeted delivery of anti-CTLA-4 antibody downregulates T cell function in vitro and in vivo.

CTLA-4 is a T cell surface molecule that binds to the costimulatory molecules CD80 and CD86 on antigen-presenting cells and downregulates T cell function. Therefore, we wanted to test whether antigen-specific activated T cells could be inhibited through directed CTLA-4 signaling using a bispecific antibody (BiAb) capable of simultaneously binding to CTLA-4 and a tissue-specific antigen. The BiAb was prepared by linking two separate monoclonal antibodies against CTLA-4 and the thyroid-stimulating hormone receptor (TSHR). The mouse B cell lymphoma line M12 (H2(d)) was used to induce alloreactive T cells in CBA/J mice (H2(k)); M12 cells stably transfected with the cDNA encoding murine TSHR (mM12) were used to restimulate the alloresponse in vitro. Results of assays for in vitro T cell proliferation, IL-2 production, and cytotoxicity in the presence of BiAb demonstrated that the BiAb could inhibit the T cell alloresponse when stimulated with mM12 cells but not with M12 cells. This effect was dependent on binding of TSHR-bound BiAb to CTLA-4, since the addition of soluble CTLA-4-Ig blocked the inhibitory effect. Injection of mM12 cells, along with the BiAb, not with antibodies against TSHR or CTLA-4 either separately or together, into CBA/J mice (H2(k)) downregulated alloreactive T cell responses. Our study demonstrated that the presence of CTLA-4 signaling molecules on the surface of target cells can protect those cells from immune attack by antigen-specific T cells and suggested that a similar approach could have potential therapeutic value in transplant rejection and tissue-specific autoimmune diseases.

Abatacept↗

Targeting delivery of paclitaxel into tumor cells via somatostatin receptor endocytosis.

BACKGROUND: The binding of somatostatin (SST) to endogenous G-protein-coupled receptors (SST receptors or SSTRs) is followed by internalization of SST, and, several reports have shown that a high density of SSTRs is present on most hormone-secreting tissue tumors. Facile synthesis of the long-acting SST analog, octreotide, has previously been described. Octreotide might be of practical value in developing tumor tracers and in serving as a carrier of cytotoxic antitumor drugs. RESULTS: Fluorescein-labeled octreotide was internalized into the cytosol of human breast MCF-7 carcinoma cells via binding to SSTRs. Octreotide-conjugated paclitaxel (taxol) was created by coupling taxol-succinate to the amino-terminal end of octreotide. This conjugate retains the biological activity of taxol in inducing formation of tubulin bundles, eventually causing apoptosis of MCF-7 cells. Cytotoxicity of octreotide-conjugated taxol is mainly mediated by SSTR, as shown by the observation that octreotide pretreatment can rescue the induced cell death. In comparison with free taxol, this conjugate shows much less toxicity in Chinese hamster ovary cells. CONCLUSIONS: Octreotide-conjugated taxol exerts the same antitumor effect of free taxol on stabilizing microtubule formation and inducing cell death. This conjugate triggers tumor cell apoptosis mediated by SSTRs and is exclusively toxic to SSTR-expressing cells. Octreotide-conjugated taxol is less toxic to low-SSTR-expressing cells compared with free taxol. Our results strongly indicated that octreotide-conjugated taxol demonstrates cell selectivity and may be used as a targeting agent for cancer therapy.

Animals↗