Taishi Higashi

Folate-PEG-appended dendrimer conjugate with α-cyclodextrin as a novel cancer cell-selective siRNA delivery carrier.

We previously reported that of the various polyamidoamine (PAMAM) STARBURST dendrimer (generation 3, G3) (dendrimer) conjugates with cyclodextrins (CyDs), the dendrimer (G3) conjugate with α-CyD having an average degree of substitution of 2.4 (α-CDE (G3)) has the greatest potential for a novel carrier for siRNA in vitro and in vivo. To improve the siRNA transfer activity and the lack of target specificity of α-CDE (G3), we prepared folate-polyethylene glycol (PEG)-appended α-CDEs (G3) (Fol-PαCs) with various degrees of substitution of folate (DSF) and evaluated their siRNA transfer activity to folate receptor (FR)-overexpressing cancer cells in vitro and in vivo. Of the three Fol-PαCs (G3, DSF 2, 4 and 7), Fol-PαC (G3, DSF 4) had the highest siRNA transfer activity in KB cells (FR-positive). Fol-PαC (G3, DSF 4) was endocytosed into KB cells through FR. No cytotoxicity of the siRNA complex with Fol-PαC (G3, DSF 4) was observed in KB cells (FR-positive) or A549 cells (FR-negative) up to the charge ratio of 100/1 (carrier/siRNA). In addition, the siRNA complex with Fol-PαC (G3, DSF 4) showed neither interferon response nor inflammatory response. Importantly, the siRNA complex with Fol-PαC (G3, DSF 4) tended to show the in vivo RNAi effects after intratumoral injection and intravenous injection in tumor cells-bearing mice. The FITC-labeled siRNA and TRITC-labeled Fol-PαC (G3, DSF 4) were actually accumulated in tumor tissues after intravenous injection in the mice. In conclusion, the present results suggest that Fol-PαC (G3, DSF 4) could potentially be used as a FR-overexpressing cancer cell-selective siRNA delivery carrier in vitro and in vivo.

Design and evaluation of polypseudorotaxanes of pegylated insulin with cyclodextrins as sustained release system.

Supramolecular assemblies have attracted a great attention, due to their intriguing topologies and their application in various fields such as nanodevices, sensors, molecular switches, and drug delivery systems. In this study, we prepared the monosubstituted insulin with poly(ethylene glycol) (PEG, MW about 2200) and its cyclodextrin (CyD) polypseudorotaxanes. The pegylated insulin formed polypseudorotaxanes with alpha- and gamma-CyDs, by inserting one PEG chain in the alpha-CyD cavity and two PEG chains in the gamma-CyD cavity. The pegylated insulin/alpha- and gamma-CyD polypseudorotaxanes were less soluble in water and the release rate of the drug decreased in the order of drug alone>the gamma-CyD polypseudorotaxane>the alpha-CyD polypseudorotaxane. The plasma levels of the pegylated insulin after subcutaneous administration of the gamma-CyD polypseudorotaxane to rats were significantly prolonged, accompanying an increase in the area under plasma concentration-time curve, which was clearly reflected in the prolonged hypoglycemic effect. The results indicated that the pegylated insulin/CyD polypseudorotaxanes can work as a sustained drug release system, and the polypseudorotaxane formation with CyDs may be useful as a sustained drug delivery technique for other pegylated proteins and peptides.

Folate-appended β-cyclodextrin as a promising tumor targeting carrier for antitumor drugs in vitro and in vivo.

A large number of antitumor drug delivery carriers based on passive targeting and/or active targeting have been developed. However, encapsulation of antitumor drugs into these drug carriers is often complicated, and antitumor activities of these targeting systems are not satisfactory. In the present study, we first prepared heptakis-6-folic acid (FA)-appended β-cyclodextrin (β-CyD) possessing two caproic acids between FA and a β-CyD molecule as a spacer (Fol-c(2)-β-CyD) and evaluated the potential as a novel tumor targeting carrier for antitumor drugs through a complexation. Fol-c(2)-β-CyD formed an inclusion complex with doxorubicin (DOX) at a 1:1 molar ratio with a markedly high stability constant (>10(6) M(-1)). Cellular uptake of DOX was increased by the addition of Fol-c(2)-β-CyD in KB cells, a folate receptor-α (FR-α)-positive cell line. Additionally, Fol-c(2)-β-CyD increased in vitro antitumor activities of antitumor drugs such as DOX, vinblastine (VBL), and paclitaxel (PTX) in KB cells, but not in A549 cells, a FR-α-negative cell line. The complex of DOX with Fol-c(2)-β-CyD markedly increased antitumor activity of DOX, not only after intratumoral administration but also after intravenous administration to mice subcutaneously inoculated Colon-26 cells, a FR-α-positive cell line. These findings suggest that Fol-c(2)-β-CyD could be useful as a promising antitumor drug carrier.

Potential use of γ-cyclodextrin polypseudorotaxane hydrogels as an injectable sustained release system for insulin

The development of injectable hydrogels for protein delivery is a major challenge. In this study, insulin/alpha-cyclodextrin (alpha-CyD) and gamma-CyD polypseudorotaxane (PPRX) hydrogels were prepared through inclusion complexation between high molecular weight poly(ethylene glycol) (PEG) and CyDs. The alpha-CyD and gamma-CyD PPRX hydrogels were formed by inserting one PEG chain in the alpha-CyD cavity and two PEG chains in the gamma-CyD cavity. Insulin/CyD PPRX hydrogel formation was based on physical crosslinking induced by self-assembling without chemical crosslinking reagent. The supramolecular structures of insulin/CyD PPRX hydrogels were confirmed with (1)H nuclear magnetic resonance ((1)H NMR), X-ray diffraction, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The in vitro release study showed that the release rate of insulin from the CyDs PPRX hydrogels decreased in the order of gamma-CyD PPRX hydrogel>alpha-CyD PPRX hydrogel. This decrease was controlled by the addition of CyDs to the medium. The serum insulin level after subcutaneous administration of gamma-CyD PPRX hydrogel to rats was significantly prolonged, accompanying with an increase in the area under serum concentration-time curve, which was clearly reflected in the prolonged hypoglycemic effect. In conclusion, these results suggest the potential use of gamma-CyD PPRX hydrogel as an injectable sustained release system for insulin.

Potential use of lactosylated dendrimer (G3)/α-cyclodextrin conjugates as hepatocyte-specific siRNA carriers for the treatment of familial amyloidotic polyneuropathy

To reveal the potential use of lactosylated-dendrimer (G3) conjugates with α-cyclodextrin (Lac-α-CDE (G3)) as novel hepatocyte-specific siRNA carriers in order to treat transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP), we evaluated the RNAi effect of siRNA complexes with Lac-α-CDE (G3) both in vitro and in vivo. Herein, we targeted TTR gene expression because TTR-related FAP was often caused by amyloidogenic TTR (ATTR), which mainly expresses in hepatocytes. Lac-α-CDE (G3, average degree of substitution of lactose (DSL) 1.2)/siRNA complex had a potent RNAi effect against TTR gene expression through adequate physicochemical properties, asialoglycoprotein receptor (ASGP-R)-mediated cellular uptake, efficient endosomal escape and the delivery of the siRNA complex to cytoplasm, but not nucleus, with negligible cytotoxicity. Lac-α-CDE (G3, DSL 1.2)/siRNA complex had the potential to induce the in vivo RNAi effect after intravenous administration in the liver of mice. The blood chemistry values in the α-CDE (G3) and Lac-α-CDE (G3, DSL 1.2) systems were almost equivalent to those in the control system (5% mannitol solution). Taken together, these results suggest that Lac-α-CDE (G3, DSL 1.2) has the potential for a novel hepatocyte-selective siRNA carrier in vitro and in vivo, and has a possibility as a therapeutic tool for FAP to the liver transplantation.

Inhibitory effect of siRNA complexes with polyamidoamine dendrimer/α-cyclodextrin conjugate (generation 3, G3) on endogenous gene expression.

In the present study, we prepared the small interfering RNA (siRNA) complexes with polyamidoamine (PAMAM) dendrimer (G3) conjugate with α-cyclodextrin (α-CDE (G3)), and examined the physicochemical properties, serum resistance, in vitro RNAi effects on endogenous gene expression, cytotoxicity, interferon response, hemolytic activity, cellular association and intracellular distribution. In addition, these results were compared to the siRNA complexes with the commercial transfection reagents such as linear polyethyleneimine (PEI), Lipofectamine™2000 (L2) and RNAiFect™ (RF). α-CDE (G3) interacted with siRNA, and suppressed siRNA degradation by serum. The siRNA complex with α-CDE (G3) showed the potent RNAi effects against Lamin A/C and Fas expression with negligible cytotoxicity and hemolytic activity, compared to those of the transfection reagents in Colon-26-luc cells and NIH3T3-luc cells. Cell-death patterns induced by siRNA polyplexes with α-CDE (G3) and PEI were different from siRNA lipoplexes with L2 and RF. α-CDE (G3) delivered fluorescent-labeled siRNA to cytoplasm, not nucleus, after transfection in NIH3T3-luc cells. Taken together, α-CDE (G3) could be potentially used as a siRNA carrier to provide the RNAi effect on endogenous gene expression with negligible cytotoxicity.

Sugar-appended polyamidoamine dendrimer conjugates with cyclodextrins as cell-specific non-viral vectors

The widespread use of various cyclodextrin (CyD)-appended polymers and polyrotaxanes as gene carriers has been reported. Among the various polyamidoamine dendrimer (dendrimer) conjugates with CyDs (CDE), the dendrimer (G3) conjugate with α-CyD having an average degree of substitution (DS) of 2.4 (α-CDE (G3, DS 2)) displayed remarkable properties as DNA carriers. In an attempt to develop cell-specific gene transfer carriers, we prepared some sugar-appended α-CDEs, e.g. mannosylated, galactosylated, and lactosylated α-CDEs. In addition, PEGylated Lac-α-CDEs (G3) were prepared and evaluated as a hepatocyte-selective and serum-resistant gene transfer carrier. Moreover, PEGylated-α-CDE/CyD polypseudorotaxane systems for novel sustained DNA release system have been developed. Interestingly, glucronylglucosyl-β-cyclodextrin (GUG-β-CyD) conjugates with dendrimer (G2) (GUG-β-CDE (G2)) had superior gene transfer activity to α-CDE (G2), expecting a development of new series of sugar-appended CDEs over α-CDEs (G2). Collectively, sugar-appended α-CDEs have the potential as novel cell-specific and safe carriers for DNA.

Potential use of Folate-appended Methyl-β-Cyclodextrin as an Anticancer Agent

To obtain a tumor cell-selectivity of methyl-β-cyclodextrin (M-β-CyD), we newly synthesized folate-appended M-β-CyD (FA-M-β-CyD), and evaluated the potential of FA-M-β-CyD as a novel anticancer agent in vitro and in vivo. Potent antitumor activity and cellular association of FA-M-β-CyD were higher than those of M-β-CyD in KB cells, folate receptor (FR)-positive cells. FA-M-β-CyD drastically inhibited the tumor growth after intratumoral or intravenous injection to FR-positive Colon-26 cells-bearing mice. The antitumor activity of FA-M-β-CyD was comparable and superior to that of doxorubicin after both intratumoral and intravenous administrations, respectively, at the same dose, in the tumor-bearing mice. All of the tumor-bearing mice after an intravenous injection of FA-M-β-CyD survived for at least more than 140 days. Importantly, an intravenous administration of FA-M-β-CyD to tumor-bearing mice did not show any significant change in blood chemistry values. These results strongly suggest that FA-M-β-CyD has the potential as a novel anticancer agent.

Recent advances in cyclodextrin delivery techniques

Introduction: Active pharmaceutical ingredients (APIs) are evolving from low-molecular-weight drugs to peptide-, protein-, gene-, oligonucleotide- and cell-based drugs. Therefore, advanced pharmaceutical technologies are required to achieve manifestation of the drug efficacy, side effect reduction and the adequate dosage form design. Areas covered: In this review, the authors highlight the recent advances in drug delivery techniques utilizing cyclodextrins (CyDs), and cyclic oligosaccharides consisting of α-1,4-linked α-D-glucopyranose units, for various drugs described above. Especially, drug delivery system consisting of combination systems of CyDs and functional materials such as dendrimer, liposome and PEG are introduced. Furthermore, the utilities of CyDs as APIs have been also described. Expert opinion: To achieve the controlled release and/or targeting of low-molecular-weight drugs in systemic administration, the construction of novel CyDs and CyD the supramolecular system should be a useful approach because of the stable complexation of drugs with CyDs. In addition, the combination systems of CyDs and various carriers have the potential as advanced drug delivery systems for proteins and nucleic acids. Furthermore, CyDs have great potential as APIs for various diseases with few side effects, although the detailed mechanism, especially cellular uptake of CyDs, should be clarified.

Efficacy of 2-hydroxypropyl-β-cyclodextrin in Niemann-Pick disease type C model mice and its pharmacokinetic analysis in a patient with the disease

Niemann-Pick type C disease (NPC), an autosomal recessive lysosomal storage disorder, is an inherited disease characterized by the accumulation of intracellular unesterified cholesterol. A solubilizing agent of lipophilic compounds, 2-hydroxypropyl-β-cyclodextrin (HPBCD), is an attractive drug candidate against NPC disease. However, establishment of the optimum dosage of HPBCD remains to be determined. In this study, we evaluated the effective dosage of HPBCD in NPC model (Npc1(-/-)) mice, and determined serum HPBCD concentrations. Subcutaneous injection of 1000-4000 mg/kg HPBCD improved the lifespan of Npc1(-/-) mice. In addition, liver injury and cholesterol sequestration were significantly prevented by 4000 mg/kg HPBCD in Npc1(-/-) mice. Serum HPBCD concentrations, when treated at the effective dosages (1000-4000 mg/kg), were approximately 1200-2500 µg/mL at 0.5 h after subcutaneous injection, and blood HPBCD concentrations were immediately eliminated in Npc1(-/-) mice. Furthermore, we examined serum HPBCD concentrations when treated at 40000 mg (approximately 2500 mg/kg) in a patient with NPC. We observed that the effective concentration in the in vivo study using Npc1(-/-) mice was similar to that in the patient. In the patient, systemic clearance and the volume of distribution of HPBCD were in accordance with the glomerular filtration rate and extracellular fluid volume, respectively. These results could provide useful information for developing the optimal dosage regimen for HPBCD therapy when administered intravenously to NPC patients.