Song Wha Chae

A novel micelle-encapsulated platinum(II) anticancer agent

A hydrophobic and water-insoluble platinum(II) compound, cis-(cha)(2)Pt(NO(3))(2) was encapsulated by macromolecular micelles self-assembled from an amphiphilic cyclotriphosphazene [NP(MPEG750)(GlyPheLeu)(2)Et](3) (CP750). The micelle-encapsulated platinum(II) compound exhibited outstanding pharmacokinetics in rats by showing long blood circulation and much larger systemic exposure (AUC=43.5 μgh/ml) compared with the free carboplatin (AUC=4.32 μgh/ml). Biodistribution study of the micellar platinum(II) compound using male Sprague-Dawley rats has shown excellent tumor to tissue ratios of 4.03 at 2h post injection and 4.67 at 24h post injection. Furthermore, the micellar platinum(II) compound exhibited more than 6 times higher cellular uptake in human cervical (HeLa) and lung (A549) tumor cells compared with the free platinum compound. Also it is surprising that the micellar platinum(II) compound displayed specifically high cytotoxicity against the stomach tumor cells (SNU638), which are one of the least responsive to chemotherapeutic agents currently in clinical use. The acute toxicity study has shown that the LD(50) values of free and the micellar cis-(cha)(2)Pt(NO(3))(2) are approximately 70 mg/kg and 90 mg/kg, respectively. Thus the platinum compound encapsulated by cyclotriphosphazene micelles is a promising candidate for preclinical studies.

Stable and efficient delivery of docetaxel by micelle-encapsulation using a tripodal cyclotriphosphazene amphiphile

Docetaxel micelle-encapsulated by a tripodal cyclotriphosphazene amphiphilile [NP(PEG750)(GlyPheLeu)(2)Et](3) (CP750) exhibited outstanding drug-loaded micelle stability in aqueous solution compared with the polymeric micelles assembled from linear block copolymers. Furthermore, docetaxel micelle-encapsulated by CP750 is obtainable in solvent free powder form, which is immediately soluble in any aqueous media including saline and PBS and very stable to photo-degradation even in the room light at room temperature. Although docetaxel micelle-encapsulated by CP750 did not display highly improved pharmacokinetic profile compared with Taxotere currently in clinical use, its in vivo xenograft trials exhibited excellent antitumor efficacy by showing complete tumor regression against the breast cancer cells (MDA-MB-231) at a lower dose of 5mg/kg and better efficacy against gastric cancer cells (MKN-28) compared with Taxotere. Furthermore, according to the comparative acute toxicity study, toxicities associated with Taxotere may be remarkably reduced by micelle-encapsulation of docetaxel using CP750, which afforded a much higher LD(50) value of 75 mg/kg compared with 28 mg/kg of docetaxel in Taxotere. Thus docetaxel micelle-encapsulated by CP750 has entered the stage of preclinical studies.

Tripodal amphiphiles tunable for self-assembly to polymersomes

Cyclotriphosphazenes grafted with equimolar amounts of a hydrophilic polyethylene glycol and a hydrophobic oligopeptide in cis-nongeminal way form a new class of tripodal amphiphiles allowing both intra- and intermolecular hydrophobic interactions that differ from linear block copolymer amphiphiles. It has been found in this study that the tripodal amphiphiles can be tuned for self-assembly from micelles to bilayered polymersomes by controlling the hydrophobicity of the oligopeptide grafted. For instance, the tripodal amphiphiles with an intermediate hydrophobicity (0<log P<1) (P=[solute](n-octanol)/[solute](water)) reassemble from initially formed micelles into polymersomes, whereas the trimers bearing highly hydrophobic oligopeptides (log P>1) remain as stable micelles in aqueous solution. These biodegradable polymersomes exhibit outstanding physicochemical properties required for practical drug delivery and other biomedical applications. In particular, the cyclic phosphazene trimer platinated with a hydrophobic cis-bis(cyclohexylamine)Pt-moiety forms very stable polymersomes with excellent tumor selectivity by EPR effect and seems to be a promising candidate for preclinical studies.

Nonviral gene delivery to human ovarian cancer cells using arginine-grafted PAMAM dendrimer

Background: A specific and effective strategy is in demand to treat ovarian cancer successfully. Epidermal growth factor receptor (EGFR) is highly expressed in ovarian cancer, and thus EGFR antisense gene therapy can be a potential therapeutic strategy. Method: l-Arginine-grafted-polyamidoamine dendrimer (PAMAM-Arg) has been reported to be a novel nonviral gene delivery carrier. Therefore, the ability of PAMAM-Arg in transferring a luciferase gene to ovarian carcinoma SK-OV3 cells has been examined, and the cytotoxicity of the cationic polymer has been investigated. In addition, the suppression of cell proliferation has been evaluated by transferring an EGFR antisense gene to SK-OV3 cells using PAMAM-Arg. Polyethyleneimine (PEI) 25K was used as a positive control. Results: As a result, in vitro gene transfection efficiency of PAMAM-Arg was enhanced with increasing transfection time and N/P ratios. PAMAM-Arg transferred the luciferase gene into cells more efficiently than PEI. In addition, PAMAM-Arg was minimally toxic to the cells whereas PEI 25K was highly toxic. The polyplexes formed by the EGFR antisense gene and PAMAM-Arg significantly reduced thymidine incorporation into the cells suggesting the suppression of cancer cell proliferation. Conclusion: These results suggest that a PAMAM-Arg/EGFR antisense gene complex can be used as a safe and efficient therapeutic agent for cancer gene therapy.

Xanthone analogues as potent modulators of intestinal P-glycoprotein

Intestinal P-glycoprotein (P-gp) is a limiting step for oral absorption of drugs. Therefore, P-gp inhibitors have been studied as enhancers of oral absorption of drugs that are P-gp substrates. We investigated the in vitro and in vivo P-gp inhibitory activity of synthesized xanthone analogues. With 3-(3-chloro-2-hydroxypropoxy)-1-hydroxy-9H-thioxanthen-9-one, compound 13, accumulation of daunomycin (DNM) increased 707% and efflux of DNM decreased 66% compared to DNM alone. Relative bioavailability (RB) of paclitaxel (PTX, 25 mg/kg) increased 2.5-fold after oral administration with 13 (5 mg/kg). In a xenograft animal model, oral administration of PTX (40 mg/kg) with 13 (10 mg/kg) significantly inhibited tumour growth and was more effective than intravenously administered PTX (10 mg/kg) alone. Therefore, the synthesized xanthone analogue 13 might have therapeutic benefits for oral absorption of P-gp substrate anticancer drugs.

Effect of coumarin derivative-mediated inhibition of P-glycoprotein on oral bioavailability and therapeutic efficacy of paclitaxel.

Since P-glycoprotein (P-gp) acts as a barrier to intestinal absorption of various drugs, P-gp inhibitors have been studied as oral absorption enhancers of P-gp substrate drugs. Here, we investigated the in vitro and in vivo effects of a novel coumarin derivative (LL-348) for its P-gp inhibitory activity. With LL-348, accumulation of daunomycin (DNM) increased 270% and efflux of DNM decreased 63% compared to that of DNM alone. Paclitaxel (PTX, 25mg/kg) after oral administration with LL-348 (5mg/kg), the optimal dose of LL-348 as an oral absorption enhancer of PTX, improved the relative bioavailability (RB) of PTX to 961%. In a xenograft animal model, PTX (40mg/kg) treated with LL-348 (10mg/kg) significantly increased the efficacy of PTX. The results collectively demonstrate that LL-348 can provide a therapeutic benefit in the oral absorption of P-gp substrate anticancer drugs.

Simple determination of azasetron in rat plasma by column‐switching high‐performance liquid chromatography

For the quantification of azasetron in rat plasma samples, a column-switching HPLC method was developed and validated. Following dilution of plasma samples with mobile phase A (17 mM potassium phosphate buffer (pH 3.0)) and simple protein precipitation by addition of perchloric acid (60%), the mixture was directly injected onto the pre-column. After endogenous plasma substances were eluted to waste, the analyte was transferred to the trap column by switching the system. Then, the analyte was back-flushed to the analytical column for separation with mobile phase B (a 22:78 v/v mixture of acetonitrile and 17 mM potassium phosphate buffer (pH 3.0)) and detected at 250 nm using a photodiode array detector. A linear standard curve was obtained in the concentration range of 10-800 ng/mL with the correlation coefficient (r) of 0.9998. The intra- and inter-day precision and accuracy values for azasetron were in the ranges of 0.3-12.9% and 89.7-101.4%, respectively. The method was valid in terms of specificity, precision, and accuracy. In addition, this efficient analytical method was successfully applied to determine plasma concentrations of azasetron following oral administration of azasetron at a dose of 4.0 mg/kg to rats.

Effects of single or repeated silymarin administration on pharmacokinetics of risperidone and its major metabolite, 9-hydroxyrisperidone in rats

1. The interactions between herbal dietary supplements and therapeutic drugs have emerged as an important issue and P-glycoprotein (P-gp) has been reported as one of the significant factors of these interactions. 2. The objective of this article is to examine the effects of single and repeated administrations of silymarin on pharmacokinetics of a P-gp substrate, risperidone, and its major metabolite, 9-hydroxyrisperidone, in rats. 3. To determine the plasma levels of risperidone and 9-hydroxyrisperidone in rats, a HPLC method was developed using a liquid-liquid acid back extraction. When risperidone (6 mg/kg) was co-administered with silymarin (40 mg/kg) to rats orally, the Cmax of 9-hydroxyrisperidone was significantly increased to1.3-fold (p < 0.05), while the other pharmacokinetic parameters did not show any significant differences. Expanding the experiment where rats were repeatedly administered with silymarin for 5 days prior to giving risperidone, the Cmax of risperidone and 9-hydroxyrisperidone were significantly increased to 2.4-fold (p < 0.001) and 1.7-fold (p < 0.001), respectively, and the AUC0-t, as well to 1.7-fold (p < 0.05) and 2.1-fold (p < 0.01), respectively. 4. The repeated exposures of silymarin, compared to single administration of silymarin, increased oral bioavailability and affected the pharmacokinetics of risperidone and 9-hydroxyrisperidone, by inhibiting P-gp.

Intestinal P-glycoprotein inhibitors, benzoxanthone analogues

The inhibitors of P‐glycoprotein (P‐gp) which limits an access of exogenous compounds in the luminal membrane of the intestine have been studied to enhance the intestinal P‐gp‐mediated absorption of anticancer drugs.