• Biomolecules & Therapeutics
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• v.1 no.2
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• pp.125-130
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• 1993

The araC prodrugs (1~5) carrying a special acyl group at 5'-Ο-or $N^4$-position were evaluated for in vitro antiviral activity against various human viruses. When tested against HSV-1 and HSV-2 cultured in the verso cells, the prodrugs exhibited slightly higher $ED_{50}$ values compared with one of the parent araC but showed more increased $CC_{50}$ values in all cases. Consequently the overall selectivity indexes of prodrugs were higher than that of arab. The prodrugs, except compound 5, exhibited very potent activity similar to that of araC ($ED_{50}$ about $0.12{\mu}g/mι$) when evaluated against another human DNA virus, cytomegarovirus. However, theses araC prodrugs were completely inactive against RNA viruses i.e. poliovirus and coxackie B3 virus at the concentration of 4250{\mu}g/mι.$

• Journal of Pharmaceutical Investigation
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• v.31 no.2
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• pp.95-100
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• 2001

Various alkyl ester prodrugs of diclofenac were synthesized in order to investigate the relationship between their skin permeation characteristics and physicochemical properties. Solubility in various vehicles was measured at room temperature. 1-Octanol/water partition coefficients (Log P) and capacity factors (k') were measured to determine the lipophilicity of the prodrugs. Stability of prodrugs in the skin extract and homogenate was also investigated before conducting the skin permeation studies. Increases in the Log P and capacity factor values were observed when alkyl esters of diclofenac were prepared. Since the aqueous solubility of the prodrugs was not high enough, they were saturated in propylene glycol (PG) for skin permeation studies. Prodrugs were rapidly metabolized to diclofenac, both in skin homogenate and in dermal extract of skin. The skin permeation rate of alkyl ester prodrugs was significantly higher than diclofenac with shorter lag time. Moreover, a parabolic relationship was observed between the permeation rate and the log P values of prodrugs, and the maximum flux was achieved at a log P value of around 4.0.

• Journal of Pharmaceutical Investigation
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• v.21 no.2
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• pp.103-110
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• 1991

Two new prodrugs of lonazolac, lonazolac acetic acid ester and lonazolac argininate, were prepared and examined for physicochemical properties and biopharmaceutical characteristics. The prodrugs were stable in solid state and lonazolac argininate showed higher dissolution rate than lonazolacca in both artificial gastric and intestinal juices. These prodrugs have higher analgegic effect than that of lonazolac-Ca in mice, and increased anti-inflammatory activities in rats. In addition, ulcerogenic effects and acute toxicity of these prodrugs were lower than those of lonaaolac-Ca. Lonazolac acetic acid ester showed larger area under the plasma concentration-time curves (AUC) than that of lonazolac. Therefore, it was suggested that these prodrugs of lonazolac have advantages over lonzolac-Ca for not only enhanced bioavailability but also decreased ulcerogenic and toxic effects.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.405-412
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• 2008

Six ester analogues of Ketorolac were synthesized as potential enhancer prodrugs for transdermal delivery. Solubility of these esters was determined in 10% propylene glycol (PG)/isotonic phosphate buffer (IPB) at room temperature while lipophilicity was obtained as partition coefficients (log P) and capacity factors (k') using HPLC. Stability of the prodrugs in skin extract and in plasma was investigated at $37^{\circ}C$. The lipophilicity of the potential prodrugs increased in proportion to their alkyl chain length. Good linear relationship between partition coefficients (log P) and capacity factors (log k') was observed ($R^2=0.9961$). All of the analogues were fairly stable but slowly degraded in IPB over a 12 hour period. However, their stability in skin extract and in plasma varied with most compounds gradually decomposing over a 12 hour period. Although unsaturation of the alkyl ester chain did not alter the over all lipophilicity of the compound, the half-life was significantly affected. In plasma, degradation of the esters was slower than in the skin extract, which is a desirable trait for enhancer-prodrugs. However, the overall hydrolysis in the skin extract needs to be facilitated for the development of an effective enhancer prodrug. The analogue with the shortest half life in the skin extract was the unsaturated C-12 analogue of 0.96 hr.

• Macromolecular Research
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• v.12 no.1
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• pp.71-77
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• 2004

We have synthesized various types of poly(ethylene glycol) (PEG)-ibuprofen conjugates by nucleophilic substitution of bromo-terminated PEG with ibuprofen-Cs salt. The conversion of the terminal hydroxyl groups to bromo-termini was quantitative, as was the drug conjugation process, which suggests that the present synthetic method is very useful for the preparation of PEG-based prodrugs from pharmaceuticals having carboxyl functionalities. The drug-release behavior of the prodrugs was examined in both phosphate buffer (PBS, pH 7.4) and rat plasma. From the drug-release behavior in PBS, we determined that each prodrug has high storage stability. The drug-release rate was observed to be much faster in rat plasma than in buffer solution as a result of the acceleration effect provided by enzymes present in the plasma. The drug-release rate in rat plasma depends on the degree of molecular aggregation of the prodrugs, which can be changed effectively by the nature of their spacer groups or by the use of Pluronic as the polymer carrier.

• YAKHAK HOEJI
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• v.40 no.5
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• pp.522-531
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• 1996

5-fluorouracil(5-FU) derivatives synthesized with four N-acyloxycarbonyl group such as 1-(N-t-butyloxycarbonyl)glycyloxymethyl-5-FU(BGFU), 1-(N-t-butyloxycarbonyl)leucyloxymethy l-5-FU(BLFU), 1-(N-t-carbobenzyloxymethyl)glycyoxymethyl-5-FU(CGFU) and 1-(N-t-carbobenzyloxymethyl)leucyloxymethyl-5-FU(CLFU) were entrapped into liposomes with different lipid compositions. The entrapment efficiency and release rate of drugs from each liposomes were evaluated. The particle size of liposomes, cytotoxicity and stability of drug-entrapped in liposomes were evaluated. The entrapment efficiency in 5-FU derivatives liposomes was dependent on the lipophilicity of N-acyloxymethyl derivatives. The drug entrapment efficiency also increased on the content of lipid increased up to 200mcmol of lipid per milliliter of liposomal solution. However, inclusion of additives such as cholesterol, dicetylphosphate and stearylamine decreased the entrapment efficiency. The mean particle size and size distribution were varied with lipid compositions and lipophilicity of prodrugs. The release rates of drugs from liposomes were not affected by additives, but those of BGFU and CGFU entrapped in liposomes with cholesterol decreased. Cytotoxicity of BLFU and CLFU entrapped in liposomes decreased by 3~5 fold compared with those of free two prodrugs. Liposome-entrapped 5-FU prodrugs were more stable either at pH 7.4 or in human plasma. Especially, 5-FU prodrugs entrapped in liposome with dipalmitoylphosphatidylcholine(DMPC) was the most stable in human plasma. Compared with free BLFU, BLFU entrapped in DMPC liposome showed a superior antitumor activity at all doses used. In contrast, CLFU entapped in liposomes were more toxic than free prodrug.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.484-493
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• 2007

Two polymeric prodrugs of PGE1 (prodrugs IVg and PNg) were newly synthesized. The drug conjugation proceeded in quantitative yield without decomposition of PGE1 to PGA1. With two types conjugates, PEG-PGE1 and PN-PGE1 with different spacer groups, we first discovered a possibility of slow release of PGE1 in blood circulatory system. PGE1 is conjugated with PEG and PN through the long alkylene spacers, and their availability as polymeric prodrugs is evaluated. Their drug-releasing behavior was examined both in phosphate buffer (pH=7.4) and rat plasma. Each prodrug was known to be highly stabile in the buffer solution. The drug-releasing rate became much faster in rat plasma than in the buffer solution due to the acceleration by the plasma enzymes. The drug-release was found to reach a plateau in rat plasma because the released PGE1 or its derivatives may be captured or decomposed by the plasma proteins. The slower drug-releasing rate of pro drug PNg in rat plasma is reasonably attributed to the molecular aggregation due to the hydrophobic bonding between the PGE1 moieties and spacers.

• YAKHAK HOEJI
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• v.40 no.5
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• pp.532-538
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• 1996

In cancer chemotherapy, it is necessary to control the phamacokinetic behavior of an antitumor drug for effective treatment. Therefore, two 5-fluorouracil derivatives synthesize d with N-a-cyloxycarbonyl derivatives {1-(N-t-butyloxycarbonyl)leucyloxymethyl-5-FU(BLFU) and 1-(N-t-carbobenzyloxymethyl)leucyloxymethyl-5-FU(CLFU)}. prodrugs of 5-fluorouracil, antitumor agent, were loaded into liposome of different lipid compositions. After liposomal drugs were injected intramuscularly, their pharmacokinetics and tissue distribution were assessed. The $AUC_{0{\to}{\infty}$ values were 1.29, 72.50, 85.57, 66.40 and 103.60${\mu}$g.hr/ml for 5-FU, BLFU, CLFU, BLFU- and CLFU-loaded liposome, respectively. 5-FU was distributed to spleen and liver with a maximal concentration after 1 hr and eliminated after 24 hr. But both prodrugs and dimyristoylphosphatidylcholine liposome entrapped prodrugs were distributed to spleen and liver at a lower concentration but maintained for a long time with a relatively high concentration in lung. Especially, liposome-entrapped CLFU was distributed to lung with a maximal concentration after 1 hr and redistributed to spleen increasingly, while the concentration of liposome-entrapped BLFU in lung reached a maximal level after 12 hr.

• YAKHAK HOEJI
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• v.26 no.2
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• pp.91-96
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• 1982

In an attempt to design prodrugs for the Derivatives of the Isothiocyanates R-N=C=S were synthesized eleven novel bis-dithiocarbamates. The best way of preparing the dithiocarbamates was the formation of the dithiocarbonates followed by the reaction of the dithiocarbonates with amines. Thus, the treatment of the diols with carbon disulfide in the presense of potassium hydroxide afforded the potassium salts of the ditniocarbonic acids. The potassium salts were then reacted with alkyl halides to give the dithiocarbonates, which upon treatment with amines produces the dithiocarbamates. In case of vicinal diol (n=o in the above formula), only one of the hydroxy groups was reacted to give the mono-dithiocarbonate. The dithiocarbonates failed to react with amides and aromatic amines. Dithiocarbonates of the different types were obtained when the active double bonds, such as $CH_{2}=CH-Z$ , (Z are electron withdrawing groups), were allowed to react with the free dithiocarbonic acids produced in situ by carefully neutralizing the Potassium salts of the corresponding acids. These compounds are considered to be of some value as prodrugs for the active double bonds.

• Archives of Pharmacal Research
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• v.26 no.10
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• pp.785-795
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• 2003

For the development of new anticonvulsive agents, GABAmimetics such as nipecotic acid, isonipecotic acid, ${\gamma}-aminobutyric$ acid (GABA), ${\gamma}-vinyl$ GABA (vigabatrin) and valproic acid were covalently coupled through an ester bond by a two-carbon linker chain as potential prodrugs and evaluated for their anticonvulsive activities.