KB tumor cells exhibit an increased number of folate receptors on their membrane. This receptor has been proposed as a promising target for tumor drug targeting. Therefore, the disposition of folate-conjugated bovine serum albumin (folate-BSA) was examined as a model system for drug targeting. Nude mice which had received KB tumor cell transplants were given bolus intravenous administration of either 111In-labeled folate-BSA (111In-folate-BSA; 1 mg/kg) or unmodified 111In-BSA (111In-BSA; 1 mg/kg). The disposition characteristics and pharmacokinetics of 111In-folate-BSA were compared with those of the 111In-BSA as a control. The half-life of the beta-phase of 111ln-folate-BSA in plasma was 140 min. The tumor uptake rate index for 111In-folate-BSA was 0.46 microL/min/g, and that for 111In-BSA was 0.32 microL/min/g. This index of 111In-folate-BSA was slightly higher than that of 111In-BSA in vivo, by a factor of 1.4. In vivo experiments showed folate-BSA has a relatively long plasma duration. 111In-folate-BSA also showed selective distribution to tumors, but not as great as recent results from in vitro experiments. Therefore, the low vascular permeability of BSA into solid tumor tissue and inhibition of folate-mediated 111In-folate-BSA uptake by tumor cells from the blood may be the rate-limiting factor of distribution.

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The purpose of this study was to investigate stable complexation of drug in blood by sugar-branched-beta-cyclodextrins (beta-CDs) such as glucose (glu)- or galactose (gal)-branched-beta-CDs and the pharmacokinetic disposition of drug in sugar-branched-beta-CD complex. Complexation of steroidal drugs in sugar-branched-beta-CDs and their replacement by cholesterol were measured. The complexes of dexamethasone/glucosyl-beta-CDs (dexamethasone/glu-beta-CD or dexamethasone/glu-glu-beta-CD) were not replaced by cholesterol, which is a representative endogenous compound, whereas the complex of dexamethasone/beta-CD was replaced by cholesterol. The same results were obtained in steroidal drugs such as hydrocortisone, triamcinolone, and prednisolone. Thus, the use of glu-beta-CD and glu-glu-beta-CD permitted the stable complexation of the drug in water. Stability constants of dexamethasone/glu-glu-beta-CD and dexamethasone/gal-glu-beta-CD complexes are the same, which means that the sugar moiety of the side chain in beta-CD has little effect on stability constants. After the dexamethasone/gal-glu-beta-CD complex or the dexamethasone/glu-glu-beta-CD complex (dexamethasone: 1 mg/body) was administered intravenously to mice, dexamethasone concentrations in liver tissue and blood were measured. The dexamethasone/gal-glu-beta-CD complex (66.1 +/- 1.7 micrograms as dexamethasone/gram of liver tissue) was distributed to liver tissue significantly more than the dexamethasone/glu-glu-beta-CD (beta-CD) complex (59.9 +/- 1.0 micrograms as dexamethasone/gram of liver) at 30 min after administration (p < .05). Sugar-branched-beta-CD gave a water-soluble and stable complex for dexamethasone and changed the disposition of dexamethasone. Sugar-branched-beta-CDs are potentially excellent carriers for a steroidal injectable formulation.

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