Aim:To evaluate the pharmacokinetic characteristics of L-valyl-ara-C,apeptidomimetic prodrug of ara-C.Methods:After the synthesis of L-valyl-ara-C,the in vitro stability of L-valyl-ara-C was examined in various biological media.Plasma pharmacokinetic profiles of ara-C and L-valyl-ara-C were also evaluated inrats.Results:The degradation of L-valyl-ara-C was negligible in fresh plasmaand also in the presence of plasmin over a 2 h incubation period.Furthermore,L-valyl-ara-C appeared to be stable in the leukemia cell homogenates,andsubsequently,it was far less cytotoxic than the parent,ara-C in AML2 and L1210cells.The chemical hydrolysis of L-valyl-ara-C was rather accelerated in acidicpH.Following an oral administration of L-valyl-ara-C,the appearance of ara-Cwas observed in plasma although the systemic exposure of the prodrug was muchhigher than that of ara-C.The bioavailability of ara-C was about 4% via prodrugadministration.Conclusion:The amide bond of L-valyl-ara-C was stable againstthe enzymatic hydrolysis,and the utility of L-valyl-ara-C as an oral delivery sys-tem of ara-C appeared to be limited by its low metabolic conversion to ara-C in rats. Aim: To evaluate the pharmacokinetic characteristics of L-valyl-ara-C, apeptidomimetic prodrug of ara-C. Methods: After the synthesis of L-valyl-ara-C, the in vitro stability of L-valyl-ara-C was examined in various biological media. Plasma pharmacokinetic profiles of ara-C and L-valyl-ara-C were also evaluated in rheologies. Results: The degradation of L-valyl-ara-C was negligible in fresh plasma and also in the presence of plasmin over a 2 h incubation period. Future Thermo, L-valyl-ara-C was found to be stable in the leukemia cell homogenates, and the results were very less cytotoxic than the parent, ara-C in AML2 and L1210 cells. The chemical hydrolysis of L- valyl-ara-C was rather accelerated in acidic pH. Following an oral administration of L-valyl-ara-C, the appearance of ara-Cwas observed in plasma although the systemic exposure of the prodrug was muchhigher than that of ara-C.The bioavailability of ara-C was about 4% via prodrugadministration.Conclusion: The amide bond of L-valyl-ara-C was stable againstt he enzymatic hydrolysis, and the utility of L-valyl-ara-C as an oral delivery sys-tem of ara-C was to be limited by its low metabolic conversion to ara-C in rats.