Vol. 288, Issue 2, 888-897, February 1999

Specific Renal Delivery of Sugar-Modified Low-Molecular-Weight Peptides

Kokichi Suzuki¹ , Hiroshi Susaki² , Satoshi Okuno³ , Harutami Yamada³ , Hiroshi K. Watanabe¹ and Yuichi Sugiyama

Drug Delivery System Institute, Ltd., Noda-shi, Chiba, Japan (K.S., H.S., S.O., H.Y., H.W.); and Faculty of Pharmaceutical Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan (Y.S.)

To develop a novel delivery system for peptides involving sugar modification, Arg-vasopressin (AVP) was modified by linking it to a variety of sugars via an octamethylene group and the subsequent tissue uptake by rats was then monitored after administration by i.v. injection. The glucosyl, mannosyl, and 2-deoxyglucosyl derivatives of AVP exhibited selective renal uptake. These derivatives were found to be distributed in the proximal tubules of the renal cortex. In addition, they exhibited specific binding to the kidney microsomal fraction in vitro (K_d = ~60 nM), suggesting that they are taken up by a specific recognition mechanism located in the kidneys. From the results of the uptake study of glucosyl derivatives, the following points are clear: 1) renal uptake in vivo becomes saturated with increasing dose, and the K_m from the uptake study is almost the same as the K_d obtained in the binding assay in vitro and 2) because the renal first-pass uptake extraction is about 70% at a low dose (10 nmol/kg), there is an effective mechanism for uptake from blood. Furthermore, glucosyl and mannosyl derivatives of oxytocin, a neutral peptide, unlike AVP that is basic, also have high renal uptake clearances. Thus, the renal uptake may not be dependent on derivatives having a cationic nature. We conclude that there is a novel transport mechanism in the kidneys that can be used for the specific renal delivery of glycosylated peptides.