AZIDOTHYMIDINE HOMODINUCLEOTIDE-LOADED ERYTHROCYTES AS BIOREACTORS FOR SLOW DELIVERY OF THE ANTIRETROVIRAL DRUG AZIDOTHYMIDINE

A new Azidothymidine derivative, '-azido-2',3'-dideoxy-D-riboside)-5'- 5'-p(1)-p(2)- pyrophosphate (AZT(p2)AZT), was encapsulated in human er ythrocytes according to a conservative procedure of hypotonic shock-is otonic resealing and reannealing. Like in erythrocyte lysates suppleme nted with 1 mM ATP, intact red cells too were found to convert AZT(p2) AZT to 3'-Azido-3'-deoxythymidine which was then released linearly in plasma. The major metabolic pathway involved in this conversion was th e symmetrical hydrolysis of AZT(p2)AZT to yield two 3'-Azido-3'-deoxyt hymidine-5'-phosphate molecules which were then dephosphorylated to 3' -Azido-3'-deoxythymidine. At late times of incubation, also a limited asymmetrical hydrolysis of AZT(p2)AZT became apparent in the intact er ythrocytes, yielding 3'-Azido-3'-deoxythymidine-5'-diphosphate that wa s then converted to the triphosphorylated derivative. Therefore, eryth rocytes loaded with AZT(p2)AZT act ''in vitro'' as bioreactors ensurin g sustained and potentially useful release of 3'-Azido-3'-deoxythymidi ne. (C) 1996 Academic Press, Inc.