Azidothymidine homodinucleotide-loaded erythrocytes as bioreactors for slow delivery of the antiretroviral drug azidothymidine

A new Azidothymidine derivative, di-(thymidine-3'-azido-2',3'-dideoxy-D-riboside)-5'-5'-p(1)-p(2)- pyrophosphate (AZT(p2)AZT), was encapsulated in human erythrocytes according to a conservative procedure of hypotonic shock-isotonic resealing and reannealing. Like in erythrocyte lysates supplemented 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 the symmetrical hydrolysis of AZT(p2)AZT to yield two 3'-Azido-3'-deoxythymidine-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 erythrocytes, yielding 3'-Azido-3'-deoxythymidine-5'-diphosphate that was then converted to the triphosphorylated derivative. Therefore, erythrocytes loaded with AZT(p2)AZT act ''in vitro'' as bioreactors ensuring sustained and potentially useful release of 3'-Azido-3'-deoxythymidine. (C) 1996 Academic Press, Inc.