A NOVEL DIMERIC FLUOROPYRIMIDINE MOLECULE BEHAVES AS A REMOTE PRECURSOR OF 5-FLUORO-2'-DEOXYURIDINE IN HUMAN ERYTHROCYTES

A new dimeric fluoropyrimidine molecule xyuridilyl-(5'-->3')-5-fluoro- 2'-deoxy-5'-uridylic acid, Compound 1) was chemically synthesized from two separately deblocked 5-fluoro-2'-deoxyuridine mononucleotide moie ties. Other structurally related nucleotides, 5-fluoro-2'-deoxyuridine -5'diphosphate (FdUDP), 5-fluoro-2'-deoxyuridine-5'-triphosphate (FdUT P) and 5-fluoro-2'-deoxyuridine-3'5'-bisphosphate were also synthesize d. The structures of all synthesized molecules were verified by mas sp ectrometric analyses and were consistent with expected molecular mass values. The metabolic patterns of conversion of Compound 1 were invest igated both in human erythrocyte lysates and in intact erythrocytes pr eviously loaded with this molecule according to a highly conservative encapsulation procedure. In hemolysates, Compound 1 was transformed to 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP). In intact red cell s, Compound 1 still generated FUdR (and to a lesser extend FU), that w as then released outside. The conversion pathway involves a phosphodie sterase-catalysed hydrolysis of Compound 1 into two FdUMP molecules, f ollowed by further dephosphorylation to FUdR and by partial conversion to FU. Unlike hemolysates, Compound 1-loaded intact erythrocytes feat ured transient formation of FdUDP and FdUTP, both metabolites represen ting storage compounds for the final and sustained production of FUdR and FU. Therefore, human erythrocytes can behave as bioreactors ensuri ng the time-controled production and delivery of the two powerful anti tumor drugs FUdR and FU from encapsulated Compound 1. This new molecul e and other compounds as well (e.g. FdUDP and FdUTP) can be viewed as useful pre-prodrugs, exploitable for intraerythrocytic bioconversion r eactions.