SYNTHESIS OF 2'-DEOXYURIDINE AND 5-FLUORO-2'-DEOXYURIDINE DERIVATIVESAND EVALUATION IN ANTIBODY TARGETING STUDIES

Derivatives of 2'-deoxyuridine and of the anticancer agent 5-fluoro-2' -deoxyuridine (FdUR) were linked indirectly via a human serum albumin carrier (HSA) to the murine antiosteosarcoma monoclonal antibody 791T/ 36. Starting from the 2'-deoxyuridines la and lb, the new nucleosides containing 5'-succinamic acid 7 and 5'-maleamic acid 8 spacers were sy nthesized from the key intermediate 5'-aminonucleoside 4, and the ribo furonamidobenzoic acid 13 from ribofuranuronic acid 10. These nucleosi des were linked via their spacer functionality to HSA. High molar subs titution ratios (MSR: moles of drug/mole of HSA) of 25-40 for these de rivative-HSA conjugates were achieved. All derivatives were less cytot oxic than the parent drug against both antigen positive osteogenic sar coma 791T and antigen negative bladder carcinoma T24 cell lines; no IC 50 was achieved with any derivative against 791T cells. The fluorodeox yuridine-HSA conjugates were then further linked via a stable thioethe r bond to the mouse monoclonal antibody 791T/36. The optimum fluorinat ed 5'-succinamic acid immunoconjugate exhibited an IC50 of 1 muM again st 791T and T24 cells, slightly better than that of fluorodeoxyuridine . The unconjugated derivative 7 was much less cytotoxic than immunocon jugate, with an IC50 of 62 muM on T24 cells, and failed to reach 50 % inhibition of 791T cell growth at 290 muM concentration. Derivative 7- HSA conjugate was 10-fold less cytotoxic than the immunoconjugate agai nst both cell lines. Immunoconjugates synthesized with the other 5-flu oro derivatives were unable to effect 50% inhibition of growth of cell lines. Nonfluorinated derivatives and their HSA conjugates and immuno conjugates exhibited no cytotoxicity.