title: 5-ethyl-2'-deoxyuridine, a modulator of both antitumour action and pharmacokinetics of 5-fluorouracil.
abstract: The aim of the present studies was to elucidate the effects and optimal modulatory conditions of 5-ethyl-2'-deoxyuridine (EtdUrd) on the antitumour efficacy, pharmacokinetics and catabolism of 5-fluorouracil (5-FU) on Colon-26 and Colon-38 murine tumours. HPLC and GC-MS techniques were used to measure the concentrations of 5-FU, dihydro-5-fluorouracil, EtdUrd, 5-ethyluracil and uridine in the plasma and that of 5-FU and 5-fluoro-2'-deoxyuridine monophosphate (FdUMP) in the tumours. It was shown that EtdUrd, given 1 h before 5-FU, selectively enhanced the antitumour action of 5-FU, without significantly increasing its toxic side-effects, thus resulting in an approximately three times higher therapeutic index. Pharmacokinetic studies revealed that 1 h after 400 mg/kg EtdUrd administration - i.e. at the time of 5-FU treatment - the plasma concentration of EtdUrd was 269 microM, and that of 5-ethyluracil, as the major metabolite of EtdUrd, was 421 microM. It is of interest that EtdUrd pretreatment did not change the maximal plasma concentration of 5-FU; however, the half-life of the terminal elimination increased from 114.5 min to 171.2 min and thus the mean residence time of 5-FU rose significantly (P < 0.05). After the combined treatment, the maximal concentration of dihydro-5-fluorouracil in the plasma decreased from 61.06 microM to 29.70 microM (P < 0.01). The intratumoral concentrations of 5-FU were 34%-158% higher 6-96 h after the combined treatment than after the single 5-FU treatment. EtdUrd also caused a moderate increase in the intratumoral level of FdUMP. It is noteworthy, that EtdUrd increased the endogenous uridine concentration in the plasma from 18 microM to a maximum of 249 microM, and the level remained high for longer than 6 h. The present studies indicate that EtdUrd enhances the therapeutic index of 5-FU by reducing the catabolism, prolonging the plasma and intratumoral concentrations of 5-FU and, at the same time, offering protection to normal organs by increasing the endogenous uridine level.
authors.affiliation: Department of Clinical Research, National Institute of Oncology, H-1525 Budapest, P.O.B. 21, Hungary. kralo@oncol.hu
authors.forename: J
authors.initials: J
authors.lastname: Kralovánszky
authors.forename: C
authors.initials: C
authors.lastname: Katona
authors.forename: A
authors.initials: A
authors.lastname: Jeney
authors.forename: E
authors.initials: E
authors.lastname: Pandi
authors.forename: P
authors.initials: P
authors.lastname: Noordhuis
authors.forename: V
authors.initials: V
authors.lastname: Erdélyi-Tóth
authors.forename: L
authors.initials: L
authors.lastname: Otvös
authors.forename: P
authors.initials: P
authors.lastname: Kovács
authors.forename: C L
authors.initials: CL
authors.lastname: Van der Wilt
authors.forename: G J
authors.initials: GJ
authors.lastname: Peters
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019540:Area Under Curve; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D003857:Deoxyuridine / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005468:Fluorodeoxyuridylate / Q000378:metabolism; D005472:Fluorouracil / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D013997:Time Factors; D016896:Treatment Outcome; D014498:Uracil / Q000031:analogs & derivatives / Q000097:blood; D014529:Uridine / Q000097:blood
chemical_list: D000964:Antimetabolites, Antineoplastic; D005468:Fluorodeoxyuridylate; C022811:edoxudin; C048011:5-ethyluracil; D014498:Uracil; C019389:5-fluorodihydrouracil; D005472:Fluorouracil; D003857:Deoxyuridine; D014529:Uridine