levoleucovorin and 5-fluorouridine

5-Fluorouracil (5-FU) is a common anticancer agent used in the treatment of solid tumours, with a reported variability in the pharmacokinetic profile and inter-patient differences in efficacy and toxicity. Since 5-FU is intracellularly metabolised to active cytotoxic fluoronucleotides, some authors suggested it would be useful to determine the plasma levels of its main metabolites 5-fluoro-5,6-dihydrouracil (5-FUH2), 5-fluorouridine (5-FUrd) and 5-fluoro-2'-deoxyuridine (5-FdUrd), in order to better characterise population pharmacokinetics-pharmacodynamics (PK-PD) of this drug. We developed and validated an HPLC method to simultaneously determine plasma concentrations of 5-FU and the three main metabolites, and we analysed the plasma concentration-time curves of the first dose of 18 colon cancer patients treated with folinic acid and 5-FU 400 mg m(-2) by intra-venous bolus injection as adjuvant chemotherapy. Non-compartmental PK analysis has been applied to 5-FU and 5-FUH2 concentrations, estimating the following parameters (median values): Cmax 55.44 and 6.23 microg ml(-1), respectively, AUC(0-2 h) 11.59 and 5.94 hx microg ml(-1), CLTB 30.64 and 51.81 lh(-1) m(-2), 5-FUH2/5-FU AUC ratio 0.47 (range 0.29-1.12). We verified the patient covariables which could influence the inter-patient variability in the area under the time-concentration curves, and we observed that age, sex, weight, body surface area, cycle of therapy, toxicity development and 5-FUrd or 5-FdUrd detectability did not have statistical influence on 5-FUH2/5-FU AUC ratio. In eight subjects, we compared the PK data of the first and the fifth day of dose administration, and we found stable 5-FU values, but the 5-FUH2 disposition decreased with lower AUC(0-2 h) (7.90 hx microg ml(-1) versus 5.99 hx microg ml(-1)) and, particularly, Cmax (8.38 microg ml(-1) versus 5.50 microg ml(-1)) at day 5. This fact, evident in almost every patient, could suggest a possible reduction in the catabolic pathway of 5-FU leading to 5-FUH2, with a possible increase of the therapeutic pathway. For this reason, we tried to detect 5-FUrd and 5-FdUrd and, in fact, in our patients these metabolites were detected only in few samples, but most of them at day 5. In conclusion, our study confirms the relevance of pharmacokinetic analysis of 5-FU main metabolites and especially 5-FUH2, to better understand the metabolism and to improve the therapeutic efficacy.

Topics: Adult; Aged; Area Under Curve; Chromatography, High Pressure Liquid; Colonic Neoplasms; Drug Administration Schedule; Drug Evaluation; Female; Floxuridine; Fluorouracil; Humans; Infusions, Intravenous; Injections, Intravenous; Kinetics; Leucovorin; Male; Middle Aged; Uridine

FOLFIRINOX and FOLFOXIRI are combination chemotherapy treatments that incorporate the same drug cocktail (folinic acid, 5-fluorouracil, oxaliplatin and irinotecan) but exploit an altered dosing regimen when used in the management of pancreatic and colorectal cancer, respectively. Both have proven effective in extending life when used to treat patients with metastatic disease but are accompanied by significant adverse effects. To facilitate improved tumour-targeting of this drug combination, an ultrasound responsive microbubble formulation loaded with 5-fluorouridine, irinotecan and oxaliplatin (FIRINOX MB) was developed and its efficacy tested, together with the non-toxic folinic acid, in preclinical murine models of pancreatic and colorectal cancer. A significant improvement in tumour growth delay was observed in both models following ultrasound targeted microbubble destruction (UTMD) mediated FIRINOX treatment with pancreatic tumours 189% and colorectal tumours 82% smaller at the conclusion of the study when compared to animals treated with a standard dose of FOLFIRINOX. Survival prospects were also improved for animals in the UTMD mediated FIRINOX treatment group with an average survival of 22.17 ± 12.19 days (pancreatic) and 44.40 ± 3.85 days (colorectal) compared to standard FOLFIRINOX treatment (15.83 ± 4.17 days(pancreatic) and 37.50 ± 7.72 days (colon)). Notably, this improved efficacy was achieved using FIRINOX MB that contained 5-fluorouricil, irinotecan and oxaliplatin loadings that were 13.44-fold, 9.19-fold and 1.53-fold lower than used for the standard FOLFIRINOX treatment. These results suggest that UTMD enhances delivery of FIRINOX chemotherapy, making it significantly more effective at a substantially lower dose. In addition, the reduced systemic levels of 5-fluorouracil, irinotecan and oxaliplatin should also make the treatment more tolerable and reduce the adverse effects often associated with this treatment.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Camptothecin; Colonic Neoplasms; Fluorouracil; Humans; Irinotecan; Leucovorin; Mice; Microbubbles; Oxaliplatin; Pancreatic Neoplasms; Treatment Outcome; Uridine

Antitumor effect and active metabolites of fluoropyrimidines were examined in mice with transplantable colon adenocarcinoma 38 (Co 38). 5-Fluoro-2'-deoxyuridine (FUdR) treatment resulted in a much higher level of free 5-fluoro-2'-deoxyuridine-5'-monophosphate in the tumor than 5-fluorouracil (5-FU) did, and thymidylate synthase was almost completely inhibited after FUdR treatment, but FUdR showed weaker antitumor activity than 5-FU did. Moreover, 5-fluorouridine (FUR) also hardly inhibited tumor growth. A more marked tumor inhibition was obtained when FUdR and FUR were administered together. The antitumor activity of 5-FU was similar to that of the combination of FUdR and FUR. In combination with 2,2'-anhydro-5-ethyluridine, a uridine phosphorylase inhibitor, FUdR lost its antitumor activity, but that of FUR was somewhat potentiated. On the other hand, in combination with leucovorin (LV), 5-FU showed markedly potentiated antitumor activity, while the antitumor activity of FUdR or FUR was not potentiated. Addition of LV to the combination of FUdR and FUR enhanced the inhibitory effect of the drugs. From these results, the combination of FUdR and FUR together with LV, and the combination of 5-FU and LV seem to be highly efficacious against Co 38.

Topics: Adenocarcinoma; Animals; Antineoplastic Combined Chemotherapy Protocols; Biotransformation; Cell Division; Colonic Neoplasms; Floxuridine; Fluorodeoxyuridylate; Fluorouracil; Leucovorin; Male; Mice; Mice, Inbred Strains; Thymidylate Synthase; Uridine

We investigated the biological activities of the natural and unnatural diastereoisomers of 5-formyltetrahydrofolate [(6S)- and (6R)-5-HCO-H4PteGlu, respectively, both 99.99% pure], using a human ileocecal carcinoma cell line (HCT-8). Optimal cell growth could be supported by (6S)-5-HCO-H4PteGlu at concentrations as low as 1 nM. (6R)-5-HCO-H4PteGlu did not support growth. Modulation of the in vitro cytotoxicity of 5-fluoro-2'-deoxyuridine (FdUrd) and intracellular (6R)-5,10-methylenetetrahydrofolates [(6R)-CH2H4PteGlun] pools by (6S)- and (6R)-5-HCO-H4PteGlu was determined with cells growing in 1 nM (6S)-5-HCO-H4PteGlu. For the control cells, the concentration of FdUrd inhibiting growth by 50% was 179 nM and the total (6R)-CH2H4PteGlun was 2.3 pmol/10(6) cells. When cells were treated with (6S)-5-HCO-H4PteGlu for 24 h, the 50% inhibition concentration of FdUrd decreased with increasing concentrations of (6S)-5-HCO-H4PteGlu, and reached a plateau of 36 nM when (6S)-5-HCO-H4PteGlu was greater than or equal to 1 microM. The total (6R)-CH2H4PteGlun pools were augmented by (6S)-5-HCO-H4PteGlu dose dependently up to 6.8 pmol/10(6) cells at 1 microM (6S)-5-HCO-H4PteGlu. (6S)-5-HCO-H4PteGlu at 10 microM did not further increase the total (6R)-CH2H4PteGlun, but induced a marked shift in the polyglutamate chain length distribution, with an increase in tri- and tetra-, and a decrease in penta-, hexa-, and heptaglutamate. The down-shift of (6R)-CH2H4-PteGlun polyglutamate chain length observed after (6S)-5-HCO-H4PteGlu treatment did not impair the modulation of FdUrd cytotoxicity. Thus shorter chain (6R)-CH2H4PteGlua (n = 3-4) function as well as longer ones (n = 5-7). (6R)-5-HCO-H4PteGlu, at 200 microM, had no effect on the cytotoxicity of FdUrd, the total (6R)-CH2H4PteGlun level, or chain length distribution in the presence or absence of additional (6S)-5-HCO-H4PteGlu. These results suggest that the high plasma (6R)-5-HCO-H4PteGlu concentrations (up to 200 microM) achieved in patients following i.v. administration of high doses of (6R,S)-5-HCO-H4PteGlu probably do not have adverse effects on the modulation of antitumor activity of FdUrd or 5-fluorouracil. Since the optimal dose and schedule of (6S)-5-HCO-H4PteGlu for modulation of fluoropyrimidines may vary from one cell type to another, introducing high doses of (6R,S)-5-HCO-H4PteGlu in patients so that the plasma concentration of the natural isomer reaches 10 microM is still recommended.

Topics: Cell Division; Chromatography, High Pressure Liquid; Cytoplasm; Humans; In Vitro Techniques; Leucovorin; Pteroylpolyglutamic Acids; Stereoisomerism; Structure-Activity Relationship; Tumor Cells, Cultured; Uridine

The action of fluoropyrimidine (FP) drugs at thymidylate synthase (TS) is associated with enhanced chemotherapeutic response. Calcium leucovorin (CF) increases the cytotoxicity of the FP drugs, 5-fluorouracil and 5-fluorodeoxyuridine, in human laryngeal carcinoma HEp-2 cells by directing the action of these drugs at TS. Thus, the effect of CF on the cytotoxicity and site of action of the FP, 5-fluorouridine (FUrd), was investigated in HEp-2 cells. The cytotoxicity of FUrd was unaffected by CF. Moreover, CF was unable to alter the growth-limiting target of FUrd to TS. HEp-2 cells convert FUrd to FdUMP, the FP metabolite that is the direct inhibitor of TS; thus, the inability of CF to modulate FUrd action is not due to lack of inhibitor formation. In addition, greater than 90 percent of TS activity is inhibited at concentrations of FUrd that inhibit HEp-2 cell growth by 50 percent. Thus, while TS is significantly inhibited by FUrd, it is not the growth-limiting target of this drug. It is likely that the RNA-directed effects of FUrd are so extensive that CF, which maximizes TS-directed action, is ineffective at reducing the cytotoxicity further. An approach to overcoming the RNA-directed effects of FUrd is suggested.

Topics: Fluorodeoxyuridylate; Humans; Leucovorin; RNA, Ribosomal; Thymidylate Synthase; Tumor Cells, Cultured; Uridine