Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Following p.o. administration to rats bearing advanced colorectal carcinoma, Ftorafur (FT) is converted to 5-fluorouracil (FUra) by microsomal P450 in the liver. To optimize the therapeutic selectivity of the FUra generated from FT, three approaches were utilized: (a) inhibition of FUra degradation to dihydrofluorouracil by uracil as an alternative substrate for uracil reductase in the molar ratio of 4 uracil:1 FT (UFT); (b) modulation of drug inhibition of thymidylate synthase by leucovorin (LV); and (c) by increasing the level of FUra incorporation into cellular RNA by N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartate transcarbomylase. The maximum tolerated dose (MTD) of FT and UFT, administered 3 times a day for 28 days, was 150 mg/kg/day and 60 mg/kg/day, respectively. The MTDs were not significantly modified by LV (150 or 600 mg/kg/day), administered by the p.o. route with the drugs, or by PALA (100 mg/kg) administered weekly by the i.v. route. The dose-limiting toxicity of FT alone and in combination with the modulators was stomatitis. The severe alopecia observed with FT alone was reduced significantly by uracil. At the MTD, the antitumor activity of UFT was superior to those of FT and FUra alone and in combination with LV and/or PALA. The 3-month sustained complete tumor regression for UFT, FT, and FUra was 38%, 0%, and 13% (for the weekly schedule), respectively. Although uracil, LV, and PALA individually increased the antitumor activity of FT at its MTD, the combination of the three modulators produced the highest therapeutic efficacy in rats bearing advanced colorectal carcinoma, in which 100% of the treated animals achieved complete and sustained tumor regression. The therapeutic efficacy observed with FT modulation could not be achieved with FUra administered by different schedules, each at its MTD alone or in combination with either LV or PALA. In brief, modulation of FT produced greater therapeutic efficacy and selectivity than FUra. Furthermore, the combined use of modulators capable of inhibiting the degradation pathway of FUra and potentiating the effects of the anabolic metabolites action appears to offer the greatest therapeutic potential.
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PMID:5-Fluorouracil prodrug: role of anabolic and catabolic pathway modulation in therapy of colorectal cancer. 981 53

We conducted a combined biochemical modulation trial of N-(phosphonacetyl)-L-aspartate (PALA), dipyridamole (DP), and fluorouracil (5-FU) in patients with cancer. Eighty-eight patients with advanced cancer were entered into this Phase I trial. During the first part of the study, four doses of PALA (125, 250, 500, and 1000 mg/m2, administered on day 1) were evaluated to determine the PALA dose with maximal suppression of aspartate transcarbamylase (ATCase) activity that was clinically tolerable. Patients were randomized to receive DP (or no DP), 50 mg/m2, p.o. every 6 h on days 1-6, and all patients received 5-FU, 400 mg/m2, by bolus administration on days 2-5. Prior to and during therapy, WBCs were collected and assayed for ATCase activity. After the maximally tolerated PALA dose with 400 mg/m2 5-FU +/- 50 mg/m2 DP was defined, the 5-FU dose was escalated using the same administration schedule of 5-FU, PALA, and DP. The dose of 5-FU was escalated by 25% in each of the DP cohorts until dose-limiting toxicity was reached. ATCase activity was inhibited in a dose-dependent manner with PALA doses of 125, 250, 500, and 1000 mg/m2, resulting in 0, 13, 17, and 49% inhibition of ATCase activity. Only at the higher PALA doses (i.e., 500 and 1000 mg/m2) was ATCase activity suppressed during days 2-5, but the activity returned to pretreatment levels by day 15. Based on the clinical tolerance and significant suppression of ATCase activity, a PALA dose of 500 mg/m2 was selected for the 5-FU dose escalation phase. At a 5-FU dose of 625 mg/m2, dose-limiting toxicity (leukopenia, stomatitis, and diarrhea) occurred in both DP cohorts. We recommend that for this monthly treatment schedule, 500 mg/m2 PALA and 500 mg/m2 5-FU, with or without 50 mg/m2 DP, be used in subsequent Phase II trials.
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PMID:Phase I study of N-(phosphonacetyl)-L-aspartate with fluorouracil and with or without dipyridamole in patients with advanced cancer. 981 75


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