A phase II and pharmacologic study of fluorouracil given by a 1-hour infusion daily for 5 days with leucovorin and interferon alpha-2a in adenocarcinoma of the large bowel.

We have reported that increasing the length of infusion from 5 min to 1 h appeared to substantially reduce the toxicity associated with fluorouracil (5-FU) modulated by leucovorin (LV) and interferon alpha-2a (IFN-alpha). This phase II study assessed the antitumor efficacy of this regimen. Patients (n=38) with colorectal cancer received IFN-alpha 5 MU/m(2) SC on days 1-6; on days 2-6, LV 200 mg/m(2) IV was given with 5-FU at initial doses of 370-425 mg/m(2)/h. The regimen was well-tolerated with no grade 4 toxicity. At 425 mg/m(2) 5-FU, grade 3 toxicities included diarrhea (8.6%), anorexia, fever and fatigue (5.7% each), neutropenia and nausea/vomiting (2.9% each). Individuals tolerated 5-FU doses up to 644 mg/m(2). Objective responses occurred in 27% of 37 patients; median time to progression and survival were 6.1 and 12.9 months. Only 1 of 25 informative tumor samples had high-frequency microsatellite instability (MSI), while 7 of 23 assessable patients (30%) with MSI-negative tumors had an objective response. With 425 mg/m(2), the average 5-FU Cp and AUC(0-1 h) were 37.4 microM and 1161 microM/h. Some 6 patients had extended sampling, and the half-lives of 5-FU and FBAL (apparent) were 8.6 and 100.0 min, respectively. A 1-h infusion of 5-FU is well tolerated; individual dose escalation of 5-FU allows each patient to receive the maximum tolerable dose.

Biochemical and molecular effects of UCN-01 in combination with 5-fluorodeoxyuridine in A431 human epidermoid cancer cells.

Concurrent and pre-exposure of A431 human epidermoid cancer cells to UCN-01, an investigational anticancer drug, with 5-fluoro--2'-deoxyuridine (FdUrd), which targets thymidylate synthase, produced more than additive cytotoxicty. A 24-h exposure to 10 nM FdUrd led to inhibition of TS, a 2.5-fold increase in total thymidylate synthase protein content, profound dTTP depletion and a 6.3-fold increase in the ratio of dATP to dTTP, but did not cause single-strand breaks in DNA. However, FdUrd enhanced UCN-01-associated DNA strand breaks. Concurrent thymidine exposure led to repletion of dTTP pools, and cytoprotection against FdUrd alone and with UCN-01. UCN-01 arrested cells in G1, decreased the percentage of FdUrd-treated cells in S phase and reduced FdUrd-DNA incorporation, suggesting the latter was not important for cytotoxicity. Delayed induction of high molecular mass DNA fragmentation and poly(ADP-ribose) polymerase cleavage was observed with the combination of UCN-01 and FdUrd. These findings suggest that while FdUrd-mediated deoxynucleotide imbalance alone was insufficient to induce apoptosis in this p53-mutant cell line, it magnified UCN-01's effects, most likely by interfering with DNA repair. The clinical evaluation of UCN-01 combined with 5-fluoropyrimidines may be of interest.