5-fluorouracil (5-FU) is widely used in the treatment of cancer. Over the past 20 years, increased understanding of the mechanism of action of 5-FU has led to the development of strategies that increase its anticancer activity. Despite these advances, drug resistance remains a significant limitation to the clinical use of 5-FU. Emerging technologies, such as DNA microarray profiling, have the potential to identify novel genes that are involved in mediating resistance to 5-FU. Such target genes might prove to be therapeutically valuable as new targets for chemotherapy, or as predictive biomarkers of response to 5-FU-based chemotherapy.

5-Fluorouracil: mechanisms of action and clinical strategies

For the capecitabine–fluorouracil comparison, the hazard ratio for death in the capecitabine group was 0.86 (95% confidence interval [CI], 0.80 to 0.99); for the oxaliplatin–cisplatin comparison, the hazard ratio for the oxaliplatin group was 0.92 (95% CI, 0.80 to 1.10). The upper limit of the confidence intervals for both hazard ratios excluded the predefined noninferiority margin of 1.23. Median survival times in the ECF, ECX, EOF, and EOX groups were 9.9 months, 9.9 months, 9.3 months, and 11.2 months, respectively; survival rates at 1 year were 37.7%, 40.8%, 40.4%, and 46.8%, respectively. In the secondary analysis, overall survival was longer with EOX than with ECF, with a hazard ratio for death of 0.80 in the EOX group (95% CI, 0.66 to 0.97; P = 0.02). Progression-free survival and response rates did not differ significantly among the regimens. Toxic effects of capecitabine and fluorouracil were similar. As compared with cisplatin, oxaliplatin was associated with lower incidences of grade 3 or 4 neutropenia, alopecia, renal toxicity, and thromboembolism but with slightly higher incidences of grade 3 or 4 diarrhea and neuropathy. Conclusions Capecitabine and oxaliplatin are as effective as fluorouracil and cisplatin, respectively, in patients with previously untreated esophagogastric cancer. (Current Controlled Trials number, ISRCTN51678883.)

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Capecitabine and oxaliplatin for advanced esophagogastric cancer.

Prodrugs are bioreversible derivatives of drug molecules that undergo an enzymatic and/or chemical transformation in vivo to release the active parent drug, which can then exert the desired pharmacological effect. In both drug discovery and development, prodrugs have become an established tool for improving physicochemical, biopharmaceutical or pharmacokinetic properties of pharmacologically active agents. About 5-7% of drugs approved worldwide can be classified as prodrugs, and the implementation of a prodrug approach in the early stages of drug discovery is a growing trend. To illustrate the applicability of the prodrug strategy, this article describes the most common functional groups that are amenable to prodrug design, and highlights examples of prodrugs that are either launched or are undergoing human trials.

Prodrugs: design and clinical applications

BACKGROUND Intravenous bolus fluorouracil plus leucovorin is the standard adjuvant treatment for colon cancer. The oral fluoropyrimidine capecitabine is an established alternative to bolus fluorouracil plus leucovorin as first-line treatment for metastatic colorectal cancer. We evaluated capecitabine in the adjuvant setting. METHODS We randomly assigned a total of 1987 patients with resected stage III colon cancer to receive either oral capecitabine (1004 patients) or bolus fluorouracil plus leucovorin (Mayo Clinic regimen; 983 patients) over a period of 24 weeks. The primary efficacy end point was at least equivalence in disease-free survival; the primary safety end point was the incidence of grade 3 or 4 toxic effects due to fluoropyrimidines. RESULTS Disease-free survival in the capecitabine group was at least equivalent to that in the fluorouracil-plus-leucovorin group (in the intention-to-treat analysis, P<0.001 for the comparison of the upper limit of the hazard ratio with the noninferiority margin of 1.20). Capecitabine improved relapse-free survival (hazard ratio, 0.86; 95 percent confidence interval, 0.74 to 0.99; P=0.04) and was associated with significantly fewer adverse events than fluorouracil plus leucovorin (P<0.001). CONCLUSIONS Oral capecitabine is an effective alternative to intravenous fluorouracil plus leucovorin in the adjuvant treatment of colon cancer.

https://www.nejm.org/doi/pdf/10.1056/NEJMoa043116

Capecitabine as Adjuvant Treatment for Stage III Colon Cancer

PURPOSE: To compare the response rate, efficacy parameters, and toxicity profile of oral capecitabine with bolus intravenous (IV) fluorouracil plus leucovorin (5-FU/LV) as first-line treatment in patients with metastatic colorectal cancer. PATIENTS AND METHODS: We prospectively randomized 605 patients to treatment with oral capecitabine for 14 days every 3 weeks or 5-FU/LV by rapid IV injection daily for 5 days in 4-week cycles. RESULTS: The overall objective tumor response rate among all randomized patients was significantly higher in the capecitabine group (24.8%) than in the 5-FU/LV group (15.5%; P = .005). In the capecitabine and 5-FU/LV groups, median times to disease progression were 4.3 and 4.7 months (log-rank P = .72), median times to treatment failure were 4.1 and 3.1 months (P = .19), and median overall survival times were 12.5 and 13.3 months (P = .974), respectively. Capecitabine, compared with bolus 5-FU/LV treatment, produced a significantly lower incidence (P < .0002) of diarrhea, stomatit...

Comparison of Oral Capecitabine Versus Intravenous Fluorouracil Plus Leucovorin as First-Line Treatment in 605 Patients With Metastatic Colorectal Cancer: Results of a Randomized Phase III Study

Design of a novel oral fluoropyrimidine carbamate, capecitabine, which generates 5-fluorouracil selectively in tumours by enzymes concentrated in human liver and cancer tissue

The antitumor activity of cytostatic 5'-deoxy-5-fluorouridine (5'-dFUrd) depends on its being converted to 5-fluorouracil (5-FUra) by the enzyme thymidine phosphorylase (dThdPase, EC 2.4.2.4). We prepared mouse anti-human dThdPase monoclonal antibodies to serve as tools for clinical studies with this drug. Partially purified dThdPase obtained from HCT116 human colon cancer cells grown in athymic mice was used as an antigen for the immunization of mice. Six hydridomas were cloned which produced anti-human dThdPase antibodies, as detected by Western blot analysis with human dThdPase. With these antibodies, we developed an ELISA method sensitive enough to measure dThdPase levels, even in tumor tissue samples weighing as little as 10 mg. In addition, one monoclonal antibody was suitable for immunologically staining the enzyme in tumor tissues. Thus, these anti-human dThdPase monoclonal antibodies could be used to measure levels of the enzyme in tumor cells, which is essential for the activation of 5'-dFUrd.

Preparation of anti-human thymidine phosphorylase monoclonal antibodies useful for detecting the enzyme levels in tumor tissues.

To investigate the mechanism causing cachexia and its association with shorter patient survival, we cloned weight-loss-inducing and -non-inducing sublines of murine colon 26 carcinoma (colon 26). One clone, clone 20, induced substantial weight loss, wasting of adipose tissue and muscle, and hypogly-cemia in mice with a minimum tumor burden of 0.3 g (2 g per 100 g body weight). Clone-20-bearing mice had a median survival of 24.5 days with average tumor weight of 0.4 g. In contrast, clone 5 induced neither severe weight loss, wasting of adipose tissue and muscle, nor hypoglycemia; clone-5-bearing mice survived for a median of 70 days with average tumor weight of 12 g. These results clearly indicate that shorter survival is associated with the degree of cachexia and is independent of tumor size. Using this pair of colon 26 clones, we examined mediators of cachexia. Neither TNFα, IL-1α nor IFNγ was detected in the serum of mice bearing either clone, while IL-6 was detected in mice bearing both clones by ELISA and a bioassay. Administration of anti-IL-6 monoclonal antibody (MAb) partially but significantly suppressed cachexia induction in clone-20-bearing mice. These results point to the involvement of IL-6 in experimental cachexia. However, our finding of the presence of IL-6 in the serum of mice bearing clone 5, which does not induce weight loss, clearly indicates that IL-6 is not solely responsible for the induction of cachexia. © 1995 Wiley-Liss, Inc.

Establishment and characterization of cachexia-inducing and -non-inducing clones of murine colon 26 carcinoma.

Murine colon 26 carcinoma causes cachexia even when the tumor burden is small. In this tumor model, murine IL-12 suppressed the induction of cancer cachexia and also inhibited tumor growth. IL-12 reduced the serum levels of IL-6, a cachexia mediator in this model, and alleviated the body weight loss and other abnormalities associated with cachexia, such as adipose tissue wasting and hypoglycemia. The anticachectic activity was observed even at low doses of IL-12, insufficient to inhibit tumor growth. IL-12 greatly increased levels of IFN-gamma in the tumor tissue and, to a lesser extent, in the circulation. IFN-gamma given intraperitoneally also prevented cancer cachexia, although it did not reduce IL-6 levels either in the tumor or in the circulation. In athymic mice bearing the same colon 26 tumor, IL-12 was no longer anticachectic and did not induce IFN-gamma. These results indicate that the anticachectic activity of IL-12 is T-cell-dependent and results from at least 2 mechanisms, the down-regulation of IL-6 and the up-regulation of IFN-gamma.

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Kazushige Mori

Papers

Design of a novel oral fluoropyrimidine carbamate, capecitabine, which generates 5-fluorouracil selectively in tumours by enzymes concentrated in human liver and cancer tissue

Preparation of anti-human thymidine phosphorylase monoclonal antibodies useful for detecting the enzyme levels in tumor tissues.

Establishment and characterization of cachexia-inducing and -non-inducing clones of murine colon 26 carcinoma.

Murine interleukin‐12 prevents the development of cancer cachexia in a murine model