A human capecitabine excretion balance and pharmacokinetic study after administration of a single oral dose of 14C-labelled drug

An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 microCi of 14C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and 19F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86-104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71-95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69-7.0) was collected in the feces. Over a collection period of 24-48 h, a total of 84.2% (range 80-95) was recovered in the urine as the sum of the parent drug and measured metabolites (5'-DFCR, 5'-DFUR, 5-FU, FUH2, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (tmax 0.25-1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.

Bioequivalence of two tablet formulations of capecitabine and exploration of age, gender, body surface area, and creatinine clearance as factors influencing systemic exposure in cancer patients

PURPOSE

The objective of the study was to assess the bioequivalence of two tablet formulations of capecitabine and to explore the effect of age, gender, body surface area and creatinine clearance on the systemic exposure to capecitabine and its metabolites.

METHODS

The study was designed as an open, randomized two-way crossover trial. A single oral dose of 2000 mg capecitabine was administered on two separate days to 25 patients with solid tumors. On one day, the patients received four 500-mg tablets of formulation B (test formulation) and on the other day, four 500-mg tablets of formulation A (reference formulation). The washout period between the two administrations was between 2 and 8 days. After each administration, serial blood and urine samples were collected for up to 12 and 24 h, respectively. Unchanged capecitabine and its metabolites were determined in plasma using LC/MS-MS and in urine by NMRS.

RESULTS

Based on the primary pharmacokinetic parameter, AUC(0-infinity) of 5'-DFUR, equivalence was concluded for the two formulations, since the 90% confidence interval of the estimate of formulation B relative to formulation A of 97% to 107% was within the acceptance region 80% to 125%. There was no clinically significant difference between the t(max) for the two formulations (median 2.1 versus 2.0 h). The estimate for C(max) was 111% for formulation B compared to formulation A and the 90% confidence interval of 95% to 136% was within the reference region 70% to 143%. Overall, these results suggest no relevant difference between the two formulations regarding the extent to which 5'-DFUR reached the systemic circulation and the rate at which 5'-DFUR appeared in the systemic circulation. The overall urinary excretions were 86.0% and 86.5% of the dose, respectively, and the proportion recovered as each metabolite was similar for the two formulations. The majority of the dose was excreted as FBAL (61.5% and 60.3%), all other chemical species making a minor contribution. Univariate and multivariate regression analysis to explore the influence of age, gender, body surface area and creatinine clearance on the log-transformed pharmacokinetic parameters AUC(0-infinity) and C(max) of capecitabine and its metabolites revealed no clinically significant effects. The only statistically significant results were obtained for AUC(0-infinity) and C(max) of intact drug and for C(max) of FBAL, which were higher in females than in males.

CONCLUSION

The bioavailability of 5'-DFUR in the systemic circulation was practically identical after administration of the two tablet formulations. Therefore, the two formulations can be regarded as bioequivalent. The variables investigated (age, gender, body surface area, and creatinine clearance) had no clinically significant effect on the pharmacokinetics of capecitabine or its metabolites.

Oral fluoropyrimidines: a closer look at their toxicities

Patient preferences, quality of life issues, and economic considerations are driving the development of orally administered chemotherapy. Oral fluorinated pyrimidines, which have been used in Japan, are attracting increasing interest as a means to provide convenient, less toxic treatment without compromising efficacy. The oral fluoropyrimidines provide prolonged 5-fluorouracil (5-FU) exposure at lower peak concentrations than those observed with bolus intravenous administration. Moreover, depending on the dose schedule, the pharmacokinetics of the oral fluoropyrimidines may mimic the pharmacokinetics of continuous-infusion 5-FU. This review focuses on the toxicity profiles of five emerging oral fluoropyrimidine antineoplastic drugs: combined uracil and tegafur (UFT), capecitabine, eniluracil, S-1, and emitefur (BOF-A2). Different patterns of toxicities emerge from an analysis of the clinical trials of these agents relative to 5-FU administered as an intermittent intravenous bolus or as continuous infusion. The results of ongoing phase III trials comparing the oral fluoropyrimidines with conventional regimens of 5-FU plus leucovorin and 5-FU by continuous intravenous infusion are necessary before their therapeutic role in the management of colorectal carcinoma can be defined.

X-ray irradiation induces thymidine phosphorylase and enhances the efficacy of capecitabine (Xeloda) in human cancer xenografts

Thymidine phosphorylase (dThdPase) is an essential enzyme for the activation of the cytostatics capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) and its intermediate metabolite 5'-deoxy-5-fluorouridine (5'-dFUrd) to 5-fluorouracil (5-FUra) in tumors. We observed previously that several cytokines and cytostatics up-regulated dThdPase expression and consequently enhanced the efficacy of capecitabine and 5'-dFUrd. In the present study, we found that X-ray irradiation also up-regulated dThdPase expression in several human cancer xenografts. A single-dose local irradiation at 5 Gy increased dThdPase levels by up to 13-fold at 9 days after the irradiation. Whole-body irradiation also up-regulated dThdPase in a tumor, but it did not increase the enzyme level in the liver. We also observed that the irradiation increased the levels of human tumor necrosis factor alpha (TNF-alpha), which is an up-regulator of dThdPase, prior to the dThdPase up-regulation. These results indicate that X-ray irradiation might increase dThdPase levels indirectly through the human TNF-alpha in the tumor tissue. In the WiDr colon and MX-1 mammary human cancer xenograft models, the combination of a single local X-ray irradiation with either capecitabine or 5'-dFUrd was much more effective than either radiation or chemotherapy alone. In contrast, treatment with X-ray irradiation and 5-FUra in combination showed no clear additive effects. Combined modality treatment of cancer patients with cape-citabine and X-ray irradiation would have greater potential usefulness than conventional radiochemotherapy with 5-FUra.

Induction of thymidine phosphorylase expression and enhancement of efficacy of capecitabine or 5'-deoxy-5-fluorouridine by cyclophosphamide in mammary tumor models

Thymidine phosphorylase (dThdPase) is an essential enzyme for the activation of the oral cytostatic drugs capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine, Xeloda(trade mark)) and its intermediate metabolite doxifluridine [5'-deoxy-5-fluorouridine (5'-dFUrd, Furtulon((R)))] to 5-fluorouracil (5-FUra) in tumors. In a previous study, we found that several cytostatics were able to up-regulate tumor levels of dThdPase in a human colon cancer xenograft model. In the present study, we confirmed that the administration of cytostatics used for breast cancer treatment, such as taxanes and cyclophosphamide (CPA), up-regulated the tumor level of dThdPase in mammary tumor models as well. Because the dThdPase up-regulation was observed even when CPA was given orally, we investigated further the usefulness of combination therapy with the 2 oral drugs, 5'-dFUrd/capecitabine and CPA in mammary tumor models. Daily oral administration of CPA up-regulated human dThdPase levels in the tumor tissue of mice bearing a human mammary tumor xenograft, MX-1, whereas in the small intestine and liver, it did not affect levels of pyrimidine nucleoside phosphorylases (PyNPase) including dThdPase and uridine phosphorylase. The preferential up-regulation of PyNPase activity in the tumor by CPA administration was also confirmed in mice bearing a syngeneic murine mammary adenocarcinoma, A755. In both models, combination therapy of 5'-dFUrd/capecitabine with CPA showed synergistic antitumor activity, without significant potentiation of toxicity. In contrast, treatment with CPA and either 5-FUra or UFT (a mixture of tegafur and uracil) in combination showed only additive activity. Our results suggest that CPA and capecitabine/5'-dFUrd, both available for oral administration, would be good partners, and that clinical trials with this drug combination against breast cancer are warranted.

The oral fluoropyrimidines in cancer chemotherapy

A classic example of a rationally developed class of anticancer drugs, the fluoropyrimidines are now the focus of further rational approaches to cancer chemotherapy as they are transformed into oral formulations. Given alone, oral 5-fluorouracil (5-FU) has erratic absorption and nonlinear pharmacokinetics. However, when oral 5-FU is given as a prodrug and/or paired with a dihydropyrimidine dehydrogenase inhibitor, the resultant 5-FU has linear pharmacokinetics that may approximate the less myelosuppressive continuous i.v. infusion schedule of 5-FU administration without the use of infusion catheters and pumps. We review the preclinical and clinical experience of several of the oral fluoropyrimidines.

A review of the pharmacology and clinical activity of new chemotherapy agents for the treatment of colorectal cancer

Colorectal carcinoma is an important cause of cancer morbidity and mortality. 5-fluorouracil has been the major chemotherapeutic agent for the treatment of colorectal carcinoma for the past four decades. This regimen is noncurative, and its impact on survival is unclear. Attempts at identifying more effective chemotherapeutic agents for colorectal cancer have yielded oral formulations and prodrugs of 5-fluorouracil with apparently equivalent efficacy. Specific thymidylate synthase inhibitors are now available. Platinum analogues with activity in colorectal carcinoma, and no cross-resistance to the antimetabolites have also been developed. The topoisomerase I inhibitors represent a new class of agents with a novel mechanism of action. These agents are in phase II and Phase III clinical trials, others have been approved for clinical use within the last 3 years.

Xeloda in the treatment of metastatic breast cancer

There are few treatment options available for patients with metastatic breast cancer who have failed anthracycline- and paclitaxel-based chemotherapy. Xeloda (capecitabine) is a novel selectively tumoractivated fluoropyrimidine carbamate producing clinically active levels of 5-fluorouracil (5-FU) at the tumor site. Xeloda is active in breast cancer and is administered orally. It is the only registered treatment for patients in whom anthracycline and taxoid treatment has failed. In a phase II trial of 163 paclitaxel-refractory patients with metastatic breast cancer, the overall response rate with Xeloda was 20%, with three complete responses, and the median survival was 12.8 months. A total of 20% of patients experienced a Clinical Benefit Response (a composite assessment of clinical benefit). Furthermore, Xeloda was well tolerated; the most common treatment-related adverse events were hand-foot syndrome, diarrhea, nausea, vomiting, and fatigue. Two additional studies of Xeloda in patients with metastatic breast cancer have also been completed. In the first study, patients with anthracycline-resistant metastatic breast cancer received either Xeloda or paclitaxel; the response rates were 36 and 26%, respectively. In the second study, women aged >/=55 years received first-line treatment with either Xeloda or cyclophosphamide/methotrexate/5-FU. The response rates were 25 and 16%, respectively. These studies show that Xeloda is an active agent in the treatment of metastatic breast cancer with the additional advantage of oral administration.

Effect of hepatic dysfunction due to liver metastases on the pharmacokinetics of capecitabine and its metabolites

Capecitabine (Xeloda) is a rationally designed oral, tumor-selective fluoropyrimidine carbamate aimed at preferential conversion to 5-fluorouracil (5-FU) within the tumor. Because capecitabine is extensively metabolized by the liver, it is important to establish whether liver dysfunction altered the pharmacokinetics of capecitabine and its metabolites. This was investigated in 14 cancer patients with normal liver function and in 13 with mild to moderate disturbance of liver biochemistry due to liver metastases. They received a single oral dose of capecitabine (1255 mg capecitabine/m2) with serial blood and urine samples collected up to 72 h after administration. Concentrations of capecitabine and its metabolites were determined in plasma by high-performance liquid chromatography or liquid chromatography coupled to mass spectrometry and in urine by 19F-nuclear magnetic resonance spectroscopy. Although plasma concentrations of capecitabine, 5'-deoxy-5-fluorouridine, 5-FU, dihydro-5-FU, and alpha-fluoro-beta-alanine were, in general, higher in patients with liver dysfunction, the opposite was found for 5'-deoxy-5-fluorocytidine. These effects were not clinically significant. Total urinary recovery of capecitabine and its metabolites was 71% of the administered dose in patients with normal hepatic function and 77% in patients with hepatic impairment. The absolute bioavailability of 5'-deoxy-5-fluorouridine was estimated as 42% in patients with normal hepatic function and 62% in patients with impaired hepatic function. In summary, mild to moderate hepatic dysfunction had no clinically significant influence on the pharmacokinetic parameters of capecitabine and its metabolites. Although caution should be exercised when capecitabine is administered to patients with mildly to moderately impaired hepatic function, there is no need for, a priori, adjustment of the dose.

Capecitabine

Capecitabine is an orally administered fluoropyrimidine carbamate used for the treatment of paclitaxel- or anthracycline-refractory breast cancer. Capecitabine is metabolised via a 3-step process to the active agent fluorouracil. The final step of this process occurs preferentially in malignant tissue. In patients with paclitaxel-refractory breast cancer receiving capecitabine (2510 mg/m2/day for 2 weeks of a 3-week cycle) the objective tumour response rate was 20%. Disease progression occurred in 34% of patients and 40% had stable disease. In this trial, the median duration of response was 241 days. Disease progression or death occurred in 83% of patients, and median time to progression was 93 days. Median survival time was 384 days. In previously untreated patients with breast cancer, the response rate was higher and time to disease progression was longer after oral capecitabine (2510 mg/m2/day for 2 weeks of a 3-week cycle) than after intravenous cyclophosphamide, methotrexate and fluorouracil therapy. In clinical trials, generally gastrointestinal or haematological adverse events were reported most frequently. Other commonly reported events included hand-and-foot syndrome, fatigue, hyperbilirubinaemia, dermatitis and anorexia.

Rational design of new tumoractivated cytotoxic agents

5-Fluorouracil (5-FU) plays an important role in the treatment of several tumor types, particularly colorectal cancer and breast cancer. Xeloda (capecitabine; 5'-deoxy-5-fluoro-N-[(pentyloxy)carbonyl-cytidine]) is a new rationally designed fluoropyrimidine carbamate. It is administrated orally and after absorption it is first metabolized to 5'-deoxy-5-fluorocytidine (5'-DFCR) by carboxylesterase from the liver and then converted to 5'-deoxy-5-fluorouridine (5'-DFUR) by cytidine deaminase from the liver and tumor tissues. Finally, thymidine phosphorylase (TP) converts 5'-DFUR to 5-FU. TP is more active in tumor tissues than in normal tissue. This tissue localization pattern results in preferential metabolism and generates higher levels of 5-FU in malignant tissue, thus enhancing efficacy but minimizing side effects. The tumor tissue selectivity was confirmed in a study of 19 patients with colorectal cancer. After Xeloda administration, concentrations of 5-FU were 2.5 times higher in the primary tumor compared with adjacent healthy tissue. Xeloda was highly active in human tumor xenografts. It was more active than 5-FU, 5'-DFUR and tegafur plus uracil (UFT) and had a better therapeutic index. Xeloda also demonstrated synergistic or additive activity when used in combination with cyclophosphamide, methotrexate, doxorubicin, paclitaxel and docetaxel. This may be in part a result of up-regulation of TP by the cytotoxic agents. Phase I and II clinical trials have shown that Xeloda is active across a range of tumor types, and phase III studies are ongoing.

Optimizing chemotherapy for patients with advanced breast cancer

Chemotherapy is offered to almost all patients with metastatic breast cancer. Optimization of treatment has four major goals: (1) To improve access to chemotherapy. Orally active chemotherapy is an attractive option for those patients when access to hospital is limited by financial considerations, long journeys or patient reluctance. In the past, only alkylating agents (cyclophosphamide, chlorambucil, melphalan) could be administered orally. The activity (first- and second-line) of Xeloda (capecitabine) with limited side effects and the development of oral vinorelbine and anthracyclines should improve access to chemotherapy and also concentrate further interest on treatment with long-term administration of cytotoxic agents. (2) To improve response rates and duration in first-line treatment. Response rates have been increased by the use of combinations of taxoids and anthracyclines and/or alkylating agents and/or fluoropyrimidines (>60-70% with complete remission in 10-15% of patients). There is increasing interest in sequential use of active agents or combinations at their optimal doses. Nevertheless, such 'induction regimen' fail to prolong response duration (rarely longer than 9-12 months). The use of less-toxic maintenance chemotherapy regimens increases response duration and disease-free survival. Such maintenance regimens could be used on an outpatient basis and will be further simplified by the availability of active oral agents such as the novel fluoropyrimidine Xeloda. (3) To increase cure rates. This can only be considered with first-line treatment in selected patients (long disease-free interval, minimal number of visceral sites and ability to tolerate high-dose chemotherapy). The completed studies with high-dose chemotherapy and hematopoietic stem cell support have, in fact, shown only a minimal effect on cure rates. Incorporation of very active agents such as taxoids and use of multicycle high-dose therapy may improve these results. (4) To offer alternative active regimens in second and subsequent metastatic progression. Taxoids, vinorelbine and, more recently, Xeloda all achieve a 20-40% response rate in these situations. The reintroduction of agents previously used for adjuvant or first-line therapy can also be considered.

Potential of Xeloda in colorectal cancer and other solid tumors

For over four decades, 5-fluorouracil (5-FU) has been the mainstay of therapy for colorectal cancer and a major cytotoxic agent for treating gastrointestinal tumors and a variety of others, including breast and head and neck cancers. Xeloda (capecitabine) is a new drug that is administered orally and has been rationally designed to generate 5-FU selectively within solid tumors. Theoretically, it has two major advantages, which should translate into an improved therapeutic index: firstly, enhanced drug concentration at the cancer site and therefore greater anti-tumor activity and secondly, reduced drug levels in non-tumor tissues, with a consequent reduction in systemic toxicity. After promising preclinical studies, phase I clinical trials of Xeloda have been performed with a variety of schedules, both with and without the oral biomodulator leucovorin. Anti-tumor activity has been observed with all regimens tested. In the setting of colorectal cancer, a randomized phase II study substantiated the phase I reports of activity and established the most promising regimen for phase III clinical trials. Patients in the phase II trial were randomly selected to receive either continuous Xeloda, intermittent Xeloda or intermittent Xeloda plus leucovorin. There were complete or partial responses in 21% of patients in the continuous arm, 24% in the intermittent arm, and 23% in the arm with intermittent Xeloda plus leucovorin. In addition, 51-63% of patients in each arm achieved stable disease. Therapy was well tolerated in all three arms. The intermittent regimen of Xeloda alone was associated with a longer time to disease progression and offered a one-week rest period to the patient. It was therefore selected for subsequent studies. Two randomized phase III trials of Xeloda versus the 'Mayo' regimen in patients with advanced colorectal cancer have completed recruitment. They are designed to demonstrate at least equivalent efficacy, with important secondary endpoints of comparisons of toxicity, medical care utilization, and quality of life. No formal results are yet available from these studies. The same regimen of Xeloda is now being evaluated in a large scale adjuvant study, which is expected to recruit approximately 1,700 Dukes' C colonic cancer patients (X-ACT study). The modest toxicity of Xeloda (particularly its low incidence of neutropenia) makes it a suitable candidate for novel combination therapies involving other agents that are active in colorectal cancer, including camptothecin and its analogues, oxaliplatin and radiotherapy. Further studies of Xeloda can be expected with other diseases known to be responsive to fluoropyrimidines, together with diseases traditionally thought to be resistant.

Fluoropyrimidines: a critical evaluation

After nearly four decades of clinical experience with the fluoropyrimidines, 5-fluorouracil (5-FU) remains an integral part of chemotherapy for colorectal cancer. A range of 5-FU treatment regimens with or without biochemical modulation are currently used and toxicity appears to be schedule dependent. The use of oral 5-FU was abandoned because of erratic absorption caused by varying levels of dihydropyrimidine dehydrogenase (DPD) found in the gastrointestinal tract. This effect may be overcome by administering agents that are converted to 5-FU or by inhibiting or inactivating DPD. Xeloda((R)) (capecitabine) was designed as an orally administered, selectively tumoractivated(TM) cytotoxic agent which achieves higher levels of 5-FU in the primary tumor than in plasma or other tissues. The United States Food and Drug Administration (FDA) has approved Xeloda for use in patients with metastatic breast cancer resistant to paclitaxel and in whom further anthracycline therapy is contraindicated. Xeloda is also registered in Canada, Switzerland, Thailand and Argentina. In phase II clinical trials in colorectal cancer, Xeloda produced response rates of 21-24% and median time to disease progression of 127-230 days. Other oral agents in development for the treatment of colorectal cancer include tegafur/uracil plus oral leucovorin, S-1 and eniluracil plus oral 5-FU.

Phase I and pharmacokinetic study of the oral fluoropyrimidine capecitabine in combination with paclitaxel in patients with advanced solid malignancies

PURPOSE

To evaluate the feasibility of administering the oral fluoropyrimidine capecitabine in combination with paclitaxel, to characterize the principal toxicities of the combination, to recommend doses for subsequent disease-directed studies, and to determine whether significant pharmacokinetic interactions occur between these agents when combined.

PATIENTS AND METHODS

Sixty-six courses of capecitabine and paclitaxel were administered to 17 patients in a two-stage dose-escalation study. Paclitaxel was administered as a 3-hour intravenous (IV) infusion every 3 weeks, and capecitabine was administered continuously as two divided daily doses. During stage I, capecitabine was escalated to a target dose of 1,657 mg/m(2)/d, whereas the paclitaxel dose was fixed at 135 mg/m(2). In stage II, paclitaxel was increased to a target dose of 175 mg/m(2), and the capecitabine dose was the maximum established in stage I. Pharmacokinetics were characterized for each drug when given alone and concurrently.

RESULTS

Myelosuppression, predominately neutropenia, was the principal dose-limiting toxicity (DLT). Other toxicities included hand-foot syndrome, diarrhea, hyperbilirubinemia, skin rash, myalgia, and arthralgia. Two patients treated with capecitabine 1,657 mg/m(2)/d and paclitaxel 175 mg/m(2) developed DLTs, whereas none of six patients treated with capecitabine 1,331 mg/m(2)/d and paclitaxel 175 mg/m(2) developed DLTs during course 1. Pharmacokinetic studies indicated that capecitabine and paclitaxel did not affect the pharmacokinetic behavior of each other. No major antitumor responses were noted.

CONCLUSION

Recommended combination doses of continuous capecitabine and paclitaxel are capecitabine 1,331 mg/m(2)/d and paclitaxel 175 mg/m(2)/d IV every 3 weeks. Favorable preclinical mechanistic interactions between capecitabine and paclitaxel, as well as an acceptable toxicity profile without clinically relevant pharmacokinetic interactions, support the performance of disease-directed evaluations of this combination.

Capecitabine: nursing implications of a new oral chemotherapeutic agent

PURPOSE/OBJECTIVES

To describe the new oral chemotherapeutic agent capecitabine (Xeloda, Roche Laboratories Inc., Nutley, NJ) and key concepts driving its development and to delineate the nursing impact of patient-administered, home-based chemotherapies.

DATA SOURCES

Published papers, investigational materials, package inserts, and clinical experience.

DATA SYNTHESIS

Capecitabine recently was approved to treat metastatic breast cancer refractory to paclitaxel and anthracycline-containing regimens. Efficacy has been demonstrated. However, although the current regimen is well-tolerated, > or = 40% of patients require dose modification because of grade 2 or greater toxicity, usually hand-foot syndrome or gastrointestinal symptoms.

CONCLUSIONS

Capecitabine frees nurses from infusion-related workload, allowing and demanding a new type and level of patient education. Such education emphasizes compliance with the treatment plan and prevention, timely recognition, and management of toxicities. These practice changes also challenge nurses to advocate for reimbursement of educational practices.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses will play more of a central role as use of patient-administered, home-based therapies increases. Nurses must enhance their patient-education and telephone symptom-management skills and help to secure reimbursement for such activities.

Influence of the antacid Maalox on the pharmacokinetics of capecitabine in cancer patients

PURPOSE

In the present study the possible influence of the antacid Maalox on the pharmacokinetics of capecitabine (Xeloda) and its metabolites was investigated in cancer patients.

METHODS

A total of 12 patients with solid, predominantly metastatic tumors of various origin received a single oral dose of 1250 mg/m2 of capecitabine (treatment A), a single oral dose of 1250 mg/m2 of capecitabine followed immediately by 20 ml of Maalox (treatment B), and a single oral dose of 1250 mg/m2 of capecitabine followed 2 h later by 20 ml of Maalox (treatment C) in an open, randomized, three-way cross over fashion. Serial blood and urine samples were collected for up to 24 h after each administration. Unchanged capecitabine and its metabolites were analyzed in plasma using liquid chromatography/mass spectrometry and in urine using nuclear magnetic resonance spectroscopy.

RESULTS

Administration of Maalox either concomitantly with capecitabine or delayed by 2 h did not influence the time to peak plasma concentrations (Cmax) or the elimination half-lives of capecitabine and its metabolites. Unexpectedly, moderate increases in the Cmax and AUC0-infinity values obtained for capecitabine and 5'-deoxy-5-fluorocytidine were observed when Maalox was given together with capecitabine. However, these increases, which ranged between 10% and 31%, were not statistically significant (P > 0.05) and are not of clinical significance. There was no indication of consistent changes in the plasma concentrations of the other metabolites 5'-deoxy-5'-fluorouridine (5'-DFUR), 5-fluorouracil, and alpha-fluoro-beta-alanine. The Cmax and AUC0-infinity values recorded for these three metabolites increased and decreased in a stochastic manner. The magnitude of these changes was low (<13%) and not statistically significant. The primary statistical analysis of the AUC0-infinity obtained for 5'-DFUR provided a P value of 0.4524 and clearly indicated no significant difference between the treatments. The addition of Maalox had no influence on the overall urinary recovery or the proportion of the dose recovered as capecitabine or its metabolites from urine.

CONCLUSION

At the dose used in this study, the effect of concomitantly delivered Maalox on the extent and rate of gastrointestinal absorption of capecitabine is not clinically significant. Therefore, there is no need to adjust the dose or timing of capecitabine administration in patients treated with Maalox.

[Mechanism and possible biochemical modulation of capecitabine (Xeloda), a newly generated oral fluoropyrimidine]

A new 5-FU analog, Capecitabine (Xeloda; N-[1-(5-deoxy-b-D-ribofuranosyl)-5-fluoro-1, 2-dihydro-2-oxo-4-pyrimidyl]-n-penyl carbamate), was generated to decrease the incidence of GI toxicity and to increase the efficacy. Capecitabine is designed as a prodrug of 5'-deoxy-5-fluorouridine (5'-DFUR), which is clinically used for gastric, breast and colorectal cancer patients undergoing single or combination chemotherapy in Japan. Capecitabine was converted to 5'-DFUR by either human carboxyestelase or cytidine deaminase, which were mainly localized in human liver. 5'-DFUR was converted to the active form of 5-FU by thymidine phosphorylase (dThdPase) in human tumors. The expression of dThdPase was higher in malignant tumors than in noninvolved normal tissues. In this regard, a high concentration of either 5'-DFUR or 5-FU in malignant tumors may be obtained by oral administration of Capecitabine. In addition, in vivo study showed synergistic or additive effects of Capecitabine combined with anti-cancer agents (Taxanes, Mitomycin C or Cyclophosphamide), cytokines, growth factors and hormonal agents. Capecitabine may be biochemically modulated by those agents in vivo. In the results of an early phase II study on breast cancer patients in Japan, a high efficacy rate and low toxicity were observed. Also, Capecitabine was already registered as 2nd- or 3rd-line treatments for breast cancer patients by the Food & Drug Administration of the USA. Capecitabine is one of the most promising orally administered 5-FU analogs.

Multicenter phase II study of capecitabine in paclitaxel-refractory metastatic breast cancer

PURPOSE

Capecitabine is a novel, oral, selectively tumor-activated fluoropyrimidine carbamate. This large multicenter phase II trial tested the efficacy and safety of twice-daily oral capecitabine at 2,510 mg/m2/d given for 2 weeks followed by a 1-week rest period and repeated in 3-week cycles, in patients with paclitaxel-refractory metastatic breast cancer.

PATIENTS AND METHODS

Patients were to have received at least two but not more than three prior chemotherapeutic regimens, one of which had to have contained paclitaxel given for metastatic disease. One hundred sixty-three patients were entered onto the study at 25 centers, and 162 patients received capecitabine. One hundred thirty-five patients had bidimensionally measurable disease, and 27 patients had assessable disease.

RESULTS

The overall response rate was 20% (95% confidence interval, 14% to 28%). All responding patients were resistant to or had failed paclitaxel, and all had received an anthracycline. Three complete responses were seen, with complete response durations of 106, 109, and 194+ days. Median duration of response was 8.1 months, median survival time was 12.8 months, and the median time to disease progression was 93 days. The most common treatment-related adverse events were hand-foot syndrome, diarrhea, nausea, vomiting, and fatigue. Diarrhea (14%) and hand-foot syndrome (10%) were the only treatment-related adverse events that occurred with grade 3 or 4 intensity in more than 10% of patients.

CONCLUSION

Capecitabine is an active drug in the treatment of paclitaxel-refractory metastatic breast cancer. It has a favorable toxicity profile with the added advantage of being an oral drug administered at home.

A Phase I study of capecitabine in combination with oral leucovorin in patients with intractable solid tumors

Capecitabine (Xeloda) is a novel rationally designed fluoropyrimidine carbamate. It passes through the intestinal mucosal membrane intact and is subsequently activated by a cascade of three enzymes resulting in preferential release of 5-fluorouracil (5-FU) at the tumor site. Preclinical studies indicated an enhancement of the therapeutic index when capecitabine was combined with leucovorin. This Phase I trial was designed to determine the safety profile, maximal tolerated dose, and pharmacokinetic profile of the combination of capecitabine plus a fixed dose of p.o. leucovorin (60 mg/day) during administration to patients with refractory advanced cancers. The intention was to administer both drugs continuously, but the starting dose of capecitabine was also the maximum tolerated dose (1004 mg/m2/day) in six patients treated with this regimen. A cycle of treatment was then redefined as leucovorin and capecitabine given p.o., twice daily for 2 consecutive weeks followed by a 1-week rest period. Capecitabine doses from 1004 mg/m2/day to 2510 mg/m2/day were evaluated with the intermittent schedule over approximately 80 courses in an additional 25 patients. The dose-limiting toxicities that defined the maximum tolerated dose at 2000 mg/m2/day were diarrhea, nausea, vomiting, and palmar plantar erythrodysesthesia. The recommended Phase II dose using this schedule was 1650 mg/m2/day of capecitabine plus leucovorin 60 mg/day. Plasma concentrations of capecitabine, intermediate metabolites, and 5-FU were measured in 26 patients on days 1 and 14 of therapy. The pharmacokinetics of capecitabine were characterized by rapid GI absorption, with Cmax at 1 h, followed by conversion to active drug. The coadministration of leucovorin had no effect on the pharmacokinetics of capecitabine. Two patients with colorectal cancer, both previously treated with 5-FU, had partial responses. Phase II studies have confirmed the promising antitumor activity of this drug, and capecitabine is currently in Phase III evaluation.

Chemotherapy for gastric carcinoma: new and old options

Although gastric carcinoma is an uncommon disease in North America, its incidence is alarmingly high in Asia, South America, Eastern Europe, and countries of the former Soviet Union. Screening for gastric carcinoma is performed only on a limited basis in Japan; in the rest of the world, therefore, patients often present with advanced disease at the time of diagnosis. Chemotherapy, radiotherapy, or both rarely cure patients with unresectable or metastatic carcinoma; therapy thus remains palliative for such patients. Chemotherapy seems to be beneficial, however, and continues to evolve in the treatment of patients with advanced gastric carcinoma. Four small randomized trials demonstrated survival and quality-of-life benefits for patients who received chemotherapy compared with those who received best supportive care. In the past 20 years, several "old" drugs have been studied either alone or in combination to treat this disease; and new active drugs have been identified. Recently, quality of life, convenience, and cost-containment have been emphasized in the treatment of cancer. This has increased interest in oral agents. At present, several promising oral 5-fluorouracil prodrugs are being studied in clinical trials. This article summarizes current developments in the treatment of advanced gastric carcinoma.

The oral fluorouracil prodrugs

Discussed herein are selected oral fluorinated pyrimidines that are converted to 5-fluorouracil (5-FU) in vivo to exert antitumor activity. These agents include capecitabine (Xeloda), tegafur-uracil (UFT) plus leucovorin (Orzel), and S-1 (BMS247616). These agents offer the convenience of an orally administered therapy with potentially fewer toxic effects than conventional bolus regimens of 5-FU plus leucovorin. These oral agents provide prolonged 5-FU exposure at lower peak concentrations than observed with bolus intravenous administration of 5-FU and may confer pharmacoeconomic advantages by reducing administration costs and toxicity-related hospitalizations. These regimens also have the potential for improved therapeutic activity by achieving higher 5-FU concentrations in the tumor or by biochemically modulating 5-FU. Phase III trials in patients with advanced colorectal carcinomas are comparing the antitumor activity of these agents with that of intravenous 5-FU plus leucovorin.

Oral 5-FU analogues in the treatment of breast cancer

Three oral 5-fluorouracil (5-FU) therapies have been approved by the US Food and Drug Administration or are in development for the treatment of patients with breast cancer: capecitabine, UFT, and 5-FU/eniluracil. Capecitabine has been approved for breast cancer patients whose disease is paclitaxel-resistant, and either anthracycline-resistant or for whom further anthracycline use is not indicated. A response rate of 20% was observed in an open-label phase II trial of capecitabine in heavily pretreated patients with metastatic breast cancer. Diarrhea and hand-foot syndrome were the most frequently reported toxicities. In a randomized phase II study of capecitabine vs paclitaxel in breast cancer patients who had failed anthracyclines, response rates were 36% for capecitabine vs 21% for paclitaxel. Several phase II trials of 5-FU/eniluracil in breast cancer are ongoing. Preliminary response data from one of these trials on 31 patients with anthracycline- and taxane-resistant advanced breast cancer showed a 16% partial response rate. Grade 3-4 treatment-related toxicities included diarrhea (8%), nausea (3%), and granulocytopenia (3%). In Japan, UFT is widely used for the treatment of breast cancer in both the adjuvant and metastatic settings, though studies in the United States are just getting under way. A phase II trial conducted in Madrid, Spain evaluated the combination of UFT, methotrexate, and leucovorin as salvage therapy for breast cancer patients. The overall response rate was 38% among 21 patients, and diarrhea was the most common toxicity. Many questions remain unanswered about the optimal use of oral 5-FU agents in breast cancer. There seems little question that these agents have substantial activity and will find a place in the therapeutic armamentarium.

Phase I and pharmacologic study of intermittent twice-daily oral therapy with capecitabine in patients with advanced and/or metastatic cancer

PURPOSE

Capecitabine is an orally administered fluoropyrimidine carbamate selectively activated to fluorouracil (5-FU) in tumors. It passes through the intestinal mucosal membrane intact and is subsequently activated by a cascade of three enzymes that results in the preferential release of 5-FU at the tumor site.

PATIENTS AND METHODS

In this phase I study, capecitabine was administered twice daily as outpatient therapy, each cycle administered for 2 weeks followed by 1 week of rest. Thirty-four patients with solid tumors, all of whom except three patients were pretreated, were treated at dose levels from 502 to 3,514 mg/m2 daily.

RESULTS

The median treatment duration was four cycles (85 days; range, 14 to 833+ days). Two patients continue on treatment at 686 and 833+ days. Capecitabine 3,000 mg/m2 daily was not tolerable, with dose-limiting toxicities of diarrhea with hypotension, abdominal pain, and leukopenia. Palmar-plantar erythrodysesthesia (PPE) became evident at higher dose levels after prolonged treatment. Evidence of objective tumor response was reported in four patients at 2,510 mg/m2 daily and greater (one complete response [CR] and three partial responses [PRs]) with subjective minor tumor responses in a further seven patients. Pharmacokinetic studies showed rapid gastrointestinal absorption of capecitabine, followed by extensive conversion into 5'-deoxy-5-fluorouridine (5'-DFUR), with only low systemic 5-FU levels.

CONCLUSION

Capecitabine is a tolerable oral outpatient therapy that shows promising clinical activity in a variety of cancers. The recommended phase II dose is 2,510 mg/m2 daily administered by this intermittent schedule.

Oral fluoropyrimidines in the treatment of colorectal cancer

5-Fluorouracil (5-FU) has been the mainstay of systemic therapy for colorectal cancer since its initial development 40 years ago. Efforts to improve the therapeutic index of 5-FU have included alteration of schedule and addition of biochemical modulators. An understanding of 5-FU mechanisms of action has resulted in major therapeutic advances in the past 10 years; however, a plateau has been reached in the efficacy of 5-FU, mandating a paradigm shift for those involved in colorectal cancer drug development. One direction vigorously pursued is the development of orally administered fluoropyrimidines that maintain or improve upon the effectiveness of intravenous 5-FU. In this paper the preclinical and clinical development of oral fluoropyrimidines and their modulators is reviewed, including UFT, capecitabine, ethynyluracil and S-1.

New drugs in the treatment of colorectal carcinoma

BACKGROUND

Treatment with 5-fluorouracil (5-FU) plus leucovorin has been the unofficial standard therapy for patients with colorectal carcinoma (CRC) for more than a decade; however, the optimal dose and schedule remain a matter of debate. Recently several new drugs have shown activity in this disease. These include irinotecan (CPT-11); oxaliplatin; the thymidylate synthase inhibitors raltitrexed, uracil/tegafur (UFT), capecitabine, and S-1; the biochemical modulators trimetrexate and 5-ethynyluracil; and the monoclonal antibody 17-1A.

METHODS

The results of clinical trials with these and other new agents, as well as their current status and main characteristics, were reviewed.

RESULTS

Several of these agents, some with a novel mechanism of action, show promising activity in CRC. In combination with 5-FU and leucovorin, trimetrexate showed encouraging response rates in Phase II studies. Other interesting agents include capecitabine, UFT, and S-1. The biochemical modulator 5-ethynyluracil may allow the oral administration of 5-FU; however, results of Phase II clinical trials are not yet available. CPT-11 is in the most advanced stage of development and, based on consistent data generated in extensive Phase II studies, currently appears to be a reasonable choice for 5-FU-resistant or refractory disease. Another promising agent is oxaliplatin, which showed activity as first-line and second-line treatment.

CONCLUSIONS

Several new agents have shown promise in the treatment of CRC, and changes in the standard treatment of advanced or high risk CRC appear likely in the near future.

Antitumor activities of a novel fluoropyrimidine, N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine (capecitabine)

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel fluoropyrimidine carbamate that was synthesized for the purpose of finding antitumor drugs with improved safety and efficacy profiles compared with those of 5-fluorouracil (5-FUra) and doxifluridine (5'-deoxy-5-fluorouridine, 5'-dFUrd). The present study compared the antitumor activities of the compound with those of other fluoropyrimidines in 12 human cancer xenograft models and their antimetastatic activities in murine tumor models. The antitumor efficacy of capecitabine was greater than those of 5'-dFUrd, UFT (a mixture of tegafur and uracil) and 5-FUra. Capecitabine was also much safer, particularly much less toxic to the intestinal tract, than the other compounds, indicating higher therapeutic indices. The therapeutic indices of capecitabine, 5'-dFUrd and 5-FUra were >40, >20 and 2.0 against the human CXF280 colon cancer xenograft, the most sensitive line to the fluoropyrimidines so far tested, and 5.1, 1.5, and <1.5 against the human HCT116 colon cancer xenograft with ordinary sensitivity, respectively. In addition, capecitabine, as well as 5'-dFUrd, selectively suppressed the spontaneous metastasis of mouse Lewis lung carcinoma in mice at extremely low doses, 32-64 fold lower than their minimum effective dose (MED) against the primary tumor growth. Capecitabine was even more antimetastatic than 5'-dFUrd. These results indicate that capecitabine has high therapeutic potential.

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

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel oral fluoropyrimidine carbamate, which is converted to 5-fluorouracil (5-FU) selectively in tumours through a cascade of three enzymes. The present study investigated tissue localisation of the three enzymes in humans, which was helpful for us to design the compound. Carboxylesterase was almost exclusively located in the liver and hepatoma, but not in other tumours and normal tissue adjacent to the tumours. Cytidine (Cyd) deaminase was located in high concentrations in the liver and various types of solid tumours. Finally, thymidine phosphorylase (dThdPase) was also more concentrated in various types of tumour tissues than in normal tissues. These unique tissue localisation patterns enabled us to design capecitabine. Oral capecitabine would pass intact through the intestinal tract, but would be converted first by carboxylesterase to 5'-deoxy-5-fluorocytidine (5'-dFCyd) in the liver, then by Cyd deaminase to 5'-deoxy-5-fluorouridine (5'-dFUrd) in the liver and tumour tissues and finally by dThdPase to 5-FU in tumours. In cultures of human cancer cell lines, the highest level of cytotoxicity was shown by 5-FU itself, followed by 5'-dFUrd. Capecitabine and 5'-dFCyd had weak cytotoxic activity only at high concentrations. The cytotoxicity of the intermediate metabolites 5'-dFCyd and 5'-dFCyd was suppressed by inhibitors of Cyd deaminase and dThdPase, respectively, indicating that these metabolites become effective only after their conversion to 5-FU. Capecitabine, which is finally converted to 5-FU by dThdPase in tumours, should be much safer and more effective than 5-FU, and this was indeed the case in the HCT116 human colon cancer and the MX-1 breast cancer xenograft models.

Preliminary studies of a novel oral fluoropyrimidine carbamate: capecitabine

PURPOSE

To evaluate the toxicology and pharmacology of an orally active fluoropyrimidine given as a continuous daily dose divided into two portions for 6 weeks, and to determine the maximal-tolerated daily dose (MTD) and the suggested phase II daily dose.

PATIENTS AND METHODS

Solid-tumor patients with a Karnofsky performance status greater than 70 who had normal organ function and resolution of the effects of prior therapy, and who gave informed written consent, were enrolled. Oral capecitabine, as a divided morning and evening dose, was administered to cohorts of a minimum of 3 patients starting at 110 mg/m2 and escalating by means of a modified Fibonacci scheme to 1,657 mg/m2/d. Pharmacologic samples were obtained on days 1 and 15. Toxicity evaluations were performed approximately every 3 days for the first 43 days. Antitumor effect was evaluated at day 42 of therapy.

RESULTS

Thirty-three patients entered the study. Few side effects occurred at or below 1,331 mg/m2/d. The MTD was 1,657 mg/m2/d with limiting toxicities of palmar-plantar erythrodysesthesia, nausea, vomiting, vertigo, abdominal pain, diarrhea, and thrombocytopenia. All toxicities were reversible. A mixed response was seen in one breast cancer patient. Pharmacologic studies showed rapid and extensive metabolism of the parent drug into cytotoxic metabolites with a maximum plasma concentration (Cmax) 1 hour after ingestion. Linear increases in the area under the concentration-time curve (AUC) and Cmax were seen with linear increases in administered dose.

CONCLUSION

The suggested phase II dose on a continuous 42-day dosing schedule is 1,331 mg/m2/d. Linear pharmacologic parameters of the parent compound and metabolites are demonstrated.

Tumor selective delivery of 5-fluorouracil by capecitabine, a new oral fluoropyrimidine carbamate, in human cancer xenografts

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel fluoropyrimidine carbamate that is converted to 5-fluorouracil (5-FUra) by three enzymes located in the liver and tumors; the final step is the conversion of 5'-deoxy-5-fluorouridine (5'-dFUrd) to 5-FUra by thymidine phosphorylase in tumors. The present study compared the efficacy of capecitabine and 5-FUra at their maximum tolerated doses in CXF280, HCT116, COLO205, and WiDr human colon cancer xenograft models, and measured subsequent 5-FUra and 5'-dFUrd levels in tumors and in the plasma and muscle. Capecitabine was effective in the first three models, whereas 5-FUra was effective only in CXF280, which is a cell line highly susceptible to fluoropyrimidines. In the three susceptible models, 5-FUra AUCs in tumors after capecitabine administration were 210 to 303 nmol x hr/g, whereas those after 5-FUra administration were 8.54 to 13.1 nmol x hr/g. In addition, capecitabine gave higher levels of 5-FUra AUC in tumors than in plasma (114- to 209-fold higher) and muscle (21.6-fold higher), whereas 5-FUra was not selectively distributed to tumors. In the refractory model, WiDr, 5-FUra AUC in tumors after capecitabine administration was only 62.8 nmol x hr/g, although the level of the intermediate metabolite 5'-dFUrd was high (AUC: 695 nmol x hr/g). The ratio of 5-FUra/5'-dFUrd levels in the WiDr tumors was 0.09, which was 23.8-fold lower than that in the HCT116 tumors. The mechanism of resistance would be the inefficient conversion of 5'-dFUrd to 5-FUra by thymidine phosphorylase in tumors. Thus, capecitabine might show its high efficacy as a result of delivering high levels of 5-FUra selectively to the tumors.

Effect of food on the pharmacokinetics of capecitabine and its metabolites following oral administration in cancer patients

Capecitabine (Ro 09-1978) is a novel oral fluoropyrimidine carbamate that was rationally designed to generate 5-fluorouracil (5-FU) selectively in tumors. The effect of food on the pharmacokinetics of capecitabine and its metabolites was investigated in 11 patients with advanced colorectal cancer using a two-way cross-over design with randomized sequence. Patients received repeated doses of 666 or 1255 mg/m2 of capecitabine twice daily. On study days 1 and 8, drug was administered following an overnight fast or within 30 min after consumption of a standard breakfast, and serial blood samples were collected. Concentrations of capecitabine and its metabolites [5'-deoxy-5-fluorocytidine (5'-DFCR), 5'-deoxy-5-fluorouridine (5'-DFUR), 5-FU, dihydro-5-fluorouracil (FUH2), and alpha-fluoro-beta-alanine (FBAL)] in plasma were determined by high-performance liquid chromatography or liquid chromatography/mass spectroscopy. Intake of food prior to the administration of capecitabine resulted in pharmacokinetic changes of all compounds involved. The extent of these changes, however, varied considerably between the various compounds. Maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) values were decreased after food, and time until the occurrence of Cmax values were increased. In contrast, the apparent elimination half-life was not affected by food intake. The extent of change in Cmax and AUC was highest for capecitabine and decreased with the order of formation of the metabolites. The "before:after food" ratios of the Cmax values were 2.47 for capecitabine, 1.81 for 5'-DFCR, 1.53 for 5'-DFUR, 1.58 for 5-FU, 1.26 for FUH2, and 1.11 for FBAL. The before: after food ratios of the AUC values were 1.51 for capecitabine, 1.26 for 5'-DFCR, 1.15 for 5'-DFUR, 1.13 for 5-FU, 1.07 for FUH2, and 1.04 for FBAL. The results show that food has a profound effect on the AUC of capecitabine, a moderate effect on the AUC of 5'-DFCR, and only a minor influence on the AUC of the other metabolites in plasma. In addition, a profound influence on Cmax of capecitabine and most of its metabolites was found. Detailed information on the relationship between concentration and safety/efficacy is necessary to evaluate the clinical significance of these pharmacokinetic findings. At present, it is recommended that capecitabine be administered with food as this procedure was used in the clinical trials.

Induction of thymidine phosphorylase activity and enhancement of capecitabine efficacy by taxol/taxotere in human cancer xenografts

Thymidine phosphorylase (dThdPase) is an essential enzyme for the activation of the cytostatics capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) and its intermediate metabolite [5'-deoxy-5-fluorouridine (5'-dFUrd)] to 5-fluorouracil in tumors. We have tried to identify the best partners of capecitabine in combination therapy, such as dThdPase up-regulators, which may enhance the efficacy of this compound. Among various cytostatics studied with the WiDr human colon cancer xenograft model, Taxol, Taxotere, and mitomycin C greatly increased levels of human dThdPase in tumors, and cyclophosphamide slightly increased the enzyme level. These cytostatics simultaneously increased the levels of human tumor necrosis factor alpha (TNFalpha), which is an up-regulator of dThdPase. In cultures of the WiDr cells, however, Taxol did not up-regulate TNFalpha to a detectable level and only slightly enhanced levels of dThdPase. These results suggest that Taxol might indirectly elevate TNFalpha in tumor cells, which in turn up-regulated dThdPase in the tumor cells in the WiDr cancer xenograft. In the combination therapy, the efficacy of Taxol and Taxotere with either capecitabine or 5'-dFUrd was more than just additive. In contrast, Taxol and either 5-fluorouracil or UFT (a mixture of tegafur and uracil) in combination showed only additive activity. Taxol and Taxotere might enhance the efficacy of capecitabine and 5'-dFUrd, probably by modulating dThdPase activity in tumor tissues.

Positive correlation between the efficacy of capecitabine and doxifluridine and the ratio of thymidine phosphorylase to dihydropyrimidine dehydrogenase activities in tumors in human cancer xenografts

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a new fluoropyrimidine carbamate, which is converted to 5-fluorouracil (5-FUra) selectively in tumors through the intermediate metabolite 5'-deoxy-5-fluorouridine (5'-dFUrd, doxifluridine). 5'-dFUrd is metabolized to 5-FUra by thymidine phosphorylase (dThdPase) located in high levels in various types of solid tumors from patients, whereas 5-FUra generated is catabolized to dihydrofluorouracil by dihydropyrimidine dehydrogenase (DPD). The present study investigated whether the efficacy of capecitabine and its intermediate metabolite 5'-dFUrd correlates with levels of these enzymes in various human cancer xenograft models. Capecitabine and 5'-dFUrd were highly effective and inhibited tumor growth by more than 50% in 18 of 24 xenograft lines (75%) and 15 of 24 xenograft lines (63%), respectively, whereas 5-FUra and a mixture of tegafur and uracil were effective only in 1 of 24 (4.2%) and 5 of 24 (21%), respectively. The efficacy of capecitabine correlated with dThdPase activity. However, capecitabine was effective even in tumors with lower levels of dThdPase if DPD levels were also lower. In contrast, it was not as effective even in tumors with sufficient levels of dThdPase if DPD levels were very high. The efficacy of capecitabine consequently correlated very well with and depended on the ratio of these two enzymes in tumors. These results indicate that capecitabine might exert its efficacy through 5-FUra generated in tumor tissues but not through that generated in normal organs. On the other hand, there was no correlation between the efficacy of a mixture of tegafur and uracil and these enzyme activities in tumors. The efficacy of capecitabine would be optimized by selecting patients who have tumors with a high ratio of dThdPase to DPD activities.

Advances in the treatment of patients with pancreatic cancer: improvement in symptoms and survival time. The San Antonio Drug Development Team

Pancreatic cancer is a major cause of death from cancer in both men and women in the USA and Europe. The disease causes pain and has a significant impact on the performance status of the patient. In a randomized trial vs 5-fluorouracil, the novel nucleoside analogue gemcitabine (GEMZAR) has been shown to provide clinical benefit for patients (decreased pain and improved performance status) as well as to improve the time to tumour progression and survival for patients with the disease. There are also other new agents that are presented in this discussion, such as the multi-targeted antifolate MTA, capecitabine and the ONYX-015 adenovirus, which replicates in, and kills, only p53-abnormal cells, which have the potential to have an impact on this terrible disease.