Clinical pharmacology of the stereoisomers of leucovorin during repeated oral dosing

Towards voltammetric point of care detection of leucovorin

Current healthcare trends have seen an increased emphasis on the move towards personalised precision medicine to tailor treatments to the individual and their response to diseases and disease therapies. This highlighting a transition from traditional "one size fits all" to a more nuanced approach. Despite advancements in fundamental knowledge to facilitate personalised prevision approaches, lack of resources to implement such plans remains one of the largest hurdles to overcome. Monitoring of drug therapies is one key aspect that could aid in the evolution of precision medicine alongside the development of drugs and targeted treatment systems. This contribution illustrates the potential of square wave voltammetry (SWV) as a proof-of-concept for monitoring of circulating blood concentrations of treatment therapies within artificial urine, using leucovorin calcium (LV) as a model cancer therapy drug. A low cost, easy-to-use and portable sensor has been developed and successfully employed for the detection of LV over the linear range 0.5-30 μM which represents the therapeutically relevant concentrations for LV within artificial urine without any prior sample preparation required with a limit of detection of 2.63 μM and initial investigations into saliva and serum as biological matrices. The developed sensor describe herein exhibits a proof-of-concept for the engagement of such electrochemical sensors as point-of-care devices, where the sensors ease of use and removal of time-consuming and complex sample preparation methods will ultimately increase its usability by physicians, widening the avenues where electrochemical sensors could be employed.

Phase II Trial of Oral Tegafur and Folinic Acid with Mitoxantrone as First-Line Regimen in Patients with Metastatic Breast Cancer

Background

Tegafur acts as a deport form of 5-fluorouracil when administered orally for longs periods of time, since it is an active drug in metastatic breast cancer, with response rates of 29-44%. Biochemical modulation with folinic acid and the addition of mitoxantrone could increase the efficacy of tegafur in patients with metastatic breast cancer.

Methods

A prospective phase II trial in patients with previously untreated metastatic breast cancer was carried out. The scheme consisted of mitoxantrone, 12 mg/m2 intravenous day 1, oral tegafur, 750 mg/m2/day divided in three equal doses, and leucovorin 15 mg/8 h orally for days 1-21, given in a 4-week schedule. None patient had received chemotherapy for metastatic breast cancer, although 16 patients had received previous adjuvant chemotherapy.

Results

Thirty-four patients were included. Objective responses were achieved in 20 of 32 patients assessable for response, with 1 complete response and 19 partial responses. The objective response rate was 62.5% (95% confidence intervals, 48-76%). The median duration of response was 10 months. Grade III-IV toxicity according to WHO criteria was digestive (nausea/vomiting) in 12.5%, diarrhea in 25% and stomatitis in 25% of patients. Other toxicities were low. Eight patients required dose-reduction.

Conclusions

We achieved a significant response rate with the scheme, which was administered on an outpatient basis. It seems to be safe and effective as first-line treatment in metastatic breast cancer, with a short median response duration. The size of the trial does not permit definitive conclusions, and the role of biochemical modulation of tegafur in combination with mitoxantrone remains to be defined.

Medical Management of Colorectal Carcinomas

Current information on the medical treatment of colorectal cancer was reviewed after a search of the literature through Medline. Publications from 1984 to present were surveyed. Appropriate adjuvant therapy increases overall survival and disease-free intervals. The treatment modalities of unresectable or metastatic tumors are disappointing, with at best 40% of patients experiencing short-lasting responses. Whenever possible, patients with advanced colorectal cancer should be enrolled in clinical trials.

Effects of the leucovorin shortage: Pilot study investigating cost, efficacy, and toxicity comparison of low fixed-dose versus body surface area-adjusted leucovorin dosing in patients with resectable colon or metastatic colorectal cancer

Purpose As a result of the leucovorin shortage, we switched from BSA-adjusted to low fixed-dose leucovorin in patients with colon cancer receiving fluorouracil-containing therapy. Methods A retrospective, pilot study of adults receiving intravenous leucovorin as part of a fluorouracil-containing treatment was conducted including individuals with stage II or III colon or newly diagnosed metastatic colorectal cancer. One low fixed-dose (leucovorin 50 mg) patient was matched by the investigator to one BSA-adjusted (leucovorin 200-500 mg/m²/dose) patient on disease stage and age. The objectives were to compare cost of alternative dosing strategies as well as efficacy and adverse event rates. Only patients being treated in the first-line metastatic colorectal cancer setting were included in the efficacy analysis. Results Fifty-eight patients were included. Leucovorin cost was reduced by 7- to 14-fold, and we were able to conserve a total of 1580-3400 doses of leucovorin by changing to fixed-dose (estimated from 200 mg/m² or 400 mg/m² dosing strategies, respectively). No statistically significant differences in progression-free survival ( p = 0.254), overall survival ( p = 0.923), or complications resulted. Conclusion Our decision to reduce the dose of leucovorin allowed us to conserve supply and control cost. The small sample size did not allow us to detect differences in efficacy or adverse event rates, and thus a larger study would be required to confirm our findings that efficacy was not compromised nor adverse effects greater.

Phase II trial of cisplatin, tegafur plus uracil and leucovorin as neoadjuvant chemotherapy in patients with squamous cell carcinoma of the oropharynx and hypopharynx

We evaluated the efficacy and toxicity of cisplatin, tegafur plus uracil and leucovorin as neoadjuvant chemotherapy for locally advanced squamous cell carcinoma (SCC) of the oropharynx and hypopharynx. Forty-six patients (stage IV, 83%; N2/3, 52%) were treated with PUL (50 mg/m2 cisplatin on day 1, 300 mg/m2 tegafur plus uracil orally and 60 mg leucovorin orally on days 1-14) over a 14-day cycle. Evaluation after 3 cycles led to chemotherapy termination if primary tumor responses were less than partial responses. Otherwise, PUL was continued up to 6 cycles before locoregional therapy. Patients achieving at least good partial responses at the primary site after neoadjuvant chemotherapy received radiotherapy for organ preservation. Chemotherapy responses were analyzed by intent-to-treat. Response rates of primary sites were 71.7% (33 of 46) with 34.8% (16 of 46) showing a complete response. Thirty patients (65.2%) achieved good partial responses at the primary site. Overall response and complete response rates of neck lymph nodes were 68.6% (24 of 35) and 25.7% (nine of 35). The combined response rate of primary site and neck lymph nodes was 63% (95% confidence interval 48.5-77.5%) with a complete response rate of 15.2%. Toxicities of WHO grade 3-4 included anemia (19.6%), diarrhea (17.4%) and neutropenia (8.7%). With a median follow-up of 36 months, overall survival and disease-free survival rates were 45.7% (21 of 46) and 41.3% (19 of 46); organ preservation rate was 90% (19 of 21). We concluded that the outpatient PUL regimen was a moderately effective, less-toxic neoadjuvant chemotherapy for SCC of the oropharynx and hypopharynx. PUL should be studied further with other active agents or radiotherapy.

Cisplatin, tegafur, and leucovorin: a moderately effective and minimally toxic outpatient neoadjuvant chemotherapy for locally advanced squamous cell carcinoma of the head and neck

BACKGROUND

To evaluate the efficacy and toxicity of cisplatin, tegafur, and leucovorin as neoadjuvant chemotherapy (CT) for patients with advanced, nonmetastatic squamous cell carcinoma of the head and neck (SCCHN).

METHODS

Patients with SCCHN according to World Health Organization (WHO) performance status of 2 or less and adequate organ function were enrolled. The CT regimen (PTL) was 50 mg/m(2) cisplatin (P) on Day 1, 800 mg per day oral tegafur (T), and 60 mg per day oral leucovorin (L) for 14 days. The CT was administered at outpatient clinics for 14-day cycles. PTL was initiated with the intent of organ preservation and it was continued for a maximum of six cycles before locoregional therapy. Reevaluation after three cycles led to the termination of CT when the response was less than a partial response. CT was discontinued immediately upon evidence of tumor progression or excessive toxicity.

RESULTS

From March 1996 through July 1999, 97 patients were enrolled consecutively. All participants were men with a median age of 56 years (range, 37-70 years). The primary tumor sites were the tongue base, 14, and the hypopharynx, 83. Sixteen percent of the tumors were Stage III, 84% were Stage IV, 62% were Stage T4, and 44% were Stage N2-3. The median number of CT cycles was six. On an intent-to-treat basis, 26 patients (27%) achieved complete responses and 32 patients (33%) achieved partial responses. The overall response rate was 60% (95% confidence interval, 50-70%). The most common toxicities of WHO Grade 3 or higher included (percent of patients): anemia, 8.3%; stomatitis, 6.3%; thrombocytopenia, 3.1%; and vomiting, 3.1%. With a median follow-up period of 3 years, the overall survival and disease-free survival rates were 40% and 38%, respectively. Organ preservation was achieved in 70% (29 of 37) of the surviving patients.

CONCLUSION

The outpatient PTL regimen was a moderately effective and minimally toxic CT for SCCHN. PTL should be studied further in combination with other active agents or radiotherapy for patients with SCCHN.

Separation methods for methotrexate, its structural analogues and metabolites

Methotrexate (MTX) is the prototype folate antagonist cytotoxic drug, employed in the therapy of solid tumors and leukaemias, and recently also as an immunosuppressive agent in organ transplantation, in the treatment of some autoimmune diseases and in the therapy of severe asthma. MTX is one of the very few antineoplastic drugs the therapeutic concentration monitoring of which is currently employed in clinical practice and can be routinely measured in biological samples by a number of different analytical techniques, among which are immunoenzymatic and chromatographic methods. Each technique has of course its own advantages in terms of sensitivity, specificity, speed, cost and level of expertise required. Along with therapeutic drug concentration monitoring and clinical pharmacology, fundamental research into the mechanism of action of antifolate drugs is still a field which requires the measurement of MTX, of its new analogues and of their metabolites in biological samples. This review summarizes the instrumental conditions and the performance of several published chromatographic methods employed to measure MTX, its metabolites and some analogues in clinical and biological research. More than 70 papers describing chromatographic assays for MTX and its metabolites have been published in the literature between 1975 and 2000. A wide array of experimental conditions for sample preparation, analyte separation and detection have been employed. According to their chemical properties, MTX, its metabolites and analogue drugs present in several biological samples (plasma, serum, saliva, urine, cerebrospinal fluid, tissue specimens) can be extracted, separated and detected under a variety of chromatographic conditions, i.e. on different stationary phases, under a wide choice of mobile phase conditions (acidic or neutral, employing ion-pair or micellar chromatography), followed by several detection techniques (UV-Vis spectrophotometry, pre- or post-column oxidation and fluorimetry, electrochemistry, mass spectrometry). Optimized methods allow simultaneous measurement within a few minutes of the plasma levels of MTX and its main metabolites at concentrations in the low-nM range. One special field which needs sensitive, fast and inexpensive methods for the detection and measurement of MTX is the monitoring of contamination in workplace environments, such as pharmaceutical industries and oncological hospital pharmacies, and in sewage waters. The measurement of the intracellular gamma-oligo-glutamate metabolites of biological folates, of MTX and of some analogue drugs is of great importance in basic pharmacological research. The existence of empirical quantitative relationships between the retention of individual oligomers under different chromatographic conditions and the number of added glutamic acid units allows identification of the metabolites even when authentic standards are not available.

Synergistic induction of ICAM-1 expression by cisplatin and 5-fluorouracil in a cancer cell line via a NF-kappaB independent pathway

Cisplatin (CDDP) and 5-fluorouracil (5-FU) are common anti-tumour agents, and the anti-tumour effect of CDDP and 5-FU are synergistically enhanced by combined treatment. To clarify the mechanisms of this synergism, we examined the effect of CDDP and 5-FU on the expression of cell adhesion molecules involved in recognition of cancer cells by T lymphocytes. When NA cells, a squamous cell carcinoma cell line, were exposed to CDDP and 5-FU for 18 h, the expression of intercellular adhesion molecule-1 (ICAM-1) was synergistically induced, whereas CDDP or 5-FU alone did not induce the expression of ICAM-1, as determined by flow cytometry. Expression of ICAM-2 and ICAM-3, which are recognized by the same counter receptor on T-cells, were not up-regulated by CDDP and 5-FU. RT-PCR analysis showed that the induction of ICAM-1 on NA cells might be due to transcriptional induction of ICAM-1 mRNA. Treatment with genistein, a protein tyrosine kinase (PTK) inhibitor, inhibited the induction of ICAM-1 on NA cells by CDDP and 5-FU, whereas staurosporin, a protein kinase C inhibitor, did not. Although CDDP and 5-FU induced binding at the nuclear factor kappa B (NF-kappaB) site in the ICAM-1 promoter, pretreatment with genistein did not prevent CDDP and 5-FU-induced binding at the NF-kappaB site. Moreover, a NF-kappaB nuclear translocation inhibitor did not inhibit the induction of ICAM-1 expression by treatment with CDDP and 5-FU. The synergistic effect of CDDP and 5-FU was not specific to NA cells, since ICAM-1 was synergistically induced by CDDP and 5-FU on HSC-4 cells, a squamous cell carcinoma cell line. These findings indicate that treatment with CDDP and 5-FU induces ICAM-1 expression by a NF-kappaB independent regulatory mechanism involving PTK.

Relief of jaundice by 5-fluorouracil and folinic acid in patients with recurrent gastric cancer

The aim of this study was to evaluate the effect of 5-fluorouracil (5-FU) and folinic acid on liver function and bile production in patients with recurrent gastric cancer and jaundice. Thirteen patients were studied for liver function and hyperbilirubinaemia, and six patients were studied for bile production retrospectively, who were treated with 5-FU [700 mg m(-2)] and folinic acid [20 mg m(-2)] for 4 days. Serum total bilirubin, aspartate aminotransferase (AST), gamma-glutamyl transferase (gamma-GT) and alkaline phosphatase (ALP) concentrations all improved with treatment (P<0.0001), and bile production increased significantly (P<0.0001) following treatment. 5-FU and folinic acid can significantly improve jaundice and liver function, and promote bile production. It is possible that 5-FU and folinic acid may become a new method for the relief of jaundice in patients with gastrointestinal tract malignancies.

Treatment of patients with advanced gastric carcinoma with the combination of etoposide plus oral tegafur modulated by uracil and leucovorin. A phase II study of the ONCOPAZ Cooperative Group

BACKGROUND

Both the biochemical modulation and the continuous administration of 5-fluorouracil (5-FU) have achieved promising results in patients with gastric carcinoma. Conversely, several studies on gastric carcinoma have demonstrated that the combination of etoposide (VP-16), leucovorin (LV), and 5-FU (ELF) is efficacious and moderately toxic. UFT is a combination of uracil and tegafur (ftorafur) in a 4:1 molar ratio. It can be administered orally for several weeks, thus stimulating the effects of a continuous infusion of 5-FU. Its combination with LV increased the efficacy of UFT. We conducted a Phase II study on patients with gastric carcinoma using the combination VP-16-LV-UFT. This combination is administered mainly orally (p.o) and could yield a good response rate and low toxicity.

METHODS

Forty-six patients with bidimensionally measurable disease were entered into the study. Patients received VP-16 100 mg/m2 IV on Day 1 and 200 mg/ m2 p.o. on Days 2 and 3; LV 500 mg/m2 administered intravenously (i.v.) on Day 1, followed by p.o. LV 15 mg every twelve hours on Days 2 to 14. Patients also received UFT p.o. 390 mg/m2/day on Days 1 to 14. Treatment was repeated every 28 days for a minimum of 3 courses per patient. All courses were given on an outpatient basis.

RESULTS

Four patients (9%) had a complete response, and 12 a partial response (26%) for an overall response rate of 35% (95% confidence interval: 22-51%). The median duration of response was 10 months. The median overall survival was 9 months. The main side effects were gastrointestinal. Grade 3 to 4 toxicity was encountered as follows: diarrhea in 17% of the patients, nausea/vomiting in 11%, anemia in 13%, mucositis and leukopenia in 4% each, and thrombocytopenia in 2%. One patient died of sepsis and neutropenia.

CONCLUSIONS

VP-16-LV-UFT has an activity comparable to that of other schemes and a low incidence of side effects. Furthermore, since it is administered mainly orally, hospitalization is avoided, which makes this scheme suitable for patients with advanced gastric carcinoma.

Enantioselective assays in comparative bioavailability studies of racemic drug formulations: nice to know or need to know?

The importance of enantiospecific assays in studying pharmacokinetic/pharmacodynamic (PK/PD) and drug-drug interactions of racemic drugs is widely recognized. Use of such assays in comparative bioavailability studies, however, remains controversial. This commentary proposes a PK/PD-based rationale for deciding whether an enantioselective assay is important in such studies. Racemic drugs are divided into three major categories: those with negligible or nonenantioselective first-pass metabolism (category I), those where the first-pass metabolism of the less-active enantiomer is predominant (category II), and those where the first-pass metabolism of the more active and/or toxic enantiomer is predominant (category III). In addressing the need for assay selectivity, a simple analogy is made between these drug categories and the protein-binding phenomenon. Enantioselective assays are not essential for category I drugs, or for category II drugs in the majority of cases. A special consideration, however, is needed for those category II drugs that undergo racemic inversion that may be influenced by the dose level and/or the residence time of the drug formulation in the gastrointestinal tract. It is with category III drugs that enantioselective assays become important, especially when metabolism, distribution, and/or elimination processes of the active or toxic enantiomer are saturable, leading to variable enantiomeric ratios in the plasma. Factors contributing to these ratio changes include routes of administration, dose level, and input rate differences. In put rate differences are particularly relevant to bioavailability evaluation of category III drugs.

A phase II trial of 5-fluorouracil and 1-leucovorin in patients with metastatic colorectal cancer

We undertook a multicenter phase II trial of 5-fluorouracil (5FU) + 1-leucovorin (1-LV) in previously untreated patients with metastatic colorectal cancer to determine the response rate, response duration, time to progression, survival, and toxicity. Patients were treated with i.v. 5FU 370 mg/m2/day and 1-LV 100 mg/m2/day x 5 every 28 days. Toxicity and response were determined by WHO criteria. One hundred and twenty-six patients were entered, and 119 patients were eligible and evaluable. Eighty-eight patients had colon cancer and 37 had rectal cancer. The male:female ratio was 58:68. The mean age was 62.2 years. ECOG performance status distribution was 0 (39.7%), 1 (46%), and 2 (11.9%). The median number of courses of therapy administered was 4.5. Severe- or life-threatening stomatitis or diarrhea, nausea, and granulocytopenia occurred in 17.6, 23.2, 17.6, and 15.9% of patients, respectively. The response rate was 22/119 [18.5%; 95% confidence interval (CI) of 12.0-26.6]. Median response duration was 188 days (95% CI of 111-248 days). Median survival was 379 days (95% confidence interval of 289-452 days). These results indicate that when 1-LV is combined with 5FU, toxicity is similar in pattern and severity to that of the d,1 racemic mixture. The overall efficacy of 1-LV + 5FU is comparable to a recent metaanalysis.

Efficacy of oral tegafur modulation by uracil and leucovorin in advanced colorectal cancer. A phase II study

A phase II study was performed to assess the efficacy and toxicity of UFT (tegafur-uracil in the molar ratio 1:4) modulated with leucovorin (LV) in previously untreated patients with advanced colorectal carcinoma (CRC). 79 patients with measurable advanced colorectal cancer (CRC) and no prior chemotherapy were included. 75 patients were evaluable for toxicity and response. The regimen consisted of LV 500 mg/m2 administered intravenously on day 1, followed by oral UFT 390 mg/m2 on days 1-14. Patients received oral LV 15 mg every 12 h on days 2-14. Treatment was repeated every 28 days for a minimum of four courses per patient. Three hundred and ninety-eight cycles of chemotherapy were delivered (median five per patient). 7 patients (9%) had a complete response, and 22 a partial response for an overall response rate of 39%. Mild gastrointestinal toxicity was dose limiting: grade 3-4 diarrhoea appeared in 9% of patients. Other grade 3-4 toxicities were nausea/vomiting and mucositis in 4% of patients, gastric pain and leucopenia in 3%. Oral UFT modulated by oral LV is active in advanced CRC and can be administered on an outpatient basis with no significant toxicity requiring hospitalisation. Given its excellent tolerance profile and low toxicity, the regimen should be thoroughly studied and compared with 5-fluorouracil modulated by LV.

Disposition of 5-formyl- and 5-methyltetrahydrofolic acid in serum after i.v. bolus of calcium folinate: pharmacokinetic drug interaction with preadministered interferon-alpha-2b

The influence of interferon (IFN) coadministered subcutaneously with the biomodulating agent folinic acid on the blood serum levels of 5-formyl-tetrahydrofolic acid (CHO-THFA) and the biotransformation into its main metabolite in the blood 5-methyltetrahydrofolic acid (CH3-THFA) was studied in patients receiving a chemotherapy with 5-fluorouracil. IFN causes a clear decrease of the serum concentrations of CHO-THFA and a statistically significant decrease of CH3-THFA concentrations (P < 0.01). The effect on serum concentrations could be observed in each patient, but in a different order of magnitude. As a consequence, the preadministration of IFN leads to a significant change in the basic pharmacokinetic parameters of both compounds: the mean area under the concentration-time curve is decreased at 27.4% for CHO-THFA (P < 0.025) and at 22.4% for CH3-THFA (P < 0.025), respectively. The total body clearance is elevated at 45.4% for CHO-THFA (P < 0.05) and at 23.4% for CH3-THFA (P < 0.05). The mean volume of distribution is increased by IFN at 38.2% for CHO-THFA (P < 0.025) and at 22.3% for CH3-THFA (P < 0.05). The nearly identical mean residence time in both groups indicates that CHO-THFA elimination is not affected by IFN. But the results prove a certain interaction between IFN and CHO-THFA. IFN accelerates the distribution of CHO-THFA as well as of its main metabolite from the blood into the tissue or activates the biotransformation of CHO-THFA into CH3-THFA inside the cells of the tissue. The extent of biotransformation of CHO-THFA into CH3-THFA, which takes place in the blood, is not influenced by IFN because percentage AUC-ratios CHO-THFA:CH3-THFA were 89.5:10.5% for the control group and 88.8:11.2% for the IFN group.

Highly sensitive coupled-column high-performance liquid chromatographic method for the separation and quantitation of the diastereomers of leucovorin and 5-methyltetrahydrofolate in serum and urine

A column-switching chiral HPLC assay was developed that allows the separation and quantitation of the diastereomers of leucovorin (LV, 5-formyltetrahydrofolic acid) and its metabolite 5-methyltetrahydrofolate (METHF) in serum and urine by means of fluorescence detection. The analysis procedure consists of an on-line concentration of the folates in the HPLC system which is followed by the elution and separation of folates on an achiral 3-microns Microbore C18 column in (6R,S)-LV and (6R,S)-METHF. (6R,S)-LV and (6R,S)-METHF are subsequently transferred on-line onto a chiral 7-microns bovine serum albumin column through a Rheodyne valve system and are separated into their diastereometers. Time of analysis is 70 min. Detection limit is 5 ng/ml for each diastereometer. The within-day variation ranges between 3.2 and 15.8% in relation to the measured concentration. Between-day variation is 4.4-12.1% for a concentration of 100 ng/ml for each diastereometer. (6R,S)-LV and (6S)-LV pharmacokinetics were assessed by analyzing serum and urine samples of four-healthy volunteers.

Phase II trial of an all-oral regimen of tegafur and folinic acid in patients with previously treated metastatic breast cancer

BACKGROUND

Tegafur is an antimetabolite slowly metabolized to 5-fluorouracil in vivo. Protracted administration of oral tegafur is active in metastatic breast cancer, with reported response rates ranging from 29 to 44%. The addition of folinic acid could improve the efficacy of tegafur by means of biochemical modulation.

METHODS

A prospective Phase II trial in patients with pretreated metastatic breast cancer was performed. The regimen consisted of oral tegafur (750 mg/m2/day) and oral folinic acid (45 mg/day) for 21 days, recycling at day 28.

RESULTS

Twenty-five patients were included. Eight partial responses were observed for an objective response rate of 32% (95% confidence intervals for response, 23-41%). The median duration of response was 7 months. According to WHO criteria, 24% of patients experienced grade 3 mucositis and 12% grade 3 diarrhea, but no other significant toxicities were observed. Twenty-eight percent of patients required dose reductions for toxicity.

CONCLUSIONS

A significant response rate with oral tegafur and folinic acid in patients with heavily pretreated breast cancer was found. This all-oral regimen, which could be safely administered on an outpatient basis, deserves further evaluation to define the role of folinic acid on the activity of tegafur in metastatic breast cancer.

A phase I trial of immediate postoperative intraperitoneal floxuridine and leucovorin plus systemic 5-fluorouracil and levamisole after resection of high risk colon cancer

BACKGROUND

The purpose of this study was to evaluate the toxicity of immediate postoperative intraperitoneal (IP) floxuridine (FUdR) and leucovorin (LV) after resection of high risk colon cancer, and to determine the appropriate dose of intravenous fluorouracil (FU) plus levamisole during concurrent intraperitoneal therapy.

METHODS

The authors conducted a tertiary referral Comprehensive Cancer Center Phase I Trial in patients with resected colon cancer at high risk for recurrence. After resection of all gross disease, intraperitoneal treatment was administered twice daily for 3 days every 2 weeks for three cycles (Days 1-3, 15-17, 29-31). Intravenous FU daily for 5 days was administered on days 29-33 concurrently with the third cycle of intraperitoneal therapy. Fluorouracil doses during the last cycle of intraperitoneal therapy were escalated; intraperitoneal FUdR and LV doses and weekly intravenous FU doses (starting on Day 58) were fixed.

RESULTS

Twenty-six patients with resected high risk colon cancer were treated. Three had Dukes' B2, 16 Dukes' C, and 7 Dukes' D (M1) resected tumors. Intraperitoneal therapy was well tolerated with no increase in operative morbidity and no operative mortality. Two patients had > or = Grade 3+ toxicity during IP therapy alone. There were no treatment related deaths. During concurrent intraperitoneal and intravenous chemotherapy, the maximum tolerated dose of FU was 300 mg/m2/day for 5 days. The recommended dose for Phase II or III trials is 200 mg/m2/day for 5 consecutive days. Pharmacokinetic analysis indicated that using the doses used in this trial, measurable systemic concentrations of FUdR and LV were obtained during IP therapy. This may have contributed to observed toxicity with intravenous FU doses of 300-400 mg/m2. With a median duration of follow-up of 18 months, four patients had recurrence of disease. No peritoneal recurrences have been noted to date.

CONCLUSIONS

Immediate postoperative IP FUdR and LV are well tolerated after resection of high risk colon cancer. The recommended dose of intravenous FU beginning on Day 29 (concurrent with the last dose of IP therapy) is 5FU 200 mg/m2 for 5 consecutive days. The remaining year of adjuvant fluorouracil and levamisole can be administered with standard dose attenuation. Although follow-up is short, the lack of recurrent peritoneal metastases is encouraging. Additional trials with this approach are warranted in patients with high risk colorectal cancer.

Pharmacokinetics of folinic acid and 5-methyltetrahydrofolic metabolite after repeated oral administration of calcium folinate following methotrexate treatment

The pharmacokinetic profiles of folinic acid (FA) and its active metabolite, 5-methyltetrahydrofolic acid, were studied after oral administration of decreasing doses of calcium folinate during 37 courses of high and intermediate dose methotrexate treatment in 25 lymphoma patients. FA was administered at a dose of 6 x 50 mg in 15 courses, 6 x 25 mg in seven courses, 6 x 15 mg in 10 courses and 6 x 7.5 mg in 5 courses. FA, 5-methyltetrahydrofolic acid, methotrexate and 70H-methotrexate were assayed simultaneously by high performance liquid chromatography. When FA was administered at doses between 50 and 15 mg, maximum concentrations of both the drug and its metabolite were always obtained after 1 to 2 h and remained stable. The same was true for the equilibrium concentration of the two products at doses over 15 mg. These findings suggest saturation of absorption and metabolism of folinic acid at doses over 15 mg.

Combination of reduced folates with methotrexate or 5-fluorouracil. Comparison between 5-formyltetrahydrofolate (folinic acid) and 5-methyltetrahydrofolate in vitro activities

Folinic acid (dlFA) is increasingly used in clinical oncology. The active isomer lFA is intensively metabolized into l5-methyltetrahydrofolate (l5MTHF), the relative proportions of lFA, dFA and l5MTHF in blood varying considerably between oral and i.v. FA administration. The purpose of the study was to compare the in vitro activities of pure lFA and pure l5MTHF at equivalent drug exposure [area under curve (AUC)], taking into account their respective chemical stability in the culture medium. The in vitro growth inhibition [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) test] was evaluated on five human tumor cell lines after methotrexate (MTX)-folate or 5-fluorouracil (5FU)-folate exposures. Not only were the activities of lFA and l5MTHF compared, but also clinically relevant mixtures of lFA + dFA + l5MTHF corresponding to the proportions found at steady state during oral (PO mixture, 4, 39 and 57%, respectively) and i.v. administrations (i.v. mixture, 7, 81 and 12%, respectively). Measurement of folates demonstrated the marked lability of l5MTHF (65.8% loss over 5 days in the culture medium) as compared to lFA (2.6% loss). Whatever the pharmacological model tested (MTX-folate or 5FU-folate), comparison of the folate effects at equivalent drug exposure taking into account their relative stability showed that l5MTHF was never more potent than lFA. Moreover, a higher efficiency of lFA was demonstrated for the cell line most sensitive to 5FU; in this case, as expected, the i.v. mixture was more potent than the PO mixture. This study shows that depending on the tumor, lFA can be more potent than its main circulating metabolite l5MTHF. Along with the limited capacity of oral absorption, the choice between oral and i.v. route for FA administration in patients should take into consideration the different pharmacological activities between lFA and l5MTHF which suggest that the oral route is potentially detrimental to the optimal activity of the 5FU-FA combination as compared to i.v. administration.

A sensitive radioenzymatic assay for (S)-5-formyltetrahydrofolate

A highly sensitive, radioenzymatic method has been developed for the specific and quantitative estimation of (S)-5-formyltetrahydrofolate. This method is based on enzymatic cycling of the 5-formyl derivative to methylenetetrahydrofolate followed by entrapment into a stable ternary complex with thymidylate synthase and tritiated fluorodeoxyuridylate. Determination of bound radiolabeled ligand permits estimation of the original folate. The initial cycling step is catalyzed by the enzyme, methenyltetrahydrofolate synthetase, which is specific for the (S)-diastereomer of 5-formyltetrahydrofolate and generates a product which can be further cycled to tetrahydrofolate using either 10-formyltetrahydrofolate deacylase or glycinamide ribonucleotide transformylase. Tetrahydrofolate is ultimately converted to the entrapable methylene derivative in the presence of excess formaldehyde. Using this assay recovery of reference (S)-5-formyltetrahydrofolate was linear over the range 0.03-1.9 pmol with an average recovery of 83 +/- 2%. The method has been applied to estimation of plasma (S)-5-formyltetrahydrofolate from a volunteer who had been administered (R,S)-5-formyltetrahydrofolate. Where comparison was possible, estimation of plasma (S)-5-formyltetrahydrofolate by this one step ternary complex-based method yielded results that were very similar to those observed by Straw et al. (Cancer Res., 44, 3114, 1984) who used an HPLC-based method for separation of diastereomeric mixtures of reduced folates and microbiological growth dependence to determine (S)-5-formyltetrahydrofolate.

Dose reduction without loss of efficacy for 5-fluorouracil and cisplatin combined with folinic acid. In vitro study on human head and neck carcinoma cell lines

Folinic acid (FA) and cisplatin (CDDP) both potentiate the cytotoxicity of 5-fluorouracil (5-FU). The activity of various drug combinations including 5-FU, CDDP and FA was tested on two human cell lines derived from squamous cell carcinomas of the head and neck. Cytotoxicity was assessed by the semi-automated colorimetric MTT test. The drugs were tested in clinically achievable conditions (concentrations and duration of exposure). The dose response curves for 5-FU (0-100 ng ml-1) associated with FA (10(-7)-10(-5) M) reflected a progressive increase in 5-FU cytotoxicity with increasing FA concentrations. When CDDP (0-5 micrograms ml-1) was associated with 5-FU, CDDP-mediated enhancement of 5-FU cytotoxicity was apparent only when CDDP was given before 5-FU. The triple association CDDP, 5-FU and FA was also tested. In this case, for an identical final cytotoxicity, the presence of FA (10(-6) M) permitted reduction of the 5-FU concentration between 24.2 and 42% and reduction of the CDDP concentration between 13.8 and 72.7%. These observations may be beneficial for the design of more rational therapeutic trials associating CDDP, 5-FU and FA.

Critical factors for the reversal of methotrexate cytotoxicity by folinic acid

The cytotoxicity of methotrexate (MTX) on representative human tumour cell lines (two cell lines from head and neck carcinomas, two from breast carcinomas, two from osteosarcomas and one lymphoblastoid cell line) was evaluated to: (1) examine the optimal time interval between MTX and folinic acid (FA) administration; (2) determine the critical FA/MTX concentration ratios; and (3) compare the relative effects of the equimolar mixture d,I-FA and I-FA. The cytotoxic effects of MTX were assessed by the MTT semi-automated test. For all of the cell lines tested, a significant inverse relationship was noted between the degree of MTX cytotoxicity reversal and the duration of the time interval between MTX and FA administration. Overall an 18-24 h interval between MTX and FA represented a time-threshold after which MTX effects could not efficiently be reversed by FA in most cell lines. With shorter time intervals between MTX and FA, MTX cytotoxicity could be partially on even totally reversed by FA; the intensity of reversal varied among the cell lines tested, and depended on the FA/MTX ratio. Regardless of the interval between MTX and FA, analysis of the various FA/MTX ratios revealed a significant direct relationship between this ratio and the percentage of recovery. Presence of the d-form had no influence on the MTX rescue capacity of the I-form; this suggests that the presence of the d-FA is unlikely to have any significant clinical consequences.

Biochemical pharmacology and analysis of fluoropyrimidines alone and in combination with modulators

After more than three decades since their introduction, fluoropyrimidines, especially FUra, are still a mainstay in the treatment of various solid malignancies. The antitumor effects of fluoropyrimidines are dependent upon metabolic activation. FdUMP, FUTP and FdUTP were identified as the key cytotoxic metabolites that interfere with the proper function of thymidylate synthase and nucleic acids. The relevance of these metabolites is cell-type specific. Recently, fluorouridine diphospho sugars have been detected, but the precise function of this class of metabolites is currently unknown. In mammalian systems fluoropyrimidines and their natural counterparts share the same metabolic pathways since the substrate properties in enzyme-catalyzed reactions are frequently comparable. Ongoing studies indicate that the metabolism and action of fluoropyrimidines exhibit circadian rhythms, which appear to be due to variations in the activity of metabolizing enzymes. Essential for the expanding knowledge of the pathways and effects of fluoropyrimidines has been the constant improvement of analytical methods. These include ligand binding techniques, numerous dedicated HPLC systems and 19F-NMR. Because the overall response rates achieved with fluoropyrimidines are modest, strategies based on biochemical modulation have been devised to enhance their therapeutic index. Biochemical modulators include a wide range of various compounds with different modes of action. In recently completed clinical trials, combinations of FUra with leucovorin, a precursor for 5,10-methylene tetrahydrofolate, or with levamisole, an anthelminthic with immunomodulatory activity, appeared to be superior to FUra alone. At the preclinical level combinations of fluoropyrimidines with, e.g. interferons or L-histidinol were demonstrated to be interesting candidates for further testing. The future therapeutic utility of fluoropyrimidines will depend on both the improvement of combination regimens currently used in the treatment of cancer patients and the judicious clinical implementation of promising experimental modulation strategies. Moreover, novel fluoropyrimidines with superior pharmacological properties may become important as part of or instead of modulation approaches.

Pharmacokinetics of reduced folates after short-term infusion of d, 1-folinic acid

After the use of d,1-folinic acid (d,1-CHO-THF), pharmacokinetic measurements should take into account 1-CHO-THF and its metabolite 1-methyltetrahydrofolic acid (1-CH3-THF) as well as d-CHO-THF. For this purpose, we developed a simple and rapid assay by combining reversed-phase HPLC to determine total levels of d,1-CHO-THF and CH3-THF and chiral HPLC to separate the biologically active 1-CHO-THF from the inactive d-CHO-THF. We investigated the pharmacokinetics after short-term infusion of 300 mg d,1-CHO-THF in ten healthy volunteers. With a mean of 56.5 min, 1-CHO-THF exhibits a rapid body clearance of 222 ml/min, about 60% of which is caused by metabolism to CH3-THF and 40%, by renal excretion. CH3-THF has a terminal half-life of 208 min and a total body clearance of 88.9 ml/min, which is essentially the same as the renal clearance. Due to the lower clearance of CH3-THF, its AUC (2,132 microM x min) exceeds that of 1-CHO-THF (1445 microM x min) by approximately 50%. In contrast to that of the reduced 1-folates, the total body and renal clearance of d-CHO-THF is very low, with values of 13.2 and 12.9 ml/min, respectively. This results in a very high AUC of 24, 269 microM x min, which is higher by factors of 17 and 11 than those of 1-CHO-THF and CH3-THF, respectively. The implications of the distinct kinetics of the reduced 1-folates and d-CHO-THF for the efficacy of folinic acid/5-fluorouracil therapy and adequate protocols for the treatment of advanced colorectal cancer are discussed.