Pharmacokinetics and toxicity of high-dose intravenous methotrexate in the treatment of leptomeningeal carcinomatosis.

PURPOSE: To evaluate the pharmacokinetics and toxicity of high-dose intravenous (i.v.) methotrexate (MTX) with leucovorin in patients with meningeal carcinomatosis. METHODS: Of 16 eligible patients entered on this study, 13 with meningeal carcinomatosis from breast cancer, lung cancer, or osteosarcoma were treated with MTX at loading doses of 200-1500 mg/m2, followed by a 23-h infusion of 800-6000 mg/m2. Three patients without meningeal disease were also treated and the cerebrospinal fluid (CSF) MTX concentrations were compared in patients with and without central nervous system (CNS) disease. RESULTS: Patients without CNS disease had lower CSF MTX concentrations relative to the plasma MTX levels than those with CNS disease, who all had CSF MTX concentrations above the target cytotoxic concentration (1 microM). The CSF MTX concentrations correlated better with the free and the total plasma MTX concentrations than with the doses. The mean half-life of CSF MTX was 8.7 +/- 3.4 h. The mean plasma clearance of MTX was not significantly different in patients with CNS disease (84 +/- 41 ml/min per m2) versus without CNS disease (59 +/- 38 ml/min per m2). All toxicities were grade 2 or less except grade 3 hematologic toxicity. No patient had an objective response in the CSF. CONCLUSION: This trial demonstrates that potentially cytotoxic CSF MTX concentrations (> 1 microM) are delivered safely by i.v. infusion, a less invasive and better distributed CSF therapy compared with intrathecal MTX. Because of the excellent pharmacokinetics and toxicity, high-dose i.v. MTX should be evaluated at a loading dose of 700 mg/m2 and a 23-h infusion of 2800 mg/m2 with leucovorin in less heavily pretreated patients with carcinomatous meningitis.

Phase I trial of intraperitoneal iododeoxyuridine with and without intravenous high-dose folinic acid in the treatment of advanced malignancies primarily confined to the peritoneal cavity: flow cytometric and pharmacokinetic analysis.

In this Phase I study, the maximally tolerated doses (MTDs) of i.p. iododeoxyuridine (IdUrd) alone and in combination with i.v. calcium leucovorin (LV) were determined. The pharmacokinetics and pharmacological advantage of IdUrd were evaluated, and flow cytometric analysis allowed examination of the extent of incorporation of IdUrd into tumor cells with and without the addition of i.v. LV. Thirty-nine patients with advanced neoplasms primarily confined to the peritoneal space were enrolled in a dose-escalation trial using 4-h dwells of IdUrd administered i.p. daily for 4 days with and without an i.v. infusion of LV 500 mg/m2/day for 4.5 days. Twenty-three patients received single-agent therapy, and 13 patients received i.p. IdUrd in combination with i.v. LV. The MTD of single-agent IdUrd administered on this schedule was 4125 mg/m2/day for 4 days; and that of the IdUrd in combination was 3438 mg/m2/day. Dose-limiting toxicities were myelosuppression and stomatitis. During the period of the dwell, the peritoneal AUC (area under the curve) of IdUrd exceeded the plasma AUC of IdUrd by one or two orders of magnitude in all patients at all doses tested; there was a possible effect of LV on peritoneal AUC. The geometric mean pharmacological advantage (AUCperitoneal/ AUCplasma) was 181 at 625 mg/m2/day and 90 at 4538 mg/m2/day. Flow cytometric analysis suggests saturation of IdUrd measured in DNA at the 2500-3125 mg/m2 dose level, without an increase after the addition of LV. Twelve patients received 4-12 courses of therapy. One patient with recurrent ovarian cancer who received 16 courses of therapy experienced complete resolution of her ascites, near normalization of CA-125 levels, and improved quality of life; two patients with high-risk tumors receiving "adjuvant" therapy are disease-free at 3 and 6 years after treatment; other patients experienced transient clearing of ascites. The recommended Phase II dose of i.p. IdUrd using a 4-h dwell daily for 4 days is 3750 mg/m2/day alone or 3125 mg/m2/day in combination with continuous i.v. LV at 500 mg/m2/day for 4.5 days. Although flow cytometric data suggest that DNA incorporation of IdUrd is not affected by the addition of LV, the cytotoxicity of the combination regimen may be increased due to LV-enhanced, IdUrd-related inhibition of thymidylate synthase. For this reason, we recommend that efficacy studies of the combination continue in parallel with studies of IdUrd alone.

Phase I study of phosphonacetyl-L-aspartate, 5-fluorouracil, and leucovorin in patients with advanced cancer.

Low-dose phosphonacetyl-L-aspartate (PALA) may potentiate both 5-fluorouracil (5-FU) incorporation into RNA and thymidylate synthase inhibition by 5-fluorodeoxyuridylate (5-FdUMP). The gastrointestinal toxicity of 5-FU is not increased by PALA administration. Exogenous leucovorin, on the other hand, which enhances thymidylate synthase inhibition, appears to increase the clinical toxicity of 5-FU in a dose-dependent manner. As a result, the clinical use of high-dose leucovorin requires a marked dose reduction of 5-FU. Extracellular leucovorin levels of 1 microM suffice to maximize the enhancement of thymidylate synthase inhibition in several models. We conducted a trial to add leucovorin to the PALA/5-FU regimen. We chose a leucovorin dose that was predicted to yield end-infusion total reduced folate concentrations of 1 microM. The major endpoint was to determine the maximum tolerated dose of 5-FU in this combination. The regimen consisted of 250 mg/m2 PALA given on day 1 and, 24 h later, escalating 5-FU doses ranging from 1,850 to 2,600 mg/m2 admixed with 50 mg/m2 leucovorin and given by 24-h infusion. Courses were repeated weekly. A total of 24 patients with a median performance status of 1 were entered at three dose levels. Diarrhea was dose-limiting; 6/13 patients had grade II or worse diarrhea at 2,600 mg/m2. Dose modification resulted in a mean dose intensity of 2,300 mg/m2 at both the 2,600- and 2,300-mg/m2 dose levels. The 2,300-mg/m2 dose is suitable for phase II testing of this regimen. Three patients (two with breast cancer and 1 with sarcoma) had a partial remission. We measured steady-state concentrations (Css) of 5-FU in 23 patients. The mean Css increased with dose from 0.738 to 1.03 micrograms/ml. Total body clearance did not vary with dose in this range. Patients with grade II or worse diarrhea had a higher mean Css (1.10 +/- 0.19) than those with grade O or I toxicity (0.835 +/- 0.25, P < 0.02). Total bioactive folates (bound and free) were measured using a biological assay. Pretreatment values ranged from 2 to 52 nM and were not predictive of toxicity. End-infusion (23-h) values were somewhat lower than predicted and ranged from 400 to 950 nM. The risk of diarrhea was positively correlated with end-infusion total folate values. In a logistic regression analysis, total folate values obtained at 23 h were a more powerful predictor of diarrhea than were 5-FU Css values.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacology and phase I trial of high-dose oral leucovorin plus 5-fluorouracil in children with refractory cancer: a report from the Children's Cancer Study Group.

Because of the synergy seen in adult trials when 5-fluorouracil is combined with leucovorin, we initiated a Phase I trial of this combination in children's refractory cancer. Leucovorin, an equal mixture of the (6R,S)-diastereoisomers, was administered p.o. for 6 consecutive days as 4 equal doses at 0, 1, 2, and 3 h totaling 500 mg/m2/day. 5-Fluorouracil was given daily on days 2 to 6 as an i.v. bolus immediately following the last dose of leucovorin. The leucovorin dose was held constant while the 5-fluorouracil dose was escalated in cohorts of patients from 300 mg/m2/day to its maximally tolerated dose. Thirty-five patients (19 with acute leukemia and 16 with solid tumors) were evaluable for toxicity. The maximally tolerated dose of FUra was 450 mg/m2/day for 5 treatments for patients with solid tumors and 650 mg/m2/day for 5 treatments for the children with leukemia. The dose-limiting toxicities were myelosuppression and stomatitis. Other side effects included transient, mild elevations of serum transaminases, mild nausea, vomiting, and diarrhea. The pharmacokinetics of high-dose p.o. leucovorin was studied in 23 children. There was considerable interpatient variability in the plasma concentrations of total bioactive folates (TBAF), (6S)-leucovorin, and (6S)-5-methyltetrahydrofolic acid. The maximum plasma concentration (Cmax) of TBAF was 821 +/- 97 (SE) nM, occurring at a median of 8 h; the Cmax of (6S)-leucovorin was 77 +/- 11 nM, occurring at 4 h. The TBAF concentration fell to 146 +/- 42 nM by 24 h. (6S)-5-Methyltetrahydrofolic acid accounted for 90 +/- 7% of the TBAF at the Cmax. The plasma concentration of (6R)-leucovorin, the unnatural isomer, was equal to that of TBAF. Thus, p.o. leucovorin reduced the 5-fold excess of (6R)-leucovorin over TBAF seen after i.v. doses. The relative amounts of the three major plasma species were approximately the same as in adults, even though the Cmax of each compound was lower.

Pharmacokinetics of diastereoisomers of (6R,S)-folinic acid (leucovorin) in humans during constant high-dose intravenous infusion.

Eleven patients treated with a 5.5-day continuous i.v. infusion of 500 mg/m2/day of (6R,S)-folinic acid in combination with daily bolus 5-fluorouracil had a median steady-state plasma concentration of 3.25 microM (6S)-folinic acid (the bioactive diastereoisomer). The bioactive metabolite (6S)-5-methyltetrahydrofolic acid, analyzed in six patients, reached a median steady-state plasma concentration of 5.7 microM. The lowest plasma concentrations at steady-state were 1.86 microM (6S)-folinic acid and 3.12 microM (6S)-5-methyltetrahydrofolic acid. These concentrations are above the minimum concentrations shown by other investigators to produce synergism between (6R,S)-folinic acid and 5-fluorouracil in vitro. The median steady-state plasma concentration of (6R)-folinic acid was 38.2 microM, more than 10 times the concentration of (6S)-folinic acid. Along with other plasma pharmacokinetic parameters, terminal half-lives were estimated for (6S)-folinic acid (median, 45.4 min), (6R)-folinic acid (median, 388 min), and (6S)-5-methyltetrahydrofolic acid (median, 446 min). Investigation of the renal pharmacokinetics confirmed the marked difference in the renal clearance of the two diastereoisomers of folinic acid which had been observed after low doses of (6R,S)-folinic acid (J. A. Straw, D. Szapary, and W. T. Wynn, Cancer Res., 44: 3114-3119, 1984). However, the low renal clearance of (6R)-folinic acid (median, 8.2 ml/min/m2) was attributable to the extensive binding of (6R)-folinic acid to plasma proteins (median, 8.7% free), not to reabsorption in the kidney.

Pharmacokinetics of leucovorin (D,L-5-formyltetrahydrofolate) after intravenous injection and constant intravenous infusion.

The pharmacokinetics of the active and inactive diastereoisomers of leucovorin and its active metabolite, 5-methyltetrahydrofolate (5-CH3-THF) were studied after iv injection of leucovorin in normal human subjects at a dose of 28 mg/m2, and in patients given 500 mg/m2 daily by constant iv infusion for a 5.5 day period. In both studies the plasma half-life (t1/2) of the active isomer, L-formyltetrahydrofolate (CHO-THF), was only 32 to 35 minutes, whereas the inactive isomer, D-CHO-THF had a plasma t 1/2 of 352 to 485 minutes. During constant infusion, the plasma levels reached plateaus of 2.33 and 37.5 microM for L-CHO-THF and D-CHO-THF, respectively. The inactive isomer was cleared from plasma only by urinary excretion of the unchanged drug. The active isomer was also excreted unchanged in the urine but in addition was extensively metabolized to the active metabolite L-5-CH3-THF. The active metabolite achieved a plasma level of 4.85 microM during constant infusion and appeared to have a longer t 1/2 after constant infusion than was observed after iv injection. Furthermore a larger apparent volume of distribution (Vd) of 5-CH3-THF was obtained in the constant infusion study. These findings suggest that constant iv infusion of large doses of leucovorin can considerably expand the intracellular pools of active folate. The consequence of the extensive accumulation of the inactive isomer, D-CHO-THF, is not known. However, the small Vd of D-CHO-THF suggests that it does not extensively accumulate in tissues.

Selective killing of transformed cells by methotrexate with histidine deprivation or with alpha-amino alcohols.

The effects of amino acid deprivation and treatment with amino alcohols upon the growth, viability, and susceptibility to methotrexate (MTX) cytotoxicity were examined in BALB/3T3 cells and their virally transformed counterparts, SV-T2 cells. Cells were deprived of either histidine or tyrosine plus phenylalanine, or they were treated with amino alcohol analogues of histidine and tyrosine (histidinol and tyrosinol). When incubated in medium lacking histidine and supplemented with dialyzed serum (histidine-deficient medium), the BALB/3T3 cells remained viable for at least 3 days, but they ceased logarithmic growth, and the cell number reached an early plateau. In contrast, the SV-T2 cells continued to divide in histidine-deficient medium. Neither cell line ceased division in medium deficient in both phenylalanine and tyrosine. Incubation of the BALB/3T3 cells with 1.5 mM histidinol or 1.0 mM tyrosinol caused an early plateau similar to the effect of histidine deprivation. SV-T2 cells were not affected by these concentrations of histidinol or tyrosinol, but growth was arrested at higher concentrations. Any of the conditions used which caused a plateau in the number of BALB/3T3 cells substantially protected the treated cells from cell death caused by MTX. Therefore, pretreatment of BALB/3T3 cells with histidine deprivation, 1.5 mM histidinol, or 1.0 mM tyrosinol protected this cell line against MTX-induced cell death, while the same pretreatment conditions failed to protect SV-T2 cells. (SV-T2 cells were protected by 4.0 mM histidinol.) Thus, the ability of MTX to kill cells in vitro can be selectively modified by conditions which protect cells which retain normal growth control characteristics, but which do not protect virally transformed cells.