Toxicity of levamisole and 5-fluorouracil in human colon carcinoma cells.

The combination of 5-fluorouracil (5-FU) with the immunomodulator levamisole (Lev) has been clinically tested in patients with metastatic colorectal carcinoma and as adjuvant therapy following primary tumor surgery. In some studies in advanced disease, the addition of Lev to 5-FU improved the median duration of response; in the adjuvant setting, the combination was associated with improvement in the disease-free survival. We studied whether Lev was directly toxic to three human colorectal carcinoma cell lines (HCT 116, SNU-C4, and NCI-H630). We also evaluated the toxicity of Lev in combination with 5-FU in these three cell lines. Lev inhibited the growth of all three colorectal cell lines, but only at concentrations two logs above that achieved with a standard 150-mg oral dose of Lev. In cell growth studies, 500 and 1,000 microM Lev increased the toxicity of 5-FU in HCT 116 cells in an additive fashion. In clonogenic assays, continuous exposure to 10 or 100 microM Lev was minimally toxic and did not enhance the lethality associated with a 24-hour exposure to 5-FU in any of the cell lines. Lev alone at 1,000 microM decreased colony formation by 45% in HCT 116 cells. A combination of 1,000 microM Lev with 10 microM 5-FU resulted in a decrease in HCT 116 colony formation from 54% to 6% of control levels. Continuous exposure of NCI-H630 cells to 500 microM Lev decreased colony formation to 76.5% of control levels; when Lev was combined with 50 microM 5-FU, colony formation was decreased from 59.5% to 27.5% of control levels. We conclude that at concentrations achievable with conventional doses of Lev, there was no evidence of direct toxicity in these colorectal cell lines. Furthermore, an additive interaction with 5-FU was evident only at suprapharmacologic doses of Lev.

The role of methotrexate in osteosarcoma.

High-dose methotrexate (MTX) is one of the agents currently used in intensive adjuvant chemotherapy regimens for nonmetastatic osteosarcoma. To elucidate the role of high-dose MTX in this disease, we present the history of trials conducted with MTX from the first single-agent studies through progressively complex combination regimens. With this background, some of the basic issues concerning MTX therapy in osteosarcoma are discussed.

Decreased catabolism of fluorouracil in peripheral blood mononuclear cells during combination therapy with fluorouracil, leucovorin, and interferon alpha-2a.

BACKGROUND: We previously reported that recombinant interferon alpha-2a (IFN alpha-2a) therapy was associated with a dose-dependent decrease in fluorouracil (5-FU) clearance. PURPOSE: In this study, we used peripheral blood mononuclear cells (PBMCs), which are responsive to IFNs, as surrogate tissue to determine whether the change in clearance might be explained by decrease in 5-FU catabolism during IFN alpha-2a therapy. METHODS: The study population consisted of 45 patients with adenocarcinoma arising in the gastrointestinal tract. Thirty-seven patients received therapy containing IFN alpha-2a at a median dose of 5 million U/m2 per day (range, 1.7-7.5 million U/m2 per day) starting on day 1 and continuing through either day 7 or day 14 in conjunction with intravenous high-dose leucovorin (LV) followed by bolus 5-FU on days 2-6. Eight patients received the same schedule of 5-FU and LV daily for 5 days without IFN alpha-2a but with granulocyte-macrophage colony-stimulating factor starting on day 6 and ending at least 3 days prior to the start of the next cycle. Peripheral blood was collected during 70 cycles on days 1, 2, and 4 prior to the daily treatment with IFN alpha-2a + 5-FU+LV and during 19 cycles on days 1 and 4 prior to the daily treatment with 5-FU+LV without IFN alpha-2a. In a given patient cycle, matched samples were drawn at approximately the same time of day. PBMCs were isolated, and the intact cells were exposed to 4 microM [3H]5-FU, and the formation of [3H]dihydrofluorouracil was determined by reverse-phase high-performance liquid chromatography. RESULTS: In 47 matched patient cycles from IFN alpha-2a + 5-FU+LV-treated patients in which samples were available on days 1, 2, and 4, 5-FU catabolism decreased by 20% (P2 = .03) and 41% (P2 = .0001) from the baseline catabolic rate (2.5 +/- 0.2 pmol/min per 10(6) cells [mean +/- SE]) on days 2 and 4, respectively. Using information from all paired samples, the mean change from baseline on day 2 was -0.4 +/- 0.2 pmol/min per 10(6) cells (n = 54; P2 = .05), and the change from baseline on day 4 was -1.3 +/- 0.3 pmol/min per 10(6) cells (n = 63; P2 = .0001). In contrast, changes in 5-FU catabolism were not evident in the PBMCs of the reference population receiving 5-FU+LV without IFN alpha-2a. CONCLUSIONS: The magnitude of the change in 5-FU catabolism is similar to the magnitude of the decrease in 5-FU clearance in our previous study. These observations suggest that changes in 5-FU catabolism during therapy with IFN alpha-2a, 5-FU, and LV may account for the decreased 5-FU clearance.

Correlates of severe or life-threatening toxic effects from trimetrexate.

Trimetrexate, an investigational antifol, has been associated with marked variability in drug tolerance among patients. The agent is extensively protein bound, and hepatic biotransformation plays a major role in its elimination. In early phase II testing, nine of 15 patients who experienced life-threatening or fatal toxic effects from trimetrexate had albumin levels less than or equal to 3.5 g/dL prior to treatment. This prompted a review of the data base on 272 patients entered in phase I clinical trails. The incidence of severe or life-threatening anemia, leukopenia, neutropenia, thrombocytopenia, mucositis, and hepatic toxic effects during the first course of trimetrexate was analyzed according to dose, schedule, prior treatment, and baseline protein and albumin levels. The schedules using doses given by short infusions of 30-60 minutes daily for 5 days or weekly for 3 weeks were generally associated with higher incidence of toxic effects than the schedules using doses given every other week by short infusions or those using continuous infusion. The occurrence of leukopenia and mucositis was dose related. Patients with baseline albumin levels less than or equal to 3.5 g/dL had higher incidence of all types of severe or life-threatening toxic effects than those with albumin levels greater than or equal to 3.6 g/dL, and the differences were significant for the development of anemia, thrombocytopenia, and mucositis. Similar correlations were noted for pretreatment protein levels less than or equal to 6.0 g/dL. The small cohort of patients with leukemia experienced substantial toxic effects and tended to have low protein and albumin levels. Performance status and prior therapy did not emerge as strong predictors of severe toxic effects in the univariate analysis. Multivariate analysis confirmed that the type of cancer (leukemia vs. solid tumor), dose, schedule, and baseline albumin level were significant and independent predictors of severe and life-threatening toxic effects in the phase I patient population. Multivariate analysis including only patients with solid tumors indicated that albumin level, dose, and schedule remained significant predictors of toxic effects. Since normal liver function as reflected by bilirubin and transaminase values were a requirement for eligibility, the results suggest that albumin and protein levels may provide a more sensitive index of hepatic function. Patients with hypoalbuminemia and hypoproteinemia are at increased risk of experiencing severe or life-threatening toxic effects from trimetrexate and should be treated cautiously.

Cephalotaxine esters: antileukemic advance or therapeutic failure?

Clinical trials conducted in the People's Republic of China and the United States of the antileukemic efficacy of the cephalotaxine esters are reviewed. Harrington has been incorporated into combination regimens for the treatment of newly diagnosed acute nonlymphocytic leukemia (ANLL) in China, and activity with cephalotaxine esters has also been noted in chronic myelogenous leukemia. While the investigational agent homoharringtonine has shown some activity in the United States in ANLL, investigator interest in the United States has waned because of toxicity and inconvenient schedules. The Chinese trials have used different schedules than have U.S. studies and have been associated with less toxicity. These trials provide new information that may lead to further investigations of the cephalotaxine esters in the United States.

Pentostatin in hairy cell leukemia: treatment by the special exception mechanism.

An analysis of the clinical outcomes in 66 patients with hairy cell leukemia treated with pentostatin under the Special Exception mechanism of the Division of Cancer Treatment, National Cancer Institute, between 1983 and 1987 has revealed a favorable balance of risk and benefit. Hematologic parameters and performance status were improved in most patients treated outside the clinical trials mechanism. The treating physicians considered 37 patients (56%) to be complete responders and 15 patients (23%) to be partial responders. Four patients (6%) died while receiving pentostatin. Life-threatening leukopenia (wbc count, less than 1,000/mm3) was reported in 24% of patients, and severe or life-threatening infection occurred in 11%. The experience gained with these patients supplements the information presently being collected from the controlled clinical trials and supports the development of a group C treatment protocol.

Alteration of fluorouracil metabolism in human colon cancer cells by dipyridamole with a selective increase in fluorodeoxyuridine monophosphate levels.

The nucleoside transport inhibitor dipyridamole can increase the cytotoxicity of 5-fluorouracil in a human colon cancer cell line (HCT 116) without affecting the total amount of fluorouracil incorporated into the acid soluble and insoluble fractions (J. L. Grem and P. H. Fischer, Cancer Res., 45: 2967-2972, 1985). We now report that dipyridamole altered the pattern of fluorouracil metabolism and provided a selective increase in intracellular fluorodeoxyuridine monophosphate (FdUMP) levels. At 2 and 4 h after exposure to fluorouracil and dipyridamole, FdUMP levels were approximately 5-fold higher in the presence of dipyridamole. The ratio of FdUMP to fluorouridine triphosphate at 4 h was substantially increased in the presence of dipyridamole (0.4 +/- 0.05) compared to fluorouracil alone (0.08 +/- 0.03). In cells preloaded with fluorodeoxyuridine (FdUrd), dipyridamole potently inhibited the efflux of FdUrd, leading to an increased retention of intracellular FdUMP. One h following removal of [6-3H]FdUrd, the FdUMP levels were increased 8-fold in the presence of dipyridamole, and the half-life of intracellular FdUMP was increased from 24 to 78 min. We have previously shown that the addition of sufficient thymidine (25 microM) can prevent the augmentation of fluorouracil toxicity produced by dipyridamole. In these studies, the addition of 25 microM thymidine reduced the FdUMP levels to less than half of those measured in the presence of fluorouracil plus dipyridamole for the first 8 h of exposure, and reduced the FdUMP levels to 6% of the FdUMP levels seen with fluorouracil and dipyridamole after 24 h of exposure. Thymidine prevented the enhanced intracellular retention of FdUMP produced by dipyridamole in cells preloaded with FdUrd. In addition, thymidine inhibited the accumulation of FdUMP in cells exposed to FdUrd. In cancer cells which significantly catabolize FdUMP, the ability of dipyridamole to block the efflux of FdUrd may provide an effective means of selectively increasing FdUMP levels and enhancing the toxicity of fluorouracil. Furthermore, dipyridamole blocked the efflux of deoxyuridine and prolonged the intracellular half-life of deoxyuridine monophosphate. In cells prelabeled with [2'-3H]dUrd, transfer of tritium to FdUrd and FdUMP occurred in cells exposed to fluorouracil and dipyridamole. These data suggest that blockade of nucleoside efflux can enhance the availability of deoxyribose-1-phosphate donors for the synthesis of FdUrd. Thus, dipyridamole's ability to inhibit nucleoside transport can perturb the metabolism of a nucleobase, fluorouracil.

Enhancement of the toxicity and DNA incorporation of arabinosyl-5-azacytosine and 1-beta-D-arabinofuranosylcytosine by cyclopentenyl cytosine.

We evaluated the interaction of a biochemically active concentration of cyclopentenyl cytosine (CPE-C), an investigational antimetabolite which inhibits CTP synthetase, on the cytotoxicity of arabinosyl-5-azacytosine (Ara-AC) and 1-beta-D-arabinofuranosylcytosine (Ara-C) in HCT 116 colon carcinoma cells. A 3-h exposure to 0.5 microM CPE-C depleted CTP pools by over 90% and decreased dCTP pools by 57%; the effect on CTP pools persisted for up to 24 h following washout of CPE-C. A 3-h pre-exposure to 0.5 microM CPE-C augmented the growth inhibition resulting from a 24-h exposure to Ara-AC. The combination of 1 microM cytidine and deoxycytidine fully reversed the enhancement associated with CPE-C pretreatment, to a level of growth inhibition expected from either CPE-C or Ara-AC alone. A striking enhancement of toxicity was observed in clonogenic studies with pre-exposure to CPE-C at a nonlethal dose followed by either Ara-AC or Ara-C. CPE-C increased the formation of Ara-AC and Ara-C nucleotides by as much as 3-fold, and this was accompanied by increased incorporation of the arabinosyl nucleotides into methanol-precipitable material. Analysis of purified RNase-treated nucleic acids by cesium sulfate density centrifugation confirmed that a 3-h pre-exposure to CPE-C increased [3H]-Ara-C incorporation into DNA at 4 and 24 h by 2.4- and 2.7-fold, respectively. Thus, these studies indicate that CPE-C can function as a biochemical modulator. Following a brief exposure to a nonlethal concentration, CPE-C is capable of augmenting the cytotoxicity and intracellular metabolism of Ara-AC and Ara-C.

Augmentation of 5-fluorouracil cytotoxicity in human colon cancer cells by dipyridamole.

The effect of dipyridamole (DP), an inhibitor of nucleoside transport, on the uptake and toxicity of 5-fluorouracil (FUra) was examined in a human colon cancer cell line (HCT 116). DP substantially increased the cytotoxicity of FUra in cell growth experiments and in viability assays measuring colony formation. The augmentation by DP was dose and time dependent. Several possible mechanisms by which DP enhanced FUra toxicity were investigated. DP did not alter the uptake of FUra into the acid-soluble and -insoluble fractions of HCT 116 cells. While DP did not affect the uptake of FUra, it did inhibit the transport of the nucleoside analogues, fluorouridine and fluorodeoxyuridine, of FUra. Although DP effectively inhibited the uptake of thymidine and uridine in a dose-dependent manner, several lines of evidence suggested that inhibition of nucleoside salvage was not the critical effect. (a) The toxicity of FUra was not prevented by thymidine, uridine, or the combination of thymidine and uridine. Thymidine triphosphate pools, decreased by 50% during the initial 8 h of exposure to FUra, were not further depleted by the addition of DP. The shrinkage in deoxythymidine triphosphate pools produced by FUra was prevented by concomitant exposure to thymidine; however, this did not translate into protection from FUra lethality. The use of dialyzed serum, which greatly diminished the availability of nucleic acid precursors, did not increase the toxicity of FUra. DP increased the cytotoxicity of FUra as effectively in experiments utilizing dialyzed serum as when nondialyzed serum was used. Surprisingly, however, the addition of sufficient thymidine to overcome the DP block did prevent the augmentation of FUra toxicity produced by DP. DP may provide a novel means of enhancing the cytotoxicity of FUra.

A phase I study of continuous infusion 5-fluorouracil plus calcium leucovorin in combination with N-(phosphonacetyl)-L-aspartate in metastatic gastrointestinal adenocarcinoma.

Preclinical studies suggest that the biochemical effects of N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartate carbamoyltransferase (ACTase), may increase the metabolic activation of 5-fluorouracil (5-FU) and enhance its cytotoxicity through both RNA- and DNA-directed mechanisms. In this Phase I trial, 22 evaluable patients with adenocarcinoma of the gastrointestinal tract were entered at escalating doses of 5-FU starting at 1150 mg/m2/day given as a concurrent 72-h i.v. infusion with a fixed dose of leucovorin (LCV), 500 mg/m2/day. The dose of 5-FU was escalated within patients according to individual tolerance, and then PALA at 250 mg/m2 was added 24 h prior to the initiation of the 5-FU/LCV infusion of the subsequent cycle. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 3 of 5 patients treated with 2300 mg/m2/day 5-FU; therefore, the recommended dose of 5-FU with concurrent LCV is 2000 mg/m2/day. Twenty-seven additional patients were then treated with escalating doses of PALA ranging from 375 to 2848 mg/m2, i.v., followed 24 h later by 2000 mg/m2/day 5-FU with high-dose LCV. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 2 of 3 patients entered at 2848 mg/m2 PALA. Dose-limiting mucositis and skin rash ultimately required both PALA and 5-FU dose reductions in 4 of 6 patients treated with 1899 mg/m2 PALA. Toxicity was similar, however, in patients receiving PALA at doses ranging from 375 to 1266 mg/m2. The mean steady-state plasma concentration of 5-FU at 2000 mg/m2/day was 6.5 +/- 0.9 microM; patients with 5-FU levels > 9 microM had a significantly higher incidence of serious gastrointestinal and hematological toxicity. Compared to each patient's own baseline, a significant trend for decreasing ACTase activity with increasing PALA dose was evident using cytosol isolated from peripheral blood mononuclear cells 24 h after PALA treatment (P2 = 0.01). PALA < or = 844 mg/m2 failed to appreciably inhibit ACTase activity at 24 h in most patients; furthermore, a decrease in ACTase activity by > 50% from baseline was seen in only 29% of cycles. More consistent inhibition of ACTase activity was seen with PALA > or = 1266 mg/m2. Even with the highest PALA doses, however, ACTase activity returned to baseline by 96 h in most patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Methotrexate and dipyridamole combination chemotherapy based upon inhibition of nucleoside salvage in humans.

We have carried out a clinical trial in 23 patients to determine whether dipyridamole modulates the clinical effect of methotrexate. This trial was based upon in vitro studies which indicate that dipyridamole potentiates the cytotoxic action of methotrexate through inhibition of thymidine salvage. Methotrexate was given as a bolus injection 24 h after initiation of a high dose dipyridamole infusion. The trial was designed so that methotrexate was escalated in individuals until toxicity occurred and then the methotrexate dose resulting in toxicity was repeated without dipyridamole. During the course of this study the methotrexate dose was escalated from 10 to 130 mg/m2. While individual patient tolerance varied, moderate to severe myelosuppression and/or mucositis occurred frequently in patients receiving the combination with methotrexate doses greater than or equal to 60 mg/m2. Ten of 10 patients who experienced moderate or severe toxicity with the combination had significantly less toxicity when treated with methotrexate alone. Dipyridamole did not increase toxicity by an alteration in methotrexate elimination. The potentiation of methotrexate by dipyridamole in these patients suggests that physiological thymidine levels are sufficient to perturb the clinical effects of methotrexate and that thymidine salvage may represent a mechanism for clinical resistance to methotrexate. These results also suggest that a high dose dipyridamole regimen can be used as a pharmacological approach to test the role of nucleoside membrane flux on the clinical action of other standard chemotherapeutic drugs. Phase II studies testing the clinical efficacy of this combination should use a methotrexate dose of 60 mg/m2 with a provision for methotrexate dose escalation based upon individual patient tolerance.

Phase I trial of 5-fluorouracil and dipyridamole administered by seventy-two-hour concurrent continuous infusion.

Forty-seven patients with advanced malignancies were treated with a concurrent 72-h continuous infusion of 5-fluorouracil (FUra) and dipyridamole. The FUra dose was escalated over the dose range of 185 to 3600 mg/m2/day for 3 days. Dipyridamole was administered in a fixed dose of 7.7 mg/kg/day for 3 days. A total of 155 courses of therapy were completed of which there were 31 paired courses of the combination and FUra alone, at the same dose of FUra and in the same patient. This was for purposes of analysis of pharmacokinetics and modulation of FUra toxicity by dipyridamole. Stomatitis was the dose-limiting toxicity experienced by patients entered into this trial. Myelosuppression was not a serious problem. Increasing FUra plasma concentration was associated with greater leukopenia and stomatitis. Dipyridamole did not appear to modulate the systemic toxicity of FUra. The pharmacokinetics of FUra were altered by the concurrent administration of dipyridamole. Dipyridamole promoted the total body clearance of FUra which resulted in lower mean steady-state FUra plasma concentrations when compared with courses of FUra alone administered at the same dose level. These differences were statistically significant over the course of the trial. For courses of the combination, FUra exhibited linear pharmacokinetics over the dose range studied. Total body clearance of FUra declined slightly at the higher dose levels, but the differences were not significant. For courses of FUra alone, total body clearance was significantly decreased above the dose level of 2300 mg/m2/day. At the maximal tolerated dose of FUra, 2300 mg/m2/day x3, mean steady-state FUra plasma concentration and total body clearance were 6.6 microM and 122 liters/h/m2, respectively, for courses of the combination. The corresponding pharmacokinetic parameters were 7.4 microM and 103 liters/h/m2 for courses when FUra was given alone. Further evaluation of the utility of this regimen and basis of these pharmacokinetic observations appear warranted.

Reversible increase in serum alpha-fetoprotein content associated with hepatic dysfunction during chemotherapy for seminoma.

Serial monitoring of the serum content of the beta subunit of human chorionic gonadotropin (beta hCG) and alpha-fetoprotein (alpha FP) is useful in the initial staging of germ cell tumors and assessing the response to treatment. An increase in either marker during or following treatment almost always heralds disease progression and indicates the need for additional therapy. We report two patients in whom substantial increases in the serum content of AFP occurred during chemotherapy for advanced seminoma. Hepatic dysfunction was present in both patients; in one patient, a chronic carrier of hepatitis B virus, the liver dysfunction was associated with reactivation of hepatitis B manifested by anicteric hepatitis and hepatitis B e antigen positivity. Marked tumor regression had occurred in both patients, and chemotherapy was discontinued in spite of the elevated alpha FP level. The alpha FP content in the serum gradually returned to normal, and hepatic dysfunction resolved. Both patients remain free of disease 15 and 17 months following the last chemotherapy treatment. These cases illustrate that hepatic dysfunction and alpha FP production may occur during chemotherapy and that increases in serum alpha FP content must be interpreted with caution since the elevated alpha FP level does not always indicate progression of germ cell tumors.

Phase I and pharmacokinetic study of recombinant human granulocyte-macrophage colony-stimulating factor given in combination with fluorouracil plus calcium leucovorin in metastatic gastrointestinal adenocarcinoma.

PURPOSE: To determine the toxicities and potential for dose escalation of intravenous (IV) bolus fluorouracil (5-FU) given with 500 mg/m2/d leucovorin (LCV) and granulocyte-macrophage colony-stimulating factor (GM-CSF). PATIENTS AND METHODS: Thirty-seven patients received escalating doses of 5-FU/LCV on days 1 to 5 with subcutaneous GM-CSF either 5 or 10 micrograms/kg/d starting on day 6 or 3 micrograms/kg/d starting on day 1. 5-FU was escalated from 370 mg/m2/d by 15% increments between patient cohorts and within patients according to tolerance. RESULTS: With GM-CSF starting on day 6, dose-limiting toxicity occurred during cycle no. 1 in all three patients entered at 5-FU 490 mg/m2/d. However, individual patients tolerated 5-FU doses up to 644 mg/m2/d. When all cycles were analyzed, grade 3 to 4 mucositis and grade 4 granulocytopenia complicated < or = 15% and < or = 6% of cycles with 5-FU doses < or = 560 mg/m2/d (115 cycles). With GM-CSF starting on day 1, dose-limiting granulocytopenia occurred during cycle no. 1 in five of 10 patients entered at 5-FU 490 mg/m2/d. Although the granulocyte nadirs were significantly lower at each 5-FU dose level with the concurrent GM-CSF schedule (eg, 490 mg/m2/d: median, 879/microL v3,286/microL; two-tailed P [P2] < .001), dose-limiting granulocytopenia complicated < or = 16% of cycles with 5-FU < or = 560 mg/m2/d (99 cycles); > or = grade 3 mucositis occurred in < or = 20% of cycles. Grade 3 to 4 diarrhea was unusual with either GM-CSF schedule. Most patients treated with GM-CSF > or = 5 micrograms/kg/d required dose reductions for constitutional toxicity; 3.0 to 3.8 micrograms/kg/d was better tolerated. Venous thrombosis occurred in 17% of patients (concurrent v sequential GM-CSF, 29% v 5%; P2 = .08). The median delivered 5-FU dose-intensity for GM-CSF starting either on day 6 or on day 1 was 615 and 647 mg/m2/wk (P2 = .41), respectively. Pharmacologic exposure to 5-FU increased with higher doses of 5-FU, and concurrent GM-CSF administration did not affect 5-FU clearance. CONCLUSION: A starting dose of 425 mg/m2/d of 5-FU with LCV on days 1 to 5 could be safely combined with GM-CSF starting either on day 1 or day 6, with further 5-FU dose escalation according to individual tolerance.

Teniposide in the treatment of leukemia: a case study of conflicting priorities in the development of drugs for fatal diseases.

Teniposide, a semisynthetic epipodophyllotoxin, was found to be highly active against murine leukemias, and the combination of teniposide with cytosine arabinoside (ara-C) was curative in murine leukemia models. The antitumor activity in preclinical models prompted introduction of teniposide into the clinic in 1971. Although teniposide as a single agent rarely produced a complete remission in heavily pretreated leukemia patients, teniposide plus ara-C produced complete remissions in some patients with refractory and relapsed acute lymphoblastic leukemia (ALL). Innovative front-line and salvage regimens using teniposide have been developed that incorporate a multi-drug strategy with early intensification, rotation of drug combinations in maintenance, and regional therapy in an effort to improve the cure rate in leukemia. However, as the complexity of these regimens increases, the contribution of an individual component such as teniposide becomes less clear. Although some of these regimens for newly diagnosed and relapsed ALL are now thought to represent the best available therapy, teniposide remains an investigational agent. In this review, we outline and discuss the conflicts arising from the need to answer drug-specific issues, and, at the same time, facilitate the implementation of innovative, curative regimens.

Platinum analogue combination chemotherapy: cisplatin and carboplatin--a phase I trial with pharmacokinetic assessment of the effect of cisplatin administration on carboplatin excretion.

Cisplatin (NSC 119875) and carboplatin (NSC 241240) are platinum (II) analogues with very different spectra of toxicity. Cisplatin dose is limited by nausea and vomiting, renal dysfunction, and dose-related peripheral neuropathy, whereas carboplatin is myelosuppressive. There are also clinical and laboratory data that suggest that these drugs may not be completely cross-resistant. Therefore, the following phase I trial of combination therapy with cisplatin and carboplatin was undertaken. Since carboplatin toxicity is enhanced in the presence of renal impairment, carboplatin excretion was also evaluated in selected patients at the maximum tolerated dose. Thirty-three patients received 50 mg/m2 cisplatin and doses of carboplatin between 160 mg/m2 and 400 mg/m2. Sequential 20-minute infusions of carboplatin and then cisplatin were able to be administered at the standard doses of carboplatin (320 and 400 mg/m2) with thrombocytopenia to the degree expected if carboplatin alone had been given. However, 280 mg/m2 carboplatin followed by 25 mg/m2 cisplatin/d X 3 caused unexpectedly severe thrombocytopenia in seven of eight patients (median platelet nadir 45,000/microL; range, 12 to 321,000/microL; nadir was less than 90,000 in seven of eight patients). In three patients treated with 280 mg/m2 carboplatin plus 25 mg/m2/d X 3 cisplatin, pharmacokinetics of carboplatin were compared during consecutive monthly cycles without and with cisplatin. Modestly increased areas under the curve (AUC) for carboplatin (15% and 35%) with cisplatin were seen in the two patients who experienced more pronounced platelet suppression with combination therapy. No other limiting or unusual toxicity was seen with this combination. Responses, primarily in "platinum responsive" tumors, were seen. The combination of cisplatin plus carboplatin is feasible and merits further study.

Phase I and pharmacokinetic trial of weekly oral fluorouracil given with eniluracil and low-dose leucovorin to patients with solid tumors.

PURPOSE: Fluorouracil (5-FU) given as a weekly, high-dose 24-hour infusion is active and tolerable. We evaluated an oral regimen of eniluracil (which inactivates dihydropyrimidine dehydrogenase [DPD]), 5-FU, and leucovorin to simulate this schedule. PATIENTS AND METHODS: Patients received a single 24-hour infusion of 5-FU (2,300 mg/m(2) on day 2) with leucovorin (15 mg orally [PO] bid on days 1 through 3) to provide reference pharmacokinetic data. Two weeks later, patients began treatment with eniluracil (20 mg) and leucovorin (15 mg) (PO bid on days 1 through 3) and 5-FU (10 to 15 mg/m(2) PO bid on day 2). RESULTS: Dose-limiting toxicity (diarrhea, neutropenia, and fatigue) was seen with 5-FU 15 mg/m(2) PO bid on day 2 given weekly for either 6 of 8 weeks or 3 of 4 weeks, whereas five of seven patients tolerated 5-FU 10 mg/m(2) PO bid given weekly for 3 of 4 weeks. Eniluracil led to a 35-fold reduction in 5-FU clearance. Fluoro-beta-alanine, a 5-FU catabolite, was not detected in plasma during oral 5-FU-eniluracil therapy. DPD activity was markedly suppressed in all patients during eniluracil therapy; the inactivation persisted after the last eniluracil dose; percentages of baseline values were 1.8% on day 5, 4.5% on day 12, and 23.6% on day 19. CONCLUSION: The recommended oral dosage of 5-FU (10 mg/m(2) PO bid) given with eniluracil and leucovorin is approximately 115-fold lower than the reference dosage for 24-hour infusional 5-FU. This difference is greater than expected given the reduction in 5-FU clearance. DPD inactivation persisted for several weeks after completion of eniluracil therapy.

A pilot study of interferon alfa-2a in combination with fluorouracil plus high-dose leucovorin in metastatic gastrointestinal carcinoma.

Thirty-one assessable patients with metastatic adenocarcinoma of the gastrointestinal tract were entered onto a pilot study designed to assess the impact of recombinant interferon alpha-2a (rIFN alpha-2a) on the toxicity and pharmacokinetics of fluorouracil (5-FU) and leucovorin (LV). Patients received an initial cycle of 5-FU (370 or 425 mg/m2/d) with LV (500 mg/m2/d) for 5 days. If tolerated, the patient received the same dose of 5-FU/LV for the second cycle on days 2 to 6, with rIFN alpha-2a at 5 x 10(6) or 10 x 10(6) U/m2/d on days 1 to 7, or with 3 x 10(6) U/m2/d on days 1 to 14. In 26 matched cycles, rIFN alpha-2a administration was associated with an increased incidence of dose-limiting mucositis and diarrhea and a significantly lower median platelet nadir; rIFN alpha-2a did not significantly affect the median WBC or granulocyte nadir. Dose-limiting toxicity occurred in all six patients entered at 425 mg/m2/d of 5-FU/LV within two cycles. The majority of patients treated with 370 mg/m2/d of 5-FU/LV and 10 x 10(6) U/m2/d rIFN alpha-2a experienced grade 3 to 4 mucositis and diarrhea, whereas patients receiving 3 x 10(6) and 5 x 10(6) U/m2/d rIFN alpha-2a had acceptable toxicity. Administration of rIFN alpha-2a was associated with a dose-dependent decrease in 5-FU clearance. The increase in the area under the 5-FU concentration-time curve (AUC) was 1.3-fold and 1.5-fold in patients receiving 5 x 10(6) and 10 x 10(6) U/m2/d rIFN alpha-2a, respectively. Thus, the increase in 5-FU toxicity with rIFN alpha-2a may be explained by alterations in 5-FU pharmacokinetics. In 22 patients without prior 5-FU therapy, three complete (13.6%) and seven partial (31.8%) responses were seen, for an overall response rate of 45.4% (95% confidence interval, 24.4% to 67.8%). Since the 5 x 10(6) U/m2/d dose of rIFN alpha-2a increased the 5-FU drug exposure and was associated with acceptable toxicity, we recommend its further evaluation as given on days 1 to 7 in combination with 5-FU 370 mg/m2/d, with high-dose LV given on days 2 to 6.

Phase II study of fluorouracil, leucovorin, and interferon alfa-2a in metastatic colorectal carcinoma.

PURPOSE: To test the activity of a regimen of interferon alfa-2a (IFN alpha-2a) 5 x 10(6) U/m2 subcutaneously (SC) days 1 through 7 combined with leucovorin 500 mg/m2/d intravenously (IV) over 30 minutes and fluorouracil (5-FU) 370 mg/m2/d through IV push 1 hour after leucovorin days 2 through 6 in a phase II study. PATIENTS AND METHODS: Forty-six patients with a good performance status (PS) with measurable colorectal cancer and no prior therapy for metastatic disease were entered. Cycles were repeated at 3-week intervals if toxicity had resolved. The 5-FU dose was increased by 15% if toxicity was mild, and decreased by 15% for grade 3 to 4 nonhematologic or grade 4 hematologic toxicity. RESULTS: Three complete responses (CRs) and 21 partial responses (PRs) were seen among 44 assessable patients (54%; 95% confidence interval, 39% to 70%). A moderately strong association was noted between PS and response: PS O (n = 26), two CRs and 15 PRs (65%); PS 1 (n = 13), one CR and six PRs (54%); PS 2 (n = 5), zero CRs and zero PRs (0%; two-tailed P = .026). With a median follow-up duration of 18.8 months, the median time to treatment failure (TTF) and survival were 7.8 months and 16.3 months, respectively. Doses were escalated to 425 mg/m2/d 5-FU in 10 patients, but only four tolerated the higher dose. When expressed as the most severe degree of toxicity experienced by each patient across all cycles, grade 3 to 4 toxicity of the following types was observed; mucositis, 37%; diarrhea, 40%; rash, 7%; fatigue, 14%; granulocytopenia, 13%. Dose-limiting toxicity at 370 mg/m2/d 5-FU eventually occurred in 28 patients (61%). Twelve patients (26%) required an IFN alpha-2a dose reduction for constitutional toxicity. CONCLUSION: This regimen has promising activity in advanced colorectal cancer, particularly in patients with an Eastern Cooperative Oncology Group (ECOG) PS of 0 to 1.

Pharmacodynamics and pharmacokinetics of a 72-hour infusion of 9-aminocamptothecin in adult cancer patients.

PURPOSE: To investigate the pharmacokinetics and pharmacodynamics of 9-aminocamptothecin (9-AC) infused over 72 hours at doses of 5 to 74 micrograms/m2/h. PATIENTS AND METHODS: 9-AC lactone and total (lactone plus carboxylate) plasma concentrations were measured in 44 patients with solid tumors using a high-performance liquid chromatography (HPLC) assay. Fifteen patients underwent extended pharmacokinetic sampling to determine the distribution and elimination kinetics of 9-AC. RESULTS: At steady-state, 8.7% +/- 4.7% (mean +/- SD) of the total drug circulated in plasma as the active 9-AC lactone. Clearance of 9-AC lactone was uniform (24.5 +/- 7.3 L/h/m2) over the entire dose range examined; however, total 9-AC clearance was nonlinear and increased at higher dose levels. In 15 patients treated at dose levels > or = 47 micrograms/m2/h, the volume of distribution at steady-state for 9-AC lactone was 195 +/- 114 L/m2 and for total 9-AC it was 23.6 +/- 10.6 L/m2. The elimination half-life was 4.47 +/- 0.53 hours for 9-AC lactone and 8.38 +/- 2.10 hours for total 9-AC. In pharmacodynamic studies, dose-limiting neutropenia correlated with steady-state lactone concentrations (Css) R2 = .77) and drug dose (R2 = .71). CONCLUSION: Plasma 9-AC concentrations rapidly declined to low levels following the end of a 72-hour infusion and the mean fraction of total 9-AC circulating in plasma as the active lactone was less than 10%. The pharmacokinetics of 9-AC may have a great impact on its clinical activity and should be considered in the design of future clinical trials of this topoisomerase I inhibitor.