A randomized comparison between rasburicase and allopurinol in children with lymphoma or leukemia at high risk for tumor lysis.

Standard therapy in the United States for malignancy-associated hyperuricemia consists of hydration, alkalinization, and allopurinol. Urate oxidase catalyzes the enzymatic oxidation of uric acid to a 5 times increased urine soluble product, allantoin. Rasburicase is a new recombinant form of urate oxidase available for clinical evaluation. This multicenter randomized trial compared allopurinol to rasburicase in pediatric patients with leukemia or lymphoma at high risk for tumor lysis. Patients received the assigned uric acid-lowering agent for 5 to 7 days during induction chemotherapy. The primary efficacy end point was to compare the area under the serial plasma uric acid concentration curves during the first 96 hours of therapy (AUC(0-96)). Fifty-two patients were randomized at 6 sites. In an intent-to-treat analysis, the mean uric acid AUC(0-96) was 128 +/- 70 mg/dL.hour for the rasburicase group and 329 +/- 129 mg/dL.hour for the allopurinol group (P <.0001). The rasburicase versus allopurinol group experienced a 2.6-fold (95% CI: 2.0-3.4) less exposure to uric acid. Four hours after the first dose, patients randomized to rasburicase compared to allopurinol achieved an 86% versus 12% reduction (P <.0001) of initial plasma uric acid levels. No antirasburicase antibodies were detected at day 14. This randomized study demonstrated more rapid control and lower levels of plasma uric acid in patients at high risk for tumor lysis who received rasburicase compared to allopurinol. For pediatric patients with advanced stage lymphoma or high tumor burden leukemia, rasburicase is a safe and effective alternative to allopurinol during initial chemotherapy.

Plasma pharmacokinetics and cerebrospinal fluid penetration of thioguanine in children with acute lymphoblastic leukemia: a collaborative Pediatric Oncology Branch, NCI, and Children's Cancer Group study.

PURPOSE: In preclinical studies, thioguanine (TG) has been shown to be more potent than the standard acute lymphoblastic leukemia (ALL) maintenance agent, mercaptopurine (MP), suggesting that TG may be more efficacious than MP in the treatment of childhood ALL. As part of a pilot trial in which TG was used in place of MP, we studied the plasma pharmacokinetics of oral TG and measured steady-state plasma and CSF TG concentrations during a continuous intravenous infusion (CIVI) in children with newly diagnosed standard-risk ALL. METHODS: Nine plasma samples were collected after each patient's first 60 mg/m2 oral TG dose during maintenance. CIVI TG (20 mg/m2/h over 24 h) was administered during the consolidation phase of therapy, and simultaneous plasma and CSF samples were collected near the end of the infusion. TG was measured by reverse-phase HPLC with ultraviolet detection. Erythrocyte TG nucleotide (TGN) concentrations were measured 7 days after a course of CIVI TG and prior to the start of each maintenance cycle. RESULTS: After oral TG (n = 35), the mean (+/- SD) peak plasma concentration was 0.46 +/- 0.68 microM and the AUC ranged from 0.18 to 9.5 microM.h (mean 1.5 microM.h). Mean steady-state plasma and CSF TG concentrations during CIVI (n = 33) were 2.7 and 0.5 microM, respectively. The mean (+/- SD) TG clearance was 935 +/- 463 ml/min per m2. Plasma TG concentrations did not correlate with erythrocyte TGN concentrations after oral or CIVI TG. The 8-OH-TG metabolite was detected in plasma and CSF. CONCLUSIONS: TG concentrations that are cytotoxic to human leukemia cell lines can be achieved in plasma after a 60 mg/m2 oral dose of TG and in plasma and CSF during CIVI of TG.

Treatment of rheumatoid arthritis with a DR4/1 peptide.

OBJECTIVE: To determine the safety and potential clinical efficacy of primary and booster injections of a DR4/1 peptide in patients with active rheumatoid arthritis (RA) despite methotrexate therapy. METHODS. Subjects with active RA were enrolled in a randomized, placebo controlled, double blind, dose-escalating clinical trial of synthetic DR4/1 peptide containing the shared epitope. The primary injection of the DR4/1 peptide in alum adjuvant was administered at one of 3 doses, 1.3, 4.0, and 13 mg, followed by up to 3 or 4 booster injections every 6 or 8 weeks at the same dose. The primary outcomes were the occurrence of adverse effects and changes in measures of immune function. Clinical efficacy was assessed using the American College of Rheumatology 20% criteria for clinical improvement. RESULTS: Fifty-three patients were entered into the trial, including 44 who completed the study. In the absence of any observations of a dose response to the DR4/1 peptide injections, the 3 dosage groups were combined for subsequent analysis into 3 groups: patients receiving DR4/1 peptide injections every 6 weeks, patients receiving DR4/1 peptide injections every 8 weeks, and a placebo group. At all doses and each dosing interval the primary and booster injections of synthetic DR4/1 peptide were well tolerated and did not produce any significant changes in lymphocyte counts or evidence of generalized immunosuppression. Analysis of clinical efficacy showed that the 6 week group had trends toward improvement in disease measures. CONCLUSION: Primary and booster injections of the DR4/1 peptide containing the shared epitope were safe and did not broadly suppress immune function.

A phase I trial of solubilized DR2:MBP84-102 (AG284) in multiple sclerosis.

OBJECTIVE: To assess the safety, tolerability, and biologic and clinical activity of a solubilized complex comprised of human leukocyte antigen-DR2 with myelin basic protein84-102 (AG284)in patients with secondary progressive MS. BACKGROUND: Soluble species-specific major histocompatibility complex myelin basic protein91-103 complexes ameliorate disease in a dose-dependent manner when administered to SJL/J mice with chronic relapsing experimental allergic encephalomyelitis. Preincubation with AG284 reduces the proliferative response of a DR2-restricted, myelin basic protein84-102-reactive T cell clone, derived from a MS patient, to myelin basic protein84-102 in the presence of autologous antigen-presenting cells. METHODS: Thirty-three patients with secondary progressive MS were randomly assigned to receive three alternate day IV doses of AG284 or placebo in a double-masked dose escalation study. The primary outcome was safety and tolerability. Secondary outcomes included a comparison of pre- and post-treatment gadolinium-enhanced brain MRI activity, Kurtzke Expanded Disability Status Scale, and Nine Hole Peg Test scores. RESULTS: The frequency of adverse events was similar in the AG284 and placebo recipients. No significant treatment effect was detected by Expanded Disability Status Scale, Nine Hole Peg Test, or number of new gadolinium-enhancing MRI lesions. CONCLUSIONS: AG284 as administered during this study was safe and well tolerated. Further studies are warranted to determine the biologic activity and clinical efficacy of this potential treatment for MS.

Liposomal amphotericin B for empirical therapy in patients with persistent fever and neutropenia. National Institute of Allergy and Infectious Diseases Mycoses Study Group.

BACKGROUND: In patients with persistent fever and neutropenia, amphotericin B is administered empirically for the early treatment and prevention of clinically occult invasive fungal infections. However, breakthrough fungal infections can develop despite treatment, and amphotericin B has substantial toxicity. METHODS: We conducted a randomized, double-blind, multicenter trial comparing liposomal amphotericin B with conventional amphotericin B as empirical antifungal therapy. RESULTS: The mean duration of therapy was 10.8 days for liposomal amphotericin B (343 patients) and 10.3 days for conventional amphotericin B (344 patients). The composite rates of successful treatment were similar (50 percent for liposomal amphotericin B and 49 percent for conventional amphotericin B) and were independent of the use of antifungal prophylaxis or colony-stimulating factors. The outcomes were similar with liposomal amphotericin B and conventional amphotericin B with respect to survival (93 percent and 90 percent, respectively), resolution of fever (58 percent and 58 percent), and discontinuation of the study drug because of toxic effects or lack of efficacy (14 percent and 19 percent). There were fewer proved breakthrough fungal infections among patients treated with liposomal amphotericin B (11 patients [3.2 percent]) than among those treated with conventional amphotericin B (27 patients [7.8 percent], P=0.009). With the liposomal preparation significantly fewer patients had infusion-related fever (17 percent vs. 44 percent), chills or rigors (18 percent vs. 54 percent), and other reactions, including hypotension, hypertension, and hypoxia. Nephrotoxic effects (defined by a serum creatinine level two times the upper limit of normal) were significantly less frequent among patients treated with liposomal amphotericin B (19 percent) than among those treated with conventional amphotericin B (34 percent, P<0.001). CONCLUSIONS: Liposomal amphotericin B is as effective as conventional amphotericin B for empirical antifungal therapy in patients with fever and neutropenia, and it is associated with fewer breakthrough fungal infections, less infusion-related toxicity, and less nephrotoxicity.

Phase I study of topotecan administered as a 21-day continous infusion in children with recurrent solid tumors: a report from the Children's Cancer Group.

The purpose of this study was to determine the toxicity, maximum tolerated dose, and pharmacokinetics of a 21-day continuous infusion of topotecan in children with relapsed solid tumors. Fifteen patients received 40 courses of continuous ambulatory infusions of topotecan every 28 days or when there was resolution of hematological toxicity and any grade 2 or greater nonhematological toxicity. The starting dose was 0.4 mg/m2/day. Total topotecan levels were measured on days 1, 7, 14, and 21. Three of four patients who received a starting dose of 0.4 mg/m2/day experienced dose-limiting myelosuppression. At the reduced dose of 0.3 mg/ m2/day, only two of the seven patients experienced dose-limiting myelosuppression. Subsequently, four patients with more limited prior therapy were treated with 0.4 mg/m2/ day; three had dose-limiting myelosuppression. Two patients with a dose-limiting toxicity at 0.4 mg/m2/day tolerated additional courses at 0.3 mg/m2/day. An equal number of patients had grade 4 neutropenia or thrombocytopenia. Other adverse events were rare. Two patients with ependymoma, one with rhabdomyosarcoma, and one with retinoblastoma metastatic to the brain had objective responses. The steady state plasma concentration and clearance of topotecan (Css) was achieved by day 1. Css in six patients with complete data were 1.44 +/- 0.50 and 2.13 +/- 0.83 ng/ml at 0.3 and 0.4 mg/m2/day, respectively. Thus, a 21-day topotecan infusion was well-tolerated at 0.3 mg/m2/day. Myelo-suppression was the dose-limiting toxicity at 0.4 mg/m2/day. The steady state and clearance of topotecan in this study are similar to those reported in adult patients.

High-dose trimetrexate and minimal-dose leucovorin: a case for selective protection?

Our objective was to find the minimum dose of leucovorin (LV; 5-formyltetrahydrofolate) needed to potentially provide selective protection of normal tissue in patients with tumors resistant to methotrexate (MTX) by virtue of transport during prolonged therapy with high-dose trimetrexate (TMTX). Based upon the known daily requirement for folate, that tumors are often resistant to methotrexate via a transport-based mechanism, and that large doses of trimetrexate can be given with large doses of leucovorin for the treatment of patients with Pneumocystis carinii, a protocol was designed to find the minimum LV dose required to allow the administration of large doses of TMTX. Patients were treated in 28-day cycles consisting of 14 consecutive days of oral TMTX (45 mg/m2 every 12 h), followed by 14 days of rest. The dose of concurrent LV was started at 5 mg/m2 twice daily. Cohorts of patients received successive half doses of LV so long as three consecutive patients had less than or equal to grade 3 toxicity. Ten patients received 29 courses of therapy. The most common toxicities encountered were thrombocytopenia (38%), mucositis (14%), and neutropenia (10%). At a LV dose of 2.5 mg/m2, toxicities were consistently limited to less than or equal to grade 3 and only one episode of grade 4 hematological toxicity. Although there was marked interpatient variability, the minimally effective LV dose for selective protection seems to be 2.5 mg/m2. If tumors are resistant to methotrexate because of decreased transport of drug (and also folate), then the same pharmacological principle used to develop TMTX/LV for the treatment of P. carinii may be applied to treatment of some patients with cancer.

Pharmacokinetics and pharmacodynamics of oral methotrexate and mercaptopurine in children with lower risk acute lymphoblastic leukemia: a joint children's cancer group and pediatric oncology branch study.

We prospectively assessed the pharmacokinetics of methotrexate, mercaptopurine, and erythrocyte thioguanine nucleotide levels in a homogenous population of children with lower risk acute lymphoblastic leukemia and correlated pharmacokinetic parameters with disease outcome. The maintenance therapy regimen included daily oral mercaptopurine (75 mg/m2) and weekly oral methotrexate (20 mg/m2). One hundred ninety-one methotrexate doses and 190 mercaptopurine doses were monitored in 89 patients. Plasma drug concentrations of both agents were highly variable. The area under the plasma concentration-time curve (AUC) of methotrexate ranged from 0.63 to 12 micromol*h/L, and the AUC of mercaptopurine ranged from 0.11 to 8 micromol*h/L. Drug dose, patient age, and duration of therapy did not account for the variability. Methotrexate AUC was significantly higher in girls than boys (P =.007). There was considerable intrapatient variability for both agents. Erythrocyte thioguanine nucleotide levels were also highly variable (range, 0 to 10 pmol/g Hgb) and did not correlate with mercaptopurine dose or AUC. A Cox regression analysis showed that mercaptopurine AUC was a marginally significant (P =.043) predictor of outcome, but a direct comparison of mercaptopurine AUC in the remission and relapsed patient groups failed to show a significant difference. Methotrexate and mercaptopurine plasma concentrations and erythrocyte thioguanine nucleotide levels were highly variable, but measurement of these pharmacokinetic parameters at the start of maintenance will not distinguish patients who are more likely to relapse.

Randomized placebo-controlled trial of granulocyte-macrophage colony-stimulating-factor support for dose-intensive cyclophosphamide, etoposide, and cisplatin.

This is a double-blind randomized placebo-controlled trial to evaluate the efficacy and safety of granulocyte-macrophage colony-stimulating-factor (GM-CSF) after dose-intensive cyclophosphamide, etoposide, and cisplatin (DICEP). Fifty-six patients with lymphoma or breast carcinoma were randomized to receive GM-CSF 250 microg/m2 or placebo subcutaneously (SC) every 12 hr after each course of DICEP until recovery of absolute neutrophil count (ANC) of 1.5 x 10(9)/L. Each patient was to receive three courses of DICEP. There were 28 patients in each group. The median duration of ANC below 0.5 x 10(9)/L was 10 versus 12 days for Course 1 (P = 0.010), 10 versus 12 days for Course 2 (P = 0.248), and 16.5 versus 15 days for Course 3 (P = 0.126); platelet counts below 20 x 10(9)/L was 4 versus 4 days for Course 1 (P = 0.586), 8.5 versus 7 days for Course 2 (P = 0.013), and 23.5 versus 10.5 days for Course 3 (P = 0.104); hospitalization for patients readmitted with cytopenic fever were 4 versus 8 days for Course 1 (P = 0.035); 7 versus 6 days for Course 2 (P = 0.692); and 8 versus 12 days for Course 3 (P = 0.884) in the GM-CSF and placebo group, respectively. GM-CSF significantly shortens the duration of neutropenia and readmission only during the first course of DICEP. There was a delay in platelet recovery and an increase in transfusion requirement during subsequent courses in the GM-CSF group. The result cautions the routine use of lineage specific hematopoietic growth factors in supporting repeated cycles of dose-intensive chemotherapy.

cDNA cloning by inverse polymerase chain reaction.

Since the first report on cDNA cloning in 1972 (1), this technology has been developed into a powerful and universal tool in the isolation, characterization, and analysis of both eukaryotic and prokaryotic genes. But the conventional methods of cDNA cloning require much effort to generate a library that is packaged in phage or plasmid and then to survey a large number of recombinant phages or plasmids. There are three major limitations of those methods. First, a substantial amount (at least 1 µg) of purified mRNA is needed as starting material to generate libraries of sufficient diversity (2). Second, the intrinsic difficulty of multiple sequential enzymatic reactions required for cDNA cloning often leads to low yields and truncated clones (3). Finally, screening of a library with hybridization technique is time-consuming.

Amplification of gene ends from gene libraries by polymerase chain reaction with single-sided specificity.

Isolation of a full-length gene on the basis of a limited sequence information is often troublesome and challenging. Tremendous effort is needed to isolate a specific gene by screening cDNA or genomic libraries by oligonucleotide or nucleic acid probes. In those methods, basically nucleic acid probes are used in a screening process to check whether or not a plaque or a colony contains the sequence of interest. There have been attempts to isolate specific DNA fragments using immobilized DNA, in which particular DNA fragments were enriched by hybrid selection and then the concentrated library was screened by a specific DNA probe (1,2). Recently, polymerase chain reaction (PCR) has been applied to the cloning of genes. Friedmann et al. (3) first used PCR to screen λgt11 library with two gene-specific primers. This protocol can be effectively used to isolate a particular DNA fragment between two specific primers or to generate nucleic acid probe from cDNA libraries. The unknown sequences flanking the fragment between the two specific primers cannot be amplified by this method.

Determination of the maximum tolerated dose of idarubicin when used in a combination chemotherapy program of reinduction of childhood ALL at first marrow relapse and a preliminary assessment of toxicity compared to that of daunorubicin: a report from the Childrens Cancer Study Group.

An escalating-dose trial of idarubicin, used weekly for 3 doses in combination with vincristine, prednisone, and L-asparaginase (VPLI), to reinduce remission of childhood ALL at first bone marrow relapse was conducted by the Childrens Cancer Study Group (CCSG). The maximum tolerated dose (MTD) of idarubicin, used in the manner, was determined to be 12.5 mg/m2/dose. Twelve of 16 (75%) evaluable patients in first marrow relapse of ALL treated at a dose of 10 or 12.5 mg/m2 entered a second complete remission, compared to 41 of 69 evaluable patients (59%) treated in a comparable way with daunorubicin (30 mg/m2) (VPLD). Prolonged myelosuppression was observed in both groups, but the frequency of documented bacterial sepsis and the duration of required hospitalization were greater among patients treated with idarubicin. No additional toxicity, specifically attributable to idarubicin, was observed at these doses.

Phase I/II trial and pharmacokinetics of intrathecal diaziquone in refractory meningeal malignancies.

PURPOSE: Because there is a compelling need to develop new agents for intrathecal use, we investigated the safety, efficacy, and CSF pharmacokinetics of diaziquone (AZQ) following intrathecal administration in patients with refractory meningeal malignancies. PATIENTS AND METHODS: Thirty-nine patients received 45 courses of intrathecal AZQ. Two schedules were studied; twice-weekly administration of a 1- or 2-mg dose and "concentration times time" (C x T) administration of 0.5 mg every 6 hours for three doses, administered once weekly. RESULTS: Dose-limiting toxicity consisting of headache, nausea, or vomiting occurred in only three patients and only at the 2-mg, twice weekly dose. The schedules of 1 mg twice-weekly and 0.5 mg every 6 hours for three doses were well tolerated. Thirty-seven courses were assessable for response. The overall response rate was 62%. Complete responses (CRs) occurred in 14 of 37 courses (38%) and partial responses (PRs) occurred in nine of 37 courses (24%). Among patients with meningeal leukemia, CRs were observed in 11 of 26 courses (42%) and PRs in nine of 26 courses (35%). There was no difference in response rate related to dose or schedule. The pharmacokinetic behavior of intrathecally administered AZQ was characterized by biexponential disappearance from ventricular CSF, with mean half-lives of 18.2 and 78.6 minutes. The mean clearance rate was 0.37 mL/min. CONCLUSION: Intrathecal AZQ is safe, well tolerated, and highly active against refractory meningeal malignancies.

Intrathecal 6-mercaptopurine: preclinical pharmacology, phase I/II trial, and pharmacokinetic study.

For over 30 years, oral 6-mercaptopurine (6-MP) has been a mainstay of systemic maintenance therapy for acute lymphoblastic leukemia. Despite its efficacy as an antileukemic agent, 6-MP has not been previously administered by the intrathecal (IT) route. In anticipation of a clinical trial of IT 6-MP, preclinical cytotoxicity and pharmacology studies were performed to define a safe, effective dose. The optimal concentration (greater than 1 microM) and duration of exposure (greater than 12 h) to 6-MP required for cytotoxicity were determined in vitro using human leukemia cell lines. The dose required to achieve the desired cerebrospinal fluid concentrations in humans was derived from pharmacokinetic parameters determined in rhesus monkeys. A phase I/II study was then performed in pediatric patients with refractory meningeal leukemia. Nine patients (aged 3.5 to 16 years) with chronic meningeal leukemia (2 to 6 central nervous system relapses) were entered onto the study. All had previously failed, at a minimum, IT methotrexate, IT cytarabine, and cranial (+/- spinal) radiation. A 10-mg IT dose of 6-MP (calculated to produce cytotoxic cerebrospinal fluid levels for 12 h) was administered twice weekly for 4 weeks. There were four complete responses and three partial responses. The duration of complete responses ranged from 7 to 22 weeks. Observed toxicities were not dose limiting and included mild headache (three patients) and minimal nausea (two patients). Pharmacokinetic studies performed in patients confirmed that cerebrospinal fluid concentrations of 6-MP were greater than 1 microM for 12 h. These results indicate that the IT administration of 6-MP is feasible, is not associated with significant toxicity, and has definite activity in patients with refractory meningeal leukemia.

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.

Hepatic function and drug pharmacokinetics after total body irradiation plus bone marrow transplant.

Radiation nephritis is the principle late toxicity seen after total body irradiation in barrier-maintained rats when hematologic toxicity is prevented by bone marrow transplantation. Renal dysfunction is observed for single doses as low as 7.5 Gy. Hepatic blood flow, as measured by indocyanine green clearance, is decreased after 8.5-9.5 Gy single-dose total body irradiation. Serum albumin levels are decreased after 9.5 Gy single-dose total body irradiation. Hypoalbuminemia is a symptom of hepatic damage, but can also be caused by renal damage or edema. No decrease in total serum protein is observed, indicating that proteinuria resulting from renal damage is not the cause of hypoalbuminemia. No edema and some dehydration are observed. These data indicate that hepatic damage as well as renal damage may be occurring after total body irradiation plus bone marrow transplantation. Animals given total body irradiation plus bone marrow transplantation show decreased tolerance to a wide variety of immunosuppressive and cytotoxic drugs, even when these drugs are given months after total body irradiation. Altered drug clearance after total body irradiation plus bone marrow transplantation is observed for cis-platinum, vincristine, and adriamycin. The increase in cis-platinum toxicity after total body irradiation plus bone marrow transplantation is caused by decreased renal drug clearance. The decrease in vincristine tolerance and the alterations in adriamycin and vincristine pharmacokinetics are caused by altered drug distribution after total body irradiation plus bone marrow transplantation. These results indicate that bone marrow transplant survivors may show altered clearance of, and decreased tolerance to, a wide variety of drugs that are used after bone marrow transplantation.

Pharmacology of fludarabine phosphate after a phase I/II trial by a loading bolus and continuous infusion in pediatric patients.

Fludarabine phosphate is a nucleotide analogue of adenine arabinoside with antitumor activity in murine and human lymphoid malignancies; it has occasional, unpredictable neurotoxicity after high dose bolus injections in adults. To avoid this toxicity, we studied a loading dose plus 5-day continuous infusion in 47 evaluable pediatric patients. Dose limiting myelosuppression was seen in children with solid tumors after a loading dose of 8 mg/m2 followed by 23.5 mg/m2/day for 5 days. In children with leukemia, no dose limiting toxicity was seen at dose level 6, consisting of a loading dose of 10 mg/m2 and an infusion of 30.5 mg/m2/day for 5 days. One complete and 3 partial remissions were seen in 26 evaluable children with acute lymphoblastic leukemia. 9-beta-D-arabinofuranosyl-2-fluoroadenine plasma concentrations and the area under the moment curve increased linearly with dose. The terminal half-life was similar, while the total body clearance was shorter than that reported for adults receiving bolus or continuous doses. Lymphoblasts isolated from 2 patients during fludarabine phosphate (9-beta-D-arabinofuranosyl-2-fluoroadenine) treatment increased their ability to convert 1-beta-D-arabinofuranosylcytosine to 1-beta-D-arabinofuranosylcytosine 5'-triphosphate by more than 10-fold. The antileukemic activity of 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-phosphate and its ability to alter the metabolism of 1-beta-D-arabinofuranosylcytosine indicate that timed combinations of these 2 agents should be tested.