The association of environmental factors with neurocognitive outcomes in survivors of childhood acute lymphoblastic leukemia (ALL).

PURPOSE: To investigate the association of environmental factors, rehabilitation services during therapy and socioeconomic status (SES - insurance type), with neurocognitive outcomes at the end of therapy for survivors of childhood acute lymphoblastic leukemia (ALL). METHODS: Survivors (n = 236) treated on the St. Jude Total Therapy Study 16 completed end of therapy testing with performance measures (IQ, attention, processing speed, fine motor skills, academics) and caregiver ratings (attention, executive function, adaptive skills). Environmental factors were abstracted from the medical record. RESULTS: Distribution of sex (47.3% female, p = 0.399), treatment arm (45.5% low risk, 54.5% standard/high risk p = 0.929), insurance type (47.7% private, 52.3% public/none, p = 0.117), and mean age at diagnosis (7.7 vs. 6.8 years, p = 0.143) were similar for groups with (n = 110; 46.6%) and without (n = 126; 53.6%) rehabilitation services during therapy. Compared to those without rehabilitation, the rehabilitation group (n = 110; 46.4%) had more caregiver reported problems with attention (Z = -0.28 vs. 0.43, p = 0.022), executive function (Z = -0.50 vs. -0.08, p = 0.003), and adaptive skills (Z = -0.41 vs.-0.13, p = 0.031). Among the rehabilitation group, there was no difference in outcomes by insurance status. Among those without rehabilitation, those with public insurance had worse neurocognitive outcomes than those with private insurance in IQ (Z = -0.04 vs. -0.45, p = 0.0115), processing speed (Z = -0.10 vs. -0.75, p = 0.0030), reading (Z = 0.18 vs. -0.59, p < 0.0001), and math (Z = -0.04 vs. -0.50, p = 0.0021). CONCLUSION: Participation in rehabilitation services during early intensive therapy is associated with end of therapy caregiver-reported neurocognitive outcomes in daily life.

Infection-related complications during treatment for childhood acute lymphoblastic leukemia.

Background: Comprehensive studies on neutropenia and infection-related complications in patients with acute lymphoblastic leukemia (ALL) are lacking. Patients and methods: We evaluated infection-related complications that were grade ≥3 on National Cancer Institute's Common Terminology Criteria for Adverse Events (version 3.0) and their risk factors in 409 children with newly diagnosed ALL throughout the treatment period. Results: Of the 2420 infection episodes, febrile neutropenia and clinically or microbiologically documented infection were seen in 1107 and 1313 episodes, respectively. Among documented infection episodes, upper respiratory tract was the most common site (n = 389), followed by ear (n = 151), bloodstream (n = 147), and gastrointestinal tract (n = 145) infections. These episodes were more common during intensified therapy phases such as remission induction and reinduction, but respiratory and ear infections, presumably viral in origin, also occurred during continuation phases. The 3-year cumulative incidence of infection-related death was low (1.0±0.9%, n = 4), including 2 from Bacillus cereus bacteremia. There was no fungal infection-related mortality. Age 1-9.9 years at diagnosis was associated with febrile neutropenia (P = 0.002) during induction and febrile neutropenia and documented infection (both P < 0.001) during later continuation. White race was associated with documented infection (P = 0.034) during induction. Compared with low-risk patients, standard- and high-risk patients received more intensive therapy during early continuation and had higher incidences of febrile neutropenia (P < 0.001) and documented infections (P = 0.043). Furthermore, poor neutrophil surge after dexamethasone pulses during continuation, which can reflect the poor bone marrow reserve, was associated with infections (P < 0.001). Conclusions: The incidence of infection-related death was low. However, young age, white race, intensive chemotherapy, and lack of neutrophil surge after dexamethasone treatment were associated with infection-related complications. Close monitoring for prompt administration of antibiotics and modification of chemotherapy should be considered in these patients.

The effect of body mass index at diagnosis on clinical outcome in children with newly diagnosed acute lymphoblastic leukemia.

The impact of body mass index (BMI) at diagnosis on treatment outcome in children with acute lymphoblastic leukemia (ALL) is controversial. We studied 373 children with ALL enrolled on the Total XV study, which prospectively used minimal residual disease (MRD) for risk assignment. MRD on day 19 and at the end of remission induction (day 46), cumulative incidence of relapse/refractory disease (CIR), event-free survival (EFS) and overall survival (OS) were evaluated using sets of four, three and two subgroups based on BMI at diagnosis, along with BMI percentile change during remission induction. Higher BMI was associated with older age and higher treatment risk. There was no association between MRD on days 19 or 46 and BMI for four, three or two BMI subgroups (P>0.1 in all cases), nor was BMI associated with CIR or EFS. Obese patients had worse OS compared with non-obese (P=0.031) due to treatment-related mortality and less salvage after refractory disease or bone marrow relapse. No association between BMI change during remission induction and MRD, CIR, EFS or OS was seen. BMI at diagnosis does not predict poorer response or relapse in a contemporary MRD-directed ALL regimen. Improvements in supportive care and innovative, less-toxic frontline/salvage therapies are needed, especially for obese patients.

Clinical impact of minimal residual disease in children with different subtypes of acute lymphoblastic leukemia treated with Response-Adapted therapy.

To determine the clinical significance of minimal residual disease (MRD) in patients with prognostically relevant subtypes of childhood acute lymphoblastic leukemia (ALL), we analyzed data from 488 patients treated in St Jude Total Therapy Study XV with treatment intensity based mainly on MRD levels measured during remission induction. MRD levels on day 19 predicted treatment outcome for patients with hyperdiploid >50 ALL, National Cancer Institute (NCI) standard-risk B-ALL or T-cell ALL, while MRD levels on day 46 were prognostic for patients with NCI standard-risk or high-risk B-ALL. Patients with t(12;21)/(ETV6-RUNX1) or hyperdiploidy >50 ALL had the best prognosis; those with a negative MRD on day 19 had a particularly low risk of relapse: 1.9% and 3.8%, respectively. Patients with NCI high-risk B-ALL or T-cell ALL had an inferior outcome; even with undetectable MRD on day 46, cumulative risk of relapse was 12.7% and 15.5%, respectively. Among patients with NCI standard-risk B-ALL, the outcome was intermediate overall but was poor if MRD was ⩾1% on day 19 or MRD was detectable at any level on day 46. Our results indicate that the clinical impact of MRD on treatment outcome in childhood ALL varies considerably according to leukemia subtype and time of measurement.

Genomewide Approach Validates Thiopurine Methyltransferase Activity Is a Monogenic Pharmacogenomic Trait.

We performed a genomewide association study (GWAS) of primary erythrocyte thiopurine S-methyltransferase (TPMT) activity in children with leukemia (n = 1,026). Adjusting for age and ancestry, TPMT was the only gene that reached genomewide significance (top hit rs1142345 or 719A>G; P = 8.6 × 10-61 ). Additional genetic variants (in addition to the three single-nucleotide polymorphisms [SNPs], rs1800462, rs1800460, and rs1142345, defining TPMT clinical genotype) did not significantly improve classification accuracy for TPMT phenotype. Clinical mercaptopurine tolerability in 839 patients was related to TPMT clinical genotype (P = 2.4 × 10-11 ). Using 177 lymphoblastoid cell lines (LCLs), there were 251 SNPs ranked higher than the top TPMT SNP (rs1142345; P = 6.8 × 10-5 ), revealing a limitation of LCLs for pharmacogenomic discovery. In a GWAS, TPMT activity in patients behaves as a monogenic trait, further bolstering the utility of TPMT genetic testing in the clinic.

Genetics of ancestry-specific risk for relapse in acute lymphoblastic leukemia.

The causes of individual relapses in children with acute lymphoblastic leukemia (ALL) remain incompletely understood. We evaluated the contribution of germline genetic factors to relapse in 2225 children treated on Children's Oncology Group trial AALL0232. We identified 302 germline single-nucleotide polymorphisms (SNPs) associated with relapse after adjusting for treatment and ancestry and 715 additional SNPs associated with relapse in an ancestry-specific manner. We tested for replication of these relapse-associated SNPs in external data sets of antileukemic drug pharmacokinetics and pharmacodynamics and an independent clinical cohort. 224 SNPs were associated with rapid drug clearance or drug resistance, and 32 were replicated in the independent cohort. The adverse risk associated with black and Hispanic ancestries was attenuated by addition of the 4 SNPs most strongly associated with relapse in these populations (for blacks: model without SNPs hazard ratio (HR)=2.32, P=2.27 × 10-4, model with SNPs HR=1.07, P=0.79; for Hispanics: model without SNPs HR=1.7, P=8.23 × 10-5, model with SNPs HR=1.31, P=0.065). Relapse SNPs associated with asparaginase resistance or allergy were overrepresented among SNPs associated with relapse in the more asparaginase intensive treatment arm (20/54 in Capizzi-methorexate arm vs 8/54 in high-dose methotrexate arm, P=0.015). Inherited genetic variation contributes to race-specific and treatment-specific relapse risk.

Genome-Wide Study Links PNPLA3 Variant With Elevated Hepatic Transaminase After Acute Lymphoblastic Leukemia Therapy.

Remission induction therapy for acute lymphoblastic leukemia (ALL) includes medications that may cause hepatotoxicity, including asparaginase. We used a genome-wide association study to identify loci associated with elevated alanine transaminase (ALT) levels after induction therapy in children with ALL enrolled on St. Jude Children's Research Hospital (SJCRH) protocols. Germline DNA was genotyped using arrays and exome sequencing. Adjusting for age, body mass index, ancestry, asparaginase preparation, and dosage, the PNPLA3 rs738409 (C>G) I148M variant, previously associated with fatty liver disease risk, had the strongest genetic association with ALT (P = 2.5 × 10-8 ). The PNPLA3 rs738409 variant explained 3.8% of the variability in ALT, and partly explained race-related differences in ALT. The PNPLA3 rs738409 association was replicated in an independent cohort of 2,285 patients treated on Children's Oncology Group protocol AALL0232 (P = 0.024). This is an example of a pharmacogenetic variant overlapping with a disease risk variant.

Efficacy and safety of rasburicase, a recombinant urate oxidase (Elitek), in the management of malignancy-associated hyperuricemia in pediatric and adult patients: final results of a multicenter compassionate use trial.

The recombinant urate oxidase, rasburicase (Elitek, Sanofi-Synthelabo, Inc.), has recently received regulatory approval for the prevention and treatment of hyperuricemia in children with leukemia, lymphoma, and solid tumors. Prior to approval, 682 children and 387 adults in the US and Canada received rasburicase on compassionate-use basis. Uric acid concentration declined rapidly in both adult and pediatric patients after rasburicase treatment. Similar responses were observed in patients treated with subsequent courses. Possible drug-related adverse events, including allergic reactions, were uncommon. These data confirm that rasburicase is effective and safe for the treatment and prophylaxis of children and adults with malignancy-associated hyperuricemia.

Overt testicular disease at diagnosis of childhood acute lymphoblastic leukemia: lack of therapeutic role of local irradiation.

To assess the prognosis of overt testicular disease at diagnosis of acute lymphoblastic leukemia, and any therapeutic role of irradiation for this involvement, we reviewed the data of 811 boys treated on St Jude studies Total X--XI (early period) and Total XII-XIV (recent period). In all, 19 boys (2.3%) had testicular disease at diagnosis. In the early period, patients with testicular leukemia had a poorer overall survival (OS) (P=0.003), event-free survival (EFS) (P=0.064), and higher cumulative incidence of relapse (P=0.041) than did other patients. During the recent period, patients with and without overt testicular leukemia did not differ in OS (P=0.257), EFS (P=0.102), or cumulative incidence of relapse (P=0.51). In a multivariate analysis, OS was lower for patients with testicular disease than for those without the involvement in the early period (P=0.047) but not in the recent one (P=0.75). Both patients who received irradiation for residual testicular disease at the end of induction subsequently died of leukemia. Of the other 17 patients who did not receive irradiation, only one developed testicular relapse in combination with bone marrow relapse. In conclusion, the prognostic impact of overt testicular disease has diminished. Irradiation appears to provide no survival advantage to this patient population.

Antisense RNA inhibition of phosphoprotein p18 expression abrogates the transformed phenotype of leukemic cells.

Phosphoprotein p18 was identified originally on the basis of its very high level of expression in leukemic cells of different lineages. Changes in the level of p18 accumulation and phosphorylation associated with induction of differentiation of leukemic cells suggested a potential role for this phosphoprotein in cellular proliferation and differentiation and possibly in malignant transformation. Recent studies have demonstrated that p18 plays an important role in cell cycle progression by serving as a substrate for p34(cdc2) kinase. These studies showed that inhibition of p18 expression in leukemic cells results in growth retardation and accumulation of cells in G(2)-M. In this study, we explore the potential role of p18 in cellular transformation by investigating the effects of inhibition of p18 expression on the malignant phenotype of K562 erythroleukemia cells. These studies show that antisense inhibition of p18 expression in leukemic cells results in growth arrest at a lower saturation density, loss of serum independence, and loss of anchorage-independent growth in vitro. In addition, inhibition of p18 expression results in a marked inhibition of tumorigenicity of leukemic cells in vivo in the severe combined immune deficiency mouse model. These studies demonstrate that the high level of p18 expression in leukemic cells is necessary for the maintenance of the transformed phenotype and suggest p18 as a potential target for antileukemic interventions.

Negative regulatory elements in the human ETS1 gene promoter.

The human ETS1 gene promoter contains binding sites for transcription factors AP1, AP2 and ETS. These factors have been previously shown to be positive regulators for the expression of the ETS1 gene. In our previous report it was inferred that the ETS1 gene promoter also contains negative regulatory elements that might balance and prevent the overexpression of the ETS1 gene product. The studies reported here show that the ETS1 gene promoter also contains binding site motifs for transcription factors PEA3 and OCT. By subjecting deletion constructs of the ETS1 gene promoter to functional analysis, two negative regulatory elements (NREs) were located: NRE1 was mapped to 230 nt at the 5' end of the promoter, and NRE2 was mapped to 350 nt located between the second OCT motif and a 120-base sequence downstream from the SacI site. These NREs can also reduce the activity of a heterogenous promoter. Gel mobility-shift assays showed that nuclear extracts from B-lymphoid (Daudi), T-lymphoid (HPB) and erthyromyeloid (K562) cells each form one major and several minor complexes with NRE1 and NRE2. The nuclear extract from promyelocytic (HL60) cells does not form complexes with either NRE1 or NRE2. The identification of NREs in the ETS1 gene promoter suggests that these elements play an important role in regulating the ETS1 gene expression in hematopoietic cells.

Pilot study of low-dose interleukin-11 in patients with bone marrow failure.

PURPOSE: Interleukin-11 (IL-11) is a thrombopoietic cytokine that attenuates postchemotherapy thrombocytopenia at doses of 50 microg/kg/d subcutaneously. Very little is known about the activity of IL-11 in patients with bone marrow failure states. PATIENTS AND METHODS: Our preliminary experience with IL-11 at doses of 50 microg/kg/d suggested that patients with bone marrow failure developed significant peripheral and pulmonary edema after the prolonged dosing necessary for treating these conditions. We, therefore, initiated a study of low-dose IL-11 (starting dose, 10 microg/kg/d). RESULTS: Sixteen patients were assessable for response. Six patients had diploid cytogenetics; the others had a variety of chromosomal abnormalities. Six (38%) of 16 patients showed a platelet response to IL-11, and two had a multilineage response (to IL-11 alone, n = 1; to IL-11 plus G-CSF and erythropoietin, n = 1). The median increase in peak platelet counts was 95 x 10(9)/L above baseline in the responders (range, increase of 55 x 10(9)/L to 130 x 10(9)/L above baseline). Responders included five of 11 patients with myelodysplasia and one of four patients with aplastic anemia. Response durations were 12, 13, 14+, 25, 30, and 30+ weeks. Side effects of IL-11 were mild (peripheral edema, n = 7; conjunctival injection, n = 7; myalgia, n = 1; all grade 1). Seven patients had no side effects. CONCLUSION: Our pilot study suggests that administration of low-dose IL-11 (10 microg/kg/d) can raise platelet counts without significant toxicity in selected thrombocytopenic patients with bone marrow failure.

High-dose mercaptopurine followed by intermediate-dose cytarabine in relapsed acute leukemia.

PURPOSE: This phase I/II study was designed to explore the feasibility, toxicity, and potential efficacy of administering high-dose continuous intravenous mercaptopurine (6MP) followed by intermediate-dose continuous intravenous cytarabine (Ara-C) to children with relapsed or unresponsive acute leukemia. PATIENTS AND METHODS: Twenty-three children with relapsed or unresponsive acute leukemia (13 myeloid, 10 lymphoid) were entered onto the study. After initial hydration and alkalinization, 1,000 or 1,250 mg/m2 of 6MP was administered by continuous intravenous infusion over 24 hours. Following another period of hydration, 500 mg/m2 of Ara-C was administered by continuous intravenous infusion daily for 4 days. In 17 children, plasma concentrations of 6MP were measured at hours 4, 24, and 27 of the 6MP infusions. Plasma concentrations of Ara-C were measured at hours 8, 24, 48, 72, and 96 of the Ara-C infusions. Intracellular Ara-C triphosphate (Ara-CTP) concentrations were measured in peripheral-blood leukemia cells of the five patients with sufficient cells for measurement. Children who developed remission received repeated courses of this regimen every 3 to 4 weeks until relapse or completion of 12 courses. RESULTS: Of 13 children with acute myeloid leukemia (AML), six developed complete remissions (CRs) lasting 7 months to nearly 4 years. Two children remain in CR with normal growth, development, and health 3 years after cessation of treatment. Of 10 children with acute lymphoid leukemia (ALL), one had a CR of 2 months' duration. Dose-limiting toxicity consisted of severe hematosuppression with fever, neutropenia, and serious infection. There were two toxic deaths. The mean steady-state plasma concentrations of 6MP were approximately 4 mumol/L and of Ara-C approximately 3 mumol/L. The median Ara-CTP concentration in peripheral-blood leukemia cells was 308 mumol/L at hour 8 of the Ara-C infusion. CONCLUSION: High-dose continuous intravenous 6MP followed by intermediate-dose intravenous Ara-C produced CRs of longer than 6 months in approximately half of children with relapsed or unresponsive AML. Further study of this drug regimen is justified.

Recombinant urate oxidase (rasburicase) in the prevention and treatment of malignancy-associated hyperuricemia in pediatric and adult patients: results of a compassionate-use trial.

To confirm the efficacy of recombinant urate oxidase (rasburicase) and to establish its safety profile, we reviewed the data on 173 children and 72 adults with malignancy who were treated with this new uricolytic agent in a compassionate-use trial. Rasburicase (0.20 mg/kg) was administered intravenously daily for 1 to 7 days and could be given every 12 h for the initial 72 h. Subsequent courses were allowed at a later date. Rasburicase produced a dramatic decrease in uric acid concentrations in all patients whether they received it for prophylaxis (n = 79) or treatment (n = 166) (P < 0.001 in all comparisons between the levels at diagnosis and those after treatment). The median post-treatment levels were 0.5 to 0.7 mg/dl. Repeated administrations were also effective in all 11 evaluable patients. Four children and five adults had mild adverse reactions that were drug related or of unknown etiology. In two of the children, the adverse events occurred during the second course. Rasburicase is highly effective and safe in the prophylaxis or treatment of malignancy- or chemotherapy-associated hyperuricemia in children and adults.

Engraftment of chronic prolymphocytic and T cell leukemia in SCID mice.

Engraftment of human acute leukemia cells in immunocompromised (SCID) mice has resulted in in vivo models for exploration of human tumor biology. Attempts at engraftment of chronic leukemia cells have been generally unsuccessful. We have engrafted cells from three human chronic leukemias in SCID mice. Cell populations were from two patients with chronic lymphocytic leukemia (CLL) and either increased proolymphocytes (CLL-Pro; patient 1), or prolymphocytic transformation (PLL; patient 2) and from a third patient with newly diagnosed T cell CLL. Both fresh and cryopreserved cells were used and were injected intravenously, intraperitoneally, or both, after conditioning with cyclophosphamide. In addition, cells derived from a mouse spleen engrafted with human leukemia were passaged into another mouse. The animals were observed daily for signs of disease or appearance of tumors and sacrificed when terminally ill. At intervals blood samples were obtained and analyzed for the presence of human cells or DNA. Human leukemic cells were demonstrated by polymerase chain reaction (PCR) analysis of the human DQalpha gene or positive staining for human leukocyte common antigen (LCA). The presence of Epstein-Barr virus (EBV)-positive cells was also investigated by PCR analysis. Disseminated tumors developed in most mice inoculated with cells from the first patient, and this was associated with shortened survival times. The methods of administration, use of fresh or frozen samples, or the size of the inoculum had no effect on the development of leukemia. Survival of the mouse receiving passaged cells was similar to mice inoculated with fresh cells. Extensive histologic, immunophenotypic, and DNA studies were performed on organs from mice engrafting with cells from patient 1. PCR analysis for EBV sequences was negative in the mice engrafting from all three cases. The successful engraftment of human CLL-Pro PLL and T cell CLL in SCID mice, and the reproducibility of this effect using frozen cells, will provide a model for exploration of disease biology and for investigations of new drugs or combinations that may be useful in the treatment of CLL.

Acute lymphoblastic leukemias from relapse engraft more rapidly in SCID mice.

It is generally believed that relapse of acute leukemia heralds progression of the disease into a more aggressive stage. The biological behavior of leukemic cells collected from four patients with adult acute lymphoblastic leukemia (ALL) prior to treatment and at relapse was studied after engraftment into 28 unconditioned mice with severe combined immunodeficiency (SCID). Leukemic cells engrafted in all but one mouse, with major differences observed in the growth and aggressiveness of the leukemias. Recipient mice of cells derived from all patients at relapse died more rapidly in overt leukemia than those which were injected with cells obtained prior to induction treatment (P=0.0002). SCID mice that received cells from one patient at the time of diagnosis also died in terminal leukemia. Other SCID mice however, that received cells from the remaining three patients prior to treatment developed occult leukemia that was detectable in the blood or bone marrow with the use of polymerase chain reaction (PCR) or flow cytometry only. Leukemic cells recovered from mice with terminal leukemia exhibited a larger proliferating fraction than cells originally injected (P=0.004). Our results demonstrate, that during the evolution from initial presentation to relapse, ALL cells may acquire biological properties which render them more aggressive in SCID mice.

Elitek-rasburicase: an effective means to prevent and treat hyperuricemia associated with tumor lysis syndrome, a Meeting Report, Dallas, Texas, January 2002.

Renal precipitation of uric acid associated with tumor lysis syndrome (TLS) is a major complication in the management of leukemia, lymphoma, and other drug-sensitive cancers. Management of hyperuricema has historically consisted of administration of allopurinol, hydration, alkalinization to maintain pH between 7.0 and 7.3, and in some cases diuresis. Allopurinol, a xanthine analogue, blocks xanthine oxidase and formation of uric acid. Urate oxidase converts uric acid to allantoin, which is 5-10 times more soluble than uric acid. Homo sapiens cannot express urate oxidase because of a nonsense mutation. Urate oxidase was initially purified from Aspergillus flavus fungus. Treatment with this nonrecombinant product had been effective in preventing renal precipitation of uric acid in cancer patients, but was associated with a relatively high frequency of allergic reactions. This enzyme was recently cloned from A. flavus and is now manufactured as a recombinant protein. Clinical trials have shown this drug to be more effective than allopurinol for prevention and treatment of hyperuricemia in leukemia and lymphoma patients. This drug has been approved in Europe as well as the US and several clinical trials are in progress to further determine its clinical utility in other patient subsets. The purpose of this meeting was to discuss usefulness of recombinant urate oxidase, also known as rasburicase, Fasturtec, and Elitek, for the management of TLS in certain cancer patients.

Low-dose oral etoposide-based induction regimen for children with acute lymphoblastic leukemia in first bone marrow relapse.

We evaluated the clinical response to low-dose etoposide in relapsed acute lymphoblastic leukemia (ALL). Of the 45 patients with ALL in first bone marrow relapse enrolled on the ALL R15 protocol, 44 had received epipodophyllotoxins during frontline therapy. In the first week of remission induction therapy, patients received etoposide (50 mg/m(2) per day) administered orally as a single agent once or twice daily. On Day 8, patients started to receive dexamethasone, vincristine, and L-asparaginase. Etoposide was administered until Day 22. Two courses of consolidation therapy were followed by continuation therapy or hematopoietic stem cell transplantation. After 7 days of single-agent etoposide treatment, peripheral blast cell counts (P=0.013) and percentages of bone marrow blasts (P=0.016) were significantly reduced. In all, 38 (84.4%) attained second remission. Only time to relapse was significantly associated with outcome (P=0.025): the 5-year event-free survival estimates (+/-se) were 52.0+/-9.6% for those with late relapse and 20.0+/-8.0% for those with early relapse. We conclude that low-dose etoposide administered orally has a cytoreductive effect in relapsed ALL.

The topoisomerase I inhibitor DX-8951f is active in a severe combined immunodeficient mouse model of human acute myelogenous leukemia.

The severe combined immunodeficient (SCID) mouse model of human acute myelogenous leukemia (AML) is a unique system for preclinical in vivo evaluation of the activity and toxicity of new agents. The topoisomerase I (topo I) inhibitor topotecan is active in patients with AML and myelodysplastic syndromes. DX-8951f is a novel topo I inhibitor with more potent antitumor effects than topotecan or CPT-11 in vitro. To study the in vivo activity of DX-8951f, 6-week-old female SCID mice received injections into the tail vein with 2 x 10(7) exponentially growing KBM-3 cells. In each experiment, three to five sets of five mice were treated with DX-8951f doses ranging from 7.5 to 80 mg/kg and at schedules of 1, 3, and 5 days; a control set of five mice was treated with the drug vehicle alone. One group received DX-8951f on day 7 of the inoculation with KBM-3 (early-treatment group). To study the activity of DX-8951f in advanced disease, a second group was treated 1 month after the inoculation, when the animals were developing symptoms (late-treatment group). The study end point was the duration of survival until death from leukemia, which was assessed clinically and by the presence of the human DQ alpha gene in tissue samples by PCR. Six experiments were conducted with 170 animals. Survival was higher in both the early- and late-treatment groups than in untreated controls, and the treated groups had significantly less central nervous system disease. Significantly improved survival was observed in animals treated early with 60 and 80 mg/kg as a single injection, with 15 and 20 mg/kg over 3 days, and with 7.5 and 10 mg/kg over 5 days. In the late-disease model (treatment starting on days 28-35), improved survival was observed with a single dose of 80 or 20 mg/kg over 5 days. Dose escalation was limited by dilution problems at the 1-day schedule and by toxicity (mainly gastrointestinal) of the prolonged schedules. Both efficacy and toxicity were dose schedule dependent, increasing with higher doses and prolonged exposure. By establishing the antileukemic activity of DX-8951f against human AML transplanted into SCID mice at doses below the LD10, our data provide a rationale for clinical evaluation of the drug in patients with AML and favor the use of prolonged administration.

Tallimustine, an effective antileukemic agent in a severe combined immunodeficient mouse model of adult myelogenous leukemia, induces remissions in a phase I study.

Despite progress in leukemia therapy, only 20-30% of patients with acute myelogenous leukemia (AML) are cured. 1-beta-D-arabinofuranosylcytosine- and topoisomerase II-reactive drugs are the primary therapeutic agents used. The aim of this study was to evaluate the potential activity of tallimustine in leukemia. In this study, we first investigated the efficacy and toxic effects of tallimustine, a distamycin-A derivative, in a human leukemia model in severe combined immunodeficient (SCID) mice. On the basis of its dramatic activity in this preclinical study, a Phase I study of tallimustine at a starting dose of 300 microgram/m2/day for 3 days every 3-4 weeks was conducted in patients with refractory or relapsed leukemia. In SCID mice grafted with a human myelomonocytic leukemia cell line, tallimustine resulted in complete remission of disease in most mice at tolerable dosages ranging from 0.86 to 3.0 mg/kg/day for 3 days and was combined effectively and safely with a 2-day schedule of high-dose ara-C. In the Phase I study, 26 patients with refractory or relapsed leukemia were treated. The maximum tolerated dose was 900 microgram/m2/day for 3 days every 3-4 weeks. This dose was 3 times higher than the maximum tolerated dose in solid tumors and was limited by severe mucositis. Magnesium and potassium wasting were also observed, but other side effects (fatigue and gastrointestinal) were minor. Two (8%) patients with AML achieved complete remission and two achieved hematological improvement with persistent thrombocytopenia. The results of this study indicate that tallimustine has promising activity in AML. Future studies may combine tallimustine with other agents known to be active against AML, and investigate its activity in other hematological malignancies. The recommended Phase II single-agent dose of tallimustine is 750-900 microgram/m2/day for 3 days, and combination studies may start at 50-66% of this dose schedule. The SCID mouse model of human leukemia may be promising in the preclinical evaluation and selection of potential antileukemic agents.