Cerebrospinal fluid asparagine concentrations after Escherichia coli asparaginase in children with acute lymphoblastic leukemia

BTK inhibition sensitizes acute lymphoblastic leukemia to asparaginase by suppressing the amino acid response pathway

Asparaginase (ASNase) therapy has been a mainstay of acute lymphoblastic leukemia (ALL) protocols for decades and shows promise in the treatment of a variety of other cancers. To improve the efficacy of ASNase treatment, we used a CRISPR/Cas9-based screen to identify actionable signaling intermediates that improve the response to ASNase. Both genetic inactivation of Bruton's tyrosine kinase (BTK) and pharmacological inhibition by the BTK inhibitor ibrutinib strongly synergize with ASNase by inhibiting the amino acid response pathway, a mechanism involving c-Myc-mediated suppression of GCN2 activity. This synthetic lethal interaction was observed in 90% of patient-derived xenografts, regardless of the genomic subtype. Moreover, ibrutinib substantially improved ASNase treatment response in a murine PDX model. Hence, ibrutinib may be used to enhance the clinical efficacy of ASNase in ALL. This trial was registered at www.clinicaltrials.gov as # NCT02884453.

Pharmacodynamics of cerebrospinal fluid asparagine after asparaginase

PURPOSE

We evaluated effects of asparaginase dosage, schedule, and formulation on CSF asparagine in children with acute lymphoblastic leukemia (ALL).

METHODS

We evaluated CSF asparagine (2114 samples) and serum asparaginase (5007 samples) in 482 children with ALL treated on the Total XVI study (NCT00549848). Patients received one or two 3000 IU/m² IV pegaspargase doses during induction and were then randomized in continuation to receive 2500 IU/m² or 3500 IU/m² IV intermittently (four doses) on the low-risk (LR) or continuously (15 doses) on the standard/high risk (SHR) arms. A pharmacokinetic-pharmacodynamic model was used to estimate the duration of CSF asparagine depletion below 1 uM.

RESULTS

During induction, CSF asparagine depletion after two doses of pegaspargase was twice as long as one dose (median 30.7 vs 15.3 days, p < 0.001). During continuation, the higher dose increased the CSF asparagine depletion duration by only 9% on the LR and 1% in the SHR arm, consistent with the nonlinear pharmacokinetics of serum asparaginase. Pegaspargase caused a longer CSF asparagine depletion duration (1.3-5.3-fold) compared to those who were switched to erwinase (p < 0.001). The median (quartile range) serum asparaginase activity needed to maintain CSF asparagine below 1 µM was 0.44 (0.20, 0.99) IU/mL. Although rare, CNS relapse was higher with decreased CSF asparagine depletion (p = 0.0486); there was no association with relapse at any site (p = 0.3).

CONCLUSIONS

The number of pegaspargase doses has a stronger influence on CSF asparagine depletion than did dosage, pegaspargase depleted CSF asparagine longer than erwinase, and CSF asparagine depletion may prevent CNS relapses.

PEG-asparaginase and native Escherichia coli L-asparaginase in acute lymphoblastic leukemia in children and adolescents: a systematic review

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the cancer with the highest incidence in childhood and adolescence, and pharmacotherapy is the primary form of treatment.

OBJECTIVE AND METHODS

A systematic review of the efficacy and safety of polyethylene glycol (PEG)-asparaginase in acute lymphoblastic leukemia therapy in children and adolescents was conducted to compare it with native Escherichia coli L-asparaginase. PubMed, Web of Science, Science Direct, Cochrane Library, Scopus, LILACS (Latin American and Caribbean Health Sciences Literature) and EMBASE databases were selected. The following outcomes were analyzed: complete remission of the disease, event-free survival, overall survival, anti-asparaginase antibody level, hypersensitivity reactions, asparaginase and asparagine serum levels, number of postdiagnosis events, and overall mortality. Five randomized controlled trials were included. Analysis of the quality of evidence and risk of bias was performed using the Cochrane recommendation tool and the GRADE system.

RESULTS

The assessment results suggest that the level of certainty on the technology addressed is relatively weak from a methodological point of view. Evidence is insufficient to assess the effects on health outcomes because of the limited number and power of studies and important flaws in their design or conduct in classifying PEG-asparaginase as a superior drug or not, in the pharmacotherapy of ALL in children and adolescents. PEG-asparaginase can be used as a substitute for native E. coli L-asparaginase, demonstrating similar efficacy and safety.

CONCLUSION

The study may help decision-makers in the public health system to offer a more in-depth judgment on the therapeutic alternatives used to treat this neoplasm in children and adolescents.

Asparagine levels in the cerebrospinal fluid of children with acute lymphoblastic leukemia treated with pegylated-asparaginase in the induction phase of the AIEOP-BFM ALL 2009 study

Asparagine levels in cerebrospinal fluid and serum asparaginase activity were monitored in children with acute lymphoblastic leukemia treated with pegylated-asparaginase. The drug was given intravenously at a dose of 2,500 IU/m² on days 12 and 26. Serum and cerebrospinal fluid samples obtained on days 33 and 45 were analyzed centrally. Since physiological levels of asparagine in the cerebrospinal fluid of children and adolescents are 4-10 μmol/L, in this study asparagine depletion was considered complete when the concentration of asparagine was ≤0.2 μmol/L, i.e. below the lower limit of quantification of the assay used. Over 24 months 736 patients (AIEOP n=245, BFM n=491) and 903 cerebrospinal fluid samples (n=686 on day 33 and n=217 on day 45) were available for analysis. Data were analyzed separately for the AIEOP and BFM cohorts and yielded superimposable results. Independently of serum asparaginase activity levels, cerebrospinal fluid asparagine levels were significantly reduced during the investigated study phase but only 28% of analyzed samples showed complete asparagine depletion while relevant levels, ≥1 μmol/L, were still detectable in around 23% of them. Complete cerebrospinal fluid asparagine depletion was found in around 5-6% and 33-37% of samples at serum asparaginase activity levels <100 and ≥ 1,500 IU/L, respectively. In this study cerebrospinal fluid asparagine levels were reduced during pegylated-asparaginase treatment, but complete depletion was only observed in a minority of patients. No clear threshold of serum pegylated-asparaginase activity level resulting in complete cerebrospinal fluid asparagine depletion was identified. The consistency of the results found in the two independent data sets strengthen the observations of this study. Details of the treatment are available in the European Clinical Trials Database at https://www.clin-icaltrialsregister.eu/ctr-search/trial/2007-004270-43/IT.

Asparaginase in the treatment of non-ALL hematologic malignancies

Asparaginases are among the most effective agents against acute lymphoblastic leukemia (ALL) and are Food and Drug Administration-approved for the treatment of pediatric and adult ALL. However, the efficacy of these drugs for the treatment of other hematologic malignancies particularly acute myeloid leukemia is not well established. The mechanism of action of asparaginases has thought to be related to a swift and sustained reduction in serum L-asparagine, which is required for rapid proliferation of metabolically demanding leukemic cells. However, asparagine depletion alone appears not to be sufficient for effective cytotoxic activity of asparaginase against leukemia cells, because glutamine can rescue asparagine-deprived cells by regeneration of asparagine via a transamidation chemical reaction. For this reason, glutamine reduction is also necessary for full anti-leukemic activity of asparaginase. Indeed, both Escherichia coli and Erwinia chrysanthemi asparaginases possess glutaminase enzymatic activity, and their administrations have shown to reduce serum glutamine level by deamidating glutamine to glutamate and ammonia. Emerging data have provided evidence that several types of neoplastic cells require glutamine for the synthesis of proteins, nucleic acids, and lipids. This fundamental role of glutamine and its metabolic pathways for growth and proliferation of individual malignant cells may identify a special group of patients whose solid or hematologic neoplasms may benefit significantly from interruption of glutamine metabolism. To this end, asparaginase products deserve a second look particularly in non-ALL malignant blood disorders. Here, we review mechanisms of anti-tumor activity of asparaginase focusing on importance of glutamine reduction, pharmacology of asparaginase products, in vitro activities as well as clinical experience of incorporating asparaginase in therapeutic regimens for non-ALL hematologic malignancies.

Erwinia asparaginase achieves therapeutic activity after pegaspargase allergy: a report from the Children's Oncology Group

AALL07P2 evaluated whether substitution of Erwinia asparaginase 25000 IU/m(2) for 6 doses given intramuscularly Monday/Wednesday/Friday (M/W/F) to children and young adults with acute lymphoblastic leukemia and clinical allergy to pegaspargase would provide a 48-hour nadir serum asparaginase activity (NSAA) ≥ 0.10 IU/mL. AALL07P2 enrolled 55 eligible/evaluable patients. NSAA ≥ 0.1 IU/mL was achieved in 38 of 41 patients (92.7%) with acceptable samples 48 hours and in 38 of 43 patients (88.4%) 72 hours after dosing during course 1. Among samples obtained during all courses, 95.8% (252 of 263) of 48-hour samples and 84.5% (125 of 148) of 72-hour samples had NSAA ≥ 0.10-IU/mL. Pharmacokinetic parameters were estimated by fitting the serum asparaginase activity-time course for all 6 doses given during course 1 to a 1-compartment open model with first order absorption. Erwinia asparaginase administered with this schedule achieved therapeutic NSAA at both 48 and 72 hours and was well tolerated with no reports of hemorrhage, thrombosis, or death, and few cases of grade 2 to 3 allergic reaction (n = 6), grade 1 to 3 hyperglycemia (n = 6), or grade 1 pancreatitis (n = 1). Following allergy to pegaspargase, Erwinia asparaginase 25000 IU/m(2) × 6 intramuscularly M/W/F can be substituted for a single dose of pegaspargase.

Dexamethasone exposure and asparaginase antibodies affect relapse risk in acute lymphoblastic leukemia

We have previously hypothesized that higher systemic exposure to asparaginase may cause increased exposure to dexamethasone, both critical chemotherapeutic agents for acute lymphoblastic leukemia. Whether interpatient pharmaco-kinetic differences in dexamethasone contribute to relapse risk has never been studied. The impact of plasma clearance of dexamethasone and anti-asparaginase antibody levels on risk of relapse was assessed in 410 children who were treated on a front-line clinical trial for acute lymphoblastic leukemia and were evaluable for all pharmacologic measures, using multivariate analyses, adjusting for standard clinical and biologic prognostic factors. Dexamethasone clearance (mean ± SD) was higher (P = 3 × 10(-8)) in patients whose sera was positive (17.7 ± 18.6 L/h per m(2)) versus nega-tive (10.6 ± 5.99 L/h per m(2)) for anti-asparaginase antibodies. In multivariate analyses, higher dexamethasone clearance was associated with a higher risk of any relapse (P = .01) and of central nervous system relapse (P = .014). Central nervous system relapse was also more common in patients with anti-asparaginase antibodies (P = .019). In conclusion, systemic clearance of dexamethasone is higher in patients with anti-asparaginase antibodies. Lower exposure to both drugs was associated with an increased risk of relapse.

Isolated extramedullary relapse in childhood acute lymphocytic leukemia

Although the vast majority of children with acute lymphocytic leukemia attain remission with modern therapies, an unacceptably high number will suffer a disease relapse. Both the duration of remission and the site of relapse are important prognostic factors. This review focuses on leukemic relapse isolated to sites outside the bone marrow (extramedullary sites). Data from cooperative study groups as well as large single institutions are reviewed with respect to the incidence of isolated extramedullary relapse as well as the outcome following relapse. The unique anatomic and physiologic properties of the testes and the central nervous system-the two most common sites of isolated extramedullary relapse-are discussed. Finally, the evolution of leukemia therapy is reviewed, bringing into focus the goals and challenges of future therapeutic endeavors.

Prognostic significance of the initial cerebro-spinal fluid (CSF) involvement of children with acute lymphoblastic leukaemia (ALL) treated without cranial irradiation: results of European Organization for Research and Treatment of Cancer (EORTC) Children Leukemia Group study 58881

AIM OF THE STUDY

To evaluate the prognostic significance of the initial cerebro-spinal fluid (CSF) involvement of children with ALL enrolled from 1989 to 1996 in the EORTC 58881 trial.

PATIENTS AND METHODS

Patients (2025) were categorised according to initial central nervous system (CNS) status: CNS-1 (CNS negative, n=1866), CNS-2 (<5 leucocytes/mm(3), CSF with blasts, n=50), CNS-3 (CNS positive, n=49), TLP+ (TLP with blasts, n=60). CNS-directed therapy consisted in intravenous (i.v.) methotrexate (5 g/sqm) in 4-10 courses, and intrathecal methotrexate injections (10-20), according to CNS status. Cranial irradiation was omitted in all patients.

RESULTS

In the CNS1, TLP+, CNS2 and CNS3 group the 8-year EFS rate (SE%) was 69.7% (1.1%), 68.8% (6.2%), 71.3% (6.5%) and 68.3% (6.2%), respectively. The 8-year incidence of isolated CNS relapse (SE%) was 3.4% (0.4%), 1.7% (1.7%), 6.1% (3.5%) and 9.4% (4.5%), respectively, whereas the 8-year isolated or combined CNS relapse incidence was 7.6% (0.6%), 3.5% (2.4%), 10.2% (4.4%) and 11.7% (5.0%), respectively. Patients with CSF blasts had a higher rate of initial bad risk features. Multivariate analysis indicated that presence of blasts in the CSF had no prognostic value: (i) for EFS and OS; (ii) for isolated and isolated or combined CNS relapse; WBC count<25 × 10(9)/L and Medac E-coli asparaginase treatment were each related to a lower CNS relapse risk.

CONCLUSIONS

The presence of initial CNS involvement has no prognostic significance in EORTC 58881. Intensification of CNS-directed chemotherapy, without CNS radiation, is an effective treatment of initial meningeal leukaemic involvement.

Comparison of native E. coli and PEG asparaginase pharmacokinetics and pharmacodynamics in pediatric acute lymphoblastic leukemia

Asparaginase (ASP) is used routinely in frontline clinical trials for the treatment of childhood acute lymphoblastic leukemia (ALL). The goals of this study were to assess the pharmacokinetics and pharmacodynamics of ASP and to mathematically model the dynamics between ASP and asparagine (ASN) in relapsed ALL. Forty children were randomized to receive either native or polyethylene glycolated (PEG) Escherichia coli ASP during reinduction therapy. Serial plasma ASP and ASN, cerebrospinal fluid (CSF) ASN, and serum anti-ASP antibody samples were collected. The ASP clearance was higher (P = 0.001) for native vs. PEG ASP. Patients with antibodies to PEG ASP had faster PEG ASP clearance (P = 0.004) than did antibody-negative patients. Patients who were positive for antibodies had higher CSF ASN concentrations than did those who were negative (P = 0.04). The modeling suggests that by modifying dosages, comparable ASN depletion is achievable with both preparations. At relapse, there were significant pharmacokinetic and pharmacodynamic differences attributable to ASP preparation and antibody status.

Pegasparaginase: where do we stand?

The use of unmodified asparaginases (ASP) in the management of pediatric and adult acute lymphoblastic leukemia (ALL) is well established. Despite its well-proven clinical efficacy, the use of unmodified Escherichia coli ASP (EC-ASP) has been limited by frequent toxicities, especially the development of hypersensitivity reactions and neutralizing antibodies, and by the need for frequent administration. To overcome these limitations, EC-ASP enzyme was covalently linked to monomethoxypolyethylene glycol (PEG), forming the pegylated ASP (PEG-ASP) (Oncaspar). PEG-ASP has a prolonged half-life and is associated with decreased immunogenicity when compared with EC-ASP. Clinical trials have demonstrated the efficacy, safety and tolerability of PEG-ASP administered intramuscularly, subcutaneously or intravenously as part of multi-agent chemotherapy regimens in the management of newly diagnosed and relapsed pediatric and adult ALL. Here we discuss the pharmacology, pharmacokinetics, clinical trial results and potential side effects of PEG-ASP.

Pharmacological and clinical evaluation of L-asparaginase in the treatment of leukemia

L-Asparaginase is an effective antineoplastic agent, used in the acute lymphoblastic leukemia chemotherapy. It has been an integral part of combination chemotherapy protocols of pediatric acute lymphoblastic leukemia for almost 3 decades. The potential of L-asparaginase as a drug of leukemia has been a matter of discussion due to the high rate of allergic reactions exhibited by the patients receiving the medication of this enzyme drug. Frequent need of intramuscular injection has been another disadvantage associated with the native preparation. However, of late these clinical complications seem to have been addressed by modified versions of L-asparaginase. PEG-L-asparaginase proves to be most effective in this regard. It becomes important to discuss the efficacy of L-asparaginase as an antileukemic drug vis-a-vis these disadvantages. In this review, an attempt has been made to critically evaluate the pharmacological and clinical potential of various preparations of L-asparaginase as a drug. Advantages of PEG-L-asparaginase over native preparations and historical developments of therapy with l-asparaginase have also been outlined in the review below.

Results of the Dana-Farber Cancer Institute ALL Consortium Protocol 95-01 for children with acute lymphoblastic leukemia

The Dana-Farber Cancer Institute (DFCI) Childhood ALL Consortium Protocol 95-01 was designed to minimize therapy-related morbidity for children with newly diagnosed ALL without compromising efficacy. Patients participated in randomized comparisons of (1) doxorubicin given with or without dexrazoxane, a cardioprotectant (high-risk patients), (2) intensive intrathecal chemotherapy and cranial radiation (standard-risk patients), and (3) Erwinia and Escherichia coli asparaginase (all patients). Between 1996 and 2000, 491 patients (aged 0-18 years) were enrolled (272 standard risk and 219 high risk). With a median of 5.7 years of follow-up, the estimated 5-year event-free survival (EFS) for all patients was 82%+/-2%. Dexrazoxane did not have a significant impact on the 5-year EFS of high-risk patients (P=.99), and there was no significant difference in outcome of standard-risk patients based on type of central nervous system (CNS) treatment (P=.26). Compared with E coli asparaginase, Erwinia asparaginase was associated with a lower incidence of toxicity (10% versus 24%), but also an inferior 5-year EFS (78%+/-4% versus 89%+/-3%, P=.01). We conclude that (1) dexrazoxane does not interfere with the antileukemic effect of doxorubicin, (2) intensive intrathecal chemotherapy is as effective as cranial radiation in preventing CNS relapse in standard-risk patients, and (3) once-weekly Erwinia is less toxic than E coli asparaginase, but also less efficacious.

Asparagine depletion after pegylated E. coli asparaginase treatment and induction outcome in children with acute lymphoblastic leukemia in first bone marrow relapse: a Children's Oncology Group study (CCG-1941)

PURPOSE

Re-induction outcomes vary for children with acute lymphoblastic leukemia (ALL) and marrow relapse. We explored possible relationships among asparaginase (ASNase) activity levels, asparagine (ASN) depletion, anti-ASNase antibody titers, and response to re-induction therapy in children and adolescents with ALL and an 'early' first marrow relapse.

PATIENTS AND METHODS

After appropriate informed consent, we enrolled children and adolescents 1-21 years old with ALL and first marrow relapse within 12 months of completion of primary therapy. Induction therapy included intramuscular pegylated ASNase on Days 2 and 16. We assessed ASNase activity, anti-ASNase antibody titers against native and pegylated (E. coli) ASNase, and amino acid levels of asparagine (ASN) and glutamine (GLN) on Days 0, 14, and 35 of re-induction.

RESULTS

Ninety-three patients were at least partially assessable. Among 21 patients with M1 marrow status at Day 35, the median Day 14 ASN level was <1 microM. This is significantly lower than the median Day 14 ASN level of 4 microM in the group of patients with M3 marrow at Day 35. Neither Day 0 nor Day 35 antibody titers predicted ASNase enzymatic activity level on Day 14. Surprisingly, Day 14 ASNase activity did not predict serum ASN level on Day 14. However, Day 0 and Day 35 anti-native ASNase antibody titers, and Day 0 anti-PEG ASNase antibody titers correlated positively with Day 14 serum ASN levels as one might expect from neutralizing antibody. Day 35 anti-PEG ASNase antibody titers did not.

CONCLUSIONS

Patients with greater ASN depletion were more likely to achieve second remission in the context of six-drug therapy.

Serum asparaginase activities and asparagine concentrations in the cerebrospinal fluid after a single infusion of 2,500 IU/m(2) PEG asparaginase in children with ALL treated according to protocol COALL-06-97

BACKGROUND AND PROCEDURE

Pharmacological surrogate parameters are considered a useful tool in estimating the treatment intensity of asparaginase (ASNase) preparations. When a pegylated ASNase (single infusion of 2,500 IU/m(2) polyethylene glycol (PEG)-ASNase, Oncaspar) was introduced into the treatment protocols of the German Cooperative Acute Lymphoblastic Leukaemia (COALL) study group, this was accompanied by a drug monitoring programme measuring serum ASNase activity and asparagine (ASN) concentrations in the cerebrospinal fluid (CSF) in 70 children.

RESULTS

Four hundred fifty-nine serum samples from 67 evaluable patients showed medians of ASNase activity of 1,189.5, 824.5, 310.5, 41 and 4 U/l on day 7 +/- 1, 14 +/- 1, 21 +/- 1, 28 +/- 1 and 35 +/- 1 respectively. One hundred eighty-four samples from 59 patients were evaluable for ASN concentrations in the CSF. The medians of ASN concentration were <0.2, 0.2, 0.9 and 3.2 microM on day 14 +/- 1, 21 +/- 1, 28 +/- 1 and 35 +/- 1 respectively. When relating CSF ASN levels to the serum ASNase activity measured on the same day, a median of 1.2 microM CSF ASN was associated with values of serum ASNase activity between > or =2.5 and <100 U/l. Serum ASNase activity values > or =100 U/l were associated with a median CSF ASN of <0.2 microM, with 13/27 samples being incompletely depleted.

CONCLUSIONS

The treatment intensity achieved with PEG ASNase in the present study appears to be acceptable based on the surrogate of serum ASNase activity. However, the pharmacological objective of ASNase treatment, that is, complete CSF ASN depletion with an ASNase activity >100 U/l, was not ensured. Nevertheless, one must also be aware that the minimum ASN concentration required for leukaemic cell growth is yet to be established.

Asparaginase Pharmacokinetics After Intensive Polyethylene Glycol-Conjugated L-Asparaginase Therapy for Children with Relapsed Acute Lymphoblastic Leukemia

PURPOSE

Asparaginase therapy is an important component in the treatment of children with acute lymphoblastic leukemia. Polyethylene glycol-conjugated asparaginase (PEG-ASNase) has significant pharmacological advantages over native Escherichia coli asparaginase. We investigated the pharmacokinetics of PEG-ASNase, presence of antibodies to PEG-ASNase, and concentrations of asparagine in serum and cerebrospinal fluid (CSF) in combination chemotherapy for relapsed pediatric acute lymphoblastic leukemia.

EXPERIMENTAL DESIGN

Twenty-eight pediatric patients with relapsed medullary (n = 16) and extramedullary (n = 11) acute lymphoblastic leukemia were enrolled at three pediatric institutions and had at least two serum and CSF samples obtained for analysis. Patients received induction therapy (including PEG-ASNase 2500 IU/m2 intramuscularly weekly on days 2, 9, 16, and 23) and intensification therapy (including PEG-ASNase 2500 IU/m2 intramuscularly once on day 7). Serum samples were obtained weekly during induction and intensification. CSF samples were obtained during therapeutic lumbar punctures during induction and intensification.

RESULTS

Weekly PEG-ASNase therapy resulted in PEG-ASNase activity of >0.1 IU/ml in 91-100% of patients throughout induction. During intensification, PEG-ASNase on day 7 resulted in PEG-ASNase activity >0.1 IU/ml in 94% and 80% of patients on days 14 and 21, respectively. Serum and CSF asparagine depletion was observed and maintained during induction and intensification in the majority of samples. PEG-ASNase antibody was observed in only 3 patients.

CONCLUSIONS

Intensive PEG-ASNase therapy in the treatment of relapsed acute lymphoblastic leukemia reliably results in high-level serum PEG-ASNase activity, and asparagine depletion in serum and CSF is usually achieved. Incorporation of intensive PEG-ASNase in future trials for recurrent acute lymphoblastic leukemia is warranted.

Role of pharmacogenomics and pharmacodynamics in the treatment of acute lymphoblastic leukaemia

Pharmacodynamic studies have been used to establish the relationships between the administered dosage and the concentration of drugs and metabolites in the blood or tissues and that between these concentrations and pharmacological effects. Polymorphisms in the genes that encode drug-metabolizing enzymes, drug transporters and drug targets can affect a person's response to therapy and may affect the development of de novo or therapy-related leukaemias. The burgeoning field of pharmacogenomics elucidates inherited differences in drug metabolism and treatment response. Increasingly, pharmacodynamic and pharmacogenomic studies are being used to individualize therapy to enhance efficacy and reduce toxicity.

Drug monitoring of PEG-asparaginase treatment in childhood acute lymphoblastic leukemia and non-Hodgkin's lymphoma

This is an updated review of the pharmacokinetic profile of PEG-asparaginase (PEG-ASNase) in childhood acute lymphoblastic leukemia (ALL) or non-Hodgkin's lymphoma (NHL). In a total of 271 children undergoing ALL/NHL or relapsed ALL treatment according to the Berlin-Frankfurt-Münster (BFM) protocols, drug monitoring of ASNase serum activity was performed after PEG-ASNase infusions. From December 1996 to July 2000, 1667 samples after 362 intravenous administrations of either 500, 750, 1000 or 2500 IU/m2 PEG-ASNase were analyzed. Three weeks after infusion when relating the ASNase activity to the four-dose levels significant differences were not observed. Large interpatient variability was seen at each dose level resulting in a relevant number of patients not achieving adequate treatment intensity. Neither the extent of ASNase pre-treatment nor a prior event of a hypersensitivity reaction against unmodified ASNase had any impact on PEG-ASNase pharmacokinetics. It is concluded that escalation of the dose of PEG-ASNase did not result in a significant prolongation of time with activity values considered therapeutic. Depending on the desired endpoint, a second administration of PEG-ASNase seems to be more favorable than increasing the dose. For a safer recommendation, further investigations assessing the pharmacodynamic profile are required. Drug monitoring is advisable for early detection of patients with rapid elimination in order to ensure maximum treatment intensity.

Remission induction therapy for childhood acute lymphoblastic leukaemia: clinical and cellular pharmacology of vincristine, corticosteroids, L-asparaginase and anthracyclines

Remission induction therapy with vincristine, a corticosteroid, L-asparaginase and an anthracycline has been the mainstay of the initial phase of treatment for childhood acute lymphoblastic leukaemia (ALL) for the past 25 years. The speed and depth of the early response to remission induction therapy has become an important determinant of the intensity of subsequent therapy in many protocols worldwide. Moreover, the detection of significant levels of minimal residual disease at the end of remission induction may have an important bearing on subsequent outcome. Although these clinical observations may reflect, in part, the inherent sensitivity of lymphoblasts to remission induction therapy, the pharmacology of these agents in relation to childhood ALL may also play an important part in early response to therapy. In-vitro studies of human leukaemia cell lines indicate that both the extracellular fluid concentration and duration of exposure to vincristine and anthracyclines are important determinants of cytotoxicity. For L-asparaginase and corticosteroids, the cellular and molecular pharmacological determinants of chemosensitivity have been partially characterized, but further work is needed in this area. The clinical pharmacology of vincristine and L-asparaginase have been well characterized in relation to childhood ALL, and considerable interpatient pharmacokinetic variability exists for these drugs. For corticosteroids and anthracyclines, pharmacology studies are needed in order to fully characterize and understand the factors influencing interpatient pharmacokinetic variability for these agents in relation to childhood ALL. Whereas the relationship between the clinical pharmacology, and potentially important pharmacodynamic effects such as asparagine depletion, has been well characterized for therapy with L-asparaginase, similar studies have yet to be performed for the other drugs that form the mainstay of remission induction therapy for childhood ALL. Therefore, further studies are required to investigate the relative importance of the clinical and cellular pharmacology of vincristine, corticosteroids, L-asparaginase and anthracyclines in the speed and depth of response to remission induction therapy for childhood ALL. Where these have been studied, interindividual differences in the clinical and cellular pharmacology of anticancer agents have been shown to be important determinants of the long-term disease-free survival for children with ALL.

L-asparagine depletion and L-asparaginase activity in children with acute lymphoblastic leukemia receiving i.m. or i.v. Erwinia C. or E. coli L-asparaginase as first exposure

PURPOSE

The present study was aimed at investigating L-asparaginase (L-ASE) activity (in plasma) and L-asparagine (L-ASN) depletion (in plasma and CSF) in children with newly diagnosed acute lymphoblastic leukemia (ALL) exposed for the first time to different L-ASE products.

PATIENTS AND METHODS

During the induction treatment of the AIEOP ALL 95 study, 62 patients were treated with either Erwinase (n = 15), or E. coli medac (n = 47) L-ASE products, given either i.m. or i.v., at the standard dosage of 10,000 IU/m2, q 3 days x 8 (first exposure).

RESULTS

Plasma and CSF L-ASN trough levels were undetectable in all cases, including those with L-ASE trough activity < 50 mU/ml. L-ASE trough activity during the administration of medac was however significantly higher when compared with that of Erwinase.

CONCLUSIONS

L-ASN depletion after a first exposure to standard doses of Erwinase or medac is obtained in virtually all patients. No differences are seen between the I.M. or I.V. administration routes but the medac product is associated with a significantly higher enzyme activity in respect of Erwinase. L-ASN levels may be undetectable also in patients with L-ASE trough activity levels < 50 mU/ml, challenging the current opinion that an activity level of 100 mU/ml is needed to obtain L-ASN depletion.

Acute lymphoblastic leukemia in children

As the overall long-term event-free survival rate in children with acute lymphoblastic leukemia approaches 80%, emphasis is being placed on risk-directed therapy so that patients are neither overtreated nor undertreated. It has become apparent that a risk assignment system based on primary genetic abnormalities is inadequate by itself. For example, leukemias with the MLL-AF4 or BCR-ABL fusion gene are, in fact, heterogeneous diseases. Many require allogeneic hematopoietic stem-cell transplantation; some, if the patient is of favorable age and has a low presenting leukocyte count, can be cured with chemotherapy alone. Measurement of early responses to therapy and extent of minimal residual disease can greatly improve the accuracy of risk assessment. Consideration of the variable effects of therapy on the prognostic significance of specific genetic abnormalities is also important. Therefore, TEL-AML1 fusion confers a favorable prognosis in some protocols of chemotherapy but not in others. Studies to identify genetic polymorphisms with pharmacokinetic and pharmacodynamic significance promise to guide further refinement of treatment strategies. This will allow maximization of anticancer effects without induction of unacceptable toxicity in individual patients.