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.

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.

Plasma asparaginase activity and asparagine depletion in acute lymphoblastic leukemia patients treated with pegaspargase on Children's Oncology Group AALL07P4.

The efficacy of asparaginase in acute lymphoblastic leukemia (ALL) is dependent on depletion of asparagine, an essential amino acid for ALL cells. The target level of plasma asparaginase activity to achieve asparagine depletion has been between 0.05 and 0.4 IU/mL. COG AALL07P4 examined the asparaginase activity and plasma and CSF asparagine concentration of pegaspargase when given intravenously in the treatment of NCI high risk ALL. Matched plasma asparaginase/asparagine levels of the clearance of 54 doses of pegaspargase given in induction or consolidation demonstrated that all patients who had a plasma asparaginase level >0.02 IU/mL had undetectable plasma asparagine. No difference was observed in CSF asparagine levels associated with matched plasma asparaginase levels of 0.02-0.049 versus 0.05-0.22 IU/mL (p = .25). Our data suggest that a plasma asparaginase activity level of 0.02 IU/mL can effectively deplete plasma asparagine. The data also indicate that the 95% CI for plasma asparagine depletion after a pegaspargase dose is 22-29 days. Clinical trial registration: clinicaltrials.gov identifier NCT00671034.

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.

Pharmacokinetics of PEG-L-asparaginase and plasma and cerebrospinal fluid L-asparagine concentrations in the rhesus monkey.

The pharmacokinetics of the polyethylene glycol-conjugated form of the enzyme L-asparaginase and the depletion of L-asparagine from the plasma and cerebrospinal fluid (CSF) following an i.m. dose of 2500 IU/m2 PEG-L-asparaginase was studied in rhesus monkeys. PEG-L-asparaginase activity in plasma was detectable by 1 h after injection and maintained a plateau of approximately 4 IU/ml for more than 5 days. Subsequent elimination from plasma was monoexponential with a half-life of 6 +/- 1 days. Plasma L-asparagine concentrations fell from pretreatment levels of 14-47 microM to < 2 microM by 24 h after injection in all animals and remained undetectable for the duration of the 25-day observation period in four of six animals. In two animals, plasma L-asparagine became detectable when the PEG-L-asparaginase plasma concentration dropped below 0.1 IU/ml. Pretreatment CSF L-asparagine levels ranged from 4.7 to 13.6 microM and fell to < 0.25 microM by 48 h in five of six animals. CSF L-asparagine concentrations remained below 0.25 microM for 10-14 days in four animals. One animal had detectable CSF L-asparagine concentrations within 24 h and another had detectable concentrations within 1 week of drug administration despite a plasma PEG-L-asparaginase activity profile that did not differ from that of the other animals. These observations may be useful in the design of clinical trials with PEG-L-asparaginase in which correlations among PEG-L-asparaginase pharmacokinetics, depletion of L-asparagine, and clinical outcome should be sought.

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.

FDA drug approval summary: pegaspargase (oncaspar) for the first-line treatment of children with acute lymphoblastic leukemia (ALL).

On July 24, 2006, the U.S. Food and Drug Administration granted approval to pegaspargase (Oncaspar; Enzon Pharmaceuticals, Inc., Bridgewater, NJ; hereafter, O) for the first-line treatment of patients with acute lymphoblastic leukemia (ALL) as a component of a multiagent chemotherapy regimen. O was previously approved in February 1994 for the treatment of patients with ALL who were hypersensitive to native forms of L-asparaginase. The trial supporting this new indication was an open label, randomized, multicenter clinical trial that enrolled 118 children (age, 1-9 years) with previously untreated, standard risk ALL. Patients received either native Escherichia coli asparaginase (Elspar; Merck, Whitehouse Station, NJ; hereafter, E) or O along with multiagent chemotherapy during remission induction and delayed intensification (DI) phases of treatment. O, at a dose of 2,500 IU/m(2), was administered i.m. on day 3 of the 4-week induction phase and on day 3 of each of two 8-week DI phases. E, at a dose of 6,000 IU/m(2), was administered i.m. three times weekly for nine doses during induction and for six doses during each DI phase. This study allowed direct comparison of O and E for asparagine depletion, asparaginase activity, and development of asparaginase antibodies. An unplanned comparison of event-free survival (EFS) was conducted to rule out a deleterious O efficacy effect. Following induction and DI treatment there was complete (0.03 IU/ml in O-treated subjects was greater than the number of days in E-treated subjects during both the induction and DI phases of treatment. There was no correlation, however, between asparaginase activity and serum asparagine levels, making the former determination less clinically relevant. Using the protocol-prespecified threshold for a positive result of >2.5 times the control, 7 of 56 (12%) O subjects tested at any time during the study demonstrated antiasparaginase antibodies and 16 of 57 (28%) E subjects tested at any time during the study had antiasparaginase antibodies. In both study arms EFS was in the range of 80% at 3 years. The most serious, sometimes fatal, O toxicities were anaphylaxis, other serious allergic reactions, thrombosis (including sagittal sinus thrombosis), pancreatitis, glucose intolerance, and coagulopathy. The most common adverse events were allergic reactions (including anaphylaxis), hyperglycemia, pancreatitis, central nervous system thrombosis, coagulopathy, hyperbilirubinemia, and elevated transaminases. Disclosure of potential conflicts of interest is found at the end of this article.