Allergic reactions to E. coli L-asparaginase do not affect outcome in childhood B-precursor acute lymphoblastic leukemia: a Children's Oncology Group Study

Asparaginase-specific basophil recognition and activation predict Asparaginase hypersensitivity in mice

Background

Asparaginase (ASNase) is a crucial part of acute leukemia treatment, but immune responses to the agent can reduce its effectiveness and increase the risk of relapse. Currently, no reliable and validated biomarker predicts ASNase-induced hypersensitivity reactions during therapy. We aimed to identify predictive biomarkers and determine immune cells responsible for anaphylaxis using a murine model of ASNase hypersensitivity.

Methods

Our preclinical study uses a murine model to investigate predictive biomarkers of ASNase anaphylaxis, including anti-ASNase antibody responses, immune complex (IC) levels, ASNase-specific binding to leukocytes or basophils, and basophil activation.

Results

Our results indicate that mice immunized to ASNase exhibited dynamic IgM, IgG, and IgE antibody responses. The severity of ASNase-induced anaphylaxis was found to be correlated with levels of IgG and IgE, but not IgM. Basophils from immunized mice were able to recognize and activate in response to ASNase ex vivo, and the extent of recognition and activation also correlated with the severity of anaphylaxis observed. Using a multivariable model that included all biomarkers significantly associated with anaphylaxis, independent predictors of ASNase-induced hypersensitivity reactions were found to be ASNase IC levels and ASNase-specific binding to leukocytes or basophils. Consistent with our multivariable analysis, we found that basophil depletion significantly protected mice from ASNase-induced hypersensitivity reactions, supporting that basophils are essential and can be used as a predictive marker of ASNase-induced anaphylaxis.

Conclusions

Our study demonstrates the need for using tools that can detect both IC- and IgE-mediated hypersensitivity reactions to mitigate the risk of ASNase-induced hypersensitivity reactions during treatment.

Pharmacogenetics of pediatric acute lymphoblastic leukemia in Uruguay: adverse events related to induction phase drugs

In Uruguay, the pediatric acute lymphoblastic leukemia (ALL) cure rate is 82.2%, similar to those reported in developed countries. However, many patients suffer adverse effects that could be attributed, in part, to genetic variability. This study aims to identify genetic variants related to drugs administered during the induction phase and analyze their contribution to adverse effects, considering individual genetic ancestry. Ten polymorphisms in five genes (ABCB1, CYP3A5, CEP72, ASNS, and GRIA1) related to prednisone, vincristine, and L-asparaginase were genotyped in 200 patients. Ancestry was determined using 45 ancestry informative markers (AIMs). The sample ancestry was 69.2% European, 20.1% Native American, and 10.7% African, but with high heterogeneity. Mucositis, Cushing syndrome, and neurotoxicity were the only adverse effects linked with genetic variants and ancestry. Mucositis was significantly associated with ASNS (rs3832526; 3R/3R vs. 2R carriers; OR: = 6.88 [1.88-25.14], p = 0.004) and CYP3A5 (non-expressors vs. expressors; OR: 4.55 [1.01-20.15], p = 0.049) genes. Regarding Cushing syndrome, patients with the TA genotype (rs1049674, ASNS) had a higher risk of developing Cushing syndrome than those with the TT genotype (OR: 2.60 [1.23-5.51], p = 0.012). Neurotoxicity was significantly associated with ABCB1 (rs9282564; TC vs. TT; OR: 4.25 [1.47-12.29], p = 0.007). Moreover, patients with <20% Native American ancestry had a lower risk of developing neurotoxicity than those with ≥20% (OR: 0.312 [0.120-0.812], p = 0.017). This study shows the importance of knowing individual genetics to improve the efficacy and safety of acute lymphoblastic leukemia.

Experience with Generic Pegylated L-asparaginase in Children with Acute Lymphoblastic Leukemia from a Tertiary Care Oncology Center in South India

Dhaarani JayaramanBackground  Acute lymphoblastic leukemia (ALL) is a common type of leukemia in children. The innovator pegylated L-asparaginase has several advantages over native L-asparaginase; however, its use in India is limited due to availability and cost. Therefore, a generic pegylated L-asparaginase can be considered as an alternative to the innovator molecule. Methods  A retrospective study was conducted to assess the outcome (minimal residual disease [MRD]) and toxicity of a generic pegylated L-asparaginase (Hamsyl) at the end of induction therapy. Results  Eighty-eight (80.7%) and 21 (19.3%) patients had received generic pegylated L-asparaginase and conventional asparaginase, respectively, as a part of their treatment protocol. Nearly 82% of patients had B-type ALL. Eight-one percent of children had a white blood cell count of fewer than 50,000/mm 3 . At the end of induction, 80.7% (88) of children were minimal residual disease (MRD)-negative, and at the end of augmented consolidation therapy, 20.2% were MRD-negative. Ten percent of patients exhibited allergic reactions. Two children had pancreatitis, and one child had central venous thrombosis. Conclusion  The generic pegylated L-asparaginase (Hamsyl) was effective and safe for use in pediatric ALL.

L-Asparaginase as the gold standard in the treatment of acute lymphoblastic leukemia: a comprehensive review

L-Asparaginase is an antileukemic drug long approved for clinical use to treat childhood acute lymphoblastic leukemia, the most common cancer in this population worldwide. However, the efficacy and its use as a drug have been subject to debate due to the variety of adverse effects that patients treated with it present, as well as the prompt elimination in plasma, the need for multiple administrations, and high rates of allergic reactions. For this reason, the search for new, less immunogenic variants has long been the subject of study. This review presents the main aspects of the L-asparaginase enzyme from a structural, pharmacological, and clinical point of view, from the perspective of its use in chemotherapy protocols in conjunction with other drugs in the different treatment phases.

Asparaginase activity monitoring and management of asparaginase hypersensitivity reactions in Canada

INTRODUCTION

Pegaspargase can cause anti-asparaginase antibody formation, which can decrease its effectiveness without causing any clinically apparent reaction (silent inactivation). When a patient has silent inactivation, a switch to Erwinia anti-asparaginase is warranted, but there is currently a global shortage of Erwinia. The only way to identify silent inactivation is to measure an asparaginase level. However, routine asparaginase level monitoring is not currently standard of care at all Canadian centers. This study aims to identify variations in practice regarding asparaginase level monitoring and Erwinia use.

METHODS

A 21-item survey was developed using OPINIO software and distributed to all Pediatric Hematology-Oncologists in Canada from February to October 2020.

RESULTS

Respondents represented 15 hospitals across each region of Canada (response rate = 52%). Only 39.2% of respondents reported routinely measuring asparaginase levels, yet 53% of respondents have modified therapy from pegaspargase to Erwinia in up to half of their patients. The most common reason for not measuring asparaginase levels was not knowing how to use levels clinically (25.5%). There was variation in the timing of levels and their target.

CONCLUSIONS

We identified substantial variation in asparaginase activity monitoring practices across Canada. Therefore, future research should aim to develop a national practice guideline on asparaginase activity monitoring.

Current Use of Asparaginase in Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

Pediatric Acute Lymphoblastic Leukemia (ALL) cure rates have improved exponentially over the past five decades with now over 90% of children achieving long-term survival. A direct contributor to this remarkable feat is the development and expanded understanding of combination chemotherapy. Asparaginase is the most recent addition to the ALL chemotherapy backbone and has now become a hallmark of therapy. It is generally accepted that the therapeutic effects of asparaginase is due to depletion of the essential amino acid asparagine, thus occupying a unique space within the therapeutic landscape of ALL. Pharmacokinetic and pharmacodynamic profiling have allowed a detailed and accessible insight into the biochemical effects of asparaginase resulting in regular clinical use of therapeutic drug monitoring (TDM). Asparaginase's derivation from bacteria, and in some cases conjugation with a polyethylene glycol (PEG) moiety, have contributed to a unique toxicity profile with hypersensitivity reactions being the most salient. Hypersensitivity, along with several other toxicities, has limited the use of asparaginase in some populations of ALL patients. Both TDM and toxicities have contributed to the variety of approaches to the incorporation of asparaginase into the treatment of ALL. Regardless of the approach to asparagine depletion, it has continually demonstrated to be among the most important components of ALL therapy. Despite regular use over the past 50 years, and its incorporation into the standard of care treatment for ALL, there remains much yet to be discovered and ample room for improvement within the utilization of asparaginase therapy.

L-asparaginase mediated therapy in L-asparagine auxotrophic cancers: A review

Microbial L-asparaginase is the most effective first-line therapeutic used in the treatment protocols of paediatric and adult leukemia. Leukemic cell's auxotrophy for L-asparagine is exploited as a therapeutic strategy to mediate cell death through metabolic blockade of L-asparagine using L-asparaginase. Escherichia coli and Erwinia chrysanthemi serve as the major enzyme deriving sources accepted in clinical practise and the enzyme has bestowed improvements in patient outcomes over the last 40 years. However, an array of side effects generated by the native enzymes due to glutamine co-catalysis and short serum stays augmenting frequent dosages, intended a therapeutic switch towards the development of biobetter alternatives for the enzyme including the formulations resulting in sustained local depletion of L-asparagine. In addition, the treatment with L-asparaginase in few cancer types has proven to elicit drug-induced cytoprotective autophagy mechanisms and therefore warrants concern. Although the off-target glutamine hydrolysis has been viewed in contributing the drug-induced secondary responses in cells deficient with asparagine synthetase machinery, the beneficial role of glutaminase-asparaginase in proliferative regulation of asparagine prototrophic cells has been looked forward. The current review provides an overview on the enzyme's clinical applications in leukemia and possible therapeutic implications in other solid tumours, recent advancements in drug formulations, and discusses the aspects of two-sided roles of glutaminase-asparaginases and drug-induced cytoprotective autophagy mechanisms.

Can recombinant technology address asparaginase Erwinia chrysanthemi shortages?

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Bacterial L-asparaginase has played an important role in ALL treatment for several decades; however, hypersensitivity reactions to Escherichia coli-derived asparaginases often preclude their use. Inability to receive asparaginase due to hypersensitivities is associated with poor patient outcomes. Erwinia chrysanthemi-derived asparaginase (ERW) is an effective, non-cross-reactive treatment option, but is limited in supply. Consequently, alternative asparaginase preparations are needed to ensure asparaginase availability for patients with hypersensitivities. Recombinant technology can potentially address this unmet need by programming cells to produce recombinant asparaginase. JZP-458, a recombinant Erwinia asparaginase derived from a novel Pseudomonas fluorescens expression platform with no immunologic cross-reactivity to E. coli-derived asparaginases, has the same primary amino acid sequence as ERW, with comparable activity based on in vitro measurements. The efficient manufacturing of JZP-458 would provide an additional asparaginase preparation for patients with hypersensitivities.

Asparaginase Toxicities: Identification and Management in Patients With Acute Lymphoblastic Leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is a common cancer in children, and outcomes have greatly improved because of the refinement of multiagent chemotherapy regimens that include intensified asparaginase therapy. Asparaginase, a cornerstone of modern pediatric chemotherapy regimens for ALL and asparaginase-containing protocols, is increasingly used in adolescent and adult patients historically treated with asparaginase-free regimens. 
.

OBJECTIVES

This article is an overview of commonly encountered asparaginase-
associated toxicities and offers recommendations for treatment management.
.

METHODS

A literature review was conducted, reviewing asparaginase and common toxicities, specifically hypersensitivity, pancreatitis, thrombosis, hyperbilirubinemia, and hyperglycemia.
.

FINDINGS

The rapid identification and management of common asparaginase-associated adverse events can reduce symptom severity and limit potential interruptions to therapy, possibly improving outcomes.

Use of PEG-asparaginase in newly diagnosed adults with standard-risk acute lymphoblastic leukemia compared with E. coli-asparaginase: a retrospective single-center study

Acute lymphoblastic leukemia (ALL) is a heterogeneous disease, and the long-term survival varies with different ages. We performed a retrospective analysis of 122 newly diagnosed adults with standard-risk ALL treated with Escherichia coli asparaginase (E. coli-asparaginase, n = 50) and polyethylene glycol-conjugated asparaginase (PEG-asparaginase, n = 72). No treatment-related mortality (TRM) occurred in the E. coli-asparaginase group, and 3 TRM events occurred in the PEG-asparaginase group without relation to asparaginase. In addition, 22 (44.0%) and 48 (66.7%) patients achieved a complete response (CR) on day 14 in the E. coli-asparaginase and PEG-asparaginase groups, respectively (P = 0.032). No different 5-year event-free survival (EFS) or overall survival (OS) rate (P = 0.632 and 0.769) was observed. Multivariate analysis revealed later CR (P = 0.008) and older age (P = 0.049) as adverse prognostic factors for both EFS and OS. In addition, we specifically monitored the known adverse effects of asparaginase, and no asparaginase-related death was observed. Allergy occurred in 9 patients using E. coli-asparaginase, and no patient in the PEG-asparaginase group suffered from allergies (P < 0.001). The incidence of other asparaginase-related toxicities was similar. We conclude that PEG-asparaginase can be safely and effectively used as asparaginase in adults with newly diagnosed standard-risk ALL.

Outcomes Following Discontinuation of E. coli l-Asparaginase Upon Severe Allergic Reactions in Children With Acute Lymphoblastic Leukemia

BACKGROUND

Discontinuation of E. coli l-asparaginase in patients with acute lymphoblastic leukemia (ALL) is unavoidable upon severe allergic reaction. We sought to examine outcomes following E. coli l-asparaginase discontinuation due to severe allergic reactions.

PROCEDURE

We evaluated the outcome of children enrolled in Taiwan Pediatric Oncology Group-2002-ALL protocol between 2002 and 2012, who had E. coli l-asparaginase discontinued due to severe allergic reactions, and compared the outcomes of those who continued with Erwinia l-asparaginase (Erwinase) with those who did not.

RESULTS

Among 700 patients enrolled in this study, 33 patients had E. coli l-asparaginase treatment discontinued due to severe allergic reactions. Five-year overall survival did not differ significantly among the 648 patients without discontinuation (81 ± 1.6%, mean ± SE), compared to 17 patients with allergic reactions and treated with Erwinase (88 ± 7.8%) and 16 patients with allergic reactions but not treated with Erwinase (87 ± 8.6%). Among 16 patients who did not receive Erwinase, all 10 who received ≥50% of the scheduled doses of E. coli l-asparaginase before discontinuation survived without events.

CONCLUSIONS

Erwinase treatment may not be needed for some ALL patients with severe allergy to E. coli l-asparaginase if ≥50% of prescribed doses were received and/or therapy is augmented with other agents.

Asparaginase-associated toxicity in children with acute lymphoblastic leukemia

Asparaginase is an integral component of multiagent chemotherapy regimens for the treatment of children with acute lymphoblastic leukemia. Positive outcomes are seen in patients who are able to complete their entire prescribed course of asparaginase therapy. Toxicities associated with asparaginase use include hypersensitivity (clinical and subclinical), pancreatitis, thrombosis, encephalopathy, and liver dysfunction. Depending on the nature and severity of the toxicity, asparaginase therapy may be altered or discontinued in some patients. Clinical hypersensitivity is the most common asparaginase-associated toxicity requiring treatment discontinuation, occurring in up to 30% of patients receiving Escherichia coli-derived asparaginase. The ability to rapidly identify and manage asparaginase-associated toxicity will help ensure patients receive the maximal benefit from asparaginase therapy. This review will provide an overview of the common toxicities associated with asparaginase use and recommendations for treatment management.

PEG-asparaginase allergy in children with acute lymphoblastic leukemia in the NOPHO ALL2008 protocol

BACKGROUND

L-Asparaginase is an effective drug in the treatment of childhood acute lymphoblastic leukemia (ALL). The use of L-asparaginase may be limited by serious adverse events of which allergy is the most frequent. The objective of this study was to describe the clinical aspects of PEG-asparaginase allergy in children treated according to the Nordic Society of Paediatric Haematology and Oncology (NOPHO) ALL2008 protocol.

PROCEDURE

Children (1-17 years) enrolled in the NOPHO ALL2008 protocol between July 2008 and August 2011, who developed PEG-asparaginase allergy were identified through the NOPHO ALL2008 toxicity registry. In the NOPHO ALL2008 protocol, patients are randomized to 8 or 15 doses of intramuscular PEG-asparaginase (Oncaspar®) 1,000 IU/m(2) /dose administered at 2 or 6 weeks intervals during a total period of 30 weeks. (Clinical trials.gov no: NCT00819351).

RESULTS

Of 615 evaluable patients, 79 patients developed clinical PEG-asparaginase allergy (cumulative risk; 13.2%) and discontinued PEG-asparaginase therapy for that reason. PEG-asparaginase allergy occurred after a median of two doses (75% range 2-4, max 14). In 58% of PEG-asparaginase hypersensitive patients, the clinical allergic reactions appeared within 2 hr after PEG-asparaginase administration and ranged from mild symptoms to systemic anaphylaxis. Nine patients experienced an anaphylactic reaction within 1 hr and 50 min from asparaginase administration; none were fatal. Four of 68 patients (6%) who subsequently received Erwinase therapy also reacted allergic to Erwinase.

CONCLUSION

Clinical allergy to PEG-asparaginase occurred early in treatment, was in general moderate in severity, and mostly developed within 2 hr after PEG-asparaginase administration. The risk of subsequent Erwinase allergic reactions was low.

Clinical utility and implications of asparaginase antibodies in acute lymphoblastic leukemia

Hypersensitivity to asparaginase is common, but the differential diagnosis can be challenging and the diagnostic utility of antibody tests is unclear. We studied allergic reactions and serum antibodies to E. coli asparaginase (Elspar) in 410 children treated on St. Jude Total XV protocol for acute lymphoblastic leukemia. Of 169 patients (41.2%) with clinical allergy, 147 (87.0%) were positive for anti-Elspar antibody. Of 241 patients without allergy, 89 (36.9%) had detectable antibody. Allergies (P=0.0002) and antibodies (P=6.6 × 10(-6)) were higher among patients treated on the low-risk arm than among those treated on the standard/high-risk arm. Among those positive for antibody, the antibody titers were higher in those who developed allergy than in those who did not (P<1 × 10(-15)). Antibody measures at week 7 of continuation therapy had a sensitivity of 87-88% and a specificity of 68-69% for predicting or confirming clinical reactions. The level of antibodies was inversely associated with serum asparaginase activity (P=7.0 × 10(-6)). High antibody levels were associated with a lower risk of osteonecrosis (odds ratio=0.83; 95% confidence interval, 0.78-0.89; P=0.007). Antibodies were related to clinical allergy and to low systemic exposure to asparaginase, leading to lower risk of some adverse effects of therapy.

Polyethylene Glycol-conjugated L-asparaginase versus native L-asparaginase in combination with standard agents for children with acute lymphoblastic leukemia in second bone marrow relapse: a Children's Oncology Group Study (POG 8866)

BACKGROUND

Administration of L-asparaginase is limited by hypersensitivity reactions mediated by anti-asparaginase antibodies. To overcome this problem, native Escherichia coli L-asparaginase was conjugated to polyethylene glycol (PEG) to formulate PEG-L-asparaginase, a preparation with decreased immunogenicity and increased circulating half-life. In early trials, PEG-L-asparaginase was tolerated by patients known to be hypersensitive to the native E. coli product.

METHODS

The Pediatric Oncology Group conducted a phase II, randomized trial to compare the efficacy and toxicity of PEG-L-asparaginase compared with native E. coli asparaginase in children with acute lymphoblastic leukemia in second bone marrow relapse. All patients (n=76) received standard doses of vincristine and prednisone. Nonhypersensitive patients (n=34) were randomized to receive either PEG-L-asparaginase of 2500 IU/m/dose intramuscularly on days 1 and 15 (treatment I) or native E. coli asparaginase of 10,000 IU/m/dose intramuscularly on days 1, 3, 5, 8, 10, 12, 15, 17, 19, 22, 24, and 26 (treatment II). Patients with a clinical history of an allergic reaction to unmodified asparaginase were directly assigned to treatment with PEG-L-asparaginase (n=42). Asparaginase levels and anti-asparaginase antibody titers were monitored in all patients. Response and toxicity were scored using conventional criteria.

RESULTS

The complete response rate for the total study population was 41%. There was no difference in complete response between patients randomized to PEG (47%) and native asparaginase (41%). PEG was well tolerated even in patients with prior allergic reactions to native asparaginase. PEG half-life was shorter in patients with prior allergy.

CONCLUSIONS

PEG asparaginase is a useful agent in patients with allergic reactions to native asparaginase.

Cell-cycle inhibition by Helicobacter pylori L-asparaginase

Helicobacter pylori (H. pylori) is a major human pathogen causing chronic gastritis, peptic ulcer, gastric cancer, and mucosa-associated lymphoid tissue lymphoma. One of the mechanisms whereby it induces damage depends on its interference with proliferation of host tissues. We here describe the discovery of a novel bacterial factor able to inhibit the cell-cycle of exposed cells, both of gastric and non-gastric origin. An integrated approach was adopted to isolate and characterise the molecule from the bacterial culture filtrate produced in a protein-free medium: size-exclusion chromatography, non-reducing gel electrophoresis, mass spectrometry, mutant analysis, recombinant protein expression and enzymatic assays. L-asparaginase was identified as the factor responsible for cell-cycle inhibition of fibroblasts and gastric cell lines. Its effect on cell-cycle was confirmed by inhibitors, a knockout strain and the action of recombinant L-asparaginase on cell lines. Interference with cell-cycle in vitro depended on cell genotype and was related to the expression levels of the concurrent enzyme asparagine synthetase. Bacterial subcellular distribution of L-asparaginase was also analysed along with its immunogenicity. H. pylori L-asparaginase is a novel antigen that functions as a cell-cycle inhibitor of fibroblasts and gastric cell lines. We give evidence supporting a role in the pathogenesis of H. pylori-related diseases and discuss its potential diagnostic application.

Tolerability and efficacy of L-asparaginase therapy in pediatric patients with acute lymphoblastic leukemia

L-asparaginase (L-ASNase) has been an essential component of multiagent chemotherapy for acute lymphoblastic leukemia in childhood for over 3 decades. There are currently 2 Food and Drug Administration (FDA)-approved formulations of L-ASNase derived from Escherichia coli and 1 non-FDA approved formulation derived from Erwinia chrysanthemi. Modifications in L-ASNase have included pegylation, which decreases drug immunogenicity and increases the half-life, allowing less frequent administration. Although L-ASNase is well-tolerated in most patients and causes little myelosuppression, significant toxicities occur in up to 30% of patients. Hypersensitivity is the most common toxicity of L-ASNase therapy and limits the further use of the drug. Other significant toxicities relate to a reduction in protein synthesis and include pancreatitis, thrombosis, central nervous system complications, and liver dysfunction. The spectrum of common toxicities and the efficacy of different formulations of L-ASNase are presented in this review.

Genetic variations in GRIA1 on chromosome 5q33 related to asparaginase hypersensitivity

The genetic variations that result in allergy to asparaginase are as yet undetermined. We interrogated more than 500,000 single-nucleotide polymorphisms (SNPs) in 485 children with acute lymphoblastic leukemia (ALL), 322 in a discovery cohort, and 163 in a validation cohort. In the top 100 SNPs associated with allergy in the discovery cohort, chromosome 5 was overrepresented as compared with other chromosomes (P = 0.00032), hosting 10 SNPs annotated to genes. Among these 10 SNPs, one SNP (rs4958351) [corrected], in GRIA1 on chromosome 5q33, was replicated in the validation cohort (P = 1.8 x 10(-5), 2.9 x 10(-3), and 3.5 x 10(-7) in the discovery, validation, and combined cohorts, respectively). Four additional SNPs annotated to GRIA1 were also significantly associated with allergy (P < 0.05) in both cohorts. Chromosome 5q33 has previously been associated with asthma and atopy. These data contribute to the growing body of evidence that there is an inherited component to predisposition to drug allergy.

Erwinia asparaginase after allergy to E. coli asparaginase in children with acute lymphoblastic leukemia

BACKGROUND

Escherichia coli asparaginase is an important component of treatment for childhood acute lymphoblastic leukemia (ALL); however, hypersensitivity develops in up to 30% of patients. We assessed the nadir enzyme activity and tolerability of Erwinia asparaginase, an alternative preparation, in E. coli asparaginase-allergic patients.

PATIENTS AND METHODS

Between 2000 and 2002, 215 children with newly diagnosed ALL were enrolled on Dana-Farber Cancer Institute ALL Consortium Protocol 00-01 and were to receive 30 weekly doses of intramuscular E. coli asparaginase. If E. coli asparaginase allergy developed, patients were switched to twice-weekly intramuscular Erwinia asparaginase (25,000 IU/m(2)). Nadir serum asparaginase activity (NSAA) was measured every 3 weeks.

RESULTS

Forty-two patients (20%) developed E. coli asparaginase allergy and switched to Erwinia. Of 38 patients with evaluable samples, 34 (89%) Erwinia-treated patients had at least one therapeutic NSAA (> or =0.1 IU/ml). The median NSAA was 0.247 IU/ml 3 days and 0.077 IU/ml 4 days after an Erwinia dose. Associated toxicities included allergy in 14 (33%) and pancreatitis in 3 patients (7%). At a median follow-up of 5.4 years, event-free survival (+/-standard error) of the 42 patients who switched to Erwinia was 86 +/- 5% compared with 81 +/- 3% for the 170 patients without E. coli asparaginase allergy (P = 0.55).

CONCLUSIONS

Twice-weekly Erwinia asparaginase was well tolerated and achieved a therapeutically effective NSAA in most E. coli asparaginase-allergic patients. Development of E. coli allergy and subsequent treatment with twice-weekly Erwinia did not adversely impact event-free survival. Erwinia asparaginase should be considered for E. coli asparaginase-allergic patients.

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.