PEG-asparaginase

Drug delivery vehicles on a nano-engineering perspective

Nanoengineered drug delivery systems (nDDS) have been successfully used as clinical tools for not only modulation of pharmacological drug release profile but also specific targeting of diseased tissues. Until now, encapsulation of anti-cancer molecules such as paclitaxel, vincristin and doxorubicin has been the main target of nDDS, whereby liposomes and polymer-drug conjugates remained as the most popular group of nDDS used for this purpose. The success reached by these nanocarriers can be imitated by careful selection and optimization of the different factors that affect drug release profile (i.e. type of biomaterial, size, system architecture, and biodegradability mechanisms) along with the selection of an appropriate manufacture technique that does not compromise the desired release profile, while it also offers possibilities to scale up for future industrialization. This review focuses from an engineering perspective on the different parameters that should be considered before and during the design of new nDDS, and the different manufacturing techniques available, in such a way to ensure success in clinical application.

Cell-penetrating peptides meditated encapsulation of protein therapeutics into intact red blood cells and its application

Red blood cells (RBCs) based drug carrier appears to be the most appealing for protein drugs due to their unmatched biocompatability, biodegradability, and long lifespan in the circulation. Numerous methods for encapsulating protein drugs into RBCs were developed, however, most of them induce partial disruption of the cell membrane, resulting in irreversible alterations in both physical and chemical properties of RBCs. Herein, we introduce a novel method for encapsulating proteins into intact RBCs, which was meditated by a cell penetrating peptide (CPP) developed in our lab-low molecular weight protamine (LMWP). l-asparaginase, one of the primary drugs used in treatment of acute lymphoblastic leukemia (ALL), was chosen as a model protein to illustrate the encapsulation into erythrocytes mediated by CPPs. In addition current treatment of ALL using different l-asparaginase delivery and encapsulation methods as well as their associated problems were also reviewed.

[Update on L-asparaginase treatment in paediatrics]

L-asparaginase (L-ASP) is one of the cornerstones of the treatment of acute lymphoblastic leukemia and non-Hodgkin lymphoma. It is an enzyme of bacterial origin capable of transforming L-asparagine to aspartic acid. The extracellular depletion of L-asparagine inhibits protein synthesis in lymphoblasts, inducing their apoptosis. Numerous studies have demonstrated that treatment with L-ASP improves survival of patients, but there are clear differences in the characteristics of the three currently available formulations. This article reviews the dosage, activity and side effects of the two L-ASP derived from Escherichia coli (native and pegylated), and the one derived from Erwinia chrysanthemi (Erwinia ASP). Despite its indisputable indication over the past50 years, there are still many points of contention, and its use is still marked by the side effects of the inhibition of protein synthesis. The short half-life of native forms, and the most frequently used parenteral administration by intramuscular injections, affects the quality of life of the patients. Therefore, recent studies claim to evaluate alternatives, such as the formulation of longer half-life pegylated L-ASP, and the use of intravenous formulations. There are encouraging results to date with both preparations. Still, further studies are needed to establish which should be the formulation and frontline indicated route of administration, optimal dosing, and management of adverse effects.

Cost-analysis of treatment of childhood acute lymphoblastic leukemia with asparaginase preparations: the impact of expensive chemotherapy

Asparaginase is an expensive drug, but important in childhood acute lymphoblastic leukemia. In order to compare costs of PEGasparaginase, Erwinia asparaginase and native E. coli asparaginase, we performed a cost-analysis in the Dutch Childhood Oncology Group ALL-10 medium-risk group intensification protocol. Treatment costs were calculated based on patient level data of 84 subjects, and were related to the occurrence of allergy to PEGasparaginase. Simultaneously, decision tree and sensitivity analyses were conducted. The total costs of the intensification course of 30 weeks were $57,893 in patients without PEGasparaginase allergy (n=64). The costs were significantly higher ($113,558) in case of allergy (n=20) necessitating a switch to Erwinia asparaginase. Simulated scenarios (decision tree analysis) using native E. coli asparaginase in intensification showed that the costs of PEGasparaginase were equal to those of native E. coli asparaginase. Also after sensitivity analyses, the costs for PEGasparaginase were equal to those of native E. coli asparaginase. Intensification treatment with native E. coli asparaginase, followed by a switch to PEGasparaginase, and subsequently to Erwinia asparaginase in case of allergy had similar overall costs compared to the treatment with PEGasparaginase as the first-line drug (followed by Erwinia asparaginase in the case of allergy). PEGasparaginase is preferred over native E. coli asparaginase, because it is administered less frequently, with less day care visits. PEGasparaginase is less immunogenic than native E. coli asparaginase and is not more expensive. Asparaginase costs are mainly determined by the percentage of patients who are allergic and require a switch to Erwinia asparaginase.

Purification, characterization and kinetic properties of extracellular L-asparaginase produced by Cladosporium sp

L-asparaginase from Cladosporium sp. grown on wheat bran by SSF was purified. Enzyme appeared to be a trimer with homodimer of 37 kDa and another 47 kDa amounting to total mass of 121 kDa as estimated by SDS-PAGE and 120 kDa on gel filtration column. The optimum temperature and pH of the enzyme were 30 °C and 6.3, respectively with Vmax of 4.44 μmol/mL/min and Km of 0.1 M. Substrate specificity studies indicated that, L-asparaginase has greater affinity towards L-asparagine with substrate hydrolysis efficiency (Vmax/Km ratio) eightfold higher than that of L-glutamine. L-asparaginase activity in presence of thiols studied showed decrease in Vmax and increase in Km, indicating nonessential mode of inactivation. Among the thiols tested, β-mercaptomethanol, exerted inhibitory effect, suggesting a critical role of disulphide linkages in maintaining a suitable conformation of the enzyme. Metal ions such as Ca(2+), Co(2+), Cu(2+), Mg(2+), Na(+), K(+) and Zn(2+) significantly affected enzyme activity whereas presence of Fe(3+), Pb(2+) and KI stimulated the activity. Detergents studied also enhanced L-asparaginase activity. In-vitro half-life of purified L-asparaginase in mammalian blood serum was 93.69 h. The enzyme inhibited acrylamide formation in potato chips by 96 % making it a potential candidate for food industry to reduce acrylamide content in starchy fried food commodities.

Engineering reduced-immunogenicity enzymes for amino acid depletion therapy in cancer

Cancer has become the leading cause of death in the developed world and has remained one of the most difficult diseases to treat. One of the difficulties in treating cancer is that conventional chemotherapies often have unacceptable toxicities toward normal cells at the doses required to kill tumor cells. Thus, the demand for new and improved tumor specific therapeutics for the treatment of cancer remains high. Alterations to cellular metabolism constitute a nearly universal feature of many types of cancer cells. In particular, many tumors exhibit deficiencies in one or more amino acid synthesis or salvage pathways forcing a reliance on the extracellular pool of these amino acids to satisfy protein biosynthesis demands. Therefore, one treatment modality that satisfies the objective of developing cancer cell-selective therapeutics is the systemic depletion of that tumor-essential amino acid, which can result in tumor apoptosis with minimal side effects to normal cells. While this strategy was initially suggested over 50 years ago, it has been recently experiencing a renaissance owing to advances in protein engineering technology, and more sophisticated approaches to studying the metabolic differences between tumorigenic and normal cells. Dietary restriction is typically not sufficient to achieve a therapeutically relevant level of amino acid depletion for cancer treatment. Therefore, intravenous administration of enzymes is used to mediate the degradation of such amino acids for therapeutic purposes. Unfortunately, the human genome does not encode enzymes with the requisite catalytic or pharmacological properties necessary for therapeutic purposes. The use of heterologous enzymes has been explored extensively both in animal studies and in clinical trials. However, heterologous enzymes are immunogenic and elicit adverse responses ranging from anaphylactic shock to antibody-mediated enzyme inactivation, and therefore have had limited utility. The one notable exception is Escherichia colil-asparaginase II (EcAII), which has been FDA-approved for the treatment of childhood acute lymphoblastic leukemia. The use of engineered human enzymes, to which natural tolerance is likely to prevent recognition by the adaptive immune system, offers a novel approach for capitalizing on the promising strategy of systemic depletion of tumor-essential amino acids. In this work, we review several strategies that we have developed to: (i) reduce the immunogenicity of a nonhuman enzyme, (ii) engineer human enzymes for novel catalytic specificities, and (iii) improve the pharmacological characteristics of a human enzyme that exhibits the requisite substrate specificity for amino acid degradation but exhibits low activity and stability under physiological conditions.

Cost-effectiveness of treatment of childhood acute lymphoblastic leukemia with chemotherapy only: the influence of new medication and diagnostic technology

BACKGROUND

Survival for childhood acute lymphoblastic leukemia (ALL) has reached 80-90%. Future improvement in treatment success will involve new technologies and medication, adding to the pressure on limited financial resources. Therefore a retrospective cost-effectiveness analysis of ALL treatment with chemotherapy only according to the two most recent Dutch Childhood Oncology Group treatment protocols was performed. The most recent protocol ALL10 included more expensive medication (pegasparaginase) and implemented a new diagnostic technique (minimal residual disease levels) compared to the previous ALL9 protocol.

PROCEDURE

Fifty children from a single center cohort were included. All direct medical costs made during treatment, including those in satellite hospitals, were determined. Costs per life year saved (LYS) were calculated. The cost-effectiveness ratio of the most recent treatment protocol was determined. LYS were calculated based on national 5-year event-free survival.

RESULTS

Mean total costs were between $115,858 (ALL9) and $163,350 (ALL10) per patient. Hospital admissions (57%) and medication (11-17%) were important drivers of overall costs, and were higher in the most recent protocol ALL10. Costs per LYS were $1,962 (ALL9) and $2,655 (ALL10) and the cost-effectiveness ratio was $8,215.

CONCLUSION

Treatment of childhood ALL with chemotherapy only is well within accepted ranges of cost-effectiveness. The use of new technology and more expensive medication in the most recent protocol ALL10 lead to higher costs but more LYS. In future (ALL) treatment protocols, costs in relation to effects should be taken into account in order to establish more cost-effective disease management without jeopardizing survival and quality of life.

The first characterized asparaginase from a basidiomycete, Flammulina velutipes

Flammulina velutipes enjoys high popularity as an edible mushroom in Asian cuisines. Investigating the secretion of peptidases in nutrient media enriched with gluten, an enzyme was noticed that catalyzed the deamidation of L-asparagine and L-glutamine. The enzyme was purified to electrophoretic homogeneity by foaming and SEC. PAGE analysis revealed a protein of about 85 kDa with 13 kDa subunits indicating a hexameric protein. Degenerated primers were deduced from peptide fragments and the complete coding sequence of 372 bp was determined. The gene of Flammulina velutipes asparaginase (FvNase) over expressed in E. coli achieved an L-asparagine-hydrolyzing activity of 16 U/mL in crude extract, which was five times higher than its L-glutamine-hydrolyzing ability. The enzyme showed a pH-optimum at pH 7, remarkable tolerance towards elevated temperature and sodium chloride concentration in both the native and recombinant form, and no significant homology to any conserved domains of published asparaginases or glutaminases.

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.

L-asparaginase treatment in acute lymphoblastic leukemia: a focus on Erwinia asparaginase

Asparaginases are a cornerstone of treatment protocols for acute lymphoblastic leukemia (ALL) and are used for remission induction and intensification treatment in all pediatric regimens and in the majority of adult treatment protocols. Extensive clinical data have shown that intensive asparaginase treatment improves clinical outcomes in childhood ALL. Three asparaginase preparations are available: the native asparaginase derived from Escherichia coli (E. coli asparaginase), a pegylated form of this enzyme (PEG-asparaginase), and a product isolated from Erwinia chrysanthemi, ie, Erwinia asparaginase. Clinical hypersensitivity reactions and silent inactivation due to antibodies against E. coli asparaginase, lead to inactivation of E. coli asparaginase in up to 60% of cases. Current treatment protocols include E. coli asparaginase or PEG-asparaginase for first-line treatment of ALL. Typically, patients exhibiting sensitivity to one formulation of asparaginase are switched to another to ensure they receive the most efficacious treatment regimen possible. Erwinia asparaginase is used as a second- or third-line treatment in European and US protocols. Despite the universal inclusion of asparaginase in such treatment protocols, debate on the optimal formulation and dosage of these agents continues. This article provides an overview of available evidence for optimal use of Erwinia asparaginase in the treatment of ALL.

Peg-asparaginase for acute lymphoblastic leukemia

IMPORTANCE OF THE FIELD

Asparaginase is a prominent component of pediatric and adolescent treatment for acute lymphoblastic leukemia. These treatment regimens are now being employed in adults. Knowledge of the efficacy and toxicity of asparaginase preparations is essential when using these treatments. AREAS COVERED BY THIS REVIEW: The search terms used were asparaginase, leukemia, pegylated, oncaspar, adolescent and young adult. Literature was searched in Pubmed/Medline with no limitations on year of publication. Abstracts from the American Society of Hematology meetings and the American Society of Clinical Oncology were searched from 2004 - 2008 using the same terms.

WHAT THE READER WILL GAIN

The reader will gain knowledge of the tolerability and efficacy of pegylated asparaginase when treating acute lymphoblastic leukemia.

TAKE HOME MESSAGE

Pegylated asparaginase is generally well tolerated in adult patients with efficacy that appears to be at least equivalent to native asparaginase preparations.

Hydrogel-magnetic nanoparticles with immobilized L-asparaginase for biomedical applications

The association of magnetic nanoparticles, which could be controlled by a magnetic field and have dimensions which facilitate their penetration in cells/tissues, with hydrogel type biopolymeric shells confer them compatibility and the capacity to retain and deliver bioactive substances. The main objective of this work is the development of a new system based on a biocompatible polymer with organic-inorganic structure capable of vectoring support for biologic active agents (L: -asparaginase, e.g.). Characterization of size and morphology of the hydrogel-magnetic nanoparticles with entrapped L: -asparaginase was made using Dynamic Light Scattering method, Transmission Electron Microscopy and Confocal Microscopy. The structure of magnetic nanoparticles coated with hydrogel was characterized by Fourier Transformed Infrared Spectroscopy. The cytotoxicity of nanoparticles was evaluated and also the interactions with microorganisms. We obtained hydrogel-magnetic nanoparticles with L: -asparaginase entrapped, with sizes below 30 nm in dried stage, capable to penetrate the cells and tissues.

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.

Alternative algorithm for L-asparaginase allergy in children with acute lymphoblastic leukemia

BACKGROUND

L-asparaginase is a crucial chemotherapeutic agent for the treatment of acute lymphoblastic leukemia. The alternatives to L-asparaginase are not available in many parts of the world, including Turkey.

OBJECTIVE

We sought to evaluate the utility of premedication with or without a desensitization protocol in children with acute lymphoblastic leukemia and systemic hypersensitivity reactions to Escherichia coli-asparaginase.

METHODS

In this prospective study patients with systemic hypersensitivity reactions to E coli-asparaginase for whom we were unable to ascertain/provide other alternatives to asparaginase were either premedicated, desensitized, or both to receive their chemotherapy as E coli-asparaginase according to the severity of the hypersensitivity reaction.

RESULTS

Nineteen patients (13 male patients) with a mean age of 7.4 +/- 4.7 years experienced a systemic hypersensitivity reaction to E coli-asparaginase during a 4-year period. Polyethylene glycol-asparaginase could be used for 3 patients. Eight of the remaining 16 children, who had experienced anaphylaxis, were premedicated and desensitized with E coli-asparaginase, and in 7 patients treatment was tolerated. The other 8 patients, with acute allergic reactions to E coli-asparaginase, were premedicated first, and 5 of them showed no reaction subsequently. Three of them demonstrated systemic hypersensitivity reactions again (anaphylaxis, n = 3), and premedication and desensitization with E coli-asparaginase resulted in anaphylaxis. Polyethylene glycol-asparaginase was administered uneventfully to the patients who could be provided it.

CONCLUSION

E coli-asparaginase could be administered to more than half of the patients who had a hypersensitivity reaction, and all of these patients were able to receive their planned doses of asparaginase. In countries with shortages of alternative asparaginase preparations, our approach might be a suitable option.