Combination therapy with methotrexate, vincristine, polyethylene-glycol conjugated-asparaginase, and prednisone in the treatment of patients with refractory or recurrent acute lymphoblastic leukemia

Pegylated asparaginase-induced liver injury, a case-based review and data from pharmacovigilance

Treatment of acute lymphoblastic leukemia has changed since introducing the asparaginase drug and its pegylated form, i.e., pegasparaginase. Several trials have demonstrated a clear advantage in using this drug in adolescents and young adults, up to 60 years. However, this drug possesses a unique plethora of side effects, spanning from pancreatitis to coagulopathy, including hepatotoxicity. This could be of mild intensity but can lead to life-threatening sequelae, up to death. Here, we report a case of a 59 years old patient affected by acute lymphoblastic leukemia, who eventually died cause of pegasparaginase-related hepatotoxicity. A review of the available literature will be provided, including epidemiology, pathophysiology and possible therapeutic interventions. In the end, an analysis of the Italian pharmacovigilance database will be presented, where hepatotoxicity has been reported in 32 cases (10% of reported adverse events, including 3 deaths related to drug-induced liver damage). This article is protected by copyright. All rights reserved.

Cardiac Relapse of Acute Lymphoblastic Leukemia Following Hematopoietic Stem Cell Transplantation: A Case Report and Review of Literature

Isolated extramedullary relapse of acute lymphoblastic leukemia (ALL) occurs in soft tissues and various organs outside the testis and central nervous system. Treatments such as hematopoietic stem cell transplantation and more novel modalities such as immunotherapy have eradicated ALL at extramedullary sites. In some instances, survival times for relapsed ALL at these sites are longer than those for relapsed disease involving only the bone marrow. Isolated relapse of ALL in the myocardium is rare, especially in children, making diagnosis and treatment of it difficult. More recent treatment options such as chimeric antigen receptor T-cell therapy carry a high risk of cytokine release syndrome and associated risk of worsening cardiac function. Herein we present the case of an 11-year-old boy who presented with relapsed symptomatic B-cell ALL in the myocardium following allogeneic hematopoietic stem cell transplantation. This is an unusual presentation of relapsed ALL and this case demonstrates the associated challenges in its diagnosis and treatment. The case report is followed by a literature review of the advances in treatment of pediatric leukemia and their application to extramedullary relapse of this disease in particular.

The effect of asparaginase therapy on methotrexate toxicity and efficacy in children with acute lymphoblastic leukemia

Asparaginase and methotrexate (MTX), both essential for pediatric acute lymphoblastic leukemia therapy, are often used concomitantly. Depending on the sequence, in vitro, asparaginase inhibits MTX-polyglutamate (MTXPG) formation, and side effects overlap. MTX toxicity and efficacy, reflected by intracellular erythrocyte MTXPG's, were compared between children treated with and without asparaginase during high dose MTX (HD-MTX) courses of the DCOG ALL-11 protocol (NL50250.078.14). Seventy-three patients, of whom 23 received asparaginase during the HD-MTX courses, were included. Grade 3-4 leukopenia and neutropenia occurred more often (59% and 86% vs. 30% and 62%). The number of infections, grade 3-4 hepatotoxicity, nephrotoxicity, and neurotoxicity did not differ. Patients with asparaginase had lower MTXPG levels, although to a lesser extent than in vitro studies. Although patients with asparaginase during HD-MTX courses showed more myelosuppression, this had no (serious) clinical consequences. Regarding the MTX efficacy, the schedule-related antagonism seen in in vitro seems less important in vivo.

Isolation, Purification, Characterisation and Application of L-ASNase: A Review

BACKGROUND

L-ASNase (L-asparagine aminohydrolase EC 3.5.1.1) is used for the conversion of L-asparagine to L-aspartic acid and ammonia and also it was found as an agent of chemotherapeutic property according to recent patents. It is known as an anti-cancer agent and recently it has received an immense attention. Various microorganisms have the ability to secrete the L-ASNase. It is famous world-wide as anti-tumor medicine for acute lymphoblastic leukemia and lymphosarcoma. L-ASNase helps in deamination of Asparagine and Glutamine.

SOURCE

L-ASNase mainly found in two bacterial sources; Escherichia coli and Erwinia carotovora. Isolation from plants: Endophytes were also a great source of L-ASNase. It was isolated from four types of plants named as; C. citratus, O. diffusa, M. koengii, and also P. bleo.

APPLICATIONS

L-ASNase is used as a potential anti-tumor medicine. It plays a very much essential role for the growth of tumor cells. Tumor cells require a lot of asparagine for their growth. But ASNase converts to aspartate and ammonia from asparagine. So the tumor cell does not proliferate and fails to survive. The L-ASNase is used as the medicine for the major type of cancer like acute lymphocytic leukemia (ALL), brain. It also used as a medicine for central nervous system (CNS) tumors, and also for neuroblastoma. Two types of L-ASNase have been found.

CONCLUSION

L-ASNase becomes a powerful anti-tumor medicine and researchers should develop a potent strain of asparaginase which can produce asparaginase in the industrial level. It is also used in the pharmaceutical industry and food industry on a broader scale.

Safety and Toxicity of Recombinant Methioninase and Polyethylene Glycol (PEG) Recombinant Methioninase in Primates

Methionine (MET) is a general metabolic therapeutic target in cancer, whereby cancer cells have an elevated requirement for MET, termed MET dependence. We have developed recombinant L-methionine α-deamino-γ-mercaptomethane lyase (recombinant methioninase [rMETase, EC 4.4.1.11]) as targeted therapy of all cancer types. Pharmacokinetics, MET depletion, antigenicity, and toxicity of rMETase were examined in macaque monkeys. Pharmacokinetic analysis showed that rMETase was eliminated with a T_1/2 of 2.49 h. A 2-week i.v. administration of 4000 units/kg every 8 h/day for 2 weeks resulted in a steady-state depletion of plasma MET to less than 2 μM. The only manifest toxicity was decreased food intake and slight weight loss. Serum albumin and red-cell values declined transiently during treatment. Rechallenge on day 28 resulted in anaphylactic shock and death in one animal. Pretreatment with hydrocortisone prevented the anaphylactic reaction. Anti-rMETase antibodies (at 10^-3) were found after the first challenge, increased to 10^-6 after the fourth challenge, and decreased to 10^-2 by 2 months post-therapy. Therefore, the therapeutic potential of rMETase is limited by its short plasma half-life and immunologic effects, including high antibody production in mice and anaphylactic reactions in monkeys. To overcome these limits, rMETase has been coupled to methoxypolyethylene glycol succinimidyl glutarate polyethylene glycol (MEGC-PEG-5000). The pharmacokinetics, antigenicity, and toxicity of MEGC-PEG-rMETase in macaque monkeys were evaluated using an escalating-dose strategy. In pharmacokinetic studies, a single 4000 units/kg dose showed that MEGC-PEG-rMETase holoenzyme activity was eliminated with a biological half-life of 1.3 h, and the MEGC-PEG-rMETase apoenzyme was eliminated with a biological half-life of 90 h, a 36-fold increase compared with non-PEGylated rMETase. The disparity in the T_½ of the apoenzyme and the holoenzyme reflects the loss of co-factor pyridoxal-L-phosphate of the circulating MEGC-PEG-rMETase. A 7-day i.v. administration of 4000 units/kg every 12 h resulted in a steady-state depletion of plasma MET to <5 μmol/L. The only manifest toxicity was decreased food intake and slight weight loss. Red cell values and hemoglobin declined transiently. Subsequent challenges did not result in any immunologic reactions. Anti-MEGC-PEG-rMETase antibodies were 100- to 1000-fold less than antibodies elicited by naked rMETase, thereby suggesting clinical potential of MEGC-PEG-rMETase as a broad anticancer agent.

A critical review on properties and applications of microbial l-asparaginases

l-Asparaginase is one of the main drugs used in the treatment of acute lymphoblastic leukemia (ALL), a commonly diagnosed pediatric cancer. Although several microorganisms are found to produce l-asparaginase, only the purified enzymes from E. coli and Erwinia chrysanthemi are employed in the clinical and therapeutic applications in humans. However, their therapeutic response seldom occurs without some evidence of hypersensitivity and other toxic side effects. l-Asparaginase is also of prospective use in food industry to reduce the formation of acrylamide in fried, roasted or baked food products. This review is an attempt to compile information on the properties of l-asparaginases obtained from different microorganisms. The complications involved with the therapeutic use of the currently available l-asparaginases, and the enzyme's potential application as a food processing aid to mitigate acrylamide formation have also been reviewed. Further, avenues for searching alternate sources of l-asparaginase have been discussed, highlighting the prospects of endophytic microorganisms as a possible source of l-asparaginases with varied biochemical and pharmacological properties.

Phase II study of methotrexate, vincristine, pegylated-asparaginase, and dexamethasone (MOpAD) in patients with relapsed/refractory acute lymphoblastic leukemia

Newer approaches are needed for the treatment of relapsed and refractory acute lymphoblastic leukemia (ALL). Asparaginase-based regimens are active in the treatment of pediatric ALL and may be important in salvage therapy for adult patients. We conducted a pilot trial combining methotrexate, vincristine, PEGylated-asparaginase, and dexamethasone (MOpAD) in adults with relapsed or refractory ALL. We added tyrosine kinase inhibitors in patients with Philadelphia chromosome positive (Ph+) ALL and rituximab in patients with CD20 positive B-cell ALL. Among 37 patients treated (median age 42 years; median 2 prior therapies), the complete remission (CR) rate was 28% and an overall response rate (ORR) was 39%. The median CR duration was 4.3 months. Patients with Ph+ ALL had CR and ORR of 50% and 67%, respectively and the CR and ORR in patients with T-cell leukemia were 45% and 56%, respectively. The median survival in patients with CR/CRp was 10.4 versus 3.4 months in nonresponders (P = 0.02). The most common grade 3 or 4 nonhematologic toxicities were elevations in bilirubin and transaminases, nausea, peripheral neuropathy, and hyperglycemia, which were managed with supportive care, dose adjustments, and interruptions.

How to manage asparaginase hypersensitivity in acute lymphoblastic leukemia

Outcomes for children with acute lymphoblastic leukemia (ALL) have improved significantly in recent decades, primarily due to dose-intensified, multi-agent chemotherapy regimens, of which asparaginase has played a prominent role. Despite this success, hypersensitivity remains a significant problem, often requiring the termination of asparaginase. Failure to complete the entire asparaginase therapy course due to clinical hypersensitivity, subclinical hypersensitivity (i.e., silent inactivation), or other treatment-related toxicity is associated with poor ALL outcomes. Thus, it is critical to rapidly identify patients who develop clinical/subclinical hypersensitivity and switch these patients to an alternate asparaginase formulation. This article provides an overview of asparaginase hypersensitivity, identification and management of hypersensitivity and subclinical hypersensitivity, and issues related to switching patients to asparaginase Erwinia chrysanthemi following hypersensitivity reaction.

Pharmacokinetics-Based Integration of Multiple Doses of Intravenous Pegaspargase in a Pediatric Regimen for Adults With Newly Diagnosed Acute Lymphoblastic Leukemia

Purpose

Asparaginase treatment is standard in all pediatric acute lymphoblastic leukemia (ALL) regimens, whereas in adults, it is either excluded or administered for a shorter duration. Several adult ALL protocols are adapting pediatric regimens, but the optimal implementation of asparaginase is not well studied, considering its potential higher toxicity. We studied a pegaspargase dosing strategy based on its pharmacokinetic characteristics in adults.

Patients and Methods

Between 2004 and 2009, 51 adults age 18 to 57 years with newly diagnosed ALL were treated with a regimen adapted from a pediatric trial that included six doses of intravenous pegaspargase at 2,000 IU/m2 per dose. Intervals between doses were longer than 4 weeks and rationally synchronized with other chemotherapy drugs to prevent overlapping toxicities. Pegaspargase was administered with steroids to reduce hypersensitivity. Asparaginase-related toxicities were monitored after 173 pegaspargase doses.

Results

The most common grade 3/4 asparaginase-related toxicities were lengthy hyperbilirubinemia and transaminitis, occasionally resulting in subsequent treatment delays. All toxicities resolved spontaneously. Forty-five percent of patients were able to receive all six doses of pegaspargase, and 61% received ≥ three doses. In only 20% of patients, the drug was discontinued after pegaspargase-related serious toxicity. Ninety-six percent achieved complete remission, almost all within 4 weeks, and a low induction death rate was seen. Seven-year disease-free and overall survival were 58% and 51%, respectively.

Conclusion

Our dose and schedule of pegaspargase, based on its pharmacokinetics, and our detailed toxicity profile could be applied for safer adaptation of pediatric ALL protocols in adults.

L-asparaginase: an effective agent in the treatment of acute lymphoblastic leukemia

L-asparaginase (L-ASNase) is an enzyme used most effectively in the treatment of acute lymphoblastic leukemia (ALL) for more than 30 years. It catalyzes the hydrolysis of amino acid l-asparagine to aspartic acid and ammonia, which leads to cell death. Clinical trials have been conducted using L-ASNase in combination with other drugs and radiotherapy, which have led to great success in the treatment of ALL. Treatments consist of induction therapy and central nervous system therapy. The achievement of complete remission in patients is associated with a few side-effects of using L-asparaginase, including pancreatitis, coagulation abnormalities and allergic reactions. Sometimes tumor cells may develop resistance to L-ASNase. To overcome these difficulties, the drug is modified by pegylation or immobilization, and also treatment protocols can be modified to increase the efficiency of the drug.

Poly(ethylene glycol)-Prodrug Conjugates: Concept, Design, and Applications

Poly(ethylene glycol) (PEG) is the most widely used polymer in delivering anticancer drugs clinically. PEGylation (i.e., the covalent attachment of PEG) of peptides proteins, drugs, and bioactives is known to enhance the aqueous solubility of hydrophobic drugs, prolong circulation time, minimize nonspecific uptake, and achieve specific tumor targetability through the enhanced permeability and retention effect. Numerous PEG-based therapeutics have been developed, and several have received market approval. A vast amount of clinical experience has been gained which has helped to design PEG prodrug conjugates with improved therapeutic efficacy and reduced systemic toxicity. However, more efforts in designing PEG-based prodrug conjugates are anticipated. In light of this, the current paper highlights the synthetic advances in PEG prodrug conjugation methodologies with varied bioactive components of clinical relevance. In addition, this paper discusses FDA-approved PEGylated delivery systems, their intended clinical applications, and formulations under clinical trials.

Prevention and management of asparaginase/pegasparaginase-associated toxicities in adults and older adolescents: recommendations of an expert panel

The rapidly increasing use of pegasparaginase (pegASNase) in adults, after a half century of use of asparaginase (ASNase) in children, has prompted a need for guidelines in the management and prevention of toxicities of asparagine depletion in adults. Accordingly, an initial set of recommendations are provided herein. Major advantages of pegASNase are its 2-3-week duration of action, in contrast to less than 3 days with native ASNase, and the flexibility of intravenous or intramuscular administration of pegASNase and associated patient and physician convenience. The most frequent toxicities of both types of ASNase are hepatic and pancreatic, with pancreatitis being the most serious. Other toxicities are hypersensitivity reactions, thrombosis, nausea/vomiting, and fatigue. Whether or not the replacement of one dose of pegASNase for 6-9 doses of native ASNase can be achieved in adults with similar efficacy and acceptable toxicities to those achieved in children remains to be established.

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.

Anti-tumor activity and immunological modification of ribosome-inactivating protein (RIP) from Momordica charantia by covalent attachment of polyethylene glycol

Ribosome-inactivating proteins (RIPs) are a family of enzymes that depurinate rRNA and inhibit protein biosynthesis. Here we report the purification, apoptosis-inducing activity, and polyethylene glycol (PEG) modification of RIP from the bitter melon seeds. The protein has a homogenous N-terminal sequence of NAsp- Val-Ser-Phe-Arg. Moreover, the RIP displayed strong apoptosis-inducing activity and suppressed cancer cell growth. This might be attributed to the activation of caspases-3. To make it available for in vivo application, the immunogenicity of RIP was reduced by chemical modification with 20 kDa (mPEG)(2)-Lys-NHS. The inhibition activity of both PEGylated and non-PEGylated RIP against cancer cells was much stronger than against normal cells, and the antigenicity of PEGylated RIP was reduced significantly. Our results suggested that the PEGylated RIP might be potentially developed as anti-cancer drug.

L-Asparaginase: A Promising Chemotherapeutic Agent

This article comprises detailed information about L-asparaginase, encompassing topics such as microbial and plant sources of L-asparaginase, treatment with L-asparaginase, mechanism of action of L-asparaginase, production, purification, properties, expression and characteristics of l-asparaginase along with information about studies on the structure of L-asparaginase. Although L-asparaginase has been reviewed by Savitri and Azmi (2003), our effort has been to include recent and updated information about the enzyme covering new aspects such as structural modification and immobilization of L-asparaginase, recombinant L-asparaginase, resistance to L-asparaginase, methods of assay of L-asparagine and L-asparaginase activity using the biosensor approach, L-asparaginase activity in soil and the factors affecting it. Also, side-effects of L-asparaginase treatment in acute lymphoblastic leukemia (ALL) have been discussed in the current review. L-asparaginase has been and is still one of the most widely studied therapeutic enzymes by researchers and scientists worldwide.

CAG regimen enables relapsed or refractory T-cell acute lymphocytic leukemia patients to achieve complete remission: a report of six cases

Patients with either relapsed or refractory T-cell acute lymphocytic leukemia (T-ALL) are candidates for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Achieving complete remission (CR) in these patients is difficult but crucial for the success of allo-HSCT. In this study, we examined 6 relapsed or refractory T-ALL patients. In the patient group, 4 were male and 2 were female, with ages ranging from 15 to 57 years (median=29 years). All 6 patients presented with the nonmature T-ALL phenotype. Cytogenetically, only one had an i(7q) anomaly, whereas the remaining 5 cases had normal karyotypes. One of these patients had the MLL/AF9 fusion transcript, as shown by molecular study. After initial remission-induction therapy, two patients achieved CR, one showed a partial remission, and all relapsed soon. The other 3 cases failed the therapy. The CAG regimen (cytosine arabinoside 10 mg/m(2) subcutaneously every 12 hr, day 1-14; aclarubicin 5-7 mg/m(2) intravenously daily, day 1-8; and concurrent use of G-CSF 200 microg/m(2)/day subcutaneously) was devised originally for the treatment of relapsed acute myelogenous leukemia. After CAG therapy, all the T-ALL patients in our study achieved CR, indicating that the CAG regimen is beneficial to the treatment of relapsed or refractory T-ALL. The efficacy of CR-induction in T-ALL patients and the adverse effects of the CAG regimen need to be further studied.

Correlation between high vascular endothelial growth factor-A serum levels and treatment outcome in patients with standard-risk acute lymphoblastic leukemia: a report from Children's Oncology Group Study CCG-1962

PURPOSE

Many molecular pathways, including cell cycle control, angiogenesis, and drug resistance, mediate tumor growth and survival. Vascular endothelial growth factor-A (VEGF-A) serum levels <40 and >100 pg/mL have been associated with good and poor prognoses, respectively.

EXPERIMENTAL DESIGN

The hypothesis was that serum VEGF-A levels in standard-risk acute lymphoblastic leukemia pediatric patients at induction are predictive of event-free survival (EFS). One hundred seventeen patients were entered in CCG-1962 study and randomized into the native and polyethylene glycolated asparaginase arms. VEGF-A levels were quantified by an ELISA assay.

RESULTS

All patients had a decrease in VEGF-A levels by day 14 of induction, but they later dichotomized; EFS group levels remained low and event group levels increased. A correlation exists between high VEGF-A levels at entry to induction and time to event. Moreover, 6-year EFS patients have lower end of induction VEGF-A levels (28 +/- 6 pg/mL) than event patients (>100 pg/mL; P < 0.01). Kaplan-Meier curves using various VEGF-A values were produced; with < or =30 at entry into induction (day 0) and < or =60 pg/mL at the end of induction (day 28), patients with low VEGF-A levels had superior EFS (P < 1e-4). Furthermore, patients who had an increase in VEGF-A during induction (DeltaVEGF-positive, days 0-28) were more likely to have an event (P < 1e-4). Bifurcation by asparaginase treatment arm did not alter these results.

CONCLUSIONS

These observations strongly support that high VEGF-A levels in induction are an asparaginase treatment-independent predictive marker for EFS. Hence, an anti-VEGF-A therapy should be tested in acute lymphoblastic leukemia.

Pharmacodynamics and safety of intravenous pegaspargase during remission induction in adults aged 55 years or younger with newly diagnosed acute lymphoblastic leukemia

In contrast to that in children, pharmacokinetic, pharmacodynamic, and safety information on pegaspargase in adults is very limited. We administered a single intravenous dose of pegaspargase (2000 IU/m2) as part of a standard frontline induction regimen to 25 adults with newly diagnosed acute lymphoblastic leukemia (ALL), and obtained serum samples on several time points. The population mean peak serum concentration of asparaginase enzymatic activity was 1 IU/mL, the elimination half-life was 7 days, and the volume of distribution was 2.43 L/m2. After the single dose, asparagine deamination was complete in all patients after 2 hours, and in 100%, 81%, and 44% on days 14, 21, and 28, respectively. A pharmocodynamic correlation model showed minimal enzymatic activity of 0.2 IU/mL for optimal asparagine depletion. The kinetic posthoc analyses demonstrated enzymatic activity for 3 weeks or more. One patient developed neutralizing antiasparaginase antibodies on day 22 after administration. Pegaspargase was well tolerated, with few grade 3/4 side effects. No allergic reactions or pancreatitis were observed. In adults aged 55 years or younger, pegaspargase produces a long duration of asparagine depletion and can be given intravenously, with a safety profile that is similar to equivalent multiple doses of intramuscular Escherichia coli asparaginase.

Emerging therapeutic options for Philadelphia-positive acute lymphocytic leukemia

Acute lymphocytic leukemia (ALL) is a heterogeneous group of disorders that are associated with a cure rate of > 80% in children. The prognosis in adults is considerably inferior, with age, disease bulk, leukemia karyotype and immune phenotype being prognostically relevant. Adult ALL treatment programs include induction, intensified consolidation and maintenance phases with CNS prophylaxis. The addition of imatinib in patients with BCR-ABL-positive ALL has improved the prognosis of this subgroup, but their survival is still poor. Initial data on the second-generation BCR-ABL inhibitors, dasatinib and nilotinib, indicate a potentially greater efficacy than imatinib, but the improvement is likely to be modest. The overall efforts in terms of developmental therapeutics in ALL are very modest and not in keeping with the urgent need for improvement. Most agents being investigated have mechanisms of action similar to those of existing agents for ALL therapy and thus represent modest opportunities to improve results. Of such agents, data on BCR-ABL inhibitors, sphingosomal vincristine, pemetrexed, talotrexin, annamycin and ABT-751 are reviewed.

Pharmacokinetic consequences of pegylation

Pegylation, generally described as the molecular attachment of polyethylene glycols (PEGs) with different molecular weights to active drug molecules or surface treatment of drug-bearing particles with PEGs, is one of the most promising and extensively studied strategies with the goal of improving the pharmacokinetic behavior of the therapeutic drugs. A variety of PEGs, both linear and branched, with different molecular weights have been exploited successfully for use in this procedure in the form of reactive PEG species. Both reversible and irreversible PEG-drug conjugates have been prepared with relative advantages/disadvantages. The main pharmacokinetic outcomes of pegylation are summarized as changes occurring in overall circulation life-span, tissue distribution pattern, and elimination pathway of the parent drug/particle. Based on these favorable pharmacokinetic consequences leading to desired pharmacodynamic outcomes, a variety of proteins/peptides as well as small molecule drugs have been pegylated and evaluated successfully. Also a number of corresponding products have been approved by the U.S. FDA for specific clinical indications and some others are underway. In this article, the chemistry, rationale, strategies, pharmacokinetic outcomes, and therapeutic possibilities of pegylated drugs are reviewed with pharmacokinetic aspects presented with more details.

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.

Emerging drugs for adult acute lymphoblastic leukaemia

Although most patients with adult acute lymphoblastic leukaemia (ALL) can achieve a remission when treated with conventional, DNA-damaging chemotherapy, in more than half of all cases the disease relapses and ultimately results in death. Therefore, there is a substantial need for new antileukaemic drugs. Recent advances in the understanding of the molecular alterations in ALL have lead to the identification of new targets and the arrival of molecular-targeted therapies in the clinical setting. The prototype for this approach is the treatment of Philadelphia chromosome-positive ALL with imatinib mesylate. Here, the targeting of a molecular abnormality--inhibition of BCR-ABL tyrosine kinase--has turned a very poor-prognosis disease into one in which promising results are achieved. Promising new therapies are under development that target various goals, including the NOTCH signalling pathway, purine nucleoside phosphorylase activity, mammalian target of rapamycin and tyrosine kinase. This review outlines recent advances in the development of emerging drugs for the treatment of adult ALL. The recent advances in the understanding of the biology and pathogenesis of ALL have helped to determine prognosis and to plan the therapy of adult patients with ALL. Still, despite improved complete remission rates of 65-90% with current therapy, only 20-40% of patients can be considered cured. New therapeutic alternatives are needed to improve these results. With a better understanding of the disease, more target-specific therapies could be designed. The aim of this review is to highlight new pharmacotherapies and those emerging drug treatments for patients with adult ALL.

Phase II study of sphingosomal vincristine in patients with recurrent or refractory adult acute lymphocytic leukemia

BACKGROUND

Outcomes with salvage therapy for patients with recurrent or refractory acute lymphocytic leukemia (ALL) are poor, with complete response (CR) rates reported to be 20-30% and a median survival ranging from 2-6 months. New agents are needed to reduce the recurrence rate after frontline chemotherapy. Vincristine is an important component of ALL therapy. In animal models, the encapsulation of vincristine into sphingomyelin liposomes or "sphingosomes" for injection (SV) has improved efficacy compared with conventional vincristine.

METHODS

A Phase II clinical trial of single-agent SV given at a dose of 2.0 mg/m2 every 2 weeks was conducted in patients with recurrent or refractory ALL. Approximately half of the 16 patients who received SV had a first CR duration of less than 1 year, 19% had failed standard induction chemotherapy, and 50% had Philadelphia chromosome-positive disease. SV was the first salvage attempt in 69% of the patients.

RESULTS

The overall response rate in the 14 evaluable patients was 14% (1 CR and 1 partial response). Five patients (36%) had transient reductions in bone marrow leukemia infiltrate with subsequent regrowth of the leukemia between SV infusions. Toxicity with limited treatment (median number of doses was two; range, one to five doses) was minimal with expected peripheral neuropathy.

CONCLUSIONS

Further study of SV in patients with ALL is warranted. A Phase I-II clinical trial of weekly SV with pulse dexamethasone currently is ongoing.

Adult acute lymphoblastic leukemia

Much progress has been made in understanding the biology of and therapy for acute lymphoblastic leukemia (ALL). This progress has translated into the recognition of several subgroups of ALL and the institution of risk-adapted therapies. New therapies are emerging based on the definition of specific cytogenetic-molecular abnormalities. Changes in the pathologic classification of ALL have led to therapeutic consequences. Adaptation of successful treatment strategies in children with ALL has resulted in similar complete remission rates in adults. Prognosis has Improved especially in mature B-cell ALL and T-cell lineage ALL. However, regardless of ALL subgroup, long-term survival in adults is still inferior to that in children. Development of new drugs and agents tailored to subset-specific cytogenetic-molecular characteristics is vital to the therapeutic success in adult ALL.

Adult acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) in adults is a relatively rare neoplasm with a curability rate around 30% at 5 years. This consideration makes it imperative to dissect further the biological mechanisms of disease, in order to selectively implement an hitherto unsatisfactory success rate. The recognition of discrete ALL subtypes (some of which deserve specific therapeutic approaches, like T-lineage ALL (T-ALL) and mature B-lineage ALL (B-ALL)) is possible through an accurate combination of cytomorphology, immunophenotytpe and cytogenetic assays and has been a major result of clinical research studies conducted over the past 20 years. Two-three major prognostic groups are now easily identifiable, with a survival probability ranging from <10 to 20% (Philadelphia-positive ALL) to about 50-60% (low-risk T-ALL and selected patients with B-lineage ALL). These issues are extensively reviewed and form the basis of current knowledge. The second major point relates to the emerging importance of studies that reveal a dysregulated gene activity and its clinical counterpart. It is now clear that prognostication is a complex matter ranging from patient-related issues to cytogenetics to molecular biology, including the evaluation of minimal residual disease (MRD) and possibly gene array tests. On these bases, the role of a correct, highly personalised therapeutic choice will soon become fundamental. Therapeutic progress may be obtainable through a careful integration of chemotherapy, stem cell transplantation, and the new targeted treatments with highly specific metabolic inhibitors and humanised monoclonal antibodies.

PEGylation Confers Greatly Extended Half-Life and Attenuated Immunogenicity to Recombinant Methioninase in Primates

Methionine depletion by recombinant methioninase (rMETase) has been demonstrated previously to be highly effective in tumor-bearing mouse models. However, the therapeutic potential of rMETase has been limited by its short plasma half-life and immunologic effects, including high antibody production in mice and monkeys and anaphylactic reactions in monkeys. To overcome these limits of rMETase, the enzyme has been coupled to methoxypolyethylene glycol succinimidyl glutarate (MEGC-PEG-5000). In this study, we evaluated the pharmacokinetics, antigenicity and toxicity of MEGC-PEG-rMETase in Macaca fascicularis monkeys using an escalating-dose strategy. Dose ranging studies at 1,000, 4,000, and 8,000 units/kg i.v. determined that a single dose of 4,000 units/kg was sufficient to reduce plasma methionine to <5 micromol/L for 12 hours. Pharmacokinetic analysis with the single 4,000 units/kg dose showed that MEGC-PEG-rMETase holoenzyme activity was eliminated with a biological half-life of 1.3 hours, and the MEGC-PEG-rMETase apoenzyme was eliminated with a biological half-life of 90 hours, an approximately 36-fold increase compared with non-PEGylated rMETase. A single dose at 2,000 units/kg of MEGC-PEG-rMETase resulted in an apoenzyme half-life of 143 hours. A seven-day i.v. administration of 4,000 units/kg every 12 hours resulted in a steady-state depletion of plasma methionine to <5 micromol/L. The only manifest toxicity was decreased food intake and slight weight loss. Red cell values and hemoglobin declined transiently during treatment but recovered after cessation of treatment. Subsequent challenges on days 29, 50 and, 71 did not result in any immunologic reactions. This result is in contrast to non-PEGylated rMETase, which elicited anaphylactic reactions in monkeys. Anti-MEGC-PEG-rMETase antibodies (at 10(-2)) were found on day 29, and these increased to 10(-3) to 10(4) on day 71, 100 to 1,000-fold less than antibodies elicited by naked rMETase. Although anti-MEGC-PEG-rMETase antibodies were produced, no neutralizing antibody was identified, and each challenge dose was effective in depleting plasma methionine levels. The results of the present study demonstrate that PEGylation greatly prolongs serum half-life of the rMETase apoenzyme and eliminated anaphylactic reactions. The results indicate a profile with respect to serum half-life, toxicity, and antigenicity that suggest clinical potential of MEGC-PEG-rMETase.

Circulating Half-Life of PEGylated Recombinant Methioninase Holoenzyme Is Highly Dose Dependent on Cofactor Pyridoxal-5′-Phosphate

Recombinant methioninase (rMETase) has been shown to target the elevated methionine (MET) dependence of tumor cells and arrest their growth as well as make tumors more sensitive to standard chemotherapy agents. Polyethylene glycol (PEG)-modified rMETase (PEG-rMETase) has reduced antigenicity compared with unmodified rMETase. However, PEG-rMETase has a limited active circulating half-life due to rapid in vivo dissociation of its cofactor pyridoxal-5'-phosphate (PLP), a surprising finding, because PLP is tightly bound to PEG-rMETase in buffer. The question asked in the current study was on the effect of increasing doses of PLP to extend the circulating half-life of active PEG-rMETase holoenzyme in vivo. rMETase was conjugated with methoxypolyethylene glycol succinimidyl glutarate 5000 (MEGC-PEG). Miniosmotic pumps containing various concentrations of PLP were implanted in BALB-C mice. PLP-infused mice were then injected with a single dose of 4000 or 8000 units/kg PEG-rMETase. Mice infused with 5, 50, 100, 200, and 500 mg/ml PLP-containing miniosmotic pumps increased plasma PLP to 7, 24, 34, 60, and 95 microm, respectively, from the PLP baseline of 0.3 microm. PLP increased the half-life of MEGC-PEG-rMETase holoenzyme in a dose-dependent manner. Pumps containing 500 mg/ml PLP increased the half-life of MEGC-PEG-rMETase holoenzyme 4.5-fold from 1.5 to 7 h. Infused PLP did not extend the half-life of MEGC-PEG-rMETase apoenzyme. With a dose of 4000 units/kg MEGC-PEG-rMETase in the mice infused with 5, 50, 200, and 500 mg/ml PLP, plasma MET was depleted from 50 microm to < or = 5 microm for 8, 24, 72, and 72 h, respectively. Thus, PLP infusion could extend the period of MET depletion by MEGC-PEG-rMETase by approximately 10-fold in a dose-dependent manner. The mice given 8000 units/kg MEGC-PEG-rMETase showed a similar plasma MET depletion time course, indicating that the limiting factor for MEGC-PEG-rMETase-mediated MET depletion in vivo was PLP. The extended time of MET depletion by MEGC-PEG-rMETase was due to the maintenance of active MEGC-PEG-rMETase holoenzyme by infused PLP. The infused PLP either bound to apo-MEGC-PEG-rMETase and/or inhibited dissociation of PLP from holo-PEG-rMETase, thereby maintaining the holoenzyme form of MEGC-PEG-rMETase in vivo. The combination of MEGC-PEG-rMETase treatment with PLP infusion suggests an effective clinical strategy for long-term MET depletion to arrest cancer growth.

Protein carboxyl amidation increases the potential extent of protein polyethylene glycol conjugation

Chemical coupling of polyethylene glycol (PEG) to therapeutic proteins reduces their immunogenicity and prolongs their circulating half-life. The limitation of this approach is the number and distribution of sites on proteins available for PEGylation (the N terminus and the -amino group of lysines). To increase the extent of PEGylation, we have developed a method to increase the number of PEGylation sites in a model protein, recombinant methionine alpha,gamma-lyase (recombinant methioninase; rMETase), an enzyme cancer therapeutic cloned from Pseudomonas putida. rMETase was first PEGylated with methoxypolyethylene glycol succinimidyl glutarate-5000 with a molar ratio of PEG:rMETase of 15:1. The carboxyl groups of the initially PEGylated protein were then conjugated with diaminobutane, resulting in carboxyl amidation. This reaction was catalyzed by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, a water-soluble carbodiimide. The steric hindrance provided by the PEG chains already coupled to the protein prevented cross-linking between rMETase molecules during the carboxyl amidation reaction. The carboxyl-amidated PEGylated rMETase was hyper-PEGylated at a molar ratio of PEG to PEG-rMETase of 60:1. Biochemical analysis indicated that 13 PEG chains were coupled to each subunit of rMETase after hyper-PEGylation compared with 6-8 PEG chains attached to the non-carboxyl-amidated PEG-rMETase. Approximately 15-20% of the non-PEGylated rMETase activity was retained in the hyper-PEGylated molecule. Immunogenicity of the hyper-PEG-rMETase was significantly reduced relative to PEG-rMETase and rMETase. Initial results suggest that hyper-PEGylation may become a new strategy for PEGylation of protein biologics.

The biology and therapy of adult acute lymphoblastic leukemia

BACKGROUND

Much progress has been made in understanding the biology of acute lymphoblastic leukemia (ALL). This has translated into the recognition of several subgroups of ALL and the institution of risk-adapted therapies. New therapies are emerging based on the definition of specific cytogenetic-molecular abnormalities.

METHODS

A review from the English literature, including original articles and related reviews from Medline (Pubmed) and abstracts based on publication of meeting material, was performed.

RESULTS

Changes in the pathologic classification of ALL have led to therapeutic consequences. Adaptation of successful treatment strategies in children with ALL has resulted in similar complete response rates in adults. Prognosis has especially improved in mature-B-cell and T-lineage ALL. The role of tyrosine kinase inhibitors in Philadelphia chromosome-positive ALL was evaluated in the current study. However, regardless of the ALL subgroup, long-term survival of adults is still inferior to that in children.

CONCLUSIONS

Intense clinical and laboratory research is attempting to close the gap in outcome between children and adults with ALL. Investigations are focusing on 1) refinement of the basic treatment stratagem of induction, consolidation, and maintenance; 2) expansion of risk-based, subgroup-oriented therapies; 3) assessment of minimal residual disease, its impact on disease recurrence, and its practical implications in clinical practice; 4) salvage strategies; 5) the role of stem cell transplantation in ALL; and 6) the development of new drugs based on a better understanding of disease biology.

New agents in the treatment of acute lymphocytic leukaemia

The overall prognosis of adult patients with acute lymphocytic leukaemia (ALL) has improved significantly over the past few decades. Combined modality strategies (e.g. chemotherapy used with targeted therapies such as monoclonal antibodies or tyrosine kinase inhibitors) may improve long-term disease-free survival. Still, most patients succumb to complications of disease progression, with current long-term disease-free survival rates of 30-45% overall. Thus, either new strategies or refinements of old ones are needed to improve the long-term prognosis. An increasing number of unique active new chemotherapeutic and biological agents are available for study. This chapter reviews new agents with the potential to be incorporated into therapeutic strategies for the treatment of ALL.

A single, high dose of idarubicin combined with cytarabine as induction therapy for adult patients with recurrent or refractory acute lymphoblastic leukemia

BACKGROUND

The majority of adult patients who are treated for lymphoblastic disease will either develop recurrent disease or will be refractory to their initial therapy. One option for patients with recurrent/refractory disease is to administer a reinduction regimen that employs a dose-intense combination of anthracycline and cytarabine. These salvage regimens are relatively distinct from the traditional vincristine/prednisone-based programs that are used typically as primary induction therapy. The authors studied a regimen that contained high-dose cytarabine and a single high dose of idarubicin as salvage induction therapy for patients with recurrent or refractory lymphoblastic disease.

METHODS

Twenty-nine previously treated adult patients with recurrent or refractory acute lymphoblastic leukemia were treated with a new intensive regimen. Eight patients had primary refractory disease. Twenty-one patients had recurrent disease, and 16 of these patients developed recurrent disease while they were still receiving their primary therapy. The treatment regimen consisted of cytarabine 3.0 g/m(2) by 3-hour infusion daily for 5 days and idarubicin 40 mg/m(2) given as a single dose on Day 3. Filgrastim (granulocyte-colony stimulating factor) 5 microg/kg administered subcutaneously every 12 hours was started on Day 7 and was continued until the absolute neutrophil count was > 5000/microL. Response was assessed using standard criteria.

RESULTS

There were 11 complete responses (38%; 95% confidence interval, 20-56%). Four patients subsequently underwent allogeneic bone marrow transplantation. Moderate but acceptable toxicity was observed given the severely myelosuppressive nature of the regimen. There was only one treatment-related death (3%). Two patients, both with significant prior exposure to anthracyclines, suffered reductions in left ventricular function to the 20-30% range during episodes of severe systemic infection. After recovery from infection, the ejection fraction in one patient improved to 50%.

CONCLUSIONS

The authors conclude that this regimen has moderate activity and a relatively low incidence of mortality for this high-risk group of patients. This regimen may be most suitable for patients who can undergo potentially curative allogeneic bone marrow transplantation if they achieve a complete response.

Chemotherapy-induced palmar-plantar erythrodysesthesia syndrome--recall following different chemotherapy agents

Radiation recall is a phenomenon commonly seen in patients receiving chemotherapy treatment who have previously been exposed to radiation. A phenomenon not clearly described is that of a side effect induced by one chemotherapy agent and later recalled when the patient is given a different chemotherapy regimen. Troxacitabine is an anti-leukemic agent which can be associated with palmar-plantar erythrodysesthesia syndrome (PPES). Here, we report six cases of troxacitabine-induced PPES that was later recalled by various chemotherapy regimens. The recall PPES was mild to moderate and self-limiting in all cases. All of these patients recovered from the recall side effects with minimal medical intervention. We conclude that a recall phenomenon similar to that described after radiotherapy might occur after certain chemotherapy agents. This phenomenon should be considered when evaluating toxicity from chemotherapy, particularly when using new and investigational agents.

Phase II study of troxacitabine, a novel dioxolane nucleoside analog, in patients with refractory leukemia

PURPOSE

To investigate the activity of a novel dioxolane L-nucleoside analog, troxacitabine (L-(-)-OddC, BCH-4556), in patients with refractory leukemia.

PATIENTS AND METHODS

Study participants were patients with refractory or relapsed acute myeloid (AML) or lymphocytic (ALL) leukemia, myelodysplastic syndromes (MDS), or chronic myelogenous leukemia in blastic phase (CML-BP). Troxacitabine was provided as an intravenous infusion for more than 30 minutes daily for 5 days at a dose of 8.0 mg/m(2)/d (40 mg/m(2) per course). Courses were given every 3 to 4 weeks according to antileukemic efficacy.

RESULTS

Forty-two patients (AML, 18 patients; MDS, one patient; ALL, six patients; CML-BP, 17 patients) were treated. Median age was 51 years (range, 23 to 80 years); 22 patients were male. Stomatitis was the most significant adverse event, with three patients (7%) and two patients (5%), respectively, experiencing grade 3 or 4 toxicity. Ten patients (24%) had grade 3 hand-foot syndrome, and two patients (5%) had grade 3 skin rash. One patient (2%) had grade 3 fatigue and anorexia. Marrow hypoplasia occurred between days 14 and 28 in 12 (75%) of 16 assessable patients with AML. Two complete remissions and one partial remission (18%) were observed in 16 assessable patients with AML. None of six patients with ALL responded. Six (37%) of 16 assessable patients with CML-BP experienced a return to chronic-phase disease.

CONCLUSION

Troxacitabine has significant antileukemic activity in patients with AML and CML-BP.

Antitumor activity of L-asparaginase from Thermus thermophilus

L-asparaginase (EC 3.5.1.1) was purified to homogeneity from Thermus thermophilus. The apparent molecular mass of L-asparaginase was found to be 33 kDa by SDS-PAGE, whereas by Sephacryl S-300 superfine column it was found to be 200 kDa, indicating that the enzyme in the native stage acts as hexamer. It is a thermostable enzyme and keeps all of its activity at 80 degrees C for 10 min. The antiproliferative activity of the purified L-asparaginase from T. thermiphilus was tested against the following human cell lines: K-562 (chronic myelogenous leukemia), Raji (Burkitt's lymphoma), SK-N-MC (primitive neuroectodermal tumor), HeLa (cervical cancer), BT20 and MCF7 (breast cancers), HT-29 (human colon cancer), and OAW-42 (ovarian cancer). The antiproliferative activity of T. thermophilus enzyme was compared with Erwinase, the commercially available L-asparaginase from Erwinia corotovora. The potency difference between the two L-asparaginases was greater in HeLa and SK-N-MC than in other cell lines. The fact that L-asparaginase from T. thermophilus does not hydrolyse L-glutamine makes it advantageous for future clinical trials.

Salvage therapy for refractory or relapsed acute lymphocytic leukemia

The overall prognosis for patients with relapsed or refractory adult ALL remains poor. Further insight into the biology of ALL is required, and novel therapeutic agents are needed to counter mechanisms of resistance. A palliative approach to the management of multiply relapsed or refractory ALL should be supplanted by enrollment into clinic trials to promote drug discovery. Monitoring of minimal residual disease may allow an earlier intervention before overt clinical relapse and improve outcome; prospective studies are needed. Attainment of a second or later CR should be followed by allogeneic BMT when feasible owing to the paucity of long-term survivors with salvage chemotherapy alone.