Toxicity, pharmacology and feasibility of administration of PEG-L-asparaginase as consolidation therapy in patients undergoing bone marrow transplantation for acute lymphoblastic leukemia

An Engineered Arginase FC Protein Inhibits Tumor Growth In Vitro and In Vivo

Arginine is a semiessential amino acid required for the growth of melanoma and hepatocellular carcinoma, and the enzymatic removal of arginine by pegylated arginine deiminase (ADI) or arginase is being tested clinically. Here, we report a genetically engineered arginase FC fusion protein exhibiting a prolonged half-life and enhanced efficacy. The use of this enzyme to treat different tumor lines both inhibited cell proliferation and impaired cellular migration in vitro and in vivo. Our data reinforce the hypothesis that nutritional depletion is a key strategy for cancer treatment.

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.

Activity of vincristine, L-ASP, and dexamethasone against acute lymphoblastic leukemia is enhanced by the BH3-mimetic ABT-737 in vitro and in vivo

Defects in apoptosis signaling contribute to poor outcome in pediatric acute lymphoblastic leukemia (ALL), and overexpression of antiapoptotic Bcl-2 (Bcl-2 and Bcl-X(L)) family proteins has been observed in ALL. ABT-737 is a small-molecule BH3-mimetic that inhibits the antiapoptotic Bcl-2 family proteins. We evaluated the cytotoxicity of ABT-737 in combination with vincristine, dexamethasone, and L-asparaginase (VXL) in 7 ALL cell lines. Multilog synergistic cytotoxicity was observed in all 7 cell lines with ABT-737 plus L-asparaginase or vincristine, and in 5 of 7 cell lines with ABT-737 plus dexamethasone or VXL. In leukemia cells, but not in normal lymphocytes, ABT-737 plus L-asparaginase induced greater mitochondrial depolarization (JC-1 staining); mitochondrial cytochrome c release; activation of Bax, Bid, and caspases (immunoblotting); and eventually apoptosis (annexin V staining) than did either drug alone. In mouse xenografts derived from patients with ALL at diagnosis (ALL-7) or at relapse (ALL-19), event-free survival (EFS) was significantly enhanced with ABT-737 plus VXL relative to VXL or ABT-737 alone (P </= .02). Thus, ABT-737 synergistically enhanced VXL cytotoxicity in ALL cell lines via a mitochondrial death pathway and enhanced EFS in VXL-treated mice bearing ALL xenografts. Combining VXL with a BH3-mimetic warrants clinical investigation in ALL at relapse and potentially in chemotherapy-resistant ALL subgroups.

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.

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

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

L-asparaginase-provoked seizures as singular expression of central nervous toxicity

Patients treated with L-asparaginase may present with hemorrhagic and thrombotic cerebrovascular events. This syndrome generally occurs after a few weeks of therapy and may occur after L-asparaginase therapy is completed. Complications appear to result from depletion of plasma proteins involved in coagulation and fibrinolysis. Seizures are uncommon symptoms, and are always caused by cerebrovascular events. We report a case of seizure associated with L-asparaginase therapy but no evidence of hemorrhagic or thrombotic cerebrovascular events.