L-asparaginase treatment reduces the anticoagulant potential of the protein C system without affecting vitamin K-dependent carboxylation

Cancer Therapy-Associated Thrombosis

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Osteonecrosis in pediatric cancer survivors: Epidemiology, risk factors, and treatment

Several treatment regimens for childhood malignancies have been associated with the development of osteonecrosis, including radiation therapy, glucocorticoid medications, immunotherapy (including anti-angiogenic agents), and several chemotherapeutic agents. Adolescents older than 10 years are at greatest risk of developing osteonecrosis within 1 year of initiating therapy. Screening with magnetic resonance imaging in this high-risk population may be a useful method for detecting osteonecrosis. Surgery may be required for lesions that have progressed substantially despite nonoperative interventions.

L-asparaginase as a critical component to combat Acute Lymphoblastic Leukaemia (ALL): A novel approach to target ALL

L-asparaginase, an anti-leukaemic drug that has been approved for clinical use for many years in the treatment of childhood Acute Lymphoblastic Leukaemia (ALL), is obtained from bacterial origin (Escherichia coli and Erwinia carotovora). The efficacy of L-asparaginase has been discussed for the past 40 years, and an ideal substitute for the enzyme has not yet been developed. The early clearance from plasma (short half-life) and requirement for multiple administrations and hence frequent physician visits make the overall treatment cost quite high. In addition, a high rate of allergic reactions in patients receiving treatment with the enzyme isolated from bacterial sources make its clinical application challenging. For these reasons, various attempts are being made to overcome these barriers. Therefore, the present article reviews studies focused on seeking substitutes for L-asparaginase through alternative sources including bacteria, fungi, actinomycetes, algae and plants to overcome these limitations. In addition, the role of chemical modifications and protein engineering approaches to enhance the drug's efficacy are also discussed. Moreover, an overview has also been provided in the current review regarding the contradiction among various researchers regarding the significance of the enzyme's glutaminase activity.

Haemostatic alterations induced by treatment with asparaginases and clinical consequences

The benefit of asparaginase for treating acute lymphoid leukaemia (ALL) has been well established. Native asparaginase derives from Escherichia coli (colaspase) or Erwinia chrysanthemi (crisantaspase); in a third preparation, colaspase is pegylated. Depletion of asparagine leads to decreased synthesis of procoagulant, anticoagulant, and fibrinolytic proteins, with resultant hypercoagulability and greater risk of venous thromboembolism (VTE). Colaspase and crisantaspase are not dose-equivalent, with crisantaspase displaying haemostatic toxicity only at dosages much higher and administered more frequently than those of colaspase. Cerebral venous thrombosis and pulmonary embolism are two life-endangering manifestations that occur during treatment with asparaginase particularly in children and in adults with ALL, respectively. Approximately one-third of VTEs are located in the upper extremities and are central venous line-related. Other risk factors are longer duration of asparaginase treatment and concomitant use of prednisone, anthracyclines, and oral contraceptives. The risk associated with inherited thrombophilia is uncertain but is clearly enhanced by other risk factors or by the use of prednisone. VTE prevention with fresh frozen plasma is not recommended; the efficacy of antithrombin (AT) concentrates has occasionally been reported, but these reports should be confirmed by proper studies, and AT should not be routinely employed. Therapeutic or prophylactic heparin doses are only partially effective, and direct thrombin or factor Xa inhibitors could play significant roles in the near future.

The coagulopathy and thrombotic risk associated with L-asparaginase treatment in adults with acute lymphoblastic leukaemia

The dramatic improvements seen in the outcome of paediatric patients with acute lymphoblastic leukaemia (ALL) have led to increasing incorporation of L-asparaginase (L-Asp) in adult treatment protocols. However, its use is associated with a disruption in the physiological balance between haemostatic and anticoagulant pathways, with the predominant clinical manifestation being thrombosis. Although L-Asp therapy is known to be associated with an acquired deficiency of antithrombin (AT), the concurrent depletion of fibrinogen and other haemostatic proteins means that the precise mechanism of thrombosis remains to be defined. In vitro coagulation assays are often prolonged but thrombosis rather than haemorrhage is the primary concern. Management of thrombotic events in these patients is based around agents that rely on AT for their anticoagulant effect, even though it is usually depleted. There is currently only limited evidence supporting the use of AT concentrates in either primary prevention or management following an established event. Evidence-based guidelines for prevention and management strategies are lacking.

Thrombosis and acute lymphoblastic leukaemia

Venous thrombosis is more frequent in patients treated for acute lymphoblastic leukaemia (ALL) than other malignancies and has distinctive causes, clinical features and remedies. The reported incidence varies from 1% to 36%, depending on the chemotherapy protocol and whether the reported cases are symptomatic or detected on screening radiography. The risk is thought to arise from increased thrombin generation at diagnosis combined with reduced thrombin inhibitory capacity due to depletion of circulating anti-thrombin (AT) by asparaginase. A number of patient and treatment variables have been reported to influence the risk of thrombosis including hereditary thrombophilia, early insertion of central venous catheters and exposure to a combination of steroids and asparaginase during induction. Erwinia asparaginase is associated with a lower risk of thrombosis compared with Escherichia coli asparaginase. The majority of symptomatic thromboses are related to central venous catheters and involve the upper venous system. Central nervous system thrombosis involving the cerebral venous sinuses is a unique feature of asparaginase-related thrombosis and is reported to occur in 1-3% of patients. Conclusive evidence to support the use of anti-coagulant treatment or AT concentrates for primary prevention is lacking, as is evidence for the efficacy of AT concentrates in the management of established thrombosis. Preventative strategies are hampered by conflicting data on factors that would enable identification of those at highest risk of thrombosis.

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.

Thrombotic complications in childhood acute lymphoblastic leukemia: a meta-analysis of 17 prospective studies comprising 1752 pediatric patients

The risk of thrombosis in children with acute lymphoblastic leukemia (ALL) reportedly ranges between 1% and 37%. Epidemiologic studies have usually been hampered by small numbers, making accurate estimates of thrombosis risk in ALL patients very difficult. The aim of this study was to better estimate the frequency of this complication and to define how the disease, its treatment, and the host contribute to its occurrence. We made an attempt to combine and analyze all published data on the association between pediatric ALL and thrombosis, by using a meta-analytic method. The rate of thrombosis in 1752 children from 17 prospective studies was 5.2% (95% CI: 4.2-6.4). The risk varies depending on several factors. Most of the events occurred during the induction phase of therapy. Lower doses of asparaginase (ASP) for long periods were associated with the highest incidence of thrombosis, as were anthracyclines and prednisone (instead of dexamethasone). The presence of central lines and of thrombophilic genetic abnormalities also appeared to be frequently associated with thrombosis. In conclusion, the overall thrombotic risk in ALL children was significant, and the subgroup analysis was able to identify high-risk individuals, a finding that will hopefully guide future prospective studies aimed at decreasing this risk.

Thrombosis in children with acute lymphoblastic leukemia

At diagnosis, there is evidence of increased thrombin generation in children with acute lymphoblastic leukemia (ALL), the etiology of which is unclear. However, thromboembolism (TE) in children with ALL is most commonly reported after the initiation of antileukemic therapy indicating a possible interaction of the disease and therapy. Antileukemic therapy influences the haemostatic system either by direct effect of the chemotherapeutic agents or indirectly through the effect of supportive care, e.g. central venous line (CVL) or infectious complications secondary to immunosuppression. Asparaginase and steroids are shown to induce hypercoagulable state by suppression of natural anticoagulants, especially AT and plasminogen, and by elevations in F VIII/vWF complex, respectively. In addition, steroid therapy causes hypofibrinolytic state by dose-dependent increase in plasminogen activator inhibitor 1 (PAI-1) levels. Combination of these effects coupled with increased thrombin generation may be responsible for the increased incidence of TE observed with concomitant administration of asparaginase and steroids. Further studies to delineate the mechanism of increased thrombin in generation children with ALL and effects of various chemotherapeutic agents, in isolation and in combination, on haemostatic system are needed.

Thrombosis related to the use of L-asparaginase in adults with acute lymphoblastic leukemia: a need to consider coagulation monitoring and clotting factor replacement

L-asparaginase (L-asp) has become an important component of combination chemotherapy for acute lymphoblastic leukemia (ALL). However, L-asp can produce depletions in many of the clotting factors with an associated risk for thrombosis and hemorrhage. Three consecutive patients seen at the Mayo Clinic with L-asp related thrombosis are described and an in-depth review of the literature is provided. Two of the 3 patients developed central nervous system (CNS) complications with evidence of thrombosis and hemorrhagic infarction. Two of the patients also developed extensive upper extremity thrombosis. The results of comprehensive hemostatic surveys showed marked abnormalities in all 3 patients. Many of the thrombotic complications related to L-asp involve the CNS, as illustrated in 2 of our patients. These patients should be treated aggressively since full recovery is possible. The precise cause of thrombosis is yet to be determined but is likely multifactorial. The optimal treatment and prevention of thrombosis in this group of patients remains poorly defined.

Effects of Erwinia-asparaginase on the coagulation system

L-Asparaginase treatment during induction therapy in acute lymphoblastic leukaemia (ALL) is known to be frequently complicated by thromboembolic events. It was recently suggested that L-asparaginase derived from Erwinia chrysanthemi alters the coagulation system less severely than does Escherichia coli asparaginase. In a series of 11 adult patients with ALL, we investigated some parameters of the coagulation system during treatment with Erwinia asparaginase. The doses employed were rather high; all patients below the age of 60 years received 15,000 U/m2 daily over 14 days. In accordance with what is known from treatment with E. coli asparaginase, we observed significant lowering of antithrombin as well as of fibrinogen. However, as to fibrinogen indeed a significant decrease had occurred prior to the institution of Erwinia asparaginase treatment. The most striking observation in the present study was that the levels of prothrombin complex, reflecting the function of K-vitamin dependent coagulation factors II, VII and X, remained within normal ranges during treatment. This indicates that these coagulation factors were not affected by Erwinia asparaginase, an observation at variance with several reports where E. coli asparaginase was investigated. This latter observation was the only finding which could lend support to the view that Erwinia asparaginase affects the coagulation system less than E. coli asparaginase. Finally, one of our patients developed a sinus thrombosis, a severe thrombotic complication.

Protein S and protein C anticoagulant activity in acute and chronic cardiac ischemic syndromes. Relationship to inflammation, complement activation and in vivo thrombin activity

Protein S (PS) and protein C (PC) anticoagulant activities and thrombin-antithrombin complex (TAT) were measured in 20 patients with AIS, 25 patients with chronic stable angina (CSA) and a control group (C). Although plasma levels of TAT were significantly elevated in patients with CSA (p < 0.01 vs C), they were much higher in patients with AIS (p < 0.001 vs CSA). PC anticoagulant activity was similar in patients and controls. At variance, PS anticoagulant activity was lower in patients with AIS than in those with CSA and controls (p < 0.05), reflecting differences in total PS and C4B-binding protein (C4B-BP) antigen possibly resulting from involvement in the mechanisms of inflammation, complement activation and acute-phase response. The ratios of anticoagulant PS and PC to procoagulant vitamin K-dependent factors IX and II were reduced in AIS patients (0.05 > p > 0.005 vs C). In addition, the ratios of anticoagulant PC and PS to factor IX were lower in patients with AIS than in those with CSA (p < 0.05). These results indicate that in patients with acute ischemic cardiac syndromes the markedly increased in vivo thrombin generation is associated with an unbalance between coagulant and anticoagulant vitamin K-dependent factors.

Minimal effects of E. coli and Erwinia asparaginase on the coagulation system in childhood acute lymphoblastic leukemia: a randomized study

A randomized study was done in twenty newly diagnosed children with acute lymphoblastic leukemia. Ten children were treated with Escherichia coli L-asparaginase, and ten with Erwinia chrysanthemi L-asparaginase. L-asparaginase (ASP) treatment started halfway during ALL-induction treatment with vincristine, prednisone, daunorubicin and intrathecal methotrexate. The mean activated partial thromboplastin time (APTT) level in all children demonstrated a significant fall (P < 0.001) from 28.25 sec at diagnosis to 23.0 sec at the start of ASP treatment. In this same time interval, the mean fibrinogen level declined markedly from 3 g/l to 1.2 g/l (P < 0.001), probably due to prednisone therapy. The APTT stayed shortened during ASP therapy, whereas the hypofibrinogenemia recovered significantly faster in the Erwinia group (P < or = 0.01). Factors (F) II, V, VII and X stayed within the normal range, while F VIII and F IX were elevated. During the entire period of induction therapy, the ATIII activity remained within the normal range in both treatment groups. The protein C values, however, demonstrated a steady decline from 140% at start of ASP treatment to a mean of 81% and 93%, respectively, at the end of the ASP therapy in the E. coli and Erwinia group. Five of the ten children treated with E. coli ASP demonstrated protein C levels below 70% at the end of ASP therapy, opposed to none of the Erwinia treated patients (P = 0.03). We suggest that the effect of ASP resulting in decreased coagulation factor synthesis is in part counterbalanced by the effect of prednisone on the coagulation system, when ASP is administered at the end of ALL induction treatment. The overall effect of ASP either of E. coli or of Erwinia on the hemorrhagic system reveals a slight imbalance towards thrombosis, mainly because of a gradual decrease in protein C activity. This imbalance is less pronounced in the Erwinia group.

Incidence of thrombotic complications in adult patients with acute lymphoblastic leukaemia receiving L-asparaginase during induction therapy: a retrospective study. The GIMEMA Group

The incidence of thrombotic complications chronologically related to L-asparaginase administration is retrospectively analyzed in 238 adult ALL patients treated according to the GIMEMA protocol ALL 0288. The patients (126 males and 112 females, aged 12-68 years, median 29) received E. coli L-asparaginase (L-ase) in the induction phase at a dosage of 6000 U/m2/day x 7 d starting on d 15, as well as vincristine, prednisone, daunorubicin and cyclophosphamide, the last-named by random 1:1. Ten patients (4.2%) developed thrombotic complications 5-15 d (median 11 d) after the start of L-ase treatment. The thrombotic events, which were lethal in 5 patients, involved the cerebral sinus (5 cases), the cerebral arteria (2 cases), the portal vein (1 case), the pulmonary district (1 case), and a deep vein in the lower extremity (1 case). The occurrence of these complications was not related to the general thrombotic risk factors, nor to the main clinical and laboratory data registered at diagnosis and immediately before the start of L-asparaginase treatment. The present study documents for the first time in a sufficiently large series of adult ALL patients that the incidence and the severity of thrombotic events related to L-ase administration are relevant and need further consideration.

Hypercoagulability during L-asparaginase treatment: the effect of antithrombin III supplementation in vivo

To evaluate the occurrence of hypercoagulability during treatment with L-asparaginase (L-ase), thrombin-antithrombin complex (TAT) and D-dimer levels in plasma were serially measured in 15 consecutive adult patients with acute lymphoblastic leukaemia or lymphoblastic lymphoma who had recently completed a chemotherapy cycle with cytosine arabinoside and methotrexate. The first eight patients (group A) received i.v. L-ase alone (20,000 U/m2 on alternate days over 10 d); the last seven patients (group B) received, in addition to L-ase, bolus injection of antithrombin concentrate (2000 U) on alternate days for a total of six administrations, beginning with the second L-ase infusion. Increased levels of TAT (P less than 0.05) and D-dimer (P less than 0.01) were observed prior to L-ase, possibly related to inflammation and cytolysis secondary to previous chemotherapy. In patients treated with L-ase alone, further elevation of TAT (P less than 0.05) and persistence of increased D-dimer were observed, associated with marked reduction of the anticoagulant activities of protein C, protein S and antithrombin III. At variance, in patients receiving antithrombin III supplementation there was no increase of TAT and a normalization of D-dimer levels occurred during L-ase treatment. In these patients, mean plasma antithrombin III activity was maintained at levels higher than 70% of normal throughout the treatment. The rate of decline of fibrinogen, factor IX, protein C and protein S was unaffected by antithrombin III supplementation, indicating that hypercoagulability has little if any relevance for the reduction of coagulation factors and inhibitors induced by L-ase treatment. The usefulness of antithrombin III concentrates in preventing thromboembolic complications in patients submitted to L-ase treatment remains to be determined.