Insight into the mechanism of asparaginase-induced depletion of antithrombin III in treatment of childhood acute lymphoblastic leukemia

Thromboprophylaxis with intermediate dose enoxaparin during asparaginase containing induction for young adults with acute lymphoblastic leukemia

Thrombosis rates among young adults receiving asparaginase (ASP) for acute lymphoblastic leukemia (ALL) can reach 34%, with highest risk during induction. Our institution implemented a standard practice of 1 mg/kg/day enoxaparin administered to young adults with ALL who are treated with ASP during induction. We performed a retrospective analysis of patients who received thromboprophylaxis with enoxaparin 1 mg/kg/day during ASP-containing induction for ALL at Oregon Health & Science University from 2012 to 2023. The primary outcome was the cumulative incidence of thrombosis during induction. Bleeding events were assessed. Sixty-two patients were included in our analysis. Four patients (6.5%; 95% CI 1.8%-15.7%) experienced a thrombotic event. Three events were catheter-associated and 1 event was a distal lower extremity deep vein thrombosis related to myositis. No cerebral sinus thromboses, thrombosis-related deaths or major bleeding events occurred. Intermediate-dose enoxaparin is a promising thromboprophylaxis strategy and warrants further prospective research.

Global coagulation assays detect an early prothrombotic state in children with acute lymphoblastic leukemia

BACKGROUND

Pediatric patients with acute lymphoblastic leukemia (ALL) are at highest risk of venous thromboembolism during the induction therapy (IT). These events are not predictable by conventional coagulation assays.

OBJECTIVES

To investigate the utility of global coagulation assays (GCAs) for assessing the hemostatic state in children with ALL during IT.

METHODS

We included children with ALL (n = 15) and healthy controls (n = 15). Analyses were performed at different time points during IT of the AIEOP-BFM protocols. In addition to prothrombotic biomarkers, natural anticoagulant proteins, and in vivo thrombin generation (TG) markers, ex vivo TG was measured using the gold standard calibrated automated thrombogram method, automated ST Genesia, and thrombodynamics analyzer (TD). The latter also provided measurement of fibrin clot formation.

RESULTS

Different from conventional coagulation assays and in vivo TG markers, ex vivo GCAs detected increasing prothrombotic changes during IT. Particularly, TG measured with TD as expressed by endogenous thrombin potential was already significantly elevated at days 8 to 12 (P < .01) and continued to increase during IT compared with prior to beginning treatment, indicating a very early shift toward a procoagulant state. A similar pattern was observed for the rate of fibrin clot formation (stationary rate of clot growth: P < .01 at days 8-12). Remarkably, in patients developing thrombotic complications (n = 5), both GCAs, ST Genesia and TD, showed a significantly higher endogenous thrombin potential very early (already at days 8-12, P < .05), well before clinical manifestation.

CONCLUSION

GCAs capture prothrombotic changes early during IT in ALL pediatric patients. If confirmed, this approach will allow tailoring thromboprophylaxis in children with ALL at highest risk for venous thromboembolism.

Correlation between asparaginase enzyme activity levels and coagulation parameters during childhood acute lymphoblastic leukemia treatment

Thromboembolism is a serious toxicity in the treatment of acute lymphoblastic leukemia (ALL), but little is known about the correlation between asparaginase enzyme activity (ASA) levels and coagulation parameters. We included 65 non-high risk ALL patients, aged 1-17 years. Coagulation parameters and corresponding ASA levels were measured during asparaginase treatment. We found ASA to be negatively correlated with antithrombin and fibrinogen up to ASA levels of 250 IU/L, after which these parameters reached a plateau and did not decrease further with further increase of ASA. Patients with silent inactivation of asparaginase had normal coagulation parameters.

Antithrombin Therapy: Current State and Future Outlook

Antithrombin (AT) is a natural anticoagulant pivotal in inactivating serine protease enzymes in the coagulation cascade, making it a potent inhibitor of blood clot formation. AT also possesses anti-inflammatory properties by influencing anticoagulation and directly interacting with endothelial cells. Hereditary AT deficiency is one of the most severe inherited thrombophilias, with up to 85% lifetime risk of venous thromboembolism. Acquired AT deficiency arises during heparin therapy or states of hypercoagulability like sepsis and premature infancy. Optimization of AT levels in individuals with AT deficiency is an important treatment consideration, particularly during high-risk situations such as surgery, trauma, pregnancy, and postpartum. Here, we integrate the existing evidence surrounding the approved uses of AT therapy, as well as potential additional patient populations where AT therapy has been considered by the medical community, including any available consensus statements and guidelines. We also describe current knowledge regarding cost-effectiveness of AT concentrate in different contexts. Future work should seek to identify specific patient populations for whom targeted AT therapy is likely to provide the strongest clinical benefit.

Current Use of Asparaginase in Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

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

Thrombosis Complications in Pediatric Acute Lymphoblastic Leukemia: Risk Factors, Management, and Prevention: Is There Any Role for Pharmacologic Prophylaxis?

Pediatric acute lymphoblastic leukemia (ALL) has achieved close to 90% cure rates through extensive collaborative and integrative molecular research, clinical studies, and advances in supportive care. Despite this high achievement, venous thromboembolic complications (VTE) remain one of the most common and potentially preventable therapy-associated adverse events in ALL. The majority of thromboses events involve the upper central venous system which is related to the use and location of central venous catheters (CVC). The reported rates of symptomatic and asymptomatic CVC-related VTE range from 2.6 to 36.7% and 5.9 to 43%, respectively. Thrombosis can negatively impact not only disease-free survival [e.g., therapy delays and/or interruption, omission of chemotherapy agents (e.g., asparaginase therapy)] but also can result in long-term adverse effects that can impair the quality of life of ALL survivors (e.g., post-thrombotic syndrome, central nervous system (CNS)-thrombosis related complications: seizures, neurocognitive deficits). In this review, will discuss thrombosis pathophysiology in pediatric ALL, risk factors, treatment, and prevention strategies. In addition, the recently published clinical efficacy and safety of direct oral anticoagulants (DOACs) use in thrombosis treatment, and their potential role in primary/secondary thrombosis prevention in pediatric patients with ALL will be discussed. Future clinical trials involving the use of these novel oral anticoagulants should be studied in ALL not only for primary thrombosis prevention but also in the treatment of thrombosis and its secondary prevention. These future research findings could potentially extrapolate to VTE prevention strategies in other pediatric cancer diagnoses and children considered at high risk for VTE.

Coagulation abnormalities in childhood acute lymphoblastic leukemia: assessing the impact of L-asparaginase therapy in Ghana

BACKGROUND

Although the rate of childhood acute lymphoblastic leukemia (ALL) is increasing in Africa, there is a dearth of information on the disease and the dynamics of hemostatic parameters with therapy.

METHODS

In this case-control study, we evaluated variations in the level/activity of selected coagulation parameters among cALL in Ghana and healthy controls stratified by stage of therapeutic management.

RESULTS

In all, the research recruited 104 participants comprising 26 cALL cases and 78 healthy controls. The cALL group had significantly higher prothrombin time (PT) (p = 0.001), activated partial thromboplastin time (APTT) (p < 0.0001) and D-dimers (p = 0.001) but lower platelet (PLT) count, protein C (PC) (p < 0.0001), protein S (PS) (p < 0.0001) and antithrombin III (ATIII) (p < 0.0001) compared to controls. Compared to the healthy controls, activity of PC was lower during induction (p < 0.0001), consolidation (p = 0.005) and maintenance phases of chemotherapy (p = 0.012) while activities of PS and ATIII were lower at both induction (p < 0.0001, p = 0.006) and consolidation (p < 0.0001, p = 0.018) phases of chemotherapy.

CONCLUSION

Our findings provide evidence in the context of Africa and corroborates previous reports that cALL could result in a state of hypercoagulability, possibly leading to a high risk of thrombosis and thromboembolic complications. This possibly increased risk is not limited to the induction phase but also the consolidation phase.

Clinical Utility of Pegaspargase in Children, Adolescents and Young Adult Patients with Acute Lymphoblastic Leukemia: A Review

Acute lymphoblastic leukemia (ALL) is a heterogenous hematological malignancy representing 25% of all cancers in children less than 15 years of age. Significant improvements in survival and cure rates have been made over the past four decades in pediatric ALL treatment. Asparaginases, derived from Escherichia coli and Erwinia chrysanthemi, have become a critical component of ALL therapy since the 1960s. Asparaginases cause depletion of serum asparagine, leading to deprivation of this critical amino acid for protein synthesis, and hence limit survival of lymphoblasts. Pegaspargase, a conjugate of monomethoxypolyethylene glycol (mPEG) and L-asparaginase, has become an integral component of pediatric upfront and relapsed ALL protocols due to its longer half-life and improved immunogenicity profile compared to native asparaginase preparations. Over the past two decades great strides have been made in outcomes for pediatric ALL due to risk stratification, incorporation of multiagent chemotherapy protocols, and central nervous system prophylaxis with pegaspargase having played an important role in this success. However, adolescents and young adults (AYA) with ALL when treated on contemporaneous trials using adult ALL regimens, continue to have poor outcomes. There is increasing realization of adapting pediatric trial regimens for treating AYAs, especially those incorporating higher intensity of chemotherapeutic agents with pegaspargase being one such agent. Dose or treatment-limiting toxicity is observed in 25-30% of patients, most notable being hypersensitivity reactions. Other toxicities include asparaginase-associated pancreatitis, thrombosis, liver dysfunction, osteonecrosis, and dyslipidemia. Discontinuation or subtherapeutic levels of asparaginase are associated with inferior disease-free survival leading to higher risk of relapse, and in cases of relapse, a higher risk for remission failure. This article provides an overview of available evidence for use of pegaspargase in pediatric acute lymphoblastic leukemia.

Venous Thromboembolism and Its Risk Factors in Children with Acute Lymphoblastic Leukemia in Israel: A Population-Based Study

Venous thromboembolism (VTE) is a serious complication of acute lymphoblastic leukemia (ALL) therapy. The aim of this population-based study was to evaluate the rate, risk factors, and long-term sequelae of VTE in children treated for ALL. The cohort included 1191 children aged 1-19 years diagnosed with ALL between 2003-2018, prospectively enrolled in two consecutive protocols: ALL-IC BFM 2002 and AIEOP-BFM ALL 2009. VTEs occurred in 89 patients (7.5%). Long-term sequelae were uncommon. By univariate analysis, we identified four significant risk factors for VTEs: Severe hypertriglyceridemia (p = 0.005), inherited thrombophilia (p < 0.001), age >10 years (p = 0.015), and high-risk ALL group (p = 0.039). In addition, the incidence of VTE was significantly higher in patients enrolled in AIEOP-BFM ALL 2009 than in those enrolled in ALL-IC BFM 2002 (p = 0.001). Severe VTE occurred in 24 children (2%), all of whom had at least one risk factor. Elevated triglyceride levels at diagnosis did not predict hypertriglyceridemia during therapy. In a multivariate analysis of 388 children, severe hypertriglyceridemia and inherited thrombophilia were independent risk factors for VTE. Routine evaluation for these risk factors in children treated for ALL may help identify candidates for intervention.

Antithrombin and fibrinogen levels as predictors for plasma L-asparaginase activity in children with acute lymphoblastic leukemia

BACKGROUND

L-asparaginase is a cornerstone treatment for children with acute lymphoblastic leukemia (ALL). However, immune reaction to the drug may increase the clearance or impair the function of L-asparaginase and reduces its therapeutic efficacy. The objective of this study was to identify potential plasma proteins that could be used as proxies for L-asparaginase activity.

METHODS

Fibrinogen, von Willebrand factor antigen (VWF:Ag), total protein, and albumin levels as well as antithrombin (AT) and L-asparaginase activities were measured in 97 children with ALL treated for prolonged period of time with L-asparaginase. Binary logistic regression and a receiver operating characteristic (ROC) curve analysis were performed to evaluate the predictive value of plasma proteins for L-asparaginase activity.

RESULTS

Median E. coli L-asparaginase activity was 220 IU/L (range, 0-1308) throughout the treatment period. L-asparaginase activity was below 100 IU/L in 23% of measured samples. L-asparaginase activity was inversely associated with AT activity, fibrinogen, total protein, and albumin levels (r = -0.63, -0.62, -0.57, and -0.45, respectively; P < 0.0001), but not with VWF:Ag. ROC curve analyses showed an intermediate accuracy of AT activity (area under the ROC curve [AUC] = 0.77) to detect specimens with subtherapeutic level of L-asparaginase. An optimal accuracy was found when AT and fibrinogen were combined (AUC = 0.82; sensitivity = 75%; specificity = 82%; positive predictive value = 55%; negative predictive value = 92%) with cutoff values of 0.73 IU/mL and 1.85 g/L, respectively.

CONCLUSIONS

AT combined with fibrinogen levels could be used as a proxy to identify patients with therapeutic level of L-asparaginase activity in the absence of real-time asparaginase measurement during prolonged exposure to L-asparaginase.

THROMBOTECT - a randomized study comparing low molecular weight heparin, antithrombin and unfractionated heparin for thromboprophylaxis during induction therapy of acute lymphoblastic leukemia in children and adolescents

Thromboembolism is a serious complication of induction therapy for childhood acute lymphoblastic leukemia. We prospectively compared the efficacy and safety of antithrombotic interventions in the consecutive leukemia trials ALL-BFM 2000 and AIEOP-BFM ALL 2009. Patients with newly diagnosed acute lymphoblastic leukemia (n=949, age 1 to 18 years) were randomized to receive low-dose unfractionated heparin, prophylactic low molecular weight heparin (enoxaparin) or activity-adapted antithrombin throughout induction therapy. The primary objective of the study was to determine whether enoxaparin or antithrombin reduces the incidence of thromboembolism as compared to unfractionated heparin. The principal safety outcome was hemorrhage; leukemia outcome was a secondary endpoint. Thromboembolism occurred in 42 patients (4.4%). Patients assigned to unfractionated heparin had a higher risk of thromboembolism (8.0%) compared with those randomized to enoxaparin (3.5%; P=0.011) or antithrombin (1.9%; P<0.001). The proportion of patients who refused antithrombotic treatment as allocated was 3% in the unfractionated heparin or antithrombin arms, and 33% in the enoxaparin arm. Major hemorrhage occurred in eight patients (no differences between the groups). The 5-year event-free survival was 80.9±2.2% among patients assigned to antithrombin compared to 85.9±2.0% in the unfractionated heparin group (P=0.06), and 86.2±2.0% in the enoxaparin group (P=0.10). In conclusion, prophylactic use of antithrombin or enoxaparin significantly reduced thromboembolism. Despite the considerable number of patients rejecting the assigned treatment with subcutaneous injections, the result remains unambiguous. Thromboprophylaxis - for the present time primarily with enoxaparin - can be recommended for children and adolescents with acute lymphoblastic leukemia during induction therapy. Whether and how antithrombin may affect leukemia outcome remains to be determined.

Asparaginase inhibits the lectin pathway of complement activation

Oncological treatment has been associated with an increased risk of infection, most often related to therapy-induced pancytopenia. However, limited research has been conducted on the effect of oncological therapy on the complement system, being part of the non-cellular innate immune system. This became the rationale for an observational clinical study (C2012) in which we have investigated the prevalence of transient complement defects. Once we had observed such defects, a correlation of the complement defects to specific clinical parameters or to specific therapeutic regimens was investigated. A prominent defect observed in C2012 was the inhibition of the lectin pathway (LP) of complement activation during the treatment of acute lymphoblastic leukemia (ALL), which we could directly associate to the use of asparaginase (ASNase). Ex-vivo experiments confirmed a direct dose-dependent inhibitory effect of ASNase on the LP functionality.

Activity levels of natural anticoagulant proteins in childhood acute lymphoblastic leukemia: relation to thromboembolic complications and treatment

Thromboembolism is a well recognized life-threatening complication in childhood acute lymphoblastic leukemia (ALL). Proper and early diagnosis of thromboembolism is of paramount importance to reduce mortality and morbidity. We evaluated antithrombin III (ATIII), protein C, protein S, and D-dimer in 60 children with ALL compared with 30 healthy controls, and patients were followed up for 12 months for detection of thrombotic complications. The relation between these natural anticoagulants and the development of thrombotic complications, as well as therapy was assessed to identify patients at risk of thromboembolism. ATIII, protein C, and protein S were significantly reduced (P < 0.001) with elevated D-dimer (P < 0.001) in patients with ALL compared with those in the control group. The incidence of thrombotic complications was 16.7%. Patients with thrombotic complications had significantly lower ATIII, protein C, protein S, and platelet count, whereas age, total leukocyte count, and D-dimer were increased compared with those without thrombosis (P < 0.05). Patients under chemotherapy had lower ATIII, protein C, and protein S levels with higher D-dimer compared with the newly diagnosed untreated patients (P < 0.05). ATIII and protein C were positively correlated (r = 0.573, P = 0.002), whereas both were negatively correlated with D-dimer (P < 0.001). ALL is associated with a state of hypercoagulability, which may be attributed to hemostatic derangement because of increased thrombin generation indicated by elevated D-dimer in association with decreased natural anticoagulants ATIII, protein C, and protein S. ALL children during induction/consolidation phase of chemotherapy are at high risk of developing thromboembolism complications and the prophylactic use of anticoagulant should be considered.

Antithrombin III as the Indicator of L-Asparaginase Activity in Children Treated for Acute Lymphoblastic Leukemia

L-asparaginase (ASP) is widely used in the treatment of acute lymphoblastic leukemia (ALL) in children. Monitoring its activity is necessary because of the risk of drug inactivation as the result of an immune reaction. Besides allergic reactions, another frequent side effect of ASP treatment is coagulopathy, especially deficiency of antithrombin III (ATIII). The aim of this study was to analyze the relationship between ASP and ATIII activities and the possibility of ATIII activity use in an indirect ASP activity assessment. ASP and ATIII activity was measured in 76 children with ALL treated according to the ALL IC BFM 2002 protocol. A correlation between ASP and ATIII activities was found (R=-0.43, P=0.0001). ROC curve analysis revealed some utility regarding the determination of ATIII in identifying patients with low or undetectable ASP activity (area under the curve=0.87 [95% confidence interval, 0.77-0.96], P<0.0001 and 0.93 [95% confidence interval, 0.85-1.0], P<0.0001, respectively). Higher ATIII activity is associated with a higher probability of a decline in ASP activity. Examination of ATIII activity cannot replace a direct determination of ASP activity, but in the case of unavailability of the direct test, it can be a helpful surrogate parameter of drug activity.

Cell-based laboratory evaluation of coagulation activation by antineoplastic drugs for the treatment of lymphoid tumors

Objectives:

Combining vorinostat, L-asparaginase, and doxorubicin (Dox) led to improved response rates in the treatment of lymphoid tumors. However, deep-vein thrombosis has been noted as one of the most serious side effects with these drugs, and how these regimens cause deep-vein thrombosis is unclear.

Methods:

We investigated the procoagulant effects of vorinostat, L-asparaginase, and doxorubicin in lymphoid tumors, focusing on tissue factor, phosphatidylserine, and antithrombin. The human vascular endothelial cell line EAhy926 as well as the lymphoid neoplastic cell lines HUT78 (cutaneous T-cell lymphoma), Molt4 (acute T-lymphoblastic leukemia), and Ramos (Burkitt lymphoma) were employed to investigate these procoagulant effects.

Results:

Vorinostat, L-asparaginase, and doxorubicin induced exposure of phosphatidylserine and procoagulant activity on the surface of lymphoid tumor cells. Vorinostat and doxorubicin also induced phosphatidylserine exposure and increased procoagulant activity on EAhy926 cells. Expression of tissue factor antigen was induced by doxorubicin on the surface of each type of cells, whereas expression of tissue factor mRNA was unchanged. Secretion of antithrombin from HepG2 cells was reduced only by L-asparaginase.

Conclusion:

These data suggest that vorinostat and doxorubicin may induce procoagulant activity in vessels through apoptosis of tumor cells and through phosphatidylserine exposure and/or tissue factor expression on vascular endothelial cells. L-asparaginase may induce a thrombophilic state by reducing the secretion of anticoagulant proteins such as antithrombin. The laboratory methods described here could be useful to evaluate the procoagulant effects of antineoplastic drugs.

Design and Characterization of Erwinia Chrysanthemi l-Asparaginase Variants with Diminished l-Glutaminase Activity

Current FDA-approved l-asparaginases also possess significant l-glutaminase activity, which correlates with many of the toxic side effects of these drugs. Therefore, l-asparaginases with reduced l-glutaminase activity are predicted to be safer. We exploited our recently described structures of the Erwinia chrysanthemi l-asparaginase (ErA) to inform the design of mutants with diminished ability to hydrolyze l-glutamine. Structural analysis of these variants provides insight into the molecular basis for the increased l-asparagine specificity. A primary role is attributed to the E63Q mutation that acts to hinder the correct positioning of l-glutamine but not l-asparagine. The substitution of Ser-254 with either an asparagine or a glutamine increases the l-asparagine specificity but only when combined with the E63Q mutation. The A31I mutation reduces the substrate Km value; this is a key property to allow the required therapeutic l-asparagine depletion. Significantly, an ultra-low l-glutaminase ErA variant maintained its cell killing ability. By diminishing the l-glutaminase activity of these highly active l-asparaginases, our engineered ErA variants hold promise as l-asparaginases with fewer side effects.

Asparaginase Erwinia chrysanthemi as a component of a multi-agent chemotherapeutic regimen for the treatment of patients with acute lymphoblastic leukemia who have developed hypersensitivity to E. coli-derived asparaginase

Asparaginase has been a mainstay of therapy in the treatment of acute lymphoblastic leukemia since the 1970s. There are two major preparations available and FDA approved in the United States today, one derived from Escherichia coli and the other from Erwinia chrysanthemi. Erwinia asparaginase is antigenically distinct from and has a considerably shorter biological half-life than E coli asparaginase. Erwinia asparaginase has been used in cases of hypersensitivity to E. coli-derived asparaginases, which has been reported in up to 30% of patients. While PEG asparaginase is increasingly used in front-line therapy for ALL, hypersensitivity still occurs with this preparation, and a change to a non-cross-reactive preparation may be necessary.

L-asparaginase and venous thromboembolism in acute lymphocytic leukemia

The occurrence of venous thromboembolism (VTE) in acute lymphocytic leukemia patients receiving L-asparaginase therapy may cause significant morbidity, neurological sequela and possibly worse outcomes. The prophylactic use of antithrombin infusion (to keep antithrombin activity >60%) or low molecular weight heparin (LMWH) may reduce the risk of VTE. The decision to continue L-asparaginase therapy after the development of VTE should be based on anticipated benefits, severity of VTE and the ability to continue therapeutic anticoagulation. In patients receiving asparaginase rechallenge, the use of therapeutic LMWH, monitoring of anti-Xa level and antithrombin level are important. Novel oral anticoagulants are not dependent on antithrombin level, hence offer theoretical advantages over LMWH for the prevention and therapy of asparaginase-related VTE.

L-Asparaginase lowers plasma antithrombin and mannan-binding-lectin levels: Impact on thrombotic and infectious events in children with acute lymphoblastic leukemia

BACKGROUND

L-asparaginase, a key therapeutic agent in the management of patients with acute lymphoblastic leukemia (ALL), dramatically impairs hepatic protein synthesis. We investigated the effects of prolonged exposure to L-asparaginase on antithrombin (AT), fibrinogen and mannan-binding-lectin (MBL) levels, and on the occurrence of thrombotic events (TE) and febrile neutropenia episodes (FN) in pediatric patients.

PROCEDURE

Protein levels were measured in 97 children during 30 weeks of chemotherapy with L-asparaginase and up to 1 year following remission. TE and FN episodes were recorded during this period.

RESULTS

Median AT level decreased from 0.96 IU/mL prior to treatment (range: 0.69-1.38) to 0.55 IU/mL (0.37-0.76) during therapy. Fibrinogen and MBL decreased from 3.18 g/L (1.29-7.28) and 1,177 ng/mL (57-5,343) to 1.56 g/L (0.84-2.13) and 193 ng/mL (57-544), respectively. All three proteins had recovered 1-4 weeks after L-asparaginase cessation. TE were reported in 22 (23%) patients. Of these, 11 occurred after a median of 10 administrations of L-asparaginase. Fifty-one FN were associated with infections, of which 36 occurred during treatment with L-asparaginase. Patients with low levels of MBL at diagnosis were at higher risk of FN associated with infections (RR = 1.59, 95%CI: 1.026-2.474). Both AT and MBL decreases were moderately correlated with fibrinogen (r = 0.51 and 0.58, respectively).

CONCLUSIONS

Children with ALL are exposed to significant decrease in AT, fibrinogen and MBL levels, and concomitant increased risk of thrombosis and FN with infection during L-asparaginase treatment. Measuring plasma levels of these liver-derived proteins could help predict the occurrence of adverse events.

[Role of antithrombin iii in cardiac surgery]

Coagulation of blood is of multidisciplinary interest. Cardiac surgery produces major changes in the delicate balance between pro-and anti-coagulant serum factors. The role of antithrombin iii has been analysed after finding evidence that associated decreased levels of protein activity to postoperative morbidity and mortality. Supplementing exogenous antithrombin is considered with the aim of optimising outcomes. Its intrinsic anticoagulant and anti-inflammatory properties have stimulated a growing interest, and suggests new lines of research.

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 leukemia

Thrombosis is a common complication in patients with acute leukemia. While the presence of central venous lines, concomitant steroids, the use of Escherichia coli asparaginase and hereditary thrombophilic abnormalities are known risk factors for thrombosis in children, information on the pathogenesis, risk factors, and clinical outcome of thrombosis in adult patients with acute lymphoid leukemia (ALL) or acute myeloid leukemia (AML) is still scarce. Expert consensus and guidelines regarding leukemia-specific risk factors, thrombosis prevention, and treatment strategies, as well as optimal type of central venous catheter in acute leukemia patients are required. It is likely that each subtype of acute leukemia represents a different setting for the development of thrombosis and the risk of bleeding. This is perhaps due to a combination of different disease-specific pathogenic mechanisms of thrombosis, including the type of chemotherapy protocol chosen, the underlying patients health, associated risk factors, as well as the biology of the disease itself. The risk of thrombosis may also vary according to ethnicity and prevalence of hereditary risk factors for thrombosis; thus, it is advisable for Latin American, Asian, and African countries to report on their specific patient population.

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.

Antithrombin deficiency and its laboratory diagnosis

Antithrombin (AT) belongs to the serpin family and is a key regulator of the coagulation system. AT inhibits active clotting factors, particularly thrombin and factor Xa; its absence is incompatible with life. This review gives an overview of the protein and gene structure of AT, and attempts to explain how glucosaminoglycans, such as heparin and heparan sulfate accelerate the inhibitory reaction that is accompanied by drastic conformational change. Hypotheses on the regulation of blood coagulation by AT in physiological conditions are discussed. Epidemiology of inherited thrombophilia caused by AT deficiency and its molecular genetic background with genotype-phenotype correlations are summarized. The importance of the classification of AT deficiencies and the phenotypic differences of various subtypes are emphasized. The causes of acquired AT deficiency are also included in the review. Particular attention is devoted to the laboratory diagnosis of AT deficiency. The assay principles of functional first line laboratory tests and tests required for classification are discussed critically, and test results expected in various AT deficiency subtypes are summarized. The reader is provided with a clinically oriented algorithm for the correct diagnosis and classification of AT deficiency, which could be useful in the practice of routine diagnosis of thrombophilia.

Validation of a predictive model for identifying an increased risk for thromboembolism in children with acute lymphoblastic leukemia: results of a multicenter cohort study

Among risk factors for developing thromboembolism (VTE) in children with acute lymphoblastic leukemia were Escherichia coli asparaginase, concomitant steroid use, presence of central venous lines, and thrombophilic abnormalities. Developing a predictive model for determining children at increased risk would be beneficial in targeting interventional studies to high-risk groups (HRGs). Predictive variables were incorporated into a risk assessment model, which was evaluated in 456 children and then validated in 339 patients. VTE risk by score was no greater than 2.5 for low-risk group (LRG) and greater than 2.5 for HRG. VTE rates at 3.5 months (validation cohorts) were 2.5% in LRG and 64.7% in HRG. In multivariate analysis adjusted for age, duration of asparaginase administration, enoxaparin prophylaxis, and T-immunophenotype, the HRG was significantly associated with VTE compared with the LRG (hazard/95% confidence interval [CI], 8.22/1.85-36.53). Model specificity was 96.2% and sensitivity was 63.2%. As secondary objective we investigated the use of enoxaparin for VTE prophylaxis in the HRG. HRG patients without enoxaparin prophylaxis showed a significantly reduced thrombosis-free survival compared with children on low-molecular-weight heparin (LMWH). On the basis of the high specificity, the model may identify children with leukemia at risk of VTE. LMWH may help prevent VTE in the HRG; this warrants assessment in larger cooperative clinical trials.

Pharmacokinetic, pharmacodynamic and intracellular effects of PEG-asparaginase in newly diagnosed childhood acute lymphoblastic leukemia: results from a single agent window study

L-asparaginase is an effective drug for treatment of children with acute lymphoblastic leukemia (ALL). The effectiveness is thought to result from depletion of asparagine in serum and cells. We investigated the clinical response in vivo of 1000 IU/m(2) pegylated (PEG)-asparaginase and its pharmacokinetic, pharmacodynamic and intracellular effects in children with newly diagnosed ALL before start of combination chemotherapy. The in vivo window response was significantly related to immunophenotype and genotype: 26/38 common/pre B-ALL cases, especially those with hyperdiploidy and TELAML1 rearrangement, demonstrated a good clinical response compared to 8/17 T-ALL (P=0.01) and BCRABL-positive ALL (P=0.04). A poor in vivo clinical window response was related to in vitro resistance to L-asparaginase (P=0.02) and both were prognostic factors for long-term event-free survival (hazard ratio 6.4, P=0.004; hazard ratio 3.7, P=0.01). After administration of one in vivo dose of PEG-asparaginase no changes in apoptotic parameters or in intracellular levels of twenty amino acids in leukemic cells could be measured, in contradiction to the changes found after in vitro exposure. This may be explained by the rapid removal of apoptotic cells from the circulation in vivo. One additional dose of PEG-asparaginase upfront ALL treatment did not lead to other severe toxicities.

Hereditary and acquired antithrombin deficiency: epidemiology, pathogenesis and treatment options

Antithrombin is a glycoprotein critical to the regulation of coagulation. Its primary action is the inhibition of the activated coagulation factors IIa (thrombin) and Xa. In addition there is growing evidence to suggest that antithrombin also plays a role in the inhibition of inflammation within the environment of the vascular endothelium. Reduced plasma antithrombin may result from congenital deficiency or arise secondarily from a range of disorders such as liver dysfunction, premature infancy and sepsis, or as a result of interventions such as major surgery or cardiopulmonary bypass. Congenital antithrombin deficiency is the most clinically important of the inherited thrombophilias resulting in thrombosis in the majority of those affected. The challenge in managing these patients is preventing potentially life-threatening thrombosis, while minimising the equally significant risk of haemorrhage associated with long-term anticoagulation. This is achieved in the first instance by identifying high-risk episodes such as surgery, immobility and pregnancy for which prophylactic anticoagulation can be used in the short term. Prophylaxis for such periods is best provided by the use of low molecular weight heparin (LMWH) with substitution by or addition of antithrombin concentrate in particularly high-risk circumstances. In the case of pregnancy, antithrombin concentrate is often used around the time of birth when LMWH may increase the risk of post-partum haemorrhage. As patients with congenital antithrombin deficiency get older so their thrombotic risk gradually increases and for many patients long-term anticoagulation becomes unavoidable because of recurrent episodes of venous thromboembolism. There has been much interest in the role of antithrombin deficiency in the setting of sepsis and the critically ill patient where there is a clear correlation between severity of illness and degree of antithrombin reduction. It is not clear yet, however, to what extent the depletion of antithrombin affects the clinical condition of such patients. A number of trials have investigated the use of antithrombin as a treatment in the intensive care setting with the overall conclusion being that there is some benefit to its use but only if large supra-physiological doses are used. It has also become clear that the concurrent use of any form of heparin removes whatever benefit may be derived from antithrombin treatment in this setting. Until recently, antithrombin replacement was only available as a pooled plasma-derived product, which despite effective viral inactivation still carries an uncertain risk of transfusion transmitted infection. A recombinant antithrombin product now under investigation, and recently licensed in Europe, may provide a useful alternative treatment option.

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.

Seizures and epilepsy in oncological practice: causes, course, mechanisms and treatment

There are few data available on the causes and mechanistic basis, outcome and treatment of seizures and epilepsy in people with systemic cancer. Seizures and epilepsy in people with cancers other than primary brain tumours are reviewed here. Articles published in English, which discussed the neurological manifestations and complications of cancer and its treatment, were searched and information on the frequency, aetiology, and course of seizures and epilepsy was extracted. The frequency, aetiology and outcome of seizure disorders in patients with cancer differ from those in the general population. Intracranial metastasis, cancer drugs and metabolic disturbances are the most common causes. Infections, cerebrovascular complications of systemic cancer and paraneoplastic disorders are among the rarer causes of seizures in patients with neoplasms. Several drugs used in the treatment of cancer, or complications arising from their use, can trigger seizures through varied mechanisms. Most drug-induced seizures are provoked and do not require long-term treatment with antiepileptic drugs.

L-asparaginase-induced antithrombin type I deficiency: implications for conformational diseases

Serpinopathies, a group of diseases caused by mutations that disrupt the structurally sensitive serpins, have no known acquired cause. Interestingly, l-asparaginase treatment of acute lymphoblastic leukemia patients causes severe deficiency in the serpin antithrombin. We studied the consequences of this drug on antithrombin levels, activity, conformation, and immunohistological and ultrastructural features in plasma from acute lymphoblastic leukemia patients, HepG2 cells, and plasma and livers from mice treated with this drug. Additionally, we evaluated intracellular deposition of alpha1-antitrypsin. l-Asparaginase did not affect functional or conformational parameters of mature antithrombin; however, patients and mice displayed severe type I deficiency with no abnormal conformations of circulating antithrombin. Moreover, l-asparaginase impaired secretion of antithrombin by HepG2 cells. These effects were explained by the intracellular retention of antithrombin, forming aggregates within dilated endoplasmic reticulum cisterns. Similar effects were observed for alpha1-antitrypsin in plasma, cells, and livers, and intracellular aggregates of additional proteins were observed in frontal cortex and pancreas. This is the first report of a conformational drug-associated effect on serpins without genetic factors involved. l-Asparaginase treatment induces severe, acquired, and transient type I deficiency of antithrombin (and alpha1-antitrypsin) with intracellular accumulation of the nascent molecule, increasing the risk of thrombosis.

Incidence and etiology of cerebrovascular disease in patients with malignancy

Cerebrovascular disease is common in cancer patients and often arises from mechanisms unique to malignancy. Direct tumor effects include intratumoral hemorrhage, arterial and venous sinus invasion by tumor mass or leptomeningeal infiltrates, and tumor emboli. Complications of chemotherapy, radiation therapy, and hematopoietic stem-cell transplantion for cancer can occur before, during, or years after treatment. Coagulopathic conditions involve disseminated intravascular coagulation, thrombocytopenia, nonbacterial thrombotic endocarditis, and cerebral intravascular coagulation. Finally, septic infarction from fungal or bacterial sepsis and infectious vasculitis manifest in cancer patients immunocompromised by malignancy or cancer therapy. In many cases a combination of mechanisms is causative, and both hemorrhagic and ischemic stroke can occur simultaneously. Stroke type and mechanism, as well as the stage and pathology of the neoplasm, dictate proper management and help delineate prognosis.

Localization of heparin cofactor II in injured human skin: a potential role in wound healing

The physiologic function of the serpin heparin cofactor II (HCII) is not fully understood. We have hypothesized that HCII functions as an extravascular inhibitor of thrombin. Thrombin formed at a site of injury has been hypothesized to contribute to migration and proliferation of fibroblasts and smooth muscle cells involved in wound healing. To begin to test our hypothesis, we examined the immunohistochemical localization of HCII in human skin and compared it to that of the closely related serpin, antithrombin (ATIII). In skin specimens with acute wounds, there was diffuse HCII and ATIII staining in areas of hemorrhage. In healing skin wounds ATIII was primarily associated with mast cells, while HCII was associated with mononuclear phagocytes in the dermis. Blood monocytes isolated from healthy donors also stained for HCII protein. However, in situ hydridization and RT-PCR studies failed to show significant HCII mRNA expression either in macrophages in wounded skin or in peripheral blood leukocytes. HCII localization is not due to nonspecific uptake of plasma proteins, since ATIII had a very different distribution in wounded skin. These findings support the notion that HCII could function as an extravascular thrombin inhibitor and might play a role in the regulation of wound healing.

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.

Glutamine deprivation-mediated cell shrinkage induces ligand-independent CD95 receptor signaling and apoptosis

Cell shrinkage and loss of cell viability by apoptosis have been examined in cultured CD95(Fas/Apo-1)-expressing leukemia-derived CEM and HL-60 cells subjected to acute deprivation of glutamine, a major compatible osmolyte engaged in cell volume control. Glutamine deprivation-mediated cell shrinkage promoted a ligand-independent activation of the CD95-mediated apoptotic pathway. Cell transfection with plasmids expressing FADD-DN or v-Flip viral proteins pointed to a functional clustering of CD95 receptors at the cell surface with activation of the 'extrinsic pathway' caspase cascade. Accordingly, cell shrinkage did not induce apoptosis in CD95 receptor-negative lymphoma L1210 cells. Replacement of glutamine with surrogate compatible osmolytes counteracted cell volume decrement and protected the CD95-expressing cells from apoptosis. A glutamine deprivation-dependent cell shrinkage with activation of the CD95-mediated pathway was also observed when asparaginase was added to the medium. Asparagine depletion had no role in this process. The cell-size shrinkage-dependent apoptosis induced by glutamine restriction in CD95-expressing leukemic cells may therefore be of clinical relevance in amidohydrolase enzyme therapies.