Anticoagulant Effects of Dabigatran in Paediatric Patients Compared with Adults: Combined Data from Three Paediatric Clinical Trials

BACKGROUND

 Physiological age-related changes in the haemostatic and coagulation systems result in differing anticoagulant assay responses to standard anticoagulants. Therefore, we investigated the response of anticoagulant assays to dabigatran etexilate (DE) in children compared with adults.

OBJECTIVE

 This article assesses the relationship between plasma dabigatran concentration and coagulation assay results across age groups in children and adults.

PATIENTS AND METHODS

 Data from three clinical trials in which children received DE following standard of care for venous thromboembolism were compared with data from adult clinical trials. The effects of dabigatran concentration on diluted thrombin time (dTT), ecarin clotting time (ECT) and activated partial thromboplastin time (aPTT) were analysed graphically and with modelling.

RESULTS

 The concentration-dTT relationships were consistent in children across all ages and adults in the graphical analysis. For ECT and aPTT, relationships based on ratios over baseline were similar across all ages; absolute clotting times showed that the same exposure resulted in longer clotting times in some of the children aged < 1 year versus adults. Modelling showed concentration-clotting time relationships for all three assays were largely comparable between adults and children, except in those aged < 2 months, in whom there was a slight upward shift in ECT and aPTT relative to adults.

CONCLUSION

 Results suggest that developmental haemostatic changes will have little impact on response to DE. However, further paediatric clinical trials assessing the relationship between coagulation assay responses and clinical outcomes will be needed to confirm this finding.

Phase 3, single-arm, multicenter study of dabigatran etexilate for secondary prevention of venous thromboembolism in children: Rationale and design

BACKGROUND

Anticoagulant therapy for venous thromboembolism (VTE) in children is largely based on treatment recommendations for adults. However, differences in both physiology (ie, renal maturation and drug excretion) and developmental hemostasis must be considered when treating children, as such differences could affect dose appropriateness, safety and efficacy.

OBJECTIVES

To address these concerns, a study was designed to evaluate the safety of dabigatran etexilate in children requiring secondary thrombus prevention in whom an initial VTE was associated with an identified risk factor that persisted after the acute VTE treatment period. We report herein the rationale and design of the study.

PATIENTS/METHODS

This phase 3, open-label, single-arm, multicenter, multinational, prospective cohort study will be conducted in ≥100 children aged 0 to <18 years at ~100 specialist sites worldwide. Children will be treated with dabigatran etexilate for 12 months, or for a shorter duration if their identified VTE risk factor resolves, as per current American College of Chest Physicians recommendations. A nomogram will be used to determine starting doses for each patient.

RESULTS

The primary outcomes of the study will be VTE recurrence, bleeding events, overall mortality, and VTE-related mortality. Secondary outcomes will include occurrence of post-thrombotic syndrome, the pharmacokinetics of dabigatran, and the need for dose adjustments during treatment. Data on adverse events during the study will also be collected.

CONCLUSION

This study will evaluate the safety of dabigatran etexilate for the secondary prevention of VTE in children, in addition to providing further data to guide pediatric dosing with dabigatran.

Design and rationale for the DIVERSITY study: An open-label, randomized study of dabigatran etexilate for pediatric venous thromboembolism

BACKGROUND

The current standard of care (SOC) for pediatric venous thromboembolism (VTE) comprises unfractionated heparin (UFH), or low-molecular-weight heparin (LMWH) followed by LMWH or vitamin K antagonists, all of which have limitations. Dabigatran etexilate (DE) has demonstrated efficacy and safety for adult VTE and has the potential to overcome some of the limitations of the current SOC. Pediatric trials are needed to establish dosing in children and to confirm that results obtained in adults are applicable in the pediatric setting.

OBJECTIVES

To describe the design and rationale of a planned phase IIb/III trial that will evaluate a proposed dosing algorithm for DE and assess the safety and efficacy of DE versus SOC for pediatric VTE treatment.

PATIENTS/METHODS

An open-label, randomized, parallel-group noninferiority study will be conducted in approximately 180 patients aged 0 to <18 years with VTE, who have received initial UFH or LMWH treatment and who are expected to require ≥3 months of anticoagulation therapy. Patients will receive DE or SOC for 3 months. DE will be administered twice daily as capsules, pellets, or an oral liquid formulation according to patient age. Initial doses will be calculated using a proposed dosing algorithm.

RESULTS

There will be two coprimary endpoints: a composite efficacy endpoint comprising the proportion of patients with complete thrombus resolution, freedom from recurrent VTE and VTE-related mortality, and a safety endpoint: freedom from major bleeding events.

CONCLUSION

Findings will provide valuable information regarding the efficacy and safety of DE for the treatment of pediatric VTE. ClinicalTrials.gov registration number: NCT01895777.

Safety, tolerability and clinical pharmacology of dabigatran etexilate in adolescents

Venous thromboembolism (VTE) incidence is increasing among children owing to many factors, including improved diagnosis of VTE. There is a need for alternative treatment options. Our objective was to investigate the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran etexilate in adolescents with VTE. Adolescents aged 12 to <18 years (n = 9) who successfully completed planned treatment for primary VTE were administered dabigatran etexilate twice daily for three days; initially 1.71 (± 10%) mg/kg (80% of a 150 mg/70 kg twice daily adult dose), followed by 2.14 (± 10%) mg/kg (target adult dose adjusted for patient’s weight), if there were no safety concerns. No bleeding events, deaths or drug-related serious adverse events (AEs) were reported; three treatment-emergent AEs, all gastrointestinal-related, occurred in two patients. In these adolescent patients with normal renal function, presumed steady-state trough plasma concentrations of dabigatran were low (geometric mean dosenormalised total dabigatran plasma concentration: 0.493 ng/ml/mg at 72 hours). Total dabigatran concentrations were well predicted by the RE-LY® population PK model (94% of trough concentrations were within the 80% prediction interval). The relationship between total dabigatran plasma concentration, diluted thrombin time and ecarin clotting time (ECT) was linear; the relationship with activated partial thromboplastin time (aPTT) was non-linear. Adult population PK/PD models predicted the adolescent concentration–ECT and –aPTT relationships well. In conclusion, dabigatran etexilate was generally well tolerated, except for occurrence of dyspepsia in two patients, over the three-day treatment period. The dabigatran PK/PD relationship observed in adolescent patients was similar to that in adult patients.

Institution where work was performed: Main clinical study site: Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada.

This study is registered at ClinicalTrials.gov (NCT00844415).

Phase IIa study of dabigatran etexilate in children with venous thrombosis: pharmacokinetics, safety, and tolerability

Essentials Dabigatran etexilate may provide a new treatment option for pediatric venous thromboembolism. Children aged 1 to < 12 years were given dabigatran etexilate in an open-label, single-arm study. The pharmacokinetic-pharmacodynamic relationship was similar to that seen in adult patients. There were no serious adverse events, bleeding events or recurrent venous thromboembolism.

SUMMARY

Background The current standard-of-care treatments for pediatric venous thromboembolism (VTE) have limitations. Dabigatran etexilate (DE), a direct thrombin inhibitor, may offer an alternative therapeutic option. Objectives To assess the pharmacokinetics, pharmacodynamics, safety, and tolerability of a DE oral liquid formulation (OLF) in pediatric patients with VTE. Patients/Methods Patients who had completed planned treatment with low molecular weight heparin or oral anticoagulants for VTE were enrolled in two age groups (2 to < 12 years and 1 to < 2 years), and received a DE OLF based on an age-adjusted and weight-adjusted nomogram. Originally, patients were to receive a DE OLF twice daily for 3 days, but the protocol was amended to a single dose on day 1. The primary endpoints were pharmacokinetics/pharmacodynamics-related: plasma concentrations of DE and its metabolites; activated partial thromboplastin time (APTT), ecarin clotting time (ECT), and dilute thrombin time (dTT); and pharmacokinetic (PK)-pharmacodynamic (PD) correlation. Safety endpoints included incidence rates of bleeding events and all other adverse events (AEs). Results Eighteen patients entered the study and received the DE OLF (an exposure equivalent to a dose of 150 mg twice daily in adults). The projected steady-state dabigatran trough concentrations were largely comparable between pediatric patients and adults. The PK/PD relationship was linear for ECT and dTT, and non-linear for APTT. No serious or severe AEs, bleeding events, or recurrent VTEs were reported. Mild AEs were reported in three patients in the single-dose group (screening period) and in one patient in the multiple-dose group (on-treatment period). Conclusion The current study supports the further evaluation of DE OLFs in pediatric patients with VTE.