Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies

Present Knowledge on Direct Oral Anticoagulant and Novel Oral Anti Coagulants and Their Specific Antidotes: A Comprehensive Review Article

Thromboembolic diseases are one of the leading causes of morbidity and mortality worldwide. For a long time, heparin and Vitamin K antagonist (VKA) drugs were used for treatment and prophylaxis of the thromboembolic diseases. The development of newer direct and novel oral anticoagulant medications (DOACs/NOACs) has changed clinical practice significantly. Lesser monitoring, ease with dosing, less drug interactions have made these drugs useful to the providers and the patients. But these drugs have bleeding as a side effect. There is ongoing research on the specific antidotes of these anticoagulants in case of life-threatening bleeding. Though the use of the DOACs and NOACs have increased, there is still not enough clinical evidence about the specific antidotes of these medications. Unlike heparin or VKA, reversal of life-threatening bleeding in the setting of DOAC use is still a clinical challenge. We need more data on the dose, pharmacokinetics, and clinical efficacy of those antidotes. Authors have reviewed articles on DOACs and their antidotes in Pubmed and also in the clinical trial website. Specific antidotes including Idarucizumab for Dabigatran, Andexanet alfa for factor Xa inhibitors are being used to reverse the actions of the anticoagulants. Ciraparantag is a universal antidote for the DOACs, which is still under investigation. FXaI16L is currently being investigated as a potential universal antidote for multiple anticoagulants, including dabigatran and rivaroxaban. Though mostly safe, the use of DOACs can still carry a risk of severe bleeding in patients. More data on the use of the antidotes is required to reverse the side effect of DOACs if clinically indicated.

Idarucizumab Reverses Dabigatran Anticoagulant Activity in Healthy Chinese Volunteers: A Pharmacokinetics, Pharmacodynamics, and Safety Study

INTRODUCTION

Idarucizumab is a humanized monoclonal antibody fragment that specifically binds to dabigatran with high affinity and reverses its anticoagulant effect. This study investigated the pharmacokinetics (PK) and pharmacodynamics (PD) of idarucizumab in healthy Chinese subjects at steady state of dabigatran and explored the effect of idarucizumab on PK and PD of dabigatran.

METHODS

Twelve subjects received dabigatran etexilate treatment alone (220 mg twice daily, b.i.d., oral). After a washout period, the 12 subjects again received dabigatran etexilate (220 mg b.i.d., oral) and idarucizumab (2.5 + 2.5 g, intravenous) 2 h after the last administration of dabigatran etexilate.

RESULTS

The geometric mean (gMean) values of area under the plasma concentration-time curve (AUC_0-∞) and maximum concentration (C_max) were 44,200 nmol h/L and 30,900 nmol/L, respectively. An amount of 35.3 μmol of idarucizumab, corresponding to 33.8% of the total dose, was excreted by urine over 72 h. The area under the effect (AUEC_above,2-12) in the presence and absence of idarucizumab was close to zero for all coagulation parameters, diluted thrombin time (dTT), ecarin clotting time (ECT), activated partial thromboplastin time (aPTT), and thrombin time (TT), which indicated the reversal of dabigatran anticoagulation by idarucizumab. There were no serious adverse events reported in this study. No subject tested positive for anti-idarucizumab antibodies.

CONCLUSION

Idarucizumab was well tolerated and no subject tested positive for anti-idarucizumab antibodies in this study. PK and PD of idarucizumab in healthy Chinese subjects at a steady state of dabigatran were comparable with those in Japanese and Caucasian subjects.

CLINICAL REGISTRATION

ClinicalTrials.gov Identifier No. NCT03086356.

Pharmacokinetics of idarucizumab and its target dabigatran in patients requiring urgent reversal of the anticoagulant effect of dabigatran

BACKGROUND

Idarucizumab is a monoclonal antibody fragment that reverses dabigatran anticoagulation. Pharmacokinetics (PK) of idarucizumab have been described in healthy, elderly, or renally impaired (RI) volunteers, but PK data in patients are lacking.

OBJECTIVES

This analysis describes the PK of idarucizumab and its target dabigatran in bleeding/surgical patients.

PATIENTS AND METHODS

Results from the Reversal Effects of Idarucizumab on Active Dabigatran study, a prospective, multicenter, single-arm study demonstrated the reversal of dabigatran anticoagulation by idarucizumab in patients with uncontrollable bleeding (group A) or who needed urgent surgery (group B). Idarucizumab and unbound dabigatran concentrations, immunogenicity, and pharmacodynamics were assessed.

RESULTS

Total and unbound dabigatran levels at baseline were 165 ng/mL vs 110 ng/mL and 103 ng/mL vs 69.5 ng/mL in group A and B patients, respectively. Maximum plasma concentrations and area under the curves (AUC0-24 ) of idarucizumab in group A vs B, respectively, were 24 900 nmol/L vs 25 000 nmol/L and 76 600 nmol/h/L vs 68 000 nmol/h/L. Idarucizumab AUC0-24 increased by 38% in mild, 90% in moderate, and 146% in severe RI patients vs normal renal function. Hepatic impairment or geographical region had no relevant effect on idarucizumab PK. Idarucizumab immediately decreased unbound dabigatran concentration (<20 ng/mL). A linear correlation was observed between unbound dabigatran and diluted thrombin time and ecarin clotting time. Antidrug antibody titers were low (1-64 at day 30; 0-16 at day 90) and had no impact on idarucizumab PK and pharmacodynamics.

CONCLUSION

Idarucizumab PK in target patients was consistent with phase I data. Patient characteristics had no impact on PK, whereas RI increased the exposure of idarucizumab and dabigatran.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02104947.

Idarucizumab to revert the anticoagulant effect of dabigatran in traumatic acute subdural haematoma: a case report of first use in Latin America

BACKGROUND 

Direct oral anticoagulants (DOAC) are an attractive alternative over vitamin K antagonists. They have several advantages in primary and secondary prevention of thromboembolisms due to atrial fibrillation, as well as in prevention and treatment of thromboembolic venous disease. They have fast onset action, do not need laboratory controls in patients with normal renal function, and they have practically no interference with the patient's diet or medications. The strongest objection to their use was the lack of reversal agents that could be used in case of life-threatening haemorrhage or the need for emergency surgery. Dabigatran was the first DOAC to have its own specific reversal agent: idarucizumab, a monoclonal antibody.

CASE SUMMARY 

We report here the case of a patient undergoing treatment with dabigatran that suffered an expansive subdural haematoma secondary to a cranial injury. The condition was life-threatening and required emergency surgery. Anticoagulation was successfully reversed with idarucizumab.

DISCUSSION 

Emergency surgery in patients in treatment with DOAC is associated with an increased risk of bleeding. With the use of a specific antidote to block the action of the anticoagulant, as in the case of idarucizumab with dabigatran, the risk of complications during and after emergency surgery is reduced. This is the first case report with which the successful use of idarucizumab in Latin America is documented.

Reversal Strategies for Newer Oral Anticoagulants

Nonvitamin K antagonist oral anticoagulants have advantages compared with warfarin, but both types of anticoagulants come with uncertainty about how best to manage life-threatening bleeding events, urgent surgeries, and invasive procedures. Nurse practitioners and physician assistants may need to manage such emergency situations in the critical care setting. Achieving hemostasis quickly is key, and efforts to do so have relied mainly on blood products. Targeted reversal agents are in clinical development and one, idarucizumab, which reverses dabigatran anticoagulation, has been approved. Current options for managing events and urgent procedures in anticoagulated patients are discussed in this article, with a focus on specific reversal agents.

Rationale and design of a phase III safety trial of idarucizumab in children receiving dabigatran etexilate for venous thromboembolism

BACKGROUND

The incidence of venous thromboembolism (VTE) in children has been increasing. Anticoagulants are the mainstay of treatment but are associated with bleeding events that may be life-threatening. Idarucizumab is a fragment antigen-binding (fab) that provides immediate, complete, and sustained reversal of dabigatran's anticoagulant effects in adults.

OBJECTIVE AND METHODS

This phase III, open-label, single-arm, multicenter, multinational trial will assess the safety of idarucizumab in children participating in two ongoing trials investigating dabigatran etexilate. Eligible patients will be children with VTE (aged 0-≤18 years; n = ~5) with life-threatening or uncontrolled bleeding (group A), and children who require emergency surgery/urgent procedures for a condition other than bleeding (group B). Patients will receive idarucizumab up to 5 g as two consecutive intravenous infusions over 5-10 minutes each, as two 10-15-minute drips or as two bolus injections (15 minutes apart) and will be monitored for 30 days. The primary endpoint will be the safety of idarucizumab assessed by the occurrence of drug-related adverse events (including immune reactions) and all-cause mortality. Secondary endpoints will be the reversal of dabigatran anticoagulant effects assessed by changes in diluted thrombin time and ecarin clotting time, time to achieve complete reversal and the duration of the reversal and bleeding severity (group A). The formation of antidrug antibodies at 30 days post-dose and cessation of bleeding will also be assessed.

CONCLUSION

This study will report the safety of idarucizumab in children with VTE who require rapid reversal of the anticoagulant effects of dabigatran. Clinical trial registration: NCT02815670.

Evidence for Idarucizumab (Praxbind) in the Reversal Of the Direct Thrombin Inhibitor Dabigatran: Review Following the RE-VERSE AD Full Cohort Analysis

Idarucizumab is the first reversal agent approved for the direct thrombin inhibitor dabigatran. The authors summarize the findings from the clinical trial series and describe case reports, post-marketing data, and ongoing studies.

Safety, pharmacokinetics and pharmacodynamics of idarucizumab, a specific dabigatran reversal agent in healthy Japanese volunteers: a randomized study

BACKGROUND

Idarucizumab is a humanized monoclonal antibody fragment that specifically binds with high affinity to dabigatran.

OBJECTIVES

This study investigated the safety, tolerability and pharmacokinetics of idarucizumab alone and with dabigatran at steady state, and the effects of idarucizumab on dabigatran-induced anticoagulation.

PATIENTS/METHODS

This was a two-part, phase I, randomized, placebo-controlled, double-blind, rising-dose trial in healthy Japanese males. Part 1: 32 subjects (males) received single idarucizumab doses (1, 2, 4 or 8 g [n=6/dose group]) or placebo (n=2/dose group). Part 2: 48 males received dabigatran (220 mg bid) followed by idarucizumab (n=9/dose group) 1, 2, 4 or 5 g (2×2.5 g), or placebo (n=3/dose group). Anti-idarucizumab antibodies (ADAs) and idarucizumab effect on anticoagulation parameters (diluted thrombin time [dTT], ecarin clotting time [ECT], activated partial thromboplastin time [aPTT] and thrombin time [TT]) were assessed.

RESULTS

No adverse events were reported in subjects receiving idarucizumab. After single doses of idarucizumab (alone or at steady state of dabigatran), maximum plasma concentration was achieved around the end of each infusion. Mean all anticoagulation parameters fell below the upper limit of normal immediately after idarucizumab infusion in all dose groups; the effect was sustained at 4 and 2×2.5 g over the entire measurement period until 72 h. At 1- and 2-g doses, partial return of the anticoagulant effect occurred. Idarucizumab alone had no effect on coagulation parameters. Treatment-emergent ADAs occurred in 6/60 males receiving idarucizumab.

CONCLUSIONS

Idarucizumab infusion achieved immediate, complete and sustained reversal of dabigatran-induced anticoagulation in Japanese volunteers. Idarucizumab was well tolerated with no procoagulant effects. Trial registration number: ClinicalTrials.gov NCT02028780 (completed).

[State of the art: Direct oral anticoagulants and transfusion]

Direct oral anticoagulants (DOAC) are indicated for stroke prevention in atrial fibrillation and for the prevention and treatment of venous thromboembolism. As any anticoagulant, they are associated with a bleeding risk. Management of DOAC-induced bleeding is challenging. Idarucizumab, antidote for dabigatran, is currently available and is part of the therapeutic strategy, whereas antidotes for anti-Xa agents are under development. Activated or non-activated prothrombin concentrates are proposed, although their efficacy to reverse DOAC is uncertain. We propose an update on DOAC-associated bleeding management, integrating the availability of idarucizumab and the critical place of DOAC concentration measurements.

Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies

Aims

Idarucizumab, a humanized monoclonal anti‐dabigatran antibody fragment, is effective in emergency reversal of dabigatran anticoagulation. Pre‐existing and treatment‐emergent anti‐idarucizumab antibodies (antidrug antibodies; ADA) may affect the safety and efficacy of idarucizumab. This analysis characterized the pre‐existing and treatment‐emergent ADA and assessed their impact on the pharmacokinetics and pharmacodynamics (PK/PD) of idarucizumab.

Methods

Data were pooled from three Phase I, randomized, double‐blind idarucizumab studies in healthy Caucasian subjects; elderly, renally impaired subjects; and healthy Japanese subjects. In plasma sampled before and after idarucizumab dosing, ADA were detected and titrated using a validated electrochemiluminescence method. ADA epitope specificities were examined using idarucizumab and two structurally related molecules. Idarucizumab PK/PD data were compared for subjects with and without pre‐existing ADA.

Results

Pre‐existing ADA were found in 33 out of 283 individuals (11.7%), seven of whom had intermittent ADA. Titres of pre‐existing and treatment‐emergent ADA were low, estimated equivalent to <0.3% of circulating idarucizumab after a 5 g dose. Pre‐existing ADA had no impact on dose‐normalized idarucizumab maximum plasma levels and exposure and, although data were limited, no impact on the reversal of dabigatran‐induced anticoagulation by idarucizumab. Treatment‐emergent ADA were detected in 20 individuals (19 out of 224 treated [8.5%]; 1 out of 59 received placebo [1.7%]) and were transient in ten. The majority had specificity primarily toward the C‐terminus of idarucizumab. There were no adverse events indicative of immunogenic reactions.

Conclusion

Pre‐existing and treatment‐emergent ADA were present at extremely low levels relative to the idarucizumab dosage under evaluation. The PK/PD of idarucizumab appeared to be unaffected by the presence of pre‐existing ADA.