Disease Management

Vitamin K Antagonist Associated Bleeding

Bleeding is the most significant adverse effect with warfarin therapy, being directly related to the level of INR. Warfarin has a narrow therapeutic index and is influenced by drug interactions, notably anti-platelet drugs, and environmental factors. Treatment with VKAs increases the risk of major bleeding by 0.3–0.5 % per year and the risk of intracranial haemorrhage by around 0.2 % per year in comparison to controls. [Alquwaizani et al., 2013; Harter et al., 2015]

Risk factors for warfarin-related haemorrhage include intensity of anticoagulant effect, time within the therapeutic range, advanced age, and serious comorbid conditions including cancer, prior stroke, chronic kidney disease (CKD), liver dysfunction, arterial hypertension and alcohol abuse. [Alquwaizani et al., 2013; Harter et al., 2015]

Current Guidelines

Guidelines have been published by the American College of Chest Physicians (ACCP) for the perioperative management of antithrombotic therapy, which addresses the management of patients who are receiving VKA anticoagulant therapy and require an elective surgery or procedure. Assessment of perioperative bleeding risk is considered but no guidance on reversal of bleeding associated with VKAs is provided. [Douketis et al., 2012]

European Society of Cardiology (ESC) guidelines for the management of AF which were updated in 2016, include antithrombotic management of patients using VKA anticoagulant therapy. These guidelines include the use of NOACs for antithrombotic therapy (See Bleeding associated with NOACs; guidelines). Although bleeding risk is assessed, no guidance on reversal of bleeding with anticoagulants is provided. [Kirchhof et al., 2016]

American College of Chest Physicians (ACCP) guidelines for the evidence-based management of anticoagulant therapy include recommendations for the prevention and management of bleeding complications with VKAs. These include the use of four-factor (4F) PCCs (Prothrombin complex concentrates), rather than plasma for major bleeding associated with VKAs. [Holbrook et al., 2012]

European Society of Anaesthesiology guidelines for the management of severe perioperative bleeding recommends that patients on oral anticoagulant therapy should be given prothrombin complex concentrate (PCC) and vitamin K before any other coagulation management steps for treating severe perioperative bleeding. [Kozek-Langenecker et al., 2017]

European guidelines for the management of bleeding and coagulopathy following major trauma recommend the early use of PCC for the emergency reversal of VKAs. [Roussaint et al., 2016]

Guidelines for the reversal of antithrombotics in intracranial haemorrhage have recently been published by the Neurocritical Care Society and Society of Critical Care Medicine. [Frontera et al., 2016]

Prothrombin Complex Concentrates

A number of randomised controlled trials (RCTs) have been conducted on the use of PCCs for VKA reversal. PCCs contain varying amounts of vitamin K dependent coagulation factors II, VII, IX and X. Literature reports suggest that 3-PCC may be less effective than 4-PCC in warfarin reversal, due to a lower factor VII content. [DeAngelo et al., 2017; Holt et al., 2018]

A prospective study of 43 patients requiring emergency VKA reversal (26 required interventional procedures and 17 experienced acute bleeding) received an infusion of 4-factor (4F) PCC which contains coagulation factors II, VII, IX, and X, and the anticoagulant proteins C and S. PCC infusion at a median rate of 7.5 mL/min (188 IU/min), produced a decline in INR to <1.3 in 93% of patients. Normalisation of INR was sustained for 48 hr post PCC infusion with median INR values of 1.2–1.3 being attained. There was a marked increase in coagulation factors II, VII, IX, and X and the thrombo-inhibitor proteins C and S following PCC infusion within 30 min, with levels of these coagulation factors and proteins C and S remaining at normal or near normal levels over the next 48 hours. One serious adverse event (SAE) possibly related to PCC was a suspected pulmonary embolism resulting in the death of a patient (aged 70 years with metastatic cancer), while five other SAEs were judged to be unrelated to PCC. [Pabinger et al., 2008]

Rapid infusion of PCC, with infusion rates varying from 2.0 to 40.0 mL/min (median of 7.5 mL/min), did not compromise its safety or efficacy, when used for emergency VKA reversal in 43 patients. [Pabinger 2010]

A retrospective study of VKA reversal using PCC treatment evaluated case notes from 50 surgical patients requiring reversal of an oral VKA (n=12) or with severe coagulopathic perioperative bleeding (n=38). Following PCC infusion in VKA reversal patients baseline INR was significantly reduced from 2.8±0.2 to 1.5±0.1 (p<0.001). In bleeding patients, PCC infusion significantly reduced the INR from 1.7±0.1 at baseline to 1.4±0.1 (p<0.001), with no major bleeding occurring during subsequent surgery. [Schick et al., 2009]

A randomised study of PCC and fresh frozen plasma (FFP) for the reversal of VKAs in 40 patients undergoing cardiopulmonary bypass surgery showed that 15 min after surgery significantly more patients reached INR target with PCC (7/16) than FFP (0/15; p=0.007). This difference was not apparent 1 hour after surgery. The safety profile was good for both treatment groups, with minor bleeding reported for two cases in the FFP group. [Demeyere et al., 2010]

A three-factor (3F) PCC was effective in the emergency reversal of VKA anticoagulation (warfarin or acenocoumarol) in 46 patients with intracranial haemorrhage. Patients had a median INR at presentation of 3.5 (INR range 2–9), and at 30 minutes following PCC infusion median INR values were significantly reduced to 1.3 (range, 0.9–3; p<0.0001). INRs declined to <1.5 in 75% of patients – the primary end-point of the study. [Imberti et al., 2011]

Two RCTs compared 4F-PCC (containing vitamin K–dependent factors plus proteins C and S) with plasma in patients receiving VKAs and presenting with acute major bleeding [Sarode et al., 2013 {NCT00708435}], or in need of urgent surgical or invasive procedures. [Goldstein, et al., 2015 {NCT00803101}]

A randomised, plasma-controlled, phase III study of 4F-PCC in 202 patients on VKAs presenting with acute major bleeding showed that 4F-PCC was non-inferior to plasma for haemostatic efficacy. Effective haemostasis was achieved in 72.4% of patients receiving 4F-PCC and 65.4% receiving plasma (difference=7.1%; 95% CI, –5.8 to 19.9). 4F-PCC was superior to plasma for rapid INR reduction (INR ≤1.3 at 30 min after end of infusion) with 62.2% of patients receiving 4F-PCC and 9.6% receiving plasma achieving this goal (difference=52.6%; 95% CI, 39.4 to 65.9). The safety profile was similar between treatment groups with 64.1% (66 of 103) in the 4F-PCC group and 65.1% (71 of 109) in the plasma group of patients experiencing ≥1 adverse event. Thromboembolic AEs were reported in 8 patients in the 4F-PCC group and 7 in the plasma group. [Sarode et al., 2013 {NCT00708435}]

4F-PCC was superior to plasma for the primary endpoint of haemostasis (90% vs. 75%; difference = 14.3%, 95% CI, 2.8–25.8; p=0·014) in the second randomized controlled trial in 168 patients on VKAs needing urgent reversal prior to surgery or an invasive procedure. [Goldstein et al 2015] The co-primary endpoint of rapid INR reduction (INR ≤1.3 at 30 min after end of infusion) also showed superiority of 4F-PCC over plasma (55% vs. 10%; difference = 45.3%, 95% CI, 31.9–56.4; p<0·0001). The safety profile was generally similar in both groups: 56% of patients receiving 4F-PCC had adverse events compared with 60% patients receiving plasma; fluid overload occurred less frequently in patients receiving 4F-PCC (3% vs 13%). [Goldstein, et al., 2015]

An analysis of pooled data from these two studies [Sarode et al., 2013; Goldstein, et al., 2015] showed that 7.3% (14 of 191) patients in the 4F-PCC group and 7.1% (14 of 197) in the plasma group developed thromboembolic events after VKA reversal (risk difference 0.2%; 95% CI, -5.5% to 6.0%). Serious adverse events were reported in 16 patients, 8 in each group. [Milling et al., 2016] Fluid overload events occurred more frequently in the plasma group than the 4F-PCC group (25 [12.7%] and 9 [4.7%], respectively).

A pharmacovigilance study of the long-term safety (15 years) and efficacy of a 4F-PCC showed that the incidence of thromboembolic events was approximately one in 31,000, with 21 thromboembolic events possibly related to 4F-PCC administration in ~647,250 standard applications of the 4F-PCC being reported. No cases of viral transmission or heparin-induced thrombocytopaenia were documented. The incidence rate of thromboembolic events is comparable to those observed with other 4F-PCCs. [Hanke et al., 2013]

A systematic review of reversal of VKA treatment by PCCs in bleeding and non-bleeding patients identified four RCTs [Boulis et al., 1999; Demeyere et al., 2010; Sarode et al., 2013; Majeed et al., 2014] with a total of 453 participants. Three of the trials provided data on mortality, with a meta-analysis of the effect of PCCs on overall mortality showing no statistical effect (Relative Risk (RR) = 0.93, 95% CI, 0.37–2.33) although the quality of evidence was judged to be very low due to the high risk of bias and underpowered nature of the trials reviewed. [Johansen et al., 2015]

A recent meta-analysis of 5 randomised and 8 observational studies which compared PCC with fresh frozen plasma (FFP) for warfarin reversal concluded that PCC use significantly reduced all-cause mortality (OR=0.56, 95 % CI, 0.37–0.84, p=0.006), produced a more rapid INR reduction (OR=10.80, 95 % CI, 6.12–19.07), with less volume overload (OR=0.27, 95 % CI, 0.13–0.58) and without an increased risk of thromboembolic events (OR=0.91, 95 % CI, 0.44–1.89). [Chai-Adisaksopha et al., 2016]

The effect of a simplified dosing protocol (RAPID) for 4F-PCC (25 IU/kg) was assessed in a retrospective audit of 17 patients with warfarin-associated bleeding. The intervention involved standardisation of the initial dose and simplification of dose calculations. Using the protocol, 15 patients with warfarin-associated bleeding (88.2%) achieved a post-treatment INR ≤1.5; with reversal of warfarin-associated bleeding within 8 h reported in 14 (82.4%). Compared with the retrospective cohort, RAPID was associated with a reduced administration interval (mean 37.7 vs 76 min, p=0.031) and an increased proportion of patients treated within 30 min (58.8 vs 6.7%, p=0.009). [Appleby et al., 2016]

The efficacy of PCC versus fresh frozen plasma has been further assessed in a retrospective chart review of 120 patients with traumatic intracranial haemorrhage. This study compared outcomes in patients with INR ≤ 1.4 after receiving activated PCC (aPCC) versus FFP within 24 hours and reported that INR was more effectively reversed in patients treated with aPCC (90.3%) versus FFP (69.7%; p=0.029). Median time to reversal (hours) was also significantly shorter with PCC vs FFP (3.75 hours vs 6.75 hours; p=0.003). Mortality rates and incidences of thrombosis did not differ between the two treatment groups. [Carothers et al., 2018]

Vitamin K & Plasma

Vitamin K

In French clinical practice guidelines, vitamin K is advocated for VKA overdose when the INR is above 6, and when bridging therapy with heparin for an elective surgical procedure is required (in patients with an INR >1.5 the evening before the procedure). It is also recommended in cases of severe bleeding, regardless of the initial INR. [Pernod et al., 2010]

American College of Chest Physicians (ACCP) guidelines suggest the administration of oral vitamin K for patients taking VKAs with INRs >10.0 and with no evidence of bleeding, but not if the INR is between 4.5 and 10. [Holbrook et al., 2012]

Reversal of anticoagulation with vitamin K is achieved more rapidly with intravenous (iv) rather than oral administration. However, in an emergency situation vitamin K treatment alone is not sufficiently rapid as it takes 4–6 hours for INR normalisation following iv administration of vitamin K. [Levy et al., 2008]

Plasma

Use of fresh frozen plasma (FFP) for reversing the effects of VKA anticoagulation is limited by the volume of plasma required to effect complete reversal. [Evans et al., 2001]

Many current guidelines, including European and American guidelines, consider that human plasma is no longer the treatment of choice to reverse VKA anticoagulation. [Board of the German Medical Association 2009; Pernod et al., 2010; Keeling et al., 2011; Holbrook et al., 2012; Roussaint et al., 2016; Kozek-Langenecker et al., 2017]

Two phase III trials comparing plasma with 4F-PCC for the rapid reversal of VKAs or in need of urgent surgical or invasive procedures showed that 4F-PCC was superior to plasma for rapid INR reversal [Sarode et al., 2013; Goldstein, et al., 2015] and effective haemostasis. [Goldstein, et al., 2015] These, and other studies, are discussed in more detail within the PCCs section. 

NOACs and Associated Bleeding

In common with all anticoagulants, haemorrhage, notably gastrointestinal bleeding and intracranial haemorrhage, is the primary adverse effect with both Xa inhibitors (rivaroxaban, apixaban, edoxaban) and direct IIa inhibitors (dabigatran). [Alquwaizani et al., 2013; Harter et al., 2015]

A recent analysis of 61 patients with non-traumatic NOAC-associated intracerebral haemorrhage reported a mortality rate of 28% at 3 months, with substantial haematoma expansion occurring in 38% (17 of 45) of evaluated patients, and new or increased intraventricular haemorrhage being observed in 18% (8 of 45) of patients. [Purrucker et al. 2016]

Current Guidelines

The ESC guidelines for management of AF, published in 2012, include the use of NOACs (dabigatran, rivaroxaban or apixaban) for antithrombotic therapy. [Camm et al., 2012] Practical guidance on how to improve the implementation of the ESC guidelines for anticoagulation in AF using NOACs has recently been published. [Kirchhof et al., 2016]

Consensus European guidelines for antithrombotic therapy in non-valvular AF patients presenting with acute coronary syndrome and/or undergoing percutaneous coronary or valve interventions has also recently been published. [Lip et al., 2014] Combined guidelines from multiple US organisations published in 2014 for the management of patients with AF include recommendations for risk-based anticoagulation therapy, with options for anticoagulation of non-valvular AF including the use of warfarin (INR 2.0–3.0), dabigatran, rivaroxaban or apixaban. [January et al., 2014]

Although these detailed guidelines discuss the risk of bleeding with NOACs, strategies for the reversal of bleeding associated with NOACs are not discussed, and specific reversal agents for NOACs in the event of major bleeding were not available at the time of publication. Some guidance is available for the reversal of oral IIa and factor Xa inhibitors, [Camm et al., 2012; Radaelli et al., 2015; Steffel et al., 2018]. Idarucizumab (Praxbind^®) has since been approved for specific reversal of the anticoagulant action of dabigatran [European Medicines Agency, 2015a; FDA, 2015] as well as andexanet alfa for the reversal of rivaroxaban and apixaban [FDA, 2018].

An Anticoagulation Education Task Force White Paper on the management of reversal of direct oral anticoagulants in emergency situations was recently published. Recommendations are provided for situations when a reversal agent is definitely required e.g. life-threatening bleeding, bleeding into an organ or closed space, persistent bleeding despite local haemostatic measures, and the need for urgent interventions and/or interventions that carry a high bleeding risk. Conditions when a reversal agent may be helpful or is generally not needed are also considered. [Ageno et al., 2016] An algorithm for the management of bleeding and urgent surgery in patients receiving NOACs is shown in the Figure below.

Figure 4. Algorithm for management of patients treated with a NOAC who present with mild, moderate–severe, or life-threatening bleeding, or who require emergency surgery.
*Idarucizumab is the preferred treatment for dabigatran reversal [Ageno et al., 2016]

European Heart Rhythm Association (EHRA) practical guidance on the use of NOACs in patients with non-valvular AF includes the management of bleeding complications with these anticoagulants. A range of measures are suggested to combat bleeding associated with NOACs including the use of prothrombin complex concentrate (PCC) for life threatening bleeding. [Steffel et al., 2018]

European guidelines for the management of bleeding and coagulopathy following major trauma suggest the measurement of substrate-specific anti-factor Xa activity in patients treated or suspected of being treated with oral inhibitors of factor Xa (rivaroxaban, apixaban or edoxaban). High dose PCC (25 to 50 U/kg) is suggested for the reversal of rivaroxaban, apixaban and edoxaban if bleeding is life threatening. [Roussaint et al., 2016]

Proposals from a working group on perioperative haemostasis on the management of patients on long-term treatment with NOACs (dabigatran and rivaroxaban) suggest either activated prothrombin complex concentrate (aPCC) 30–50 U/kg) or non-activated PCC (50 U/kg) as first line therapy for serious bleeding. [Pernod et al., 2013; Faraoni et al., 2015] 

Prothrombin Complex Concentrates

PCCs potentially have a role in the reversal of the anticoagulant effect of NOACs, although clinical data supporting this use are generally lacking. [Pengo et al., 2011; Ghanny et al., 2012; Kaatz et al., 2012; Roussaint et al., 2016; Steffel et al., 2018]

PCCs were recently recommended for the reversal of life-threatening bleeding by the Anticoagulation Education Task Force. [Ageno et al., 2016]

Preclinical studies

Animal models have illustrated the potential of PCCs to reverse the effects of NOACs: 

• A porcine model of trauma showed that PCCs were effective in reducing the anticoagulant effects of dabigatran, as was idarucizumab (aDabi-Fab, [Das et al., 2015]) the specific reversal agent for dabigatran, which was the most effective agent tested. [Grottke et al., 2014]
• Rabbit models of acute bleeding have been used to assess the effect of reversal of a 4F-PCC following administration of edoxaban [Herzog et al., 2015a], rivaroxaban [Herzog et al., 2015b], dabigatran [Herzog et al., 2014] or apixaban [Herzog et al., 2015c]. The 4F-PCC was effective in significantly reducing edoxaban-associated haemorrhage [Herzog et al., 2015a]; reducing bleeding to control levels following administration of rivaroxaban [Herzog et al., 2015b]; reversing excessive bleeding following dabigatran administration whilst retaining the protective anticoagulation activity of dabigatran [Herzog et al., 2014]; and reducing bleeding time and volume following administration of apixaban. [Herzog et al., 2015c]
• Reversal of dabigatran-induced bleeding by six different coagulation factor concentrates comprising 3F-PCC, 4F-PCCs, an activated PCC and rVIIa was demonstrated in a rat-tail bleeding model. These coagulation factor concentrates significantly decreased (P<0.001) the prolonged bleeding time induced by dabigatran over 30 min, although none of the coagulation factor concentrates had a concomitant effect on coagulation assays. [van Ryn et al., 2014]
• In a porcine polytrauma model a 4F-PCC was effective in treating blood loss following dabigatran administration. Blood loss was significantly lower with 4F-PCC administered at 50 U/kg (1,749 ± 47 ml) or 100 U/kg (1,692 ± 97 ml) compared to dabigatran treated controls (3,855 ± 258 ml). [Honickel et al., 2015] 

Studies in healthy human volunteers

A number of phase I studies have demonstrated the potential of PCCs for reversing the effects of anticoagulants in humans:

• Twelve healthy male volunteers received rivaroxaban or dabigatran for 2.5 days, followed by either a 50 IU/kg bolus of 4F-PCC (human plasma-derived factors II, VII, IX and X, as well as antithrombin and proteins C and S) or a saline placebo. After a washout period, the procedure was repeated with the alternate anticoagulant, again followed by 4F-PCC or saline. 4F-PCC completely reversed the anticoagulant effects of rivaroxaban, but had no influence on the effects of dabigatran. [Eerenberg et al., 2011]
• Thirty-five healthy adults received rivaroxaban for 4 days, and on day 5 received a 50 IU/kg bolus of either 3F-PCC (including factors II, IX and X), 4F-PCC (including factors II, VII, IX and X) or saline. Both PCCs showed at least partial reversal of rivaroxaban’s actions: the thrombin generation effect of rivaroxaban was more effectively reversed by 3F-PCC than 4F-PCC, while the increase in prothrombin time with rivaroxaban was more effectively reversed by 4F-PCC than 3F-PCC. [Levi et al., 2014]
• One hundred and ten healthy adults took part in a study in which they received a single dose of edoxaban followed by different doses of 4F-PCC (including factors II, VII, IX and X) or placebo. The reversal of edoxaban’s effects was observed in a dose-dependent manner, with the 50 IU/kg dose providing complete reversal of the effect on bleeding duration and endogenous thrombin potential, and partial reversal of the increased prothrombin time. [Zahir et al., 2015]
• The reversal of apixaban’s effects was investigated in a study of six healthy volunteers, given 25 IU/kg or 37.5 IU/kg doses of 4F-PCC, or saline placebo, following 3 days of apixaban treatment. Both doses of 4F-PCC at least partially restored coagulation parameters, but not to pre-apixaban levels, suggesting that the doses used were too low to fully reverse the anticoagulation effect of apixaban. [Cheung et al., 2015] Corresponding investigations by the same research group into lower doses of 4F-PCC (or placebo) on the actions of rivaroxaban in six healthy volunteers were undertaken. Results showed that both doses restored prothrombin time prolongation, but that 25 IU/kg was not different from placebo in restoring endogenous thrombin potential or thrombin generation, while 37.5 IU/kg partially restores both measures. [Barco et al., 2016]

Reports from bleeding episodes in clinical practice

A retrospective review of 18 patients treated with direct factor Xa inhibitors (n=16 with rivaroxaban; n=2 with apixaban) presenting with traumatic and spontaneous intracranial haemorrhage summarised treatment with 4F-PCC for the reversal of anticoagulation. Favourable outcomes at 90 days were observed in one third of patients (n=6). Worsening of bleeding was found in one patient; six patients (33.3%) died in hospital (four following family withdrawal of care; two due to pneumonia); and one patient had a thromboembolic complication. The use of 4F-PCC was considered to be safe. [Grandhi et al., 2015]

Analysis of 1082 bleeding events in a registry of rivaroxaban patients identified six patients whose serious bleeding events were treated with PCC (of unspecified composition); five of these showed stabilisation of haemorrhage, and four were without sequelae at 90 days post-bleeding. The patient whose haemorrhage was not stabilised was judged to have had too low a dose (18 IU/kg) and had a 5.5 hour delay from admission to PCC application; the patient with sequelae by 90 days died of septic pneumonia on day 16. [Beyer-Westendorf et al., 2014]

A recent review of PCCs and activated PCCs for the reversal of dabigatran-induced anticoagulation concluded that their use was warranted in patients with life-threatening haemorrhage if idarucizumab was unavailable. [Grottke et al., 2016]

Plasma & rVIIa

Plasma

Use of fresh frozen plasma (FFP) for reversing the effects of VKA anticoagulation is limited by the volume of plasma required to effect complete reversal. [Evans et al., 2001; Refaai et al., 2015]

Many current guidelines, including European and American guidelines, consider that human plasma is no longer the treatment of choice to reverse VKA anticoagulation. [German Medical Association 2009; Pernod et al., 2010; Keeling et al., 2011; Holbrook et al., 2012; Roussaint et al., 2016; Kozek-Langenecker et al., 2017]

Two phase III trials comparing plasma with 4F-PCC for the rapid reversal of VKAs or in need of urgent surgical or invasive procedures showed that 4F-PCC was superior to plasma for rapid INR reversal [Sarode et al., 2013; Goldstein, et al., 2015] and effective haemostasis. [Goldstein, et al., 2015] These, and other studies are discussed in more detail in the Prothrombin complex concentrates (PCCs) section.

rVIIa

Off-label use by the administration of rVIIa may be considered for bleeding which cannot be stopped by conventional means and/or there is a failure of comprehensive coagulation therapy. [Kozek-Langenecker et al., 2017] Although there is no formal review of clinical experience for NOAC reversal, anecdotal evidence for the use of rVIIa is inconsistent. [Lazo-Langner et al., 2013]

Idarucizumab

Idarucizumab is a humanised monoclonal Fab antibody fragment that specifically binds to dabigatran, thereby neutralising the anticoagulant. [Das & Liu 2015; European Medicines Agency 2015b] Idarucizumab recently received fast-track marketing authorisation from the European Medicines Agency (EMA) as a specific reversal agent for dabigatran etexilate when rapid reversal of anticoagulation is required. [European Medicines Agency 2015a]

EMA approval for idarucizumab was based on data from three placebo-controlled phase I RCTs involving 283 subjects [European Medicines Agency 2015b] including a study in healthy volunteers [Glund et al., 2015] (NCT01688830) and the RE-VERSE AD trial (NCT02104947) [Pollack et al., 2015] for the reversal of the factor IIa inhibitor, dabigatran.

The RE-VERSE AD trial included 301 patients with uncontrolled bleeding (group A), and 202 patients requiring an urgent procedure (group B), across 173 sites in 39 countries. All patients (100%) achieved complete reversal of the anticoagulant effect of dabigatran determined by diluted thrombin time (dTT) or ecarin clotting time (ECT) in the first 4 hours after administration of idarucizumab. {Figure 5 below} Reversal of anticoagulation was rapid and was independent of age, sex, renal function and dabigatran concentration at baseline. The estimated 90-day mortality rate was 18.8% in group A and 18.9% in group B. Thrombotic events were reported within 90 days in 14 patients in group A (4.8%) and in 15 patients in group B (6.8%). There were no serious adverse safety signals with most adverse events appearing to be worsening of an index event or a coexisting condition. [Pollack et al., 2017]

Figure 5. Reversal, by idarucizumab, of dabigatran-induced clotting time prolongation determined by dTT in (A) 293 patients with uncontrolled bleeding (group A) and (B) 195 patients requiring an urgent procedure (group B) from the RE-VERSE AD trial [Pollack et al., 2017].

Andexanet Alfa

Andexanet alfa is a recombinant protein that when bound, inactivates direct factor Xa inhibitors. [Das & Liu 2015] The effect of andexanet alfa for the reversal of the factor Xa inhibitors, apixaban (5 mg twice daily) or rivaroxaban (20 mg daily) was assessed in a placebo-controlled trial of healthy volunteers (aged 50–75 years) using the mean percentage change in anti–factor Xa activity (which is a measure of factor Xa inhibition by the anticoagulants) as the primary outcome. Adexanet alfa significantly reduced anti-factor Xa activity, compared to placebo, in participants treated with either apixaban (94±2% vs.21±9%; p<0.001) or rivaroxaban (92±11% vs. 18±15%; p<0.001). No serious or severe adverse events were reported, with thrombotic events being absent. All adverse events relating to andexanet administration were mild. [Siegal et al., 2015]

The single-arm open-label ANNEXA-4 trial in 228 patients experiencing acute bleeding whilst taking a factor Xa inhibitor (of which 132 patients were adjudicated for efficacy), has released early results demonstrating that andexanet alfa rapidly reversed factor Xa activity when administered as a bolus, which was sustained when followed by a 120-minute infusion. Haemostasis was achieved in 83% of these patients, whilst rates of thrombotic events (11%) and mortality (12%) were consistent with earlier study findings. Andexanet alfa gained approval from the U.S. Food and Drug Administration in 2018 and is currently under review by the European Medicines Agency. [FDA, 2018; Portola Pharmaceuticals Press Release, 2018]

Ciraparantag (Arapazine, PER977)

Ciraparantag (arapazine, PER977) is a small water-soluble molecule which binds to direct inhibitors of factor Xa and IIa, and also to heparin-based anticoagulants, thereby antagonising their effects. [Das & Liu 2015; Siegal, 2015; Milling Jr and Kaatz, 2016] The safety and efficacy of ciraparantag (5–300 mg iv) was studied following its administration to healthy people in a double-blind placebo-controlled trial who were treated with a 60 mg oral dose of the factor Xa inhibitor, edoxaban. The anticoagulant effect of edoxaban, and its reversal by ciraparantag was assessed by whole-blood clotting time (WBCT). Edoxaban increased the mean WBCT by 37% from baseline values, with a single iv dose of ciraparantag (100–300 mg) administered 3 hours post edoxaban reducing the WBCT to within 10% of baseline values in ≤10 min. In contrast, a comparable level of WBCT in patients receiving placebo was reached in approximately 12 to 15 hours. Adverse events potentially related to ciraparantag were mild. [Ansell et al., 2014] A further dose-escalation study by the same group (NCT01826266) reported that 100–300 mg ciraparantag restored haemostasis within 10–30 mins, and sustained this for 24 hours in 83 healthy subjects. [Ansell et al., 2017; US National Library of Medicine 2018)