Anne-Laure Sennesael

Appropriateness of Prescribing Dabigatran Etexilate and Rivaroxaban in Patients With Nonvalvular Atrial Fibrillation A Prospective Study

Background: Direct oral anticoagulants have been developed to address some of the drawbacks of vitamin-K antagonists. However, special attention should be given when using these drugs, especially in patients with renal insufficiency, questionable compliance, and those at high risk of bleeding. Objective: To evaluate the appropriateness of prescribing dabigatran etexilate (DE) and rivaroxaban in patients with nonvalvular atrial fibrillation (NVAF) in real-life clinical practice. Methods: This was a prospective study that included patients presenting to a teaching hospital from April to mid-October 2013, who were taking rivaroxaban or DE for NVAF. Appropriateness of prescribing was evaluated using 9 of the 10 criteria of the Medication Appropriateness Index. The primary outcome measure was the prevalence of inappropriate prescribing. Secondary outcome measures included (a) categories of inappropriateness, (b) prevalence of adverse drug events, and (c) interventions made by a clinical pharmacist to optimize prescribing. Results: A total of 69 patients were evaluated; 16 patients (23%) had 1 inappropriate criterion, and an additional 18 (26%) had more than 1 inappropriate criterion. The most frequent inappropriate criteria were inappropriate choice (28% of patients), wrong dosage (26%), and impractical modalities of administration (26%). An adverse event (AE) was found in 51% of patients (including 8 patients with transient ischemic attack/stroke). The clinical pharmacists performed 48 interventions, and 94% were accepted by the physician. Conclusions: Inappropriate use of DE and rivaroxaban in patients with NVAF is frequent and possibly leads to AEs. Reinforcing education of health care professionals and patients is needed. Collaboration with clinical pharmacists can contribute to better use.

Does the Russell Viper Venom time test provide a rapid estimation of the intensity of oral anticoagulation? A cohort study

BACKGROUNDnDilute Russell Viper Venom Time (DRVV-T) might be useful in urgent settings for screening patients on Non-VKA Oral Anticoagulants (NOACs).nnnAIMnTo compare the accuracy of DRVV-T with gold standard assays for the assessment of pharmacodynamics of dabigatran, rivaroxaban and vitamin K antagonist (VKA) in plasma samples from patients.nnnMETHODSnSixty rivaroxaban, 48 dabigatran and 50 VKA samples from patients were included. DRVV-T was performed in all groups using STA®-Staclot®DRVV-Screen and -Confirm. For NOACs, PT and aPTT were performed using different reagents while plasma drug concentrations were measured by liquid mass-spectrometry (LC-MS/MS). For VKA, INR was performed using RecombiPlasTin 2G®.nnnRESULTSnFor NOACs, correlations between calibrated STA®-Staclot®DRVV-Confirm and LC-MS/MS (rs=0.88 and 0.97 for rivaroxaban and dabigatran, respectively) were higher than the ones obtained with STA®-Staclot®DRVV-Screen (rs=0.87 and 0.91), PT (rs=0.83 to 0.86) or aPTT (rs=0.84 to 0.89). Bland Altman analyses showed that calibrated DRVV-T methods tend to overestimate plasma concentrations of NOACs. ROC curves revealed that cut-off to exclude supra-therapeutic levels at Ctrough (i.e. 200ng/mL) are different for dabigatran and rivaroxaban. Neither STA®-Staclot®DRVV-Screen nor -Confirm correlated sufficiently with the intensity of VKA therapy (rs=0.35 and 0.52).nnnCONCLUSIONSnSTA®-Staclot®DRVV-Confirm provides a rapid estimation of the intensity of anticoagulation with rivaroxaban or dabigatran without specific calibrators. At Ctrough, thresholds for rivaroxaban and dabigatran can be used to identify supra-therapeutic plasma level. However, this test cannot differentiate the nature of the NOACs. The development of a point-of-care device optimising this method would be of particular interest in emergency situations.

An optimized dRVVT-based assay to estimate the intensity of anticoagulation in patients treated with direct oral anticoagulants

BACKGROUNDnThe dilute Russells viper venom time (dRVVT) has been suggested for the assessment of the intensity of anticoagulation of all direct oral anticoagulants (DOACs). This study aimed to compare the performance of an optimized liquid-stable dRVVT-based DOAC assay (DRVV-DOAC) on clinical samples before and after mixing these with normal pooled plasma (NPP).nnnMETHODSnForty-one apixaban, 25 dabigatran, 56 rivaroxaban and 49 vitamin K antagonists (VKAs) plasma samples were included for retrospective analysis. Plasma DOAC concentrations were determined by liquid chromatography coupled with tandem mass-spectrometry. INR was determined for all VKA samples. DRVV-DOAC was performed with an original ready-to-use reagent (Haematex Research™) where plasma samples were tested neat and in a 1:1 mix with NPP.nnnRESULTSnPlasma concentrations ranged from 1 to 406ng/ml for apixaban, 0 to 386ng/ml for dabigatran and 0 to 719ng/ml for rivaroxaban. INR ranged from 2.2 to 6.1. DRVV-DOAC correlated well with plasma concentrations (r2=0.70, 0.94, 0.63 (non-mixed procedure) and 0.77, 0.97, 0.86 (mixed procedure) for apixaban, dabigatran and rivaroxaban, respectively). DRVV-DOAC measurements in the normal range ruled out dabigatran and rivaroxaban concentrations above 30 and 50ng/ml, but performance was lower for apixaban. DRVV-DOAC was sensitive to VKA samples but poorly reflected INR values. When VKA samples were mixed with NPP, DRVV-DOAC measurements decreased to values close to baseline clotting time.nnnCONCLUSIONSnDRVV-DOAC is a quick method which showed increased sensitivity compared with other phospholipid-rich dRVVT reagents already investigated. Mixing samples with NPP improved the specificity but reduced sensitivity, especially for apixaban.

Preventability of serious thromboembolic and bleeding events related to the use of oral anticoagulants: a prospective study

To determine the preventability of serious adverse drug reactions (ADRs) related to the use of direct oral anticoagulants (DOACs), and to explore contributing factors to preventable ADRs. Results were compared with vitamin K antagonists (VKAs).

Rivaroxaban plasma levels in patients admitted for bleeding events: insights from a prospective study

BackgroundSerious bleeding events have been frequently described in patients taking direct oral anticoagulants (DOAC). In secondary analyses of phase 3 trials, DOAC plasma concentrations were shown to correlate with bleeding outcomes. This study aimed to describe rivaroxaban plasma levels in patients admitted to the emergency department (ED) for bleeding events. For each patient, risk factors for experiencing bleeding events were also investigated.MethodsThis analysis was part of an observational study conducted in the ED of two teaching hospitals. Plasma samples from 10 rivaroxaban-treated patients admitted for bleeding events were collected. Rivaroxaban plasma concentrations were determined by calibrated chromogenic anti-Xa assay. The measured rivaroxaban levels were then extrapolated at trough using a published population pharmacokinetic (PopPK) model, and compared to on-therapy ranges observed in large clinical trials. For each patient, clinical, medication and ABCB1 genotype data were collected.ResultsRivaroxaban measurements varied from 5 to 358xa0ng/ml, with a post-intake delay ranging from 9 to 38xa0h. At trough, estimated plasma concentrations were between 12 and 251xa0ng/ml (median value 94xa0ng/ml). Four patients had higher-than-expected rivaroxaban levels. Inadequate dose regimen, excessive alcohol consumption and lack of treatment reassessment were observed in several patients. Half of patients were taking ≥1 drug with potential pharmacokinetics interactions (e.g. amiodarone, diltiazem), while half of patients were taking ≥1 drug increasing the risk of bleeding. All 3 patients with available genotyping data and higher-than-expected rivaroxaban levels were heterozygous or homozygous mutated for the ABCB1 1236Cu2009>u2009T, 2677Gu2009>u2009T, 3435 Cu2009>u2009T and rs4148738 single nucleotide polymorphisms (SNP).ConclusionsRivaroxaban patients admitted to the ED for bleeding events showed highly variable plasma concentrations. This analysis underlines the usefulness of rapid DOAC measurement and the value of PopPK models to estimate concentrations at trough in a context where the post-intake delay is unmanageable. Close patient follow-up, including renal function assessment and drug interactions review, is essential for bleeding risk minimization.

Effect of ABCB1 genetic polymorphisms on the transport of rivaroxaban in HEK293 recombinant cell lines

Direct oral anticoagulants (DOAC) are substrates for the ABCB1 transporter (also called P-glycoprotein), an active efflux pump. ABCB1 polymorphisms have been previously reported to influence the pharmacokinetics of several drugs such as immunosuppressants and tyrosine kinase inhibitors. Recently, in vivo studies have suggested that genetic variants might contribute to the inter-individual variability in DOAC plasma concentrations. Therefore, we evaluated the in vitro effect of the most common coding ABCB1 single nucleotide polymorphisms (SNP), 1236u2009Cu2009>u2009T-2677Gu2009>u2009T-3435Cu2009>u2009T, and the coding ABCB1 1199u2009Gu2009>u2009A SNP on the transport activity towards rivaroxaban. HEK293 cells were transfected to overexpress the ABCB1 wild-type (1236C-2677G-3435C, 1199u2009G) or variant proteins (1236C-2677G-3435T, 1236T-2677T-3435T or 1199u2009A). ABCB1 expression decreased the intracellular accumulation of rivaroxaban, when compared to control cells. This confirms the involvement of ABCB1 in the active transport of rivaroxaban. However, the ABCB1 1236u2009Cu2009>u2009T-2677Gu2009>u2009T-3435Cu2009>u2009T and 1199u2009Gu2009>u2009A SNPs had no significant influence on the intracellular accumulation of rivaroxaban when compared to the wild-type protein. These results suggest that the ABCB1 coding SNPs investigated in the present study are unlikely to contribute to the inter-individual variability in rivaroxaban plasma concentrations.

Implementing a screening tool to improve prescribing in hospitalized older patients: a pilot study.

Background The use of STOPP–START criteria during hospitalization reduced inappropriate medications in randomized controlled trials. Objective To evaluate whether the implementation of a screening tool (short version of STOPP–START criteria) in routine geriatric practice reduces potentially inappropriate medications (PIM) and potential prescribing omissions (PPO) at discharge. Methods We conducted a retrospective interrupted time series analysis. Four periods were selected between February and September 2013: (1) baseline situation; (2) screening tool made available to physicians; (3) 3xa0months later; (4) weekly meetings with junior doctors and a clinical pharmacist to review treatments according to the tool. The primary outcome was the proportion of patients with prescribing improvement from admission to discharge. Results We included 120 patients (median age 85xa0years). The prevalence of PIMs and PPOs on admission was 56% (67/120) and 51% (61/120) respectively. Hospitalization improved prescribing appropriateness in 49% of patients with PIMs (33/67) and 39% of patients with PPOs (24/61). The use of the screening tool by way of multidisciplinary meetings was a predictor of PIMs reduction at discharge. Conclusions The sole distribution of a screening tool in a geriatric unit did not reduce PIMs and PPOs. Multidisciplinary meetings to review treatments should be encouraged.

Partial economic evaluation of clinical pharmacy interventions on the prescription of direct oral anticoagulants in a teaching hospital

Background Potential inappropriate use of direct oral anticoagulants (DOACs) increases the risk of thromboembolic and haemorrhagic events. Purpose To determine the net cost benefit of clinical pharmacy interventions on the prescription of DOACs. Method We constructed a decision tree model using a public payer perspective. The appropriateness of the prescription was assessed using the Medication Appropriateness Index. The theoretical risks were collected from the literature and the individual potential risks were calculated using the Nesbit risk assignment conducted by two independent clinical pharmacists. Different costs were included based on diagnosis-related group coding and data in the literature. A univariate sensitivity analysis was performed. Results Thirty-six of 75 patients had an inappropriate prescription of DOACs. The saved difference between avoided costs (7954€) and annualised medication costs and pharmacist cost (4323€) was 3631€ for 75 patients. Conclusions In addition to the enhancement of the quality of the prescription, our results indicate that pharmacist interventions provide a positive net cost benefit.

Glucose-regulated protein of 94 kDa contributes to the development of an aggressive phenotype in breast cancer cells.

Grp94 plays an essential role in protein assembly. We previously suggested that Grp94 overexpression is involved in tumor aggressiveness. However, the underlying mechanisms remain unknown. Since many tumors display high Grp94 levels, we investigated the effects of tumor microenvironment on the regulation of this chaperone expression. First, we found out that hypoxia did not change Grp94 expression in the human tumor cell lines MCF-7 (breast cancer) and HepG2 (liver cancer). Second, glucose deprivation significantly increased Grp94 protein levels. Subsequently, we focused in the putative role of Grp94 in the acquisition of an aggressive phenotype by cancer cells. Using a more aggressive cancer cell model (MDA-MB-231 breast tumor cells), we found out that Grp94 knockdown using siRNA decreased the invasive capacity of cancer cells. Moreover, cells with decreased Grp94 levels displayed an enhanced sensitivity of tumor cells to doxorubicin, a standard drug in the treatment of breast cancer. Taken together, our results suggest that the expression of Grp94 is linked to tumor aggressiveness. Therefore, targeting Grp94 could be an effective way to inhibit tumor growth improving chemotherapy outcome.

Matrix effect of commercially available direct oral anticoagulant standards: a look through the limits and the need for standardization of current calibrators

Abstracts Supported bys Supported by ABSTRACTS OF THE 62ND ANNUAL MEETING OF THE SCIENTIFIC AND STANDARDIZATION COMMITTEE OF THE INTERNATIONAL SOCIETY ON THROMBOSIS AND HAEMOSTASIS MAY 25–28, 2016S OF THE 62ND ANNUAL MEETING OF THE SCIENTIFIC AND STANDARDIZATION COMMITTEE OF THE INTERNATIONAL SOCIETY ON THROMBOSIS AND HAEMOSTASIS MAY 25–28, 2016 Animal, Cellular and Molecular Models AMC01 Endothelial injury and hypoxia enhances neutrophil recruitment, extravasation, and apoptosis during thrombus formation Nishimura S, Seo K and Sakata A Jichi Med Univ, and the Univ of Tokyo, Tochigi, Japan; Jichi Med Univ, Tochigi, Japan Background: Primary trigger of cardiovascular events remains unclear due to the absence of direct analysis tools of in vivo thrombus formation. Aims: To elucidate blood cell behavior and vascular responses, we improved in vivo imaging technique based on multi-photon microscopy, and analyzed new three animal thrombus formation models. Methods:We combined multi-photon microscope technique, and lightmanipulations system, which enabled us to evaluate platelet aggregations by photochemical reactions. Results: First, we induced rapidly developing thrombi composed of discoid platelets, which was triggered by ROS production without endothelial damage. Discoid platelet activations and aggregations were induced without leukocyte recruitment in this system. Second, thrombus formation was also induced by direct endothelial cell disruption by femto-second laser irradiations. With the rapid recruitment of inflammatory neutrophils into damaged area, following fibrin net formation and tissue regenerative changes were observed, indicating tight association between endothelial damage and inflammatory reactions, Spontaneous apoptotic neutrophil death, and endothelial-neutrophilinteractions were induced after platelet aggregations. Last, platelet aggregations, and inflammatory neutrophil recruitment were also observed after transient ischemia and reperfusion. Combination of hypoxia and endothelial injury enhanced thrombus formation, and extravasation steps were remarkably enhanced. Leukocyte escaped from specific and limited “holes” in endothelial junctions. Conclusions: Intravital visualization of thrombus formation elucidated association of inflammation of endothelium, leukocyte recruitment, and platelet aggregations in vivo. Neutrophils were selectively recruited in early phase, which was enhanced by endothelial damages and hypoxic conditions. Our real-time imaging system can evaluate multicellular thrombotic processes and therapeutic strategies against them. AMC02 TMEM16F-mediated platelet pro-coagulant activity contributes to infarct progression after ischemic stroke Baig AA, Haining EJ, Geuss E, Beck S, Stegner D, Kleinschnitz C, Braun A and Nieswandt B University of W€ urzburg, Rudolf Virchow Center for Experimental Biomedicine, Wuerzburg, Germany; University Hospital of W€ urzburg, Department of Experimental Biomedicine, Wuerzburg, Germany; University Hospital of W€ urzburg, Department of Neurology, Wuerzburg, Germany Background: Transmembrane protein TMEM16F, mutated in patients with the bleeding disorder Scott syndrome, is important for the scrambling of phosphatidylserine (PS) to the platelet surface upon platelet activation. Thus, it plays an essential role in the platelet pro-coagulant response. However, the contribution of TMEM16F and the pro-coagulant activity of platelets to thrombo-inflammation after ischemic stroke is unknown. Aims: To investigate the pathophysiological role of TMEM16Fmediated platelet pro-coagulant activity in the setting of ischemic stroke. Methods: A platelet and megakaryocyte specific TMEM16F knockout (KO) mouse was generated by targeted deletion of exon 3 in the Anoctamin6 gene. The mice were assessed in the transient middle cerebral artery occlusion (tMCAO)model of ischemic stroke in addition tomodels of thrombosis and hemostasis, as well as in vitro platelet analyses. Results: TMEM16F KO platelets exposed significantly less PS and also failed to acquire a ballooned morphology after stimulation with ionomycin, indicating a reduced pro-coagulant potential. Likewise, thrombinoscope measurements showed that time to peak thrombin concentration was significantly delayed in KO platelet rich plasma (PRP), as compared to WT PRP. KO mice displayed significantly prolonged tail bleeding times, and were protected in a model of ferric chloride induced thrombosis in the carotid artery, confirming previous reports. These results highlighted the TMEM16F KO as a suitable model with which to investigate the pathophysiological significance of pro-coagulant platelets in cerebral infarct progression following tMCAO. Initial experiments indicate that female TMEM16F KO mice are protected from infarct growth after tMCAO. Further experiments are underway to test if this is also the case in male mice and to understand how pro-coagulant platelets contribute to thrombo-inflammation during ischemic-reperfusion injury. Figure 1