[New anticoagulants in 2024: Development of factor XI and XIa inhibitors]. / Les nouveaux anticoagulants en 2024 : développement des inhibiteurs du facteur XI et du XIa.

Thrombosis remains one of the leading causes of death in the world. The history of anticoagulation has evolved considerably from non-specific drugs (i.e., heparins and vitamin K antagonists, VKA) to agents that directly target specific coagulation factors (i.e., argatroban, fondaparinux and direct oral anticoagulants, DOAC). Since the last decade, DOAC are widely used in clinical practice because of their ease to use, their favorable pharmacological profile and the fact that they do not require monitoring. However, despite having a better safety profile than vitamin K antagonist, their bleeding risk is not negligible. New anticoagulants targeting the contact phase of coagulation are currently being developed and could make it possible to prevent the risk of thrombosis without impairing hemostasis. Epidemiological and preclinical data on FXI deficiency make FXI a promising therapeutic target. The aim of this review is to summarize the results of the various clinical trials available that focus on FXI/FXIa inhibition, and to highlight the challenges that this new therapeutic class of anticoagulants will face.

[Method comparison between two hemostasis analyzers: STA R Max3 and Cobas t 511]. / Comparaison de méthode entre deux analyseurs d'hémostase : STA R Max3 et Cobas t 511.

The STA R Max3 (Stago, France) and Cobas t511 (Roche Diagnostics, Germany) are two automated hemostasis analysers that can be used to perform a wide range of tests. The STA R Max3 uses a mechanical clot detection system to measure coagulation times, while the Cobas t511 uses optical detection. The aim of this study was to compare the analytical performance of these two analysers using fresh plasma samples with or without a risk of interference due to hemolysis or lipemia. For plasma samples without interference, acceptable agreement was observed for prothrombin time (PT) (n = 55), activated partial thromboplastin time (APTT) (n = 56), fibrinogen (n = 56) and factor II (n = 43) with R² of 0.907, 0.963, 0.979 and 0.968 respectively. For factor V (n = 43) and D-dimers (n = 45), agreement was less acceptable, with respective R² of 0.756 and 0.887, but with no clinical impact. For hemolysed samples, acceptable results were observed for PT, fibrinogen and D-dimers, but three results were clinically discordant for APTT, and STA R Max3 offered greater robustness for processing highly lipemic samples.

[Interference of oral anti-Xa anticoagulants during monitoring of unfractionated heparin treatments: practical and future attitudes]. / Interférence des anticoagulants oraux directs anti-Xa lors de la surveillance des traitements par héparine non-fractionnée : attitudes pratiques et à venir.

Contrary to direct oral anticoagulants (DOAC), unfractionated heparin (UFH) requires daily monitoring when administered at therapeutic dose. At present, UFH monitoring is preferably carried out by measuring plasma anti-Xa activity, however, in patients previously treated with an anti-Xa DOAC and switched to UFH, there is a high risk of DOAC interfering with the measurement of UFH anti-Xa activity. Residual anti-Xa DOAC in the sample can lead to an overestimation of the anticoagulant activity attributed to heparin and thus to incorrect anticoagulation. This risk of interference should not be overlooked because interference may occur even at concentration of DOAC below the hemostatic safety threshold and can last several days. To overcome this issue, several alternatives are being studied. This note provides an update on anti-Xa DOAC interference and different strategies available in current practice. It also underlines the importance of communication between biologists and clinicians on anticoagulant treatments received by patients.

DOAC-Remove to counteract the interference of anti-Xa oral anticoagulants on the monitoring of heparin.

INTRODUCTION: The monitoring of unfractionated heparin (UFH) by anti-factor Xa activity (AXA) is commonly used to ensure effective anticoagulation and prevent bleeding risk. However, in patients previously treated with an anti-Xa direct oral anticoagulant (DOAC) switching to UFH therapy, there is a risk of interference that may lead to inappropriate anticoagulation. The first objective of this study was to validate DOAC-Remove to remove DOAC for measuring UFH specific AXA. The second objective was to assess the length of DOAC interference on UFH monitoring and to identify potential predictive factors. MATERIALS AND METHODS: This monocentric retrospective study included all patients admitted from April 2019 to April 2021 previously treated with anti-Xa DOAC, and for whom an interference on UFH monitoring was suspected. Interference was defined as a difference in the AXA measured before and after using DOAC-Remove >2.8-fold standard deviation of the method. RESULTS: Removal with DOAC-Remove was specific of DOAC (apixaban n = 42, rivaroxaban n = 41, UFH n = 20) and sufficient to avoid interference on UFH AXA measurement. The exact interference length was 6.0 days [IQR 3.0-11.0] for apixaban (n = 26) and 4.5 days [IQR 2.0-5.8] for rivaroxaban (n = 20). Among the 89 patients sorted based on an interference length ≤ or >3 days, 74 (83.1%) presented an interference greater than 3 days. Correlations were observed with age for apixaban and creatinine for rivaroxaban. CONCLUSIONS: Our results suggest that DOAC-Remove could be of high interest in patients receiving UFH previously treated with an anti-Xa DOAC even if DOAC was stopped for more than 3 days.

Development of new anticoagulant in 2023: Prime time for anti-factor XI and XIa inhibitors.

Thrombosis remains one of the leading causes of death in the world. The history of anticoagulation has evolved considerably from non-specific drugs (i.e., heparins and vitamin K antagonists, VKA) to agents that directly target specific coagulation factors (i.e., argatroban, fondaparinux and direct oral anticoagulants, DOAC). Since the last decade, DOAC are widely used in clinical practice because of their ease to use with favorable pharmacological profile and not requiring monitoring, particularly for venous thromboembolism treatment and prevention and stroke prevention in atrial fibrillation. However, despite having a better safety profile than VKA, their bleeding risk is not negligible. Therefore, research is underway to develop new anticoagulant therapies with a better safety profile. One of these news approaches to reduce the risk of bleeding is to target the coagulation in the intrinsic pathway, in particular the contact activation, with the ultimate goal of preventing thrombosis without impairing hemostasis. Based on epidemiological data with patients with inherited factor XI (FXI) deficiency and preclinical studies, FXI emerged as the most promising candidate target separating hemostasis from thrombosis. This review summaries the role of FXI and FXIa in hemostasis, provides evidence of initial success with FXI pathway inhibitors in clinical trials (such as IONIS-FXIRx, fesomersen, osocimab, abelacimab, milvexian, asundexian or xisomab 3G3) and highlights the opportunities and challenges for this next generation of anticoagulants.

A Validated LC-MS/MS Method for Performing Belatacept Drug Monitoring in Renal Transplantation.

Belatacept, a CTLA4-Ig, was designed to prevent rejection and graft loss in kidney transplant recipients. This immunotherapy showed a long-term clinical benefit mainly on renal function and better glycemic control but was also associated with a higher number of severe infectious diseases, particularly CMV disease, and lymphoproliferative disease. Therapeutic drug monitoring usually guides the benefit-risk assessment of long-term immunosuppression. In this study, an analytical method by LC-MS/MS was developed in 20 microL of plasma for the belatacept quantification. Intra- and inter-assay precision and accuracy were lower than 20% for the limit of quantification, and 15% for higher concentrations. The method was implemented in our lab and provided data about the inter-variability (N = 108) and intra-variability (N = 33) of belatacept concentrations in kidney transplant recipients with a stable renal function, after conversion from a CNI- to a belatacept-based regimen.

Antiphospholipid antibodies: what is new in 2022 / Détection des anticorps antiphospholipides : actualités en 2022

Antiphospholipid syndrome (APS) is a clinicobiological entity defined by the association of thrombotic events and/or obstetric complications and the presence of persistent antiphospholipid antibodies (aPLs) detected by coagulation tests (lupus anticoagulant, LAC) and/or immunological assays (anticardiolipin and anti-glycoprotein-beta-I antibodies). The increased use of direct oral anticoagulants (DOAC) for the treatment of venous thromboembolism (VTE) is now a challenge for hematology laboratories for the diagnosis of APS. DOAC interfere with LAC screening and confirmation tests resulting in a risk of false positive results. To avoid these interferences, several solutions are suggested. Some of them rely on the use of DOAC-reversal systems (activated charcoal tablet, filter system) others on the use of reagents insensitive to DOAC presence in the sample. Detection of anti-phosphatidylserine/prothrombin antibodies may be helpful because they are strongly associated to the presence of LAC and are increasingly recognized as a useful tool in the diagnosis and prognosis of APS. Finally, positivity of LA in the setting of a viral infection is frequent and not specific to APS. During the Covid-19 pandemic, many patients developed arterial and VTE that could suggest testing for aPLs. The association between LAC and a risk of VTE or in-hospital mortality in hospitalized Covid-19 patients was not demonstrated. Moreover, aPLs do not persist after Covid-19. Currently, testing for aPLs in Covid-19 patients is not recommended.

Le syndrome des antiphospholipides (SAPL) est une entité clinico-biologique définie par l'association de manifestations thrombotiques et/ou de complications obstétricales et la présence persistante d'anticorps antiphospholipides (aPLs) détectés par des tests de coagulation (lupus anticoagulant, LA) et/ou par des tests immunologiques (anticorps anti-cardiolipine et anticorps anti-ß2-glycoprotéine-I). L'essor des anticoagulants oraux directs (AOD) dans la prise en charge des évènements thrombotiques veineux (ETV) constitue aujourd'hui un défi pour les laboratoires d'hémostase dans le cadre du diagnostic du SAPL. Les AOD interfèrent avec les tests de dépistage et de confirmation du LA occasionnant des faux positifs. Afin de se soustraire à ces interférences plusieurs solutions sont proposées. Certaines reposent sur l'utilisation de système neutralisant l'AOD (pastille de charbon activé, système de filtre) d'autres sur l'utilisation de réactifs insensibles à la présence d'AOD. On peut également faire appel aux anticorps anti-phosphatidylsérine/prothrombine très corrélés à la présence de LA et constituant un outil de plus en plus reconnu dans le diagnostic biologique du SAPL et son pronostic. Enfin, la positivité des aPLs dans un contexte infectieux est fréquente et non spécifique du SAPL. Au cours de la pandémie Covid-19, de nombreux patients ont présentés des ETV et artériels qui ont pu motiver la recherche d'aPLs. L'association entre LA et le risque d'ETV ou la mortalité hospitalière chez les patients Covid-19 hospitalisés n'a pas été démontrée. De plus, il ne semble pas qu'il y ait de persistance de ces aPLs après la Covid-19. A ce jour, la recherche d'aPLs chez les patients atteint de Covid-19 n'est pas recommandée.