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Background Direct oral anticoagulants (DOACs) have shown a positive benefit-risk balance in both clinical trials and real-world data, but approximately 2% to 3.5% of patients experience major bleeding annually. Many of these patients require hospitalization, and the administration of reversal agents may be required to control bleeding. Objectives The aim of this study was to investigate clinical outcomes associated with the use of 4-factor prothrombin complex concentrates, idarucizumab, or andexanet for reversal of severe DOAC-associated bleeding. Methods The investigators systematically searched for studies of reversal agents for the treatment of severe bleeding associated with DOAC. Mortality rates, thromboembolic events, and hemostatic efficacy were meta-analyzed using a random effects model. Results The investigators evaluated 60 studies in 4,735 patients with severe DOAC-related bleeding who were treated with 4-factor prothrombin complex concentrates (n = 2,688), idarucizumab (n = 1,111), or andexanet (n = 936). The mortality rate was 17.7% (95% confidence interval [CI]: 15.1% to 20.4%), and it was higher in patients with intracranial bleedings (20.2%) than in patients with extracranial hemorrhages (15.4%). The thromboembolism rate was 4.6% (95% CI: 3.3% to 6.0%), being particularly high with andexanet (10.7%; 95% CI: 6.5% to 15.7%). The effective hemostasis rate was 78.5% (95% CI: 75.1% to 81.8%) and was similar regardless of the reversal agent considered. The rebleeding rate was 13.2% (95% CI: 5.5% to 23.1%) and 78% of rebleeds occurred after resumption of anticoagulation. The risk of death was markedly and significantly associated with failure to achieve effective hemostasis (relative risk: 3.63; 95% CI: 2.56 to 5.16). The results were robust regardless of the type of study or the hemostatic scale used. Conclusions The risk of death after severe DOAC-related bleeding remains significant despite a high rate of effective hemostasis with reversal agents. Failure to achieve effective hemostasis strongly correlated with a fatal outcome. Thromboembolism rates are particularly high with andexanet. Comparative clinical trials are needed.

Stroke is a significant source of morbidity and mortality in developed countries. Cardioembolic strokes represent approximately 15-30% of all ischemic strokes. They are frequently related to atrial fibrillation (AF) and have a worse prognosis and high recurrence rates when compared to other causes (e.g. atherosclerosis).This review includes a summary of general and specific scores to assess cardiovascular and stroke risks, with a focus on specific scores available in AF. Recommendations for antithrombotic therapy are also reviewed.Several scores are available for the evaluation of stroke risk. They are useful to identify the risk factors that trigger the need for medical interventions. Integrated risk scores with visual interfaces showing the risk of events, with and without the proposed interventions, can aid decision-making. The risk of stroke can definitely be considered too high in those patients with a history of stroke/transient ischemic attack, who need antiplatelet therapy (after a non-cardioembolic stroke) or anticoagulant therapy (after a cardioembolic stroke). For primary prevention of stroke, antiplatelet therapy is not usually recommended, while anticoagulation should be considered if the patient has concomitant AF and at least one additional risk factor unrelated to sex.

Death is more frequent than nonfatal recurrent venous thromboembolism (VTE) and major bleeding after acute VTE. The analysis of the causes of death is fundamental to explore new strategies to reduce mortality rates in these patients. The authors performed a meta-analysis to analyze mortality and independently adjudicated causes of death in anticoagulated patients due to VTE, and to evaluate potential differences between different anticoagulant schemes. They searched MEDLINE and CENTRAL, from January 1, 2000, to January 31, 2017, and performed additional searches in Web sites of regulatory agencies, clinical trial registers, and conference proceedings. Two investigators independently selected studies and extracted the data. Study quality was assessed with the Cochrane Collaboration's tool for assessing the risk of bias in randomized studies. Seven prospective randomized trials in 29,844 patients (22,025 patient-year follow-up) were included, comparing dabigatran, rivaroxaban, apixaban, and edoxaban with the standard anticoagulant treatment of VTE. A total of 718 patients died during the follow-up (3.4% per year; 95% confidence interval [CI]: 2.3–4.8). The most frequent causes of death were cancer (42%), followed by VTE (20%), infections (13%), hemorrhage (6%), heart disease (4%), and stroke (2%). There were no differences in the overall survival and causes of death according to the anticoagulant type. Concomitant active cancer during the study was significantly associated with death (odds ratio: 15.2; 95% CI: 9.2–25.1). Cancer is the leading cause of death in contemporary VTE trials. Interventions beyond anticoagulation, particularly in patients with active cancer, are needed.

In recent years, several direct-acting oral anticoagulants (DOAC) have become available for use in Europe and other regions in indications related to prophylaxis and treatment of venous and arterial thromboembolism. They include the oral direct thrombin inhibitor dabigatran etexilate (Pradaxa, Boehringer Ingelheim) and the oral direct FXa inhibitors rivaroxaban (Xarelto, Bayer HealthCare), apixaban (Eliquis, Bristol-Myers Squibb), and edoxaban (Lixiana/Savaysa, Daiichi-Sankyo). The new compounds have a predictable dose response and few drug-drug interactions (unlike vitamin k antagonists), and they do not require parenteral administration (unlike heparins). However, they accumulate in patients with renal impairment, lack widely available monitoring tests for measuring its anticoagulant activity, and no specific antidotes for neutralization in case of overdose and/or severe bleeding are currently available. In this review, we describe the pharmacology of the DOAC, the efficacy, and safety data from pivotal studies that support their currently approved indications and discuss the postmarketing experience available. We also summarize practical recommendations to ensure an appropriate use of the DOAC according to existing data. Finally, we discuss relevant ongoing studies and future perspectives.

In the last decade, several direct oral anticoagulants (DOAC) targeting thrombin (dabigatran) or activated factor X (FXa) (rivaroxaban, apixaban and edoxaban) have been marketed for a number of indications related to prophylaxis and treatment of thrombotic diseases. All these drugs are effective in preventing thrombosis, but are associated with an increased bleeding risk. Areas covered: This review includes a summary of new targets for anticoagulation (e.g.: FXIa, FXIIa, protein disulfide isomerase, polyphosphates, etc.), the discovery process and pharmacological features of new anticoagulant compounds and the available results from non-clinical and clinical studies. A significant number of new anticoagulant compounds are currently in development. These compounds were developed using different technologies like SELEX (aptamers), antisense technology (ASOs), hybridoma (MAB) and structure based drug design. Compounds like ichorcumab (a parenteral thrombin inhibitor), BMS-986177 (oral FXIa inhibitor), BAY-1213790 and xisomab (parenteral FXIa inhibitors) are currently in the clinical development stage. Expert opinion: It's important to be cautious when interpreting preliminary findings of new compounds showing a good antithrombotic effect without altering haemostasis. That being said, the anticoagulants in development have the potential to provide a safer alternative to the currently available anticoagulants in patients at high risk of bleeding, but further investigation is warranted.

In the European Union multiple dose bioequivalence studies are required for the approval of generic prolonged-release products, but they are not required by the US-FDA. In order to investigate if the multiple dose bioequivalence studies are necessary, the bioequivalence studies assessed in the Spanish Agency for Medicines and Health Care Products in the last 10 years were searched to find all reasons for rejection and identify those cases where the multiple dose study had failed to show bioequivalence and the single dose study had shown bioequivalence. In these latter cases, the plasma concentration at the end of the dosing interval (C(τ)) in the single dose study was assessed to investigate its sensitivity to predict non-bioequivalence in the steady state. The search identified six cases where the non-equivalence in the multiple dose study was not detected by the corresponding single dose study. C(τ) was not able to detect the difference in five cases and in general it was more variable than conventional metrics. In conclusion, the multiple dose bioequivalence study is necessary to ensure therapeutic equivalence and the use of C(τ) would be counterproductive, increasing the sample size of the studies without enough sensitivity to detect differences in the steady state.

In the last decade, several direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, apixaban, edoxaban) have been marketed for prophylaxis and/or treatment of thromboembolism without having specific antidotes available for their reversal. Current management of bleeding associated to DOAC includes the removal of all antithrombotic medications and supportive care. Non-specific procoagulant agents (prothrombin complex concentrates and activated factor VIIa) have been used in case of serious bleeding. Currently, some specific antidotes for the DOAC are under development. Idarucizumab (BI 655075; Boehringer Ingelheim) is a fragment of an antibody (Fab), which is a specific antidote to the oral direct thrombin inhibitor dabigatran. Andexanet alfa (r-Antidote, PRT064445; Portola Pharmaceuticals) is a truncated form of enzymatically inactive factor Xa, which binds and reverses the anticoagulant action of the factor Xa inhibitors (e.g.: rivaroxaban, apixaban and edoxaban). Aripazine (PER-977, ciraparantag; Perosphere Inc.) is a synthetic small molecule (~500 Da) that reverses oral dabigatran, apixaban, rivaroxaban, as well as subcutaneous fondaparinux and LMWH in vivo. These antidotes could provide an alternative for management of life-threatening bleeding events occurring with the above-mentioned anticoagulants. In addition, the specific antidote anivamersen (RB007; Regado Biosciences Inc.) is an RNA aptamer in clinical development to reverse the anticoagulant effect of the parenteral factor IXa inhibitor pegnivacogin, which is also in development. This anticoagulant-antidote pair may provide an alternative in situations in which a fast onset and offset of anticoagulation is needed, like in patients undergoing cardiac surgery with extracorporeal circulation, as an alternative to the heparin/protamine pair. This patent review includes a description of the pharmacological characteristics of the novel specific antidotes, the available results from completed non-clinical and clinical studies and the description of ongoing clinical trials with the new compounds.

The history of the traditional anticoagulants is marked by both perseverance and serendipity. The anticoagulant effect of heparin was discovered by McLean in 1915, while he was searching for a procoagulant in dog liver. Link identified dicumarol from spoiled sweet clover hay in 1939 as the causal agent of the sweet clover disease, a hemorrhagic disorder in cattle. Hirudin extracts from the medicinal leech were first used for parenteral anticoagulation in the clinic in 1909, but their use was limited due to adverse effects and difficulties in achieving highly purified extracts. Heparins and coumarins (i.e.: warfarin, phenprocoumon, acenocoumarol) have been the mainstay of anticoagulant therapy for more than 60 years. Over the past decades, the drug discovery paradigm has shifted toward rational design following a target-based approach, in which specific proteins, or "targets", are chosen on current understandings of pathophysiology, small molecules that inhibit the target's activity may be identified by high-throughput screening and, in selected cases, these new molecules can be developed further as drugs. Despite the application of rational design, serendipity has still played a significant role in some of the new discoveries. This review will focus on the discovery of the main anticoagulant drugs in current clinical use, like unfractionated heparin, low-molecular-weight heparins, fondaparinux, coumarins (i.e.: warfarin, acenocoumarol, phenprocoumon), parenteral direct thrombin inhibitors (DTIs) (i.e.: argatroban, recombinant hirudins, bivalirudin), oral DTIs (i.e.: dabigatran) and oral direct factor Xa inhibitors (i.e.: rivaroxaban, apixaban).

Pulmonary embolism (PE) is a relatively common cardiovascular emergency. PE and deep vein thrombosis (DVT) are considered expressions of the same disease, termed as venous thromboembolism (VTE). In the present review, we describe and meta-analyze the efficacy and safety data available with the direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, apixaban, edoxaban) in clinical trials testing these new compounds in the acute/long-term and extended therapy of VTE, providing subgroup analyses in patients with index PE. We analyzed ten studies in 35,019 randomized patients. A total of 14,364 patients (41%) had index PE. In the acute/long-term treatment of VTE, the DOAC showed comparable efficacy in preventing recurrent VTE to standard treatment in patients with index PE (risk ratio [RR]: 0.88; 95% confidence interval [CI]: 0.70–1.11) and index DVT (RR: 0.93; 95% CI: 0.75–1.16) (P for subgroup differences =0.76). VTE recurrence depending on PE anatomical extension and presence/absence of right ventricular dysfunction was only reported in two trials, with results being consistent with those obtained in the overall study populations. In the single trial comparing extended therapy of VTE with DOAC versus warfarin, the point estimate for recurrent VTE tended to disfavor the DOAC in patients with index PE (RR: 2.05; 95% CI: 0.83–5.03) and in patients with index DVT (RR: 1.11; 95% CI: 0.49–2.50) (P for subgroup differences =0.32). In trials that compared DOAC versus placebo for extended therapy, the reduction in recurrent VTE was consistent in patients with PE (RR: 0.15; 95% CI: 0.01–1.82) and in patients with DVT (RR: 0.25; 95% CI: 0.10–0.61) (P for subgroup differences =0.71). The DOAC were associated with a consistently lower risk of clinically relevant bleeding (CRB) than standard treatment of acute VTE and higher risk of CRB than placebo for extended therapy of VTE regardless of index event. In summary, the DOAC were as effective as, and safer than, standard treatment of (hemodynamically stable) PE. Their efficacy in preventing recurrent VTE seemed consistent regardless of anatomical extension of PE (extensive, intermediate, or limit) or presence/absence of right ventricular dysfunction although the data are limited. For extended therapy, the DOAC were more effective than placebo in preventing recurrent VTE but were associated with an increase in CRB regardless of index event.