Factor XIa inhibition with asundexian after acute non-cardioembolic ischaemic stroke (PACIFIC-Stroke): an international, randomised, double-blind, placebo-controlled, phase 2b trial

An update on novel therapies for treating patients with arterial thrombosis

INTRODUCTION

Antithrombotic therapy field is undergoing rapid and significant changes during the past decade. In addition to new therapeutic strategies with existing targets, investigators are exploring the potential use of new targets to address unmet needs to treat patients with arterial diseases.

AREAS COVERED

We aim to provide an update on and a comprehensive review of the antithrombic agents that are being explored in patients with arterial diseases. We discuss latest developments with respect to upstream antiplatelet agents, and collagen and thrombin pathway inhibitors. We searched PubMed databases for English language articles using keywords: antiplatelet agents, thrombin pathway inhibitors, collagen receptors, arterial disease.

EXPERT OPINION

Despite implementation of potent P2Y12 inhibitors, there are numerous unmet needs in the treatment of arterial diseases including ceiling effect of currently available antiplatelet agents along with and an elevated risk of bleeding. The latter observations encouraged investigators to explore new targets that can attenuate the generation of platelet-fibrin clot formation and subsequent ischemic event occurrences with minimal effect on bleeding. These targets include collagen receptors on platelets and thrombin generation including FXa, FXIa, and FXIIa. In addition, investigators are studying novel antiplatelet agents/strategies to facilitate upstream therapy in high-risk patients.

Metabolism and Disposition of the Novel Oral Factor XIa Inhibitor Asundexian in Rats and in Humans

BACKGROUND AND OBJECTIVES

Current anticoagulants pose an increased risk of bleeding. The development of drugs targeting factor XIa, like asundexian, may provide a safer treatment option. A human mass‑balance study was conducted to gain a deeper understanding of the absorption, distribution, metabolism, excretion, and potential for drug-drug interaction of asundexian. Additionally, an overview of the biotransformation and clearance pathways for asundexian in humans and bile-duct cannulated (BDC) rats in vivo, as well as in vitro in hepatocytes of both species, is reported.

METHODS

The mass balance, biotransformation, and excretion pathways of asundexian were investigated in six healthy volunteers (single oral dose of 25 mg [¹⁴C]asundexian) and in BDC rats (intravenous [¹⁴C]asundexian 1 mg/kg).

RESULTS

Overall recovery of radioactivity was 101% for humans (samples collected up to 14 days after dosing), and 97.9% for BDC rats (samples collected in the 24 h after dosing). Radioactivity was mainly excreted into feces in humans (80.3%) and into bile/feces in BDC rats (> 94%). The predominant clearance pathways in humans were amide hydrolysis to metabolite M1 (47%) and non-labeled M9 with subsequent N-acetylation to M10; oxidative biotransformation was a minor pathway (13%). In rats, hydrolysis of the terminal amide to M2 was the predominant pathway. In human plasma, asundexian accounted for 61.0% of total drug-related area under the plasma concentration-time curve (AUC); M10 was the major metabolite (16.4% of the total drug-related AUC). Excretion of unmetabolized drug was a significant clearance pathway in both species (human, ~ 37%; BDC rat, ~ 24%). The near-complete bioavailability of asundexian suggests negligible limitations on absorption and first-pass metabolism. Comparison with radiochromatograms from incubations with human or rat hepatocytes indicated consistency across species and a good overall in vitro/in vivo correlation.

CONCLUSIONS

Similar to preclinical experiments, total asundexian-derived radioactivity is cleared quantitatively predominantly via feces. Excretion occurs mainly via amide hydrolysis and as the unchanged drug.

Acute reperfusion treatment and secondary prevention of cancer-related stroke: comprehensive overview and proposal of clinical algorithm

Cancer-related stroke (CRS), referring to ischemic stroke occurring in cancer patients without other clear etiology, represents a clinical challenge, as it is associated with unfavorable clinical outcomes including high rates of recurrence and mortality. There are scarce international recommendations and limited consensus statements on CRS management. For this comprehensive overview, the available studies/reviews/meta-analyses on the use of acute reperfusion and secondary prevention treatments for cancer patients with ischemic stroke, focusing on antithrombotic agents, were collected and summarized. A practical management algorithm was designed per the available data. In short, acute reperfusion in the form of intravenous thrombolysis and mechanical thrombectomy appears to be safe in CRS and can be considered for eligible patients, though the functional outcomes are often poor, and mostly defined by the preexisting condition. Many patients carry indications for anticoagulation, in which case vitamin K antagonists are not preferred, while low-molecular weight heparins remain the treatment of choice; direct oral anticoagulants can be alternatively considered but are contraindicated for gastrointestinal malignancies. For patients without clear anticoagulation indications, no net benefit for anticoagulation compared to aspirin has been shown. Other targeted treatment options should be evaluated in an individualized approach, alongside the appropriate management of conventional cerebrovascular risk factors. Oncological treatment should be swiftly initiated/continued. In conclusion, acute CRS remains a clinical challenge, with many patients suffering recurrent stroke, despite preventive measures. More randomized-controlled clinical trials are urgently needed to pinpoint the most effective management options for this subset of stroke patients.

Factor XIa Inhibitors as a Novel Anticoagulation Target: Recent Clinical Research Advances

BACKGROUND

While current clinically administered anticoagulant medications have demonstrated effectiveness, they have also precipitated significant risks: severe bleeding complications including, but not limited to, gastrointestinal hemorrhaging and intracranial and other life-threatening major bleedings. An ongoing effort is being made to identify the best targets for anticoagulant-targeted drugs. Coagulation factor XIa (FXIa) is emerging as an important target of current anticoagulant treatment.

OBJECTIVE

This review will summarize the development of anticoagulants and recent advances in clinical trials of experimental factor XI inhibitors from a clinical application perspective.

RESULTS

As of 1 January 2023, our search screening included 33 clinical trials. We summarized the research progress of FXIa inhibitors from seven clinical trials that evaluated their efficacy and safety. The results showed no statistically meaningful distinction in the primary efficacy between patients receiving FXIa inhibitors compared to controls (RR = 0.796; 95% CI: 0.606-1.046; I² = 68%). The outcomes did not indicate a statistical difference in the occurrence of any bleeding between patients receiving FXIa inhibitors compared to controls (RR = 0.717; 95% CI: 0.502-1.023; I² = 60%). A subgroup analysis found significant differences in severe bleeding and clinically relevant hemorrhaging in subjects receiving FXIa inhibitors compared to Enoxaparin (RR = 0.457; 95% CI: 0.256-0.816; I² = 0%).

CONCLUSIONS

Clinical trials to date have indicated that factor XIa is a potential anticoagulation target, and factor XIa inhibitors may play an important role in the development of anticoagulants.

Thromboinflammatory challenges in stroke pathophysiology

Despite years of encouraging translational research, ischemic stroke still remains as one of the highest unmet medical needs nowadays, causing a tremendous burden to health care systems worldwide. Following an ischemic insult, a complex signaling pathway emerges leading to highly interconnected thrombotic as well as neuroinflammatory signatures, the so-called thromboinflammatory cascade. Here, we thoroughly review the cell-specific and time-dependent role of different immune cell types, i.e., neutrophils, macrophages, T and B cells, as key thromboinflammatory mediators modulating the neuroinflammatory response upon stroke. Similarly, the relevance of platelets and their tight crosstalk with a variety of immune cells highlights the relevance of this cell-cell interaction during microvascular dysfunction, neovascularization, and cellular adhesion. Ultimately, we provide an up-to-date overview of therapeutic approaches mechanistically targeting thromboinflammation currently under clinical translation, especially focusing on phase I to III clinical trials.

Advances in Clinical Cardiology 2022: A Summary of Key Clinical Trials

INTRODUCTION

Over the course of 2022, numerous key clinical trials with valuable contributions to clinical cardiology were published or presented at major international conferences. This review seeks to summarise these trials and to reflect on their clinical context.

METHODS

The authors reviewed clinical trials presented at major cardiology conferences during 2022, including the American College of Cardiology (ACC), European Association for Percutaneous Cardiovascular Interventions (EuroPCR), European Society of Cardiology (ESC), Transcatheter Cardiovascular Therapeutics (TCT), American Heart Association (AHA), European Heart Rhythm Association (EHRA), Society for Cardiovascular Angiography and Interventions (SCAI), TVT-The Heart Summit (TVT) and Cardiovascular Research Technologies (CRT). Trials with a broad relevance to the cardiology community and those with potential to change current practice were included.

RESULTS

A total of 93 key cardiology clinical trials were identified for inclusion. Interventional cardiology data included trials evaluating the use of new generation novel stent technology and new intravascular physiology strategies such as quantitative flow ratio (QFR) to guide revascularisation in stable and unstable coronary artery disease. New trials in acute coronary syndromes and intervention focused on long-term outcomes of optimal medical therapy (OMT), revascularisation in ischaemic dysfunction and left main (LM) intervention. Structural intervention trials included latest data on optimal timing and anticoagulation strategies in transcatheter aortic valve replacement (TAVR), in addition to expanding evidence in mitral and tricuspid valve interventions. Heart failure data included trials with sodium-glucose cotransporter 2 (SGLT2) inhibitors, iron replacement and novel drugs such as omecamtiv. Prevention trials included new data on proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and polypill strategies. In electrophysiology, new data regarding optimal timing of ablative therapy for atrial fibrillation (AF) in addition to novel screening strategies were evaluated.

CONCLUSION

This article presents a summary of key clinical cardiology trials published and presented during the past year and should be of interest to both practising clinicians and researchers.

Potential anticoagulant of traditional chinese medicine and novel targets for anticoagulant drugs

BACKGROUND

Anticoagulants are the main drugs used for the prevention and treatment of thrombosis. Currently, anticoagulant drugs are primarily multitarget heparin drugs, single-target FXa inhibitors and FIIa inhibitors. In addition, some traditional Chinese drugs also have anticoagulant effects, but they are not the main direction of treatment at present. But the anticoagulant drugs mentioned above, all have a common side effect is bleeding. Many other anticoagulation targets are under investigation. With further exploration of coagulation mechanism, how to further determine new anticoagulant targets and how to make traditional Chinese medicine play anticoagulant role have become a new field of exploration.

PURPOSE

The purpose of the study was to summarize the recent research progress on coagulation mechanisms, new anticoagulant targets and traditional Chinese medicine.

METHODS

A comprehensive literature search was conducted using four electronic databases, including PubMed, Embase, CNKI, Wanfang database and ClinicalTrials.gov, from the inception of the study to 28 Feb 2023. Key words used in the literature search were "anticoagulation", "anticoagulant targets", "new targets", "coagulation mechanisms", "potential anticoagulant", "herb medicine", "botanical medicine", "Chinese medicine", "traditional Chinese medicine", "blood coagulation factor", keywords are linked with AND/OR. Recent findings on coagulation mechanisms, potential anticoagulant targets and traditional Chinese medicine were studied.

RESULTS

The active components extracted from the Chinese medicinal herbs, Salvia miltiorrhiza, Chuanxiong rhizoma, safflower and Panax notoginseng have obvious anticoagulant effects and can be used as potential anticoagulant drugs, but the risk of bleeding is unclear. TF/FVIIa, FVIII, FIX, FXI, FXII, and FXIII have all been evaluated as targets in animal studies or clinical trials. FIX and FXI are the most studied anticoagulant targets, but FXI inhibitors have shown stronger advantages.

CONCLUSION

This review of potential anticoagulants provides a comprehensive resource. Literature analysis suggests that FXI inhibitors can be used as potential anticoagulant candidates. In addition, we should not ignore the anticoagulant effect of traditional Chinese medicine, and look forward to more research and the emergence of new drugs.

New pharmacotherapeutic options for oral anticoagulant treatment in atrial fibrillation patients aged 65 and older: factor XIa inhibitors and beyond

INTRODUCTION

Although much progress has been made using anticoagulation for stroke prevention in patients with non-valvular atrial fibrillation, bleeding is still a major concern.

AREAS COVERED

This article reviews current pharmacotherapeutic options in this setting. Particular emphasis is placed on the ability of the new molecules to minimize the bleeding risk in elderly patients. A systematic search of PubMed, Web of Science, and the Cochrane Library up to March 2023 was carried out.

EXPERT OPINION

Contact phase of coagulation is a possible new target for anticoagulant therapy. Indeed, congenital or acquired deficiency of contact phase factors is associated with reduced thrombotic burden and limited risk of spontaneous bleeding. These new drugs seem particularly suitable for stroke prevention in elderly patients with non-valvular atrial fibrillation in whom the hemorrhagic risk is high. Most of anti Factor XI (FXI) drugs are for parenteral use only. A group of small molecules are for oral use and therefore are candidates to substitute direct oral anticoagulants (DOACs) for stroke prevention in elderly patients with atrial fibrillation. Doubts remain on the possibility of impaired hemostasis. Indeed, a fine calibration of inhibition of contact phase factors is crucial for an effective and safe treatment.

Antithrombotic Therapy in Peripheral Artery Disease: Current Evidence and Future Directions

Patients with peripheral artery disease (PAD) are at an increased risk of major adverse cardiovascular events, and those with disease in the lower extremities are at risk of major adverse limb events primarily driven by atherothrombosis. Traditionally, PAD refers to diseases of the arteries outside of the coronary circulation, including carotid, visceral and lower extremity peripheral artery disease, and the heterogeneity of PAD patients is represented by different atherothrombotic pathophysiology, clinical features and related antithrombotic strategies. The risk in this diverse population includes systemic risk of cardiovascular events as well as risk related to the diseased territory (e.g., artery to artery embolic stroke for patients with carotid disease, lower extremity artery to artery embolism and atherothrombosis in patients with lower extremity disease). Moreover, until the last decade, clinical data on antithrombotic management of PAD patients have been drawn from subanalyses of randomized clinical trials addressing patients affected by coronary artery disease. The high prevalence and related poor prognosis in PAD patients highlight the pivotal role of tailored antithrombotic therapy in patients affected by cerebrovascular, aortic and lower extremity peripheral artery disease. Thus, the proper assessment of thrombotic and hemorrhagic risk in patients with PAD represents a key clinical challenge that must be met to permit the optimal antithrombotic prescription for the various clinical settings in daily practice. The aim of this updated review is to analyze different features of atherothrombotic disease as well as current evidence of antithrombotic management in asymptomatic and secondary prevention in PAD patients according to each arterial bed.

Post-stroke cardiovascular management: Current concepts, integrated care and future developments

After an ischaemic stroke patients often have cardiovascular complications known as stroke-heart syndrome. The cardiovascular management after stroke has a significant impact on life expectancy as well as the quality of life. The development and implementation of management pathways to improve outcomes for patients with stroke-heart syndrome requires a multidisciplinary involvement from health care professionals from primary, secondary and tertiary prevention levels. A holistic, integrated care approach could follow the ABC pathway: A) Appropriate antithrombotic therapy in all stroke/TIA patients in the acute phase as well as recommendations for the longer term treatment regimen are required to avoid recurrent stroke. B) For better functional and psychological status the assessment of post-stroke cognitive and physical impairment, depression, and anxiety as part of routine post-stroke work-up in every patient is necessary. C) Cardiovascular risk factors and comorbidities management further includes cardiovascular work-up, adapted drug therapy, but often also lifestyle changes that are central to the success of integrated care for stroke-heart syndrome. Greater patient and family/caregiver involvement in planning actions and the input and feedback on optimizing stroke care pathways is needed. Achieving integrated care is challenging and highly context dependent on different healthcare levels. A tailored approach will utilize a variety of enabling factors. In this narrative review, we summarize the current evidence and outline potential factors that will contribute to the successful implementation of integrated cardiovascular care for stroke-heart syndrome management.

Effect of atherosclerosis on 5-year risk of major vascular events in patients with transient ischaemic attack or minor ischaemic stroke: an international prospective cohort study

BACKGROUND

The prevalence of atherosclerosis and the long-term risk of major vascular events in people who have had a transient ischaemic attack or minor ischaemic stroke, regardless of the causal relationship between the index event and atherosclerosis, are not well known. In this analysis, we applied the ASCOD (atherosclerosis, small vessel disease, cardiac pathology, other causes, and dissection) grading system to estimate the 5-year risk of major vascular events according to whether there was a causal relationship between atherosclerosis and the index event (ASCOD grade A1 and A2), no causal relationship (A3), and with or without a causal relationship (A1, A2, and A3). We also aimed to estimate the prevalence of different grades of atherosclerosis and identify associated risk factors.

METHODS

We analysed patient data from TIAregistry.org, which is an international, prospective, observational registry of patients with a recent (within the previous 7 days) transient ischaemic attack or minor ischaemic stroke (modified Rankin Scale score of 0-1) from 61 specialised centres in 21 countries in Europe, Asia, the Middle East, and Latin America. Using data from case report forms, we applied the ASCOD grading system to categorise the degree of atherosclerosis in our population (A0: no atherosclerosis; A1 or A2: atherosclerosis with stenosis ipsilateral to the cerebral ischaemic area; A3: atherosclerosis in vascular beds not related to the ischaemic area or ipsilateral plaques without stenosis; and A9: atherosclerosis not assessed). The primary outcome was a composite of non-fatal stroke, non-fatal acute coronary syndrome, or cardiovascular death within 5 years.

FINDINGS

Between June 1, 2009, and Dec 29, 2011, 4789 patients were enrolled to TIAregistry.org, of whom 3847 people from 42 centres participated in the 5-year follow-up; 3383 (87·9%) patients had a 5-year follow-up visit (median 92·3% [IQR 83·4-97·8] per centre). 1406 (36·5%) of 3847 patients had no atherosclerosis (ASCOD grade A0), 998 (25·9%) had causal atherosclerosis (grade A1 or A2), and 1108 (28·8%) had atherosclerosis that was unlikely to be causal (grade A3); in 335 (8·7%) patients, atherosclerosis was not assessed (grade A9). The 5-year event rate of the primary composite outcome was 7·7% (95% CI 6·3-9·2; 101 events) in patients categorised with grade A0 atherosclerosis, 19·8% (17·4-22·4; 189 events) in those with grade A1 or A2, and 13·8% (11·8-16·0; 144 events) in patients with grade A3. Compared with patients with grade A0 atherosclerosis, patients categorised as grade A1 or A2 had an increased risk of the primary composite outcome (hazard ratio 2·77, 95% CI 2·18-3·53; p<0·0001), as did patients with grade A3 (1·87, 1·45-2·42; p<0·0001). Except for age, male sex, and multiple infarctions on neuroimaging, most of the risk factors that were identified as being associated with grade A1 or A2 atherosclerosis were modifiable risk factors (ie, hypertension, dyslipidaemia, overweight, smoking cigarettes, and low physical activity; all p values <0·025).

INTERPRETATION

In patients with transient ischaemic attack or minor ischaemic stroke, those with atherosclerosis have a much higher risk of major vascular events within 5 years than do those without atherosclerosis. Preventive strategies addressing complications of atherosclerosis should focus on individuals with atherosclerosis rather than grouping together all people who have had a transient ischaemic attack or minor ischaemic stroke (including those without atherosclerosis).

FUNDING

AstraZeneca, Sanofi, Bristol Myers Squibb, SOS Attaque Cérébrale Association.

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-FXI_Rx, fesomersen, osocimab, abelacimab, milvexian, asundexian or xisomab 3G3) and highlights the opportunities and challenges for this next generation of anticoagulants.

Factor XI Inhibitors in Early Clinical Trials: A Meta-analysis

BACKGROUND

 Phase II randomized controlled trials (RCTs) on factor(F)XI inhibitors have shown promising results but they were burdened by low statistical power for clinical outcomes.

METHODS

 We performed a systematic review and meta-analysis of RCT comparing FXI inhibitors versus other anticoagulants (enoxaparin or direct oral anticoagulants, DOACs) or versus placebo on top of antiplatelet therapy.

RESULTS

 Eight RCTs testing FXI inhibitors (ISIS 416858, osocimab, abelacimab, milvexian, asundexian) and enrolling 9,216 patients were included. Compared with enoxaparin, FXI inhibitors were associated with reduced any-bleeding (risk ratio [RR]: 0.49, 95% confidence interval [CI]: 0.31-0.77), no difference in major bleeding (RR: 0.96, 95% CI: 0.41-2.28), and reduced trial-defined efficacy endpoint (RR: 0.62, 95% CI: 0.49-0.79), the latter driven by the high-dose regimens. Compared with DOACs, FXI inhibitors were associated with a trend toward reduced any-bleeding (RR: 0.66, 95% CI: 0.31-1.38) and no difference in major bleeding (RR: 1.03, 95% CI: 0.22-4.78) or in trial-defined efficacy endpoint (RR: 1.23, 95% CI: 0.88-1.70). Compared with placebo, FXI inhibitors were associated with increased any-bleeding (RR: 1.25, 95% CI: 1.08-1.43) and a trend toward increased major bleeding (RR: 1.21, 95% CI: 0.75-1.93), both driven by high-dose regimens, with no difference in trial-defined efficacy endpoint (RR: 1.02, 95% CI: 0.92-1.13).

CONCLUSION

 Results of this meta-analysis on FXI inhibitors suggest increased safety and efficacy compared with enoxaparin and modest increased safety compared with DOACs. The use of FXI inhibitors in adjunct to antiplatelet therapy versus placebo appears to be associated with a dose-dependent increase in bleeding without any difference in efficacy.

STUDY REGISTRATION

 This study is registered in PROSPERO (CRD42022367706).

A review of emerging factor XI inhibitors

INTRODUCTION

Whilst the introduction of direct oral anticoagulants (DOACs) has improved the prevention of thromboembolic events, there is still a need for safer anticoagulants. This is particularly so, for specific populations of patients, such as those with an increased bleeding risk or those with severely reduced kidney function. People with Factor XI (FXI) deficiency are at reduced risk of thromboembolic events, without an increased risk of spontaneous bleeding. FXI inhibition, therefore, presents the ideal target for novel anticoagulants.

AREAS COVERED

In this review, we provide an overview of the currently available anticoagulants and the emerging FXIa inhibitors in clinical trials. The need for availability of novel anticoagulants and the potential issues that will hinder the development and marketing of factor XIa inhibitors is also discussed.

EXPERT OPINION

Evidence suggests that FXI inhibition presents a promising drug target for novel anticoagulation therapies. The FXIa inhibitors in development have advantages over DOACs with lower renal clearance and long half-lives. Overall, FXI inhibition presents a promising target, it is likely that the clinical use of FXIa inhibitors is on the horizon.

Pharmacology and Clinical Development of Factor XI Inhibitors

Therapeutic anticoagulation is indicated for a variety of circumstances and conditions in several fields of medicine to prevent or treat venous and arterial thromboembolism. According to the different mechanisms of action, the available parenteral and oral anticoagulant drugs share the common principle of hampering or blocking key steps of the coagulation cascade, which unavoidably comes at the price of an increased propensity to bleed. Hemorrhagic complications affect patient prognosis both directly and indirectly (ie, by preventing the adoption of an effective antithrombotic strategy). Inhibition of factor XI (FXI) has emerged as a strategy with the potential to uncouple the pharmacological effect and the adverse events of anticoagulant therapy. This observation is based on the differential contribution of FXI to thrombus amplification, in which it plays a major role, and hemostasis, in which it plays an ancillary role in final clot consolidation. Several agents were developed to inhibit FXI at different stages (ie, suppressing biosynthesis, preventing zymogen activation, or impeding the biological action of the active form), including antisense oligonucleotides, monoclonal antibodies, small synthetic molecules, natural peptides, and aptamers. Phase 2 studies of different classes of FXI inhibitors in orthopedic surgery suggested that dose-dependent reductions in thrombotic complications are not paralleled by dose-dependent increases in bleeding compared with low-molecular-weight heparin. Likewise, the FXI inhibitor asundexian was associated with lower rates of bleeding compared with the activated factor X inhibitor apixaban in patients with atrial fibrillation, although no evidence of a therapeutic effect on stroke prevention is available so far. FXI inhibition could also be appealing for patients with other conditions, including end-stage renal disease, noncardioembolic stroke, or acute myocardial infarction, for which other phase 2 studies have been conducted. The balance between thromboprophylaxis and bleeding achieved by FXI inhibitors needs confirmation in large-scale phase 3 clinical trials powered for clinical end points. Several of such trials are ongoing or planned to define the role of FXI inhibitors in clinical practice and to clarify which FXI inhibitor may be most suited for each clinical indication. This article reviews the rationale, pharmacology, results of medium or small phase 2 studies, and future perspectives of drugs inhibiting FXI.

Factor XI inhibitors: what should clinicians know

PURPOSE OF REVIEW

Factor XI (FXI) inhibitors were developed to address unmet needs and limitations of current anticoagulants and are currently being studied in several indications. In this paper, we review the rationale for the development of these agents and summarize what clinicians should know about drugs that target FXI.

RECENT FINDINGS

Patients with FXI deficiency may have a lower risk of venous thromboembolism and cardiovascular events and have a variable but generally mild bleeding diathesis. FXI has been proposed as a target for anticoagulants due to the potential for reduction in thrombosis with a lower risk of bleeding than current anticoagulant agents. Several classes of drugs that target FXI are under development, of which three classes (small molecule inhibitors, antisense oligonucleotides and monoclonal antibodies) have been studied in Phase II trials. At least three large Phase III trial programs are planned or are underway, and will study the efficacy and safety of FXI inhibitors in tens of thousands of patients across a variety of indications including atrial fibrillation, stroke and cancer-associated venous thromboembolism.

SUMMARY

FXI inhibitors were developed with the hope of attenuating thrombosis with reduced bleeding/impairment of haemostasis. These agents have shown promise in preliminary trials with a low rate of bleeding. Ongoing Phase III investigations will inform the utility of these agents in clinical practice.

Clinical Evaluation of Factor XIa Inhibitor Drugs: JACC Review Topic of the Week

Factor XI/XIa (FXI/FXIa) represents a potential target for improved precision in anticoagulation because it is involved primarily in thrombus formation and plays a much smaller role in clotting and hemostasis. This suggests that the inhibition of FXI/XIa could prevent pathologic thrombi from forming, but largely preserve a patient's ability to clot in response to bleeding or trauma. This theory is supported by observational data showing that patients with congenital FXI deficiency have lower rates of embolic events without an increase in spontaneous bleeding. Small phase 2 trials of FXI/XIa inhibitors have offered encouraging data with regard to bleeding and safety and evidence of efficacy for the prevention of venous thromboembolism. However, larger clinical trials across multiple patient groups are needed for this emerging class of anticoagulants to understand their possible role in clinical use. Here we review the potential clinical indications for FXI/XIa inhibitors, data available to date, and consider future trials.

A Review of FXIa Inhibition as a Novel Target for Anticoagulation

Limitations of vitamin K antagonists as chronic oral anticoagulant therapy have largely been supplanted by direct factor IIa and factor Xa inhibitor oral anticoagulants with similar efficacy but an overall better safety profile, lack of routine monitoring, and very limited drug-drug interactions compared with agents such as warfarin. However, an increased risk of bleeding remains even with these new-generation oral anticoagulants in fragile patient populations, in patients requiring dual or triple antithrombotic therapy, or high bleed risk surgeries. Epidemiologic data in patients with hereditary factor XI deficiency and preclinical studies support the notion that factor XIa inhibitors have the ability to be an effective but potentially safer alternative to existing anticoagulants, based on their ability to prevent thrombosis directly within the intrinsic pathway without affecting hemostatic mechanisms. As such, various types of factor XIa inhibitors have been studied in early phase clinical studies, including inhibitors of the biosynthesis of factor XIa with antisense oligonucleotides or direct inhibitors of factor XIa using small peptidomimetic molecules, monoclonal antibodies, aptamers, or natural inhibitors. In this review, we discuss how different types of factor XIa inhibitors work and present findings from recently published Phase II clinical trials across multiple indications, including stroke prevention in atrial fibrillation, dual pathway inhibition with concurrent antiplatelets post-myocardial infarction, and thromboprophylaxis of orthopaedic surgery patients. Finally, we refer to ongoing Phase III clinical trials of factor XIa inhibitors and their potential to provide definitive answers regarding their safety and efficacy in preventing thromboembolic events in specific patient groups.

Effects of Tablet Formulation, Food, or Gastric pH on the Bioavailability of Asundexian

Absolute bioavailability (F) and the impact of gastric pH, tablet formulation, and food on the pharmacokinetics and safety of asundexian, an oral factor XIa inhibitor, was assessed in healthy White men aged 18-45 years in 4 studies. For F, fasted participants received 50 μg of [¹³ C₇ ,¹⁵ N]-labeled asundexian intravenously 2 hours after 25 mg of asundexian orally. Tablet formulation (50-mg immediate release [IR], and different amorphous solid dispersion [ASD] IR 25-mg and 50-mg ASD IR tablets) and food effects were explored in 2 studies. Formulation was compared using 50-mg IR versus 25-mg ASD IR and 25-mg ASD IR versus 50-mg ASD IR (fasted); food effect using 25-mg ASD IR and 50-mg ASD IR. Gastric pH modulation was assessed using omeprazole or antacid coadministration with asundexian in the fasted state. Pharmacokinetic parameters included area under the concentration-time curve (AUC; and AUC/dose [D]) and maximum observed concentration (C_max and C_max /D) data were evaluable for 59 participants. F was 103.9%. Relative bioavailability with 25-mg ASD IR and 50-mg ASD IR tablets, respectively, was marginally affected by formulation (AUC/D ratios, 94.3% and 95.1%; C_max /D ratios, 95.5% and 88.7%), food (AUC[/D] ratios, 91.1% and 96.9%; C_max [/D] ratios: 78.3% and 95.1%), and gastric pH (omeprazole, no effect; antacid, AUC ratio, 89.9% and C_max ratio, 83.7%). No serious adverse events or deaths occurred; most adverse events were mild or moderate. In summary, oral asundexian was well tolerated and demonstrated complete bioavailability irrespective of tablet formulation, food, or gastric pH.

Factor XI inhibitors: cardiovascular perspectives

Anticoagulants are the cornerstone for prevention and treatment of thrombosis but are not completely effective, and concerns about the risk of bleeding continue to limit their uptake. Animal studies and experience from patients with genetic coagulation factor XI deficiency suggesting that this factor is more important for thrombosis than for haemostasis raises the potential for drugs that target factor XI to provide safer anticoagulation. Multiple factor XI inhibitors are currently under evaluation in clinical trials, including parenterally administered antisense oligonucleotides, monoclonal antibodies, and orally active small-molecule inhibitors. Promising results of phase 2 trials in patients undergoing major orthopaedic surgery, and in those with end-stage kidney disease, atrial fibrillation and acute coronary syndromes have led to large phase 3 trials that are currently ongoing. We here review premises for the use of these agents, results so far accrued, ongoing studies, and perspectives for future patient care.

Dual pathway inhibition in patients with atherosclerotic disease: pharmacodynamic considerations and clinical implications

INTRODUCTION

The persistence of elevated rates of ischemic recurrences despite the use of antiplatelet therapy among patients with atherosclerotic disease together with the understanding of the pivotal role of coagulation in the thrombo-inflammatory processes involved in the pathogenesis of atherosclerosis and its complications has fostered the development of treatments targeting both platelets and coagulation, a strategy known as dual-pathway inhibition (DPI).

AREAS COVERED

In this review we discuss the recent advancements in the understanding of the interplay between coagulation, platelets and inflammation involved in the pathophysiology of atherosclerosis and atherothrombosis, as the rationale for the implementation of a DPI strategy. We also discuss the available pharmacodynamic (PD) evidence and clinical implications with the use of DPI in patients with atherosclerotic disease.

EXPERT OPINION

The implementation of a DPI by adding the so-called 'vascular dose of rivaroxaban' (i.e. 2.5 mg bis in die), on top of antiplatelet therapy has consistently been associated with reduced levels of thrombin generation in PD studies and with reduced ischemic event rates at the cost of increased bleeding compared to antiplatelet therapy alone. Further research is warranted to best define patients in whom a DPI regimen has the best safety and efficacy profile.

Factor XI/XIa Inhibition: The Arsenal in Development for a New Therapeutic Target in Cardio- and Cerebrovascular Disease

Despite major advancements in the development of safer and more effective anticoagulant agents, bleeding complications remain a significant concern in the treatment of thromboembolic diseases. Improvements in our understanding of the coagulation pathways highlights the notion that the contact pathway-specifically factor XI (FXI)-has a greater role in the etiopathogenesis of thrombosis than in physiological hemostasis. As a result, a number of drugs targeting FXI are currently in different stages of testing and development. This article aims to review the different strategies directed towards FXI-inhibition with a brief summation of the agents in clinical development, and to comment on the therapeutic areas that could be explored for potential indications. Therapeutics targeting FXI/FXIa inhibition have the potential to usher in a new era of anticoagulation therapy.