Effects of Itraconazole and Diltiazem on the Pharmacokinetics and Pharmacodynamics of Milvexian, A Factor XIa Inhibitor

Milvexian, a novel factor XIa inhibitor for stroke prevention: pharmacokinetic and pharmacodynamic evaluation

INTRODUCTION

Antiplatelets and oral anticoagulants are commonly used to treat patients with various cardiovascular and cerebrovascular diseases. However, the primary concern for clinicians remains the risk of bleeding, thus necessitating the development of new therapies. Milvexian is a new anticoagulant that inhibits factor XIa, preventing the pathological formation of thrombi without increasing bleeding risk.

AREAS COVERED

This drug evaluation examines the pharmacokinetic properties of milvexian and provides information on its pharmacodynamics and clinical efficacy in treating some cerebrovascular conditions.

EXPERT OPINION

Milvexian shows a good pharmacokinetic profile with low renal elimination rates, justifying its use in patients with a high degree of renal impairment, and without relevant drug-drug interactions. In patients affected by acute non-cardioembolic ischemic stroke or high-risk transient ischemic stroke, milvexian, in addition to dual antiplatelet therapy, seems to have a positive efficacy profile without any safety concerns, especially in terms of intracranial hemorrhage. Two phase 3 trials are ongoing to investigate the efficacy and safety of milvexian for preventing cardioembolic and non-cardioembolic ischemic stroke.

Therapeutic Potential of FXI Inhibitors: Hype or Hope?

Significant advancements have shaped the landscape of anticoagulant therapy in the past two decades, including the introduction of direct oral anticoagulants (DOACs), characterized by favorable safety and efficacy profiles and reduced drug-to-drug or food interaction resulting in excellent patient compliance. However, residual concerns still exist with standard-of-care anticoagulant therapy, including the inability to use DOACs in several clinical settings and the need to further reduce the risk of bleeding. Recent improvements in the understanding of the mechanisms behind thrombus formation have led to the awareness that the intrinsic pathway of the coagulation cascade may play an important role in pathological thrombosis, but not in hemostasis. This has represented the rationale for targeting this pathway with factor XI (FXI) inhibitors, with the aim of uncoupling hemostasis and thrombosis. Clinical evidence from patients with FXI deficiency further supports this concept. A number of compounds with different mechanisms of action have been developed to target FXI (i.e., asundexian, abelacimab, Ionis-FXIRx, milvexian, osocimab, and Xisomab 3G). To date, the majority of available trials have not gone beyond completion of phase 2 and results are conflictive making it difficult to appraise the clinical benefit of these compounds in the different clinical settings where they have been tested (i.e., atrial fibrillation, acute ischemic stroke, acute myocardial infarction, end-stage renal disease, total knee arthroplasty). Moreover, the largest phase 3 randomized trial designed to test the efficacy of asundexian over apixaban in patients with atrial fibrillation, the OCEANIC-AF, has been prematurely stopped as a result of the inferior efficacy of asundexian. In this review we discuss the pharmacological properties and available evidence generated thus far for factor XI inhibitors, providing a perspective on the current state of these drugs.

Safety, tolerability, pharmacokinetics and pharmacodynamics of milvexian with aspirin and/or clopidogrel in healthy participants

Milvexian, an oral activated Factor XI (FXIa) inhibitor, is in clinical studies where it may be combined with antiplatelet agents, including aspirin and/or clopidogrel, to prevent thromboembolic diseases. This phase I trial assessed safety, pharmacokinetics, and pharmacodynamics of milvexian coadministration with aspirin and/or clopidogrel in healthy participants through 3 drug-drug interaction studies using a 3-period, 3-treatment, crossover design. A total of 113 participants were randomized to receive milvexian (200 mg; twice daily for 5 days) or matched placebo coadministered with once-daily aspirin (325 mg for 5 days) and/or clopidogrel (Day 1: 300 mg; Days 2-5: 75 mg). Milvexian was safe and well tolerated, with and without aspirin and/or clopidogrel. Eight mild bleeding adverse events (AEs) were reported in 5 of 113 participants across various treatment arms. Peak and total exposures of milvexian were similar with or without clopidogrel and/or aspirin. Exposure-dependent prolongation of activated partial thromboplastin time and reduction of FXI clotting activity by milvexian were similar with coadministration of aspirin and/or clopidogrel. Milvexian, with or without coadministration of aspirin and/or clopidogrel, did not affect bleeding time or platelet aggregation. Administration of milvexian alone or with aspirin and/or clopidogrel was safe and well tolerated without increased incidence of AEs, including bleeding. Pharmacokinetic and pharmacodynamic effects of milvexian, including bleeding time, were similar with or without aspirin and/or clopidogrel.ClinicalTrials.gov Identifier: NCT03698513.

Milvexian: evaluating the factor XIa inhibitor for the treatment of acute coronary syndrome

INTRODUCTION

Balancing the prevention of thrombosis with bleeding risk when combining anticoagulants and platelet antagonists remains a concern among clinicians, particularly in patients with acute coronary syndrome (ACS) who are treated with potent antiplatelet therapy. This may be because the available antiplatelet and anticoagulants are unable to uncouple physiological hemostasis and pathological thrombosis. Therefore, their use is associated with an unavoidable elevated risk of bleeding.

AREAS COVERED

Evidence available from studies evaluating FXIa inhibitors and milvexian was collected from a selective literature search. In this review, the authors describe the potential role of FXI/XIa in experimental thrombosis, evidence for FXIa inhibition in the treatment of clinical thrombotic events, and highlight the current evidence supporting the role of milvexian, a novel FXIa inhibitor, in patients with ACS.

EXPERT OPINION

The ongoing LIBREXIA-ACS trial is a large-scale study currently investigating milvexian in patients with ACS. This study may support the proof of concept of differentiating physiological hemostasis and pathological thrombosis and achieving maximum antithrombotic efficacy with minimum bleeding risk when used on top of dual antiplatelet therapy with potent P2Y12 receptor blockers.

Pharmacological and clinical appraisal of factor XI inhibitor drugs

The evolution of anticoagulation therapy, from vitamin K antagonists to the advent of direct oral anticoagulants (DOACs) almost two decades ago, marks significant progress. Despite improved safety demonstrated in pivotal trials and post-marketing observations, persistent concerns exist, particularly regarding bleeding risk and the absence of therapeutic indications in specific subgroups or clinical contexts. Factor XI (FXI) has recently emerged as a pivotal contributor to intraluminal thrombus formation and growth, playing a limited role in sealing vessel wall injuries. Inhibiting FXI presents an opportunity to decouple thrombosis from haemostasis, addressing concerns related to bleeding events while safeguarding against thromboembolic events. Notably, FXI inhibition holds promise for patients with end-stage renal disease or cancer, where clear indications for DOACs are currently lacking. Various compounds have undergone design, testing, and progression to phase 2 clinical trials, demonstrating a generally favourable safety and tolerability profile. However, validation through large-scale phase 3 trials with sufficient power to assess both safety and efficacy outcomes is needed. This review comprehensively examines FXI inhibitors, delving into individual classes, exploring their pharmacological properties, evaluating the latest evidence from randomized trials, and offering insights into future perspectives.

Milvexian: A Focus on a New Oral Anticoagulant that Targets Factor XIa for Thromboembolism Prophylaxis

Drugs that target factor XI and/or XIa have been evaluated as alternatives to existing anticoagulants, in light of studies that indicate that a decrease in Factor XI/XIa levels or activity may result in a lower risk of thrombosis without a significant increase in bleeding risk. Milvexian is an investigational small-molecule factor XIa inhibitor that has recently completed phase 2 clinical trials. Preclinical studies were suggestive of its potential to prevent arterial and venous thrombosis. It was well-tolerated in healthy participants, as well as in participants with mild or moderate hepatic impairment and moderate or severe renal impairment. Notably, patients who received milvexian after knee arthroplasty had a dose-proportional lower incidence of venous thromboembolism compared to patients who received postoperative enoxaparin, and they had a lower incidence of clinically relevant bleeding. A separate phase 2 trial was conducted that assessed the use of milvexian for secondary stroke prevention in patients who had ischemic stroke or transient ischemic attack. It failed its primary objective of establishing a dose-response relationship between milvexian and a composite endpoint of symptomatic ischemic stroke or covert brain infarction. The trial did, however, show a reduction in the relative risk of symptomatic ischemic stroke across most of the treatment groups receiving various dosages of milvexian compared to placebo. The efficacy of milvexian in secondary stroke prevention will be further assessed in an upcoming phase 3 trial. Additional upcoming phase 3 trials will also assess its efficacy in stroke prevention in patients with atrial fibrillation as well as in event reduction in patients with acute coronary syndrome.

Determination of the Potential Clinical Benefits of Small Molecule Factor XIa Inhibitors in Arterial Thrombosis

Anticoagulants are the mainstay for the prevention and treatment of thrombosis. However, bleeding complications remain a primary concern. Recent advances in understanding the contribution of activated factor XI (FXIa) in arterial thrombosis with a limited impact on hemostasis have led to the development of several FXIa-targeting modalities. Injectable agents including monoclonal antibodies and antisense oligonucleotides against FXIa have been primarily studied in venous thrombosis. The orally active small molecules that specifically inhibit the active site of FXIa are currently being investigated for their antithrombotic activity in both arteries and veins. This review focuses on a discussion of the potential clinical benefits of small molecule FXIa inhibitors, mainly asundexian and milvexian, in arterial thrombosis based on their pharmacological profiles and the compelling results of phase 2 clinical studies. The preclinical and epidemiological basis for the impact of FXIa in hemostasis and arterial thrombosis is also addressed. In recent clinical study results, asundexian appears to reduce ischemic events in patients with myocardial infarction and minor-to-moderate stroke, whereas milvexian possibly provides benefits in patients with minor stroke or high-risk transient ischemic attack (TIA). In addition, asundexian and milvexian had a minor impact on hemostasis even in combination with dual-antiplatelet therapy. Other orally active FXIa inhibitors also produce antithrombotic activity in vivo with low bleeding risk. Therefore, FXIa inhibitors might represent a new class of direct-acting oral anticoagulants (DOACs) for the treatment of thrombosis, although the explicit clinical positions of asundexian and milvexian in patients with ischemic stroke, high-risk TIA, and coronary artery disease require confirmation from the outcomes of ongoing phase 3 trials.

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.

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.

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, a potential target for anticoagulation therapy for venous thromboembolism

Venous thromboembolism (VTE) is a common cause of mortality and disability in hospitalized patients, and anticoagulation is an essential therapeutic option. Despite the increasing use of direct oral anticoagulants, complications and adverse drug reactions still occur in patients with VTE. Within 5 years, 20% of patients with VTE experience recurrence, and 50% of patients with deep vein thrombosis develop post-thrombotic syndrome. Furthermore, bleeding due to anticoagulants is a side effect that must be addressed. Therefore, safer and more effective anticoagulant strategies with higher patient compliance are urgently needed. Available epidemiological evidence and animal studies have shown that factor XI (FXI) inhibitors can reduce thrombus size and loosen the thrombus structure with a relatively low risk of bleeding, suggesting that FXI has an important role in thrombus stabilization and is a safer target for anticoagulation. Recent clinical trial data have also shown that FXI inhibitors are as effective as enoxaparin and apixaban in preventing VTE, but with a significantly lower incidence of bleeding. Furthermore, FXI inhibitors can be administered daily or monthly; therefore, the monitoring interval can be longer. Additionally, FXI inhibitors can prolong the activated partial thromboplastin time without affecting prothrombin time, which is an easy and common test used in clinical testing, providing a cost-effective monitoring routine for patients. Consequently, the inhibition of FXI may be an effective strategy for the prevention and treatment of VTE. Enormous progress has been made in the research strategies for FXI inhibitors, with abelacimab already in phase III clinical trials and most other inhibitors in phase I or II trials. In this review, we discuss the challenges of VTE therapy, briefly describe the structure and function of FXI, summarize the latest FXI/activated FXI (FXIa) inhibitor strategies, and summarize the latest developments in clinical trials of FXI/FXIa inhibitors.

Rationale and design of the AXIOMATIC-SSP phase II trial: Antithrombotic treatment with factor XIa inhibition to Optimize Management of Acute Thromboembolic events for Secondary Stroke Prevention

BACKGROUND

Individuals with ischemic stroke or transient ischemic attack (TIA) have a high early risk of ischemic stroke despite dual antiplatelet therapy. The risk of ischemic stroke, and associated disability, represents a significant unmet clinical need. Genetic variants resulting in reduced factor XI levels are associated with reduced risk for ischemic stroke but are not associated with increased intracranial bleeding. Milvexian is an oral small-molecule inhibitor of FXIa that binds activated factor XI with high affinity and selectivity and may reduce the risk of stroke when added to antiplatelet drugs without significant bleeding. We aimed to evaluate the dose-response relationship of milvexian in participants treated with dual antiplatelets.

METHODS

We began a phase II, double-blinded, randomized, placebo-controlled trial at 367 sites in 2019. Participants (N = 2366) with ischemic stroke (National Institutes of Health Stroke Scale score ≤7) or high-risk TIA (ABCD² score ≥6) were randomized to 1 of 5 doses of milvexian or placebo for 90 days. Participants also received clopidogrel 75 mg daily for the first 21 days and aspirin 100 mg for 90 days. The efficacy endpoint was the composite of ischemic stroke or incident infarct on magnetic resonance imaging. Major bleeding, defined as type 3 or 5 bleeding according to the Bleeding Academic Research Consortium, was the safety endpoint. Participant follow-up will end in 2022.

CONCLUSION

The AXIOMATIC-SSP trial will evaluate the dose-response of milvexian for ischemic stroke occurrence in participants with ischemic stroke or TIA.