Current and potentially novel antithrombotic treatment in acute ischemic stroke

Acute ischemic stroke (AIS) is the most common type of stroke and requires immediate reperfusion. Current acute reperfusion therapies comprise the administration of intravenous thrombolysis and/or endovascular thrombectomy. Although these acute reperfusion therapies are increasingly successful, optimized secondary antithrombotic treatment remains warranted, specifically to reduce the risk of major bleeding complications. In the development of AIS, coagulation and platelet activation play crucial roles by driving occlusive clot formation. Recent studies implicated that the intrinsic route of coagulation plays a more prominent role in this development, however, this is not fully understood yet. Next to the acute treatments, antithrombotic therapy, consisting of anticoagulants and/or antiplatelet therapy, is successfully used for primary and secondary prevention of AIS but at the cost of increased bleeding complications. Therefore, better understanding the interplay between the different pathways involved in the pathophysiology of AIS might provide new insights that could lead to novel treatment strategies. This narrative review focuses on the processes of platelet activation and coagulation in AIS, and the most common antithrombotic agents in primary and secondary prevention of AIS. Furthermore, we provide an overview of promising novel antithrombotic agents that could be used to improve in both acute treatment and stroke prevention.

Pharmacokinetics, pharmacodynamics, and safety of frunexian in healthy Chinese volunteer adults: A randomized dose-escalation phase I study

The purpose of this study was to evaluate the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of frunexian (formerly known as EP-7041 and HSK36273) injection, a small molecule inhibitor of activated coagulation factor XI (FXIa), in healthy Chinese adult volunteers. This study was a randomized, placebo- and positive-controlled, sequential, ascending-dose (0.3/0.6/1.0/1.5/2.25 mg/kg/h) study of 5-day continuous intravenous infusions of frunexian. Frunexian administration exhibited an acceptable safety profile with no bleeding events. Steady state was rapidly reached with a median time ranging from 1.02 to 1.50 h. The mean half-life ranged from 1.15 to 1.43 h. Frunexian plasma concentration at a steady state and area under the concentration-time curve exhibited dose-proportional increases. The dose-escalation study of frunexian demonstrated its progressively enhanced capacities to prolong activated partial thromboplastin time (aPTT) and inhibit FXIa activity. The correlations between PK and PD biomarkers (aPTT/baseline and FXI clotting activity/baseline) were described by the two Emax models, with the EC50 values of 8940 and 1300 ng/mL, respectively. Frunexian exhibits good safety and PK/PD properties, suggesting it is a promising candidate for anticoagulant drug.

Orally bioavailable amine-linked macrocyclic inhibitors of factor XIa

The discovery of orally bioavailable FXIa inhibitors has been a challenge. Herein, we describe our efforts to address this challenge by optimization of our imidazole-based macrocyclic series. Our optimization strategy focused on modifications to the P2 prime, macrocyclic amide linker, and the imidazole scaffold. Replacing the amide of the macrocyclic linker with amide isosteres led to the discovery of substituted amine linkers which not only maintained FXIa binding affinity but also improved oral exposure in rats. Combining the optimized macrocyclic amine linker with a pyridine scaffold afforded compounds 23 and 24 that were orally bioavailable, single-digit nanomolar FXIa inhibitors with excellent selectivity against relevant blood coagulation enzymes.

Recent advances in the discovery and development of factor XI/XIa inhibitors

Factor XIa (FXIa) is a serine protease homodimer that belongs to the intrinsic coagulation pathway. FXIa primarily catalyzes factor IX activation to factor IXa, which subsequently activates factor X to factor Xa in the common coagulation pathway. Growing evidence suggests that FXIa plays an important role in thrombosis with a relatively limited contribution to hemostasis. Therefore, inhibitors targeting factor XI (FXI)/FXIa system have emerged as a paradigm-shifting strategy so as to develop a new generation of anticoagulants to effectively prevent and/or treat thromboembolic diseases without the life-threatening risk of internal bleeding. Several inhibitors of FXI/FXIa proteins have been discovered or designed over the last decade including polypeptides, active site peptidomimetic inhibitors, allosteric inhibitors, antibodies, and aptamers. Antisense oligonucleotides (ASOs), which ultimately reduce the hepatic biosynthesis of FXI, have also been introduced. A phase II study, which included patients undergoing elective primary unilateral total knee arthroplasty, revealed that a specific FXI ASO effectively protects patients against venous thrombosis with a relatively limited risk of bleeding. Initial findings have also demonstrated the potential of FXI/FXIa inhibitors in sepsis, listeriosis, and arterial hypertension. This review highlights various chemical, biochemical, and pharmacological aspects of FXI/FXIa inhibitors with the goal of advancing their development toward clinical use.

Factor XIa Inhibitors as New Anticoagulants

With the introduction of thrombin and factor Xa inhibitors to the oral anticoagulant market, significant improvements in both efficacy and safety have been achieved. Early clinical and preclinical data suggest that inhibitors of factor XIa can provide a still safer alternative, with expanded efficacy for arterial indications. This Perspective provides an overview of target rationale and details of the discovery and development of inhibitors of factor XIa as next generation antithrombotic agents.