Tolerability and pharmacokinetics of TB-402 in healthy male volunteers

Factor XI Inhibitors: Potential Role in End-Stage Kidney Disease

Patients with end-stage kidney disease (ESKD) experience a high thrombotic risk but are also at increased risk of bleeding. There is an unmet need for safer antithrombotic therapy in patients with ESKD on hemodialysis. Factor XI (FXI) represents an attractive therapeutic target for anticoagulation because of the potential to mitigate the bleeding risks associated with currently approved anticoagulants, especially in patients at high risk of bleeding. FXI inhibition is also an attractive option in settings where coagulation is activated by exposure of the blood to artificial surfaces, including the extracorporeal circuit during hemodialysis. Therapies targeting FXI that are in the most advanced stages of clinical development include antisense oligonucleotides, monoclonal antibodies, and synthetic small molecules, which serve either to lower FXI levels or block its physiological effects. This review article presents the most recent pharmacological data with FXI inhibitors, briefly describes phase 2 and 3 clinical trials with these agents, and critically examines the potential future use of FXI inhibitors for extracorporeal circuit anticoagulation in patients with ESKD. In addition, laboratory monitoring and reversal of FXI inhibitors are briefly discussed.

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.

Pharmacokinetic-Pharmacodynamic Analysis' Role in Design of Phase ⅠClinical Trials of Anticoagulant Agents: A Systematic Review

INTRODUCTION

There remains an unmet need for better anticoagulants. The phase I clinical trial is of great significance in the development of anticoagulants, and the design is special. This system review aims to provide insights for the design of future phase I clinical trials of anticoagulants.

AREAS COVERED

We searched the database PubMed and ClinicalTrail.gov website, to collate the phase I clinical trial of anticoagulants in healthy people. The study protocol, inclusion-exclusion criteria, safety, and pharmacodynamic indexes were reviewed.

EXPERT OPINION

New anticoagulants under development focused on inhibiting one or more than one serine proteases within the coagulation cascade. Agents targeting intrinsic factors are in the pipeline of the drug development. The enrollment eligibility criteria have more restrictions on laboratory tests, medical history, or medication history related to bleeding and coagulation; more precautions were taken to assess and minimize the risk of hemorrhagic events. Pharmacodynamics markers were evaluated as a surrogate marker of anticoagulation potency to guide further dose selection in drug's development. In future, the positive control study can be applied in phase I studies of new anticoagulants with appropriate pharmacodynamics markers, which can provide more favorable information on making 'go/no' decision in drug development.

Therapeutic strategies for thrombosis: new targets and approaches

Antiplatelet agents and anticoagulants are a mainstay for the prevention and treatment of thrombosis. However, despite advances in antithrombotic therapy, a fundamental challenge is the side effect of bleeding. Improved understanding of the mechanisms of haemostasis and thrombosis has revealed new targets for attenuating thrombosis with the potential for less bleeding, including glycoprotein VI on platelets and factor XIa of the coagulation system. The efficacy and safety of new agents are currently being evaluated in phase III trials. This Review provides an overview of haemostasis and thrombosis, details the current landscape of antithrombotic agents, addresses challenges with preventing thromboembolic events in patients at high risk and describes the emerging therapeutic strategies that may break the inexorable link between antithrombotic therapy and bleeding risk.

Current and emerging pharmacotherapy for ischemic stroke prevention in patients with atrial fibrillation

Introduction: Atrial fibrillation (AF) is associated with high morbidity and mortality rates due to thromboembolic complications, and anticoagulation is central to the management of this common arrhythmia to prevent acute thromboembolic events. The traditional anticoagulants: heparin, fondaparinux, and vitamin K antagonists (VKA, e.g. warfarin, acenocoumarol or phenprocoumin) have long served as pharmacotherapy for ischemic stroke prophylaxis. Areas covered: In this review article, the authors provide an overview on current and emerging pharmacotherapy for ischemic stroke prevention. Furthermore, they review the data from novel therapeutic targets in the coagulation cascade, and investigational anticoagulant drugs currently assessed in preclinical and clinical studies. Expert opinion: The introduction of nonvitamin K antagonist oral anticoagulants (NOACs) was an important milestone, as these drugs show relative efficacy, safety, and convenience compared to the VKAs. Nevertheless, their clinical use still has some limitations with, for example, patients with severe renal impairment and those with mechanical heart valves, high bleeding risks, lack of standard laboratory monitoring and (some) reversal agents. To overcome some of these limitations, various attempts are now underway to discover new strategies and targets via the hemostatic pathway in order to develop new coagulation inhibiting drugs.

Anticoagulation beyond direct thrombin and factor Xa inhibitors: indications for targeting the intrinsic pathway?

Antithrombotic drugs like vitamin K antagonists and heparin have been the gold standard for the treatment and prevention of thromboembolic disease for many years. Unfortunately, there are several disadvantages of these antithrombotic drugs: they are accompanied by serious bleeding problems, it is necessary to monitor the therapeutic window, and there are various interactions with food and other drugs. This has led to the development of new oral anticoagulants, specifically inhibiting either thrombin or factor Xa. In terms of effectiveness, these drugs are comparable to the currently available anticoagulants; however, they are still associated with issues such as bleeding, reversal of the drug and complicated laboratory monitoring. Vitamin K antagonists, heparin, direct thrombin and factor Xa inhibitors have in common that they target key proteins of the haemostatic system. In an attempt to overcome these difficulties we investigated whether the intrinsic coagulation factors (VIII, IX, XI, XII, prekallikrein and high-molecular-weight kininogen) are superior targets for anticoagulation. We analysed epidemiological data concerning thrombosis and bleeding in patients deficient in one of the intrinsic pathway proteins. Furthermore, we discuss several thrombotic models in intrinsic coagulation factor-deficient animals. The combined results suggest that intrinsic coagulation factors could be suitable targets for anticoagulant drugs.

New Anticoagulants for the Prevention and Treatment of Venous Thromboembolism

Anticoagulant drugs, like vitamin K antagonists and heparin, have been the mainstay for the treatment and prevention of venous thromboembolic disease for many years. Although effective if appropriately used, traditional anticoagulants have several limitations such as unpredictable pharmacologic and pharmacokinetic responses and various adverse effects including serious bleeding complications. New oral anticoagulants have recently emerged as an alternative because of their rapid onset/offset of action, predictable linear dose-response relationships and fewer drug interactions. However, they are still associated with problems such as bleeding, lack of reversal agents and standard laboratory monitoring. In an attempt to overcome these drawbacks, key steps of the hemostatic pathway are investigated as targets for anticoagulation. Here we reviewed the traditional and new anticoagulants with respect to their targets in the coagulation cascade, along with their therapeutic advantages and disadvantages. In addition, investigational anticoagulant drugs currently in the development stages were introduced.

Determination of the starting dose in the first-in-human clinical trials with monoclonal antibodies: a systematic review of papers published between 1990 and 2013

A systematic review was performed to evaluate how the maximum recommended starting dose (MRSD) was determined in first-in-human (FIH) studies with monoclonal antibodies (mAbs). Factors associated with the choice of each MRSD determination method were also identified. PubMed was searched for FIH studies with mAbs published in English between January 1, 1990 and December 31, 2013, and the following information was extracted: MRSD determination method, publication year, therapeutic area, antibody type, safety factor, safety assessment results after the first dose, and number of dose escalation steps. Seventy-nine FIH studies with mAbs were identified, 49 of which clearly reported the MRSD determination method. The no observed adverse effects level (NOAEL)-based approach was the most frequently used method, whereas the model-based approach was the least commonly used method (34.7% vs 16.3%). The minimal anticipated biological effect level (MABEL)- or minimum effective dose (MED)-based approach was used more frequently in 2011–2013 than in 1990–2007 (31.6% vs 6.3%, P=0.036), reflecting a slow, but steady acceptance of the European Medicines Agency’s guidance on mitigating risks for FIH clinical trials (2007). The median safety factor was much lower for the MABEL- or MED-based approach than for the other MRSD determination methods (10 vs 32.2–53). The number of dose escalation steps was not significantly different among the different MRSD determination methods. The MABEL-based approach appears to be safer and as efficient as the other MRSD determination methods for achieving the objectives of FIH studies with mAbs faster.

Giving monoclonal antibodies to healthy volunteers in phase 1 trials: is it safe?

Many monoclonal antibodies (MAbs) have been studied in healthy volunteers in phase 1, but few data have been published on the safety of that practice. We aimed to review the available data, and thereby to estimate the risks of participation in phase 1trials of MAbs. We searched PubMed, the ClinicalTrials.gov database and Google, using the search terms 'monoclonal antibody', 'phase 1' and 'healthy volunteers'. We identified 70 completed trials of MAbs in healthy volunteers, but the published data were too sparse to allow confident assessment of the risks of MAbs in healthy volunteers. Our best estimate of risk of a life-threatening adverse event was between 1: 425 and 1: 1700 volunteer-trials, but all such events occurred in a single trial (of TGN1412). In a phase 1trial of a small molecule, the risk of death or a life-threatening adverse event appears to be 1: 100,000-1,000,000 volunteer-trials, which is similar to the risk of many ordinary daily activities. Most people would consider that level of risk to be 'minimal' or 'negligible' and, therefore, acceptable. On that basis, the safety record of MAbs in healthy volunteers has been ruined by the TGN1412 disaster. However, that experience is unlikely to be repeated, because of improvements in governance and practice of phase 1trials. If the experience of TGN1412 is disregarded, it seems reasonable to continue using healthy volunteers in phase 1trials of MAbs, provided that there are scientific and medical reasons to conclude that the risk is truly minimal.

Investigational anticoagulants for hematological conditions: a new generation of therapies

INTRODUCTION

The introduction of novel anticoagulants has had contrasting effects on the agents in the pipeline, fueling the development of some and sinking the others. The complexity of the coagulation cascade offers interesting inhibition choices that might become valid treatment options.

AREAS COVERED

This review will highlight some of the anticoagulants in the pipeline. Following the success of the direct thrombin and FXa inhibitors already in the market, new agents are being tested. These include AZD0837, betrixaban, letaxaban, darexaban, and LY517717. Targeting other components of the hemostatic pathway might lead to better safety profiles without influencing efficacy. Inhibitors to FVIIa-tissue factor (FVIIa/TF) complex, FIX, FXI, and FXII are being assessed. New inspiring inhibitors are antisense oligonucleotides (ASOs) and aptamers. These are highly specific agents with readily reversible effect and might be engineered to inhibit any coagulation factor. Currently tested ASOs and aptamers are inhibitors of FXI, FXII, thrombin, FIXa, and platelet GPIV.

EXPERT OPINION

Some of the agents in the pipeline offer valid treatment option for long-term therapy, overcoming some of the drawbacks of the novel anticoagulants. Research is being driven by an expanding market in the anticoagulation field that has been unexploited for a long time.

Single-dose TB-402 or rivaroxaban for the prevention of venous thromboembolism after total hip replacement. A randomised, controlled trial

TB-402 is a long-acting monoclonal antibody that partially inhibits factor VIII. A single administration of TB-402 was effective and well-tolerated for the prevention of venous thromboembolism (VTE) after total knee replacement. In this study, the efficacy and safety of a single administration of TB-402 for the extended prophylaxis of VTE after total hip replacement (THR) was investigated. This was a phase II, randomised, active-controlled, double-blind study that included patients undergoing elective THR surgery. Patients were randomised to TB-402 25 mg or TB-402 50 mg, administered as a single intravenous administration 2-4 hours postoperatively, or to rivaroxaban 10 mg once daily for 35 days. The primary efficacy outcome was total VTE defined as symptomatic VTE and asymptomatic deep-vein thrombosis (DVT) detected by bilateral venography at day 35. The principal safety outcome was the incidence of major bleeding and clinically relevant non-major bleeding until day 35. Total VTE was similar in all groups: 5.3% (95%CI 2.9-9.6), 5.2% (95%CI 2.8-9.3) and 4.7% (95%CI 2.5-8.7) for TB-402 25 mg, TB-402 50 mg and rivaroxaban, respectively. All were asymptomatic DVTs. Major or clinically relevant non-major bleedings were observed in 5.8% (95%CI 3.3-9.9), 7.2% (95%CI 4.4-11.6) and 1.4% (95%CI 0.5-4.2) for TB-402 25 mg, TB-402 50 mg and rivaroxaban, respectively. In conclusion, TB-402, administered as a single postoperative dose, had a similar efficacy compared to rivaroxaban for the prevention of VTE after THR. The incidence of major and clinically relevant non-major bleeding was higher in the TB-402 groups than in the rivaroxaban group.

Antidote strategies to reverse anticoagulation with TB-402, a long-acting partial inhibitor of factor VIII

BACKGROUND

TB-402 is a partially inhibiting antibody of factor VIII that is under development as a long-acting anticoagulant.

PATIENTS AND METHODS

The reversibility of FVIII inhibition by TB-402 was evaluated in vitro after spiking with recombinant human FVIII (rhFVIII), human plasma-derived FVIII (hpdFVIII), recombinant activated human FVII (rhFVIIa), FVIII inhibitor bypassing activity (FEIBA), and prothrombin complex concentrate (PCC). Twelve subjects were randomized to placebo or 35 or 70 IU kg(-1) rhFVIII 48 h after a single dose of 620 μg kg(-1) TB-402. TB-402 concentrations, FVIII activity (FVIII:C), activated partial thromboplastin time (APTT) and thrombin generation were measured over a period of 8 weeks.

RESULTS

In spiked samples, TB-402 inhibited FVIII:C by 30%, prolonged APTT by 4.5 s, and reduced the peak height in the thrombin generation assay to 56% ± 13% of the control value. In the presence of 10 μg mL(-1) TB-402, rhFVIII restored FVIII:C and APTT to the values obtained in the absence of TB-402. The inhibitory effect of TB-402 on thrombin generation was entirely reversed by rhFVIII, hpdFVIII, rhFVIIa, FEIBA, and PCC. In men, the mean half-life (t(1/2) ) of TB-402 was 14.2 days. TB-402 lowered the endogenous thrombin potential by 23% for ~ 35 days. Infusion of 35 IU kg(-1) rhFVIII had a marginal effect, whereas 70 IU kg(-1) rhFVIII restored FVIII:C, reduced APTT back to baseline for 9 h, and restored thrombin generation for ~ 3 h.

CONCLUSIONS

TB-402 resulted in a stable long-term anticoagulant effect. rhFVIII and other procoagulants counteracted the effect of TB-402 temporarily, and may be effective antidotes for future clinical practice.

New antithrombotic drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article focuses on new antithrombotic drugs that are in or are entering phase 3 clinical testing. Development of these new agents was prompted by the limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this article (1) outlines the rationale for development of new antithrombotic agents; (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs; and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.

Emerging anticoagulants

INTRODUCTION

Thromboembolic disease encompasses a spectrum of conditions extending from deep vein thrombosis to stroke and myocardial infarction. The current anticoagulation therapy is cumbersome and characterized by several important drawbacks.

AREAS COVERED

Existing treatments and latest breakthroughs on emerging anticoagulants are presented. Oral and parenteral novel anticoagulants are being developed and tested for efficacy and safety and results are being published regularly. The introduction of novel anticoagulants marks a new era in the management of anticoagulated patients. It is important for the healthcare provider to understand the benefits and risks of the armamentarium of anticoagulants that will be available in the very near future. The critical conclusions drawn will help the reader look past what is the most highlighted feature of the new anticoagulantion era: the non-necessity for monitoring.

EXPERT OPINION

Currently, novel anticoagulants seem to lack the indefinable 'charm' of weakness. However, important questions remain unanswered and will require in-depth evaluations.

Single intravenous administration of TB-402 for the prophylaxis of venous thromboembolism after total knee replacement: a dose-escalating, randomized, controlled trial

BACKGROUND

TB-402 is a novel anticoagulant monoclonal antibody with a prolonged antithrombotic effect resulting from its partial factor (F)VIII inhibition and long half-life. We evaluated the efficacy and safety of a single administration of TB-402 for the prevention of venous thromboembolism (VTE) after total knee replacement (TKR).

PATIENTS AND METHODS

This was a phase II, dose-escalating, randomized, enoxaparin-controlled, open-label study. Patients were post-operatively assigned to a single dose of TB-402 (0.3, 0.6 or 1.2 mg kg(-1)) or enoxaparin 40 mg for at least 10 days (n = 75 per group; 3:1 TB-402 to enoxaparin). The primary efficacy outcome was total VTE defined as asymptomatic deep vein thrombosis (DVT) detected by bilateral venography and symptomatic VTE by day 7 to 11. The principal safety outcome was the incidence of major bleeding and clinically relevant non-major bleeding.

RESULTS

Total VTE was lower in all TB-402 groups compared with enoxaparin: 16.7%(95% CI 9.8-26.9), 23.9%(95% CI 15.3-35.3), 24.1%(95% CI 16.0-34.5) and 39.0%(95% CI 28.8-50.1) for TB-402 0.3, 0.6, 1.2 mg kg(-1) and enoxaparin, respectively (P = 0.003 for TB-402 0.3 mg kg(-1) vs. enoxaparin). The incidence of total VTE in the pooled TB-402 groups was 21.6% (95%CI 16.6-27.5), an absolute risk reduction vs. enoxaparin of 17.4% (95% CI 5.2-29.6). Major or clinically relevant non-major bleeding was observed in 3/75(4.0%), 4/74(5.4%), 7/87(8.0%) and 3/79(3.8%) patients for TB-402 0.3, 0.6, 1.2 mg kg(-1) and enoxaparin, respectively.

CONCLUSIONS

TB-402, as a single post-operative administration, was associated with a lower rate of VTE in all doses tested, compared with enoxaparin. The incidence of major and clinically relevant non-major bleeding was similar to enoxaparin 40 mg for TB-402 0.3 and 0.6 mg kg(-1).

New parenteral anticoagulants in development

The therapeutic armamentarium of parenteral anticoagulants available to clinicians is mainly composed by unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), fondaparinux, recombinant hirudins (i.e. bivalirudin, desirudin, lepirudin) and argatroban. These drugs are effective and safe for prevention and/or treatment of thromboembolic diseases but they have some drawbacks. Among other inconveniences, UFH requires regular anticoagulant monitoring as a result of variability in the anticoagulant response and there is a risk of serious heparin-induced thrombocytopaenia (HIT). LMWH, fondaparinux and recombinant hirudins are mainly cleared through the kidneys and their use in patients with severe renal insufficiency may be problematic. LMWH is only partially neutralized by protamine while fondaparinux and recombinant hirudins have no specific antidote. Novel anticoagulants in development for parenteral administration include new indirect activated factor Xa (FXa) inhibitors (idrabiotaparinux, ultra-low-molecular-weight heparins [semuloparin, RO-14], new LMWH [M118]), direct FXa inhibitors (otamixaban), direct FIIa inhibitors (flovagatran sodium, pegmusirudin, NU172, HD1-22), direct FXIa inhibitors (BMS-262084, antisense oligonucleotides targeting FXIa, clavatadine), direct FIXa inhibitors (RB-006), FVIIIa inhibitors (TB-402), FVIIa/tissue factor inhibitors (tifacogin, NAPc2, PCI-27483, BMS-593214), FVa inhibitors (drotrecogin alpha activated, ART-123) and dual thrombin/FXa inhibitors (EP217609, tanogitran). These new compounds have the potential to complement established parenteral anticoagulants. In the present review, we discuss the pharmacology of new parenteral anticoagulants, the results of clinical studies, the newly planned or ongoing clinical trials with these compounds, and their potential advantages and drawbacks over existing therapies.