Discovery of betrixaban (PRT054021), N-(5-chloropyridin-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxybenzamide, a highly potent, selective, and orally efficacious factor Xa inhibitor

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

The U.S. FDA approved cardiovascular drugs from 2011 to 2023: A medicinal chemistry perspective

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. A total of 28 new molecular entities (NMEs) were approved by the U.S. Food and Drug Administration (FDA) for the treatment of cardiovascular diseases from 2011 to 2023. Approximately 25 % of the medications were sanctioned for the management of diverse vascular disorders. The other major therapeutic areas of focus included antilipemic agents (15 %), blood pressure disease (11 %), heart failure, hyperkalemia, and cardiomyopathy (7-8% each). Among all the approved drugs, there are a total of 22 new chemical entities (NCEs), including inhibitors, agonists, polymers, and inorganic compounds. In addition to NCEs, 6 biological agents (BLAs), including monoclonal antibodies, small interfering RNAs (siRNAs), and antisense oligonucleotides, have also obtained approval for the treatment of cardiovascular diseases. From this perspective, approved NCEs are itemized and discussed based on their disease, targets, chemical classes, major drug metabolites, and biochemical and pharmacological properties. Systematic analysis has been conducted to examine the binding modes of these approved drugs with their targets using cocrystal structure information or docking studies to provide valuable insights for designing next-generation agents. Furthermore, the synthetic approaches employed in the creation of these drug molecules have been emphasized, aiming to inspire the development of novel, efficient, and applicable synthetic methodologies. Generally, the primary objective of this review is to provide a comprehensive examination of the clinical applications, pharmacology, binding modes, and synthetic methodologies employed in small-molecule drugs approved for treating CVD. This will facilitate the development of more potent and innovative therapeutics for effectively managing cardiovascular diseases.

Minimally modified human blood coagulation factor X to bypass direct factor Xa inhibitors

BACKGROUND

Direct oral factor (F)Xa inhibitors are widely used as alternatives to conventional vitamin K antagonists in managing venous thromboembolism and nonvalvular atrial fibrillation. Unfortunately, bleeding-related adverse events remain a major concern in clinical practice. In case of bleeding or emergency surgery, rapid-onset reversal agents may be required to counteract the anticoagulant activity.

OBJECTIVES

The ability of FXa variants to bypass the direct oral FXa inhibitors was assessed.

METHODS

Human FXa variants were generated through substitution of phenylalanine 174 (F174) for either alanine, isoleucine, or serine. FXa variants were stably expressed in HEK293 cells and purified to homogeneity using ion-exchange chromatography.

RESULTS

F174-substituted human FX variants demonstrated efficacy in restoring thrombin generation in plasma containing direct FXa inhibitors (apixaban, rivaroxaban, edoxaban). Their ability to bypass the anticoagulant effects stems from a significantly reduced sensitivity for the direct FXa inhibitors due to a decrease in binding affinity determined using molecular dynamics simulations and free energy computation. Furthermore, F174 modification resulted in a partial loss of inhibition by tissue factor pathway inhibitor, enhancing the procoagulant effect of F174-substituted FX. Consequently, the F174A- and F174S-substituted FX variants effectively counteracted the effects of 2 widely used anticoagulants, apixaban and rivaroxaban, in plasma of atrial fibrillation and venous thromboembolism patients.

CONCLUSION

These human FX variants have the potential to serve as a rescue reversal strategy to overcome the effect of direct FXa inhibitors in case of life-threatening bleeding events or emergency surgical interventions.

Rh(III)-Catalyzed Controlled Ortho-Amidation of Arylamides with Dioxazolones Using Weakly Coordinating Native Primary Amide as the Directing Group

Herein, we report a controlled introduction of an amide unit at the ortho-position of an electron-deficient arylamide system without affording any cyclized products using user-friendly dioxazolone as an amidating reagent in the presence of a Rh(III)-catalyst. This is the first report where native primary amide has been utilized as a weakly coordinating group for site-selective C-N bond formation reaction. The developed protocol works under external auxiliary-free conditions with a wide substrate scope.

An Update on Betrixaban, The Challenging Anticoagulant Agent for Extended Venous Thromboembolism Prophylaxis

ABSTRACT

Venous thromboembolism (VTE) is a prevalent yet preventable cause of death, particularly among hospitalized patients. Studies have shown that the risk of VTE remains high for up to 6 months after discharge, highlighting the need for extended thromboprophylaxis as a viable treatment approach. Despite the availability of several anticoagulant drugs such as vitamin K antagonists, heparinoids, rivaroxaban, apixaban, edoxaban, and dabigatran, none of them has received approval from the US Food and Drug Administration for long-term thromboprophylaxis. However, an emerging factor Xa inhibitor called betrixaban has shown promising results in Phase II and phase III trials, positioning itself as the first and only US Food and Drug Administration-approved anticoagulant for extended thromboprophylaxis in hospitalized patients after discharge. Betrixaban offers distinct pharmacological characteristics, including a long half-life, low renal excretion, and unique hepatic metabolism, making it an attractive option for various theoretical uses. Numerous articles have been published discussing the safety and efficacy of betrixaban, all of which have emphasized its usefulness and practicality. However, there has been limited discussion regarding its weaknesses and areas of ambiguity. Therefore, this article aimed to explore the challenges faced during the approval process of betrixaban and provide a comprehensive review of the literature on its advantages and disadvantages as a long-term prophylaxis approach for VTE. Furthermore, we aim to identify the ambiguous points that require further investigation in future studies.

The Structure-property Relationships of Clinically Approved Protease Inhibitors

BACKGROUND

Proteases play important roles in the regulation of many physiological processes, and protease inhibitors have become one of the important drug classes. Especially because the development of protease inhibitors often starts from a substrate- based peptidomimetic strategy, many of the initial lead compounds suffer from pharmacokinetic liabilities.

OBJECTIVE

To reduce drug attrition rates, drug metabolism and pharmacokinetics studies are fully integrated into modern drug discovery research, and the structure-property relationship illustrates how the modification of the chemical structure influences the pharmacokinetic and toxicological properties of drug compounds. Understanding the structure- property relationships of clinically approved protease inhibitor drugs and their analogues could provide useful information on the lead-to-candidate optimization strategies.

METHODS

About 70 inhibitors against human or pathogenic viral proteases have been approved until the end of 2021. In this review, 17 inhibitors are chosen for the structure- property relationship analysis because detailed pharmacological and/or physicochemical data have been disclosed in the medicinal chemistry literature for these inhibitors and their close analogues.

RESULTS

The compiled data are analyzed primarily focusing on the pharmacokinetic or toxicological deficiencies found in lead compounds and the structural modification strategies used to generate candidate compounds.

CONCLUSION

The structure-property relationships hereby summarized how the overall druglike properties could be successfully improved by modifying the structure of protease inhibitors. These specific examples are expected to serve as useful references and guidance for developing new protease inhibitor drugs in the future.

Investigating Betrixaban Maleate drug degradation profiles, isolation and characterization of unknown degradation products by mass-triggered preparative HPLC, HRMS, and NMR

Betrixaban Maleate, a novel oral, once-daily factor Xa inhibitor drug substance, was subjected to stress testing under a wide range of degradation conditions, including acidic hydrolysis, alkaline hydrolysis, oxidative, thermal, and photolytic, to determine its inherent stability. The drug was biodegradable in acidic and alkaline environments, and three new degradation products were identified. Two degraded products are formed in an acidic environment, while the third is in alkaline conditions. The three degradants were identified using UPLC-ESI/MS and isolated using mass-triggered preparative HPLC, and their structures were unambiguously elucidated using HRMS and 2D NMR techniques. Based on spectral and chromatographic data, it was firmly proven that these distinct degradation products were the betrixaban chemical's hydrolysis components. The formation of the degradants has been hypothesized through several possible mechanisms.

Microwave assisted synthesis of fluorescent hetero atom doped carbon dots for determination of betrixaban with greenness evaluation†

A simple, rapid and eco-friendly method for synthesis of nitrogen and sulfur doped carbon dots (N,S-CDs) is described. The method involved one step carbonization assisted by a green microwave irradiation route using available and cheap sources, as sucrose (source for C) and thiourea (source for N and S). The formed aqueous solution of N,S-CDs showed excellent optical and electronic properties with high compatibility and stability. The particles of the prepared dots were spherical with a narrow range of size from 1.7 to 3.7 nm with a quantum yield of 0.20. These dots act as a fluorescent probe, as they showed an intense blue fluorescence at 413 nm after excitation at 330 nm. The N,S-CDs were utilized for determination of the anticoagulant drug, betrixaban maleate (BTM), based on quenching of their fluorescence upon its gradual addition. The quenching process was found to be through an inner filter effect mechanism. The proposed method showed a good linearity over a concentration range of (1.0–100.0 μM) with LOD and LOQ values of 0.33 μM and 0.99 μM, respectively. All validation parameters met the acceptance criteria according to ICH guidelines. The high specificity and sensitivity of the performed method contributed to further assay of BTM in dosage form and spiked human plasma sample with high percent recoveries and low values of RSD. Interference from co-administered drugs was studied. Finally, the greenness of the proposed method was evaluated adopting a ComplexGapi approach, the excellent green profile has supported its applicability in quality control laboratories.

Schematic sketch clarified the stepwise synthesis process of N,S-CDs.

Investigation of the tight binding mechanism of a new anticoagulant DD217 to factor Xa by means of molecular docking and molecular dynamics

A new promising drug candidate DD217 has been proposed recently as a potent anticoagulant acting on factor Xa (fXa) target. It exhibits the lowest concentration of doubling the prothrombin time among the known anticoagulants. In order to explain the efficacy of DD217 in terms of molecular interactions with its target we studied the hypothesis of the tight binding mechanism by means of molecular dynamics simulations and statistical analysis of the trajectory. The conducted analysis confirms the significant contributions to the MM/GBSA estimated binding free energy of the S4 pocket residues as well the crucial role of establishing the hydrogen bonds between the ligand and the backbone amides of Gly216 and Gly218 of the target. The simulation results support the hypothesis of the tight binding mechanism of DD217 to fXa.Communicated by Ramaswamy H. Sarma.

Switching from warfarin to direct-acting oral anticoagulants: it is time to move forward!

Oral vitamin K antagonists (VKAs), warfarin, have been in routine clinical use for almost 70 years for various cardiovascular conditions. Direct-Acting Oral Anticoagulants (DOACs) have emerged as competitive alternatives for VKAs to prevent stroke in patients with non-valvular atrial fibrillation (AF) and have become the preferred choice in several clinical indications for anticoagulation. Recent guidelines have limited the use of DOACs to patients with non-valvular AF to reduce the risk of cardioembolic complications and to treat venous thromboembolism (VTE). Although emerging evidence is suggestive of its high efficacy, there was a lack of data to support DOACs safety profile in patients with mechanical valve prosthesis, intracardiac thrombi, or other conditions such as cardiac device implantation or catheter ablation. Therefore, several clinical trials have been conducted to assess the beneficial effects of using DOACs, instead of VKAs, for various non-guideline-approved indications. This review aimed to discuss the current guideline-approved indications for DOACs, advantages, and limitations of DOACs use in various clinical indications highlighting the potential emerging indications and remaining challenges for DOACs use. Several considerations are in favour of switching from warfarin to DOACs including superior efficacy, better adverse effect profile, fewer drug-drug interactions, and they do not require frequent international normalized ratio (INR) monitoring. Large randomized controlled trials are required to determine the safety and efficacy of their use in various clinical indications.

Development of three ecological spectroscopic methods for analysis of betrixaban either alone or in mixture with lercanidipine: greenness assessment

Three eco-friendly spectrophotometric methods were developed for determination of the novel anticoagulant drug, betrixaban (BTX). The first method (method A) was based on direct analysis of BTX at 229.4 nm on the zero-order spectrum using methanol as the optimum solvent. While the second method (method B) was based on measuring difference absorption value (ΔA) of BTX at 335 nm, which was obtained from pH-induced spectral difference (difference spectra of BTX in 0.1 M NaOH versus 0.1 M HCl). The third method (method C) was based on measurement of the first-derivative amplitudes of BTX and its co-administered Ca channel blocker lercanidipine (LER) at 304 and 229 nm for simultaneous assay of BTX and LER, respectively. All methods were linear over concentration ranges of 1.0-20.0 and 8.0-80.0 µg ml^-1 for BTX in methods A and B, respectively, and of 1.0-20.0 and 1.0-25.0 µg ml^-1 for BTX and LER, respectively, in method C. The three methods were fully validated and assessed for greenness by three metrics: analytical eco-scale, green analytical procedure index and Analytical GREEnness metrics. The results indicated the validity and greenness of the proposed methods. Moreover, the methods were applied to assay the studied analytes in their dosage forms with high percentage of recovery and low percentage of relative s.d. values.

Integrating Incompatible Assay Data Sets with Deep Preference Learning

A large amount of bioactivity assay data is already accumulated in public databases, but the integration of these data sets for quantitative structure-activity relationship (QSAR) studies is not straightforward due to differences in experimental methods and settings. We present an efficient deep-learning-based approach called Deep Preference Data Integration (DPDI). For integrating outcome variables of different assay types, a surrogate variable is introduced, and a neural network is trained such that the total order induced by the surrogate variable is maximally consistent with given data sets. In a task of predicting efficacy of factor Xa inhibitors, DPDI successfully integrated 2959 molecules distributed in 129 assay data sets. In most of our experiments, data integration improved prediction accuracy strongly in interpolation and extrapolation tasks, indicating that DPDI is an effective tool for QSAR studies.

Drugs in phase I and II clinical development for the prevention of stroke in patients with atrial fibrillation

INTRODUCTION

Atrial fibrillation is the most frequently diagnosed cardiac arrhythmia globally and is associated with ischemic stroke and heart failure. Patients with atrial fibrillation are typically prescribed long-term anticoagulants in the form of either vitamin K antagonists or non-vitamin K antagonist oral anticoagulants; however, both carry a potential risk of adverse bleeding.

AREAS COVERED

This paper sheds light on emerging anticoagulant agents which target clotting factors XI and XII, or their activated forms - XIa and XIIa, respectively, within the intrinsic coagulation pathway. The authors examined data available on PubMed, Scopus, and the clinical trials registry of the United States National Library of Medicine (www.clinicaltrials.gov).

EXPERT OPINION

Therapies targeting factors XI or XII can yield anticoagulant efficacy with the potential to reduce adverse bleeding. Advantages for targeting factor XI or XII include a wider therapeutic window and reduced bleeding. Long-term follow-up studies and a greater understanding of the safety and efficacy are required. Atrial fibrillation is a chronic disease and therefore the development of oral formulations is key.

Optimization and Validation of a Facile RP-HPLC Method for Determination of Betrixaban and Lercanidipine in Pharmaceutical and Biological Matrices

A simple, accurate, rapid and sensitive reversed-phase high-performance liquid chromatography (RP-HPLC) method was established for determination of a novel non-vitamin K antagonist oral anticoagulant drug, betrixaban, and its co-administered calcium-channel blocker drug, lercanidipine, in pharmaceutical formulations and biological fluids. The proposed HPLC method was the first chromatographic method applied to estimate this mixture in a short chromatographic run (<6 min), high resolution between betrixaban/lercanidipine (Rs = 7.12) and acceptable values of limit of detection (LOD), limit of quantification (LOQ) and percentage of relative standard deviation (%RSD). The chromatographic separation was performed on a cyano column using a mobile phase composed of acetonitrile:methanol:water (35:35:30, v/v/v) containing 0.2% orthophosphoric acid adjusted to pH 3.2 by triethylamine, programmed with a flow rate of 1 mL/min with UV detection at 240 nm. The proposed method showed linearity over the concentration ranges of (0.20-20.0 μg/mL) and (0.25-25.0 μg/mL) for betrixaban and lercanidipine, respectively. All validation parameters met the acceptance criteria according to ICH guidelines in terms of linearity, LOD, LOQ, accuracy, precision, robustness, specificity and system suitability. The method was applied to assay the studied analytes in their pharmaceutical formulations with high % recovery (98-102%) and low %RSD (<1.5). Furthermore, the proposed method was successfully applied for the determination of betrixaban in spiked human plasma.

Binding of direct oral anticoagulants to the FA1 site of human serum albumin

The anticoagulant therapy is widely used to prevent and treat thromboembolic events. Until the last decade, vitamin K antagonists were the only available oral anticoagulants; recently, direct oral anticoagulants (DOACs) have been developed. Since 55% to 95% of DOACs are bound to plasma proteins, the in silico docking and ligand-binding properties of drugs apixaban, betrixaban, dabigatran, edoxaban, and rivaroxaban and of the prodrug dabigatran etexilate to human serum albumin (HSA), the most abundant plasma protein, have been investigated. DOACs bind to the fatty acid (FA) site 1 (FA1) of ligand-free HSA, whereas they bind to the FA8 and FA9 sites of heme-Fe(III)- and myristic acid-bound HSA. DOACs binding to the FA1 site of ligand-free HSA has been validated by competitive inhibition of heme-Fe(III) recognition. Values of the dissociation equilibrium constant for DOACs binding to the FA1 site (ie, ^calc K_DOAC ) derived from in silico docking simulations (ranging between 1.2 × 10^-8 M and 1.4 × 10^-6 M) agree with those determined experimentally from competitive inhibition of heme-Fe(III) binding (ie, ^exp K_DOAC ; ranging between 2.5 × 10^-7 M and 2.2 × 10^-6 M). In addition, this study highlights the inequivalence of rivaroxaban binding to mammalian serum albumin. Given the HSA concentration in vivo (~7.5 × 10^-4 M), values of K_DOAC here determined indicate that the formation of the HSA:DOACs complexes in the absence and presence of FAs and heme-Fe(III) may occur in vivo. Therefore, HSA appears to be an important determinant for DOACs transport.

Druggability Assessment for Selected Serine Proteases in a Pharmaceutical Industry Setting

Target druggability assessment is an integral part of the early target characterization and selection process in pharmaceutical industry. Here, we investigate a set of five different serine proteases from the blood coagulation cascade. The aim of this study is twofold. Firstly, leveraging the wealth of available in-house high-throughput screening (HTS) data, we analyze HTS hit rates and discuss their predictive value for the development of small molecule (SMOL) candidates. Purely structure-activity relationship (SAR) based druggability ratings are compared with computational protein-structure based druggability assessments. Secondly, we evaluate the impact of using conformational ensembles from molecular dynamics (MD) simulations instead of single static crystal structures as basis for computational druggability assessments. Based on this study, we recommend incorporating molecular dynamics routinely into the early target characterization process, especially if only a single X-ray structure is available.

Reversal Agents for the Direct Factor Xa Inhibitors: Biochemical Mechanisms of Current and Newly Emerging Therapies

The direct oral anticoagulants targeting coagulation factor Xa or thrombin are widely used as alternatives to vitamin K antagonists in the management of venous thromboembolism and nonvalvular atrial fibrillation. In case of bleeding or emergency surgery, reversal agents are helpful to counteract the anticoagulant therapy and restore hemostasis. While idarucizumab has been established as an antidote for the direct thrombin inhibitor dabigatran, reversal strategies for the direct factor Xa inhibitors have been a focal point in clinical care over the past years. In the absence of specific reversal agents, the off-label use of (activated) prothrombin complex concentrate and recombinant factor VIIa have been suggested as effective treatment options during inhibitor-induced bleeding complications. Meanwhile, several specific reversal agents have been developed. In this review, an overview of the current state of nonspecific and specific reversal agents for the direct factor Xa inhibitors is provided, focusing on the biochemistry and mechanism of action and the preclinical assessment of newly emerging therapies.

Expedient Approach to the Synthesis of Betrixaban

A new scalable route to synthesize the factor Xa (FXa) inhibitor betrixaban is disclosed. The product is obtained in a seven-step reaction sequence (in five stages using two one-pot reactions) starting from easily accessible 4-(N,N-dimethylcarbamimidoyl)benzoate. Effective isolation of intermediates, use of cost-effective amide formation and 2-methyltetrahydrofuran as an effective reaction solvent as well as for extraction in three of the stages, are key features. The strategy provides the desired product in 38% overall yield with high purity (>98%).

Coagulation modifiers targeting SARS-CoV-2 main protease Mpro for COVID-19 treatment: an in silico approach

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection depends on viral polyprotein processing, catalysed by the main proteinase (Mpro). The solution of the SARS-CoV-2 Mpro structure allowed the investigation of potential inhibitors. This work aims to provide first evidences of the applicability of commercially approved drugs to treat coronavirus disease-19 (COVID-19). We screened 4,334 compounds to found potential inhibitors of SARS-CoV-2 replication using an in silico approach. Our results evidenced the potential use of coagulation modifiers in COVID-19 treatment due to the structural similarity of SARS-CoV-2 Mpro and human coagulation factors thrombin and Factor Xa. Further in vitro and in vivo analysis are needed to corroborate these results.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

New factor Xa inhibitors based on 1,2,3,4-tetrahydroquinoline developed by molecular modelling

Factor Xa is a serine protease representing a crucial element in the coagulation process and an attractive target for anticoagulant therapy. At the present time there are several chemical classes of factor Xa inhibitors with proven activity. Furthermore, three factor Xa inhibitors have been approved for the medical use to date. However, therapy with these medications is accompanied by substantial adverse effects. In this background, the structure-based computational approach combining molecular docking and semiempirical quantum chemical calculations was applied for a search for new effective factor Xa inhibitors. We have undertaken a few virtual screening procedures to select potential candidates for synthesis and subsequent testing. The first screen of the focused library resulted in identifying 20 compounds among which 7 compounds showed the noticeable inhibition of factor Xa at maximal concentrations, allowed by solubility. The subsequent additional screens identified 20 additional candidates. Of these, 5 substances were shown to be capable of inhibiting factor Xa at 5 μM. The best two found 1,2,3,4-tetrahydroquinoline derivatives identified by means of modelling have demonstrated IC50 values in the micromolar range. One of them turned out to be selective factor Xa inhibitor over trypsin, factors IIa, IXa and XIa.

Betrixaban in the prevention of venous thromboembolism in medically ill patients

Despite significant advances in strategies and compliance with venous thromboembolism (VTE) prophylaxis, hospital-acquired VTE remains a leading cause of preventable deaths in acute medically ill patients. A majority of venous thromboembolic events occur posthospital discharge when risk factors persist and pharmacoprophylactic regimens have been completed. Until recently, there has been an unmet need for safe and effective extended-duration VTE prevention. Three major trials evaluated this concept, but excess bleeding outweighed the benefit of reduced thromboembolic events. Betrixaban is an oral direct factor Xa inhibitor recently approved for extended-duration VTE prophylaxis in acute medically ill patients at risk for thromboembolism based on results from the Phase III APEX study. This article reviews the pharmacology and supporting data for betrixaban.

Betrixaban for first-line venous thromboembolism prevention in acute medically ill patients with risk factors for venous thromboembolism

INTRODUCTION

Compared to other direct oral anticoagulants, betrixaban has a longer half-life, smaller peak-trough variance, minimal renal clearance, and minimal hepatic Cytochrome P (CYP) metabolism. The Acute Medically Ill VTE Prevention with Extended Duration Betrixaban (APEX) trial evaluated the efficacy and safety of extended duration betrixaban compared to standard duration enoxaparin in acutely ill hospitalized patients. Areas covered: This article describes the role of betrixaban in the prevention of venous thromboembolism (VTE) in acutely ill medical patients. This article provides a consolidated summary of the primary APEX study findings as well as prespecified and exploratory substudies. This article also provides a review of the results of studies in which other direct factor Xa inhibitors have been evaluated in an extended duration regimen in this patient population. Expert commentary: While previous agents have demonstrated that extended duration VTE prophylaxis can be efficacious, betrixaban is the first agent to demonstrate efficacy without an increase in major bleeding. The totality of the data from the APEX trial supports extended duration betrixaban for VTE prophylaxis in the acute medically ill patient population. As such, betrixaban has been approved in the USA for extended VTE prophylaxis in at-risk acute medically ill patients.

Cu(OAc)2-Promoted Ortho C(sp2)-H Amidation of 8-Aminoquinoline Benzamide with Acyl Azide: Selective Formation of Aroyl or Acetyl Amide Based on Catalyst Loading

An efficient method for the C(sp²) amidation of 8-aminoquinoline benzamide by acyl azide in the presence of copper acetate has been achieved via C-H activation. Interestingly, the loading of copper acetate has a strong influence on the outcome of the reaction. The use of 1 equiv of copper acetate produces the corresponding aroyl amide, whereas the use of 2 equiv led to acetyl amide. A series of substituted benzoyl and acetyl amides has been obtained.

Pharmacokinetic drug interactions of the non-vitamin K antagonist oral anticoagulants (NOACs)

The use of warfarin, the most commonly prescribed oral anticoagulant, is being questioned by clinicians worldwide due to warfarin several limitations (a limited therapeutic window and significant variability in dose-response among individuals, in addition to a potential for drug-drug interactions). Therefore, the need for non-vitamin K antagonist oral anticoagulants (NOACs) with a rapid onset of antithrombotic effects and a predictable pharmacokinetic (PK) and pharmacodynamic (PD) profile led to the approval of five new drugs: the direct factor Xa (F-Xa) inhibitors rivaroxaban, apixaban, edoxaban and betrixaban (newly approved by FDA) and the direct thrombin (factor-IIa) inhibitor dabigatran etexilate. The advantages of NOACs over warfarin are a fixed-dosage, the absence of the need for drug monitoring for changes in anti-coagulation and fewer clinically significant PK and PD drug-drug interactions. NOACs exposure will likely be increased by the administration of strong P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4-inhibitors and may increase the risk of bleeds. On the contrary, P-gp inducers could significantly decrease the NOACs plasma concentration with an associated reduction in their anticoagulant effects. This manuscript gives an overview of NOACs PK profiles and their drug-drug interactions potential. This is meant to be of help to physicians in choosing the best therapeutic approach for their patients.

Pharmacological properties of betrixaban

Venous thromboembolism (VTE) in acute medically ill patients is a leading cause of in-hospital morbidity and mortality. A majority of these VTE events occur post-discharge, and patients remain at increased VTE risk for up to 3 months post-discharge. Recent clinical trials of extended-duration thromboprophylaxis with enoxaparin, rivaroxaban, and apixaban in acute medically ill patients did not demonstrate a net clinical benefit compared with in-hospital thromboprophylaxis, and were shown to be associated with higher risks of major bleeding. Betrixaban is a new direct oral anticoagulant (DOAC) with a different pharmacokinetic profile than other DOACs. Betrixaban has the longest half-life among the DOAC class, with a terminal half-life of 35-45 h and an effective half-life of 19-27 h. Betrixaban has a low peak-to-trough ratio compared with other anticoagulants and a predictable duration of drug exposure, leading to overall consistent anticoagulant effect over 24 h. Betrixaban is mainly cleared via the hepatobiliary system and therefore not contraindicated in patients with severe renal insufficiency. Betrixaban was recently approved for the indication of extended thromboprophylaxis in the United States based on the APEX trial of betrixaban 80 mg once daily for 35-42 days compared with low molecular weight heparin enoxaparin for 10 ± 4 days in hospitalized acute medically ill patients. This study demonstrated that extended-duration betrixaban reduced VTE compared with standard-duration enoxaparin in acute medically ill patients, without increased risk of major bleeding. This patient population at risk of VTE may benefit from extended prophylaxis, ensuring continuum of care from in-hospital to post-discharge.

The Development of New Factor Xa Inhibitors Based on Amide Synthesis

BACKGROUND

Factor Xa (FXa) is known to play a central role in blood coagulation cascade and considered to be one of the most attractive targets for oral anticoagulants of new generation.

OBJECTIVE

Our approach for the development of directly acting oral anticoagulants (DOAC), FXa inhibitors was demonstrated in this work.

METHOD

Chemical synthesis is the base of our approach for the development of potential inhibitors. In this work, the substances like R1-(CONH)-R2-(CONH)-R3 are being developed, using previously described docking and screening methods, where R1, R2 and R3 are some chemical groups and (CONH) are amide bonds connecting R1, R2 and R3. The direction of amide bond (CONH) could be arbitrary for R1, R2 and R2, R3.

RESULTS

Chemical modifications were made in the frame of the results, taking into account the structure of FXa, chemical synthesis capabilities, as well as patentability of the target compounds. Subnanomolar potency of several developed compounds was achieved. Several analyzers and various testing-suites have been used to measure the concentration that doubled the prothrombin time (PTx2). Moreover, in human plasma the PTx2 concentration of the compound 217 (DD217) turned out to be 80±20 nM. The compound efficacy has proved by in vivo assays including oral administrations in rats, rabbits and monkeys.

CONCLUSION

The pharmacodynamic profile of DD217 for oral administration in cynomolgus monkeys proves the efficacy of the compound, which makes it promising for the future preclinical trials.

The safety and efficacy of full- versus reduced-dose betrixaban in the Acute Medically Ill VTE (Venous Thromboembolism) Prevention With Extended-Duration Betrixaban (APEX) trial

BACKGROUND

The APEX trial assessed the safety and efficacy of extended-duration thromboprophylaxis using betrixaban versus standard dosing of enoxaparin among hospitalized, acutely ill medical patients. The 80-mg betrixaban dose was halved to 40 mg among subjects with severe renal insufficiency and those receiving a concomitant strong P-glycoprotein inhibitor.

METHODS

This analysis assessed the pharmacokinetics, efficacy, and safety of full- (80 mg) and reduced-dose (40 mg) betrixaban relative to enoxaparin in the APEX trial.

RESULTS

The median concentration of betrixaban among subjects administered the 80-mg dose was higher than that of the 40-mg dose (19 ng/mL vs 11 ng/mL, P<.001). In the primary analysis cohort 1 (d-dimer ≥2× upper limit of normal), the primary efficacy outcome (asymptomatic proximal deep vein thrombosis, symptomatic proximal or distal deep vein thrombosis, symptomatic nonfatal pulmonary embolism, or venous thromboembolism-related death) was significantly reduced among subjects treated with 80 mg of extended-duration betrixaban versus enoxaparin (6.27% [95/1516] vs 8.39% [130/1549], relative risk reduction=0.26 [0.04-0.42], P=.023), and similarly in the entire primary efficacy outcome population (4.87% [122/2506] vs 7.06% [181/2562], relative risk reduction=0.30 [0.13-0.44], P=.001). There was no difference in the primary outcome for subjects treated with 40 mg betrixaban vs enoxaparin across cohorts. In addition, there was no excess of major bleeding associated with either betrixaban dose compared with enoxaparin.

CONCLUSIONS

The 80-mg betrixaban dose achieves higher plasma concentrations than the 40-mg dose and, in contrast to the 40-mg dose, is associated with improved efficacy across all cohorts relative to standard-dose enoxaparin without an excess risk of major bleeding in the management of medically ill subjects.

Design, synthesis and biological evaluation of novel 2,3-dihydroquinazolin- 4(1H)-one derivatives as potential fXa inhibitors

Coagulation factor Xa (fXa) is a particularly attractive target for the development of effective and safe anticoagulants. In this study, novel 2,3-dihydroquinazolin-4(1H)-one derivatives were designed as potential fXa inhibitors based on anthranilamide structure which has been reported in our previous research. The experimental data showed that most of the designed compounds exhibited significant in vitro potency against fXa. Among them, compound 8e displayed the strongest potency against fXa with the IC₅₀ value of 21 nM and highly selectivity versus thrombin (IC₅₀ = 67 μM) and excellent in vitro antithrombotic activity with its 2 × PT value of 1.2 μM and 2 × aPTT value of 0.6 μM. In addition, 8e also displayed excellent in vivo antithrombotic activity in the rat arteriovenous shunt (AV-SHUNT) model. The bleeding risk evaluation showed that 8e had a similar safety profile as that of betrixaban. All results demonstrated that compound 8e could be considered as a potential fXa inhibitor for the prevention and treatment of thromboembolic diseases.

Contemporary developments in the discovery of selective factor Xa inhibitors: A review

Thrombosis is a leading cause of death in cardiovascular diseases such as myocardial infarction (MI), unstable angina and acute coronary syndrome (ACS) in the industrialized world. Venous thromboembolism is observed in about 1 million people every year in United States causing significant morbidity and mortality. Conventional antithrombotic therapy has been reported to have several disadvantages and limitations like inconvenience in oral administration, bleeding risks (heparin analogs), narrow therapeutic window and undesirable interactions with food and drugs (vitamin K antagonist-warfarin). The unmet medical demand for orally active safe anticoagulants has generated widespread interest among the medicinal chemists engaged in this field. To modulate blood coagulation, various enzymes involved in the coagulation process have received great attention as potential targets by various research groups for the development of oral anticoagulants. Among these enzymes, factor Xa (FXa) has remained the centre of attention in the last decade. Intensive research efforts have been made by various research groups for the development of small, safe and orally bioavailable FXa inhibitors. This review is an attempt to compile the research work of various researchers in the direction of development of FXa inhibitors reported since 2010 onward.

A Facile Method for the Synthesis of Betrixaban

A facile method for the synthesis of N-(5-chloropyridin-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxybenzamide (Betrixaban) from 5-methoxy-2-nitrobenzoic acid is achieved by reduction, acylation, chlorination, acylation and the formation of the amidine. A dechlorinated impurity is avoided in this method. Using tetrahydrofuran as the solvent in the four steps makes its recovery easier. The total yield of the target compound is about 40% and this method is suitable for large-scale production.

Profile of betrixaban and its potential in the prevention and treatment of venous thromboembolism

Venous thromboembolism (VTE), which includes deep vein thrombosis and pulmonary embolism, is a common and potentially preventable cause of morbidity and mortality. Unfractionated heparin, low-molecular-weight heparin, and warfarin have been the cornerstone of VTE prevention and treatment but are being replaced by recently approved non-vitamin K antagonist oral anticoagulants (NOACs): dabigatran, rivaroxaban, apixaban, and edoxaban. The NOACs are at least as effective and as safe as heparins and warfarin for VTE prevention and treatment and are more convenient because they have a low propensity for food and drug interactions and are given in fixed doses without routine coagulation monitoring. The remaining limitations of currently available NOACs include their dependence on renal and hepatic function for clearance, and the lack of an approved antidote. Betrixaban is a new NOAC with distinct pharmacological characteristics: minimal renal clearance, minimal hepatic metabolism, and long half-life. It has undergone successful Phase II studies in orthopedic thromboprophylaxis, and in stroke prevention in atrial fibrillation. Currently, it is being evaluated in a Phase III trial of extended thromboprophylaxis in medical patients (APEX study). In this article, we describe the development of betrixaban, review its pharmacological profile, discuss the results of clinical trials, and examine its potential for VTE prevention and treatment.

Global assays and the management of oral anticoagulation

Coagulation tests range from global or overall tests to assays specific to individual clotting factors and their inhibitors. Whether a particular test is influenced by an oral anticoagulant depends on the principle of the test and the type of oral anticoagulant. Knowledge on coagulation tests applicable in monitoring status and reversal of oral anticoagulation is a prerequisite when studying potential reversal agents or when managing anticoagulation in a clinical setting. Specialty tests based on the measurement of residual activated factor X (Xa) or thrombin activity, e.g., are highly effective for determining the concentration of the new generation direct factor Xa- and thrombin inhibitors, but these tests are unsuitable for the assessment of anticoagulation reversal by non-specific prohemostatic agents like prothrombin complex concentrate (PCC) and recombinant factor VIIa (FVIIa). Global coagulation assays, in this respect, seem more appropriate. This review evaluates the current status on the applicability of the global coagulation assays PT, APTT, thrombin generation and thromboelastography in the management of oral anticoagulation by vitamin K antagonists and the direct factor Xa and thrombin inhibitors. Although all global tests are influenced by both types of anticoagulants, not all tests are useful for monitoring anticoagulation and reversal thereof. Many (pre)analytical conditions are of influence on the assay readout, including the oral anticoagulant itself, the concentration of assay reagents and the presence of other elements like platelets and blood cells. Assay standardization, therefore, remains an issue of importance.

Structure-function relationships of factor Xa inhibitors: implications for the practicing clinician

The recent development and approval of novel oral anticoagulants represents a significant success in the intelligent design of target-specific therapeutics. However, while these agents obviate many of the shortcomings of their predecessor (warfarin), they present novel challenges in pharmacologic management as well. Each was designed to have high oral bioavailability and high affinity for its target molecule, conveying significant anticoagulant effects. Yet, such unique drug-ligand binding, coupled with unfamiliar drug interactions and renal-based clearance, represent challenges to clinical management. The current review describes the development and pharmacokinetic properties of these agents, in the context of their clinical utility and pitfalls.

Pharmacology and laboratory testing of the oral Xa inhibitors

New oral factor Xa inhibitors are intended to progressively substitute the oral vitamin K antagonists and parenteral indirect inhibitors of factor Xa in the prevention and treatment of venous and arterial thromboembolic episodes. This article focuses on the main clinical studies and on biological measurements of new oral factor Xa inhibitors, and addresses several safety issues. These newer agents do not require any routine laboratory monitoring of blood coagulation; however, biological tests have been developed in order to assess the plasma concentration of these drugs in several clinical settings. This article reviews these 4 oral direct factor Xa inhibitors.

Synthesis and biological evaluation of substituted 4-(thiophen-2-ylmethyl)-2H-phthalazin-1-ones as potent PARP-1 inhibitors

We have developed a series of substituted 4-(thiophen-2-ylmethyl)-2H-phthalazin-1-ones as potent PARP-1 inhibitors. Preliminary biological evaluation indicated that most compounds possessed inhibitory potencies comparable to, or higher than AZD-2281. Among these compounds, 18q appeared to be the most notable one, which displayed an 8-fold improvement in enzymatic activity compared to AZD-2281. These efforts lay the foundation for our further investigation.