Latest developments in anticoagulant drug discovery

Design, synthesis and biological evaluation of 6-chloro-quinolin-2-one derivatives as novel FXIa inhibitors

A series of 6-chloro-quinolin-2-one derivatives were designed and synthesized as FXIa inhibitors by exploration of P1, P1 prime and P2 prime groups. Each compound was accessed for inhibitory effect on FXIa and some of them were evaluated in the clotting assay. 14c demonstrated excellent in-vitro potency (FXIa IC50: 15 nM, 2 x aPTT: 6.8 μM) and good in-vivo efficacy (prolonged in-vivo aPTT by more than 1-fold but not PT). Moreover, the pharmacokinetics property of 14c were evaluated following intravenous administration in rats, which indicated that 14c probably will be a clinical candidate for intravenous administration.

Computer Design of Low-Molecular-Weight Inhibitors of Coagulation Factors

The review discusses main approaches to searching for new low-molecular-weight inhibitors of coagulation factors IIa, Xa, IXa, and XIa and the results of such studies conducted from 2015 to 2018. For each of these factors, several inhibitors with IC₅₀ < 10 nM have been found, some of which are now tested in clinical trials. However, none of the identified inhibitors meets the requirements for an "ideal" anticoagulant, so further studies are required.

Fragment-Based Lead Generation of 5-Phenyl-1H-pyrazole-3-carboxamide Derivatives as Leads for Potent Factor Xia Inhibitors

FXIa is suggested as a major target for anticoagulant drug discovery because of reduced risk of bleeding. In this paper, we defined 5-phenyl-1H-pyrazole-3-carboxylic acid derivatives as privileged fragments for FXIa inhibitors’ lead discovery. After replacing the (E)-3-(5-chloro-2-(1H-tetrazol-1-yl)phenyl)acrylamide moiety in compound 3 with 5-(3-chlorophenyl)-1H-pyrazole-3-carboxamide, we traveled from FXIa inhibitor 3 to a scaffold that fused the privileged fragments into a pharmacophore for FXIa inhibitors. Subsequently, we synthesized and assessed the FXIa inhibitory potency of a series of 5-phenyl-1H-pyrazole-3-carboxamide derivatives with different P1, P1′ and P2′moiety. Finally, the SAR of them was systematically investigated to afford the lead compound 7za (FXIa Ki = 90.37 nM, 1.5× aPTT in rabbit plasma = 43.33 μM) which exhibited good in vitro inhibitory potency against FXIa and excellent in vitro coagulation activities. Furthermore, the binding mode of 7za with FXIa was studied and the results suggest that the 2-methylcyclopropanecarboxamide group of 7za makes 2 direct hydrogen bonds with Tyr58B and Thr35 in the FXIa backbone, making 7za binds to FXIa in a highly efficient manner.

Future prospects for contact factors as therapeutic targets

Anticoagulants currently used in clinical practice to treat or prevent thromboembolic disease are effective, but place patients at increased risk for serious bleeding because they interfere with plasma enzymes (thrombin and factor Xa) that are essential for hemostasis. In the past 10 years, work with genetically altered mice and studies in baboons and rabbits have demonstrated that the plasma contact proteases factor XI, factor XII, and prekallikrein contribute to the formation of occlusive thrombi despite having limited roles in hemostasis. In the case of factor XI, epidemiologic data from human populations indicate that elevated levels of this protein increase risk for stroke and venous thromboembolism and may also influence risk for myocardial infarction. These findings suggest that inhibiting contact activation may produce an antithrombotic effect without significantly compromising hemostasis. This chapter reviews strategies that are being developed for therapeutic targeting of factor XI and factor XII and their performances in preclinical and early human trials.

Use of novel oral anticoagulants for the treatment of venous thromboembolism and its considerations in Asian patients

Parenteral anticoagulation followed by warfarin has been conventionally used for the treatment of venous thromboembolism (VTE). However, there are numerous troublesome characteristics of warfarin that prompted the development of novel oral anticoagulants (NOACs) for the treatment of VTE. Asians are reported to be at an increased risk of bleeding with warfarin, and while the reported incidence of VTE in Asians is lower than in Caucasians, the annual rate of VTE in Asia is rising along with the need for better oral anticoagulant options. Recently, several Phase III clinical trials with NOACs for the treatment and prevention of VTE recurrence have been published. For the treatment of VTE, the four NOACs - dabigatran, rivaroxaban, apixaban, and edoxaban - each showed comparable efficacy outcomes while resulting in better safety outcomes when compared with conventional treatment. In these trials, Asian patients had comparable efficacy and safety outcomes as other races, except in the edoxaban trial, in which the Asian subgroup had better safety profiles than other races, although further confirmation is necessary. For secondary prevention, dabigatran was compared with conventional treatment and showed similar efficacy and safety outcomes. When NOACs were compared with placebo for secondary prevention of VTE, they showed superior efficacy and increased bleeding except for apixaban, which showed comparable major bleeding and composite of major and clinically relevant nonmajor bleeding rates as placebo. No significant differences in the outcomes based on race were observed in the Asian subgroups for secondary prevention. Therefore, NOACs can be used with similar efficacy and at least similar or superior safety compared with conventional treatment in the treatment of VTE, and at no increased risk in Asian patients.