Design and Preclinical Characterization Program toward Asundexian (BAY 2433334), an Oral Factor XIa Inhibitor for the Prevention and Treatment of Thromboembolic Disorders.

Activated coagulation factor XI (FXIa) is a highly attractive antithrombotic target as it contributes to the development and progression of thrombosis but is thought to play only a minor role in hemostasis so that its inhibition may allow for decoupling of antithrombotic efficacy and bleeding time prolongation. Herein, we report our major efforts to identify an orally bioavailable, reversible FXIa inhibitor. Using a protein structure-based de novo design approach, we identified a novel micromolar hit with attractive physicochemical properties. During lead modification, a critical problem was balancing potency and absorption by focusing on the most important interactions of the lead series with FXIa while simultaneously seeking to improve metabolic stability and the cytochrome P450 interaction profile. In clinical trials, the resulting compound from our extensive research program, asundexian (BAY 2433334), proved to possess the desired DMPK properties for once-daily oral dosing, and even more importantly, the initial pharmacological hypothesis was confirmed.

Pharmacological profile of asundexian, a novel, orally bioavailable inhibitor of factor XIa.

BACKGROUND: Activated coagulation factor XI (FXIa) contributes to the development and propagation of thrombosis but plays only a minor role in hemostasis; therefore, it is an attractive antithrombotic target. OBJECTIVES: To evaluate the pharmacology of asundexian (BAY 2433334), a small molecule inhibitor targeting FXIa, in vitro and in various rabbit models. METHODS: The effects of asundexian on FXIa activity, selectivity versus other proteases, plasma thrombin generation, and clotting assays were evaluated. Antithrombotic effects were determined in FeCl2 - and arterio-venous (AV) shunt models. Asundexian was administered intravenously or orally, before or during thrombus formation, and with or without antiplatelet drugs (aspirin and ticagrelor). Potential effects of asundexian on bleeding were evaluated in ear-, gum-, and liver injury models. RESULTS: Asundexian inhibited human FXIa with high potency and selectivity. It reduced FXIa activity, thrombin generation triggered by contact activation or low concentrations of tissue factor, and prolonged activated partial thromboplastin time in human, rabbit, and various other species, but not in rodents. In the FeCl2 -injury models, asundexian reduced thrombus weight versus control, and in the arterial model when added to aspirin and ticagrelor. In the AV shunt model, asundexian reduced thrombus weight when administered before or during thrombus formation. Asundexian alone or in combination with antiplatelet drugs did not increase bleeding times or blood loss in any of the models studied. CONCLUSIONS: Asundexian is a potent oral FXIa inhibitor with antithrombotic efficacy in arterial and venous thrombosis models in prevention and intervention settings, without increasing bleeding.

Design, Synthesis, and Pharmacological Characterization of a Neutral, Non-Prodrug Thrombin Inhibitor with Good Oral Pharmacokinetics.

Despite extensive research on small molecule thrombin inhibitors for oral application in the past decades, only a single double prodrug with very modest oral bioavailability has reached human therapy as a marketed drug. We have undertaken major efforts to identify neutral, non-prodrug inhibitors. Using a holistic analysis of all available internal data, we were able to build computational models and apply these for the selection of a lead series with the highest possibility of achieving oral bioavailability. In our design, we relied on protein structure knowledge to address potency and identified a small window of favorable physicochemical properties to balance absorption and metabolic stability. Protein structure information on the pregnane X receptor helped in overcoming a persistent cytochrome P450 3A4 induction problem. The selected compound series was optimized to a highly potent, neutral, non-prodrug thrombin inhibitor by designing, synthesizing, and testing derivatives. The resulting optimized compound, BAY1217224, has reached first clinical trials, which have confirmed the desired pharmacokinetic properties.

Oral, direct thrombin and factor†Xa inhibitors: the replacement for warfarin, leeches, and pig intestines?

To prevent thromboses after surgery, patients have until now had to inject themselves daily with heparin. For stroke prophylaxis in atrial fibrillation, patients take vitamin K antagonists of the coumarin type, which have a narrow therapeutic window and whose dosage must be regularly monitored. In order to improve the standard of therapy in thromboembolic diseases such as deep-vein thrombosis, pulmonary embolism, and stroke in atrial fibrillation, intensive research has been carried out over the last decade in the search for new, orally active thrombin and factor Xa inhibitors. A number of these compounds are already on the market or are in advanced clinical development; they could revolutionize the anticoagulant market.

The discovery and development of rivaroxaban, an oral, direct factor Xa inhibitor.

The activated serine protease factor Xa is a promising target for new anticoagulants. After studies on naturally occurring factor Xa inhibitors indicated that such agents could be effective and safe, research focused on small-molecule direct inhibitors of factor Xa that might address the major clinical need for improved oral anticoagulants. In 2008, rivaroxaban (Xarelto; Bayer HealthCare) became the first such compound to be approved for clinical use. This article presents the history of rivaroxaban's development, from the structure-activity relationship studies that led to its discovery to the preclinical and clinical studies, and also provides a brief overview of other oral anticoagulants in advanced clinical development.

Rivaroxaban: a new oral factor Xa inhibitor.

Rivaroxaban is a direct inhibitor of factor Xa, a coagulation factor at a critical juncture in the blood coagulation pathway leading to thrombin generation and clot formation. It is selective for human factor Xa, for which it has >10 000-fold greater selectivity than for other biologically relevant serine proteases (half-maximal inhibitory concentration [IC(50)], >20 micromol/L). Rivaroxaban inhibits factor Xa in a concentration-dependent manner (inhibitory constant [K(i)], 0.4 nmol/L) and binds rapidly (kinetic association rate constant [k(on)], 1.7x10(7) mol/L(-1) s(-1)) and reversibly (kinetic dissociation rate constant [k(off)], 5x10(-3) s(-1)). By inhibiting prothrombinase complex-bound (IC(50), 2.1 nmol/L) and clot-associated factor Xa (IC(50), 75 nmol/L), rivaroxaban reduces the thrombin burst during the propagation phase. In animal models of venous and arterial thrombosis, rivaroxaban showed dose-dependent antithrombotic activity. In healthy individuals, rivaroxaban was found to have predictable pharmacokinetics and pharmacodynamics across a 5- to 80-mg total daily dose range, inhibiting factor Xa activity and prolonging plasma clotting time. In phase III clinical trials, rivaroxaban regimens reduced rates of venous thromboembolism in patients after total hip or knee arthroplasty compared with enoxaparin regimens, without significant differences in rates of major bleeding, showing that rivaroxaban has a favorable benefit-to-risk profile.

Entering the era of non-basic p1 site groups: discovery of Xarelto (Rivaroxaban).

Several clinical candidates have now emerged as a result of an intense search for orally available, antithrombotic factor Xa inhibitors. This review highlights the discovery of XareltoTM (Rivaroxaban) starting from an initial tetrahydrophthalimide screening hit. The major breakthrough was the finding that a chlorothiophene moiety can undergo an interaction in the S1 binding site thus leading to high potency combined with favorable oral bioavailability. The binding mode of this P1 moiety is discussed, and further non-basic S1 binders of this new type are reviewed.

Discovery of the novel antithrombotic agent 5-chloro-N-({(5S)-2-oxo-3- [4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl}methyl)thiophene- 2-carboxamide (BAY 59-7939): an oral, direct factor Xa inhibitor.

Despite recent progress in antithrombotic therapy, there is still an unmet medical need for safe and orally available anticoagulants. The coagulation enzyme Factor Xa (FXa) is a particularly promising target, and recent efforts in this field have focused on the identification of small-molecule inhibitors with good oral bioavailability. We identified oxazolidinone derivatives as a new class of potent FXa inhibitors. Lead optimization led to the discovery of BAY 59-7939 (5), a highly potent and selective, direct FXa inhibitor with excellent in vivo antithrombotic activity. The X-ray crystal structure of 5 in complex with human FXa clarified the binding mode and the stringent requirements for high affinity. The interaction of the neutral ligand chlorothiophene in the S1 subsite allows for the combination of good oral bioavailability and high potency for nonbasic 5. Compound 5 is currently under clinical development for the prevention and treatment of thromboembolic diseases.