Discovery of a High Affinity, Orally Bioavailable Macrocyclic FXIa Inhibitor with Antithrombotic Activity in Preclinical Species.

Oral factor XIa (FXIa) inhibitors may provide a promising new antithrombotic therapy with an improved benefit to bleeding risk profile over existing antithrombotic agents. Herein, we report application of a previously disclosed cyclic carbamate P1 linker which provided improved oral bioavailability in the imidazole-based 13-membered macrocycle to the 12-membered macrocycle. This resulted in identification of compound 4 with desired FXIa inhibitory potency and good oral bioavailability but high in vivo clearance. Further structure-activity relationship (SAR) studies of heterocyclic core modifications to replace the imidazole core as well as various linkers to the P1 group led to the discovery of compound 6f, a potent FXIa inhibitor with selectivity against most of the relevant serine proteases. Compound 6f also demonstrated excellent pharmacokinetics (PK) profile (high oral bioavailability and low clearance) in multiple preclinical species. Compound 6f achieved robust antithrombotic efficacy in a rabbit efficacy model at doses which preserved hemostasis.

The P2Y1 receptor antagonist MRS2500 prevents carotid artery thrombosis in cynomolgus monkeys.

Adenosine diphosphate directly induces platelet aggregation via the G-protein coupled P2Y1 and P2Y12 receptors. P2Y12, but not P2Y1, receptor antagonists are available in the clinic. The relevance of the P2Y1 receptor as an antiplatelet target has been studied in rodents, but not in higher species. We therefore examined effects of the pharmacological blockade of the P2Y1 receptor with its selective antagonist MRS2500 in monkey models of electrolytic-mediated arterial thrombosis (ECAT) and kidney bleeding time (KBT). Abciximab, a GPIIb-IIIa antagonist, and cangrelor, a P2Y12 antagonist, were utilized to validate these monkey models. Compounds were given IV at 15-60 min before thrombosis initiation in anesthetized monkeys. Scanning electron microscopy showed the luminal surface of thrombotic artery covered with platelet aggregates and fibrin network. Administration of abciximab at 0.25 and 0.7 mg/kg IV significantly reduced thrombus weight by 71 ± 1 and 100 ± 0 %, and increased KBT by 10.0 ± 0.1- and 10.1 ± 0-fold, respectively (n = 3/dose). Likewise, cangrelor at 0.6 and 2 mg/kg/h IV significantly reduced thrombus weight significantly by 72 ± 9 % and 100 ± 0 % and increased KBT by 2.1 ± 0.1- and 9.8 ± 0.2-fold, respectively (n = 3/dose). MRS2500 [mg/kg + mg/kg/h IV] at 0.09 + 0.14 and 0.45 + 0.68 significantly reduced thrombus weight by 57 ± 1 % and 88 ± 1 % and increased KBT by 2.1 ± 0.3- and 4.9 ± 0.6-fold, respectively (n = 4/dose). In summary, MRS2500 prevented occlusive arterial thrombosis at a dose that moderately prolonged KBT, indicating a role of P2Y1 receptors in arterial thrombosis and hemostasis in monkeys. Thus P2Y1 receptor antagonism provides a suitable target for drug discovery.

Discovery of diarylurea P2Y(1) antagonists with improved aqueous solubility.

Preclinical data suggests that P2Y1 antagonists, such as diarylurea compound 1, may provide antithrombotic efficacy similar to P2Y12 antagonists and may have the potential of providing reduced bleeding liabilities. This manuscript describes a series of diarylureas bearing solublizing amine side chains as potent P2Y1 antagonists. Among them, compounds 2l and 3h had improved aqueous solubility and maintained antiplatelet activity compared with compound 1. Compound 2l was moderately efficacious in both rat and rabbit thrombosis models and had a moderate prolongation of bleeding time in rats similar to that of compound 1.

A small-molecule factor XIa inhibitor produces antithrombotic efficacy with minimal bleeding time prolongation in rabbits.

BMS-262084 is a 4-carboxy-2-azetidinone-containing irreversible inhibitor of FXIa, which is selective over other coagulation proteases. We evaluated the in vitro and in vivo properties of BMS-262084 in rabbits. Studies were conducted in arteriovenous-shunt thrombosis (AVST), venous thrombosis (VT), electrolytic-mediated carotid arterial thrombosis (ECAT) and cuticle bleeding time (BT) models. BMS-262084 was infused IV from 1 h before thrombus induction or cuticle transection to the end of the experiment. In vitro, BMS-262084 prolonged activated partial thromboplastin time (aPTT) with EC(2x) (concentration required to double aPTT) of 10.6 µM in rabbit plasma, and did not prolong prothrombin time (PT), thrombin time (TT) and HepTest. In vivo, BMS-262084 produced dose-dependent antithrombotic effects in rabbits with antithrombotic ED(50) (dose that reduced thrombus weight or increased blood flow by 50% of the control) in AVST, VT and ECAT of 0.4, 0.7 and 1.5 mg/kg/h IV, respectively. BMS-262084 increased ex vivo aPTT dose-dependently without changes in PT and TT. The antithrombotic effect of BMS-262084 was significantly correlated with its ex vivo aPTT, supporting the use of ex vivo aPTT as a pharmacodynamic biomarker. BMS-262084 did not alter ex vivo rabbit platelet aggregation to ADP and collagen. BT (fold-increase) determined at 3 and 10 mg/kg/h of BMS-262084 were 1.17 ± 0.04 and 1.52 ± 0.07*, respectively (*P < 0.05 vs. control). This study demonstrated that BMS-262084 prevented experimental thrombosis at doses with low BT effects in rabbits, and suggests that a small molecule FXIa inhibitor may represent a promising antithrombotic therapy.