Compound 15 (SAR107375), a novel potent dual thrombin and factor Xa inhibitor resulted from a rational optimization process. Starting from compound 14, with low factor Xa and modest anti-thrombin inhibitory activities (IC50's of 3.5 and 0.39 μM, respectively), both activities were considerably improved, notably through the incorporation of a neutral chlorothiophene P1 fragment and tuning of P2 and P3-P4 fragments. Final optimization of metabolic stability with microsomes led to the identification of 15, which displays strong activity in vitro vs factor Xa and thrombin (with Ki's of 1 and 8 nM, respectively). In addition 15 presents good selectivity versus related serine proteases (roughly 300-fold), including trypsin (1000-fold), and is very active (0.39 μM) in the thrombin generation time (TGT) coagulation assay in human platelet rich plasma (PRP). Potent in vivo activity in a rat model of venous thrombosis following iv and, more importantly, po administration was also observed (ED50 of 0.07 and 2.8 mg/kg, respectively). Bleeding liability was reduced in the rat wire coil model, more relevant to arterial thrombosis, with 15 (blood loss increase of 2-fold relative to the ED80 value) compared to rivaroxaban 2 and dabigatran etexilate 1a.

In the search of a potential backup for clopidogrel, we have initiated a HTS campaign designed to identify novel reversible P2Y12 antagonists. Starting from a hit with low micromolar binding activity, we report here the main steps of the optimization process leading to the identification of the preclinical candidate SAR216471. It is a potent, highly selective, and reversible P2Y12 receptor antagonist and by far the most potent inhibitor of ADP-induced platelet aggregation among the P2Y12 antagonists described in the literature. SAR216471 displays potent in vivo antiplatelet and antithrombotic activities and has the potential to differentiate from other antiplatelet agents.

The disposition of tiludronate in mouse, rat, rabbit, dog and monkey has been studied after oral and intravenous doses. Like other bisphosphonates, tiludronate was characterized by poor absorption from the gastrointestinal tract. Peak plasma concentrations appeared shortly (0.5-1 h) after dosing, except for the baboon (4.5 h). Food intake highly impaired intestinal absorption The affinity of tiludronate for bone and the slow release from this deep compartment could account for the large volume of distribution and the low plasma clearance found in all species. Tiludronate has low affinity for red blood cells and binds moderately to serum proteins, mainly to serum albumin. Calcified tissues appeared to be the main target for deposition. Distribution into bone was not homogenous, with higher levels in the trabecular bone than in the corticol part of the long bones. The uptake of tiludronate into bone was unequivocally less in the older animal. No metabolism occurred in the tested animal species. The major route of elimination of the absorbed drug is urine. Preclinical observations made with tiludronate, like with other bisphosphonates, were predictive of results obtained in clinical investigation.

The metabolism of 2-n-propyl-2-pentenoate (delta 2-VPA) was evaluated in human hepatic microsomal fractions. Two biotransformation pathways have been particularly investigated. In the presence of the cytochrome P-450 co-factor, NADPH, the main metabolites recovered were delta 3-VPA, delta 2,4-VPA and VPA. The glucuronidation of delta 2-VPA was also studied on various hepatic microsomal fractions using Brij 35 as activator and UDP-glucuronic acid as co-factor. A large interindividual variability occurred in this metabolic pathway. Km and Vmax were 0.85 mmol/l and 1.75 nmol.min-1.mg-1, respectively, for delta 2-VPA and 1.11 mmol/l and 5.71 nmol.min-1.mg-1 for VPA, respectively. The good correlation (r = 0.82; p less than 0.001) observed between the glucuronidation of VPA and delta 2-VPA as well as the mutual inhibition of each other's glucuronidation strongly suggests that (a) common single UDP-glucuronosyltransferase isoenzyme(s) was (were) involved in this glucuronidation step. The glucuronidation of specific substrates for various UDP-glucuronosyltransferase isoenzymes showed a good relationship between the glucuronidations of delta 2-VPA and morphine, a substrate for UDP-glucuronosyltransferase-2B. Moreover, morphine competitively inhibits delta 2-VPA glucuronidation. It seems the same isoenzyme or, at least, (a) very closely related isoenzyme(s) belonging to UDP-glucuronosyltransferase-2 isoenzyme, is involved in delta 2-VPA glucuronidation.

No abstract