Emmanuel Meyer

Optimization of 2-phenyl-pyrimidine-4-carboxamides towards potent, orally bioavailable and selective P2Y(12) antagonists for inhibition of platelet aggregation.

2-Phenyl-pyrimidine-4-carboxamide analogs were identified as P2Y12 antagonists. Optimization of the carbon-linked or nitrogen-linked substituent at the 6-position of the pyrimidine ring provided compounds with excellent ex vivo potency in the platelet aggregation assay in human plasma. Compound 23u met the objectives for activity, selectivity and ADMET properties.

4-((R)-2-{[6-((S)-3-Methoxypyrrolidin-1-yl)-2-phenylpyrimidine-4-carbonyl]amino}-3-phosphonopropionyl)piperazine-1-carboxylic Acid Butyl Ester (ACT-246475) and Its Prodrug (ACT-281959), a Novel P2Y12 Receptor Antagonist with a Wider Therapeutic Window in the Rat Than Clopidogrel.

Recent post hoc analyses of several clinical trials with P2Y12 antagonists showed the need for new molecules being fully efficacious as antiplatelet agents and having a reduced propensity to cause major bleeding. We have previously reported the discovery of the 2-phenylpyrimidine-4-carboxamide analogs as P2Y12 antagonists with nanomolar potency in the disease-relevant platelet aggregation assay in human plasma. Herein we present the optimization steps that led to the discovery of clinical candidate ACT-246475 (30d). The key step was the replacement of the carboxylic acid functionality by a phosphonic acid group which delivered the most potent molecules of the program. In addition, low in vivo clearance in rat and dog was achieved for the first time. Since the bioavailability of 30d was low in rat and dog, we developed the bis((isopropoxycarbonyl)oxy)methyl ester prodrug (ACT-281959, 45). Compound 30d showed efficacy in the rat ferric chloride thrombosis model when administered intravenously as parent or orally as its prodrug 45. Moreover, 30d displays a wider therapeutic window as compared to clopidogrel in the rat surgical blood loss model.

Advances in Antiplatelet Agents

Platelets are small circulating cells that are essential to maintain the integrity of blood vessels following injury. Any alteration in the interplay between platelets, the endothelium, and the coagulation cascade will put a subject at risk of bleeding or, conversely, of thrombosis. In this article, we focus on platelets as the central player in cardiovascular pathology, and we discuss the fundamental biological mechanisms leading to blood vessel occlusion and thus life-threatening ischemic diseases. We highlight the recent advances in the development of antiplatelet agents from a medicinal chemistry perspective and discuss new frontiers in platelet research.