Discovery of Potent & Selective Inhibitors of Activated Thrombin-Activatable Fibrinolysis Inhibitor for the Treatment of Thrombosis

• Published in: Journal of medicinal chemistry 2007-11, Vol.50 (24), p.6095-6103
• Main Authors: Bunnage, Mark E, Blagg, Julian, Steele, John, Owen, Dafydd R, Allerton, Charlotte, McElroy, Andrew B, Miller, Duncan, Ringer, Tracy, Butcher, Ken, Beaumont, Kevin, Evans, Karen, Gray, Andrew J, Holland, Stephen J, Feeder, Neil, Moore, Robert S, Brown, David G
• Format: Article
• Language: English
• Subjects: Amino Acids - chemical synthesis; Amino Acids - pharmacokinetics; Amino Acids - pharmacology; Animals; Binding Sites; Biological and medical sciences; Biological Availability; Blood Loss, Surgical - prevention & control; Blood. Blood coagulation. Reticuloendothelial system; Carboxypeptidase B - chemistry; Catalytic Domain; Crystallography, X-Ray; Dogs; Fibrinolysis - drug effects; Fibrinolytic Agents - chemical synthesis; Fibrinolytic Agents - pharmacokinetics; Fibrinolytic Agents - pharmacology; Half-Life; Humans; Imidazoles - chemical synthesis; Imidazoles - pharmacokinetics; Imidazoles - pharmacology; Male; Medical sciences; Models, Molecular; Molecular Structure; Pancreas - enzymology; Pharmacology. Drug treatments; Rabbits; Stereoisomerism; Structure-Activity Relationship; Swine; Thrombin - metabolism; Venous Thromboembolism - drug therapy
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm0702433

Thrombin-activatable fibrinolysis inhibitor (TAFI) has emerged as a key link between the coagulation and fibrinolysis cascades and represents a promising new target for the treatment of thrombosis. A novel series of imidazolepropionic acids has been designed that exhibit high potency against activated TAFI (TAFIa) and excellent selectivity over plasma carboxypeptidase N (CPN). Structure activity relationships suggest that the imidazole moiety plays a key role in binding to the catalytic zinc of TAFIa, and this has been supported by crystallographic studies using porcine pancreatic carboxypeptidase B as a surrogate for TAFIa. The SAR program led to the identification of 21 (TAFIa Ki = 10 nM, selectivity TAFIa/CPN > 1000) as a candidate for clinical development. Compound 21 exhibited antithrombotic efficacy in a rabbit model of venous thrombosis, yet had no effect on surgical bleeding in the rabbit. In addition, 21 exhibited an excellent preclinical and clinical pharmacokinetic profile, characterized by paracellular absorption, low clearance, and a low volume of distribution, fully consistent with its physicochemical properties of low molecular weight (MW = 239) and high hydrophilicity (log D = −2.8). These data indicate 21 (UK-396,082) has potential as a novel TAFIa inhibitor for the treatment of thrombosis and other fibrin-dependent diseases in humans.