Efficacious and Orally Bioavailable Thrombin Inhibitors Based on a 2,5-Thienylamidine at the P1 Position: Discovery ofN-Carboxymethyl-d-diphenylalanyl-l-prolyl[(5-amidino-2-thienyl)methyl]amide
- 12 July 2003
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of Medicinal Chemistry
- Vol. 46 (17), 3612-3622
- https://doi.org/10.1021/jm030025j
Abstract
Thrombin, a crucial enzyme in the blood coagulation, has been a target for antithrombotic therapy. Orally active thrombin inhibitors would provide effective and safe prophylaxis for venous and arterial thrombosis. We conducted optimization of a highly efficacious benzamidine-based thrombin inhibitor LB30812 (3, Ki = 3 pM) to improve oral bioavailability. Of a variety of arylamidines investigated at the P1 position, 2,5-thienylamidine effectively replaced the benzamidine without compromising the thrombin inhibitory potency and oral absorption. The sulfamide and sulfonamide derivatization at the N-terminal position in general afforded highly potent thrombin inhibitors but with moderate oral absorption, while the well-absorbable N-carbamate derivatives exhibited limited metabolic stability in S9 fractions. The present work culminated in the discovery of the N-carboxymethyl- and 2,5-thienylamidine-containing compound 22 that exhibits the most favorable profiles of anticoagulant and antithrombotic activities as well as oral bioavilability (Ki = 15 pM; F = 43%, 42%, and 15% in rats, dogs, and monkeys, respectively). This compound on a gravimetric basis was shown to be more effective than a low molecular weight heparin, enoxaparin, in the venous thrombosis models of rat and rabbit. Compound 22 (LB30870) was therefore selected for further preclinical and clinical development.Keywords
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