Analysis of highly potent amidine containing inhibitors of serine proteases and their N-hydroxylated prodrugs (amidoximes)

Abstract

The development of serine protease inhibitors often results in the discovery of new lead compounds containing strong basic amidine functions that usually suffer from poor absorption from the intestine. In order to improve oral bioavailability of these drugs, prodrug principles such as the conversion of amidines into amidoximes may be applied. In this work, two HPLC-based separation methods of serine protease inhibitors (amidines) and their N-hydroxylated prodrugs have been developed and characterised. This was performed by evaluating 11 distinct amidine-amidoxime pairs with different physicochemical parameters (clogP: −3 to 5.1). The HPLC methods developed allowed excellent separation of the compound pairs examined. Also, the possible selection of different separation techniques (i.e. adsorption- and ion-pair-chromatography) permits universal application. Moreover, both techniques are compatible with mass spectrometry and are superior to the previously described methods. In summary, both HPLC methods are suitable for the separation of most amidoxime-prodrugs currently in clinical or preclinical development.

Keywords::

• Serine protease inhibitor
• prodrug
• amidine
• amidoxime
• HPLC

Acknowledgement

We would like to thank AstraZeneca (Mölndal, Sweden), Hoffmann-La Roche (Basel, Switzerland), The Medicines Company (Leipzig, Germany) and Wilex AG (Munich, Germany) for providing the test compounds.

Declaration of interest

The authors report no conflicts of interests. The authors alone are responsible for the content and writing of the paper.