A Marriage of Convenience

The development of peptides as new pharmaceutical drugs for the treatment of disease in various therapeutic areas (anti-infection or central nervous system (CNS), for example) led to the issue of detecting and quantifying these molecules in biological media in order to assess drug exposure, the pharmacokinetic properties and dosage regimen of these new drugs. The use of enzyme-based assays was, until recently, the only way to evaluate these characteristics. Issues with the specificity and reliability of such enzyme assays have led to the development of physico-chemicalbased methods. With the emergence of new mass spectrometry equipment and, in particular, liquid chromatography with tandem mass spectrometric detection (LC/MS-MS), it is now possible to measure the levels of peptides in biological matrices with the level of precision and accuracy that is generally required by regulatory agencies. This article investigates two examples of analytical methods that are presently being used in laboratories for assaying two peptides in preclinical and clinical development. At the present time, we are not able to disclose any information on the structure of these peptides. We have, therefore, named the test peptides PEPT-I and PEPT-II. PEPT-I is being developed for application in infectious disease, while PEPT-II is under development for an application in CNS disease.

MATERIALS AND METHOD

All reagents and solvents used in the described analyses (HPLC-water, acetonitrile, methanol, trifluoroacetic acid and trichloroacetic acid) were analytical grade. A Waters Quattro PremierTM XE MS-MS, from Micromass Waters, fitted with an UPLC/AcquityTM system was used for the LC/MS-MS analyses equipped with a UPLC 50x2.1 mm x 1.7μm BEH C18 reverse-phase Waters Acquity LC column.