Huskey, Su-Er, Li, Hongmei, Catoire, Alexandre, Zhang, Jin, Jian, Zhigang, Flarakos, Jimmy and Mangold, James (2016) UTILIZATION OF STABLE ISOTOPE LABELING TO FACILITATE THE IDENTIFICATION OF VERY POLAR METABOLITES IN RAT URINE. Drug metabolism and disposition, 44 (1). pp. 1697-1708. ISSN 1521-009X

Abstract

Identification of polar metabolites of small molecule drug candidates in drug development is often challenging. Several major polar metabolites of [14C]compound Y (partial structure shown below) were detected in rat urine from the radiolabeled ADME study, but could not be characterized by LC-MS/MS. In such instances a strategy chosen by many investigators is to use a high specific activity radiolabeled version of the test compound, having the isotope ratio (i.e., [12C]:[14C]) serve as a mass filter. Unfortunately, [14C]compound Y was uniformly labeled, such that the [12C]:[14C] ratio was only ~0.1. This ratio was insufficient to be useful as a mass filter despite having a high specific activity (120 Ci/mg). Since a stable-label version of compound Y was already available for use as the internal standard of compound Y in GLP toxicokinetics studies, we decided to use it to enhance the isotope ratio as a mass filter. Accordingly an oral dose was designed, with a mixture of [13C6]compound Y, [12C]compound Y, and trace [14C]compound Y (specific activity 3.65 mCi/mg) such that the ratio of [12C] to [13C6] was ~0.9. In addition, a new separation method was developed to retain the polar metabolites longer on the HPLC column. Using this strategy, four polar metabolites (M1 to M4) were successfully identified and characterized in rat urine. Overall this alternative approach was shown to be practical and valuable for identification of polar metabolites by LC-MS/MS. The details of this approach are discussed in this presentation.

Item Type:	Article
Date Deposited:	22 Sep 2016 00:45
Last Modified:	22 Sep 2016 00:45
URI:	https://oak.novartis.com/id/eprint/21826