RESUMEN
11ß-Methyl-19-nortestosterone dodecylcarbonate (11ß-MNTDC) is a prodrug of 11ß-MNT and is being considered as a promising male oral contraceptive candidate in clinical development. However, the oral administration of 11ß-MNTDC exhibits an ~200-fold lower serum concentration of 11ß-MNT compared to 11ß-MNTDC, resulting in the poor bioavailability of 11ß-MNT. To elucidate the role of the first-pass metabolism of 11ß-MNT in its poor bioavailability, we determined the biotransformation products of 11ß-MNT and its prodrugs in human in vitro models. 11ß-MNT and its two prodrugs 11ß-MNTDC and 11ß-MNT undecanoate (11ß-MNTU) were incubated in cryopreserved human hepatocytes (HHs) and subjected to liquid chromatography-high resolution tandem mass spectrometry analysis, which identified ten 11ß-MNT biotransformation products with dehydrogenated and glucuronidation (11ß-MNTG) metabolites being the major metabolites. However, 11ß-MNTG formation is highly variable and prevalent in human intestinal S9 fractions. A reaction phenotyping study of 11ß-MNT using thirteen recombinant UDP-glucuronosyltransferase (UGT) enzymes confirmed the major role of UGT2B17 in 11ß-MNTG formation. This was further supported by a strong correlation (R2 > 0.78) between 11ß-MNTG and UGT2B17 abundance in human intestinal microsomes, human liver microsomes, and HH systems. These results suggest that 11ß-MNT and its prodrugs are rapidly metabolized to 11ß-MNTG by the highly polymorphic intestinal UGT2B17, which may explain the poor and variable bioavailability of the drug.
RESUMEN
Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) has become a mainstay analytical technique in pharmaceutical research and development and clinical diagnosis due to several advantages including excellent selectivity, specificity, and high sensitivity. LC-MS/MS has become the method of choice for steroids analysis due to its fast analytical time and improved specificity yet has a challenge in the separation and measurement of isomers with the same product ions. Here we describe a high-sensitivity LC/LC-MS/MS method that combines chiral chromatography and reverse-phase chromatography (LC/LC) along with MS/MS to rapidly separate and quantify steroid isomers of 11ß-methyl-19-nortestosterone (11ß-MNT) and endogenous testosterone in serum.