Dimethandrolone, a Potential Male Contraceptive Pill, is Primarily Metabolized by the Highly Polymorphic UDP-Glucuronosyltransferase 2B17 Enzyme in Human Intestine and Liver

Dimethandrolone undecanoate (DMAU), an oral investigational male hormonal contraceptive, is a prodrug that is rapidly converted to its active metabolite, dimethandrolone (DMA). Poor and variable oral bioavailability of DMA after DMAU dosing is a critical challenge to develop it as an oral drug. The objective of our study was to elucidate the mechanisms of variable pharmacokinetics of DMA. We first identified DMA metabolites formed in vitro and in vivo in human hepatocyte incubation and serum samples following oral DMAU administration in men, respectively. The metabolite identification study revealed two metabolites, DMA-glucuronide (DMA-G; major) and the androstenedione analog of DMA (minor), in the hepatocyte incubations. After oral DMAU administration, only DMA-G was detected in serum, which was >100-fold compared with DMA levels, supporting glucuronidation as the major elimination mechanism for DMA. Next, 13 clinically relevant UDP-glucuronosyltransferase (UGT) enzymes were tested for their involvement in DMA-G formation, which revealed a major role of UDP-glucuronosyltransferase 2B17 (UGT2B17) isoform with a smaller contribution of UGT1A9 in DMA-G formation. These data were confirmed by dramatically higher DMA glucuronidation rates (>200- and sevenfold) in the high versus the null UGT2B17-expressing human intestinal and liver microsomes, respectively. Since human UGT2B17 is a highly variable enzyme with a 20%-80% gene deletion frequency, the in vitro data suggest a major role of UGT2B17 polymorphism on the first-pass metabolism of DMA. Further, considering DMA is a selective and sensitive UGT2B17 substrate, it could be used as a clinical probe of UGT2B17 activity. SIGNIFICANCE STATEMENT: Dimethandrolone (DMA) is an active metabolite of dimethandrolone undecanoate (DMAU), an investigational male hormonal contraceptive. Previous studies have indicated poor and inconsistent bioavailability of DMAU following oral administration. This study found that UDP-glucuronosyltransferase 2B17-mediated high intestinal first-pass metabolism is the key mechanism of variable DMA bioavailability.