Abstract 1912: A Microbial Glucuronidase Target Implicated in Intestinal Reactivation of Tyrosine Kinase Inhibitors

Abstract Many drugs are inactivated by liver UGT enzymes and reactivated by enteric bacterial β-glucuronidases (GUS), an axis of drug metabolism that contributes to gut toxicities of anti-neoplastic agents, NSAIDs, and potentially other drug classes. For example, toxic reactivation of irinotecan by E. coli GUS is the causative event leading to intense, delayed diarrhea. Receptor tyrosine kinase (RTK)-targeted cancer drugs that undergo this UGT-GUS axis of metabolism are also associated with a high incidence of diarrhea. However, glucuronides of RTK inhibitors (RTKi) are not substrates of E. coli GUS. We recently reported that the human gut microbiome expresses nearly 300 distinct GUS enzymes (GUSome). The objective of this work is to identify the GUS enzyme(s) capable of metabolizing the glucuronide of the RTKi, sorafenib, that may contribute to sorafenib-induced diarrhea. We used UGT1A9 supersomes to make sorafenib-glucuronide (S-G) from commercially purchased sorafenib. S-G was screened against a library of 15 purified GUSome enzymes to identify the specific GUS orthologs that can cleave S-G, which was determined by monitoring sorafenib absorbance at 280 nm. Similar approaches were used to identify GUS enzymes that can cleave other RTKi's. Of the GUS enzymes evaluated for cleavage of S-G, only the GUS enzyme from an uncultured Eubacterium species was active. The structurally similar regorafenib-glucuronide and two glucuronides of other RTKi's (axitinib and imatinib) are also substrates of Eubacterium GUS. All four RTKi's are associated with diarrhea in at least 40-60% of patients. In contrast to E. coli GUS, very little is known about Eubacterium GUS. We have identified a set of RTKi-glucuronides as the first substrates of Eubacterium GUS, which may contribute to diarrhea associated with targeted anti-cancer drugs. Citation Format: Bret David Wallace, Jeffrey Hymes, Matthew Redinbo, Ward Peterson. A microbial glucuronidase target implicated in intestinal reactivation of tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1912.