Characterizing Tebipenem Pivoxil Absorption and Metabolism with Enteroid Monolayers

Abstract

Tebipenem is a carbapenem antibiotic used to treat broad-spectrum bacterial infections. While tebipenem has very poor oral bioavailability, its prodrug form, tebipenem pivoxil, has fairly extensive and rapid oral absorption. It was hypothesized that tebipenem pivoxil uptake transport via organic anion transporting polypeptide 2B1 and organic anion transporting polypeptide 1A2 facilitated its absorption, with metabolism by carboxylesterases into tebipenem. However, the absorption and metabolism mechanism of tebipenem pivoxil has not been characterized with human physiologically relevant in vitro models. While enteroids are increasingly being used to investigate intestinal drug disposition, there is a lack of studies using differentiated enteroid monolayers to investigate prodrug absorption and metabolism, such as tebipenem pivoxil. This study used enteroids derived from pediatric donors, to investigate the intestinal permeation and metabolism of tebipenem pivoxil. The enteroid monolayers on Transwell inserts were dosed either apically or basolaterally with tebipenem pivoxil or tebipenem. Apical side, basolateral side, and cell lysate drug concentrations were determined using liquid chromatography-tandem mass spectrometry over a 2-hour period. In addition, organic anion transporting polypeptide 2B1, organic anion transporting polypeptide 1A2, or carboxylesterase 2 inhibitors were dosed with tebipenem pivoxil apically to assess potential mechanisms of tebipenem pivoxil permeation and metabolism. We observed that enteroid monolayers can distinguish the oral bioavailability differences between tebipenem pivoxil and tebipenem by assessing their permeation. In addition, the enteroid model was used to identify a significant impact on tebipenem pivoxil permeation/metabolism with carboxylesterase 2 inhibition or organic anion transporting polypeptide 2B1 / organic anion transporting polypeptide 1A2 inhibition. However, there were misalignments with in vivo data, such as the incredibly high tebipenem amount detected on apical side when dosing tebipenem pivoxil apically, and relatively low tebipenem permeated to the basolateral side. In addition, the impact of uptake transporter inhibition was not as large as expected, which warrants further studies. In conclusion, the enteroid monolayers can be used to study prodrug permeation and metabolism, but further studies are needed to confirm the abundance and localization of proteins involved in intestinal transport and metabolism.