Investigations of Enteric-Coated Propyl Gallate-induced Nephrotoxicity in Beagles and Human and Dog Renal Proximal Tubule Epithelial Cells

Permeability plays a major role in oral biotherapeutic delivery and permeation enhancers can improve the intestinal permeability of poorly absorbed active pharmaceutical ingredients such as peptides. As part of nonclinical development of an oral formulation for a glucagon-like peptide-1 (GLP-1) receptor agonist, MEDI7219, toxicology studies revealed that one of the formulation excipients, propyl gallate (PG), when administered in enteric-coated tablets, led to nephrotoxicity in beagles. While PG has been widely used in food and cosmetics as an anti-oxidant, understanding of its toxicology, metabolism and disposition has been rarely discussed. To elucidate the nephrotoxicity observed after administration of PG in an enteric coated tablet formulation, we employed dog and human renal proximal tubule epithelial cells (RPTEC). We observed greater cytotoxicity to PG in dog RPTEC compared to human cells. We also observed greater increases in response to PG treatment of glutathione in human cells compared to dog cells. Glutathione elevation is a common response to detoxify xenobiotics, especially ones that produce free radicals such as PG. Thus, we hypothesize that glutathione in human RPTECs was elevated to detoxify PG, but not in dog RPTECs, leading to greater cytotoxicity for dog RPTECs. Furthermore, to characterize disposition and metabolism of PG in both humans and dogs we developed a 10-plex, highly sensitive and robust LC-MS/MS-based quantification method of PG and its phase-I and phase-II metabolites in dog and human plasma. The methods were employed to support clinical study (NCT03362593) and preclinical dog studies to evaluate safety, pharmacokinetics and tolerability of PG to support its use in an oral formulation for MEDI7219.