Nintedanib, which is used to treat idiopathic pulmonary fibrosis and non–small cell lung cancer, is metabolized to a pharmacologically inactive carboxylate derivative, BIBF1202, via hydrolysis and subsequently by glucuronidation to BIBF1202 acyl-glucuronide (BIBF1202-G). Since BIBF1202-G contains an ester bond, it can be hydrolytically cleaved to BIBF1202. In this study, we sought to characterize these metabolic reactions in the human liver and intestine. Nintedanib hydrolysis was detected in human liver microsomes (HLMs) (Clearance [CLint]: 102.8 ± 18.9 µL/min per mg protein) but not in small intestinal preparations. CES1 was suggested to be responsible for nintedanib hydrolysis according to experiments using recombinant hydrolases and hydrolase inhibitors as well as proteomic correlation analysis using 25 individual HLM. BIBF1202 glucuronidation in HLM (3.6 ± 0.3 µL/min per mg protein) was higher than that in human intestinal microsomes (1.5 ± 0.06 µL/min per mg protein). UGT1A1 and gastrointestinal UGT1A7, UGT1A8, and UGT1A10 were able to mediate BIBF1202 glucuronidation. The impact of UGT1A1 on glucuronidation was supported by the finding that liver microsomes from subjects homozygous for the UGT1A1*28 allele showed significantly lower activity than those from subjects carrying the wild-type UGT1A1 allele. Interestingly, BIBF1202-G was converted to BIBF1202 in HLS9 at 70-fold higher rates than the rates of BIBF1202 glucuronidation. An inhibition study and proteomic correlation analysis suggested that β-glucuronidase is responsible for hepatic BIBF1202-G deglucuronidation. In conclusion, the major metabolic reactions of nintedanib in the human liver and intestine were quantitatively and thoroughly elucidated. This information could be helpful to understand the inter- and intraindividual variability in the efficacy of nintedanib.

SIGNIFICANCE STATEMENT To our knowledge, this is the first study to characterize the enzymes responsible for each step of nintedanib metabolism in the human body. This study found that β-glucuronidase may contribute to BIBF1202-G deglucuronidation.