Recent advances in metabolism and toxicity of tyrosine kinase inhibitors.

Small molecule tyrosine kinase inhibitors (TKIs) are widely used as anticancer drugs approved by U.S. FDA. However, the toxicities of TKIs to multiple organs have greatly limited their clinical applications. The metabolism of TKIs generates several potentially toxic metabolites in vivo, that can disturb the endogenous metabolism as well as cellular function, leading to organ damage. Therefore, it is essential to identify the toxic metabolites and elucidate the underlying mechanism of TKI-induced toxicity. Metabolomics is a powerful tool for the identification of the xenobiotic metabolites and metabolic derangement associated with xenobiotic exposure, that is helpful to understand the toxicity of TKIs. The study using metabolomics approach has revealed that the reactive metabolites/intermediates (e.g., N-oxide metabolite, primary amine metabolite, 1,4-benzoquinone intermediate) and adducts with glutathione, cysteine and mercapturic acid can be derived from TKIs. Fourteen metabolic pathways could be affected following the TKI treatment, including lipid metabolism, bile acid metabolism, and gut microbiota-related pathway. Modulation of xenobiotic receptor signaling, inhibition of xenobiotic metabolism, and supplementation of endogenous metabolites are potential strategies to protect against TKI-induced toxicity. In this review, studies on the metabolism of TKIs and the alterations of endogenous metabolism are discussed, and the potential preventions against TKI-induced toxicity are summarized.