Neratinib reduces CytochromP450 3A enzymes in mouse intestine

Abstract

Neratinib (NERLYNX®) is a pan-HER tyrosine kinase inhibitor newly approved by FDA in 2017 and post to European market in 2018 to treat HER2-positive breast cancer, but the approval of neratinib has been controversial. Previous retrospective analysis showed that neratinib did not harm patients' quality of life, while another cost-benefit analysis indicated that neratinib's severe side effect comprises its cost-effectiveness. The phase III trial of neratinib showed that 96% of the patients taking neratinib experienced diarrhea. However, very few mechanistic studies have done to explore neratinib-induced gastrointestinal (GI) toxicity. Hereby, we performed toxicity studies in mice to characterize the potential mechanism underlying this adverse effect. C57BL/6 J (female, 5-weeks old) mice were randomly separated into three groups A, B, C. Group A received vehicle; group B was orally dosed with 100mg/kg neratinib once daily for 18 days. Group C was dosed with 100mg/kg neratinib for 12 days and switched to vehicle later for 6 days. Intestine and liver were collected for further analysis. Caco2, HT29 and Colo320DM cells were treated with neratinib in vitro. Our results showed that 12 days treatment of neratinib caused persistent histological damage in mouse GI tract, including blunted villi in small intestine and inflammatory infiltrate in colon. The gene expression of Cyp3a11, the major enzyme metabolizing neratinib in mice was significantly reduced in small intestine. The gene expression of proinflammatory cytokines, TNF-α, IL-6 and IL-1β, increased throughout the GI tract. Such damages were not recovered after 6 days without neratinib treatment. In addition, in vitro data showed that neratinib was potent in killing human intestine derived cell lines but did not reduce CYP3A4 expression in those cells. Based on such findings, we concluded that neratinib triggered inflammatory response in gut. And the release of cytokines downregulated intestinal CYP3A. With lower level of CYP3A, there is likely neratinib accumulation. It eventually leads to high risk of diarrhea. Our findings give new insight into the mechanism of neratinib-induced GI toxicity.