Diarrhea is the most prevalent side effect of afatinib as an EGFR
tyrosine kinase inhibitor. The current study is to investigate the
potential protective mechanisms of crofelemer or loperamide in an animal
model of afatinib-induced diarrhea. Rats were randomized as the control,
afatinib (50 mg/kg), afatinib plus loperamide (50 mg/kg) or afatinib
plus crofelemer (50 mg/kg) group. Rats received drugs or saline through
oral gavage daily for consecutive 7 days. Diarrhea, weight, serum
biomarkers, gut histology or ultrastructure and multiomic changes were
analyzed daily or at day 8. Afatinib induced significant diarrhea,
weight loss, elevated serum levels of endotoxin, IL-6, IL-1β and TNF-α
in rats. Mucosal damage was most prominent in distal ileum, showing
edema, inflammatory infiltration, epithelial villus atrophy or fusion
and loss of tight junction. Both loperamide and crofelemer conferred
protection against afatinib-induced diarrhea and gut damage.
Transcriptomic enrichment analysis showed that PPAR and IL-17 signaling
pathway are among the top modified pathways in the ileum and colon of
the afatinib group, respectively. Metabolomic profiling identified 318
differently abundant metabolites when comparing the afatinib and the
control groups, with the most prominent enriched metabolic pathways
being metabolism of xenobiotics by cytochrome P450, retinol metabolism
and lysine degradation. Afatinib significantly decreased microbial
diversity, which is not fully restored by administration of crofelemer
or loperamide. Correlation analysis showed that cecal microbiota were
significantly correlated with metabolite profiles. Loperamide and
crofelemer attenuate afatinib-induced diarrhea and intestinal damage in
rats, possibly through regulating microbiota-metabolic axis.