Abstract 1453: Antibiotic treatment targeting gram negative bacteria prevents neratinib-induced diarrhea in rats
Authors: Secombe Kate R. , Ball Imogen A. , Wignall Anthony D. , Bateman Emma , Diala Irmina , Lalani Alshad S. , Bowen Joanne M. 
Published: July 2021

Abstract
Introduction
Neratinib is an irreversible pan-HER tyrosine kinase inhibitor used for treatment of HER2+ breast cancer. Diarrhea is a common toxicity observed with this class of agents. We have previously shown that neratinib-induced diarrhea is associated with alterations to the gut microbiome in a rat model [Secombe et al. 2020]. This study aimed to evaluate contribution of specific gut microbiota in the development of neratinib-induced diarrhea using different classes of oral antibiotics.
Methods
Female Albino Wistar rats (n=44) were treated daily with 50 mg/kg neratinib or vehicle control (0.5% hydroxypropyl methylcellulose) for 28 days by oral gavage. Antibiotics (vancomycin (0.5g/L), neomycin (1g/L) or an antibiotic cocktail (vancomycin 0.5g/L, neomycin 1g/L and ampicillin 1g/L)) were administered via drinking water throughout the study, beginning four weeks prior to neratinib. Diarrhea was scored from 0-3. In the vehicle control, neratinib alone and neomycin treated groups, fecal contents were collected at necropsy and subject to 16S bacterial DNA sequencing and bioinformatic analysis was performed to characterize the microbiome.
Results
Conclusions
Neratinib treatment was associated with an increase in Gram negative Proteobacteria, and neomycin targeting Gram negative bacteria was most effective at reducing neratinib-induced diarrhea. These studies suggest that modulating the microbiome may be a novel strategy for mitigating or prevention of tyrosine kinase inhibitor-induced diarrhea. Given that increases in Blautia were associated with ablation of diarrhea, this is now a sensible further target for future intervention studies.
VariableVehicle Control(n=8)Neratinib(n=10)Neratinib + antibiotic cocktail (n=8)Neratinib + vancomycin (n=8)Neratinib + neomycin(n=10)Incidence of diarrhea, %Grade 010014.112.192.295.2Grade 1026.278.46.94.8Grade 2047.67.80.80Grade 3012.1000Mean±SEM days with grade 2 diarrhea0±0*13.8±1.592.25±0.620.25±0.16*0±0*Median (range) tissue injury scoreProximal ileum0.5 (0-2)2 (1-4)**1.5 (0-4)1.5 (0-4)2 (1-4)Distal ileum1 (0-2)3 (1-4)**3 (0-4)3 (2-4)**3 (2-4)**Proximal colon1 (0-2)2 (0-3)1.5 (1-3)1.5 (0-2)1 (0-2)Distal colon1 (0-2)3 (1-4)2 (1-3)2 (1-3)2 (1-3)Microbial analysisShannon's Index (mean±SEM)2.42±0.17#2.39±0.15#--1.30±0.11Relative genus abundanceProteobacteria0.0076±0.0010.045±0.01#0.0045±0.001Blautia0.042±0.01#0.016±0.005#--0.70±0.04Allobaculum0.0045±0.0020.17±0.04**--0.074±0.03SEM, standard error of the mean, PCoA, Principal Coordinate Analysis*P&lt;0.005 vs neratinib, **P&lt;0.05 vs control, #P&lt;0.005 vs neratinib +neomycin
Citation Format: Kate R. Secombe, Imogen A. Ball, Anthony D. Wignall, Emma Bateman, Irmina Diala, Alshad S. Lalani, Joanne M. Bowen. Antibiotic treatment targeting gram negative bacteria prevents neratinib-induced diarrhea in rats [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1453.