Abstract 2096: Mechanistic insights into the pathogenesis of anti-DLL4-related hepatic sinusoidal dilatation
Authors: Jarzabek Monika A. , Desai Rupal , Zhu Yuda , de Zafra Christina Z. , Beyer Joe , Cain Gary , Raja Rajiv , Byrne Annette T. , Hegde Priti , Tarrant Jacqueline M. 
Published: July 2016

Abstract
Background: The Delta-like 4 (DLL4)-mediated NOTCH signaling pathway is an attractive therapeutic target in cancer. However, chronic blockade of DLL4 signalling has been observed to result in vascular toxicities, such as hepatic sinusoidal dilatation. As the underlying pathogenesis is unclear, the current study was undertaken to interrogate gene expression changes and potential safety biomarkers associated with anti-DLL4 related hepatic sinusoidal dilatation.
Methods: Formalin-fixed paraffin-embedded (FFPE) liver sections were derived from male and female cynomolgus monkeys administered FDLL8566 (recombinant humanized anti-DLL4 F(ab’)2 antibody) by intravenous injection once weekly for 8 weeks at dose levels of 0, 5, 15 and 50 mg/kg/week (n = 3/sex/group). RNA was extracted from whole liver sections and laser capture-microdissected (LCM) hepatic regions with or without sinusoidal dilatation. mRNA expression was quantified using a high-throughput RT-qPCR approach, with 96 pre-validated, species-specific TaqMan gene expression assays. A non-parametric statistical test was used to assess differential gene expression between sinusoidal dilatation-affected and non-affected liver tissues. The Benjamini-Hochberg multiple testing comparison error-based False-Discovery-Rate (FDR) method was applied to calculate the adjusted p-values for each probe set.
Results: Fourteen candidate genes were differentially expressed between sinusoidal dilatation-affected and non-affected cynomolgus monkey livers with an FDR adjusted p value &lt;0.05. The presence of sinusoidal dilatation could be discriminated based on hierarchical clustering and principal component analysis (PCA). Modulation of expression in genes associated with the VEGF/NOTCH pathway, vascular remodeling, and inflammation were related to anti-DLL4-induced sinusoidal dilatation.
Conclusions: This work highlights the involvement of the NOTCH pathway in the maintenance of hepatic sinusoidal homeostasis in the nonhuman primate (NHP). As preclinical toxicities in NHPs have translated to patients for other anti-DLL4 inhibitors, the changes in candidate genes and potential mechanism of toxicity identified in this study are likely to be relevant to humans. The phenotypic characteristics of hepatic sinusoidal dilatation associated with anti-DLL4 resemble the microscopic and molecular features observed in the liver following oxaliplatin treatment of patients (including involvement of angiogenesis), suggesting that similar molecular mechanisms of hepatic toxicity may exist between anti-DLL4 and oxaliplatin.
This work was supported by an EU funded Industry Academia Pathways and Partnerships Marie Curie Award (AngioTox) Grant Number 251528.
Citation Format: Monika A. Jarzabek, Rupal Desai, Yuda Zhu, Christina Z. de Zafra, Joe Beyer, Gary Cain, Rajiv Raja, Annette T. Byrne, Priti Hegde, Jacqueline M. Tarrant. Mechanistic insights into the pathogenesis of anti-DLL4-related hepatic sinusoidal dilatation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2096.