Combinatorial Treatment of Birinapant and Zosuquidar Enhances Effective Control of HBV Replication In Vivo.

Emma Morrish,Gregor Ebert,Liana Mackiewicz,Marc Pellegrini,John Silke,Gabriela Brumatti,Natasha Silke

doi:10.3390/v12080901

Abstract

Chronic hepatitis B virus (HBV) infection remains a global health threat and affects hundreds of millions worldwide. Small molecule compounds that mimic natural antagonists of inhibitor of apoptosis (IAP) proteins, known as Smac-mimetics (second mitochondria-derived activator of caspases-mimetics), can promote the death of HBV-replicating liver cells and promote clearance of infection in preclinical models of HBV infection. The Smac-mimetic birinapant is a substrate of the multidrug resistance protein 1 (MDR1) efflux pump, and therefore inhibitors of MDR1 increase intracellular concentration of birinapant in MDR1 expressing cells. Liver cells are known to express MDR1 and other drug pump proteins. In this study, we investigated whether combining the clinical drugs, birinapant and the MDR1 inhibitor zosuquidar, increases the efficacy of birinapant in killing HBV expressing liver cells. We showed that this combination treatment is well tolerated and, compared to birinapant single agent, was more efficient at inducing death of HBV-positive liver cells and improving HBV-DNA and HBV surface antigen (HBsAg) control kinetics in an immunocompetent mouse model of HBV infection. Thus, this study identifies a novel and safe combinatorial treatment strategy to potentiate substantial reduction of HBV replication using an IAP antagonist.

Highlights

Many pathogens, including hepatitis B virus (HBV), effectively manipulate tumor necrosis factor (TNF) receptor pathways and control molecular processes within host cells to evade antiviral immune responses and promote their propagation [1]
We have shown that HBV-expressing hepatocytes display high sensitivity to TNF signaling, with increased expression of both TNF and TNF receptor 1 (TNFR1), warranting the investigation of how the TNFR1 pathway can be therapeutically leveraged for the elimination of HBV infected cells [2]
We have shown that the combination treatment of birinapant with zosuquidar potentiates Smac-mimetic-mediated killing of hematopoietic malignancies [16]

Summary

Introduction

Many pathogens, including hepatitis B virus (HBV), effectively manipulate tumor necrosis factor (TNF) receptor pathways and control molecular processes within host cells to evade antiviral immune responses and promote their propagation [1]. We have shown that HBV-expressing hepatocytes display high sensitivity to TNF signaling, with increased expression of both TNF and TNF receptor 1 (TNFR1), warranting the investigation of how the TNFR1 pathway can be therapeutically leveraged for the elimination of HBV infected cells [2]. Cellular inhibitor of apoptosis (cIAP) proteins are major regulators of the extrinsic TNFR cell death pathway, orchestrating cell survival and cell death [3,4]. Natural IAP antagonists, such as the second mitochondria-derived activator of caspases (Smac/DIABLO), can sensitize cancers to cell death. This has led to the pharmaceutical development of small molecule peptide-mimetic IAP antagonists (Smac-mimetics) [5]. The observation that cIAPs limit TNF-mediated apoptosis and that

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Conclusion