AS001
Preclinical assessment of capsid assembly modulators (CAMs) of
varying potency revealed a novel class of picomolar-acting CAMs
inducing neither significant HBcAg cytoplasmic retention nor
adverse interactions with HBcAg-specific adaptive immunity
Romano Di Fabio1, Leda Bencheva1, Raffaele De Francesco2,3,
Lorena Donnici2, Vincenzo Summa4,5, Edith Monteagudo4,
Matteo Iannacone6,7, Luca Guidotti6,7. 1Promidis, Milan, Italy; 2National
Institute of Molecular Genetics “Romeo ed Enrica Invernizzi”, Virology,
Milan, Italy; 3University of Milan, Department of Pharmacological and
Biomolecular Sciences, Milano, Italy; 4IRBM Science Park S.p.A., Pomezia,
Italy; 5University of Naples Federico II, Napoli, Italy; 6San Raffaele
Hospital, Immunology & Infectious Diseases, Milano, Italy; 7Vita-Salute
San Raffaele University, Milano, Italy
Email: [email protected]
Background and Aims: Capsid assembly modulators (CAMs) that
induce the formation of empty/aberrant HBV capsids in the
hepatocyte are currently under development. Whether CAMs of
different potency in vitro varyingly alter the normal intracellulardistribution of the particulate and nonparticulate forms of the HBV
core protein (HBcAg) in vivo, and whether such supposed alteration
has toxic and/or immunoregulatory/immunopathological consequences
is ill defined. The aim of this study was to evaluate these
issues, exploiting immunocompetent transgenic mice that - being
immune tolerant to HBV - indefinitely replicate the virus at high
levels in the liver and display stable and lifelong viremia of ∼10^8
HBV genomes/ml.
Method: Three proprietary CAMs (termed M-1103, M-1407 and M-
1428) and a first-in-class CAM (termed NVR3-778) endowed with
diverse potency profiles in vitro were evaluated in HBV-replicating
transgenic mice (transferred or not with HBcAg-specific mouse naïve
or effector CD8 T cells) as per i) relative antiviral potency, ii) capsid/
core protein distribution, iii) direct or immune-mediated hepatocellular
toxicity and iv) immunoregulatory potential.
Results: EC50/EC90 evaluation in HepAD38 cells and HBV-infected
HepG2-NTCP cells indicated that M-1103 and M-1407 are ∼30 and
∼100-fold more potent in vitro than NVR3-778, respectively; potency
increased to ∼ 500 folds in the case of the picomolar-active M-1428.
Similar potency ratios over NVR3-778were observed in vivo, with M-
1428 quantitively eliminating HBV replicative intermediates from the
liver of transgenic mice after only 3 days of dosing at 50 mg/kg QD
(with commensurate reductions in serum HBV DNA, HBV RNA and
HBeAg). Time- and dose-dependent experiments revealed that none
of the tested CAMs caused direct liver injury. Surprisingly, however,
NVR3-778, M-1103 and M-1407 induced significant cytoplasmic
retention of HBcAg, whereas the more potent M-1428 and structurally
related analogues with increased potency did not. Of note, the
latter compounds did not sensitize hepatocytes to HBcAg-specific
effector CD8 T cell-mediated killing and did not interfere with a
recently described IL-2-based therapeutic strategy (Nature 574:200,
2019) capable of reverting T cell tolerance in this same animal model.
Conclusion: This study revealed that CAMs endowed with highly
diverse antiviral potency in vitro behave in vivo quite unpredictably
as per their intrinsic capacity to retain cytoplasmic HBcAg and,
secondarily, influence the interaction of CAM-exposed HBV-expressing
hepatocytes with adaptive immune responses. 作者: StephenW 时间: 2020-8-23 12:52