Oligonucleotides remain compounds of high interest in drug development, especially with recent advancements in chemistry and delivery technologies. With more compounds progressing further in preclinical development, the need for physiologically relevant preclinical animal models is of utmost importance but still remains a challenge.
Following expanded use of chimeric mice with humanized liver technology, we are highlighting some of the papers published by industrial researchers working in the oligonucleotide therapeutics field, where the PhoenixBio technology was used to advance the research in this important area.
PXB-cells® (fresh human hepatocytes isolated from PXB-mice) have been used by F. Hoffmann-La Roche AG researchers  to validate the target of their anti-HBV lead in development. The results were published in “Hepatology” – the Journal of the American Association for the Study of Liver Diseases. HBV-infected PXB-cells® were treated with the Roche proprietary compound RG7834 or with PAPD5 LNA SSO and PAPD7 LNA SSO (locked nucleic acid single-stranded oligonucleotides targeting knockdown of PAPD5 and PAPD7, respectively). Both PAPD5 and PAPD7 knockdown (P5+P7 KD on the image) and RG7834 treatment led to destabilization and degradation of HBV mRNA without impacting the production of viral RNA transcripts (see Figure 1).
Lipid nanoparticle (LNP) transfection efficiency in the PXB-mouse® has been shown by Arbutus Biopharma Corporation  and Moderna, Inc. . Arbutus Biopharma  utilized the PXB-mouse® with Hepatitis B/ Hepatitis Delta (HBV/HDV) dual chronic infection model to evaluate the anti-HBV and anti-HDV effects of an LNP-encapsulated HBV-targeting siRNA. One compound (an siRNA agent designed to cleave HBV RNAs) reduced both HBV and HDV viremia, while anti-HDV siRNA only inhibited HDV, and PEG-IFN-alpha only inhibited HBV. Moderna, Inc.  showed the utility of the PXB-mouse® to predict human miRNA-mediated protein knock down which was recapitulated in non-human primates. LNP-encapsulated mRNAs were administered into PXB-mice to test if miRts (microRNA target sites)-mediated suppression is likely to work in humans. miR122 target site (122ts) mRNAs were tested in PXB-mice and miRts-mediated knockdown of protein expression was observed with both reporters used.
A nice example of GalNAc-conjugated siRNA-mediated mRNA knock down in PXB-mouse® livers is shown in Dicerna Pharmaceuticals, Inc. publication .
To confirm the efficiency of LDHA (gene encoding lactate dehydrogenase A (LDHA) in liver) knockdown, it was confirmed that human specific LDHA siRNA achieved specific inhibition of human LDHA mRNA in the PXB-mouse®. Human-specific LDHA siRNA displayed expected target delivery and gene suppression in human hepatocytes in PXB-mice.
The utility of both PhoenixBio products (PXB-mouse® and PXB-cells®) was shown by Benitec Biopharma Ltd.  and Arcturus Therapeutics . Efficacy of shRNA and AAV transduction efficiency in both PXB-cells® and chimeric mice with humanized liver was shown by Benitec Biopharma  using their anti-HBV compound in development. In addition to in vivo and in vitro efficacy, Arcturus Therapeutics  also showed a favorable tolerability profile with their proprietary lipid-enabled unlocked nucleic acid RNA (LUNAR) delivery platform.
These publications show the growing utility of chimeric mouse with humanized liver technology in evaluating efficacy, delivery, off-target effects, safety, pharmacokinetics (PK) and ADME (adsorption, distribution, metabolism and excretion) profiles of oligonucleotides in development. Stay tuned for further updates on our products use in this exciting field.
 Esau, C. et al. “LUNAR (TM)-HBV, a UNA Oligomer Combination for the Treatment of Chronic Hepatitis B Virus Infection.” Poster presented at: AASLD The Liver Meeting; November 2016; Boston, MA
 Mao, T. et al. “BB-HB‐331, a DNA-Directed RNA Interference Agent, Suppresses Hepatitis B virus (HBV) in vitro and in vivo.” Poster presented at: ESGCT 2016; October 2016; Florence