William Symonds
Analyst · William Blair
I think we may have lost Mike so perhaps I'll step in until Mike dials back in. This is Bill Symonds, Chief Development Officer. So, our product pipeline is centered on our strategy to cure chronic hepatitis B virus infections and employing a combination of therapeutic agents with complementary mechanisms of action. We are conducting preclinical combination studies to evaluate combinations of our proprietary candidates with HBV standard of care therapies and with other Arbutus owned assets. Our team recently presented two preclinical studies supporting our drug combination approach at the 53rd annual International Liver Congress or EASL as Mark described earlier which provided further validation of our combination strategy and endorsed the breadth and quality of our preclinical candidates. Our next-generation capsid inhibitor, AB-506 and a novel HBV RNA destabilizer, AB-452 were studied in combination with our leading LNP enabled RNAi agent, ARB-1467, and approved HBV therapies nucleotide analogs, Entecavir, tenofovir disoproxil fumarate and tenofovir alafenamide. In these studies, when AB-506 and AB-452 were combined, they exhibited distinct and complementary antiviral activities. The in vitro dual combinations of AB-506 or AB-452 with approved nucleoside analogs and nucleotide analogs or with ARB-1467 ranged from additive to moderately synergistic at reducing HBV RC-DNA and HBS antigen levels. After a once-daily-7-day oral treatment period in HDI HBV mice, dual combinations of AB-506 plus AB-452, AB-506 plus tenofovir and AB-452 plus tenofovir, demonstrated a strong antiviral activity with mean 1.4, 1.9 and 2.2 log reductions in serum HBV DNA versus control respectively, whereas the triple combination of AB-506, AB-452 and a nuc resulted in greater serum HBV DNA reductions, 2.8 log versus the vehicle control. All AB-506 and AB-452 treated groups demonstrated more robust reductions in liver HBV DNA compared to tenofovir alone. Serum Hepatitis B surface antigen reduction was detected in AB-452 treated groups and when combined with AB-506 and/or tenofavir, there was no adverse effect on the ability of AB-452 to reduce hepatitis B surface antigens. These studies suggest that when combined, these agents have distinct but mechanistically compatible antiviral activities and thus may [synctively] be used in future combination therapeutic regimens. We expect to file an IND or CTA for both of these molecules in mid-2018 to enable a Phase I study of healthy volunteers in the second half of the 2018. Expanding on our commitment to hepatitis B surface antigen reduction, we have developed an N-Acetylgalactosamine or GalNAc enabled RNAi conjugate technology that we are applying to hepatitis B virus and recently nominated a promising new RNAi candidate, AB-729, that is targeted to hepatitis using our novel covalently conjugated GalNAc-delivery technology. This Arbutus proprietary technology enables subcutaneous administration of an RNAi therapeutic. AB-729 is a single triggered RNAi agent that targets the multiple HBV transcripts, enabling an inhibition of viral replication and suppression of hepatitis B surface antigen and all other hepatitis B viruses antigens. AB-729 showed more durable in vivo preclinical activity than earlier generation RNAi agents for the treatment of chronic HBV infections supporting infrequent dosing regimens. One dose of AB-729 was sufficient to achieve mean maximum hepatitis B surface antigen reductions of 1.4, 2.8 and 3.9 log10 at either at 1, 3 or 9 mg/kg respectively and AAV-HBV mouse model. In vivo AB-729 suppression of hepatitis B surface antigen was highly durable with 83%, 89% and 99% respectively of the mean maximal effect remaining at week 10 after a single dose. This GalNAc HBV agent has the potential to complement our small molecule agents with a convenient subcu dose administration. These results support the design and execution of clinical combination studies in patients with chronic hepatitis B virus infections to improve upon the current standard of care. In totality, our next generation capsid inhibitor, novel HBV RNA destabilizer and GalNAc enabled RNAi, have demonstrated strong feasibility for inclusion in a drug combination regiment with approved therapies in other Arbutus agents supporting our goal of delivering a curative HBV therapeutic combination regimen. We anticipate completing IND or CTA enabling studies for AB-506 and AB-452 by the middle of this year and to plan to file an IND or CTA on AB-729 in the first half of 2019. Now moving onto the clinical study with ARB-1467. We have initiated a phase II triple combination study with ARB-1467, tenofovir and pegylated interferon. As a reminder, the LNP enabled ARB-1467 facilitates potent knock down of all viral messenger RNA or mRNA transcripts and viral antigens across a broad range of HBV genotypes and reduces the risk of developing antiviral resistance. ARV-1467 simultaneously targets 3 sites on the HBV genome, including the hepatitis B surface antigen coding region which increases the likelihood of affecting the HBV infection. Reducing hepatitis B surface antigen is thought to be a key prerequisite to enable a patient's immune system, to raise an adequate immune response against the virus. In order to evaluate the role of the immune system in patients with reduced hepatitis B surface antigen levels, patients in this study who meet predetermined criteria with ARB-1467 treatment, will qualify for the addition of weekly pegylated interferon treatments. Patients who do not reach the predefined response criteria by week 6 will discontinue all medications. The study will conclude with a 24-week post treatment follow-up period to evaluate the treatment response. Partial or interim on-treatment results from this study are expected in the second half of 2018, followed by complete results in 2019. Results from this study will help inform the design of future combination studies with the small molecule agents l I described earlier. I would now like to turn the call over to Koert.