Arbutus ends COVID-19, RNA destabilizer programs after glimpsing preclinical data

Arbutus Biopharma has become the latest biotech to exit the COVID-19 space as well as discontinuing its work on RNA destabilizers, tightening its focus on hepatitis B.

The company’s pipeline had included AB-343, an oral coronavirus therapy designed to inhibit the SARS-CoV-2 main protease. Arbutus has also been working on a combination therapy that combined AB-343 with a potential nsp12 polymerase inhibitor, but an “unfavorable” pharmacokinetic profile in preclinical studies led the biotech to give up on its coronavirus efforts altogether.

A similar story has played out for Arbutus’ RNA destabilizer, AB-161, which the company also announced yesterday is being halted over “a pre-clinical toxicology finding not related to peripheral neuropathy.” AB-161 had already entered a phase 1 trial for hepatitis B virus, and the company stressed that no safety issues had been reported in the healthy participants of this study.

The company expects the pipeline culls will extend its cash runway into the third quarter of 2025. Arbutus has a number of key readouts lined up before then, including preliminary data from a phase 2a trial of the RNAi therapeutic imdusiran in combination with Vaccitech’s antigen-specific immunotherapy VTP-300 in patients with chronic hepatitis B virus. Those initial data are expected in the fourth quarter of this year.

Next up will be preliminary data from a phase 1 trial of oral PD-L1 inhibitor AB-101. While the drug was slapped with a clinical hold by the FDA in April, Arbutus has received the green light to proceed in New Zealand, where it expects to report data in the first half of next year.

CEO William Collier described AB-101 as “highly potent” and said it had already “demonstrated activity against PD-L1 in cells from chronic HBV subjects.”

“We … continue to believe that checkpoint inhibitors may play a role in antiviral immune tolerance in cHBV,” Collier added in yesterday’s release.

An FDA hold isn’t the only bump in the road for Arbutus. The company has ongoing lawsuits against Moderna and Pfizer-BioNTech alleging patent infringement of its lipid nanoparticle delivery system. “Document production is currently ongoing in the lawsuit against Moderna with the claim construction hearing scheduled for February 7, 2024,” the biotech said.

Dropping its coronavirus and RNA destabilizer programs are only the latest pipeline culls for Arbutus. The company scrapped a phase 1 med in 2019 after two healthy participants fell ill with acute hepatitis, followed less than six months later by axing a preclinical hepatitis B candidate after safety concerns arose in animal studies. In November 2022, the biotech also dropped an oral capsid inhibitor.