Arbutus is currently dosing patients in the last cohort of its Phase 1a/1b clinical trial to evaluate the safety and tolerability of AB-729 in patients with chronic Hepatitis B (cHBV) infection (AB-729-001 Trial). Data observed to-date show that AB-729 continues to reduce HBsAg across all doses and dosing intervals with a favorable safety and tolerability profile. Additionally, long term dosing of AB-729 has increased HBV-specific immune responses in some patients.

The Company intends to present updated and new on-treatment data on multiple cohorts of patients included in the AB-729-001 Trial, as well as long-term follow-up data for patients in the AB-729-001 Trial who completed treatment and have discontinued AB-729 and standard-of-care nucleos(t)ide analogues (NA) therapy at a medical conference this year. In-line with the Company's strategy to combine multiple therapies that target different points of the viral replication cycle to develop a curative treatment regimen for cHBV, Arbutus is currently enrolling patients in its Phase 2a randomized, open-label, proof-of-concept clinical trial designed to evaluate the safety and tolerability of AB-729 in combination with ongoing NA therapy and short courses of PEG-IFNa-2a in 40 patients with cHBV infection. The Company is expecting initial data from this clinical trial in the second half of 2022.

Also, in line with the Company's strategy, Arbutus has entered into separate clinical collaboration agreements with Assembly Biosciences Inc. (Assembly), Vaccitech plc (Vaccitech) and Antios Therapeutics Inc. (Antios) to evaluate AB-729 as the cornerstone agent in combination with Assembly's capsid inhibitor, Vaccitech's T-cell stimulating therapeutic vaccine, and Antios' Active Site Polymerase Inhibitor Nucleotide (ASPIN), respectively, in patients with cHBV infection. Enrollment is on-going in the Phase 2a proof-of-concept triple combination clinical trial evaluating AB-729, vebicorvir (VBR), Assembly's lead HBV core inhibitor (capsid inhibitor), and an NA. Assembly is conducting this clinical trial and expecting initial data in the second half of 2022.

Arbutus is on-track to initiate a triple combination Phase 2a clinical trial in the first half of 2022 to evaluate AB-729, combined with VTP-300, Vaccitech's therapeutic vaccine and an NA. Enrollment is complete in a cohort of patients in Antios' Phase 2a clinical trial evaluating AB-729, ATI-2173, Antios' ASPIN, and Viread (tenofovir disoproxil fumarate). With the majority of patients in this cohort enrolled in Ukraine, which is currently in a state of war, they may be lost to follow-up before completing the trial.

Therefore, Arbutus and Antios may report limited data on a reduced number of patients from this clinical trial.