Arbutus Biopharma Corporation (Nasdaq: ABUS) announced on October 22, 2026, that the U.S. Food and Drug Administration has removed the clinical hold on the Investigational New Drug application for AB-101, allowing the company to conduct additional U.S. clinical development of the experimental hepatitis B treatment.
The decision removes a regulatory restriction that had remained in place for more than three years. However, Arbutus has not announced a new clinical trial or a timeline for restarting U.S. development. The company said it is evaluating the next steps for AB-101.
AB-101 is an oral small-molecule inhibitor of programmed death-ligand 1, or PD-L1. Arbutus designed the treatment to inhibit an immune checkpoint that can limit the ability of T cells to respond to chronic hepatitis B virus infection. The company believes an oral approach could provide more controlled checkpoint inhibition than antibody-based treatments, although that potential has not been established in a pivotal clinical trial.
Arbutus has completed a Phase 1a/1b study evaluating single and multiple doses of AB-101 in healthy volunteers and patients with chronic hepatitis B. According to the company, the candidate was generally well tolerated. Seven patients showed high PD-L1 receptor occupancy, while two patients receiving the 30-milligram dose experienced declines in hepatitis B surface antigen.
Those findings are preliminary and involve a small number of patients. Receptor occupancy shows that a drug is engaging its intended target, but it does not establish that the treatment produces a meaningful or lasting clinical benefit. Surface-antigen declines in two patients are also insufficient to determine efficacy.
In a May 2025 update, President and CEO Lindsay Androski said AB-101 had “achieved 100% receptor occupancy in 11 of 13 evaluable healthy volunteers” at the 40-milligram dose. The newly completed study included both healthy participants and patients with chronic hepatitis B, but Arbutus has not identified a dose or trial design for subsequent development.
The FDA initially placed the AB-101 application on hold in April 2023, before the company had started dosing U.S. participants. Arbutus later disclosed that the agency had raised questions about certain preclinical data and aspects of the proposed clinical-trial design. The company subsequently conducted the Phase 1 study under authorization from New Zealand’s medicines regulator.
Arbutus reported $92.6 million in cash, cash equivalents and marketable securities as of June 30, 2026, and a second-quarter net loss of $5.1 million. It used $14.1 million in operating activities during the first six months of the year.
Its financial position changed materially after the quarter. Arbutus received approximately $178.4 million from a Moderna patent-litigation settlement in July and subsequently spent $230 million repurchasing 46 million shares through a tender offer. Updated financial statements will provide a clearer picture of the company’s post-tender liquidity.
Upcoming Catalysts
- Arbutus’s decision on whether to continue developing AB-101
- Details of any new U.S. clinical trial or regulatory plan
- Additional analysis from the completed Phase 1a/1b study
- Updated financial results following the settlement and tender offer
- Further clinical progress involving the company’s separate imdusiran program
Sources
- Arbutus Announces FDA Clinical Hold Is Lifted for AB-101 — October 22, 2026
- Arbutus 2025 Annual Report and Form 10-K — March 23, 2026
- Arbutus Reports Second-Quarter 2026 Results — August 12, 2026
- Arbutus Announces Final Results of $230 Million Tender Offer — October 1, 2026
- Arbutus Reports First-Quarter 2025 Results and AB-101 Data — May 14, 2025
Editorial Disclosure
This article is based entirely on publicly available information, including company announcements, SEC filings and publicly available corporate materials. Securities discussed or referenced include Arbutus Biopharma Corporation (Nasdaq: ABUS). Biotech Stocks Daily has not received compensation from Arbutus Biopharma, its management, investor relations representatives or any third party for this specific article. Biotech Stocks Daily may have current or past paid business relationships with other companies, which do not influence the content or conclusions of this article. No staff member or principal of Biotech Stocks Daily holds a position in any security mentioned at the time of publication.
Sources used include Arbutus’s October 22, 2026 clinical-hold announcement, its 2025 annual report, its second-quarter 2026 results, its October 1 tender-offer announcement and its May 2025 clinical update. Information concerning AB-101’s mechanism, clinical findings and development potential originated primarily from Arbutus and has not been independently validated by Biotech Stocks Daily.
AB-101 remains investigational. Removal of the FDA clinical hold does not constitute approval or establish the candidate’s safety or efficacy. Arbutus has not announced a new U.S. trial, selected a future dose or committed to continuing the program. Clinical observations cited by the company involve small patient groups and may not be reproduced in larger controlled studies.
Financial information reflects disclosures made on the dates cited. The company’s June 30 cash position predates its receipt of settlement proceeds and its subsequent $230 million tender offer. Current liquidity may therefore differ materially from the reported quarter-end balance.
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