Arbutus Biopharma says FDA lifts AB‑101 clinical hold

United States clinical development can resume for an oral hepatitis B drug candidate after Arbutus Biopharma Corporation NASDAQABUS said on Thursday the FDA lifted the clinical hold on AB-101. The decision removes a restriction first disclosed in April 2023, but Arbutus has not committed to another trial.

In its Oct. 22 announcement, Arbutus said the FDA removed the hold on its investigational new drug application. The release did not describe the work required to resolve the hold, disclose the agency's correspondence or provide a new trial's design and start date.

Arbutus is a clinical-stage biotechnology company based in Pennsylvania with a pipeline focused on chronic hepatitis B.

Shares closed at US$4.18 on Nasdaq at 4:00 p.m. EDT on Oct. 21, before the announcement, according to the NASDAQABUS quote. The broader State Street SPDR S&P Biotech ETF NYSEARCAXBI quote showed US$152.78 as of 8:00 p.m. EDT on Oct. 21.

"Arbutus is evaluating next steps for the continued development of AB-101," the company said in the release.

Arbutus first announced the hold on April 25, 2023, after receiving verbal notification from the FDA. That announcement said initial single-dose trial data would no longer be reported in the second half of that year.

Early Trial Measured Safety

The ClinicalTrials.gov record, updated April 13, lists 128 actual participants across the completed Phase 1a/1b study. It compared AB-101 with placebo in healthy volunteers and patients with chronic hepatitis B, with the patient portion including background antiviral therapy.

The study's primary outcomes measured adverse events, laboratory abnormalities and changes in vital signs. Its listed sites were outside the United States, and the registry records completion on Feb. 9, 2026.

AB-101 is designed to inhibit the immune checkpoint protein PD-L1, potentially activating an immune response against hepatitis B. Arbutus described it as generally well tolerated in healthy participants and patients, without reporting adverse-event counts in Thursday's release.

The company reported high receptor occupancy in seven patients and surface-antigen declines in two patients at the 30 mg dose. The announcement supplied no magnitude of antigen reduction, placebo comparison, p value or confidence interval for those observations, and reported no functional-cure result.

Arbutus's Aug. 12 financial update reported US$92.6 million in cash, cash equivalents and marketable securities at June 30. It also disclosed receipt of US$178.4 million on July 8 as its share of a patent-litigation settlement.

The August update said Arbutus expected to return capital through repurchases of up to approximately US$230 million, subject to board approval. Thursday's announcement supplied neither an updated cash runway nor a budget for further AB-101 testing.

Hepatitis B Rivals Target Functional Cure

GSK plc LONGSK NYSEGSK announced FDA approval of Hibsago on Oct. 20 for eligible adults with chronic hepatitis B receiving antiviral therapy. Its approval announcement reported functional cure in 19 per cent of treated participants and none receiving placebo in pooled late-stage trials.

GSK defines functional cure as undetectable viral DNA and surface antigen for at least 24 weeks after all treatment stops. That sustained, off-treatment endpoint differs from the antigen declines described in Arbutus's early observations.

Read more: GSK wins FDA approval for Hibsago in chronic hepatitis B

Vir Biotechnology, Inc. NASDAQVIR is another viral-hepatitis developer. In its Jan. 12 update, Vir projected fourth-quarter topline results from its ECLIPSE 1 trial in chronic hepatitis delta, a different infection.

For AB-101, removal of the hold permits additional United States clinical development; it does not approve the drug for sale. Arbutus's next step remains a decision on continued development, with no trial-start or readout date disclosed on Oct. 22.