FDA lifts clinical hold on Arbutus's AB-101
Key Facts
Arbutus Biopharma announced on October 22, 2026, that the U.S. Food and Drug Administration had lifted the clinical hold on the investigational new drug application for its oral drug AB-101. The decision removes the hold imposed on the U.S. application, a regulatory development concerning the company's chronic hepatitis B treatment program. Arbutus describes the drug as an oral inhibitor of the protein known as PD-L1, designed to act on the immune system in patients with the disease. Describing its therapeutic purpose, the company said it was designed to "reawaken and boost the immune system" in these patients. The announcement that the hold had been lifted follows the company's disclosure in its quarterly report for the period ended June 2026 that the drug's early-stage clinical trial had been completed.
Arbutus announced the original hold on April 25, 2023, according to its filing with the U.S. Securities and Exchange Commission. In its quarterly report at the time, it said the FDA's questions concerned "certain preclinical data and aspects of the clinical trial design." When the hold was imposed, the company had not dosed any patients with the drug, according to the same report. In July 2023, New Zealand's Medsafe approved the company's application to conduct a Phase 1 clinical trial of the drug in New Zealand, according to Arbutus's annual report. The New Zealand approval thus followed the announcement of the U.S. hold, as part of the program's clinical development path before the latest regulatory announcement.
The completed trial covered parts A and B of the drug's first phase of clinical development, according to the company's quarterly report. Arbutus had presented data on the drug's binding to its target receptors in its third-quarter 2025 results update. Those data showed maximum occupancy of the target protein's receptors ranging between 68% and 100%. That range was recorded at a daily dose of 30 mg, according to the company's update. In the portion of the study involving patients with chronic hepatitis B, Arbutus said there were "no drug-related serious adverse events and no evidence of liver dysfunction."
On virus-related results, Arbutus disclosed declines in surface antigen levels in two trial patients in its quarterly report filed with the Securities and Exchange Commission. One patient recorded a decline of 86.4%, while the other recorded a decline of 98.8%. The two percentages concern hepatitis B surface antigen, according to the company's description of the clinical results. These are preliminary results in these two patients and do not establish a functional cure for the chronic infection. The results form part of the trial of the drug, through which the company aims to reactivate the immune response in patients.
Financially, Arbutus held $92.6 million in cash, cash equivalents and marketable securities as of June 30, 2026, according to its second-quarter results announcement. Those balances were measured at the end of the financial period for which the company disclosed the completion of the early-stage clinical trial in its report. In a separate announcement of the final results of its share repurchase tender offer, Arbutus said it had accepted 46,000,000 shares for purchase. The company set the purchase price under the offer at $5.00 per share, according to the final results statement. With the announcement that the clinical hold had been lifted on October 22, 2026, Arbutus is assessing the next steps to advance the drug's development.