Bepirovirsen, an antisense oligonucleotide developed by Ionis in partnership with GSK, met its primary endpoint in two global Phase 3 studies, B‑Well 1 and B‑Well 2. The trials, which enrolled more than 1,800 patients across 29 countries, demonstrated a statistically significant and clinically meaningful functional cure rate—defined as sustained loss of hepatitis B surface antigen and undetectable viral DNA for at least 24 weeks—when the drug was combined with standard of care. Functional cure rates were markedly higher than with standard therapy alone, with the greatest benefit observed in patients whose baseline surface antigen levels were ≤1,000 IU/mL.
The achievement of a functional cure represents a finite six‑month treatment that could replace lifelong nucleoside‑analogue therapy. By providing a curative option, bepirovirsen addresses a critical unmet need in a disease that affects more than 250 million people worldwide and accounts for roughly 56 % of liver‑cancer cases. The data support Ionis’s strategy to bring RNA‑targeted medicines to market and align with its transition to a fully integrated commercial company.
Safety data from the trials indicated an acceptable profile. No serious adverse events were reported, and the most common events were mild injection‑site reactions, consistent with the drug’s mechanism of action. The tolerability profile supports the feasibility of a short‑course, patient‑friendly regimen.
Ionis and GSK’s collaboration agreement could yield up to $150 million in milestone payments and 10–12 % royalties on net sales. The partnership also grants access to GSK’s global commercial network, accelerating potential market entry. Ionis’s bepirovirsen has received Fast Track designation from the U.S. FDA, Breakthrough Therapy status in China, and SENKU designation in Japan, streamlining regulatory pathways in key markets.
Following the announcement, analysts at RBC Capital and TD Cowen raised their price targets and reiterated buy ratings, reflecting confidence in the drug’s commercial potential. Ionis’s CEO Brett P. Monia emphasized that the results bring hope to millions of people living with chronic hepatitis B, while GSK’s Chief Scientific Officer Tony Wood highlighted the potential to transform treatment goals for the disease.
Ionis plans to submit the data to regulatory authorities in the first quarter of 2026 and intends to publish the full study findings in a peer‑reviewed journal. The positive Phase 3 results position bepirovirsen as a first‑in‑class finite therapy that could capture a substantial share of the global chronic hepatitis B market, estimated at over 250 million patients and a significant portion of liver‑cancer cases.
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