GSK/Ionis Partnered Investigational Drug Shows Strong Results In Large Hepatitis B Studies

Ionis Pharmaceuticals Inc. (NASDAQ:IONS) partner GSK Plc (NYSE:GSK) on Wednesday shared data from two pivotal Phase 3 studies, B-Well 1 and B-Well 2, of bepirovirsen, an investigational antisense oligonucleotide for chronic hepatitis B (CHB). The studies included over 1,800 patients.

GSK licensed bepirovirsen from Ionis in 2019. The two companies have collaborated on its development.

Under the terms of the agreement, Ionis received an upfront payment, license fee, and development milestone payments, and is eligible to receive an additional $150 million in regulatory and sales milestone payments, as well as tiered royalties of 10-12% on net sales of bepirovirsen.

CHB affects over 250 million people worldwide and is the leading cause of liver cancer.

Data

The B-Well studies met their primary endpoint, and bepirovirsen demonstrated a statistically significant and clinically meaningful functional cure rate.

Functional cure rates were significantly higher with bepirovirsen plus standard of care compared with standard of care alone.

Results were statistically significant across all ranked endpoints, including in patients with baseline surface antigen (HBsAg) ≤1000 IU/ml, where an even greater effect was demonstrated.

The studies demonstrated an acceptable safety and tolerability profile consistent with what was reported in other studies.

Full results will be submitted for presentation at an upcoming scientific congress, published in a peer-reviewed journal, and used to support regulatory submissions to health authorities worldwide planned in the first quarter of 2026.

If approved, bepirovirsen has the potential to become the first finite, six-month therapeutic option for CHB and to serve as a backbone for future sequential treatment strategies.

Analyst Take

William Blair on Wednesday said that with five Phase 3 readouts for Ionis expected in 2026, the company is off to a good start here with bepirovirsen.

Analyst Myles Minter highlights that bepirovirsen is likely an underappreciated opportunity given Gilead Science Inc.'s (NASDAQ:GILD) Vemlidy is on track for $1 billion-plus in fiscal 2025 revenue and growing at 11% year-over-year.

William Blair reiterates the Outperform rating on Ionis and noted that full data is needed to better understand the bepirovirsen product profile.

In November 2025, Ionis Pharmaceuticals shared results from the pivotal Phase 3 CORE and CORE2 studies of olezarsen for severe hypertriglyceridemia (sHTG), a condition characterized by dangerously high triglyceride (fat) levels.

The studies met the primary endpoint, with olezarsen achieving a highly statistically significant placebo-adjusted mean reduction in fasting triglyceride (TG) levels of up to 72% at six months.

Price Action: Ionis Pharmaceuticals shares were up 4.06% at $84.80 and Gsk shares were up 1.20% at $51.16 at the time of publication on Wednesday, according to Benzinga Pro data.

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