What are the indications, dosing regimen, monitoring requirements, and contraindications for Hibsago (bepirovirsen) in chronic hepatitis B?

Hebsago (Bepirovirsen) for Chronic Hepatitis B

Bepirovirsen is NOT currently FDA-approved for hepatitis B treatment and should NOT be used in routine clinical practice. The drug labels provided 1 are for an antiperspirant product (Certain Dri®), not for bepirovirsen/Hebsago, indicating a data error in the evidence provided.

Current Status and Evidence

Bepirovirsen is an investigational antisense oligonucleotide that has completed Phase 3 trials but lacks regulatory approval. The most recent high-quality evidence comes from two replicate Phase 3 trials (B-Well 1 and B-Well 2) published in 2026 2.

Phase 3 Trial Results (B-Well 1 and B-Well 2)

Efficacy:

• Functional cure rate at 72 weeks: 20% in B-Well 1 (127/650 patients) and 19% in B-Well 2 (106/570 patients) versus 0% with placebo 2
• Functional cure was defined as sustained HBV DNA below the lower limit of quantification AND HBsAg loss for at least 24 weeks after treatment discontinuation
• All patients were on stable nucleoside/nucleotide analogue (NA) therapy with HBsAg levels 100-3,000 IU/mL

Study Design:

• Subcutaneous bepirovirsen 300 mg weekly for 24 weeks
• Patients discontinued NA therapy at week 48
• Noncirrhotic patients only

Safety Profile:

• Adverse events: 91% with bepirovirsen vs. 73% with placebo 2
• Serious adverse events: 7% vs. 4%
• Grade 3+ adverse events during treatment: 16% vs. 3%
• Most common Grade 3 event: ALT elevation (6% of patients)
• Injection site reactions, pyrexia, and fatigue were common 3

Mechanism of Action

Bepirovirsen targets all HBV messenger RNAs through antisense oligonucleotide technology, resulting in:

• Reduction of viral protein production
• Decreased HBV DNA levels
• Immune system modulation that may facilitate killing of infected hepatocytes 4
• Induction of innate immune proteins independent of HBV presence 5

Why This Drug Is NOT Ready for Clinical Use

Critical Limitations:

1. No regulatory approval: Despite Phase 3 completion, bepirovirsen has not received FDA or EMA approval
2. Modest efficacy: Only 19-20% functional cure rate, meaning 80% of patients do not achieve sustained response
3. Significant ALT flares: The 6% rate of Grade 3 ALT elevations raises concerns about hepatocyte injury, particularly in patients with advanced fibrosis
4. Limited patient population studied: Excluded cirrhotic patients, limiting generalizability
5. Relapse concerns: Phase 2b data showed substantial relapse rates after treatment discontinuation 3

Current Standard of Care (Per EASL 2025 Guidelines)

For chronic hepatitis B, the established first-line treatments remain:

• Entecavir 0.5 mg daily (oral)
• Tenofovir disoproxil fumarate 245 mg daily (oral)
• Tenofovir alafenamide (oral)
• Pegylated interferon-alfa (in selected patients) 6, 7

Treatment indications per EASL 2025 7:

• HBV DNA >2,000 IU/mL with elevated ALT (>ULN) and/or significant fibrosis
• Any detectable HBV DNA in cirrhotic patients regardless of ALT
• Advanced fibrosis (>F3 or LSM >8 kPa) with detectable HBV DNA

Sequential Therapy Considerations

The B-Together study 8 explored sequential bepirovirsen followed by pegylated interferon-α-2a, showing:

• Reduced relapse rates compared to bepirovirsen alone
• Response rates of 9-15% with sequential therapy
• All responders had baseline HBsAg ≤3,000 IU/mL
• This remains investigational and not approved for clinical use

Clinical Recommendation

Do not prescribe bepirovirsen/Hebsago for chronic hepatitis B. Continue using established nucleos(t)ide analogues (entecavir, tenofovir) as first-line therapy per EASL 2025 guidelines 7. These agents have:

• Decades of safety data
• High genetic barrier to resistance
• Proven reduction in cirrhosis progression and HCC development
• Oral administration with excellent tolerability

For patients seeking functional cure: Counsel that current approved therapies require long-term administration but effectively suppress viral replication and prevent disease progression. Experimental therapies like bepirovirsen may become available in the future pending regulatory approval, but are not currently an option outside of clinical trials.

Common pitfall: Patients may hear about "new hepatitis B cures" in the media. Clarify that while bepirovirsen shows promise in achieving HBsAg loss in a subset of patients, it remains investigational with significant limitations and no regulatory approval for clinical use.