Biotechnology: Hepatitis Delta (HDV): Rare Disease Market Poised For Meaningful Expansion

Research evidence excerpt

Biotechnology: Hepatitis Delta (HDV): Rare Disease Market Poised For Meaningful Expansion

FoundationM

VIR: Tobevibart + Elebsiran Presents Efficacious Monthly

Option

Vir Biotechnology is developing a differentiated combination regimen for chronic HDV

consisting of tobevibart, an engineered anti-HBsAg monoclonal antibody, and elebsiran, an

HBV-targeted siRNA designed to suppress hepatitis B surface antigen production. Because

HDV is dependent on HBV-derived HBsAg for viral assembly and propagation, Vir's

strategy focuses on achieving profound HBsAg suppression while simultaneously

preventing viral spread, with the goal of delivering durable HDV control through

complementary mechanisms.

Tobevibart targets a highly conserved region of HBsAg known as the antigenic loop, which

is required for viral attachment and entry into hepatocytes. Beyond direct viral

neutralization, the antibody has been engineered to enhance immune engagement,

promoting clearance of circulating HBV virions and subviral particles while potentially

stimulating antiviral immune responses through antibody-dependent cellular cytotoxicity

and enhanced antigen presentation. Elebsiran complements this approach by targeting a

highly conserved HBV sequence present across viral transcripts, thereby reducing

production of HBsAg and other HBV proteins from both covalently closed circular DNA

(cccDNA) and integrated HBV DNA ( Exhibit 4 ). Collectively, the combination is designed

to attack HDV biology at multiple levels by limiting viral spread, reducing the HBsAg

substrate required for replication, and potentially restoring antiviral immune function.

Exhibit 4: Tobevibart + Elebsiran Characteristics

Source: Vir Corporate Presentation

Clinical proof-of-concept has been established in the ongoing Ph2 SOLSTICE study