Combination therapy shows promise for hepatitis D in phase 2 trial

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A combination of tobevibart plus elebsiran significantly reduced hepatitis D virus (HDV) RNA levels and hepatitis B surface antigen (HBsAg) in patients with chronic hepatitis D, according to results from a phase 2 trial published in The New England Journal of Medicine.

"Tobevibart and elebsiran have complementary mechanisms of action. Tobevibart is a broadly neutralizing anti-HBsAg monoclonal antibody that neutralizes HBV and HDV and blocks viral entry into hepatocytes. Elebsiran is a small interfering RNA (siRNA) that targets HBV messenger RNA and reduces HBsAg production," noted Tarik Asselah, MD, and fellow investigators.

The randomized, open-label SOLSTICE trial assigned participants with chronic HDV infection to receive either tobevibart plus elebsiran every 4 weeks or tobevibart monotherapy. The primary endpoint was a combined response at week 24, defined as an HDV RNA level below the limit of detection or a decrease of at least 2 log10 IU per milliliter from baseline, along with normalization of ALT.
 
At week 24, a combined response was observed in 47% of participants (15 of 32) who received combination therapy and 70% of participants (23 of 33) who received monotherapy. Virologic response was achieved in 100% of patients receiving combination therapy (32 of 32) compared with 82% of those receiving monotherapy (27 of 33). ALT normalization occurred in 47% (15 of 32) and 76% (25 of 33), respectively.
 
By week 48, combined response rates were 56% (18 of 32) in the combination group and 61% (20 of 33) in the monotherapy group. Undetectable HDV RNA was reported in 66% of patients receiving combination therapy (21 of 32) compared with 48% receiving monotherapy (16 of 33), reported Dr. Asselah, of the Hôpital Beaujon, APHP, Clichy, France, and colleagues.
 
A key differentiator was the effect on HBsAg. At week 48, an HBsAg level below 10 IU per milliliter was achieved in 91% of participants (29 of 32) in the combination group compared with 21% (7 of 33) in the monotherapy group, suggesting deeper suppression of antigen production with the dual-agent approach.
 
Adverse events were common in both treatment groups. Through week 48, at least one adverse event occurred in 81% of participants receiving combination therapy and 94% of those receiving monotherapy. Reported events were primarily influenza-like illness and chills. ALT flares were also observed, particularly among participants initiating both agents simultaneously or receiving tobevibart alone.
 
"The ongoing phase 2 SOLSTICE trial is evaluating the efficacy and safety of tobevibart alone or combined with elebsiran for up to 192 weeks in participants with chronic HDV infection," noted study investigators.
 
In an accompanying editorial Daryl T. Y. Lau, MD, MPH, highlighted the importance of targeting HBV biology to treat HDV infection.
 
"The overall results of tobevibart plus elebsiran for chronic HDV infection are very encouraging; the combination received FDA Breakthrough Therapy designation and European Medicines Agency Priority Medicines designation for the treatment of chronic HDV infection," wrote Dr. Lau, of Harvard Medical School, Boston. "The crucial unanswered question is whether these favorable virologic responses would be sustained after the completion of therapy. Future studies are needed to further understand the host–viral interactions and immune mechanisms of these agents on the various HBV and HDV genotypes."
 
The trial was supported by Vir Biotechnology.

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