Ribo Life Science Reports Sustained Viral and Antigen Suppression with Ozisiran in Phase IIa Trial for Chronic Hepatitis D

At the Delta Cure Meeting in Milan, Italy, researchers presented data that could reshape treatment for one of hepatitis's most challenging forms. The findings come from a clinical trial testing ozisiran, an investigational small interfering RNA (siRNA) drug, in patients with chronic hepatitis D virus (HDV)—a severe liver disease with limited treatment options.

Suzhou Ribo Life Science Co., Ltd. (06938.HK), a China-based biopharmaceutical company focused on siRNA therapies, announced preliminary interim results from its Phase IIa study of ozisiran (also known as RBD1016). The data, presented as an oral report at the conference, showed sustained suppression of both HDV RNA and hepatitis B surface antigen (HBsAg)—two key markers of the disease.

The trial enrolled 14 patients at Karolinska University Hospital and Danderyd Hospital in Stockholm, Sweden. The first 16 weeks used a randomized, single-blind, placebo-controlled design to evaluate ozisiran's efficacy when added to tenofovir alafenamide (TAF), a standard antiviral therapy. Researchers analyzed data through Week 36.

Persistent Viral Suppression

The results demonstrated clear suppression of HDV RNA and HBsAg at Week 24—12 weeks after the last dose. More importantly, this suppression continued through Week 36, which was 24 weeks after patients stopped receiving the drug. The durability of the effect suggests ozisiran may offer lasting benefits even after a relatively short treatment period.

"These results are encouraging, showing that ozisiran has a durable effect on two key virological markers of HDV—HBsAg and HDV RNA," said Dr. Anders Gabrielsen, Chief Medical Officer at Ribo Life Science. "The ability to observe sustained pharmacological activity after a relatively short dosing period underscores the potential of RNAi technology in addressing the significant unmet medical need in HDV."

Safety Profile

Ozisiran was generally well-tolerated, according to the trial data. HDV-related ALT flares—acute elevations of alanine aminotransferase, a liver enzyme—were rare and well-controlled. Other adverse events were mostly mild, and no serious adverse events were reported.

Targeting a Difficult Disease

HDV is a severe form of viral hepatitis that occurs only in people already infected with hepatitis B virus. The disease accelerates liver damage and increases the risk of cirrhosis and liver cancer. Current treatment options remain limited, making new therapies urgently needed.

Ozisiran works by targeting HBsAg, a protein essential for both hepatitis B and D virus infection. By reducing HBsAg production, the drug aims to achieve sustained viral control and improve clinical outcomes for HDV patients.

The study is registered on ClinicalTrials.gov under identifier NCT06649266.

About Ribo Life Science

Suzhou Ribo Life Science Co., Ltd. is a global innovative biopharmaceutical company focused on the research, development, and commercialization of siRNA therapies. The company has built a comprehensive small nucleic acid technology platform and developed a differentiated pipeline targeting cardiovascular metabolism, liver, kidney, and other major unmet medical needs. Ribo Life Science is committed to providing revolutionary nucleic acid drug treatments for patients worldwide.

Ribocure Pharmaceuticals AB, a subsidiary of Ribo Life Science, is dedicated to the global research and development of siRNA therapies, focusing on asset and pipeline development as well as the exploration of new targets. The subsidiary aims to build capabilities in clinical trials and siRNA drug development to address unmet medical needs around the world.