ECLIPSE 1 - A Phase 3 Randomized, Open-Label Study to Evaluate the Efficacy and Safety of Tobevibart+Elebsiran Combination Therapy in Participants with Chronic HDV Infection

Chronic (long-term) hepatitis D is a serious liver disease caused by the hepatitis delta virus (HDV). HDV can only infect people who already have hepatitis B virus (HBV). HDV can quickly lead to severe scarring of the liver (known as cirrhosis), liver failure, liver cancer, and even death. When the liver is damaged, liver enzyme levels in the blood can become higher than normal. The goal of treatment is to slow or reverse liver scarring, restore normal liver function, reduce the amount of HDV in the blood so low that it cannot be detected, and to make liver enzyme levels go back to normal. For people infected with both HBV and HDV, nucleos(t)ide reverse transcriptase inhibitors (NRTIs) may be used because they help keep HBV under control. However, NRTIs have demonstrated little to no efficacy against HDV. Tobevibart and elebsiran are 2 experimental drugs being studied (also known as study drug) that work in different ways to prevent HDV from multiplying and destroy virus already in the body. This ECLIPSE 1 trial will include adult participants with chronic HDV infection who are taking NRTI for HBV before starting the trial and who continue taking NRTI during the trial. This trial will study the effectiveness of tobevibart (300 mg) + elebsiran (200 mg) given every 4 weeks in treating HDV compared with waiting 12 weeks to start treatment with tobevibart+elebsiran (known as delayed treatment). Participants will also have either no cirrhosis or cirrhosis where the liver can still function properly despite scarring (known as compensated cirrhosis). Participants who immediately start treatment with tobevibart+elebsiran will be included in a group named Arm 1. Participants who delay treatment with tobevibart+elebsiran will be included in a group called Arm 2. All participants will receive up to 240 weeks of tobevibart+elebsiran.