The Phase 3 LIMT-2 study will evaluate the safety and efficacy of Peginterferon Lambda treatment for 48 weeks with 24 weeks follow-up compared to no treatment for 12 weeks in patients chronically infected with HDV. The primary analysis will compare the proportion of patients with HDV RNA < LLOQ at the 24-week post-treatment visit in the Peginterferon Lambda treatment group vs the proportion of patients with HDV RNA < LLOQ at the Week 12 visit in the no-treatment comparator group.

This is a randomized, open-label, parallel arm study that will allocate patients (2:1) with chronic HDV infection to one of two treatment groups: Peginterferon Lambda 180 mcg QW for 48 weeks with 24 weeks follow-up (Arm 1, n=100), or no treatment for 12 weeks followed by Peginterferon Lambda treatment for 48 weeks with 24 weeks of follow-up (Arm 2, n=50). All patients will receive concomitant therapy with a potent 2nd generation anti-HBV nucleos(t)ide analogue (NUC) throughout the study duration.

Data collected during Peginterferon Lambda treatment in Arm 2 will not be included in the primary analysis. The primary purpose of Arm 2 is to provide benchmark data in a parallel reference group for the expected rate of HDV RNA suppression among patients with chronic HDV infection who receive 12 weeks of anti-HBV NUC therapy alone.

Prior to randomization, all patients will enter a run-in phase with 12 weeks of anti-HBV NUC therapy, which will ensure virologic control of HBV (< 100 IU/mL) prior to randomization and start of Peginterferon Lambda therapy.

Inclusion Criteria:

• Chronic HDV infection documented by a positive HDV antibody test or a positive HDV RNA by RT PCR test for at least 6 months at Screening Visit 2
• Quantifiable HDV RNA by RT-PCR test at Screening Visit 2
• Documented confirmed suppression of HBV DNA (< 100 IU/mL) following at least 12 weeks of anti-HBV NUC treatment with ETV or a TNF-based NUC (TDF or TAF) at Screening Visit 2
• Serum ALT > upper limit of normal (ULN) and < 10 × ULN.
• Patients categorized with Child-Turcotte-Pugh score of ≤ 5 with well compensated liver disease.

Exclusion Criteria:

• History or current evidence of decompensated liver disease (episodes of bleeding esophageal or gastric varices, ascites and/or encephalopathy)
• Treatment with interferons (IFNs) or immunomodulators within 6 months before Screening Visit 2 or refractory to prior IFN treatment.