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 prior to Screening Quantifiable HDV RNA by RT-PCR test at Screening 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) 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 variceal bleeding, ascites or encephalopathy) Treatment with interferons (IFNs) or immunomodulators within 12 months of randomization or refractory to prior IFN treatment.