a study of jnj-73763989 + nucleos(t)ide analog in participants co-infected with hepatitis b and hepatitis d virus

Conditions: Hepatitis D, Chronic

Summary: the purpose of the study is to evaluate on-treatment efficacy against hepatitis d virus (hdv) of jnj-73763989 + nucleos(t)ide analog (na) regimen compared to na alone.


Eligibility criteria:
inclusion criteria: * medically stable based on physical examination, medical history, vital signs, electrocardiogram (ecg) at screening * chronic hepatitis b virus (hbv) and hepatitis d virus (hdv) co-infection with documentation at least 6 months prior to screening * for part 1: hepatitis d rna (hdv rna) greater than or equal to (\>=) 1000 international units per milliliter (iu/ml) at screening. for part 2: must have hdv rna values \>= 500 iu/ml, and must have hepatitis b surface antigen (hbsag) values less than or equal to (\<=) 10000 iu/ml at screening or hdv rna values at screening are \<= 100000 iu/ml * alanine aminotransferase (alt) greater than upper limit normal (uln) but less than 10 times (uln) * body mass index (bmi) between 18.0 and 35.0 kilogram per meter square (kg/m\^2), extremes included * highly effective contraceptive measures in place for female participants of childbearing potential or male participants with female partners of childbearing potential * non-cirrhotic participants and participants with compensated cirrhosis (child pugh class a) at screening (part 1) and participants must have absence of cirrhosis and platelet count of \>= 140000 per deciliter (dl) for enrollment into part-2 exclusion criteria: * evidence of infection with hepatitis a, c, or e virus infection or evidence of human immunodeficiency, virus type 1 (hiv-1) or hiv-2 infection at screening * history or evidence of clinical signs/symptoms of hepatic decompensation including but not limited to: portal hypertension, ascites, hepatic encephalopathy, esophageal varices or any laboratory abnormalities indicating a reduced liver function as defined in the protocol * evidence of liver disease of non-hbv/hdv etiology * signs of hepatocellular carcinoma (hcc) * significant laboratory abnormalities as defined in the protocol at screening * participants with a history of malignancy within 5 years before screening * abnormal sinus rhythm or ecg parameters at screening as defined in the protocol * history of or current cardiac arrhythmia or history or clinical evidence of significant or unstable cardiac disease * participants with any current or previous illness for which, in the opinion of the investigator and/or sponsor, participation would not be in the best interest of the participant * history of or current clinically significant skin disease or drug rash * participants with known allergies, hypersensitivity, or intolerance to jnj-3989 or its excipients or excipients of the placebo content * contraindications to the use of entecavir (etv), tenofovir disoproxil, or tenofovir alafenamide (taf) per local prescribing information * participants who have taken any therapies disallowed per protocol * female participants who are pregnant, or breast-feeding, or planning to become pregnant while enrolled in this study or within 90 days after the last dose of study intervention * male participants who plan to father a child while enrolled * participants who had or planned major surgery, (example, requiring general anesthesia) or who have received an organ transplant * vulnerable participants (example, incarcerated individuals, individuals under a legal protection measure)