Activity of NCO-48 Fumarate in Treatment-Naive Adults With Chronic Hepatitis B

Inclusion Criteria: * Adult male and female subjects between 18 and 65 years of age * Female subjects of non-childbearing potential must be surgically sterile or postmenopausal at the Screening Visit * Female subjects of childbearing potential who are sexually active with a non-sterile male partner must be using a medically acceptable form of birth control for the duration of the study and for 30 days after the last dose of study drug and must have a negative serum pregnancy test at the Screening Visit and a negative urine pregnancy test upon admission to the study site * HBV treatment-naive or treatment-experienced with (pegylated or non pegylated) interferon alpha (must have ended at least 6 months prior to the Screening Visit) * Screening plasma HBV DNA ≥ 2x10\^3 IU/mL * Positive for serum hepatitis B surface antigen for more than 6 months * Estimated creatinine clearance (CLCr) ≥ 70 mL/min * Serum transaminase activity (aspartate aminotransferase \[AST\] and/or alanine aminotransferase \[ALT\] levels) \<10 x the upper limit of normal * Compensated liver disease with normal prothrombin time/international normalized ratio, hematology, albumin, bilirubin (unless subject has Gilbert's disease). Serum AST and/or ALT levels may be normal or elevated * Body mass index within the range of 18.5 to 35 kg/m2, inclusive, and body weight \>45 kg * Normal vital signs, without any clinically significant abnormalities at the Screening Visit * Subjects who have normal or abnormal clinically insignificant clinical laboratory assessments as considered by the Investigator from pre-treatment blood tests to assess hematology, liver (except for serum AST and/or ALT levels) and renal biochemistry, urinalysis, and drug screen * Normal 12-lead electrocardiogram (ECG), with no clinically significant abnormalities of rate, rhythm, or conduction and including normal heart rate-corrected QT interval segment time at the Screening Visit Exclusion Criteria: * Received treatment with TFV disoproxil fumarate or TAF (including clinical study experience) * Positive for hepatitis C virus (HCV) or human immunodeficiency virus (HIV) * History or presence of asthma or other pulmonary disease, thyroid disease, or other liver disease * Hematologic, cardiovascular, pulmonary, renal, gastrointestinal, hepatic, or central nervous system; or other conditions that may interfere with the absorption, distribution, metabolism, or excretion of study drug, or would place the subject at increased risk * Abnormal laboratory values that are considered clinically significant * Have used medication, other than topical products without significant systemic absorption, hormonal contraceptives, or hormone replacement therapy and thyroid medication for at least 6 months * Unwilling to refrain from consumption of alcohol within 48 hours prior to each dose of study drug and during the inpatient period, or have a history of significant alcohol abuse within 1 year prior to Screening * Positive urine drug screen, or positive alcohol breath test at Screening or upon admission to the study site * Use of illicit drugs within 3 months prior to the Screening Visit or hard drugs within 1 year prior to the Screening Visit, significant mental illness, physical dependence to any opioid, or any history of drug abuse or addiction * Women who are breastfeeding or have a positive pregnancy test at the Screening Visit or at any time during the study