The purpose of this study is to determine the safety, tolerability and pharmacokinetics of ALN-HBV in healthy adult volunteers and patients with chronic hepatitis B virus (HBV) infection. In addition, the study will assess antiviral efficacy of ALN-HBV in patients with HBV.

The study has 3 parts. Part A is a single ascending dose (SAD) study in healthy volunteers. Part B is a single ascending dose study (SAD) in patients with HBV infection. Part C is a multiple ascending dose study (MAD) in patients with HBV infection.

Inclusion Criteria:

All subjects:

• 18 to 65 years inclusive
• Women of child-bearing potential must have a negative pregnancy test, cannot be breast feeding, and must be willing to use a highly effective method of contraception
• Agrees not to donate blood during the duration of the study
• Willing to comply with the study requirements and to provide written informed consent

Additional inclusion criteria for patients with HBV infection:

• Body mass index (BMI) ≥18.0 kg/m2
• Must be on a stable regimen of entecavir or tenofovir

Exclusion Criteria:

All subjects:

• Any uncontrolled or serious disease, or any medical or surgical condition, that may either interfere with participation in the clinical study, and/or put the subject at significant risk
• Subjects with a history of serious mental illness
• Active infection with human immunodeficiency virus (HIV) infection, hepatitis A virus (HAV), or hepatitis C virus (HCV) infection and/or a history of delta virus hepatitis
• Known hypersensitivity or contraindication to any medication or history of allergic reaction to an oligonucleotide or N-acetylgalactosamine (GalNAc)

Additional exclusion criteria for healthy volunteers:

• Evidence of liver disease