This is three part study that will, in part one assess the safety, tolerability, and PK of a single dose of CRV431 in healthy volunteers. The second part of the study will be a single dose drug-drug interaction study in healthy volunteers with CRV431 co-treated with TDF. The third part of the study will assess the safety, tolerability, PK, and preliminary signal for antiviral efficacy and identification of clinically-relevant biomarkers of CRV431 with TDF in stable HBV patients.

Inclusion Criteria:

• Capable of giving written informed consent
• Willing and able to complete all study requirements
• Healthy male or female between 18 and 55 years of age (inclusive);
• Body mass index 16 to 32 kg/m2 (inclusive);

Exclusion Criteria:

• Positive test for HCVAb or HIVAb. For healthy subjects only: positive test for HBsAg
• Current or history of abuse of alcohol or illicit drugs
• Received an investigational drug, vaccine or medical device within 90 days prior to first dose of study drug.

Additional Exclusion Criteria for HBV Pilot Subjects Only:

• Evidence of significant liver fibrosis or cirrhosis
• History of NAFLD or NASH
• Positive test for HDV