This sponsor-open, investigator- and participant-blinded, multi-center study will assess the safety, tolerability, pharmacokinetics and pharmacodynamics of RO7020531 in healthy participants and in participants with chronic hepatitis B. Part I will be conducted in two portions: Single Ascending Dose (SAD) and Multiple Ascending Dose (MAD) which will include only healthy volunteers. Part II will commence after completion of the MAD portion of Part I and will include only Chronic Hepatitis B (CHB) participants.