The primary purpose of this study is to determine the safety and tolerability of AB801, and to understand the pharmacokinetic (PK) profile of AB801 when taken as a capsule and tablet in healthy volunteers.

Key Inclusion Criteria:

• Healthy as determined by medical evaluation by study physician
• Body mass index (BMI) of 18.0 to 32.0 kilogram (kg)/meter (m)^2 as measured at screening
• Weight ≥ 50 kg at screening
• Must agree to adhere to the protocol defined contraception requirements

Key Exclusion Criteria:

• Do not have suitable veins for multiple venepunctures/cannulation as assessed by the study physician
• Prolonged QT interval defined as mean Corrected QT interval by Fridericia's formula (QTcF) ≥ 450 msec for males and > 470 millisecond (msec) for females at screening and pre-dose
• Clinically significant abnormal clinical chemistry, haematology or urinalysis as judged by the study physician
• Received any study medicine in a clinical research study within the last 90 days
• Taking, or have taken, any prescribed or over-the-counter drugs including gastric acid reducing agents and including CYP3A inhibitor and/or inducers

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Arcus will provide access to individual de-identified participant data and related study documents (e.g., protocol, Statistical Analysis Plan [SAP], Clinical Study Report [CSR]) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions.

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