The goal of this clinical trial is to learn about the safety and pharmacokinetics (PK, the amount of drug in the blood) of a new drug called CDI-988 in healthy volunteers.

The main questions it aims to answer are:

• Are there any side effects of the drug?
• What is the amount of drug that reaches the bloodstream? Participants will be assigned by chance to take either CDI-988 or placebo by mouth and have physical exams, electrocardiograms (ECGs), vital signs, and blood tests to look for any side effects.

CDI-988 is a severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) 3-chymotrypsin-like (3CL) protease inhibitor for oral administration. This study is being conducted in 2 parts to examine the safety, tolerability, and PK of CDI-988 in healthy participants. Part 1 will entail escalating single doses in sequential cohorts and Part 2 will enroll escalating multiple-dose cohorts. Participants will be monitored for adverse events, vital signs, laboratory values, and electrocardiograms (ECGs).

Inclusion Criteria:

• Healthy males or non-pregnant, non-lactating females
• Body weight of at least 45 kg.
• Body mass index ≥18.0 and ≤32.0 kg/m2
• Good state of mental and physical health
• Negative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test

Exclusion Criteria:

• Received an investigational drug within 30 days
• Received a coronavirus disease 2019 (COVID-19) vaccine within 7 days
• Drug or alcohol abuse in the past 12 months
• Clinically significant abnormal biochemistry, hematology, coagulation, urinalysis test results
• Clinically significant abnormal ECG or vital signs