Evaluate the Safety, Tolerability, PK and PD of SAD of Intravenously Adminsterted ALTB-268 in Healthy Participants

This is a first-in-human safety study of a new investigational drug called ALTB-268, given by IV infusion, in healthy adults. The study is testing single doses to see how the drug behaves in the body and whether it causes any side effects before it can be tested in patients with a specific disease. **You may be eligible if...** - You are 18–55 years old - You are a healthy non-smoker (no tobacco or nicotine use in the past 3 months) - You have a BMI between 18.5 and 32 and weigh at least 50 kg (men) or 45 kg (women) - You have no significant medical, mental health, or surgical history - For women: you are post-menopausal or have had surgical sterilization **You may NOT be eligible if...** - You have any clinically significant abnormal findings on physical exam or lab tests - You test positive for hepatitis B, hepatitis C, HIV, or tuberculosis - You have any history of suicidal thoughts, depression, or score above a mild level on mood questionnaires - You have had any serious mental health history Talk to your doctor to see if this trial is right for you.