This study is testing a new medicine, **BXCL501**, to see if it helps calm kids and teens with **schizophrenia** or **bipolar disorder** who are feeling very upset. Schizophrenia affects how a person thinks, feels, and behaves, while bipolar disorder causes extreme mood swings. The study will have about 140 participants who will receive either BXCL501 or a **placebo** (a fake pill with no medicine) in different doses. Everyone in the study will stay in a hospital or research center to make sure they are safe and to check if the medicine works.

To join, participants must be between 10 and 17 years old, have bipolar disorder or schizophrenia, and be very agitated. They must also agree to use birth control. People who are not allowed to join include those who are intoxicated, have taken certain medicines recently, are very sick, or are at risk of harming themselves.

• Study includes hospital stay for safety checks.
• Participants must be between 10-17 years old with specific conditions.
• Excludes recent drug trials and certain medical conditions.