This study looks at how safe and easy it is for kids with Autism Spectrum Disorder (ASD) to take a medicine called lumateperone. Kids in the study will be aged between 5 and 12 and a half. They should have some symptoms of irritability and be able to swallow capsules. The study will not include kids with other main mental health problems or those with a history of certain health issues. The goal is to check how the medicine behaves in the body (this is called pharmacokinetics, or PK).

• The study is open-label, meaning everyone knows what medicine is being taken.
• It's a Phase 1b study, which is an early step in testing a new treatment.
• Many centers will help conduct this study, making it a multicenter study.

The doctors will watch for any side effects (safety and tolerability) and see how the medicine moves and changes in the body (PK). The study won't include kids with a history of certain heart issues, suicidal thoughts, and behaviors, or those with uncontrollable behaviors. If you are thinking about joining, it is important to talk to your doctor about it first.