This study is testing a new drug called RAP-219 to see if it helps adults with bipolar I disorder, a mental illness causing extreme mood swings. Researchers want to know if RAP-219 is safe and works well for people having a manic episode, which is when someone feels overly excited and energetic. This study will last for 3 weeks and takes place in a hospital setting where participants will stay overnight. It's a randomized and double-blind study, meaning neither the participants nor the researchers know who is getting the actual drug or a fake one (placebo).

• Study Length: 3-week stay in a hospital.
• Participation Requirements: Adults with bipolar I disorder and a history of manic episodes.
• Exclusions: People with certain other mental health issues like schizophrenia or substance abuse.

Participants must have had at least one past manic episode needing treatment. Some people cannot join, like those with schizophrenia or who have four or more mood episodes in a year. Joining the study might help find a new treatment for bipolar disorder, but there are risks, as with any drug trial.