This is a study of the efficacy and safety of BXCL501 in children and adolescents with acute agitation and either bipolar disorder or schizophrenia.

The study will enroll approximately 140 subjects randomized to dose regimens of 80 µg or 120 µg BCXL501 or placebo (Group one), or 60 µg BCXL501 or placebo (Group two; Europe only). Subjects with acute agitation will include male and female children and adolescents who are either newly admitted to a hospital setting or already admitted and experiencing acute agitation. Subjects will be domiciled in a clinical research setting or hospitalized to remain under medical supervision while undergoing screening procedures to assess eligibility. Efficacy and safety assessments will be conducted periodically before and after dosing.

Inclusion Criteria:

1. Male and female subjects between the ages of 10-17 years, inclusive, with bipolar disorder (DSM-5 criteria) and 13-17 years, inclusive, in subjects with schizophrenia (DSM-5 criteria).
2. Patients who are judged to be clinically agitated at Screening and Baseline with a total score of ≥14 on the 5 items comprising the PANSS Excited Component (PEC).
3. Patients who have a score of ≥ 4 on at least 1 of the 5 items on the PEC at Baseline.
4. Participants who agree to use a medically acceptable and effective birth control method

Exclusion Criteria:

1. Patients with agitation caused by acute intoxication, including alcohol or drugs of abuse (with the exception of THC) during urine screening.
2. Use of benzodiazepines or other hypnotics or oral or short-acting intramuscular antipsychotic drugs in the 4 hours before study treatment.
3. Patients who are judged to be at significant risk of suicide.
4. Patients with serious or unstable medical illnesses.
5. Patients who have received an investigational drug within 30 days prior to the current agitation episode.
6. Patients who are considered by the investigator, for any reason, to be an unsuitable candidate for receiving the study drug.

Double-Blind, Placebo-controlled