This is a Phase 1B clinical study evaluating the safety and exploring the effectiveness of SP-624 as compared to placebo in the treatment of adults with schizophrenia experiencing acute psychosis.

Key Inclusion Criteria:

• Is willing and able to provide written informed consent to participate in the study.

• Has an identified reliable informant.

• Is, in the investigator's opinion, suitable for initiating a washout from the subject's current antipsychotic regimen, if applicable, and is willing to abstain from prohibited psychotropic medications in accordance with study requirements.

  • Subjects must meet screening eligibility criteria and be in an inpatient setting prior to discontinuing antipsychotic medications.
  • Subject must be able, in the investigator's opinion, to safely discontinue prohibited psychotropic medications prior to Baseline without increased suicidality.

• Has a primary diagnosis of schizophrenia based on the Diagnostic and Statistical Manual 5th edition (DSM-5) criteria and confirmed by Mini International Neuropsychiatric Interview (MINI) for Psychotic Disorders Studies.

• Is experiencing an acute exacerbation or relapse of symptoms.

• Is in generally good physical health, in the investigator's opinion, based on Screening medical history, physical examination, vital signs, and clinical laboratory values.

• Has a body mass index (BMI) between 18 and 40 kg/m2, inclusive.

• For women of reproductive potential: has a negative serum pregnancy test at Screening and a negative urine pregnancy test at Baseline.

• For women of reproductive potential and men with female partners of reproductive potential: agrees to remain abstinent from sexual intercourse or use adequate and reliable contraception throughout the study and for at least 30 days after the last dose of study drug.

Key Exclusion Criteria:

• Is a woman who is pregnant, breastfeeding, or less than 6 months postpartum at Screening.
• Has any primary DSM-5 disorder other than schizophrenia, as confirmed by the MINI.
• Fails to discontinue prohibited psychotropic medications.
• Has, in the investigator's opinion, a significant risk of violent or destructive behavior.
• Is currently hospitalized involuntarily or incarcerated.
• Has a history or presence of any clinically significant medical condition, disease, or surgical history that could, in the investigator's opinion, jeopardize the safety of the subject or validity of the study data, or interfere with the absorption, distribution, metabolism, or excretion of the study drug.
• Is, in the investigator's opinion, not a suitable candidate for the study.