This is a single ascending dose phase 1 study to evaluate the pharmacokinetics (PK), safety, and tolerability of a single intramuscular (IM) injection of quarterly Risperidone (QUAR) for different formulations and dose strengths in participants with schizophrenia.

The study will assess the PK, safety and tolerability of QUAR when administered as a single IM injection, in patients with schizophrenia. The study will be conducted with 3 different dose strengths and up to two formulations.

After eligibility confirmation, an oral treatment period follow by a washout period will be performed before QUAR IM administration.

The different cohorts will be administered with one of the following dosages of Risperidone QUAR:

Cohort 1/2: Formulation 1 or 2. Dose level 1 (Gluteal); Cohort 1a/2a: Formulation 1 or 2. Dose level 2 (Gluteal); Cohort 1b/2b: Formulation 1 or 2. Dose level 3 (Gluteal); Cohort 1c/2c: Formulation 1 or 2. Dose level 3 (Deltoid);

The progression to the next cohorts will take place after a clinical safety assessment. Several blood samples for plasma pharmacokinetic (PK) assessments will be obtained pre-dose and post-dose. Safety assessments will be conducted at each pre-specified time points.

After assessment of Cohort 1 (formulation 1, Dose Level 1, -gluteus-) progression to the next cohort with same formulation and escalating dose will take place (Cohort 1a -gluteus-). After assessment of Cohort 1a, progression and randomization (gluteus/deltoid) to the next cohorts with same formulation and escalating dose will take place (Cohort 1b -gluteus- and Cohort 1c -deltoid-). In this scenario, none of the Cohorts 2 will be conducted.

If the assessment for Cohort 1 is not adequate, none of the subsequent Cohorts 1 (a/b/c) will be conducted and progression to the next cohort (Cohort 2) with different formulation and same level of dose as Cohort 1 will take place (Cohort 2: Formulation 2, Dose Level 1 -gluteus-). After assessment of Cohort 2, progression to the next cohort with same formulation and escalating dose will take place (Cohort 2a -gluteus-). After assessment of Cohort 2a, progression and randomization (gluteus/deltoid) to the next cohorts with same formulation and escalating dose will take place (Cohort 2b -gluteus- and Cohort 2c -deltoid-).

Inclusion Criteria:

• Capable of providing informed consent.
• Male or female aged ≥ 18 years to < 65 years with BMI ≥17.0 to ≤35.0 kg/m2
• Current diagnosis of schizophrenia, according to the Diagnostic and DSM-5 criteria.
• Medically stable over the last month, and psychiatrically stable without significant symptom exacerbation over the last three months based on the investigator's judgment
• currently taking oral risperidone as maintenance therapy
• Score of ≤ 4 (moderately ill at most) on the Clinical Global Impression - Severity of Illness (CGI-S)
• If a sexually active female of childbearing potential, using a medically accepted method of birth control.

Exclusion Criteria:

• Presence of an uncontrolled, unstable, clinically significant medical condition that in the opinion of the investigator could interfere with the interpretation of safety and PK evaluations
• If female, a positive serum pregnancy test, or planning to become pregnant between signing informed consent and 1 month after the last dose of study drug or is breastfeeding a child.
• History of neuroleptic malignant syndrome and current or past history of clinically significant tardive dyskinesia.
• The participant has a primary diagnosis other than schizophrenia diagnosis that is primarily responsible for current symptoms and functional impairment
• Positive test result for drugs of abuse or alcohol unless the positive finding can be accounted for by documented prescription use.
• In the investigator's opinion, at imminent risk of committing self-harm or harm to others.
• Unwilling to discontinue any of the prohibited medications prior to the baseline visit or unable to safely washout such medication without significant destabilization or increased risk of self-harm (suicide).
• Receipt study drug in another investigational study in the last 90 days.
• Current participation in any other clinical trial.