A 52-Week, Phase 3, Open-Label Extension Study of ACP-204 in Adults With Lewy Body Dementia Psychosis (LBDP)

The primary objective is to evaluate the **safety** and **tolerability** of long-term **ACP-204** treatment in subjects with **Lewy body dementia psychosis** (LBDP). This objective addresses the critical need to assess the risk-benefit profile of extended therapeutic intervention in patients experiencing psychotic symptoms associated with Lewy body dementia, a condition characterized by complex neuropsychiatric manifestations requiring careful monitoring during prolonged pharmacological management.

The secondary objective focuses on safety evaluation: to assess the safety and tolerability of long-term ACP-204 treatment in subjects with LBDP based on additional safety measures. This secondary endpoint provides supplementary data to comprehensively characterize the adverse event profile and tolerability parameters over extended treatment duration.

This clinical trial enrolled a total of **77 participants** diagnosed with **Lewy body dementia psychosis**. The study population included both **male and female subjects** who were classified as **adults** and **elderly** individuals. Participants were selected based on their completion of Visit 6 (end of treatment) in the antecedent ACP-204-012 study without early discontinuation, and the investigator's judgment that they could benefit from long-term open-label ACP-204 treatment. All subjects were required to attend study visits accompanied by a study partner or caregiver. Female participants had to be of nonchildbearing potential, while male participants were required to refrain from sperm donation and either practice long-term sexual abstinence or use condoms with additional contraceptive methods employed by female partners of childbearing potential during the study period and for at least 90 days after the last dose. The trial involved a **vulnerable population**. Subjects or their legally authorized representatives were required to provide written informed consent, with assent from subjects when applicable according to local regulations.

This is a Phase 3, open-label extension study evaluating the long-term safety and tolerability of ACP-204 in adults with Lewy body dementia psychosis. The study is designed as a continuation trial for subjects who have completed the antecedent ACP-204-012 study. The primary objective is to assess the safety and tolerability of long-term ACP-204 treatment in subjects with this condition. The primary endpoint is the occurrence of treatment-emergent adverse events (TEAEs). The investigational medicinal product, ACP-204 tartrate, will be administered orally in capsule form. Two dose levels are evaluated: a maximum daily dose of 30 mg and a maximum daily dose of 60 mg. The maximum treatment period is 52 weeks, with a maximum total dose of 10920 mg for the lower dose regimen and 21840 mg for the higher dose regimen.

Eligible subjects must have completed Visit 6 (end of treatment) of the antecedent ACP-204-012 study without early discontinuation and must be judged by the investigator to potentially benefit from long-term open-label ACP-204 treatment. Subjects must be able to complete all study visits accompanied by a study partner or caregiver. Informed consent must be obtained from the subject or, if the subject is not competent to provide consent, from a legally authorized representative (LAR) or study partner/caregiver as permitted by local regulations, with the subject providing written assent when capable. Female subjects must be of non-childbearing potential. Male subjects must agree to refrain from sperm donation and either practice abstinence or use contraception during the study intervention period and for at least 90 days after the last dose of study drug.

The overall trial duration is estimated to span from December 2025 to February 2028. Subject involvement extends for up to 52 weeks of treatment. The study visits include an enrollment visit for subjects transitioning from the antecedent study, followed by regular follow-up visits throughout the 52-week treatment period to monitor safety and tolerability. An end-of-study visit is conducted upon completion of the treatment period or at the time of early discontinuation. Conditions that may lead to early termination from the study include adverse events, withdrawal of consent, investigator decision, or other safety concerns as determined during the course of the trial.

The experimental medication under investigation is ACP-204, which contains the active substance ACP-204 tartrate of chemical origin. The medicinal product is manufactured by ACADIA Pharmaceuticals and is formulated as capsules for oral use. Two dosage strengths of ACP-204 capsules are utilized in this clinical trial to accommodate different dosing regimens.

The first dosage formulation provides a maximum daily dose of 60 mg, with a maximum total dose of 21,840 mg administered over the treatment period. The second dosage formulation provides a maximum daily dose of 30 mg, with a maximum total dose of 10,920 mg over the same duration. Both formulations are administered throughout a maximum treatment period of 52 weeks. The dosing units are expressed in milligrams for both daily and total dose amounts.

This is an open-label extension study designed to evaluate the safety and tolerability of long-term ACP-204 treatment in subjects with Lewy body dementia psychosis. The trial design does not include a placebo or comparator treatment arm, as all participants receive active ACP-204 treatment. The study protocol designates ACP-204 as the test medicinal product, with both capsule formulations serving the same therapeutic role in the investigation.

The primary efficacy endpoint in this clinical trial is the evaluation of treatment-emergent adverse events (TEAEs). This open-label extension study focuses primarily on assessing the safety and tolerability of long-term ACP-204 treatment in subjects with Lewy body dementia psychosis over a treatment period of 52 weeks. The trial will monitor and collect data on adverse events that emerge during the course of treatment to characterize the safety profile of extended ACP-204 administration in this patient population.