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A Study of ACP-204 Tartrate for Adults With Lewy Body Dementia Psychosis

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study is looking at Lewy body dementia psychosis, a condition where people with Lewy body dementia experience symptoms such as seeing or hearing things that are not there or having false beliefs. Lewy body dementia is a brain disorder that affects thinking, movement, behavior, and mood. The treatment being tested is ACP-204, which is given as a capsule taken by mouth. This medication is being studied to see if it can help manage the symptoms of psychosis in people with this type of dementia.

The purpose of this study is to evaluate the safety and tolerability of long-term treatment with ACP-204 in people with Lewy body dementia psychosis. This study will last for 52 weeks, which is about one year. During this time, all participants will receive the study medication, and there will be different dose levels that may be given. The study is designed for adults who have already completed a previous study with ACP-204 and who may benefit from continuing to take this medication. Participants will need to attend study visits together with a caregiver or study partner who knows them well and can provide information about their condition.

Throughout the study, doctors will monitor participants regularly to check for any side effects or unwanted reactions to the medication. The study will collect information about any health problems that occur during treatment. Participants will continue to take the medication for the full year unless their doctor decides it is not safe or appropriate to continue. The study aims to understand how well people tolerate this medication when taken over a longer period of time compared to shorter studies.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline assessment

    This study begins immediately after completing the previous ACP-204-012 study. You will transition directly from that study into this extension study.

    You must have completed Visit 6 (end of treatment) of the previous study without stopping early to be eligible for this extension study.

    You will need to attend all study visits with your study partner or caregiver present throughout the entire study.

    If you are female, you must not be able to become pregnant. If you are male, you must agree to use a condom during sexual intercourse and your female partner must use additional birth control if she can become pregnant. These precautions must continue for at least 90 days after your last dose of the study medication. Males must also refrain from donating sperm during this time.

  2. Step 2

    Treatment with ACP-204

    You will receive ACP-204 tartrate in capsule form to take by mouth.

    This is an open-label study, which means both you and your doctor will know you are receiving the active medication.

    The treatment will continue for 52 weeks (approximately one year).

    Your doctor will determine the specific dosage and frequency of the capsules based on what may benefit you most.

    The medication is designed to treat psychosis symptoms associated with Lewy body dementia, which is a condition affecting the brain that can cause hallucinations and other changes in thinking and perception.

  3. Step 3

    Regular monitoring visits

    Throughout the 52-week treatment period, you will attend scheduled study visits at the study site.

    During these visits, the study team will monitor your safety and how well you tolerate the medication.

    Your study partner or caregiver must accompany you to each visit.

    The study team will assess any side effects or health changes you experience, known as treatment-emergent adverse events.

  4. Step 4

    End of treatment

    After completing the 52-week treatment period, you will have a final assessment.

    The study is expected to continue enrolling participants until December 2025 and will conclude by February 2028.

    All information collected during the study will be used to evaluate the long-term safety of ACP-204 for treating psychosis in people with Lewy body dementia.

Who can join the trial?

7 criteria

  • You must have completed the previous study called ACP-204-012 through the end of treatment visit without stopping early
  • Your doctor believes that you may benefit from long-term treatment with the study medication ACP-204
  • You must be able to attend all study visits with a study partner or caregiver, which is someone who knows you well and can accompany you to appointments
  • You must be able to understand what the study involves and sign a consent form agreeing to participate, or if you are not able to make this decision yourself, a legally authorized representative (someone legally allowed to make decisions on your behalf) must sign the consent form and you must agree to participate
  • If you are a woman, you must not be able to become pregnant, meaning you have gone through menopause (the natural end of monthly periods) or have had surgery that prevents pregnancy
  • If you are a man, you must agree not to donate sperm during the study and for at least 90 days after your last dose of study medication
  • If you are a man who is sexually active with a woman who could become pregnant, you must either avoid sexual intercourse completely during the study and for 90 days after, or use a condom and your female partner must also use a reliable birth control method

Who cannot join the trial?

3 criteria

  • The source data does not provide specific exclusion criteria, which are reasons why a patient cannot participate in the study
  • Without detailed information about who cannot join this clinical trial, it is not possible to list the specific conditions or situations that would prevent participation
  • Generally, clinical trials have rules about who can and cannot participate, but these specific details are not available in the provided information
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Investigated drugs

ACP-204 is an investigational medication being studied for the treatment of psychosis in adults with Lewy body dementia. This medication is being tested to see if it is safe and well-tolerated when taken over a long period of time. The study is looking at how this medication works in patients who experience hallucinations, delusions, or other psychotic symptoms related to their Lewy body dementia.

What is already known about the treatment

ACP-204 – ACP-204 is an investigational medication currently being studied in clinical trials and is not yet approved for general medical use. It is being tested as a treatment for psychosis that occurs in people with Lewy body dementia, a brain disorder that affects thinking, movement, and behavior. The medication is taken orally, and researchers are examining how safe it is when used over a long period of time, specifically looking at whether patients can tolerate it well for up to 52 weeks. The exact way ACP-204 works in the brain has not been fully described in available trial information, but it is designed to reduce hallucinations and delusions in patients with this type of dementia.

Investigated diseases

Lewy Body Dementia – Lewy body dementia is a brain disorder that occurs when abnormal protein deposits called Lewy bodies build up in nerve cells in the brain. This condition affects thinking abilities, memory, and movement control. People with this disease often experience changes in attention and alertness that can vary throughout the day. Visual hallucinations, where people see things that are not really there, are common in this condition. The disease also causes problems with movement similar to Parkinson's disease, including slow movements, stiff muscles, and tremors. As the condition progresses, it becomes increasingly difficult for affected individuals to perform daily activities and maintain independence.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521711-39-00Protocol codeACP-204-013Estimated enrolment126 patientsSponsorAcadia Pharmaceuticals Inc.

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).