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Phase 3 Double‑Blind Relapse Prevention Trial of Trospium Chloride and Xanomeline Tartrate (KarXT) in Adults with Schizophrenia

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What is this trial about?

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

The study focuses on schizophrenia, a mental health condition that can cause disturbed thinking, hallucinations, and difficulty with daily activities. The medication being tested is called KarXT, which contains two active ingredients: trospium chloride and xanomeline tartrate. Both ingredients are taken by mouth in capsule form.

The purpose of the trial is to find out whether KarXT can keep symptoms from returning after they have become stable, compared with a pill that contains no active medicine. Participants who have reached a stable state are randomly assigned to continue taking the study drug or to switch to the inactive pill, and they are followed for several months while researchers monitor for any return of symptoms, the need for additional medication, or hospitalization.

During the study, participants attend regular clinic visits where doctors check mental health status using simple questionnaires and watch for any side effects. If symptoms worsen significantly, the participant may stop the study medication and receive appropriate care. The overall design allows researchers to compare the time it takes for symptoms to reappear between the two groups.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline Assessment After Joining the Study

    You will meet with the study doctor for a baseline assessment. This includes answering questions about your health, having a physical check‑up, and completing questionnaires that measure the severity of your schizophrenia symptoms.

    The purpose of this visit is to record your starting condition before you begin the double‑blind treatment period.

  2. Step 2

    Random Assignment to Double‑Blind Treatment

    After the baseline assessment, you will be randomly assigned to receive either KarXT or a placebo. Random assignment means the allocation is made by chance, and you will not know which one you receive.

    The study is double‑blind, which means neither you nor the study doctor will know whether you are taking KarXT or the placebo during the treatment phase.

  3. Step 3

    Starting the Study Medication

    You will be instructed to take one oral capsule each day. Each capsule contains 9999 mg of KarXT (a combination of trospium chloride and xanomeline tartrate) or an identical‑looking placebo capsule with no active medicine.

    The capsule is taken by mouth with water, preferably at the same time each day.

  4. Step 4

    Regular Clinic Visits for Safety and Symptom Monitoring

    You will attend scheduled visits at the study site throughout the treatment period. At each visit, the study doctor will check your vital signs, ask about any side effects (called adverse events), and review your medication adherence.

    You will also complete symptom questionnaires such as the PANSS (Positive and Negative Syndrome Scale) and the CGI‑S (Clinical Global Impression – Severity) to track any changes in your schizophrenia symptoms.

  5. Step 5

    Monitoring for Relapse

    The main goal of the trial is to see whether KarXT prevents relapse, which means a return or worsening of schizophrenia symptoms.

    If the questionnaires show a significant increase in scores, or if you experience worsening symptoms, the study doctor may decide that you have relapsed.

  6. Step 6

    Actions If Relapse Occurs

    If a relapse is identified, the study doctor may start a new antipsychotic medication, discontinue the study medication, or ask you to leave the trial for safety reasons.

    You will receive appropriate medical care, and the reason for stopping the study medication will be recorded.

  7. Step 7

    Continuation Until Study End or Early Discontinuation

    You will continue taking the assigned capsule daily and attending clinic visits until the study ends, you experience a relapse that requires stopping the medication, or you choose to withdraw from the trial.

    At the final visit, the study doctor will perform a concluding assessment to document your overall health status and any lasting effects.

Who can join the trial?

5 criteria

  • Be between 18 and 65 years old.
  • Have a confirmed diagnosis of schizophrenia that has lasted at least one year (a diagnosis means a doctor has determined you have this condition).
  • Have been hospitalized for schizophrenia at some time during the past year (hospitalized means staying in a hospital for treatment).
  • Currently show residual symptoms of schizophrenia (ongoing signs of the illness that remain even when the main symptoms are under control).
  • Reach the required minimum on two important assessments that measure how serious the schizophrenia symptoms are (an assessment is a test or questionnaire, and a score is the number you receive based on your answers).

Who cannot join the trial?

7 criteria

  • You must only have a diagnosis of schizophrenia; having any other mental health diagnosis means you cannot join the study.
  • You cannot have used drugs or alcohol heavily (called moderate to severe substance use disorder) within the past year.
  • If a urine drug screen (a test of your urine for drugs) or an alcohol test shows any substances, you cannot take part.
  • If you have thoughts of hurting yourself or other people, you are not allowed to join.
  • A past history of glaucoma (an eye disease that raises pressure inside the eye) excludes you.
  • Serious problems with bowel movements (such as constipation or diarrhea) or difficulty urinating (trouble passing urine) mean you cannot participate.
  • Women who are pregnant or breastfeeding are not eligible for the study.
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Investigated drugs

KarXT is an oral capsule that contains two active ingredients designed to work together to help control symptoms of schizophrenia. In this trial, people whose symptoms were already stable were given KarXT to see if it could keep their condition from getting worse again. The medication was taken by mouth and was compared with a placebo to test whether it can prevent relapse of schizophrenia symptoms.

What is already known about the treatment

KarXT - KarXT is taken as an oral capsule that you swallow whole. It is still an investigational drug being studied in phase 3 trials for schizophrenia. The medicine combines trospium chloride, which blocks certain peripheral nerve signals, with xanomeline tartrate, which stimulates brain receptors to help balance activity and reduce symptoms. Pharmacologically it is a mixed anticholinergic and muscarinic‑receptor agonist used as a novel antipsychotic.

Investigated diseases

Schizophrenia - Schizophrenia is a chronic mental disorder that affects thinking, perception, emotions, language, sense of self, and behavior. It usually starts in late adolescence or early adulthood. People may have episodes of hallucinations, delusions, and disorganized speech, along with periods of reduced motivation and social withdrawal. Symptoms can vary over time, with periods of relative stability followed by episodes of worsening. The illness often follows a relapsing‑remitting pattern, where symptom severity can increase again after a period of improvement.
Trial detailsLast updated 22 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523664-20-00Protocol codeCN0120006Estimated enrolment238 patientsSponsorBristol-Myers Squibb Services Unlimited Company

sourced from the EU Clinical Trials Register and site verification

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