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Long‑Term Safety and Tolerability of KarXT in Adolescents with Schizophrenia and of KarXT + KarX‑EC in Children and Adolescents with Autism‑Related Irritability

Verified siteInvestigationalNo placebo
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What is this trial about?

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

The study looks at two conditions: Schizophrenia in teenagers aged 13‑17 and irritability that can occur in children and adolescents with Autism Spectrum Disorder. The medication being tested is a combination capsule that contains two active ingredients, trospium chloride and xanomeline tartrate. The product is known by the code name KarXT when both ingredients are used, and by KarX-EC when only xanomeline tartrate is given. The main aim of the trial is to see how safe and tolerable the medicine is when taken for a long period.

Participants will take the study drug by mouth every day for several months, with regular visits to check for any side effects and to answer simple questionnaires. Researchers will monitor for any new health problems, serious problems, and specific symptoms related to the study drugs. They will also use a few rating tools to watch for movement‑related side effects and to assess thoughts of self‑harm, using the C-SSRS questionnaire and movement scales called the SAS, BARS, and AIMS. The study ends after the treatment period and a short follow‑up to confirm the safety findings.

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

    Enrollment and baseline assessments

    After joining the study, a series of baseline assessments are performed. these include a medical history review, a physical examination, and questionnaires that record current symptoms of schizophrenia or autism spectrum disorder and related irritability.

    The purpose of these assessments is to create a reference point for later comparison during the study.

  2. Step 2

    Starting study medication

    Based on the assigned group, you will receive either karxt alone (for schizophrenia) or the combination of karxt plus karx-ec (for irritability associated with autism).

    Each dose consists of a capsule containing 9999 mg of the active ingredients. the capsule is taken by mouth (oral) as directed by the study team.

  3. Step 3

    Daily medication administration

    The study medication is taken each day, usually at the same time, with a glass of water.

    It is important to follow the dosing instructions exactly and not miss any doses unless instructed otherwise.

  4. Step 4

    Regular clinic visits for safety monitoring

    Throughout the treatment period you will attend scheduled clinic visits. during each visit vital signs, laboratory tests, and physical examinations are performed to monitor your health.

    You will also complete brief questionnaires, such as the columbia suicide severity rating scale (c-ssrs), which asks about thoughts of self‑harm, and other rating scales that assess movement‑related side effects.

  5. Step 5

    Reporting adverse events

    Any unwanted medical occurrence, whether it is thought to be related to the study drug or not, should be reported to the study staff. these are called treatment‑emergent adverse events.

    Serious problems, called serious adverse events, and events of special interest are also recorded and evaluated.

  6. Step 6

    Continuation of treatment

    The medication is continued for the entire duration of the study, which may extend for several years until the study end date of 2030‑03‑08, unless you or the study team decide to stop earlier.

  7. Step 7

    Final safety follow‑up

    After the last dose of study medication, a final safety follow‑up visit is scheduled. this visit includes the same assessments as earlier visits to ensure that any lingering effects are identified and managed.

Who can join the trial?

9 criteria

  • You must be between 13 and 17 years old when you agree to join the study for schizophrenia.
  • You must have a diagnosed schizophrenia (a mental health condition that changes how a person thinks, feels, and acts).
  • You must have finished the earlier study’s double‑blind treatment period (called Visit 8) and not have any safety problem that the doctor thinks is too risky.
  • You must be between 5 and 17 years old when you agree to join the study for irritability linked to ASD.
  • You must have a diagnosed Autism Spectrum Disorder (ASD) (a developmental condition that can affect social interaction and behavior).
  • You must have irritability related to ASD (meaning frequent or strong upset, anger, or aggression).
  • You must have finished the earlier study’s double‑blind treatment period (called Week 8) and not have any safety problem that the doctor thinks is too risky.
  • Both boys and girls are allowed to take part in the study.
  • Because participants are children or teenagers, they are considered a vulnerable group and receive extra protection.

Who cannot join the trial?

5 criteria

  • If you were in study CN0120020 and your main diagnosis (the primary condition identified by doctors) is not schizophrenia, you cannot take part.
  • If you were in study CN0120020 and have a moderate or severe substance use disorder (problematic use of drugs or alcohol) within the past year, you cannot take part.
  • If, at the final visit of study CN0120020, CN0120044, or CN0120045, doctors found important problems in your physical exam, electrocardiogram (a test that records the heart’s electrical activity), or vital signs such as heart rate or blood pressure, and think these could affect your safety, you cannot take part.
  • Women who are currently pregnant or breastfeeding (feeding a baby with breast milk) cannot take part.
  • If you were in study CN0120044 or CN0120045 and your main psychiatric condition is not ASD (Autism Spectrum Disorder), you cannot take part.
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Investigated drugs

  • KarXT

    is an oral capsule that contains two medicines working together. One part helps calm the brain’s activity, and the other part helps improve thinking and mood. In this study the drug is being given to teenagers with schizophrenia to see if it is safe for long‑term use, and it is also being tested together with KarX‑EC in children and adolescents with autism‑related irritability.

  • KarX-EC

    is an oral capsule that contains only the brain‑stimulating component of KarXT. It is meant to help reduce irritability and improve behavior. In the trial it is used together with KarXT to evaluate whether the combination is safe and well‑tolerated for children and adolescents who have irritability associated with autism spectrum disorder.

What is already known about the treatment

  • KarXT

    KarXT is taken as an oral capsule that contains trospium chloride and xanomeline tartrate. It is currently an investigational drug being studied in phase 3 trials for schizophrenia and for irritability associated with autism spectrum disorder. Xanomeline works by gently activating certain brain receptors (muscarinic receptors) that help regulate mood and thinking, while trospium stays mostly outside the brain and blocks similar receptors in the gut to reduce side effects. The combination is classified as a muscarinic receptor agonist paired with a peripheral anticholinergic.

  • KarX-EC

    KarX-EC is an oral capsule that contains only xanomeline tartrate. It is also investigational and is being evaluated in phase 3 studies for irritability in children and adolescents with autism spectrum disorder. Xanomeline activates muscarinic receptors in the brain, which can improve mood, attention and social behavior. It is classified as a muscarinic receptor agonist.

Investigated diseases

  • Schizophrenia

    Schizophrenia is a chronic brain disorder that changes how a person thinks, perceives reality, feels, and behaves. Early signs often appear in the late teens or early twenties and may start with social withdrawal, unusual thoughts, or reduced motivation. Over time these signs can become more noticeable and may develop into hearing voices, strong false beliefs, or disorganized speech. Mood changes and difficulty with daily tasks can also emerge. The condition usually follows a pattern of periods when symptoms worsen and periods when they become less intense, but it tends to persist throughout life.

  • Autism Spectrum Disorder

    Autism Spectrum Disorder is a neurodevelopmental condition that affects social interaction, communication, and behavior from early childhood. Typical early signs include limited eye contact, delayed language development, and repetitive movements. As the child grows, these patterns often become more fixed, while some communication skills may improve with experience. Sensory sensitivities and a strong preference for routine often continue into later years. The condition follows a lifelong pattern, with each person showing a unique combination of strengths and challenges.

Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2025-524062-16-00Protocol codeCN0120021Estimated enrolment300 patientsSponsorBristol-Myers Squibb Services Unlimited Company

sourced from the EU Clinical Trials Register and site verification

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