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Long-term safety study of trospium chloride and xanomeline tartrate combination (KarXT) in patients with inadequately controlled schizophrenia symptoms

Fast replyInvestigationalNo placebo
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What is this trial about?

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

This study focuses on people with schizophrenia, a serious mental health condition that affects how a person thinks, feels, and behaves. The study will test a medication called KarXT, which contains two active substances: trospium chloride and xanomeline tartrate. KarXT will be given as additional treatment alongside the patient's current antipsychotic medication to help manage symptoms that are not well controlled by their existing treatment.

The purpose of this research is to evaluate the long-term safety and how well patients tolerate KarXT when it is used together with their regular antipsychotic medication. The medication comes in the form of capsules that are taken by mouth. Different doses of KarXT will be tested during the study, which will last for up to 52 weeks.

During the study, participants will continue taking their regular antipsychotic medication while also receiving KarXT. The healthcare team will monitor participants throughout the study period to track any side effects that may occur and assess how well patients tolerate the combination of medications. This is a continuation study for people who have completed a previous trial with KarXT.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial qualification

    You must be between 18 and 65 years old to participate in this study

    You need to have completed the previous treatment period of Study KAR-012 (through Visit 8)

    You must be taking an approved antipsychotic medication from the previous KAR-012 study

    You must be able to understand and sign the informed consent form

  2. Step 2

    Living arrangements and support

    Your living situation must be considered stable

    You need to have a reliable person who can assist with study activities

    This support person may complete some assessments by phone, except in Bulgaria where in-person presence may be required

  3. Step 3

    Medication requirements

    You will receive KarXT capsules to take by mouth

    You must continue taking your current antipsychotic medication at the same dose throughout the study

    The study will evaluate how safe and well-tolerated KarXT is when taken alongside your current medication

  4. Step 4

    Safety measures

    If you or your partner can become pregnant, you must use at least one highly effective method of birth control during the study

    Birth control must continue for at least 30 days after the last dose of study medication

    Male participants cannot donate sperm for 30 days after the final dose

  5. Step 5

    Study duration

    The study is expected to run from March 2022 to April 2026

    During this time, you will be monitored for any side effects that may occur while taking the medication

    The study will track both mild and serious side effects, as well as any effects that might lead to stopping the medication

Who can join the trial?

14 criteria

  • Age between 18 and 65 years old
  • Must have completed treatment period of Study KAR-012 successfully
  • Must have followed all required procedures in Study KAR-012 properly
  • Must be taking prescribed antipsychotic medication (APD) regularly and continue with the same medication and dose throughout the study
  • Must be able to understand and sign an informed consent form (ICF) in the language it is written
  • Must have a stable living situation
  • Must have a reliable person (informant/caregiver) who can help with study activities. This person can participate in assessments by phone (except in Bulgaria, where in-person presence may be required)
  • For women who can become pregnant and men with partners who can become pregnant:
    • Must use at least one highly effective birth control method during the study
    • Must continue birth control for at least 30 days after the last study drug dose
    • Men cannot donate sperm for 30 days after the final study drug dose
    • Women are considered able to become pregnant unless they have:
      • Been in menopause for 12 months
      • Had their uterus removed (hysterectomy)
      • Had both fallopian tubes removed (bilateral salpingectomy)
      • Had both ovaries removed (bilateral oophorectomy)

Who cannot join the trial?

14 criteria

  • Age below 18 or above 65 years
  • Current diagnosis of substance use disorder (addiction to drugs or alcohol) within the past 3 months
  • History of seizures or other significant neurological conditions
  • Unstable medical conditions that could interfere with study participation
  • Pregnancy or breastfeeding
  • Use of medications that could interact with the study drug
  • Participation in another clinical trial within the past 30 days
  • History of serious suicide attempts or current suicidal ideation (thoughts about suicide)
  • Significant heart problems or abnormal heart rhythm
  • Uncontrolled hypertension (high blood pressure)
  • History of not following prescribed medication schedules
  • Severe kidney or liver problems
  • Known allergic reactions to similar medications
  • Unable to provide informed consent
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Investigated drugs

KarXT is an investigational medication designed to help people with schizophrenia who are not getting enough relief from their current treatment. It works as an add-on therapy, meaning it is taken alongside existing schizophrenia medications. KarXT targets specific receptors in the brain that are involved in controlling symptoms of schizophrenia. This medication aims to improve symptoms while potentially having a different side effect profile compared to currently available treatments.

What is already known about the treatment

KarXT – An investigational medication administered orally as an adjunctive therapy for patients with schizophrenia who have inadequate response to current treatments. It represents a novel approach in schizophrenia treatment, combining xanomeline (a muscarinic receptor agonist) and trospium (a muscarinic receptor antagonist) to reduce side effects while maintaining therapeutic efficacy. The medication works by selectively targeting M1/M4 muscarinic receptors in the central nervous system, which are involved in the regulation of neurotransmitter systems affected in schizophrenia, while trospium helps minimize peripheral cholinergic side effects. Currently undergoing clinical trials to evaluate its long-term safety and tolerability, KarXT belongs to a new class of antipsychotic medications that offers a different mechanism of action compared to traditional antipsychotics.

Investigated diseases

Schizophrenia - A complex mental disorder that affects how a person thinks, feels, and behaves. The condition typically appears in late teens or early adulthood and is characterized by a combination of hallucinations, delusions, and disorganized thinking. People with schizophrenia may experience periods where they have difficulty distinguishing between what is real and what isn't. The condition can also cause reduced emotional expression, decreased motivation, and difficulties with concentration and memory. Social withdrawal and changes in daily functioning are common features of this disorder.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-510773-20-00Protocol codeKAR-013Estimated enrolment272 patientsSponsorKaruna Therapeutics Inc.

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