Completed

TrypNAC-IIEffects of Kynurenine Aminotransferase Inhibition on Brain Chemistry, Function, and Behavior in Schizophrenia

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Study Aim

This study aims to evaluate if N-acetylcysteine (NAC) can block the conversion of kynurenine to kynurenic acid in individuals with schizophrenia, and how this affects brain chemistry, function, and behavior.

What is being tested

N-acetylcysteine (NAC)

+ Tryptophan

+ Placebo

Drug
Who is being recruted

Mental Disorders+1

+ Psychotic Disorders

+ Schizophrenia

From 18 to 55 Years
+13 Eligibility Criteria
See all eligibility criteria
How is the trial designed

Other Study

Placebo-ControlledPhase 1 & 2
Interventional
Study Start: January 2020
See protocol details

Summary

Principal SponsorUniversity of Maryland, Baltimore
Last updated: February 12, 2026
Sourced from a government-validated database.Claim as a partner

Study start date: January 20, 2020

Actual date on which the first participant was enrolled.

This clinical trial aims to understand if a high dose of N-acetylcysteine (NAC) can counteract the negative effects of increased kynurenic acid (KYNA) on brain chemistry, function, and behavior in people with schizophrenia. KYNA is produced when an enzyme called kynurenine aminotransferase (KAT) II converts kynurenine. The study is important as it could potentially lead to the development of new treatments to improve cognition in individuals with schizophrenia. Participants in this study, who have schizophrenia, will be given either high-dose NAC or a placebo, followed by tryptophan (TRYP). The study will measure the levels of kynurenine and KYNA in the blood before and after the treatment to see if NAC can block the conversion of kynurenine to KYNA. The study will also use non-invasive imaging techniques like arterial spin labeling (ASL), magnetic resonance spectroscopy (MRS), and diffusion tensor imaging (DTI) to measure brain function and structure before and after the treatment. The study hopes to find that NAC can improve brain function and structure, and that these improvements are related to better cognitive performance.

Official TitleThe Effects of Kynurenine Aminotransferase Inhibition in People With Schizophrenia
NCT04013555
Principal SponsorUniversity of Maryland, Baltimore
Last updated: February 12, 2026
Sourced from a government-validated database.Claim as a partner

Protocol

This section provides details of the study plan, including how the study is designed and what the study is measuring.
Design Details

88 patients to be enrolled

Total number of participants that the clinical trial aims to recruit.

Other Study

Some studies explore topics that don't fall into a specific category. These might include innovative research, new technologies, or emerging healthcare areas.

Eligibility

Researchers look for people who fit a certain description, called eligibility criteria: person's general health condition or prior treatments.
Conditions
Criteria

Any sex

Biological sex of participants that are eligible to enroll.

From 18 to 55 Years

Range of ages for which participants are eligible to join.

Healthy volunteers not allowed

If individuals who are healthy and do not have the condition being studied can participate.

Conditions

Pathology

Mental DisordersPsychotic DisordersSchizophreniaSchizophrenia Spectrum and Other Psychotic Disorders

Criteria

5 inclusion criteria required to participate
Males and females
Age: 18 to 55 years
DSM-5 Criteria for schizophrenia, schizoaffective disorder or schizophreniform disorder (documented by SCID)
Prescription of antipsychotic medication for at least 60 days and constant dose for 30 days prior to study entry (either first or second generation antipsychotics permitted)
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8 exclusion criteria prevent from participating
DSM-5 alcohol or substance misuse disorder in the last 3 months (documented by SCID)
History of an organic brain disorder; mental retardation; or a medical condition, whose pathology or treatment could alter cognition
Active disorders that have been reported to affect tryptophan metabolism or interfere with absorption will be excluded (Acute Intermittent Porphyria, Celiac Disease, Crohn's Disease, Irritable Bowel Syndrome; Brune and Pflughaupt 1975; Torres et al 2007).
Excessive self-reported daily caffeine intake, defined as intake exceeding 1000mg or the equivalent of 8 cups of coffee
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Study Plan

Find out more about all the medication administered in this study, their detailed description and what they involve.
Treatment Groups
Study Objectives

2 intervention groups are designated in this study

50% chance of being blinded to the placebo group

Treatment Groups

Group I

Experimental
N-acetylcysteine 140 mg/kg up to a maximum of 15 g. Thirty minutes after N-acetylcysteine administration participants will receive Tryptophan, 6 grams.

Group II

Placebo
Placebo 140 mg/kg up to a maximum of 15 g. Thirty minutes after placebo administration participants will receive Tryptophan, 6 grams.

Study Objectives

Primary Objectives

Study Centers

These are the hospitals, clinics, or research facilities where the trial is being conducted. You can find the location closest to you and its status.

This study has 1 location

Suspended

Maryland Psychiatric Research Center (MPRC) ; the Treatment Research Program (TRP)

Catonsville, United StatesOpen Maryland Psychiatric Research Center (MPRC) ; the Treatment Research Program (TRP) in Google Maps
CompletedOne Study Center