NCT04013555CompletedPhase 1/2
The Effects of Kynurenine Aminotransferase Inhibition in People With Schizophrenia
Source: ClinicalTrials.gov · Last updated 11 Feb 2026
Brief summary (registry, in English)
Kynurenic acid (KYNA) is a naturally occurring chemical in the brain. Studies with rodents indicate that levels of KYNA can impact levels of the neurotransmitters glutamate and dopamine. One way to reliably increase KYNA levels is by ingesting the amino acid tryptophan. Tryptophan is a normal part of the human diet. Tryptophan gets metabolized/changed to other chemicals in the body- including KYNA. By giving people 6 grams of tryptophan, the investigators will be able to increase the KYNA level in a controlled way. The investigators will then be able to study the effects of KYNA on neurotransmitters by using cognitive tests and magnetic resonance imaging techniques (measuring brain activity and brain chemistry using the MRI magnet). The overall goal of the study is to examine how the medication N-acetylcysteine (NAC), when added to tryptophan, affects various cognitive functions, such as verbal and visual memory. The investigators will also use magnetic resonance imaging (MRI) to examine how NAC affects brain activity and chemicals.
- Status (registry)
- Completed
- Phase (registry)
- Phase 1/2
- Study type
- Interventional
- Enrollment
- 88 (actual)
- First submitted
- 27 Jun 2019
- Start date
- 20 Jan 2020
- Primary completion date
- 14 Aug 2024
- Lead sponsor
- University of Maryland, Baltimore
- Diseases
- Schizophrenia
- NCT number
- NCT04013555
What you commit to
- Study type: Interventional · Phase 1/2
- Participants enrolled: 88
- From 20 Jan 2020 to the primary completion date, 14 Aug 2024
- 1 site in 1 country
- Visits and tests: ask the trial team, the registry does not list them
Built from the registry fields of ClinicalTrials.gov. It describes the study, not your situation.
Who cannot take part
Copied verbatim from ClinicalTrials.gov and grouped by topic. Only the trial team decides who can take part.
Prior treatment
- Monoamine oxidase inhibitors, migraine headache medications (triptans) and dextromethorphan
Other illness
- 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).
Other
- Excessive self-reported daily caffeine intake, defined as intake exceeding 1000mg or the equivalent of 8 cups of coffee
- Pregnancy or lactation
- No metal in body that will interfere with MR imaging
- Forensic or legal issues
Who the study is looking for
- 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)
- Female participants must agree to use a medically accepted means of contraception
Age in the registry: 18 years to 55 years · Sex: All · Does not accept healthy volunteers
Sites (1)
Sites in registry order. Pick your city on the disease page to sort them by distance.
| Site | City | Country | Site status |
|---|---|---|---|
| Maryland Psychiatric Research Center (MPRC) ; the Treatment Research Program (TRP) Coordinator of this site? Confirm its status | Catonsville | United States | Unknown status |
This page is information, not medical advice. Discuss any trial with your doctor.