Clozapine-related Immunodeficiency in Parkinsons Disease

Assessment of Clozapine-related Immunodeficiency Effect in Parkinsons Disease Patients

Clozapine-related Immunodeficiency in Parkinsons Disease (NCT06634641) is a Phase 4 interventional studying Clozapine and Parkinson's Disease (PD), sponsored by Centre Hospitalier Universitaire, Amiens. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

About This Trial

Clozapine is a second generation antipsychotic drug used in psychiatry to treat schizophrenia, affective disorders or certain symptoms of dementia. In neurology, clozapine is frequently used and recommended to manage symptoms of psychosis associated with Parkinson's disease (PD). The risk of neutropenia or agranulocytosis associated with clozapine estimated at 1.3% is well known to doctors around the world with a peak at one month and a decrease in risk after more than a year of treatment. This risk has led to the policy of "no blood, no drugs" and monitoring of the complete blood count (CBC) weekly for 18 weeks and then monthly for the duration of treatment. Some studies suggest an increased risk of infections related to immunodeficiency induced by clozapine itself. This clozapine-induced immunodeficiency would be comparable to that encountered in patients with common variable immunodeficiency or under immunosuppressive treatment. In addition, this immunosuppressive effect linked to clozapine would not be dose dependent but time dependent. However, the only studies currently performed have been in psychiatric patients treated for schizophrenia. It seems important to specifically explore clozapine-related immunodeficiency in PD patients treated with clozapine for PD-related psychosis. In this study, the investigators propose to evaluate the variations in serum immunoglobulin levels and lymphocyte subpopulations (B, T, NK) in parkinsonian patients treated with Clozapine at 6 months and 1 year after initiation of treatment.

What Stage of Research Is This?

Phase 4 studies happen after a treatment has been approved by the FDA. They monitor long-term safety, real-world effectiveness, and any rare side effects that only emerge in larger populations over longer periods. Phase 4 results sometimes lead to label changes, additional warnings, or — rarely — withdrawal of approval.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

With a target enrollment of 24 participants, this is a small study — typical of early-phase research, rare-disease trials, or pilot studies designed to generate preliminary signal before a larger study is launched.

Who May Be Eligible (Plain English)

Who May Qualify: - Patient ≥ 18 years old with Parkinson's disease according to MDS 2015 criteria - Psychotic symptoms requiring treatment with Clozapine - Patients with initially a normal leukocyte count (number of white blood cells ≥ 3500/mm3 \[3.5 x 109/l\] and an absolute neutrophil count PNN ≥ 2000/mm3 \[2 x 109/l\]) - patients in whom the number of white blood cells (WBC) and the absolute number of neutrophils (PNN) may be determined regularly at the following intervals: once a week during the first 18 weeks of treatment and, thereafter, at least every 4 weeks for the duration of the treatment. This monitoring must be continued throughout the treatment and for 4 weeks who follow the complete cessation of CLOZAPINE - Informed and written consent. - Affiliation to a social security system Who Should NOT Join This Trial: - Patients with a contraindication to the use of Clozapine according to the summary of product characteristics (SPC) - Hypersensitivity to the active substance or to any of the excipients. - Patients who cannot receive regular blood tests. - History of granulopenia or toxic or idiosyncratic agranulocytosis (unless it results from previous chemotherapy). - History of agranulocytosis induced by CLOZAPINE - Treatment with CLOZAPINE should not be started at the same time as substances known to have a high potential for inducing agranulocytosis; The concomitant administration of depot antipsychotics is not recommended. - Functional bone marrow failure. - Uncontrolled epilepsy. - Alcoholic or induced psychosis, drug intoxication, comatose states. - Circulatory collapse and / or CNS depression regardless of the aetiology. - Severe renal or cardiac disorders (eg: myocarditis). - Active liver disease with nausea, anorexia or jaundice; progressive liver disease, liver failure. - Paralytic ileus. - Patient with another potential cause of immunosuppression - Immunosuppressive or immune modulatory treatment active or stopped for less than 5 years ...See full criteria on ClinicalTrials.gov Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language

Inclusion Criteria: * Patient ≥ 18 years old with Parkinson's disease according to MDS 2015 criteria * Psychotic symptoms requiring treatment with Clozapine * Patients with initially a normal leukocyte count (number of white blood cells ≥ 3500/mm3 \[3.5 x 109/l\] and an absolute neutrophil count PNN ≥ 2000/mm3 \[2 x 109/l\]) * patients in whom the number of white blood cells (WBC) and the absolute number of neutrophils (PNN) may be determined regularly at the following intervals: once a week during the first 18 weeks of treatment and, thereafter, at least every 4 weeks for the duration of the treatment. This monitoring must be continued throughout the treatment and for 4 weeks who follow the complete cessation of CLOZAPINE * Informed and written consent. * Affiliation to a social security system Exclusion Criteria: * Patients with a contraindication to the use of Clozapine according to the summary of product characteristics (SPC) * Hypersensitivity to the active substance or to any of the excipients. * Patients who cannot receive regular blood tests. * History of granulopenia or toxic or idiosyncratic agranulocytosis (unless it results from previous chemotherapy). * History of agranulocytosis induced by CLOZAPINE * Treatment with CLOZAPINE should not be started at the same time as substances known to have a high potential for inducing agranulocytosis; The concomitant administration of depot antipsychotics is not recommended. * Functional bone marrow failure. * Uncontrolled epilepsy. * Alcoholic or induced psychosis, drug intoxication, comatose states. * Circulatory collapse and / or CNS depression regardless of the aetiology. * Severe renal or cardiac disorders (eg: myocarditis). * Active liver disease with nausea, anorexia or jaundice; progressive liver disease, liver failure. * Paralytic ileus. * Patient with another potential cause of immunosuppression * Immunosuppressive or immune modulatory treatment active or stopped for less than 5 years * Anti-epileptic treatment active or stopped for less than 5 years * Chemotherapy active or stopped for less than 5 years * Solid or hematologic cancer active or treated for less than 5 years * Human immunodeficiency virus infection * Already known constitutional immune deficiency * Nephrotic syndrome * Protein-losing enteropathy * A history of radiotherapy * Long-term use of corticosteroids * Patient with potentially major cognitive disorders defined by a MoCA score less than or equal to 23 * Pregnant or breastfeeding women * Patient under guardianship/curatorship or deprived of liberty

Treatments Being Tested

BIOLOGICAL

blood test

Only carrying out additional immunological assays during blood tests before initiation of treatment, six months after initiation of treatment and then one year after initiation of treatment.

Locations (1)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

CHU Amiens-Picardie

Salouël, France

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT06634641), the sponsor (Centre Hospitalier Universitaire, Amiens), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT06634641 clinical trial studying?

Who can participate in NCT06634641?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT06634641?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT06634641. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT06634641. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-05-08 · Data from ClinicalTrials.gov.