CLOZAPINE Response in Biotype-1

May 7, 2026 updated by: Carol A. Tamminga, University of Texas Southwestern Medical Center

Antipsychotic Response to Clozapine in B-SNIP Biotype-1 (Clozapine)

The CLOZAPINE study is designed as a multisite study across 5 sites and is a clinical trial, involving human participants who are prospectively assigned to an intervention. The study will utilize a stringent randomized, double-blinded, parallel group clinical trial design. B2 group will serve as psychosis control with risperidone as medication control. The study is designed to evaluate effect of clozapine on the B1 participants, and the effect that will be evaluated is a biomedical outcome. The study sample will be comprised of individuals with psychosis, including 1) schizophrenia, 2) schizoaffective disorder and 3) psychotic bipolar I disorder. The investigators plan to initially screen and recruit n=524 (from both the existing B-SNIP library and newly-identified psychosis cases, ~50% each) in order to enroll n=320 (B1 and B2) into the RCT.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

The clinical hypotheses underlying this experiment are that (i) B1 individuals are uniquely responsive to the pharmacological properties of clozapine because they have low Intrinsic EEG Activity (IEA), an index of compromised cortical neuronal responsiveness. This is plausibly associated with both (ii) reduced excitatory and (iii) reduced inhibitory stimulation in cortex and that IEA will track this altered excitatory/inhibitory balance and parallel clinical antipsychotic response. Furthermore, (iv) B2 probands (based on their high IEA) will not respond to clozapine. In this study clozapine response is measured by a 'super-APD' (AntiPsychotic Drug) drug response, a response in addition to what is seen with a usual APD (e.g., risperidone). The investigators believe that the 30-35% of individuals who show a 'super-APD' clozapine response in schizophrenia in the pivotal study will be predominantly in B1, because the B1 completers will no longer be diluted by the other non-responders like B2s. Therefore, the investigators postulate that >50% of B1 will show a unique therapeutic action of clozapine (beyond general APD action), contrasted with the usual predicted response of B1 to risperidone or of B2 to clozapine or risperidone.

Study Type

Interventional

Enrollment (Estimated)

524

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 60 years (Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • 18-60y/o; males and females; all races and ethnicities; able to provide written informed consent; able to read, speak, and understand English; medically stable; meeting DSM-IV (SCID-based) criteria for schizophrenia, schizoaffective disorder, or bipolar I disorder with psychotic features (we will use DSM-IV to be consistent with prior B-SNIP samples); PANSS total score of ≥70 and at least one item scored ≥5 or two items scored ≥4 on PANSS Positive Subscale; normal baseline values for absolute neutrophil count (ANC above 1500/mm3)

Exclusion Criteria:

  • premorbid intellectual ability estimate below 70 (WRAT-4, Word Reading subtest, age-corrected standardized score); comorbid DSM-IV diagnosis of alcohol or substance abuse in prior 1 month or substance dependence in prior 3 months; neurological (e.g., seizure disorder, stroke, traumatic brain injury with a loss of consciousness ≥ 30min) or severe medical condition (e.g., decompensated cardiovascular disorder, AIDS) that may affect central nervous system function; concomitant medications known to affect EEG properties (i.e., lithium, anticonvulsants, benzodiazepines) or strong CYP 1A2 inhibitors (e.g., ciprofloxacin, enoxacin) or strong CYP 3A4 inducers (e.g., phenytoin, carbamazepine, phenobarbital, rifampin) which cannot be safely discontinued; vulnerable populations (e.g., pregnant, nursing, incarcerated); unwilling to use reliable means of contraception; history of neuroleptic malignant syndrome; prior treatment with clozapine, prior treatment with long-acting injectable antipsychotics that are 1-month formulations within the past 3 months and for 3-month formulations within the past 6 months; intolerable side effects to either clozapine or risperidone in lifetime, or a previously failed trial of either clozapine or risperidone at adequate doses in lifetime; history of drug reaction with eosinophilia and systemic symptoms syndrome (DRESS), also known as drug-induced hypersensitivity syndrome (DIHS); high risk for suicide defined as more than 1 attempt in past 12 months that required medical attention, any attempt in the past 3 months or current suicidal ideation with plan and intent such that outpatient care is precluded; current homicidal ideation with plan and intent such that outpatient care is precluded.

Study Plan

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

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Biotype 1 - Clozapine (B1C)
Target doses will be up to clozapine 500mg po qd. In addition, several concomitant (open label) medications for symptomatic management will be available via the study protocol [non-benzodiazepine sleep aid (melatonin, hydroxyzine); motor side effect treatments (benztropine, propranolol)]. The doses for these medications will be consistent with those routinely used in a clinical practice: melatonin [up to 10mg at bedtime], hydroxyzine [up to 100mg at bedtime]; benztropine [up to 4mg/day (2mg twice/day)], propranolol [up to 40mg/day (20mg twice/day)].
Drug: clozapine
Biotype 1 and Biotype 2
Other Names:
  • Clozaril
Placebo Comparator: Biotype 1 - Risperidone (B1R)
Target doses will be up to risperidone 6mg po qd. In addition, several concomitant (open label) medications for symptomatic management will be available via the study protocol [non-benzodiazepine sleep aid (melatonin, hydroxyzine); motor side effect treatments (benztropine, propranolol)]. The doses for these medications will be consistent with those routinely used in a clinical practice: melatonin [up to 10mg at bedtime], hydroxyzine [up to 100mg at bedtime]; benztropine [up to 4mg/day (2mg twice/day)], propranolol [up to 40mg/day (20mg twice/day)].
Drug: risperidone
Biotype 1 and Biotype 2
Other Names:
  • Risperdal
Active Comparator: Biotype 2 - Clozapine (B2C)
Target doses will be up to clozapine 500mg po qd. In addition, several concomitant (open label) medications for symptomatic management will be available via the study protocol [non-benzodiazepine sleep aid (melatonin, hydroxyzine); motor side effect treatments (benztropine, propranolol)]. The doses for these medications will be consistent with those routinely used in a clinical practice: melatonin [up to 10mg at bedtime], hydroxyzine [up to 100mg at bedtime]; benztropine [up to 4mg/day (2mg twice/day)], propranolol [up to 40mg/day (20mg twice/day)].
Drug: clozapine
Biotype 1 and Biotype 2
Other Names:
  • Clozaril
Placebo Comparator: Biotype 2 - Risperidone (B2R)
Target doses will be up to risperidone 6mg po qd. In addition, several concomitant (open label) medications for symptomatic management will be available via the study protocol [non-benzodiazepine sleep aid (melatonin, hydroxyzine); motor side effect treatments (benztropine, propranolol)]. The doses for these medications will be consistent with those routinely used in a clinical practice: melatonin [up to 10mg at bedtime], hydroxyzine [up to 100mg at bedtime]; benztropine [up to 4mg/day (2mg twice/day)], propranolol [up to 40mg/day (20mg twice/day
Drug: risperidone
Biotype 1 and Biotype 2
Other Names:
  • Risperdal

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in the PANSS total score
Time Frame: Week 4, Week 10 and Week 18
The change in the PANSS total score from the clinical trial baseline (W4) to the end of treatment (W18) will be a primary outcome measure. We predict that B1/clozapine will show a significantly larger change in the PANSS score from W4 to W18, compared to B1/risperidone, B2/clozapine and B2/risperidone. We will also examine the patterns of change in the PANSS score during the 'stable treatment' phase (W10-W18), across the same study groups. A mixed-effect repeated-measures ANCOVA [2(Biotypes) × 2(clozapine/risperidone) × 2(time points] will be used. We also predict that the reduction in the PANSS scores will correlate with increased IEA in B1/clozapine but not in B1/risperidone, B2/clozapine or B2/risperidone. Multivariate prediction models will be used.
Week 4, Week 10 and Week 18

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Texas Southwestern Medical Center

Collaborators

National Institute of Mental Health (NIMH)
Beth Israel Deaconess Medical Center
University of Chicago
University of Georgia
Hartford Hospital

Investigators

  • Principal Investigator: Carol Tamminga, M.D., University of Texas Southwestern Medical Center

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 1, 2022

Primary Completion (Estimated)

April 30, 2027

Study Completion (Estimated)

April 30, 2027

Study Registration Dates

First Submitted

October 1, 2020

First Submitted That Met QC Criteria

October 1, 2020

First Posted (Actual)

October 8, 2020

Study Record Updates

Last Update Posted (Actual)

May 11, 2026

Last Update Submitted That Met QC Criteria

May 7, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ( STU-2020-0989 )

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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