Clozapine
| Evidence Level: L2 | Predicted Indications: 10 |
Table of Contents
Clozapine: From Treatment-Resistant Schizophrenia to Manic Bipolar Affective Disorder
One-Sentence Summary
Clozapine is an atypical antipsychotic, marketed in the US as generic tablets and orally disintegrating tablets. The license data do not list an indication, but the evidence pack ties its established use to treatment-resistant schizophrenia. The TxGNN model predicts it may be effective for manic bipolar affective disorder, with 6 registered clinical trials and 20 publications retrieved. Only one trial is a direct clozapine efficacy study (Phase 2, double-blind, completed).
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not stated in the US license data. The evidence pack points to treatment-resistant schizophrenia |
| Predicted New Indication | Manic bipolar affective disorder |
| TxGNN Prediction Score | 99.95% |
| Evidence Level | L2 |
| US Market Status | ✓ Marketed |
| Number of NDAs | 20 (listed licenses are ANDA generics) |
| Recommended Decision | Proceed with Guardrails |
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available in the source record. Based on general pharmacology, clozapine blocks dopamine D2 and serotonin 5-HT2A receptors and also acts on muscarinic, adrenergic and histaminergic receptors. This broad profile underlies its established superiority in treatment-resistant schizophrenia.
Treatment-resistant mania and schizophrenia are both severe psychiatric illnesses in which first-line agents often fail. Clozapine’s receptor profile plausibly supports antimanic effects and the reported reduction in suicidality in refractory illness.
Support comes from a 2020 systematic review and meta-analysis of clozapine in bipolar disorder, a 2015 systematic review in treatment-resistant bipolar disorder, and a completed Phase 2 double-blind trial in treatment-resistant mania. No randomized outcome data are included in the pack, so the evidence is promising but not definitive.
Clinical Trial Evidence
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT00029458 | Phase 2 | Completed | 42 | Double-blind study of clozapine efficacy and pathophysiology in treatment-resistant mania. Outcome data are not in the pack |
| NCT07047651 | Phase 4 | Recruiting | 40 | Pharmacotherapy plus a recovery-oriented programme for treatment-resistant bipolar disorder. The psychosocial component confounds any clozapine effect |
| NCT05603104 | Phase 3 | Recruiting | 1254 | Intensified pharmacological treatment after first-line failure in schizophrenia, major depression and bipolar depression. Clozapine’s role is unclear |
| NCT06993662 | Phase 1 | Active, not recruiting | 107 | Pharmacotherapy combined with cognitive behavioural therapy. Not specific to clozapine |
| NCT03651674 | N/A | Unknown | 200 | MRI study of electroconvulsive therapy in schizophrenia and bipolar disorder. Indirect link only |
| NCT07398365 | N/A | Recruiting | 100 | Observational phenotyping of psychiatric inpatients. No clozapine efficacy question |
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 32182485 | 2020 | Systematic review / meta-analysis | J Psychiatr Res | Assesses clozapine’s clinical efficacy and adverse-effect profile in bipolar disorder |
| 25346322 | 2015 | Systematic review | Bipolar Disord | Evaluates efficacy and safety of clozapine in treatment-resistant bipolar disorder |
| 33719158 | 2021 | Review | Bipolar Disord | Summarizes what is known about clozapine in bipolar disorder and future research needs |
| 33460070 | 2020 | Review | Acta Psychiatr Scand | Evidence-based options for managing a manic episode, including choice of mood stabilizer and antipsychotic |
| 16432528 | 2006 | Review | Mol Psychiatry | Treatment-resistant bipolar disorder: first-line agents and options after inadequate response |
| 11280956 | 2001 | Review | Bull Menninger Clin | Newer treatments for bipolar disorder rest mostly on case reports and case series |
| 31488793 | 2019 | Review / commentary | Psychiatr Danub | Clozapine as a promising treatment for suicidality in bipolar disorder |
| 37068038 | 2023 | Prescribing-pattern study | J Clin Psychopharmacol | Asian consortium study of clozapine use for bipolar disorder |
| 40174308 | 2025 | Retrospective cohort | J Psychiatr Res | Nationwide Korean study of anti-suicidal effectiveness of clozapine, lithium and valproate |
| 31567198 | 2021 | Retrospective cohort | Am J Ther | Rapid clozapine titration in schizophrenia and bipolar disorder |
US Market Information
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| ANDA206433 | Clozapine (American Health Packaging) | Tablet | Not listed in the source data |
| ANDA201824 | Clozapine (Mylan Pharmaceuticals Inc.) | Tablet, orally disintegrating | Not listed in the source data |
| ANDA090308 | Clozapine (Teva Pharmaceuticals USA, Inc.) | Tablet, orally disintegrating | Not listed in the source data |
| ANDA201824 | Clozapine (Mylan Institutional Inc.) | Tablet, orally disintegrating | Not listed in the source data |
| ANDA090308 | Clozapine (Teva Pharmaceuticals USA, Inc.) | Tablet, orally disintegrating | Not listed in the source data |
A suspension formulation is also recorded under the “Other” route.
Safety Considerations
Please refer to the package insert for safety information.
Conclusion and Next Steps
Decision: Proceed with Guardrails
Rationale: Clozapine is already marketed, and the pack scores this indication L2. A completed Phase 2 double-blind trial and systematic reviews and meta-analyses support use in treatment-refractory mania. No completed Phase 3 evidence for mania is in the pack, and clozapine carries serious known risks, so any further work should be limited to treatment-refractory patients.
To proceed, the following is needed:
- Package insert warnings and contraindications (a blocking data gap), obtained from the FDA label
- Detailed mechanism of action data from DrugBank
- Outcome data from NCT00029458 and from the Phase 4 randomized comparison NCT02562287, whose status is unknown
- Safety guardrails in any protocol: mandatory absolute neutrophil count (ANC) monitoring for agranulocytosis, and surveillance for myocarditis, seizures, metabolic effects and constipation
- Confirmation of the approved indication text for the US licenses
This report is for research reference only and does not constitute medical advice. Repurposing candidates require clinical validation before any application.
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.