Cysteamine
| 證據等級: L5 | 預測適應症: 10 個 |
目錄
- Cysteamine
- Cysteamine: From Nephropathic Cystinosis to Mitochondrial Oxidative Phosphorylation Disorder Due to Nuclear DNA Anomalies
Cysteamine: From Nephropathic Cystinosis to Mitochondrial Oxidative Phosphorylation Disorder Due to Nuclear DNA Anomalies
One-Sentence Summary
Cysteamine (β-mercaptoethylamine) is a small aminothiol globally approved for nephropathic cystinosis, where its free sulfhydryl group depletes lysosomal cystine accumulation via disulfide exchange — though it is not currently marketed in Canada. The TxGNN model’s top prediction assigns a 99.93% score for potential efficacy in Mitochondrial Oxidative Phosphorylation Disorder Due to Nuclear DNA Anomalies, based on theoretical antioxidant and autophagy-modulating mechanisms; however, no clinical trials and no supporting publications currently exist for this specific indication. Notably, the model independently re-identifies cysteamine’s established global uses at Ranks 2–3 (inborn disorder of lysosomal amino acid transport [L2] and ocular cystinosis [L1]), providing strong internal validation of the prediction framework and offering a separate, evidence-rich pathway for Canada market entry consideration.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Nephropathic cystinosis (globally approved under Cystagon® / Procysbi®; not marketed in Canada) |
| Predicted New Indication | Mitochondrial oxidative phosphorylation disorder due to nuclear DNA anomalies |
| TxGNN Prediction Score | 99.93% |
| Evidence Level | L5 |
| Canada Market Status | Not marketed |
| Number of DINs | 0 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Cysteamine contains a free sulfhydryl (-SH) group that is central to its pharmacological activity. In its approved indication (nephropathic cystinosis), cysteamine enters the lysosome and reacts with accumulated cystine through disulfide exchange, generating cysteine and a mixed cysteine–cysteamine disulfide. These products exit the lysosome via intact alternative transporters (LYAAT-1 and cationic amino acid transporters), effectively bypassing the defective cystinosin transporter and reducing toxic lysosomal cystine loads across all cell types. This mechanism of action is well-established and globally validated.
For mitochondrial oxidative phosphorylation (OXPHOS) disorders caused by nuclear DNA anomalies, the mechanistic rationale is indirect but biologically plausible. The free thiol group grants cysteamine antioxidant properties — specifically the capacity to scavenge reactive oxygen species (ROS) — which are chronically overproduced in OXPHOS-deficient cells due to impaired electron transport chain function. Additionally, published research indicates that cysteamine can modulate mTORC1 signalling and stimulate autophagy (including mitophagy), pathways that are centrally dysregulated in mitochondrial diseases where defective mitochondria accumulate and exacerbate cellular energy failure.
However, this mechanistic link remains firmly hypothetical. Cysteamine does not correct nuclear DNA mutations, does not restore electron transport complex enzyme activity, and has no validated direct target within the OXPHOS pathway. The high TxGNN score likely reflects shared network topology between lysosomal-mitochondrial pathway nodes in the knowledge graph, rather than a direct pharmacological relationship. In the complete absence of preclinical or clinical evidence, this prediction requires experimental validation before any development decision can be made.
Clinical Trial Evidence
No clinical trials are currently registered for cysteamine in mitochondrial oxidative phosphorylation disorder due to nuclear DNA anomalies.
Supplementary — Ocular Cystinosis (Rank 3, Evidence Level L1)
The following trials directly evaluate cysteamine in cystinosis and its ocular manifestations — the highest-evidenced predictions in this pack — included here as clinical context and Canada market entry reference.
| Trial Number | Phase | Status | Enrollment | Key Findings |
|---|---|---|---|---|
| NCT01197378 | Phase 3 | Completed | 60 | Long-term open-label safety and efficacy of RP103 (cysteamine bitartrate delayed-release) vs. immediate-release Cystagon® in nephropathic cystinosis; confirms twice-daily dosing non-inferiority and sustained cystine depletion |
| NCT01000961 | Phase 3 | Completed | 43 | Randomized crossover PK/PD study comparing RP103 and Cystagon® in nephropathic cystinosis; pivotal study supporting FDA approval of Procysbi® |
| NCT01744782 | Phase 3 | Completed | 17 | Long-term safety and effectiveness of RP103 in cysteamine treatment-naïve cystinosis patients; U.S. participants transitioned to commercially approved Procysbi® |
| NCT00010426 | N/A (Randomized) | Completed | 30 | Randomized study of topical cysteamine hydrochloride eye drops for corneal cystine crystal accumulation; assessed reduction in corneal crystal density of ≥1.00 unit |
| NCT00001736 | Phase 1 | Completed | 51 | Safety and efficacy of NDA-formulation topical cysteamine eye drops for corneal cystine crystals in cystinosis; foundational safety study for the topical ophthalmic route |
| NCT04125927 | Phase 3 | Completed | 5 | Safety of Cystadrops® (0.55% cysteamine eye drops) in pediatric cystinosis patients aged 6 months to under 2 years; supports EMA-approved label extension to younger age group |
| NCT05901077 | N/A (Observational) | Recruiting | 400 | European Cystinosis Cohort — large-scale real-world registry study of long-term cystinosis outcomes; cysteamine is the standard background therapy for all enrolled patients |
| NCT02012114 | N/A (Observational) | Completed | 65 | Observational cohort assessing relationship between cysteamine compliance and treatment efficacy, including ocular and neurological complication rates |
| NCT00872729 | Phase 1/2 | Completed | 9 | Pilot PK/PD study comparing RP103 and Cystagon® in nephropathic cystinosis; early pharmacokinetic foundation supporting the 12-hour dosing regimen |
| NCT02766855 | N/A | Completed | 26 | Observational efficacy study of topical cysteamine eye drops for corneal cystine crystal deposits in nephropathic cystinosis over a 12-year follow-up period |
Literature Evidence
No published literature is currently available for cysteamine in mitochondrial oxidative phosphorylation disorder due to nuclear DNA anomalies.
Supplementary — Ocular Cystinosis (Rank 3, Evidence Level L1)
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 33287176 | 2020 | Review | Pharmaceutics | Comprehensive review of drug delivery systems for ocular cystinosis; confirms cysteamine as the only topical treatment proven effective for corneal cystine crystal accumulation; reviews stability challenges for hospital pharmacy compounding |
| 40943162 | 2025 | Review | Int J Molecular Sciences | Molecular and clinical guidance on ocular manifestations of cystinosis; highlights that strict adherence to topical cysteamine is the only therapy that reduces corneal crystal accumulation; discusses emerging anti-inflammatory approaches |
| 30242621 | 2018 | Review | Ophthalmology and Therapy | Expert consensus from the Ophthalmology Cystinosis Forum; supports early diagnosis and initiation of topical cysteamine; discusses delayed diagnosis impact on prognosis |
| 11001803 | 2000 | Clinical Observational | Molecular Genetics and Metabolism | Natural history of corneal cystine crystal formation in nephropathic cystinosis using a validated scoring system; demonstrates measurable reduction in crystal density with cysteamine eye drops |
| 16603246 | 2006 | Clinical Observational | Ophthalmology | Retrospective study using the largest documented cohort worldwide; evaluates posterior segment ocular manifestations of nephropathic cystinosis and the protective effect of oral cysteamine therapy |
| 35028272 | 2022 | Clinical Study | JIMD Reports | Open-label prospective study of twice-daily delayed-release cysteamine capsules in cystinosis patients under 6 years; demonstrates control of leukocyte cystine levels and promotion of statural growth and kidney health |
| 30030899 | 2018 | Clinical Study/Case Series | Am J Transplantation | First human report that allogeneic HSCT transfers wild-type cystinosin to non-hematological epithelial cells in cystinosis; cysteamine used as standard background therapy; relevant for rank 2 (lysosomal amino acid transport disorder) |
| 35598215 | 2022 | Clinical Report | Orvosi Hetilap | Clinical report on cysteamine eye drop treatment for ocular cystinosis; describes photophobia reduction and quality of life improvement with consistent topical cysteamine use |
| 35791182 | 2022 | Case Report | Indian Journal of Ophthalmology | Case illustrating the consequences of non-adherence to topical cysteamine in infantile ocular cystinosis; outcome deteriorated with treatment interruption, underscoring compliance importance |
| 23946626 | 2013 | Regulatory Summary | P & T | Pharmaceutical approval update noting FDA approval of cysteamine bitartrate delayed-release capsules (Procysbi®) for nephropathic cystinosis in 2013; regulatory milestone reference |
Canada Market Information
Cysteamine is not currently marketed in Canada. No Drug Identification Numbers (DINs) are on record with Health Canada.
For reference, cysteamine is approved in major jurisdictions under the following products:
| Product | Route/Form | Indication | Jurisdiction |
|---|---|---|---|
| Cystagon® (cysteamine bitartrate, immediate-release) | Oral capsule | Nephropathic cystinosis | FDA (since 1994) |
| Procysbi® (cysteamine bitartrate, delayed-release) | Oral capsule | Nephropathic cystinosis | FDA (2013), EMA |
| Cystadrops® (cysteamine 0.55% ophthalmic solution) | Topical eye drops | Corneal cystine crystal accumulation in cystinosis | EMA (approved); pediatric label ≥6 months |
A Canada regulatory pathway (via the Orphan Drug and Rare Disease program) may be available, leveraging existing FDA/EMA approvals as reference.
Safety Considerations
Please refer to the package insert for safety information. Formal Health Canada label warnings and contraindications were not available in this Evidence Pack.
Based on published literature and global label information:
- Gastrointestinal effects: Nausea, vomiting, abdominal pain, and diarrhea are common and frequently dose-limiting, particularly on initiation; delayed-release formulations (Procysbi®) significantly reduce GI adverse effects compared to immediate-release Cystagon®
- Dermatological effects: Body odour, rash, and skin fragility have been reported with long-term use; collagen abnormalities (skin striae, joint hypermobility) are associated with chronic oral cysteamine therapy
- Ocular (topical formulation): Transient stinging, burning, and light sensitivity upon eye drop instillation are expected; proper instillation technique and compliance monitoring are essential
- Monitoring: Leukocyte cystine levels should be measured regularly (target: <1 nmol ½-cystine/mg protein) to confirm therapeutic adequacy; renal function, growth parameters, and thyroid function should be monitored in paediatric patients
Conclusion and Next Steps
Primary Prediction — Mitochondrial Oxidative Phosphorylation Disorder Due to Nuclear DNA Anomalies
Decision: Hold
Rationale: Despite a high TxGNN score (99.93%), the complete absence of preclinical studies, clinical trials, or published literature for cysteamine in OXPHOS disorders due to nuclear DNA anomalies means this prediction cannot currently be translated into a development programme. The mechanistic rationale — antioxidant ROS scavenging and autophagy modulation — is biologically plausible but unvalidated in this specific disease context.
To proceed, the following is needed:
- Preclinical studies (patient-derived fibroblast cell lines or CTNS-knockout/OXPHOS-deficient animal models) to determine whether cysteamine reduces ROS accumulation or improves mitochondrial membrane potential
- Mechanistic studies to evaluate whether cysteamine-induced autophagy/mitophagy activation is beneficial or potentially harmful in nuclear DNA-mediated OXPHOS disorders
- Expanded literature review covering thiol-based antioxidant strategies (e.g., N-acetylcysteine, glutathione precursors) in mitochondrial disease as mechanistic comparators
- Full MOA characterisation from DrugBank API (currently unavailable)
- Complete safety profile review from TFDA/Health Canada package insert
Supplementary Recommendation — Ocular Cystinosis (Rank 3)
Decision: Proceed with Guardrails
Rationale: Ocular cystinosis has the strongest evidence in this pack (L1: multiple completed Phase 3 trials; EMA-approved Cystadrops®; FDA-approved Procysbi®). For this indication, cysteamine already constitutes global standard of care. The primary unmet need in Canada is regulatory filing — no DINs exist despite established international approvals.
To proceed, the following is needed:
- File a New Drug Submission (NDS) with Health Canada referencing existing FDA (Procysbi® / Cystagon®) and EMA (Cystadrops®) approvals as regulatory anchors
- Confirm no Canadian patient access programmes currently exist (e.g., Special Access Programme) as interim measures
- Develop a post-market pharmacovigilance and patient registry plan given ultra-orphan disease status
- Identify Canadian cystinosis patient advocacy organisations and metabolic disease centres of excellence for partnership
- Assess pricing and reimbursement strategy for rare disease designation under CADTH / provincial formularies
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.