Hydroxyurea
| 證據等級: L5 | 預測適應症: 10 個 |
目錄
Hydroxyurea: From Sickle Cell Disease to Female Breast Carcinoma
One-Sentence Summary
Hydroxyurea is an established antineoplastic and disease-modifying agent, internationally approved for sickle cell disease and haematologic malignancies (including chronic myeloid leukaemia), but currently not registered in Australia with zero ARTG entries. The TxGNN model predicts it may be effective for Female Breast Carcinoma, with no registered clinical trials and 20 publications currently supporting this direction — though evidence is predominantly preclinical and from early-phase combination regimens where Hydroxyurea was not the primary agent.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Not registered in Australia; internationally established for sickle cell disease and haematologic malignancies (CML, polycythaemia vera) |
| Predicted New Indication | Female Breast Carcinoma |
| TxGNN Prediction Score | 99.97% |
| Evidence Level | L3 |
| Australia Market Status | Not marketed (no ARTG registration) |
| Number of ARTG Entries | 0 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data was not retrieved in this Evidence Pack. Based on established pharmacological knowledge, Hydroxyurea inhibits ribonucleotide reductase (RNR) — the enzyme responsible for converting ribonucleotides to deoxyribonucleotides, which is a rate-limiting step in DNA synthesis. This makes Hydroxyurea a cell-cycle S-phase–specific cytotoxic agent that selectively impairs rapidly dividing cells by depleting the deoxyribonucleotide pool and inducing replication fork stalling.
Female breast carcinoma is among the most proliferative solid malignancies, and the theoretical basis for RNR inhibition as an anti-tumour strategy is plausible. Historically, Hydroxyurea has been employed as a radiosensitiser and as a cell-cycle synchronisation agent in combination chemotherapy protocols for various solid tumours, including breast cancer (Phase I combination studies, 1990–1994). More recent mechanistic research has explored its role in modulating replication stress pathways — including EYA4-mediated replication stress avoidance in mammary tumours — as well as novel lipid–drug conjugate (LDC) formulations targeting the PI3K/AKT/mTOR pathway to improve cellular uptake in breast cancer cells.
However, Hydroxyurea’s precise position within modern breast cancer treatment frameworks remains undefined. Current standard-of-care regimens (CDK4/6 inhibitors, HER2-targeted agents, PARP inhibitors for BRCA-mutated disease, immunotherapy) are mechanistically distinct and clinically validated. The prediction likely reflects overlapping biological signals around DNA replication stress — a hallmark of aggressive breast cancer — rather than a direct, clinically proven therapeutic effect. The mechanistic link is scientifically credible but requires dedicated clinical evaluation.
Clinical Trial Evidence
Currently no related clinical trials registered for Hydroxyurea specifically in female breast carcinoma.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 7914447 | 1994 | Phase I/II Trial | Bone Marrow Transplantation | High-dose cyclophosphamide + thiotepa + hydroxyurea (18 g/m²) with autologous haematopoietic stem cell rescue in 26 women with responding metastatic breast cancer; demonstrated feasibility as consolidation chemotherapy |
| 1957839 | 1991 | Phase I Trial | American Journal of Clinical Oncology | Phase I dose-escalation study of allopurinol + 5-FU + leucovorin followed by hydroxyurea (HALF regimen) in 20 patients with advanced gastrointestinal and breast cancers; evaluated sequential biochemical modulation |
| 1733549 | 1992 | Phase I Trial | Cancer Chemotherapy and Pharmacology | Phase I study combining 5-FU, leucovorin, hydroxyurea, and escalating-dose continuous-infusion cisplatin with concurrent radiotherapy in advanced solid tumours; characterised hydroxyurea as a radiosensitiser |
| 2245491 | 1990 | Phase I Trial | Cancer Chemotherapy and Pharmacology | Pilot clinical translation of in vitro model: cisplatin preceded by concurrent cytarabine + hydroxyurea as DNA repair inhibitors in 40 patients with prior or no prior chemotherapy |
| 28837865 | 2017 | Preclinical | DNA Repair | Valproic acid (0.5 mM) sensitised multiple breast cancer cell lines to hydroxyurea by inhibiting RPA2 hyperphosphorylation-mediated DNA repair, inducing DNA double-strand breaks at safe concentrations |
| 32795962 | 2020 | Preclinical | DNA Repair | 2-hexyl-4-pentynoic acid (a lower-dose valproic acid analogue) sensitised breast carcinoma cells to hydroxyurea via the RPA2 hyperphosphorylation repair pathway, aiming to reduce valproic acid toxicity |
| 38211596 | 2024 | In-silico / Preclinical | Drug Research | In-silico design and development of hydroxyurea–lipid drug conjugates targeting PI3K/AKT/mTOR pathway; conjugation aimed to improve lipophilicity and cellular uptake to overcome hydroxyurea’s hydrophilic limitations in breast cancer |
| 34661718 | 2022 | Preclinical | Naunyn-Schmiedeberg’s Archives of Pharmacology | Hydroxyurea-loaded Fe₃O₄/SiO₂/chitosan-g-mPEG2000 magnetic nanoparticles demonstrated pH-dependent drug release, induced cell cycle arrest, and altered p53 and lincRNA-p21 expression in cancer cells |
| 37777742 | 2023 | Basic Research | Molecular Cancer | EYA4 promotes breast cancer progression and metastasis through replication stress avoidance; mammary tumour cells with EYA4 alterations showed heightened susceptibility to replicative DNA damage (hydroxyurea-modelled) |
| 21730979 | 2011 | Preclinical / Translational | British Journal of Cancer | ATR inhibitor NU6027 potentiated cisplatin independently of CDK2 in breast and ovarian cancer cell lines; hydroxyurea used as a reference replication stress inducer to characterise ATR pathway activity |
Australia Market Information
Hydroxyurea (DB01005) has no ARTG entries and is currently not registered in Australia under TGA regulation. There are no TGA-approved products or indications on record.
Clinicians seeking to access Hydroxyurea for Australian patients would need to explore the TGA Special Access Scheme (SAS) or Authorised Prescriber pathways, with reference to international product information (e.g., FDA-approved labelling, EMA SmPC).
Cytotoxicity
| Item | Content |
|---|---|
| Cytotoxicity Classification | Conventional cytotoxic — Ribonucleotide reductase (RNR) inhibitor / Hydroxamic acid class |
| Myelosuppression Risk | High — dose-dependent neutropenia, thrombocytopenia, and anaemia are the primary dose-limiting toxicities; myelosuppression is reversible upon dose reduction or cessation |
| Emetogenicity Classification | Low to moderate |
| Monitoring Items | Full blood count (FBC) with differential (at baseline, then weekly during dose titration, then monthly at stable dosing), renal function (eGFR/creatinine), liver function tests (LFTs), electrolytes |
| Handling Protection | Must be handled in accordance with cytotoxic drug handling regulations; capsules should not be opened; healthcare workers should wear appropriate PPE (gloves, gown, mask); cytotoxic waste disposal protocols apply |
Safety Considerations
No safety data (key warnings, contraindications, or drug–drug interactions) were retrieved from any queried source for this Evidence Pack. Hydroxyurea is not registered in Australia and therefore has no TGA-approved Product Information (PI).
Clinicians should consult:
- The FDA-approved prescribing information (Droxia®, Siklos®, Hydrea®) for full warnings and precautions
- The EMA Summary of Product Characteristics for European registration detail
- Published clinical guidelines from ASH (American Society of Hematology) or ESMO for cytotoxic monitoring and toxicity management
Conclusion and Next Steps
Decision: Hold
Rationale: While the TxGNN model assigns a high prediction score (99.97%) for Hydroxyurea in female breast carcinoma, no dedicated clinical trials exist for this indication, and the available published evidence is limited to early-phase combination regimens (where Hydroxyurea was an adjunct) and preclinical mechanistic studies. Without a clear differentiated clinical use case relative to modern breast cancer standard-of-care, and with no Australian registration or safety data on file, this indication cannot progress beyond a research question at this stage.
To proceed, the following is needed:
- MOA confirmation: Retrieve DrugBank API data to formally document the RNR inhibition mechanism and its relevance to breast cancer biology
- Safety package: Obtain and review FDA/EMA Product Information for key warnings, contraindications, and clinically relevant drug–drug interactions
- Clinical niche identification: Define a specific breast cancer subtype or treatment context where Hydroxyurea’s RNR inhibition or radiosensitisation mechanism offers a differentiated advantage (e.g., BRCA-mutated tumours with replication stress vulnerability, HER2+ radiotherapy combinations)
- Dedicated literature review: Systematic search for Hydroxyurea as a radiosensitiser specifically in breast radiotherapy protocols
- Prioritisation review: Consider whether the Rank 2–6 predicted indications (HbSC, HbSE, HbSD, HPFH-SCD, HbS-β-thal) represent higher-priority repurposing opportunities, given that multiple completed Phase 2/3 clinical trials already exist in those sickle cell disease subtypes
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.