Hydroxyurea
| 證據等級: L5 | 預測適應症: 10 個 |
目錄
Hydroxyurea: From Sickle Cell Disease & Leukemia to Female Breast Carcinoma
One-Sentence Summary
Hydroxyurea is a well-established antineoplastic and disease-modifying agent used internationally for sickle cell disease, chronic myeloid leukemia, and other myeloproliferative disorders, though it currently holds no product registration in Singapore. The TxGNN model predicts it may be effective for Female Breast Carcinoma with a confidence score of 99.97%, with 0 registered clinical trials and 20 publications currently available — the latter consisting primarily of Phase I combination studies from the 1990s and recent preclinical research rather than breast-cancer-specific efficacy trials.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Sickle cell disease, chronic myeloid leukemia, and myeloproliferative disorders (not registered in Singapore) |
| Predicted New Indication | Female Breast Carcinoma |
| TxGNN Prediction Score | 99.97% |
| Evidence Level | L3 |
| Singapore Market Status | ✗ Not Marketed |
| Number of Registrations | 0 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Currently, detailed mechanism of action data is not available in this evidence pack. Based on established pharmacology, Hydroxyurea (HU) is a ribonucleotide reductase (RNR) inhibitor — it blocks the conversion of ribonucleotides to deoxyribonucleotides, the rate-limiting step in DNA synthesis, causing cells to arrest in the S-phase of the cell cycle. This mechanism is broadly cytotoxic to rapidly dividing cells, making it theoretically applicable to many tumour types including breast cancer.
The biological rationale for HU in breast cancer rests on two intersecting mechanisms: (1) direct RNR inhibition to arrest breast tumour cell proliferation, particularly relevant in hormone-independent, rapidly cycling subtypes; and (2) sensitisation of cancer cells to DNA-damaging agents by impairing the DNA repair response. Early Phase I clinical studies from the late 1980s and early 1990s included breast cancer patients in combination regimens with 5-fluorouracil, leucovorin, and cisplatin, and one Phase I/II trial specifically enrolled 26 metastatic breast cancer patients for high-dose HU with haematopoietic stem cell rescue. More recent preclinical work has explored HU sensitisation via the RPA2 hyperphosphorylation–DNA repair axis (in combination with valproic acid) and novel lipid conjugate or nanoparticle delivery systems targeting the PI3K/AKT/mTOR pathway.
However, the critical evidence gap is the complete absence of any Phase 2 or Phase 3 trial evaluating HU specifically in breast cancer as either a single agent or a defined combination. All existing clinical data comes from small Phase I studies treating heterogeneous solid tumour populations where breast cancer patients were a minority. The TxGNN prediction is mechanistically plausible, but the current evidence base supports a hypothesis-generating signal rather than an actionable clinical development path.
Clinical Trial Evidence
Currently no related clinical trials registered for Hydroxyurea in female breast carcinoma.
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 7914447 | 1994 | Phase I/II (high-dose + stem cell rescue) | Bone Marrow Transplantation | 26 metastatic breast cancer women responding to prior chemotherapy received HU 18 g/m² combined with cyclophosphamide (6 g/m²) + thiotepa (600 mg/m²) with stem cell rescue; reported as effective consolidation chemotherapy |
| 1957839 | 1991 | Phase I RCT (combination) | Am J Clin Oncol | 20 patients with advanced colorectal, pancreatic, gastric, and breast cancer enrolled in HALF regimen (5-FU + leucovorin → HU + allopurinol); dose escalation and tolerability assessed |
| 2245491 | 1990 | Pilot / In vitro–guided clinical | Cancer Chemother Pharmacol | Cisplatin preceded by concurrent cytarabine + HU in 40 patients (mixed solid tumours); design based on in vitro synergy model showing HU inhibits cisplatin-damaged DNA repair in colon cancer cells |
| 1733549 | 1992 | Phase I/II (combination + RT) | Cancer Chemother Pharmacol | Escalating cisplatin added to 5-FU + HU + concomitant radiotherapy in advanced solid tumours; established HU as radiation sensitiser in multi-drug palliative setting |
| 28837865 | 2017 | Preclinical (cell line) | DNA Repair | Valproic acid (0.5 mM) sensitises multiple breast cancer cell lines to HU (2 mM) by blocking RPA2 hyperphosphorylation-mediated DNA double-strand break repair; mechanistic sensitisation study |
| 32795962 | 2020 | Preclinical | DNA Repair | 2-hexyl-4-pentynoic acid investigated as alternative sensitiser to HU in breast carcinoma cells via the RPA2 hyperphosphorylation-DNA repair axis; addresses valproic acid dose limitations |
| 38211596 | 2024 | In-silico / Computational | Drug Research | Novel HU lipid drug conjugates designed in silico to increase lipophilicity and cellular uptake; targets PI3K/AKT/mTOR pathway in breast cancer; no in vivo data available |
| 34661718 | 2022 | Preclinical (nanoparticle) | Naunyn-Schmiedeberg's Arch Pharmacol | HU loaded into Fe₃O₄/SiO₂/chitosan-g-mPEG2000 magnetic nanoparticles; pH-dependent release demonstrated; cell cycle arrest and altered p53/lincRNA-p21 expression in cancer cell lines |
| 21730979 | 2011 | Preclinical (cell line) | Br J Cancer | ATR inhibitor NU6027 potentiates cisplatin in breast and ovarian cancer cell lines; HU used as replication stress inducer to characterise ATR-dependent checkpoint signalling |
| 30159181 | 2018 | Case Report | Case Rep Hematol | 65-year-old woman with JAK2+ essential thrombocythemia concurrent with hormone-positive, HER2-negative invasive ductal carcinoma; HU used for thrombocythemia management during breast cancer treatment; reports clinical management challenges of dual diagnoses |
Singapore Market Information
Hydroxyurea is currently not registered in Singapore. There are no active product authorizations on record (total registrations: 0). Clinicians wishing to use this agent would need to apply through the Health Sciences Authority (HSA) special access pathway for unregistered medicines.
Cytotoxicity
Hydroxyurea qualifies as an antineoplastic agent (ribonucleotide reductase inhibitor; conventional cytotoxic class). Its original clinical use includes treatment of leukaemia and myeloproliferative disorders.
| Item | Content |
|---|---|
| Cytotoxicity Classification | Conventional cytotoxic — Ribonucleotide reductase inhibitor (distinct from alkylating agents, antimetabolites, or taxanes) |
| Myelosuppression Risk | High — bone marrow suppression is the primary dose-limiting toxicity; neutropenia, thrombocytopenia, and macrocytic anaemia are common and dose-dependent |
| Emetogenicity Classification | Low to moderate |
| Monitoring Items | Complete blood count (CBC with differential) at baseline and regularly during therapy; renal function (serum creatinine, eGFR) — HU is primarily renally excreted and dose adjustment required in renal impairment; platelet nadir monitoring in high-dose regimens |
| Handling Protection | Must follow cytotoxic drug handling regulations; capsule formulations should not be opened or crushed without appropriate PPE; pregnant healthcare workers should avoid direct contact |
Safety Considerations
Please refer to the package insert for safety information. Singapore package insert data (TFDA warnings and contraindications) has been identified as a blocking data gap in this evidence pack and must be retrieved before any clinical decision-making. No drug-drug interaction data was found in this search.
Conclusion and Next Steps
Decision: Hold
Rationale: All existing clinical evidence for Hydroxyurea in female breast carcinoma consists of Phase I combination regimens from over 30 years ago where breast cancer patients were a minority subgroup, supplemented by recent preclinical and computational studies. There are no Phase 2 or Phase 3 trials, no registered active trials, and no regulatory precedent for this indication. The mechanistic rationale is plausible but not sufficiently differentiated from established standard-of-care agents to justify clinical development without foundational studies.
To proceed, the following is needed:
- Safety baseline: Retrieve TFDA/international package insert for key warnings and contraindications (currently a blocking data gap)
- MOA documentation: Obtain full mechanism of action profile from DrugBank to strengthen mechanistic argument for breast cancer subtypes
- Biomarker hypothesis: Identify which breast cancer subtype (HR+, HER2+, or TNBC) is most likely to respond based on RNR expression or DNA repair pathway dependence
- Preclinical proof-of-concept: Conduct in vitro and in vivo studies with HU as monotherapy or in a defined targeted combination (e.g., HU + PARP inhibitor or HU + anti-HER2) in breast cancer models
- Evidence upgrade: If preclinical data is promising, design a Phase 1b/2 biomarker-stratified basket trial; the high-dose stem cell rescue data from 1994 (PMID 7914447) may provide historical dosing reference but is not suitable as modern comparator evidence
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.