Mercaptopurine

證據等級: L5

預測適應症: 10 個

Mercaptopurine: From Acute Lymphoblastic Leukemia to Myeloid Leukemia

One-Sentence Summary

Mercaptopurine (6-MP) is a purine antimetabolite whose established use — evident throughout the accompanying literature and trial evidence in this pack — is as the backbone of acute lymphoblastic leukemia (ALL) maintenance therapy. The TxGNN model's top-ranked prediction is Myeloid Leukemia, with 29 clinical trials and 20 publications currently supporting this direction, though closer review shows this largely reflects mercaptopurine's already-documented historical role in acute promyelocytic leukemia (APL) maintenance rather than a wholly novel mechanism.

Note on original indication: The structured regulatory field for original indication was not populated in this evidence pack (data gap). The "Acute Lymphoblastic Leukemia" reference above is derived from repeated context within the supplied clinical trial and literature evidence (e.g., mercaptopurine + methotrexate maintenance regimens), not from an external source.

Quick Overview

Item	Content
Original Indication	Not available in structured regulatory data; extensively referenced in evidence as Acute Lymphoblastic Leukemia (ALL) maintenance therapy
Predicted New Indication	Myeloid Leukemia
TxGNN Prediction Score	99.94%
Evidence Level	L1
New Zealand Market Status	✗ Not Marketed
Number of Authorizations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available (data gap). Based on known information, mercaptopurine is a thiopurine/purine antimetabolite; its efficacy as part of maintenance chemotherapy for acute lymphoblastic leukemia has been well established in the literature included in this pack, and mechanistically the same antiproliferative pathway — conversion to thioguanine nucleotides, incorporation into DNA/RNA, and inhibition of de novo purine synthesis — is not lineage-specific, making applicability to myeloid malignancies biologically plausible.

Importantly, the supporting evidence indicates this is less a "new" hypothesis than a validated extension of existing practice: multiple Phase 3/Phase 4 trials (e.g., AIDA, AIDA2000, PETHEMA LPA2005) already incorporate 6-mercaptopurine, alongside ATRA and methotrexate, as standard post-remission maintenance therapy for acute promyelocytic leukemia (APL), a recognized subtype of acute myeloid leukemia. The repurposing rationale attached to this prediction explicitly frames it as a "standard/historical regimen" for AML (particularly APL) maintenance rather than a novel repurposing hypothesis. This strengthens confidence in the signal but also means the primary value of pursuing this indication is regulatory/label formalization rather than discovery of new biological activity.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT00492856	Phase 3	Completed	105	S0521 RCT directly comparing 6-MP + methotrexate maintenance vs. observation in low/intermediate-risk APL
NCT00136084	Phase 3	Completed	238	Collaborative trial for newly diagnosed AML/MDS comparing two multi-agent chemotherapy regimens
NCT06199557	Phase 1/2	Recruiting	48	Hydroxyurea + valproic acid, or 6-MP + valproic acid, in AML/high-risk MDS patients unfit for standard therapy
NCT00003934	Phase 3	Completed	420	Tretinoin ± arsenic trioxide consolidation followed by maintenance with intermittent tretinoin plus mercaptopurine/methotrexate in untreated APL
NCT00180128	Phase 4	Unknown	80	AIDA2000 risk-adapted APL therapy; maintenance includes 2-year course of 6-MP, methotrexate, and ATRA
NCT00465933	Phase 4	Completed	N/A	AIDA induction with risk-adapted consolidation; ATRA + methotrexate + mercaptopurine salvage for relapse
NCT00408278	Phase 4	Completed	300	PETHEMA LPA2005: risk-adapted APL therapy with maintenance of ATRA plus low-dose methotrexate/mercaptopurine
NCT00482833	Phase 3	Completed	276	Arsenic trioxide + ATRA vs. standard ATRA/anthracycline (AIDA) in newly diagnosed non-high-risk APL
NCT02688140	Phase 3	Completed	135	Arsenic trioxide + ATRA + idarubicin vs. AIDA regimen in newly diagnosed high-risk APL
NCT00962767	Phase 3	Completed	168	Gemtuzumab ozogamicin vs. 2-year ATRA + chemotherapy maintenance in intermediate/high-risk APL

Literature Evidence

PMID	Year	Type	Journal	Key Findings
10497848	1999	RCT	International Journal of Hematology	JALSG-AML92: adding etoposide to daunorubicin/cytarabine/6-mercaptopurine induction showed no additional benefit in adult AML
8174198	1994	RCT	Cancer Chemotherapy and Pharmacology	Nationwide randomized comparison of daunorubicin vs. aclarubicin combined with cytarabine, 6-mercaptopurine, and prednisolone in untreated AML
26425037	2015	Cohort	Journal of Korean Medical Science	Oral maintenance with 6-MP and methotrexate in transplant-ineligible AML patients after first complete remission
9095207	1997	Cohort	Cancer Investigation	High-dose continuous 6-MP followed by intermediate-dose cytarabine as first-remission consolidation in pediatric AML
1793832	1991	—	International Journal of Hematology	Intensive individualized induction with behenoyl cytarabine, daunorubicin, and 6-MP in adult AML (71% CR rate)
1657335	1991	—	Chinese Medical Journal	Cytarabine + daunorubicin + 6-mercaptopurine combination induction/consolidation in adult AML
1059498	1975	—	Cancer	Cytarabine, daunorubicin, prednisolone, and mercaptopurine or thioguanine in childhood AML; 78% remission rate
4518586	1973	—	Cancer	Cytosine arabinoside combined with 6-mercaptopurine in adult AML
5220682	1966	Case Series	Minnesota Medicine	Early case series of AML treated with 6-mercaptopurine and cyclophosphamide
13930127	1963	—	Blood	Comparison of remission patterns in acute myelocytic leukemia with methyl-glyoxal-bis-guanylhydrazone vs. 6-mercaptopurine

New Zealand Market Information

Mercaptopurine is currently not marketed in New Zealand, with no authorization records available in this evidence pack.

Cytotoxicity

Item	Content
Cytotoxicity Classification	Conventional cytotoxic (purine antimetabolite / thiopurine class)
Myelosuppression Risk	High — the literature in this pack consistently identifies neutropenia/leukopenia as the primary dose-limiting toxicity, strongly modulated by TPMT and NUDT15 genetic polymorphisms
Emetogenicity Classification	Please refer to the package insert warnings and precautions
Monitoring Items	CBC with differential, liver function tests, and TPMT/NUDT15 genotype or phenotype testing before and during therapy
Handling Protection	Standard cytotoxic drug handling precautions required

Safety Considerations

Please refer to the package insert for safety information.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Multiple Phase 3/4 trials and consistent literature confirm 6-mercaptopurine's established role in APL/AML maintenance regimens, giving this prediction L1-level evidence. However, the drug is not currently marketed in New Zealand, and this appears to be a formalization of existing off-label/protocol use rather than a genuinely novel mechanism — guardrails should focus on regulatory pathway and safety documentation rather than efficacy uncertainty.

To proceed, the following is needed:

TFDA package insert warnings/contraindications (currently a Blocking data gap — required before any S1 safety assessment)
Detailed mechanism of action data from DrugBank (currently a High-severity data gap)
A New Zealand market authorization pathway assessment, since the drug has zero existing licenses in-market
TPMT/NUDT15 pharmacogenomic testing protocol as part of any monitoring plan
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.