Irinotecan

證據等級: L5

預測適應症: 1 個

Irinotecan: From Colorectal Cancer to Female Breast Carcinoma

One-Sentence Summary

Irinotecan is a topoisomerase I inhibitor globally approved for colorectal cancer and other gastrointestinal malignancies, where its active metabolite SN-38 induces tumour cell apoptosis via DNA replication fork collapse. The TxGNN model predicts it may be effective for Female Breast Carcinoma, with 22 clinical trials and 20 publications currently supporting this direction.

Quick Overview

Item	Content
Original Indication	Colorectal cancer (global standard; no Philippines registration on file)
Predicted New Indication	Female Breast Carcinoma
TxGNN Prediction Score	99.08%
Evidence Level	L2
Philippines Market Status	Not marketed
Number of Registrations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Irinotecan (CPT-11) is a prodrug converted in vivo to SN-38, a potent topoisomerase I (Top1) inhibitor. SN-38 stabilises the Top1–DNA covalent complex, prevents DNA strand religation, and causes replication-fork collapse with double-strand breaks — ultimately triggering tumour cell apoptosis. Breast cancer, particularly triple-negative breast cancer (TNBC), is characterised by high proliferative rates and elevated topoisomerase I expression, making it mechanistically sensitive to this class of agent.

The clearest mechanistic bridge between irinotecan and breast cancer is Sacituzumab Govitecan (SG), an FDA-approved antibody–drug conjugate that delivers SN-38 directly to tumour cells via a Trop-2-targeting antibody. SG carries full regulatory approval for metastatic TNBC and HR+/HER2− metastatic breast cancer — effectively confirming that SN-38 is cytotoxically active in the breast cancer microenvironment. This constitutes mechanism-level validation that goes well beyond a model prediction.

Importantly, irinotecan as a bare drug has also been evaluated directly in clinical trials. Phase 2 studies (NCT00072852; NCT03562390) enrolled patients with anthracycline- and taxane-refractory metastatic breast cancer, and a Phase 1 study specifically targeted triple-negative recurrent breast cancer (NCT00031681). Additionally, the PHENOMENAL Phase 2 trial (2026) demonstrated that liposomal irinotecan crosses the blood-brain barrier and shows antitumour activity in HER2-negative breast cancer with brain metastases — a particularly high-unmet-need population. Taken together, the mechanistic rationale and the clinical evidence base are mutually reinforcing.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT00072852	Phase 2	Completed	134	Single-agent irinotecan (two dosing schedules) in women with anthracycline-, taxane-, and capecitabine-refractory metastatic breast cancer. This is the core Phase 2 direct-efficacy trial for this repurposing prediction.
NCT01631552	Phase 1/2	Completed	515	Sacituzumab Govitecan (SN-38 ADC, anti-Trop-2) in epithelial cancers, with large TNBC and HR+/HER2− breast cancer cohorts. Pivotal trial confirming SN-38 payload activity in breast cancer microenvironment.
NCT03562390	Phase 2	Unknown	124	Single-arm irinotecan as third-line or later therapy in Chinese patients with locally recurrent or metastatic breast cancer previously treated with anthracyclines and taxanes. Directly evaluates irinotecan efficacy and safety in an Asian population.
NCT00031681	Phase 1	Completed	41	UCN-01 + irinotecan in solid tumours (Part I); exclusively in triple-negative recurrent breast cancer from 2007 onwards (Part II). Directly addresses TNBC subtype with irinotecan backbone.
NCT00083148	Phase 1	Completed	12	Irinotecan followed by capecitabine in advanced breast carcinoma; dose-finding study based on the rationale that irinotecan sensitises tumour cells to capecitabine.
NCT04640480	Phase 1	Completed	21	SNB-101 (novel nanoparticle SN-38 formulation) dose escalation in advanced solid tumours. Safety and PK profile of next-generation irinotecan-derived formulation.
NCT01770353	Phase 1	Completed	45	Nanoliposomal irinotecan (nal-IRI) PK and biodistribution in solid tumours; confirmed drug delivery to breast cancer tumour microenvironment and assessed feasibility of ferumoxytol MRI to predict response.
NCT03678883	Phase 1/2	Active, not recruiting	350	GSK-3β inhibitor 9-ING-41 combined with irinotecan (and other cytotoxics) in refractory cancers including breast cancer. Large-scale combination trial supporting irinotecan’s role in multi-line breast cancer therapy.
NCT05453825	Phase 2	Unknown	180	Navicixizumab (DLL4/VEGF bispecific antibody) ± irinotecan basket study with a dedicated TNBC cohort (Cohort C). Evaluates irinotecan as a combination partner in anti-angiogenic strategies.
NCT00004095	Phase 1	Completed	38	Irinotecan + gemcitabine in unresectable or metastatic solid tumours; established dosing, schedule, and safety for this combination regimen applicable to breast cancer.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
30786188	2019	Phase 1/2 Trial	N Engl J Med	Sacituzumab Govitecan in refractory mTNBC; ORR 33.3%, median PFS 5.5 months. Landmark study confirming SN-38 (irinotecan’s active metabolite) as a cytotoxic payload effective in TNBC.
36027558	2022	Phase 3 RCT	J Clin Oncol	TROPiCS-02: Sacituzumab Govitecan vs physician’s choice in HR+/HER2− metastatic breast cancer. SG significantly improved PFS, extending SN-38 efficacy evidence to luminal subtypes.
28291390	2017	Phase 2 Clinical Study	J Clin Oncol	Sacituzumab Govitecan in heavily pretreated mTNBC; ORR 30%, median OS 11.4 months. Phase 2 expansion cohort independently validating SN-38 cytotoxicity in breast cancer.
36302269	2022	Systematic Review	Breast	Comprehensive review of TROP-2-targeting ADCs (SG, datopotamab deruxtecan) in metastatic breast cancer; mechanism, clinical data, and emerging resistance patterns.
41371050	2026	Phase 2 Study	Eur J Cancer	PHENOMENAL trial: liposomal irinotecan (nal-IRI) in HER2-negative breast cancer with brain metastases. Demonstrates irinotecan’s blood-brain barrier penetration and antitumour activity in a high-unmet-need population.
31208270	2019	Mechanistic Review	mAbs	In-depth mechanistic review of SN-38-based ADC development; topoisomerase I inhibition, SN-38 potency advantages over conventional irinotecan, and design rationale for TROP-2-targeted delivery in solid tumours.
32223649	2020	Trial Protocol	Future Oncol	TROPiCS-02 study design and rationale; explains scientific basis for SN-38 payload targeting Trop-2-overexpressing HR+/HER2− breast cancer and outlines primary and secondary endpoints.
28558150	2017	Phase 1/2 Study	Cancer	IMMU-132 (sacituzumab govitecan) pharmacokinetics and safety at 8–10 mg/kg across diverse epithelial cancers; tolerability profile established for the SN-38 ADC platform.
12800602	2003	Review	Oncology	Mechanistic rationale for mitomycin + irinotecan synergy in advanced breast cancer; mitomycin upregulates topoisomerase I, increasing irinotecan sensitivity — foundational pharmacological argument for irinotecan use in breast cancer.
9726101	1998	Review	Oncology	Early overview of irinotecan’s broad antitumour activity across tumour types including breast, ovarian, pancreatic, and haematological malignancies. Historical foundation for this repurposing direction.

Philippines Market Information

Irinotecan is currently not registered with the FDA Philippines. No marketing authorisations, product licences, or Certificate of Product Registration records are on file.

Cytotoxicity

Item	Content
Cytotoxicity Classification	Conventional cytotoxic — Camptothecin analog (Topoisomerase I inhibitor)
Myelosuppression Risk	High — Dose-limiting neutropenia and delayed diarrhoea are class-defining toxicities. Patients homozygous for the UGT1A128 allele (and UGT1A16, prevalent in East/Southeast Asian populations) are at significantly elevated risk of severe neutropenia and require dose reduction.
Emetogenicity Classification	Moderate
Monitoring Items	CBC with differential (prior to each cycle and as clinically indicated), liver function tests, total and direct bilirubin, serum electrolytes, renal function; UGT1A1 genotyping prior to first dose
Handling Protection	Yes — must be prepared and administered by trained oncology personnel following cytotoxic drug handling regulations; closed-system drug transfer devices (CSTDs) recommended; standard cytotoxic PPE required for preparation and disposal

Safety Considerations

Please refer to the package insert for safety information.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Multiple completed Phase 2 trials have directly evaluated irinotecan in anthracycline- and taxane-refractory metastatic breast cancer, and the FDA approval of Sacituzumab Govitecan — whose cytotoxic payload is SN-38, the active metabolite of irinotecan — for both mTNBC and HR+/HER2− metastatic breast cancer provides mechanism-level validation that this compound class is active in the breast cancer setting. The TxGNN score of 99.08% is strongly aligned with the L2 clinical evidence base.

To proceed, the following is needed:

Philippines registration pathway: Irinotecan is currently unregistered in the Philippines; an import/compassionate use or full registration dossier pathway must be assessed before any clinical deployment
UGT1A1 genotyping programme: UGT1A1*6 allele (distinct from the UGT1A1*28 allele used in Western guidelines) is prevalent in Filipino and Asian populations; local genotyping capacity and dose-individualisation protocols must be established prior to use
Phase 3 data gap: The highest-level direct evidence for irinotecan as a bare drug in breast cancer remains Phase 2; a Phase 3 confirmatory trial or regulatory bridging strategy from SG approval data is needed for definitive indication approval
Safety information retrieval: Full prescribing information (warnings, contraindications, drug interactions) should be sourced from the originator package insert or regulatory dossier to complete the safety evaluation
Strategic decision on formulation: Determine whether the preferred local development path is irinotecan bare drug, liposomal irinotecan (nal-IRI), or SN-38-based ADC (Sacituzumab Govitecan), as each carries different evidence levels, cost implications, and access considerations for the Philippines market
Disclaimer

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