Trastuzumab

證據等級: L5

預測適應症: 10 個

Trastuzumab: From HER2-Positive Breast Cancer to Progesterone-Receptor Positive Breast Cancer

One-Sentence Summary

Trastuzumab is a HER2-targeted humanized monoclonal antibody, well established for HER2-positive breast cancer (the evidence pack itself does not supply a Danish-registered indication text for this drug). The TxGNN model predicts it may be effective for progesterone-receptor positive breast cancer, with 36 clinical trials and 20 publications currently associated with this hypothesis — though the strongest evidence points to the HR+/HER2+ co-expressing subgroup rather than PR status alone.

Quick Overview

Item	Content
Original Indication	Not available from the Danish licensing data in this evidence pack (`taiwan_regulatory.licenses` is empty); trastuzumab’s globally established original indication is HER2-positive breast cancer
Predicted New Indication	Progesterone-receptor positive breast cancer
TxGNN Prediction Score	99.90%
Evidence Level	L1
Denmark Market Status	Not marketed
Number of Marketing Authorisations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Currently, detailed mechanism-of-action data is not available in this evidence pack (flagged as a High-severity data gap, DG002). Based on generally known pharmacology, trastuzumab is a humanized IgG1 monoclonal antibody that binds the extracellular domain of human epidermal growth factor receptor 2 (HER2/ERBB2), blocking HER2-driven proliferation signalling and mediating antibody-dependent cellular cytotoxicity (ADCC). Its efficacy in HER2-positive breast cancer is proven across numerous pivotal trials, and mechanistically it may extend to progesterone-receptor positive breast cancer where HER2 co-expression is present.

Importantly, the underlying repurposing rationale supplied with the evidence pack clarifies that PR status is not itself the pharmacological target — trastuzumab’s indication is determined by HER2 status, not hormone-receptor status. The clinical trials and literature listed for this “new” indication predominantly enrol HR+/HER2+ (triple-positive) patients, a population where trastuzumab is already standard of care. This means the prediction should be interpreted as confirmation of an existing, guideline-recognized use in a HER2+ subgroup that happens to be PR-positive, rather than a genuinely novel repurposing hypothesis into an unrelated disease area.

The large Phase III trials in the evidence (e.g., adjuvant regimens with over 3,000 patients each) directly test trastuzumab-containing regimens in HER2-overexpressing breast cancer populations that include PR-positive tumours, which is why the evidence level reaches L1 despite the conceptual overlap with the original indication.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT01275677	Phase 3	Completed	3270	Adjuvant chemotherapy ± trastuzumab in node-positive or high-risk node-negative HER2-low invasive breast cancer
NCT00667251	Phase 3	Completed	652	Taxane-based chemotherapy + lapatinib vs. + trastuzumab as first-line therapy in HER2+ metastatic breast cancer
NCT02152943	Phase 1	Completed	37	Everolimus + letrozole + trastuzumab in hormone receptor-positive and HER2-positive advanced/metastatic breast cancer and other solid tumours
NCT00005970	Phase 3	Completed	3436	Doxorubicin/cyclophosphamide followed by paclitaxel ± trastuzumab as adjuvant treatment in HER2-overexpressing node-positive or high-risk node-negative breast cancer
NCT04629846	Phase 3	Completed	517	QL1209 (pertuzumab biosimilar) vs. reference pertuzumab, each + trastuzumab + docetaxel, in HER2-positive/ER-PR-negative early or locally advanced breast cancer
NCT03726879	Phase 3	Completed	454	IMpassion050: atezolizumab vs. placebo + neoadjuvant dose-dense AC then paclitaxel + trastuzumab + pertuzumab in early HER2-positive breast cancer
NCT00545688	Phase 2	Completed	417	4-arm neoadjuvant Herceptin ± docetaxel ± pertuzumab in locally advanced, inflammatory, or early-stage HER2-positive breast cancer
NCT00134680	Phase 2	Completed	33	Letrozole + trastuzumab in ErbB2-positive, estrogen and/or progesterone receptor-positive metastatic breast cancer
NCT04152057	Phase 1/2	Unknown	20	Pyrotinib + albumin-bound paclitaxel + trastuzumab in HER2-positive early or locally advanced breast cancer
NCT00999804	Phase 2	Active, not recruiting	128	TBCRC 023: Lapatinib + trastuzumab, with or without endocrine therapy, for 12 vs. 24 weeks in HER2-overexpressing breast cancer

Literature Evidence

PMID	Year	Type	Journal	Key Findings
27179402	2016	RCT	Lancet Oncol	NeoSphere 5-year follow-up: neoadjuvant pertuzumab + trastuzumab + docetaxel improves progression-free and disease-free survival in HER2-positive breast cancer
32353342	2020	RCT	Lancet Oncol	monarcHER: abemaciclib + trastuzumab ± fulvestrant vs. chemotherapy + trastuzumab in HR+/HER2+ advanced breast cancer
26874901	2016	RCT	Lancet Oncol	ExteNET: neratinib after trastuzumab-based adjuvant therapy in HER2-positive breast cancer
29117498	2017	Cohort	NEJM	20-year recurrence risk after stopping 5 years of endocrine therapy in ER-positive early breast cancer
31410192	2019	Pending classification	Theranostics	Molecular portraits and trastuzumab responsiveness of ER-positive, PR-positive, and HER2-positive (triple-positive) breast cancer
34983437	2022	Pending classification	BMC Cancer	Trastuzumab + fulvestrant combination therapy in HR-positive/HER2-positive advanced breast cancer (retrospective single-centre study)
37166817	2023	Pending classification	JAMA Oncol	WSG-TP-II randomized trial: endocrine therapy + trastuzumab + pertuzumab vs. de-escalated chemotherapy in HR+/HER2+ early breast cancer
35640077	2022	Pending classification	J Clin Oncol	ASCO guideline update: systemic therapy for advanced HER2-positive breast cancer
39191270	2024	Pending classification	JNCCN	Clinical Treatment Score post-5 years (CTS5) and late recurrence risk in HR+/HER2+ breast cancer
26253814	2015	Review	Breast	Clinical implications of the intrinsic molecular subtypes of breast cancer

Denmark Market Information

No marketing authorisation records are present in the evidence pack (taiwan_regulatory.licenses is empty, total_licenses = 0, market_status = "Not marketed"). Trastuzumab does not currently have a registered marketing authorisation in this dataset for the Danish market.

Cytotoxicity

Trastuzumab is an antineoplastic agent (breast/gastric cancer indications; DrugBank monoclonal antibody classification).

Item	Content
Cytotoxicity Classification	Targeted therapy (HER2-targeted humanized monoclonal antibody; not a conventional cytotoxic chemotherapeutic)
Myelosuppression Risk	Please refer to the Summary of Product Characteristics (SmPC) warnings and precautions
Emetogenicity Classification	Please refer to the Summary of Product Characteristics (SmPC) warnings and precautions
Monitoring Items	Please refer to the Summary of Product Characteristics (SmPC) warnings and precautions
Handling Protection	Please refer to the Summary of Product Characteristics (SmPC) warnings and precautions

Safety Considerations

Please refer to the approved Summary of Product Characteristics (SmPC) for safety information. Note that a formal Danish/EU label warnings-and-contraindications lookup is flagged as a Blocking data gap (DG001) in this evidence pack — this must be resolved before a formal safety pre-assessment (S1) can proceed.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale:

Evidence level L1 is supported by multiple completed Phase III RCTs and a direct Phase I combination trial in the HR+/HER2+ population, but the repurposing rationale itself notes this largely confirms an existing HER2-positive breast cancer indication in a PR-positive subgroup, rather than establishing a genuinely novel indication.
Trastuzumab is currently not marketed in Denmark (0 authorisations on record), and formal label/safety data (warnings, contraindications, DDI) are missing, which blocks a complete safety pre-assessment.

To proceed, the following is needed:

TFDA/EMA-approved product label (SmPC) with warnings, contraindications, and DDI data (Blocking gap, DG001)
Formal mechanism-of-action documentation from DrugBank or equivalent source (DG002)
Confirmation of Danish marketing authorisation pathway, given the drug is not currently marketed locally
Clarification of whether the target population should be defined by HER2 status (established use) rather than PR status alone, to distinguish genuine repurposing value from label-extension confirmation
Disclaimer

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