Trastuzumab

證據等級: L5

預測適應症: 10 個

Trastuzumab: From HER2-Positive Breast Cancer to Normal Breast-like Subtype of Breast Carcinoma

One-Sentence Summary

Trastuzumab is a HER2/ERBB2-targeted monoclonal antibody, historically established for HER2-overexpressing breast cancer (original indication data itself is a documented gap in this evidence pack — see below). The TxGNN model's top prediction is that trastuzumab may be effective for the normal breast-like PAM50 subtype of breast carcinoma, with 12 clinical trials and 1 publication currently associated with this prediction — though the evidence itself flags a mechanistic contradiction (see rationale below).

Quick Overview

Item	Content
Original Indication	Not available in the structured regulatory data (data gap). Based on the drug's known mechanism and the repurposing rationale embedded in this evidence pack, trastuzumab's established use is HER2-overexpressing breast cancer.
Predicted New Indication	Normal breast-like subtype of breast carcinoma
TxGNN Prediction Score	99.90% (rank 1423 of full candidate list)
Evidence Level	L3
Norway Market Status	✗ Not Marketed
Number of Authorizations	0
Recommended Decision	Hold (Research Question stage)

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available at the drug level (Data Gap DG002). Based on the mechanistic descriptions embedded throughout this evidence pack's repurposing rationale, trastuzumab is a humanized monoclonal antibody that binds the extracellular domain of HER2 (ERBB2), blocking its downstream proliferative signaling and mediating antibody-dependent cell-mediated cytotoxicity (ADCC). Its efficacy in HER2-overexpressing breast cancer has been extensively demonstrated, and the top TxGNN-predicted new indication — "normal breast-like" — is itself a molecular subtype of breast cancer, not a distinct disease category. In that narrow sense, the prediction is not a large mechanistic leap.

However, the evidence pack's own rationale for this specific prediction flags an important biological contradiction: the PAM50 "normal-like" subtype is clinically characterized by low proliferative activity and is frequently HER2-low or HER2-negative — the opposite of the population in which trastuzumab has proven benefit. None of the 12 associated clinical trials were designed to specifically enrich for or test this PAM50 subtype; most are general HER2-positive breast cancer trials in which trastuzumab appears as a background or comparator therapy. The single literature citation (PMID 19466513) discusses basal-like, not normal-like, tumor morphology, and is a general review rather than subtype-specific outcome data.

Taken together, this prediction is plausible only insofar as "normal breast-like" falls within the broad breast-cancer indication space trastuzumab already occupies — but the model's confidence score does not resolve the underlying mechanistic mismatch (HER2-targeted therapy applied to a typically HER2-low/negative subtype). This is why the evidence pack itself stages this candidate at S1 / "Research Question" rather than a more advanced decision stage.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT03168880	Phase 3	Active, Not Recruiting	720	Weekly paclitaxel ± carboplatin in large operable/locally advanced triple-negative (basal-like) breast cancer; population defined by conventional HER2 status, not PAM50 normal-like stratification (Grade B).
NCT01796197	Phase 2	Completed	23	Paclitaxel + trastuzumab + pertuzumab as pre-operative therapy for inflammatory HER2+ breast cancer; no subtype-specific design (Grade B).
NCT04329065	Phase 2	Recruiting	25	WOKVAC vaccine + neoadjuvant chemotherapy + HER2-targeted antibody therapy; trastuzumab is background treatment, not the primary evaluated agent (Grade C).
NCT06328387	Phase 1/2	Unknown	120	Hydroxychloroquine + antibody-drug conjugate vs. ADC alone in advanced breast cancer; status unknown, weak evidentiary value (Grade C).
NCT05900206	Phase 2	Recruiting	370	Trastuzumab deruxtecan (an ADC, not naked trastuzumab) with biology-driven treatment selection for HER2-positive breast cancer; does not directly test trastuzumab in normal-like subtype (Grade C).
NCT04759248	Phase 2	Active, Not Recruiting	55	ATREZZO study: atezolizumab + trastuzumab + vinorelbine in ER-negative or PAM50 non-luminal HER2-positive advanced/metastatic breast cancer.
NCT04750122	Phase 1/2	Recruiting	46	Drug-screening-guided neoadjuvant therapy using patient-derived tumor-like cell clusters in HER2-positive early breast cancer.
NCT06585969	Phase 3	Withdrawn	0	Trastuzumab deruxtecan vs. CDK4/6 inhibitors in non-Luminal A, ER-positive/HER2-low metastatic breast cancer; trial withdrawn before enrollment.
NCT01670877	Phase 2	Completed	56	Neratinib alone/with fulvestrant in HER2 non-amplified but HER2-mutant metastatic breast cancer.
NCT06348134	Phase 2	Recruiting	74	Efficacy/safety of optimal neoadjuvant-to-adjuvant anti-HER2 therapy in Nigerian women with HER2-positive breast cancer.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
19466513	2009	Review	Breast Cancer (Tokyo, Japan)	Describes morphological/cytopathological characteristics of the basal-like breast carcinoma subtype within the five-subtype intrinsic classification (luminal A, luminal B, normal-like, HER2-overexpressing, basal-like); does not directly address trastuzumab response in the normal-like subtype.

Norway Market Information

Trastuzumab is currently not marketed in this jurisdiction according to the regulatory data provided (0 authorizations, no license records available). No product/dosage-form table can be generated from this evidence pack.

Cytotoxicity

Trastuzumab is classified as antineoplastic — all TxGNN-predicted indications in this pack are cancers/tumors, and the drug's mechanism (HER2/ERBB2-targeted cytotoxic activity via ADCC) falls under oncology therapeutics.

Item	Content
Cytotoxicity Classification	Targeted therapy (HER2-targeted humanized monoclonal antibody; not conventional cytotoxic chemotherapy)
Myelosuppression Risk	Please refer to the package insert warnings and precautions (specific hematologic toxicity data not available in this evidence pack)
Emetogenicity Classification	Please refer to the package insert warnings and precautions
Monitoring Items	Please refer to the package insert warnings and precautions
Handling Protection	Please refer to the package insert warnings and precautions

Safety Considerations

Please refer to the package insert for safety information. (Key warnings, contraindications, and drug-drug interaction data are marked as data gaps in this evidence pack — DG001, Blocking severity — and could not be populated from the TFDA/regulatory label source.)

Conclusion and Next Steps

Decision: Hold (Research Question)

Rationale: The top-ranked prediction (normal breast-like PAM50 subtype) is supported only by L3 evidence — a single review article and no subtype-specific completed trials — and the evidence pack's own mechanistic rationale identifies a biological contradiction, since this subtype is typically HER2-low/negative, undermining trastuzumab's core targeted mechanism. This candidate should not advance past the research-question stage without subtype-specific validation. (Note: within this same evidence pack, the PR-positive and PR-negative breast cancer candidates, ranks 2–3, reach a stronger L2 evidence level with completed Phase 3 RCTs and are separately staged "Proceed with Guardrails" — these may warrant prioritization over the rank-1 candidate.)

To proceed, the following is needed:

TFDA/regulatory label data — warnings, contraindications, DDI (DG001, Blocking)
Confirmed, sourced mechanism-of-action documentation at the drug level (DG002)
HER2 expression prevalence data specifically within the PAM50 "normal-like" subtype population
A subtype-specific prospective trial (or retrospective biomarker-stratified analysis) testing trastuzumab response in HER2-low/negative "normal-like" tumors before this candidate can be re-staged
Disclaimer

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