Trastuzumab Emtansine

證據等級: L5

預測適應症: 4 個

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

One-Sentence Summary

Trastuzumab emtansine (T-DM1, DrugBank DB05773) is an antibody-drug conjugate already used worldwide for HER2-positive breast cancer. The TxGNN model predicts it may also be effective specifically for progesterone-receptor (PR) positive breast cancer, with 4 clinical trials and 15 publications currently associated with this direction, though the drug itself is not registered on the local market.

Quick Overview

Item	Content
Original Indication	Not available in local (Taiwan/NZ) regulatory data — no licenses on file. Globally, trastuzumab emtansine (Kadcyla) is approved for HER2-positive breast cancer, generally in patients previously treated with trastuzumab and a taxane.
Predicted New Indication	Progesterone-receptor positive breast cancer
TxGNN Prediction Score	99.82% (rank 2195)
Evidence Level	L2
New Zealand Market Status	✗ Not Marketed
Number of Authorizations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism of action data is not available in this Evidence Pack (marked as a High-severity data gap). Based on general drug class knowledge, trastuzumab emtansine is an antibody-drug conjugate (ADC) that links trastuzumab, a monoclonal antibody targeting HER2, to DM1 (emtansine), a maytansinoid microtubule inhibitor. The antibody component delivers the cytotoxic payload specifically to HER2-expressing tumor cells, combining HER2 pathway blockade with targeted chemotherapy.

Progesterone-receptor (PR) status is a hormone-receptor biomarker that commonly co-occurs with HER2 positivity in a subset of breast cancers (HR+/HER2+ disease), rather than a mechanistically distinct disease. Since trastuzumab emtansine's activity depends on HER2 expression rather than hormone-receptor status, its efficacy would be expected to extend to HER2-positive tumors regardless of PR status — which is consistent with the TxGNN model surfacing this indication as a molecularly-defined subgroup within the drug's existing target population.

This is further supported by the clinical trial evidence below, which includes a completed Phase 3 randomized trial evaluating trastuzumab/pertuzumab-based regimens in early HER2-positive breast cancer, and by an extensive literature base (ASCO/EGTM guidelines, biomarker reviews) that explicitly discusses HR (including PR) status alongside HER2 status in guiding anti-HER2 ADC therapy.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT03726879	Phase 3	Completed	454	IMpassion050: randomized, double-blind, placebo-controlled trial of atezolizumab vs. placebo added to neoadjuvant ddAC-Paclitaxel-Trastuzumab-Pertuzumab in early HER2-positive breast cancer (T2-4, N1-3, M0)
NCT02326974	Phase 2	Active, not recruiting	164	Evaluates T-DM1 in combination with pertuzumab in the preoperative setting; studies impact of HER2 heterogeneity on treatment response
NCT04675827	Phase 2	Terminated	139	DECRESCENDO: de-escalation study of adjuvant chemotherapy in HER2-positive, ER-negative, node-negative early breast cancer achieving pathological complete response after neoadjuvant dual HER2 blockade
NCT06131424	N/A (observational)	Completed	1151	Multicenter retrospective study estimating prevalence and clinical characteristics of HER2-low locally-advanced/metastatic breast cancer previously classified as HER2-negative

Literature Evidence

PMID	Year	Type	Journal	Key Findings
35640077	2022	Guideline	J Clin Oncol	ASCO guideline update on systemic therapy for HER2-positive advanced breast cancer
29939838	2018	Guideline	J Clin Oncol	ASCO clinical practice guideline update for systemic therapy in advanced HER2-positive breast cancer, incorporating hormone-receptor status
24799465	2014	Guideline	J Clin Oncol	Earlier ASCO evidence-based guideline on systemic therapy for advanced HER2-positive breast cancer
28259011	2017	Guideline/Review	Eur J Cancer	EGTM updated guidelines on ER/PR and HER2 biomarker testing to guide endocrine and anti-HER2 (including T-DM1) therapy selection
33726508	2021	Review	Future Oncology	Reviews treatment trends in HR+/HER2+ breast cancer, including trastuzumab emtansine among novel anti-HER2 therapies
39631485	2024	Review	Pharmacological Research	Reviews targeted and cytotoxic inhibitors in breast cancer, discussing management by HER2/HR/ER/PR status
24892840	2013	Review	Clin Adv Hematol Oncol	Reviews integration of new data into metastatic breast cancer practice, stratified by ER/PR/HER2 subtype
34215766	2021	Observational	Scientific Reports	ChangeHER real-world study on prognostic relevance of HER2-positivity gain in metastatic breast cancer treated with pertuzumab/T-DM1
35251981	2022	Case Report/Review	Frontiers in Oncology	Case report and literature review of HER2-positive breast cancer with leptomeningeal disease (ER-negative, PR-negative tumor characterized)
40642740	2025	Case Report/Review	J Medical Cases	Long-term follow-up case and literature review of durable response with an anti-HER2 ADC in metastatic breast cancer

New Zealand Market Information

This drug currently has no registered authorizations on file (0 licenses) — trastuzumab emtansine is not marketed locally at this time.

Cytotoxicity

Item	Content
Cytotoxicity Classification	Targeted therapy — HER2-targeted antibody-drug conjugate (ADC) delivering a cytotoxic maytansinoid payload (DM1)
Myelosuppression Risk	No structured toxicity data in this Evidence Pack; thrombocytopenia is a well-recognized, often dose-limiting toxicity for this drug class per general prescribing knowledge — please refer to the package insert for confirmed rates
Emetogenicity Classification	Please refer to the package insert warnings and precautions
Monitoring Items	Platelet count/CBC with differential, liver function tests, cardiac function (LVEF), infusion-related reactions
Handling Protection	Cytotoxic payload warrants handling per institutional hazardous/cytotoxic drug protocols

Safety Considerations

Please refer to the package insert for safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: A Blocking-severity data gap (missing TFDA/Medsafe label warnings and contraindications) prevents completion of the S1 safety pre-assessment, and the drug is not currently marketed locally (0 authorizations). While the mechanistic rationale is sound and one completed Phase 3 trial plus supporting guideline-level literature exist, the predicted "new indication" largely reflects a biomarker subgroup of an already-established HER2-positive breast cancer population rather than a distinct novel use.

To proceed, the following is needed:

TFDA/Medsafe package insert warnings and contraindications (resolve DG001)
Confirmed mechanism of action data from DrugBank (resolve DG002)
Drug-drug interaction data (currently not found)
Local regulatory pathway assessment given zero current NZ market authorizations
Disclaimer

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