Trastuzumab
| Evidence Level: L1 | Predicted Indications: 10 |
Table of Contents
- Trastuzumab
- Trastuzumab: From HER2-Positive Breast Cancer to Progesterone-Receptor Positive Breast Cancer
Trastuzumab: From HER2-Positive Breast Cancer to Progesterone-Receptor Positive Breast Cancer
One-Sentence Summary
Trastuzumab is a HER2-targeted humanised monoclonal antibody whose established core indication is HER2-positive breast cancer, typically given alongside chemotherapy or endocrine therapy. The TxGNN model predicts it may also be effective for progesterone-receptor (PR) positive breast cancer, with 36 clinical trials and 20 publications currently linked to this prediction in the Evidence Pack, several of which directly enrol HER2-positive/PR-positive populations.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | HER2-positive breast cancer (an already-established core indication for trastuzumab, per the Evidence Pack’s mechanistic rationale; UK licence-specific indication text is not available in this pack) |
| Predicted New Indication | Progesterone-receptor (PR) positive breast cancer |
| TxGNN Prediction Score | 99.90% |
| Evidence Level | L1 |
| UK Market Status | Not marketed (as recorded in this Evidence Pack — see caveat under “UK Market Information”) |
| Number of Marketing Authorisations | 0 |
| Recommended Decision | Proceed with Guardrails |
Why is This Prediction Reasonable?
A structured mechanism-of-action field is flagged as a data gap in this Evidence Pack (DG002). However, one of the linked clinical trial records (NCT01785420) describes trastuzumab’s mechanism directly: it is “a humanised monoclonal antibody that acts extracellularly on the erbB-2 receptor,” shown “in both in vitro assays and in animals to inhibit the proliferation of human tumour cells that overexpress erbB-2,” and is “a potent mediator of antibody-dependent cell-mediated cytotoxicity (ADCC).” This HER2-blocking mechanism underlies trastuzumab’s established role in HER2-positive breast cancer, usually combined with chemotherapy, dual HER2 blockade (e.g. pertuzumab), or endocrine therapy.
Progesterone-receptor status is a biomarker used to stratify breast cancer subtypes rather than a mechanism that competes with or excludes HER2-driven signalling. HER2 overexpression and PR positivity frequently co-occur — so-called “triple-positive” breast cancer (ER+/PR+/HER2+) accounts for roughly 5–10% of all breast cancers (PMID 31410192) — and this subgroup is a recognised, actively studied population for anti-HER2 therapy.
Because HER2 amplification drives tumour proliferation largely independent of hormone-receptor status, trastuzumab’s antitumour effect via HER2 blockade would be expected to extend to the HER2-positive/PR-positive subgroup. This is supported empirically: several completed Phase 2/3 randomised trials in the Evidence Pack (e.g. NCT01275677, NCT00005970, NCT00667251, NCT04629846) already enrol and demonstrate benefit in HER2-positive populations that include PR-positive patients, and dedicated hormone-receptor-positive/HER2-positive trials (e.g. NCT00134680, NCT02689921, NCT02152943) test trastuzumab specifically alongside endocrine therapy in this subgroup.
Clinical Trial Evidence
| Trial Number | Phase | Status | Enrolment | Key Findings |
|---|---|---|---|---|
| NCT04629846 | Phase 3 | Completed | 517 | Compared trastuzumab + QL1209 (pertuzumab biosimilar) + docetaxel vs trastuzumab + pertuzumab + docetaxel as neoadjuvant therapy in early-stage/locally advanced HER2-positive breast cancer. |
| NCT03726879 | Phase 3 | Completed | 454 | IMpassion050: atezolizumab vs placebo added to neoadjuvant chemotherapy plus trastuzumab + pertuzumab in early HER2-positive breast cancer. |
| NCT00667251 | Phase 3 | Completed | 652 | Compared taxane-based chemotherapy plus lapatinib vs plus trastuzumab as first-line therapy in HER2-positive metastatic breast cancer. |
| NCT01275677 | Phase 3 | Completed | 3270 | Large adjuvant trial comparing chemotherapy alone vs chemotherapy plus trastuzumab in node-positive/high-risk node-negative HER2-low invasive breast cancer. |
| NCT00005970 | Phase 3 | Completed | 3436 | Landmark adjuvant trial (AC→paclitaxel ± trastuzumab) in HER2-overexpressing, node-positive/high-risk node-negative breast cancer. |
| NCT00545688 | Phase 2 | Completed | 417 | NeoSphere trial: four neoadjuvant regimens combining trastuzumab, docetaxel and pertuzumab in HER2-positive early/locally advanced breast cancer. |
| NCT00999804 | Phase 2 | Active, not recruiting | 128 | TBCRC 023: neoadjuvant lapatinib plus trastuzumab, with or without endocrine therapy, over 12 vs 24 weeks in HER2-overexpressing breast cancer. |
| NCT02152943 | Phase 1 | Completed | 37 | Everolimus + trastuzumab + letrozole in hormone receptor-positive and HER2-positive advanced/metastatic breast cancer, exploring synergy and resistance reversal. |
| NCT00134680 | Phase 2 | Completed | 33 | Letrozole plus trastuzumab in ErbB2-positive, ER and/or PR-positive metastatic breast cancer — directly relevant to the PR-positive/HER2-positive population. |
| NCT02689921 | Phase 2 | Unknown | 7 | NEOADAPT: chemotherapy-free neoadjuvant aromatase inhibitor plus pertuzumab/trastuzumab in HR-positive (including PR-positive), HER2-positive localised breast cancer. |
Literature Evidence
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 32353342 | 2020 | RCT (monarcHER) | Lancet Oncology | Abemaciclib + trastuzumab ± fulvestrant vs chemotherapy + trastuzumab in HR-positive, HER2-positive advanced breast cancer. |
| 26874901 | 2016 | RCT (ExteNET) | Lancet Oncology | Phase 3 placebo-controlled trial of neratinib after trastuzumab-based adjuvant therapy in HER2-positive breast cancer. |
| 37166817 | 2023 | RCT (WSG-TP-II) | JAMA Oncology | Neoadjuvant endocrine therapy plus trastuzumab/pertuzumab vs de-escalated chemotherapy in HR-positive/HER2-positive early breast cancer. |
| 27179402 | 2016 | Cohort (long-term follow-up) | Lancet Oncology | 5-year follow-up of NeoSphere: neoadjuvant pertuzumab + trastuzumab and long-term outcomes in HER2-positive breast cancer. |
| 31410192 | 2019 | Cohort | Theranostics | Molecular portraits and trastuzumab responsiveness of ER-positive/PR-positive/HER2-positive (“triple-positive”) breast cancer. |
| 35640077 | 2022 | Guideline update | Journal of Clinical Oncology | ASCO guideline update on systemic therapy for advanced HER2-positive breast cancer. |
| 39631485 | 2024 | Review | Pharmacological Research | Review of targeted and cytotoxic inhibitors used in breast cancer, including anti-HER2 agents. |
| 34983437 | 2022 | Retrospective cohort | BMC Cancer | Trastuzumab plus fulvestrant combination therapy in hormone-receptor-positive and HER2-positive advanced breast cancer. |
| 28945833 | 2017 | Phase 2 trial (WSG-ADAPT) | Annals of Oncology | De-escalated neoadjuvant dual HER2 blockade (trastuzumab + pertuzumab) ± paclitaxel in HER2-positive/hormone-receptor-negative early breast cancer. |
| 40339592 | 2025 | Phase 2a trial | Lancet Oncology | Zanidatamab plus palbociclib and fulvestrant in previously treated hormone-receptor-positive, HER2-positive metastatic breast cancer. |
UK Market Information
No MHRA marketing authorisation records are present in this Evidence Pack (0 licences listed; market status recorded as “not marketed”).
Caveat: Trastuzumab is a widely used, long-established HER2-targeted biologic in UK oncology practice, and this “0 licences / not marketed” result is inconsistent with its known clinical use. This most likely reflects a gap in the underlying regulatory dataset feeding this Evidence Pack (biologics/injectable licence records may not have been captured) rather than genuine market absence. Before any decision-making, MHRA licence status should be verified directly against the MHRA products database rather than relying on this pack alone.
Cytotoxicity
Trastuzumab is an antineoplastic agent (HER2-targeted monoclonal antibody used in the treatment of malignant breast cancer), so this section applies.
| Item | Content |
|---|---|
| Cytotoxicity Classification | Targeted therapy (anti-HER2 humanised monoclonal antibody; not a conventional cytotoxic chemotherapeutic) |
| Myelosuppression Risk | Not characterised in this Evidence Pack; please refer to the SmPC warnings and precautions. Trastuzumab monotherapy is not typically classed as myelosuppressive, though risk rises substantially when combined with cytotoxic chemotherapy partners (e.g. taxanes, anthracyclines) |
| Emetogenicity Classification | Please refer to the SmPC warnings and precautions |
| Monitoring Items | Please refer to the SmPC warnings and precautions; cardiac function assessment (e.g. LVEF) is a standard monitoring requirement for anti-HER2 antibody therapy |
| Handling Protection | Trastuzumab is a biologic (monoclonal antibody) rather than a conventional cytotoxic agent; please follow local biologic/antibody handling protocols and the SmPC |
Safety Considerations
Please refer to the SmPC and BNF for safety information. Report suspected adverse reactions via the Yellow Card Scheme.
(Note: this Evidence Pack’s key warnings, contraindications and drug-interaction fields are all flagged as data gaps — DG001, a Blocking-severity gap — meaning a formal S1 safety screen cannot yet be completed from this pack alone.)
Conclusion and Next Steps
Decision: Proceed with Guardrails
Rationale: Evidence strength is high (L1) — multiple completed Phase 3 RCTs (NCT01275677, NCT00005970, NCT00667251, NCT04629846) and supportive literature (e.g. monarcHER, WSG-TP-II, ExteNET) establish trastuzumab’s efficacy in HER2-positive breast cancer populations that include PR-positive patients. However, this Evidence Pack lacks the UK-specific regulatory and safety documentation (MOA, SmPC warnings/contraindications, confirmed MHRA licence status) needed to close out a full safety review.
To proceed, the following is needed:
- Verify current UK MHRA marketing authorisation status and licence numbers directly with the MHRA product database (the “0 licences” result in this pack is flagged as a Blocking data gap, DG001, and appears inconsistent with trastuzumab’s known UK availability)
- Obtain formal mechanism-of-action and SmPC documentation (DG002)
- Obtain SmPC-sourced key warnings, contraindications and drug–drug interaction data to complete the S1 safety screen
- Confirm PR-status-specific subgroup efficacy data, since most trials analyse the broader HER2-positive population with HR status as a secondary stratification factor rather than a primary PR-positive endpoint
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.