Pertuzumab

Evidence Level: L5

Predicted Indications: 6

Pertuzumab

Pharmacist Assessment Report

Pertuzumab: Ectomesenchymoma

One-Sentence Summary

Pertuzumab is a HER2-targeted monoclonal antibody, originally used to treat HER2-positive breast carcinoma. This is largely an extension within the existing HER2-positive indication rather than true new-disease repurposing, because the benefit depends on HER2 status, not progesterone receptor (PR) status.

Quick Overview

Item	Content
Original Indication	Not recorded in the local data
Predicted New Indication	Ectomesenchymoma
TxGNN Prediction Score	0.9971
Evidence Level	L5 (as assigned in the data compiled for this report; see note below)
Australia Market Status	Listed on the PBS Schedule (1 of 1 items) – TGA (ARTG) registration status is not included in this data
Number of PBS Items	1 (valid: 1)
Recommended Decision	Proceed with Guardrails

Note on evidence level: The L1 rating is based on randomised Phase 3 and Phase 2 evidence. Only one completed Phase 3 trial is listed, and it is a biosimilar equivalence study. A strict reading of the rules (two or more completed Phase 3 RCTs) would be more conservative, so this rating should be read with caution.

Why is This Prediction Reasonable?

Detailed mechanism of action data is not available in the data compiled for this report. Based on known pharmacology, pertuzumab binds HER2 subdomain II and blocks HER2/HER3 heterodimerisation. This inhibits PI3K/AKT and MAPK signalling in HER2-positive tumours.

Hormone receptor-positive/HER2-positive breast cancer is a molecular subset of the already approved HER2-positive breast cancer indication, so the mechanism applies directly. The effect depends on HER2 status rather than PR status. Cross-talk between the HER2 and hormone receptor pathways is described in the literature, which is why combinations with endocrine therapy are of interest.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrolment	Key Findings
NCT04629846	Phase 3	Completed	517	Randomised, double-blind trial of the pertuzumab biosimilar QL1209 vs reference pertuzumab, each with trastuzumab and docetaxel, in early or locally advanced HER2-positive, ER/PR-negative breast cancer. This is a biosimilar equivalence comparison, not a test of a new indication.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
42150145	2026	RCT	J Clin Oncol	Survival analysis of WSG TP-II: neoadjuvant trastuzumab + pertuzumab with endocrine therapy vs weekly paclitaxel in HR-positive/HER2-positive early breast cancer
37166817	2023	RCT	JAMA Oncol	WSG-TP-II: endocrine therapy plus dual HER2 blockade vs de-escalated chemotherapy in HR-positive/HER2-positive early breast cancer
27179402	2016	RCT (Phase 2)	Lancet Oncol	NeoSphere 5-year analysis: progression-free and disease-free survival and safety of neoadjuvant pertuzumab plus trastuzumab
28945833	2017	RCT (Phase 2)	Ann Oncol	WSG-ADAPT HER2+/HR-: 12 weeks of dual blockade with or without weekly paclitaxel
38906970	2024	RCT	Br J Cancer	Phase 3 equivalence of pertuzumab biosimilar QL1209 vs reference pertuzumab in HER2-positive, ER/PR-negative disease
41401771	2026	RCT	ESMO Open	Phase 3 equivalence of pertuzumab biosimilar TQB2440 vs reference pertuzumab
35640077	2022	Guideline	J Clin Oncol	ASCO guideline update on systemic therapy for advanced HER2-positive breast cancer
27057657	2016	Review	Cancer Treat Rev	Review of HR-positive/HER2-positive breast cancer, including pathway cross-talk
41387082	2026	Cohort	Breast	Retrospective study of ovarian function suppression plus aromatase inhibitors in premenopausal HR+/HER2+ patients
40983817	2025	Review	Breast Cancer	Signalling pathway interactions and clinical translation in HR+/HER2+ breast cancer

Australia Market Information

ARTG Number	Product Name	Dosage Form	Approved Indication
ARTG 10267J	Perjeta	Solution for I.V. infusion 420 mg in 14 mL	Approved indication text not available in the data compiled for this report

Cytotoxicity

Item	Content
Cytotoxicity Classification	Targeted therapy (HER2-directed monoclonal antibody)
Myelosuppression Risk	Low as a single agent; haematological toxicity is mainly driven by the combined chemotherapy (e.g. docetaxel)
Emetogenicity Classification	Low
Monitoring Items	Left ventricular ejection fraction (cardiac function) before and during treatment; FBC, liver and renal function as required by the combined chemotherapy
Handling Protection	Please refer to the Product Information (PI) and local institutional policy

Safety Considerations

Drug Interactions: A moderate interaction with idelalisib is recorded. The other interaction entry describes pertuzumab’s pharmacological target (ERBB2/HER2), not a drug-drug interaction.
Cardiac safety: Cardiac safety studies of pertuzumab, trastuzumab and chemotherapy (TRYPHAENA, BERENICE) are available in the literature. Cardiac monitoring is advised.
Pregnancy: Reports of use during pregnancy are limited, so this requires specialist advice.

For key warnings and contraindications, please refer to the TGA-approved Product Information (PI).

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Pertuzumab is already registered in Australia, and randomised evidence supports its use in HER2-positive breast cancer, including HR-positive subsets. The predicted indication falls within the existing HER2-positive indication, so the real question is HER2 status and treatment combination, not a new disease.

To proceed, the following is needed:

Confirmation of HER2 positivity before treatment
Cardiac function monitoring plan
Review of endocrine therapy combinations for HR-positive/HER2-positive disease
Confirmation of the approved indication wording from the ARTG entry and the TGA Product Information
Mechanism of action data and PI-based warnings and contraindications, which are not yet available
Disclaimer

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