# HER3 expression

Source: https://onco.cc/biomarkers/her3-expression/  
OnCo record `her3-expression` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

HER3 is a signalling partner of EGFR and HER2 present on most lung and breast cancers. Patritumab deruxtecan was studied in EGFR-mutant lung cancer without a HER3 threshold, and no approval exists.

## Summary

Patritumab deruxtecan showed activity in EGFR-mutant NSCLC after osimertinib (HERTHENA-Lung01, HERTHENA-Lung02, NCT05338970) irrespective of HER3 membrane H-score; the US application received a complete response letter in 2024 on manufacturing grounds and no approval has followed. NRG1 fusions, which signal through HER3, are the selection marker for zenocutuzumab, a separate readout.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: HER3; ERBB3 expression; HER3-positive; HER3 IHC
- Tags: biomarker; surface-antigen; no-threshold

## Sources

- ClinicalTrials.gov NCT05338970 (HERTHENA-Lung02): https://clinicaltrials.gov/study/NCT05338970

## Connected records

- biomarkers: [EGFR exon 19 deletion](https://onco.cc/biomarkers/egfr-exon-19-deletion/), [HER2 IHC 3+ (HER2-positive by immunohistochemistry)](https://onco.cc/biomarkers/her2-ihc-3-plus/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/)
- drugs: [Patritumab deruxtecan](https://onco.cc/drugs/patritumab-deruxtecan/)
- targets: [HER3](https://onco.cc/targets/her3/)

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JSON: https://onco.cc/api/v1/entities/her3-expression.json