{"entity":{"id":"her3-expression","kind":"biomarker","name":"HER3 expression","aka":["HER3","ERBB3 expression","HER3-positive","HER3 IHC"],"tldr":"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.","asOf":"2026-09-23","links":[{"label":"ClinicalTrials.gov NCT05338970 (HERTHENA-Lung02)","url":"https://clinicaltrials.gov/study/NCT05338970"}],"tags":["biomarker","surface-antigen","no-threshold"],"related":["egfr-exon-19-deletion","her2-ihc-3-plus"],"cancers":["nsclc","breast-cancer"],"sections":[],"technologies":[],"targets":[],"drugs":["patritumab-deruxtecan"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"her3","measurement":"ihc-score","scoringRule":{"text":"The label names the antigen in the drug's description but does not require it to be measured before treatment; no approval threshold exists for this readout.","quote":"HERTHENA-Lung02: patritumab deruxtecan versus platinum-based chemotherapy in EGFR-mutated NSCLC after EGFR TKI","source":"https://clinicaltrials.gov/study/NCT05338970","sourceLabel":"ClinicalTrials.gov NCT05338970 (HERTHENA-Lung02)"},"thresholds":[],"definedBy":{"label":"HERTHENA-Lung02 (NCT05338970)","url":"https://clinicaltrials.gov/study/NCT05338970"},"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"There is no approved HER3-directed drug and no HER3 test you would routinely have. Patritumab deruxtecan is available only in trials, which enrol on the EGFR mutation rather than on HER3 staining."},"route":"/biomarkers/her3-expression/","neighbours":{"biomarker":[{"id":"egfr-exon-19-deletion","kind":"biomarker","name":"EGFR exon 19 deletion","route":"/biomarkers/egfr-exon-19-deletion/"},{"id":"her2-ihc-3-plus","kind":"biomarker","name":"HER2 IHC 3+ (HER2-positive by immunohistochemistry)","route":"/biomarkers/her2-ihc-3-plus/"}],"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"}],"drug":[{"id":"patritumab-deruxtecan","kind":"drug","name":"Patritumab deruxtecan","route":"/drugs/patritumab-deruxtecan/"}],"target":[{"id":"her3","kind":"target","name":"HER3","route":"/targets/her3/"}]}}