Claudin-18.2 expression (CLDN18.2)

Deterministic view of the source YAML entity. Clinical authority remains with the cited source IDs and reviewer sign-off state.

ID	`BIO-CLDN18-2`
Type	Biomarker
Aliases	CLDN18.2Claudin 18.2Claudin-18 isoform 2 expressionZolbetuximab companion biomarkerЕкспресія клаудину-18.2 (CLDN18.2)
Status	reviewed 2026-04-30 \| pending_clinical_signoff
Diseases	None declared
Sources	`SRC-ESMO-GASTRIC-2024` `SRC-NCCN-GASTRIC-2025`

Biomarker Facts

Biomarker type	protein_expression_ihc
Measurement	MethodIHC with VENTANA CLDN18 (43-14A) RxDx assay (zolbetuximab companion diagnostic). Score: % of tumor cells with moderate-to-strong (2+/3+) membranous staining. Unitscategorical: positive (≥75% of tumor cells with 2+/3+ membranous staining) \| negative
Related biomarkers	`BIO-HER2-SOLID` `BIO-MSI-STATUS` `BIO-PDL1-CPS`

Notes

CLDN18.2 is a tight-junction protein normally restricted to gastric mucosa; aberrantly expressed in gastric/GEJ, pancreatic, and biliary adenocarcinomas. Zolbetuximab is a chimeric IgG1 mAb targeting CLDN18.2 — first FDA approval Oct 2024 (SPOTLIGHT mFOLFOX6 + GLOW CAPOX registrational trials). Companion diagnostic VENTANA CLDN18 (43-14A) RxDx required. SPOTLIGHT: mOS 18.2 vs 15.5 mo (HR 0.75); GLOW: mOS 14.4 vs 12.2 mo (HR 0.77). Hierarchy when multiple actionable signals co-occur: HER2+ (TOGA/KEYNOTE-811) > MSI-H (KEYNOTE-859) > CLDN18.2+ (SPOTLIGHT/GLOW) > PD-L1 CPS≥5 ICI add-on (CheckMate-649).

Used By

Actionability

BMA-CLDN18-2-GASTRIC - Zolbetuximab (anti-CLDN18.2 chimeric IgG1 mAb) + chemotherapy is FDA-approved (Oct 2024)...

Biomarker

BIO-FGFR2B-IHC - FGFR2b protein expression by IHC (membranous staining)

Indications

IND-GASTRIC-METASTATIC-1L-CLDN18-2-ZOLBETUXIMAB - IND-GASTRIC-METASTATIC-1L-CLDN18-2-ZOLBETUXIMAB
IND-GASTRIC-METASTATIC-1L-FGFR2B-BEMARITUZUMAB - IND-GASTRIC-METASTATIC-1L-FGFR2B-BEMARITUZUMAB