# Claudin 18.2 expression (>= 75% of tumour cells, moderate to strong)

Source: https://onco.cc/biomarkers/cldn18-2-expression/  
OnCo record `cldn18-2-expression` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Claudin 18.2 is a tight-junction protein exposed on stomach cancer cells. Zolbetuximab requires at least 75 percent of tumour cells to stain moderately or strongly, the strictest expression threshold in any current label.

## Summary

Zolbetuximab (Vyloy) is labelled with fluoropyrimidine and platinum chemotherapy for first-line HER2-negative gastric or GEJ adenocarcinoma whose tumours are CLDN18.2 positive as determined by an FDA-approved test; the SPOTLIGHT and GLOW trials and the VENTANA CLDN18 (43-14A) RxDx Assay define positivity as 75 percent or more of tumour cells with moderate to strong membranous staining. About 38 percent of screened patients met the bar. CLDN18.2 ADCs and CAR-T cells in trials use lower or different cut-offs.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: CLDN18.2; Claudin 18.2 positive; CLDN18.2-positive; claudin 18.2 expression; CLDN18 IHC; CLDN18.2 >= 75%
- Tags: biomarker; surface-antigen

## Sources

- VYLOY prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e7695a21-abb6-47ac-93f8-0ece5a9c4409

## Connected records

- biomarkers: [HER2 IHC 3+ (HER2-positive by immunohistochemistry)](https://onco.cc/biomarkers/her2-ihc-3-plus/), [PD-L1 CPS (combined positive score)](https://onco.cc/biomarkers/pd-l1-cps/)
- cancers: [Claudin 18.2-positive gastric cancer](https://onco.cc/cancers/gastric-cldn18-2-positive/), [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/)
- drugs: [Zolbetuximab](https://onco.cc/drugs/zolbetuximab/)
- terms: [Immunohistochemistry (IHC)](https://onco.cc/terms/ihc/)
- targets: [Claudin 18.2](https://onco.cc/targets/cldn18-2/)

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JSON: https://onco.cc/api/v1/entities/cldn18-2-expression.json