# VENTANA CLDN18 (43-14A) RxDx Assay

Source: https://onco.cc/drugs/ventana-cldn18-43-14a/  
OnCo record `ventana-cldn18-43-14a` (Test). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The stain that decides whether stomach or junction cancer is claudin 18.2-positive and so eligible for zolbetuximab.

## Summary

Ventana Medical Systems' (Roche Tissue Diagnostics) CLDN18 (43-14A) RxDx Assay was approved on 18 October 2024 (PMA P230018) as the companion diagnostic for zolbetuximab in gastric or gastro-oesophageal junction adenocarcinoma.

## Fields

- Kind: Test
- Status: approved
- Last checked: 2026-11-03
- Tags: test
- Brand: VENTANA CLDN18 (43-14A) RxDx Assay
- Modality: Immunohistochemistry companion diagnostic assay (claudin 18 protein, gastric tumour tissue)
- Mechanism: Immunohistochemistry with the 43-14A antibody; the FDA list defines a positive result as claudin 18 staining in at least 75% of viable tumour cells.
- Approvals: US 2024: Companion diagnostic for zolbetuximab in gastric or GEJ adenocarcinoma (claudin 18 in at least 75% of viable tumour cells)

## Sources

- FDA PMA P230018: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?id=P230018
- FDA: List of cleared or approved companion diagnostic devices: https://www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools

## Connected records

- biomarkers: [Claudin 18.2 expression (>= 75% of tumour cells, moderate to strong)](https://onco.cc/biomarkers/cldn18-2-expression/)
- cancers: [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/)
- technologies: [Companion diagnostics](https://onco.cc/technologies/companion-diagnostic/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- targets: [Claudin 18.2](https://onco.cc/targets/cldn18-2/)
- drugs: [Zolbetuximab](https://onco.cc/drugs/zolbetuximab/)
- companies: [Roche / Genentech](https://onco.cc/companies/roche-genentech/)
- terms: [Companion diagnostic](https://onco.cc/terms/companion-diagnostic-term/), [Immunohistochemistry (IHC)](https://onco.cc/terms/ihc/)

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