Claudin 18 IHC

Formalin fixed paraffin-embedded (FFPE) tissue block or slides

One paraffin block or five air-dried unstained slides sectioned at 4-5 microns, no more than 45 days in age

At least three unstained slides sectioned at 4-5 microns

Paraffin block or unstained positive charged slides

Collect specimen on paraffin block or unstained slides sectioned off no more than 45 days in age. 

The recommended fixative is 10% neutral buffered formalin for 24 hours with a range from six to 48 hours fixation time. Slides should be cut at 3-5 micron thickness and mounted onto positively charged slides. It is recommended that slides are stained shortly after slide preparation, as antigenicity of cut tissue sections may diminish.

Tumor types other than gastric/gastro-esophageal adenocarcinoma; improper fixation; freezing; thawing; washing; heating; sectioning or contamination with other tissue; slides sectioned greater than 45 days prior to test request

This assay is indicated as an aid in identifying patients with gastric or gastro-esophageal junction (GEJ) adenocarcinoma who may be eligible for treatment with VYLOY™ (zolbetuximab) in accordance with the approved therapeutic product labeling.

Decalcification and improper fixation may negatively affect results.

Immunohistochemistry

Shitara K, Lordick F, Bang YJ, et al. Zobetuzimab plus mFOLFOX6 in patients with claudin-18 isoform 2 positive, HER2-negative, untreated, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma (SPOTLIGHT): a multicentre, radomised, double-blind, phase 3 trial. Lancet. 2023 May 20;401(10389):1655-1668. PubMed 37068504

VENTANA CLDN18 (43-14A) RxDXAssay [package insert]. Ventana Medical Systems, Inc. Tucson, AZ; 2024.