CLDN18.2 TEST RESULTS
CLDN18.2 40% vs 75%: why the percentage matters
A pathology report summarized as negative or below threshold can still describe a CLDN18.2 result relevant to satri-cel. Two different treatments use two different staining thresholds, and the exact percentage is what matters.
Two Different Thresholds
VYLOY (zolbetuximab) companion-diagnostic selection uses moderate-to-strong membranous CLDN18 staining in at least 75% of viable tumor cells. The satri-cel pivotal study used a lower threshold: CLDN18.2 IHC intensity of 2+ or higher in at least 40% of tumor cells.
Why Negative for One Test Is Not Negative for Both
A report described as below the VYLOY threshold, or informally called negative, does not by itself establish whether the tumor is below satri-cel’s lower 40% threshold. A case reported as 40 to 74% CLDN18.2-positive can fall below the VYLOY cutoff while still meeting the satri-cel pivotal threshold.
What to Ask For From the Original Report
Ask the reporting pathology lab for the original percentage and staining intensity, not a binary positive or negative summary. Vialen’s intake asks for the exact percentage and intensity when available so a case is not screened out on shorthand alone.
Not Tested Yet?
Real-world CLDN18 testing penetration in advanced gastric and GEJ cancer remains incomplete. If CLDN18.2 has not been tested, the relevant next step is usually pathology testing through the patient’s normal clinical care. Whether to re-test existing tissue is a physician and pathology decision, and is never promised automatically.