PD-L1 IHC 22C3 pharmDx

Overview

PD-L1 IHC 22C3 pharmDx (Agilent/Dako) is an FDA-approved companion diagnostic immunohistochemistry assay using the 22C3 monoclonal antibody to detect PD-L1 protein expression in formalin-fixed paraffin-embedded tumor tissue. Results are reported as a Combined Positive Score (CPS) — the number of PD-L1-staining cells (tumor cells, lymphocytes, macrophages) divided by the total number of viable tumor cells, multiplied by 100. CPS thresholds (e.g., ≥1, ≥10, ≥20) are used as biomarkers for anti-PD-1/PD-L1 therapy eligibility across multiple indications including HNSCC, gastric/GEJ, cervical, urothelial, and other cancers.

Used by

  • PMID:38780927 — central PD-L1 IHC 22C3 pharmDx performed on tumor tissue from 51 evaluable patients with recurrent/second primary HNSCC enrolled on NCT03521570; CPS <20 vs. ≥20 showed no significant correlation with 1-year PFS (68.8% vs. 59.2%, P = .86) or OS (94.4% vs. 84.3%, P = .74), in contrast to its predictive utility in recurrent/metastatic HNSCC with single-agent PD-1 inhibition PMID:38780927.
  • PD-L1 IHC 22C3 TPS slides digitized and used as a texture-feature input to the DyAM multimodal model; PD-L1 TPS alone achieved AUC = 0.73, while IHC-G (automated texture) achieved AUC = 0.62 in the pathology validation cohort (n=52) PMID:36038778
  • PD-L1 expression measured by IHC using clone 22C3 (Merck) on 30/34 NSCLC patients treated with pembrolizumab; among PD-L1–expressing tumors with high mutation burden (>200 nonsynonymous mutations), DCB was 91% (10/11), demonstrating mutation burden and PD-L1 IHC capture complementary biomarker information PMID:25765070

Notes

  • PD-L1 CPS by 22C3 did not stratify benefit in the reirradiation + nivolumab context, suggesting that the predictive value of this biomarker may be attenuated when PD-1 blockade is combined with reirradiation in previously irradiated fields PMID:38780927.
  • Corpus-grown slug; not present in canonical ontology.

Sources

This page was processed by crosslinker on 2026-05-14. - PMID:36038778

This page was processed by crosslinker on 2026-05-14. - PMID:25765070

This page was processed by crosslinker on 2026-05-14.