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The 22C3 pharmDx assay is the PD-L1 stain tied to pembrolizumab since 2015 and the source of the combined positive score (CPS). The cut-off differs by cancer: 1% of tumour cells in lung cancer, CPS 1 in gastric, cervical and head and neck cancer, CPS 10 in oesophageal and triple-negative breast cancer, so one stain is read differently per disease.
Approved 2 October 2015 (PMA P150013, Dako, now Agilent) as the companion diagnostic for pembrolizumab in non-small-cell lung cancer, initially at TPS ≥50% and from 2016 at TPS ≥1%. It has since been approved for gastric and gastro-oesophageal junction cancer (CPS ≥1, 2017), cervical cancer (CPS ≥1, 2018), head and neck squamous cell carcinoma (CPS ≥1, 2019), oesophageal squamous cell carcinoma (CPS ≥10, 2019) and triple-negative breast cancer (CPS ≥10, 2020, KEYNOTE-355). The many cut-offs are a source of confusion for patients: the same stain is read differently depending on the cancer and the trial that set the threshold.
Mouse monoclonal antibody 22C3 on the Dako Autostainer Link 48, reported as tumour proportion score (TPS) in lung cancer or combined positive score (CPS, tumour plus immune cells relative to tumour cells) in other cancers. Connects to PD-L1.
1.PD-L1 IHC 22C3 pharmDx slips into a pocket on PD-L1.
| Region | Year | Indication |
|---|---|---|
| US | 2015 | Companion diagnostic for pembrolizumab in NSCLC (TPS) |
| US | 2017 | Gastric / GEJ adenocarcinoma, CPS ≥1 |
| US | 2019 | Head and neck squamous cell carcinoma (CPS ≥1) and oesophageal squamous cell carcinoma (CPS ≥10) |
| US | 2020 | Triple-negative breast cancer, CPS ≥10 (pembrolizumab plus chemotherapy) |
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This is the population-based prevalence for the two label thresholds in early TNBC, and it shows the KEYNOTE-355 CPS 10 gate would admit only about a quarter of unselected patients.
The clearest demonstration that PD-L1 positive in triple-negative breast cancer means different things depending on the kit; with atezolizumab withdrawn, pembrolizumab's 22C3 combined positive score of 10 is the surviving standard, and roughly a quarter of patients get a different answer depending on which assay their laboratory runs.
This is the paper Europe PMC returns for registry id NCT02819518 with the most citations, so it is the natural first reading for anyone following the KEYNOTE-355 trial. Read the abstract above alongside the trial page and the registry entry; the record was linked automatically and its figures have not been checked by hand.
Query for this drug: (TITLE:"PD-L1 IHC 22C3 pharmDx" OR ABSTRACT:"PD-L1 IHC 22C3 pharmDx") AND (cancer OR tumor OR tumour OR oncology OR carcinoma OR lymphoma OR leukemia OR leukaemia OR myeloma OR sarcoma OR melanoma OR glioma). Results are unfiltered search hits about PD-L1 IHC 22C3 pharmDx, not a curated reading list.
Shares VENTANA PD-L1 (SP142) Assay, PD-L1 TPS (tumour proportion score), PD-L1 Immunohistochemistry Assay Comparison in Atezolizumab Plus nab-Paclitaxel-Treated Advanced Triple-Negative Breast Cancer, PD-L1 expression testing (22C3, SP142, SP263) and the tag test.
Shares Agilent Technologies (Dako), Companion diagnostics, Non-small-cell lung cancer and the tag test.
Shares Agilent Technologies (Dako), Diagnostics roadmap: stains → gene panels → blood tests that decide treatment, Companion diagnostics, Immunohistochemistry (IHC) and the tag test.
Shares Diagnostics roadmap: stains → gene panels → blood tests that decide treatment, Head and neck squamous cell carcinoma, Triple-negative breast cancer (TNBC), Non-small-cell lung cancer and the tag test.
Shares Diagnostics roadmap: stains → gene panels → blood tests that decide treatment, Companion diagnostics, Triple-negative breast cancer (TNBC) and the tag test.
Shares Diagnostics roadmap: stains → gene panels → blood tests that decide treatment, Companion diagnostics, Triple-negative breast cancer (TNBC) and the tag test.
Shares Diagnostics roadmap: stains → gene panels → blood tests that decide treatment, Companion diagnostics, Non-small-cell lung cancer and the tag test.
Shares Companion diagnostics, Histopathology & immunohistochemistry, Triple-negative breast cancer (TNBC), Pembrolizumab and the tag test.