Abstract 3755: Impact of antigen retrieval and other parameters on detection of FGFR2b in various solid tumors on a BenchMark ULTRA automated staining platform: Development of a new IHC assay for FGFR2b

Abstract Background: Fibroblast growth factor receptor 2b (FGFR2b) is part of the FGFR transmembrane tyrosine kinase receptor family. This protein has gained more attention in recent years as a tumor progression biomarker in numerous solid tumors. The detection of FGFR2b by immunohistochemistry (IHC) has been used recently in immunotherapy clinical trials with multiple tumor types. During IHC assay development on formalin-fixed paraffin embedded tissue, a thorough study of antigen retrieval through cell conditioning or enzyme incubation, primary antibody incubation, and detection parameters is critical to evaluate staining performance. Design: A study of an investigational anti-FGFR2b (FPR2-D) assay developed on a BenchMark ULTRA automated staining platform explored the effect of antigen retrieval and detection parameters on staining performance. VENTANA System Software was used to modify steps in the IHC staining protocol resulting in 42 permutations. Ten different solid tumors were stained with these modifications to the assay and subsequently evaluated for FGFR2b expression. Result: s The results demonstrate that the staining clarity, intensity, and dynamic range within tissue cases of FGFR2b staining can vary widely between different solid tumor types. While most permutations of the initial assay parameters had minimal impact on the staining performance and readability by a pathologist, the order of the enzyme treatment and the cell conditioning steps (in addition to increased incubation time of primary antibody) had a significant impact when comparing across different solid tumors. Detection of FGFR2b seemed to have a greater susceptibility by tumor type to the antigen retrieval process than has traditionally been observed in other biomarkers. Conclusion: The overall results of this investigation show the importance of an extensive parameter screening approach when evaluating new antibody targets and indication combinations in IHC to ensure optimal staining performance. This is critical to downstream testing and the potential use of new assays in the context of in vitro diagnostics. Citation Format: Autumn Sky Watson, Catherine Le, Anne M. Wertheimer, Spencer Escobedo, Lisa So, Bhavani Bagevalu Siddegowda, John D. Palting, Susan Marion, Steven P. Stratton, Birte Aggeler. Impact of antigen retrieval and other parameters on detection of FGFR2b in various solid tumors on a BenchMark ULTRA automated staining platform: Development of a new IHC assay for FGFR2b abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3755.