7561 Background: CD38 is a type II transmembrane glycoprotein expressed on normal lymphoid and myeloid cells and can be highly expressed in hematologic malignancies. An IHC prototype assay was developed to detect CD38 expression in formalin-fixed, paraffin-embedded (FFPE) tissue specimens from three relapsed or refractory non-Hodgkin’s lymphoma (NHL) subtypes: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL) and mantle cell lymphoma (MCL) for selection of patients for treatment with daratumumab in a Phase 2 clinical trial (NCT02413489). Methods: This assay is based on EnVision FLEX IHC technology using CD38, clone DAK-CD38, primary antibody that has been developed and manufactured by Agilent Technologies. The assay staining protocol was developed for Dako PT Link and Autostainer Link 48. Specificity of DAK-CD38 staining was demonstrated by Western blot analysis of cancer cell lysates, as well as IHC on both normal and cancer tissue. Assay precision and robustness were evaluated using commercially procured FFPE DLBCL, FL and MCL specimens. Results: CD38 IHC DAK-CD38 detected a broad range of CD38 expression in DLBCL, FL, and MCL specimens. FFPE specimens derived from cancer cell lines exhibited a range of IHC staining intensity and confirmed the reported expression of CD38 in the scientific literature. All precision and robustness results met acceptance criteria for both IHC intensity and percent positive cells staining. Conclusions: Our studies demonstrate that the Dako CD38 IHC DAK-CD38 assay is sensitive, specific, precise, and robust for the detection of CD38 expression in DLBCL, FL and MCL. This assay may also have the potential to be used for the detection of CD38 in additional tumor types.

e14588 Background: The PD-L1 IHC 28-8 pharmDx assay has been developed for use in detection of PD-L1 protein in formalin-fixed, paraffin-embedded (FFPE) non-squamous NSCLC and melanoma tissues for associated treatment effect with nivolumab. Validation of the assay for measuring PD-L1 expression level in human squamous cell carcinoma of the head and neck (SCCHN) FFPE sections has been conducted and results are described. Methods: Visualization of the PD-L1 IHC 28-8 pharmDx assay is based on the EnVision FLEX IHC technology. As described in the Instructions For Use, antigen retrieval was performed using the Dako PT Link, and the automated staining was conducted with Autostainer Link 48. The assay performance was validated on commercially procured FFPE SCCHN specimens. Results: Assessment of assay sensitivity to PD-L1 expression was measured on 236 unique specimens originating from squamous cell carcinoma of the tongue, tonsil, nasopharynx, oropharynx, hypopharynx, and larynx. The study demonstrated PD-L1 positive staining across a range of 0-95% positive tumor cells and 0 to 3+ staining intensity. Among these tested specimens, 44% of specimens had PD-L1 expression levels ≥1%. Assay robustness was validated by assessing critical parameters such as target retrieval solution pH, target retrieval solution temperature, target retrieval time, and cut section thickness. Assay reproducibility was evaluated in a study at three external sites. Reproducibility of intra-site, inter-day, and inter-site agreement was assessed in addition to inter- and intra-observer agreement. Assay robustness and reproducibility demonstrated agreement estimates above 85% with values for lower bound 95% confidence intervals calculated above 85%. Conclusions: These studies demonstrate that the PD-L1 IHC 28-8 pharmDx assay is reproducible and robust when used for automated detection of PD-L1 protein in FFPE human SCCHN specimens using Autostainer Link 48.