Validation of an immunohistochemical assay, CEACAM5 IHC 769, under development for use with the antibody-drug conjugate tusamitamab ravtansine (SAR408701).

e21030 Background: Despite recent advances in non-small cell lung cancer (NSCLC) treatment, a need remains for treatment options at disease progression. Tusamitamab ravtansine (SAR408701) is an antibody-drug conjugate of a humanized CEACAM5-specific monoclonal antibody linked to the maytansinoid DM4, a potent anti-tubulin agent. In a Phase 1/2 study, tusamitamab ravtansine showed promising antitumor activity in pretreated advanced non-squamous NSCLC (NSQ NSCLC) patients with high CEACAM5 expression, defined as ≥ 50% of the tumor cells per specimen with CEACAM5 positive staining at ≥ 2+ intensity (Gazzah A et al. J Clin Oncol 2020;38[15]: 9505). Sanofi and Agilent have partnered to develop an immunohistochemical (IHC) assay, CEACAM5 IHC 769, for detection of CEACAM5 protein in formalin-fixed paraffin-embedded (FFPE) NSQ NSCLC tissue using the EnVision FLEX visualization system on Dako Omnis. This assay is in development for the assessment of patients for whom tusamitamab ravtansine is being considered. Methods: CEACAM5 IHC 769 is a qualitative IHC assay using mouse monoclonal anti-CEACAM5 clone 769. Murine anti-CEACAM5 clone 769 is based on tusamitamab ravtansine, with the same specificity as the drug for CEACAM5. The clone was developed by Sanofi and used to evaluate CEACAM5 expression in a Phase 1/2 trial. The CEACAM5 IHC 769 scoring algorithm defines positive staining as any partial or complete tumor cell plasma membrane staining at ≥ 2+ intensity. Membrane staining may be linear or punctate. Staining may appear as complete or partial staining involving the basal, lateral, or basolateral aspects of the membrane, or as apical staining of the luminal aspect of the cell. CEACAM5 IHC 769 is being validated by Agilent Technologies for NSQ NSCLC at the cutoff of ≥ 50% at ≥ 2+ intensity. Internal studies included sensitivity, specificity, intra-block heterogeneity, observer precision, laboratory repeatability/precision, and robustness. Results: Sensitivity studies demonstrated detection across a dynamic range of CEACAM5 expression. Specificity studies indicated that the antibody is specific for CEACAM5. An intra-block heterogeneity study showed good overall diagnostic agreement for sections from the same tumor (point estimate ≥ 85%). Inter- and intra-observer precision, laboratory repeatability/precision, and robustness validation studies met acceptance criteria; the lower bound of the two-sided 95% confidence interval was ≥ 85% for positive, negative, and overall percent agreement. Conclusions: Internal validation studies demonstrated that CEACAM5 IHC 769 is sensitive, specific, precise, reproducible and robust in evaluating CEACAM5 expression in NSQ NSCLC tissue at the cutoff of ≥ 50% at ≥ 2+ intensity. CEACAM5 IHC 769 is being used for patient selection/stratification in ongoing Phase 2 and 3 clinical trials of tusamitamab ravtansine.

Photostable AIE Probes for Wash-Free, Ultrafast, and High-Quality Plasma Membrane Staining

Plasma membrane (PM), a fundamental building component for a cell, is responsible for a variety of cell functions and biological processes. However, it is still challenging to acquire its morphology...

PD-L1 Expression in Sarcomas: An Immunohistochemical Study

Introduction/Objective Immunotherapy is increasingly used for the treatment of metastatic melanoma and carcinomas. PD-I (programmed death 1) and its associated ligand (PD-L1) inhibits the activation of T lymphocytes. This inhibition can be impacted by a number of drugs. Response to these drugs is predicted by assessment of PD-L1 expression. PD-L1 expression varies between 19% and 92% in melanomas and carcinomas. PD-L1 expression is less well documented for sarcomas. Methods Fifty-one sarcomas of various histopathologic types were immunohistochemically stained (IHC) for PD-L1 using the antibody clone SP263 (Ventana, Tuscan, AZ). Membrane staining of tumor cells was quantitated as a percentage of total tumor cells. Sarcomas were judged as non-expressors (less than 1%) low-expressors (1 to 50%) and high expressors (greater than 50%). The percentage of each type of sarcoma judged as an expressor was determined. Results The percentage of each type of sarcoma expressing PD-L1 is reported and 20% of sarcomas expressed PD- L1. The percentage of sarcomas expressing PD-L1 varied significantly between types but the majority of sarcomas were non-expressors. Conclusion PD-L1 IHC expression is valuable in predicting response to immune-modulating drugs. Such therapies may be useful for treatment of metastatic sarcomas. Expression of PD-L1 in carcinomas and melanomas is variable ranging from 19% to 92%. In our study, a minority (20%) of sarcomas expressed PD-L1. Other studies have shown similar results with between 1.4 and 59% (average 24%) of sarcomas expressing PD-L1. Expression appears to be type specific. These finding suggest that PD-L1 based therapy may be less useful in sarcomas than in other malignancies.

When the strategies for cellular selectivity fail. Challenges and surprises in the design and application of fluorescent benzothiadiazole derivatives for mitochondrial staining

Design, synthesis, molecular architecture and the unexpected behavior of fluorescent benzothiadiazole for selective mitochondrial and plasma membrane staining are investigated.