Development of the Prototype Immunohistochemistry Assay that Advanced Development of Pembrolizumab

Our prototype assay’s expert development resulted in an assay with wide dynamic range, high precision and reproducible results, laying the foundation for the successful 22C3 PD-L1 companion diagnostic assay widely utilized today to select patients eligible for treatment with the anti-PD-1 immunotherapy pembrolizumab.


The programmed death receptor-1 (PD-1) pathway is one of the major immune-checkpoints that engages with tumor cells to avoid T-cell–mediated immune surveillance. The PD-1 receptor-1 ligand (PD-L1), which is often expressed by tumor cells, binds with PD-1 on T cells and delivers an inhibitor signal to down-regulate T cell proliferation and activation – enabling tumor expansion and growth.

Given its role in tumor progression, the PD-1 pathway is a common target for immunotherapies. The first clinical trial of a PD-L1-blocking drug began in 2006 in patients with a variety of tumors including melanoma, kidney, and lung. Today, six PD-1/L1 checkpoint inhibitor immunotherapies have been approved by the U.S. Food and Drug Administration for 14 different types of cancer, and PD-1/L1 inhibitors are being evaluated in more than 2,250 clinical trials.

Download the Full Poster

To gain access to the FREE poster, please fill out the form below.