IHC Assay That Advanced Development Of Pembrolizumab

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 ability to reliably and simply measure PD-L1 expression in tumor tissue may identify subsets of patients who might achieve better outcomes with anti–PD-1 or anti–PD-L1 therapeutics. QualTek experts (now part of Discovery Life Sciences) collaborated with experts from Merck Research Laboratories to develop a prototype immunohistochemistry (IHC) assay for measuring PD-L1 expression among patients enrolled in Merck-sponsored clinical trials to predict those who have a higher likelihood of responding to Merck’s immune checkpoint inhibitor, 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.