Bio-Rad Laboratories introduces a range of antibodies that are specific to cemiplimab (Libtayo) and inhibit the binding of the drug to its target, human programmed death receptor-1 (PD-1). These ready-made antibodies are suitable for developing selective and sensitive assays for bioanalysis and drug monitoring of cemiplimab, which acts as a checkpoint inhibitor by binding to PD-1 on T cells and blocking the interaction with its ligands, PD-L1 and PD-L2, thereby activating T cells to attack cancer cells. The new range of anti-cemiplimab antibodies offers flexibility for bioanalytical ligand binding assays. The recombinant antibodies are generated using the Human Combinatorial Antibody Libraries (HuCAL) and CysDisplay, a proprietary method of phage display, along with guided selection methods to obtain highly targeted reagents. The recombinant production method aims to deliver batch-to-batch consistency, ensuring reproducible results and a secure supply throughout the assay lifecycle.