This ELISA kit provides quantitative measurement of Cathepsin B, a lysosomal cysteine protease released as a CHO host cell protein impurity. Its high sensitivity supports detection of trace Cathepsin B in culture fluids and downstream purification samples, helping safeguard product stability and quality. The kit includes a pre‑coated microplate, standards, conjugate, and optimized buffers for reliable, plate‑based quantification. E‑65CTB is ideal for bioprocess monitoring, impurity clearance studies, and regulatory‑driven HCP characterization involving proteases with potential to degrade therapeutic proteins.