CTSB and neoplasm: This work investigatesthe enzymatic susceptibility, cleavage kinetics, and metabolic stabilityof the peptide sequence Gly–Pro–Leu–Gly (GPLG)as a novel Cathepsin B-cleavable linker for tumor-targeting drug conjugates.Compared to GFLG, VCit, and VA, all conjugated to paclitaxel via aPABC-N,N′-dimethylethylenediaminespacer, GPLG exhibited the fastest Cathepsin B cleavage within thefirst 30 min of the assay, and higher stability at pH 5.4 and in bothhuman and rat plasma samples.