This book focuses on the development of stapled peptides, a novel molecular modality used to regulate aberrant intracellular protein-protein interactions (PPIs). The author designs and presents a novel helical peptide stabilization methodology by constructing a chiral cross-linker moiety, namely "chiral center induced peptide helicity (CIH)". The book demonstrates that a precisely positioned carbon chiral center on tether can decisively determine the secondary structure of a peptide, and that the R-configured peptide is helical, while the S-configured peptide is non-helical. Further, it reports that helicity-enhanced R isomer peptides displayed significantly enhanced cell permeability and target binding affinity, as well as tumor inhibition efficiency, in comparison to S isomer peptides. The book will not only advance readers' understanding of the basic principle of stapled peptides, but also accelerate the clinical transformation of stapled peptide drugs. .