Novel compounds are provided that bind to polo-like kinases through the polo -box domain. In certain embodiments, the novel compounds are PEGylated peptides. The PEGylated peptides in accordance with the invention demonstrate high PBD-binding affinity. In certain embodiments, the PEGylated peptides have also achieved activities in whole cell systems. The invention also provides compounds that bind polo- like kinases through the polo -box domain and possess reduced anionic charge. Further provided are methods of design and/or synthesis of the PEGylated peptides and methods of use thereof. The invention provides methods of use of the compounds and methods of synthesis of the compounds. The compounds of the invention have potential therapeutic activity in view of their binding and inhibitory activities towards Plkl. They are based on the amino acid sequence PLHSpT (phosphorylated Thr). The PEG moiety, when present, is covalently attached at the N- terminus. The invention also encompasses derivatives having substituents on the Pro and/or the His side chains, substituents on the phosphate group, the replacement of His with Gln, the replacement of Pro with a N-substituted Gly, the replacement of Ser with Ala, as well as HS-pT fragments with N-terminal alkoxycarbonyl group and PLHS fragments with a C-terminal glyco-imino-alkylxyalkylamide group.
