tried technology that has already produced various FDA-approved medicines, attesting to its viability and safety. Since its inception, PEGylation has mostly been utilized to control the life cycles of already-existing therapeutic proteins. Since every protein is unique, each PEG moiety must be tailored individually to the desired therapeutic molecule. The impact on pharmacokinetic and pharmacody­namic qualities depends heavily on the length and form of each PEG moiety. In addition, homogeneity and pyrogenicity requirements for pegylated drugs must be met, and activation and binding methods must be repeatable. Notwithstanding these difculties, methods for PEGylating proteins and peptides have greatly improved recently. In the near future, we may anticipate and sincerely hope that the numerous studies conducted by academic and commercial researchers will successfully address the issues with PEG-small drug conjugates, allowing the introduction of these novel products to the market as well.