Optimizing Pharmacological and Immunological Properties of Therapeutic Proteins Through PEGylation: Investigating Key Parameters and Their Impact

João Gonçalves,1 Paolo Caliceti2 1Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal; 2Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, ItalyCorrespondence: João Gonçalves, iMed – Research Institute for Medicines, Faculdade de Farmácia da Universidade de Lisboa, Av. Prof. Gama Pinto, Lisbon, Portugal, Tel +351-217946486, Email [email protected]: Protein PEGylation represents a significant technological advancement in the development of protein-based therapeutics and is widely used to reduce immunogenicity, enhance pharmacokinetics, and/or improve stability. The improved pharmacokinetic profile of PEGylated proteins compared with the native protein results in sustained versus fluctuating plasma concentrations and carries the potential of less frequent administration. However, attachment of PEG to therapeutic proteins can alter their structural conformation, which exposes new epitopes to the immune system. The design of PEGylated proteins thus needs to balance the intended benefits with the potential risks associated with the immunogenicity of the PEG moiety itself or resulting from alterations in the conformation of the therapeutic protein. In recent years, advancements in protein PEGylation chemistry have offered the capability to target PEG attachment to specific amino acids to create more stable and bioactive therapies. The biophysical and biopharmaceutical features of PEGylated proteins can vary based on polymer size, shape, density, and conjugation site, and the immunogenicity of the conjugate can be further impacted by the properties of the therapeutic protein itself and the characteristics of the patient. It is important to note that not all patients will develop an immune response toward the PEG moiety, and not all immune responses are clinically meaningful. A comprehensive understanding of the factors that influence immunogenic responses to PEGylated proteins is important to optimize their therapeutic benefits. This article reviews the design and optimization of PEGylation strategies to enhance the clinical performance of protein-based therapeutics while minimizing immunogenic responses to the PEG moiety or PEGylated proteins. Keywords: PEGylation, protein-based therapeutics, immunogenic response