title: Stability Enhancing N-Terminal PEGylation of Oxytocin Exploiting Different Polymer Architectures and Conjugation Approaches.
abstract: Oxytocin, a cyclic nine amino acid neurohypophyseal hormone therapeutic, is effectively used in the control of postpartum hemorrhaging (PPH) and is on the WHO List of Essential Medicines. However, oxytocin has limited shelf life stability in aqueous solutions, particularly at temperatures in excess of 25 °C and injectable aqueous oxytocin formulations require refrigeration (<8 °C). This is particularly problematic in the hot climates often found in many developing countries where daytime temperatures can exceed 40 °C and where reliable cold-chain storage is not always achievable. The purpose of this study was to develop N-terminal amine targeted PEGylation strategies utilizing both linear PEG and polyPEG "comb" polymers as an effective method for stabilizing solution formulations of this peptide for prolonged storage in the absence of efficient cold-chain storage. The conjugation chemistries investigated herein include irreversible amine targeted conjugation methods utilizing NHS ester and aldehyde reductive amination chemistry. Additionally, one reversible conjugation method using a Schiff base approach was explored to allow for the release of the native peptide, thus, ensuring that biological activity remains unaffected. The reversibility of this approach was investigated for the different polymer architectures, alongside a nonpolymer oxytocin analogue to monitor how pH can tune native peptide release. Elevated temperature degradation studies of the polymer conjugates were evaluated to assess the stability of the PEGylated analogues in comparison to the native peptide in aqueous formulations to mimic storage conditions in developing nations and regions where storage under appropriate conditions is challenging.
authors.affiliation: Department of Chemistry, University of Warwick , CV4 7AL, Coventry, United Kingdom.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Collins
authors.affiliation: Department of Chemistry, University of Warwick , CV4 7AL, Coventry, United Kingdom.|ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: Kristian
authors.initials: K
authors.lastname: Kempe
authors.affiliation: Department of Chemistry, University of Warwick , CV4 7AL, Coventry, United Kingdom.|ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Wilson
authors.affiliation: Department of Chemistry, University of Warwick , CV4 7AL, Coventry, United Kingdom.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Blindauer
authors.affiliation: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: Michelle P
authors.initials: MP
authors.lastname: McIntosh
authors.affiliation: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Davis
authors.affiliation: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Whittaker
authors.affiliation: Department of Chemistry, University of Warwick , CV4 7AL, Coventry, United Kingdom.|ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Haddleton
mesh_terms: D006801:Humans; D010121:Oxytocin / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D055550:Protein Stability; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D011108:Polymers; D014867:Water; D011092:Polyethylene Glycols; D010121:Oxytocin