Preservative-Induced Aggregation of Glucagon-Like Peptide-1 Receptor Agonists

• Gavin Brownstein, Chemical Engineering, University of Delaware

• Norman Wagner, Chemical and Biomolecular Engineering, University of Delaware

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a class of incretin mimetics used in the treatment of type 2 diabetes and obesity. Although pharmaceutical products must be formulated to inhibit aggregate and microbial growth, the stability of pharmaceutical formulations of these peptides is impeded by antimicrobial agents and other excipient molecules in solution. Common preservatives destabilize GLP-1RAs and promote the formation of aggregates. Large aggregates from preservative-induced aggregation may compromise drug efficacy or safety during injection. This research focuses on the peptides semaglutide (SMG) and liraglutide (LRG) with preservatives phenol and benzyl alcohol. The purpose of this study was to catalog the limits of stable oligomer peptide conformation across varying formulations and temperatures. Turbidity and stability measurements were performed using static multiple light scattering (SMLS) and aggregate sizes were conducted using dynamic light scattering (DLS). Samples that contained a higher concentration of phenol aggregated at higher temperatures with no sample below 13 mg/mL phenol showing turbidity at any measured temperature. The addition of benzyl alcohol to samples containing phenol led to turbidity occurring at temperatures higher than samples with phenol alone. Benzyl alcohol also led to an increase in the size of aggregated particles. Light transmission through samples due to changes in temperature was monitored and appreciably decreased in a matter of minutes for samples where aggregates were present.  Phase separation and sedimentation occurred in samples with high phenol concentration at extended time scales. Samples that were turbid and sedimented demonstrated a recovery of clarity when acclimated back to temperatures above their stability limit. This recovery suggests reversible aggregation, indicative of a thermodynamic phase separation.